Do you think you need a subwoofer?

Dear Dgob: Nice to read that you are really satisfied too.

Regards and enjoy the music.
Raul.

Dear Jim: Other factor that could help to that Legacy speakers is to separate the subs from the main box.
Anyway it looks like a very good speaker.

regards and enjoy the music.
Raul.

Hi Doug: Do you think you need subwoofers? what is your opinion about?

Regards and enjoy the music.
Raul.

Dear Sirspeedy: I love you man ! and that's why ( I take my time for this. ) I give you next some high-lights that different people ( including me ) posted on this thread on the subject ( two subwoofers/IMD/HD ):

this one was an answer to what you posted:

Dear Sirspeedy: +++++ " if the main speakers can support a certain low frequency,before rolling off,it will be best to bring in the sub at just under this point. " +++++

Well this is one approach that mainly goes to have a lower bass response: it is the REL approach and other subwoofer manufacturers but not all of them.

My approach is different from yours, mine goes to obtain ( first place ) a better quality performance in my main speakers and in second place to achieve a better quality bass performance that could goes lower too.
I use two subwoofers in true stereo way to achieve those targets, the first one ( that you can't achieve with your approach. ) is obtained lowering the Intermodulation Distortion ( main speakers ), this means to stop to ask to the woofers ( main speakers ) the simultaneous reproduction of frequencies between 20Hz and 200HZ or higher( if yours goes flat to 30Hz then you still have some distorted response at 20Hz that makes higher the IMD subject/problem ), this means ( again ) that we have to choose a crossover frequency higher than what the main woofers are handled : in my case 60 Hz and in Eldartford 80Hz.
In this manner the main woofers will be free/less stressed of the low bass reproduction working from 60Hz-80Hz up and lowering ( cleaning in deep ) the IMD: this fact makes a huge improvement ( in any speaker including yours ) in the quality sound reproduction of the main speakers ( it is not matters what you think about or what I think about, lowering the IMD always improves the quality performance of " that " driver, physics laws. ).
The second advantage on this approach is that now the low bass frequency response not only goes down through the subwoofers but with a better quality bass performance due that those bass frequencies will be reproduced for " drivers /amplifiers " that were designed specific for those kind of bass frequencies. " +++++

+++++ " Where the subs can help us ? :

Intermodulation Distortions ( harmonic distortions ): Almost any three ways speaker ( all two ways/one way ) has it's crossover frecuency ( low driver ) between 150Hz and 450Hz. I can assume that any of ours speakers system goes down flat ( at least ) between 60Hz to 20Hz.

What does that means ?, well that a single driver has to reproduce frecuencies/harmonics from 20Hz/60Hz to 150Hz/450Hz. With that kind of frecuency range here exist a great intermodulation distortions that put it's " color " on the sound reproduction.

You have to imagine that that single woofer/driver has to reproduce, at the same " time ", a 30Hz frecuency along a 350Hz frecuency: here is where exist that IM that gives heavy distortions in what we hear ( there is no perfect driver: moving coil, electrostatic, ribbon, etc.. The speaker designers has to choose the best " trade offs ", but the distortions are there. ): less clarity, less resolution, less precision, less natural balance, less pitch, les, less, less......., and this is what we are really hearing: LESS MUSIC.

What happen when that low driver is free from those frecuencies ? ( main speakers: monitors or full range, it does not matters. My main speakers are flat to 22Hz and only 5db +.- at 18Hz and I have benefits with the subwoofers integration to my system ), below 60Hz ( this is the crossover frecuency that we find the best point to start to blend a subwoofer. Mines are at around this 60Hz frecuency: 78Hz,yours ( I think ) will be around that frecuency. ):

SUDDENLY the " lights are on ", your music/audio " life " its born: the mid bass is clean, the midrange is clean, the highs are clean: high resolution every where ( the distortions are almost gone ), and now you can really hear for the first time the MUSIC through your home stereo audio system: what a pleasure!!!!!. " +++++

Mark the second subwoofer is not to obtain more bass but to even and smooth the room bass response:

08-02-05: Skushino
After adding a second sub to my system, there was smoother bass response. Again, this isn't about louder or stronger bass, in fact, I was seeking lower, smoother bass. Ironic that the path to this goal was accomplished by adding a sub! My girlfriend is a great listener and concurred that bass was better quality. Since I returned the second sub (on loan from my neighbor), I miss the performance " +++++

this quote comes from a in deep research made by Harman International Group:

+++++ " Using very large numbers of subwoofers would result in
cancellation of room modes. For practical numbers of
subwoofers, there appears to be no obvious correlation.

Two subwoofers, at opposing
wall midpoints, performs very nearly as well as four at the
midpoints and gives a much better LF factor

Can a sufficiently large number of
subwoofers cancel out all room
modes?
Theoretically yes

With 5000 subwoofers, modal variation is virtually
eliminated. !!!! " +++++

+++++ " I don't know at which frecuency you are cutting your REL. But, for example, if the crossover is at 27-30Hz and if the low pass filter is of second to fourth order then your REL is reproducing frecuencies as high like 80-100Hz that are interfering with the same frecuency range of your main speakers " +++++

this quote comes from a friend ( Agon ) that send to me for this thread. The research/investigation or whatever were made by: Audio Perfectionist Journal and Vandersteen:

+++++ " Suppose I told you that you could add two
components to your system that would reduce
intermodulation distortion in the midrange by a
factor of two or more, dramatically improve the
resolution of midrange and high frequency detail,
double or triple the dynamic range capability of
your system without changing your existing
amplifier or speakers and improve imaging more
than you can imagine. You would probably be
interested, right? But wait, there’s more.
These same components would allow the
amplifier to maintain tighter control over the
speakers in the mid-bass and lower midrange.
They could extend bass response to infrasonic frequencies
while lowering bass distortion and
improving the system’s ability to accurately convey
the rhythm and pace of music. And these
same components could virtually eliminate the
uneven response at lower frequencies caused by
room standing waves.
Does all that sound too good to be true?
Are you concerned about the possible cost of all
this improvement? If all this is so easily achievable,
are you wondering why you’ve never heard
about it before?
Let me assure you that all these sonic
improvements can be yours and I’ve been conservative
in my estimates of the level of audible
improvement you’ll get.

When properly integrated with the system,
subwoofers blend seamlessly with the main
speakers and don’t make their presence known.
But that’s a very hard sell to the average consumer
and selling is the name of the audio game.
Subwoofers are supposed to add bass, right?
After their initial forays into the market,
few manufacturers continue to try to make subwoofers
that accurately represent music. Why try
to educate consumers when it’s easier to just give
them what they think they want? Boom!
Subwoofer makers soon learned what
dealers had already figured out: if they can’t hear
it woof they won’t buy it. Manufacturers started
to build subwoofers with high-Q alignments and
vents in order to provide more “slam.” Dealers
started to set up their demonstrations for maximum
thump, and maximized sales figures.
Awareness of the basic concepts of specialized
bass reproducers faded or was suppressed.
Home theater exacerbated this situation.
People today expect a subwoofer to rattle their
fillings and the exaggerated bass that most subwoofers
deliver is incompatible with accurate
music reproduction.
But there is more to bass than boom—bass
is the foundation of all music. And there is more
to subwoofers than bass. They reproduce bass frequencies
to be sure, but bass extension is possibly
the least of the sonic benefits offered by good
powered subwoofers.
Why Good Subwoofers Improve Sound
In order to provide the benefits mentioned
at the beginning of this article, subwoofers must
utilize a dedicated bass amplifier, and the main
amplifier and speakers must be high-pass filtered
using a passive, first-order device.
A high-pass filter does just what you
would expect: it allows frequencies above the cutoff
point to pass, and blocks frequencies below
that cut-off point. " +++++

this is another quote on the subject:

+++++ " - There is no single external / stand alone amplifier that can work or do a better job than a low bass dedicated amplifier like the one that comes with a powered subwoofer:

think that this dedicated bass amplifier was designed/tailored to match every single woofer parameter: impedance, frecuency response range, damping, power, distortion, etc, etc,...

- It is not only this dedicated amplifier what makes this subwoofer approach/technology ideal to handle the low bass octaves.
The driver/woofer is designed/tailored too for that specific frecuency range.
There is no passive FRS ( full range speaker ), at any price with any amplifier, that could beat a self powered subwoofers in that frecuency range. When you have and hear the subs on your system you never can live again with out those subwoofers.

Here we have to remember other important issue: the best subwoofers are SERVO CONTROLLED, this characteristic give to the subwoofer a heavy advantage over a FRS about the low distortion that a well designed subwoofer had against a higher distortions on any FRS.

- With a subwoofer we not only gain with a lowest harmonic distortion but with a lowest intermodulation distortion too. This means better quality sound reproduction.

- Other advantage is that with the integration of two subwoofers in a true stereo fashion to a full range speakers system: the main ( s ) amplifier will be free of those high power consumtion low bass frecuency range: this means too, better quality music sound reproduction. No exception.

- Other advantage with the subs integration is that facilitate the integration of our mains speakers to the room.

Do you think that your FRS audio system sounds great? Wait till you do the subwoofers integration: you will be on music heaven !!!!!!!! Nothing less. Try it. " +++++

Please read carefully, I only want ( I would that ) that you understand the whole subject concept, if you want to aplicate or not is a totally different subject.

Regards and enjoy the music.
Raul.

Dear Psychicanimal: Biomimetic give you an answer about and I will try, along this thread, that the use of subs are essential for the analog sound reproduction.

Regards and enjoy the music.
Raul.

Dear Stevecham: +++++ " the soundstage opened up on all recordings. +++++ "

This is a plus when we installed the subs. If we haven't then we are loosing this characteristic.

+++++ " I think the main challenge is to take the time to fine tune the sub so that it is "not heard" and just picks up where your mains leave off. +++++ "

THis is our challenge whe we installed the subs. We ( José and I ) take around six months to settle in right on target.

Dear Steve I never had the opportunity to hear your speakers/subs combination but I'm sure they give you a lot of musical pleasure.

Regards and enjoy the music.
Raul.

Dear Newbee: +++++ " The reasons for a sub with monitors is obvious. More and better bass, when they are integrated properly. +++++ "

As Steve told us ( wider soundstage ) the use of subs are not only " more an better " bass, there are other important sound reproductions improvement when you use it.

+++++ " I believe that the best use of a sub is when your full range systems create bass problems in your room because the location of the main speakers creates very uneven bass response. +++++ "

THis is issue is very interesting, I never think about.

You are right: life is a trade off.

Regards and enjoy the music.
Raul.

Dear Tbg: You tell us, too, the trouble to integrate the subs with the main speakers and like I already told: this is our challenge. But I think it is worthwhile. The Beauhorns: I never heard it but I read very interesting things about.

+++++ " So the answer to your question is both absolutely you need subwoofers and absolutely no subwoofers are impossible. " +++++

I really like your answer and tell us everything about.

Regards and enjoy the music.
Raul.

Dear Dave : Tks for the links.
Try your system with two subs instead only one and try a crossover at: 80Hz, " listen " and decide.

Regards and enjoy the music.
Raul.

Dear Readster: The use of subs depends on many issues, like you say. I will try along this thread to explain: why we need it.

Regards and enjoy the music.
Raul.

Dear Tim: Yes, you are right: Velodyne DD series.

Regards and enjoy the music.

Raul.

Dear Raytheprinter: +++++ " ,i like to hear whats on the recording " +++++.

I share this statement with you and is one of the reasons: why we need subs. I know well your Paradigms ( nice sound ) and maybe you have to try hard again for integrate your unused sub.

Regards and enjoy the music.
Raul.

Dear Biomimetic: +++++ " I think subs have more to do with your own ear and the music you prefer: undertones and overtones plus the way the music is engineered are very important. " +++++

As we can see over this thread, there are many reasons for what we need or don't need subwoofers. Your statement is one or two reasons about.

+++++" . The Velodyne's to me just seemed to make an under-enthusiastic whomp-whomp sound - a real one note wonder. +++++ "

Well, this true if you choose a wrong croosverpoint/phase/gain ( volume )/room location. I can tell you, for sure, that with the HGS and DD Velodyne series that does not happen.

Regards and enjoy the music.
Raul.

Dear 76 doublebass: +++++ " ,but it added
more to every recording.The sub brought back the fullness
and proper timbre to the whole orchestra,and also gave every recording its proper depth of field. " +++++

These is something that the subs can give almost anyone.

+++++ " So do I need a sub now I DON'T KNOW? " +++++

You already give you the answer.

Regards and enjoy the music.
Raul.

Dear Sirspeedy: Well, maybe all of us need 4 subwoofers.

In my case, it will be a very hard alternative because right now my audio system is a " musical event ". It is not if it have: resolution, pitch, dynamics, accuracy, tranparency, neutrality, etc,etc....

It is, well: BALANCED.

It is not only the seamless subs integration, that does not means nothing " per se ", it is that is like music: balanced.

Sirspeedy, you have to hear it.

Regards and enjoy the music.
Raul.

Dear Blkdar: +++++ " . But going by music I have heard live, most contains at least bass harmonics that fill out the sound. " +++++

THis is other of the reasons for to have subs.

+++++" In some rooms (like mine) a 'fullrange' speaker can sound bloated because of room effect and tailoring a sub (or pair of subs) can be a better compromise. " +++++

I can see that you agree with Newbee and here again is where the subs can be used.

Tks for your words about my audio system.

Yes, this is my time: I will try to explain what are my bias and experiences about.

Regards and enjoy the music.
Raul.

Psychicanimal: I agree with you about.

Regards and enjoy the music.
Raul.

Dear friends:

Why it is important the use of subs on our home stereo audio systems ?

Well, for we can hear what is on the recording ( analog / digital / any ) we need a series of links ( audio items ) to build the whole chain for the music/sound reproduction.

All the links on the system chain are important and all of them have their particular distortions that put the " colors " to our " audio pictures ".

In this audio chain, in the analog case , the most imperfect links are at the front end: phono cartridges and the speakers. Here is where we have a lot of distortions ( of any kind ) because these audio music " translators " are truly an imperfect ones against electronics ( for example ). So, for me, these are the " tweak " links on the audio chain.

In this forum all of us already learn how to improve the cartridge link for a better music/sound reproduction ( less distortions ), but not many of us take care about the speakers distortions, other than the room interaction, that really " color " the final sound that we hear.

Why we take care about: VTF, VTA/SRA, Overhang, resonance tonearm/cartridge, SUT or not SUT, unipivot, air bearing, cables, tubes or not tubes, SS, DAC's, CD transports, and the like when all what we do can be corrupted at the end of the audio chain with full of speakers/room distortions.

Where the subs can help us ? :

Intermodulation Distortions: Almost any three ways speaker ( all two ways/one way ) has it's crossover frecuency ( low driver ) between 150Hz and 450Hz. I can assume that any of ours speakers system goes down flat ( at least ) between 60Hz to 20Hz.

What does that means ?, well that a single driver has to reproduce frecuencies/harmonics from 20Hz/60Hz to 150Hz/450Hz. With that kind of frecuency range here exist a great intermodulation distortions that put it's " color " on the sound reproduction.

You have to imagine that that single woofer/driver has to reproduce, at the same " time ", a 30Hz frecuency along a 350Hz frecuency: here is where exist that IM that gives heavy distortions in what we hear ( there is no perfect driver: moving coil, electrostatic, ribbon, etc.. The speaker designers has to choose the best " trade offs ", but the distortions are there. ): less clarity, less resolution, less precision, less natural balance, less pitch, les, less, less......., and this is what we are really hearing: LESS MUSIC.

If you read any manufacturer specifications on their speakers they never " write " the value of the IM or harmonic distortions, they tell us the frecuency range and how is flat on that range but never " talk " about distortions. I think that you know that when we have a speaker frecuency specifications, say: 28Hz to 22kHz +,- 3db, that is a very nice spec, that speaker low driver don't stop at 28hZ it's goes a few hertz below that frecuency with heavy harmonic distortion that increase the IM distortion of the sound reproduction of that driver and these additional distortions have a severe degradation in the reproduction of the MUSIC.

What happen when that low driver is free from those frecuencies ? ( main speakers: monitors or full range, it does not matters. My main speakers are flat to 22Hz and only 5db +.- at 18Hz and I have benefits with the subwoofers integration to my system ), below 80Hz ( this is the crossover frecuency that we find the best point to start to blend a subwoofer. Mines are at around this 80Hz frecuency: 78Hz,yours ( I think ) will be around that frecuency. ):

SUDDENLY the " lights are on ", your music/audio " life " its born: the mid bass is clean, the midrange is clean, the highs are clean: high resolution every where ( the distortions are almost gone ), and now you can really hear for the first time the MUSIC through your home stereo audio system: what a pleasure!!!!!.

This is truly a discovery for all of us that cares about MUSIC. We really discovery what kind ( quality/quantity ) of audio system we really have ( now we can do any evaluation of any audio item, not before. ) and where to work for a future improvements.

Now that we already settle in the subwoofers ( self powered ) with our main speakers ( yes, it is a hard work to do. We need at least: very good ears, love for music, experience with live music, patience, time and good muscles. We have to work with: location of subwoofers and the main speakers too, phase, crossover frecuency, volume/gain. We need two subwoofers not one and this issue is critical. TIP: avoid the common asumption that the crossover point should be at the low frecuency flat response of the main speakers, example: the speakers are flat at 40Hz, then you choose 40Hz for the frecuency crossover between the subs and the speakers, this is a great mistake: remember that we use subwoofers not only for a better and extended low bass but for a better midrange/midbass too. So, the frecuency crossover will be over that 40Hz: not at 40Hz or below 40Hz. ), we have others advantages:

- better quality low bass ( you can have at least one more octave ) and mid bass ( quantity? : you choose it: volume/gain ) ). Now we can heard the " foundation " of the MUSIC ( and its harmonics ) and this single issue is stunning for the pleasure to hear any kind of music. Now, we are nearest to the " real MUSIC ", nothing less.

The first time you can hear the subwoofers right blended on your stereo home audio system: YOU NEVER COULD LIVE WITH OUT THEM AGAIN, ANY ONE CAN, period.

- An improvement in the soundstage reproduction in all parameters: deep, front/side location, wide of the stage, etc...

- the main speakers amplifiers works best ( less distortion, more headroom, less chance of clipping, less amplifier stress, etc...) with out to handle the frecuencies range that now are handle by the dedicated subwoofers amplifiers. This is important for an SS amplifier but for the tubes ones is a must.

- Now the low bass frecuencies are handle for a dedicated driver that was build with specifics characteristics for to work in that frecuency range and this low bass driver is matched with an amplifier ( self powered subwoofers ) that was build with specifications that mates excatly what the low bass drivers needs about: frecuency response, output impedance, damping, power, etc..... You can't ask for more!!!

- Not only the IM distortion goes down but the harmonic distortion of the low driver of your main speakers goes down too, Btw, the whole harmonic distortion goes down, because ( in the case of my Velodyne's less than 0.5%: with's yours? ) ) the harmonic distortion of a well self powered designed subwoofer is usually " very low ". This means ( again ) less coloration: MORE MUSIC.

Btw, and this is not the subject on this thread ( sorry ): We choose Velodyne because after test/research, Velodyne was the only subwoofer manufacturer that answer our questions ( web site, e-mails, reviews ) about harmonic distortion ( and other parameters )on their subwoofers ( no, this was not the only subject for we decide for Velodyne but was an important one ).

I remember ( example ) that I ask to Revel ( three times ) which was the harmonic distortion of their subwoofers at 20Hz and 40Hz at 90db, 100db and 110db of SPL, they give me many answers but never were specifics about, I assume they don't know it.

Check the manufacturer specifications about for: REL, Revel, Aerial, Wilson, etc,... and you can't find it. Who cares about? : You and me that cares about M U S I C , want to hear M U S I C and needs to be nearest to the M U S I C .

All what I post here are my own experiences and that's what I like to share with all of you.

It works for you?, maybe. I think that you have to try if your speakers are not self powered or headphones.

Imagine how could your Wilson's, Dynaudio's, Karma's, Sonus Faber, Dali's, Merlin's, Martin Logan's, Aerial's, Spendor's, Harbeth's, Thiel's, Alon's, Talon's, Paradigm's, JM Labs, Epos, Avalon's, Boston'S, B&W, Magneplanar's, Proac's, Quad's, Revel, Totem's, etc, etc..... sound.

Better than that: don't imagine, try it.

I can tell you that it works for me and that I'm extremely satisfied with the subwoofers integration in my home stereo audio system. Really I'm. !!!!!!

WELL: DO YOU THINK YOU NEED SUBWOOFERS?

Best regards and enjoy the music.

Raul.

Dear Biomimetic: It happen that I use supertweeters in my audio system.

Take a look: http://forum.audiogon.com/cgi-bin/fr.pl?vdone&1115433273&view

Regards and enjoy the music.
Raul.

Dear friends: There are other improvemenst when you mate subwoofers to your home stereo audio system, example:

Usually the location of the speakers in our room ( with out subs ) is a " compromise " ( trade off ) between the best performance at the bass against the best performance at the mid/high frecuencies ( only in a few cases the location is with out any " trade offs ". ), when we integrated the subs in our audio system we can have the best of both " worlds " and you will be in " heaven ".

Now you can really know how good ( or not ) is not only your audio system but any single audio item: cartridge/tonearm/cables/TT/preamp/amplifier/CD, and now you can detect any sound reproduction performance problems in those audio items and try to fixed/exchange: now and only now ( not before ) you can say " this is the best cartridge or tonearm or SUT ,etc.. " that I ever heard.

When your subs are settle-in in your system you don't have only a great high resolution system but a truly full range audio system in favor of the M U S I C .

Really, you don't know what you have ( the great potential of your system that right now you are loosing. It does not matters what you have. ) till you have yours: subwoofers. It is a pleasure that you can't imagine !!!!!!

Regards and enjoy the music.
Raul.

Dear Ray: As I already post the integration of the subs in any room is not an easy task and almost always we need to do some room's treatment but always is wortwhile every effort about.

Never is a wasting time to try again with the subs: you have to try and after that you will do the room treatment, not before.

Regards and enjoy the music.
Raul.

Dear Eldartford and Newbee: I suggest that you read carefully the links that Davehrab post here it can instruct about.

Btw, remember that the integration of subwoofers it's not only for a better ( quality/quantity ) bass but for a better midrange too.

Regards and enjoy the music.

Raul.

Dear friends: I wonder why many of the " regulars " on this forum decide ( till today ): " stay away " on this extremely critical subject for the analog music/sound reproduction.

Share with all of us your knowledge and points of view about, in that way all we could receive related audio benefits.

Regards and enjoy the music.
Raul.

Dear Eldart: +++++ " I regard the "subwoofer" not as a separate speaker system, but as part of the main speaker system...the part that the manufacturer left out because of size and cost. " +++++

I agree with you. It is always more " confortable " to design speakers with out that low end octave. So, they give us what they want not what we need, well: not what the MUSIC needs.

Like Stevecham told us, the name of the game is: "Integration" .

Regards and enjoy the music.
Raul.

Dear Gmorris: +++++ " . I have been able to obtain seamless integration of the subs with the maggies after many weeks of experimentation and frustration. " +++++

Always is a hard work for the seamless integration of the subwoofers: test and error experimentation.

The Maggies are wonderful main speakers and I never heard along with subwoofers, but I can imagine.

+++++ " To fully recreate the recording space you need the lower octaves even if the recording involves instruments sans the lower registers. " +++++

THis is absolutely true. I agree, too, with any single word about the advantages of two subs instead only one.

Regards and enjoy the music.
Raul.

Dear Eldartford: +++++ " I run the SWs up to 200-300Hz, and there is no doubt that it is better. " +++++

I can't imagine this situation ( maybe because I don't have enough experience with the Maggies ). Which are the frecuency limits of your SWs ?

Regards and enjoy the music.

Raul.

Dear friends: This is something that could help you to integrate the subs to your main speakers:

- first you have to find the best place for your main speakers.

- you can do that with the whole system " on ": speakers/electronic crossover/subs. Then choose the crossover point: 80Hz ( it is a good point to start ) and turn " off " the subs volume/gain and listen to your main speakers that now are working from 80Hz and up.

- listen and listen and listen through your main speakers and move them ( if neccesary ) till you find the best mid/high frecuency response performance.

- then do the same with your subs: alone ( main speakers off ) till you find the best room interaction with.

- now, with the whole system " on " : listen and listen and listen till you identified problems with the seamless integration of the main speakers/subs, that is the target.

- here you have to " play " with small changes in: crossover frecuency, phase, volumen/gain, room treatment and very small changes in the site of the subs/main speakers, till you " done ".

This is only a way to do it and give me the best results to integrate subs, not only in my system but on severals others systems. Sure you can do it in a scientific way. There are no absolute rules here, the only one is: " test and error ".

Regards and enjoy the music.
Raul.

Dear Goatwuss: From your preamp: left output to your left side sub and right output to your right side sub .

About your REL question: my english is really bad and I can't understand what you mean.

Regards and enjoy the music.
Raul.

Dear Biomimetic: About your superteeters question: no, it is not tiring. I think that, like the subwoofers, in many audio systems the integration of STs is a must to have too.

Regards and enjoy the music.
Raul.

Dear Darkmoebius: +++++ " Perhaps it is best to run true L/R stereo signals to the subs instead of summed mono. " +++++.

Absolutely. If you have two subs it is a must to run in stereo way.

Bryston and Pass have very good X-over that can meet your targets.

Regards and enjoy the music.
Raul.

Dear Darkmoebius: I think that the Pass is an expensive unit, very well made and I hope meet your targets.

The Bryston is a very good one too and with many user friendly options. Second hand: "inexpensive " too.

Yes, please let us know how it works.

Regards and enjoy the music.
Raul.

Dear Goatwuss: I'm sorry for my mistake about your REL question, the problem was not my english but my unknow REL concept about subs: but now I understand how the REL subs work.

I think that you can't run the RELs on true stereo fashion, but if exist that alternative it really does not help to a stereo sound reproduction because it dos not roll-off ( take-off ) the low bass from your main speakers.

The REL desing only cover one of the objectives of a subwoofer: better quality/quantity low end. Its use is more for HT than for a true stereo home aplications, it can't really help here.

Regards and enjoy the music.
Raul.

Dear Eldartford: Tks for the Maggies info and ¡congratulations! you really do a great job with your self-design subwoofers.

Regards and enjoy the music.
Raul.

Dear Dan ed: +++++ " you have to control the bass response if you want the mid and high frequencies to sound good and proper. I assume that this is very much true of systems that use strong SW's. " +++++

THis statement is absolutely true.

The control of the bass response is important but to have that bass is really important too, with out it we can't have proper stereo music/sound reproduction and can't enjoy the complete pleasure of hearing MUSIC.

I know your 10t, and I like it, and you can do a huge improvement in the quality sound of your system with the integration of two subwoofers.

Regards and enjoy the music.
Raul.

Dear friends: This is something important issue that I want to share with all of you:

As you can read in my " system " I use Pneumatic suspension insulators from Audio Technica in my Micro Seiki TT and Van Slike insulators in my two Acoustic Signature TTs, both type of insulators do an excellent job with my TTs.

Last week I receive two additional sets of the same model of Audio Technica insulators. So I installed on the TTs and then the Van Slyke were with out job.

I ask me what could happen if I install below my subwoofers?

What a great surprise: these Van Slyke insulators do wonders in my system. Now I have a cleanest low end, not only more tight but " more bass ", better pitch, better image system, less bass overhang, etc...

This was a revelation for me and in my system. Of course I'm truly happy about.

I'm using the Van Slyke Tri-Orb Heavy ( TOH ), three of them in each sub. Three of them support around 200lbs and four of them over 500lbs: this is important because you can use the Tri-Orbs like the footers/insulators of your whole system raks: think about.

This is the site: http://www.vsengr.com/triorbs.html

Regards and enjoy the music.
Raul.

Dear Downunder: I forgot: +++++ " Don't your amps run the speakers full range down to 22hz?? " +++++

No, my amplifiers/speakers run/work from 50hz up and the self powered subwoofers from 60hz down.

Regards and enjoy the usic.
Raul.

Dear Peepoy2: I think that you own the Trio, right? .
Well, Avantgarde are truly great an very special speaker design. Your model crossover point to the subs module is around 100Hz, I like it.

I think that before you go for the second Velodyne, try to talk with the Avantgarde people because their subs integrated design in the Trio has special characteristics in the crossovers for the subs module can integrate seamless to the horn module.

Now, with the info from Avantgarde you can check if with the Velodyne you can mimic the Avantgarde crossover characteristics and if you can then go for the Velodynes.

Other alternative is that your dealer can borrowed the additional Avantgarde subs modules for you can test in your system.

Regards and enjoy the music.
Raul.

Dear Todd: +++++ " It appears as though you advocate using a crossover to take the low freq. information away from the main speakers (only have the sub handle low freq, as opposed to running both subs and speakers full range). " +++++

Yes, this is the main idea. You can do this using the internal crossover of the subs and running the signal to your main amplifier from each sub after the signal ( that comes from your preamp ) pass through the sub internal crossover.
You can do it, too, using an external crossover to run the signal to the main amplifiers. The Pass and Bryston crossovers are very good ones for this application.

+++++ " If the main speaker is a monitor that is -3db at 40hz, is it really necessary to use a crossover? " +++++

Yes, absolutely. Please read carefully at: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&27&4#27

Regards and enjoy the music.
Raul.

Dear friends: Something that works very well with my Velodyne subs: I mass loaded ( top panel ) with around 25kg.

This can work with your subs. Try it and decide.

Regards and enjoy the music.
Raul.

Dear Audiofeil: I'm using " dead weigh " ( smaller than the cover ): the ones that use for " muscle growth excersice " ( the right words are not on my vocabulary ).

You can " see it " ( a little ) in the " picture " of my " system ".

This is temporary. I'm looking for a ( same size ) steel plate with a weigh around 45kgs. Stay tunned.

Regards and enjoy the music.
Raul.

Audiofeil: Yes.

Regards and enjoy the music.
Raul.

Dear friends: As you know the location for the proper streo integration of the subwoofers is really critical. We have to play around with this subject, many times in incredible " location/way ". Don't be afraid about: try everything till you are satisfied.

My subs are in front of the main speakers and side firing eachother. Till today this is the best " location"way " in my room.

Time consuming but with a big sonic reward. ¡ Try hard on this !.

If you can try to read this: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&31&4#31

Regards and enjoy the music.
Raul.

Dear Scott: Btw, I choose ( too ) 1st order filter for the high-pass on my system. This high-pass filter is inside of my 20.6s. It work for me.

+++++ " So, how to find the proper balance????? " +++++

I think there are no rules here other than: test, test and more tests. Now, why don't contact with the designer/builder of your subs/speakers?

The " spot on " integration of the subwoofers is not an easy task, I take more than six months to do it and today ( time to time ) I still do little adjustements.
I know that this hard work sometimes is very frustating but I can asure you that is worthwhile. Good luck!!

Regards and enjoy the music.
Raul.

Dear friends: This is for the people that already have or want to have or likes REL subwoofers.

The REL subwoofers are a very good ones subs, no question about.

As any one can " read " in the REL owner manual, that the REL design is primarily for " bass reinforcement on full range speakers ". That's why the REL people recomended that their subs must be installed near the corners and why the REL subs ( normally ) works summing-up the left/right channels signal for works in mono way for less distortion. Other characteristic is that the REL subs does not have high-pass filters for a true stereo performance.

The bass reinforcement REL design is oriented to the HT application and not for a " true proper stereo integration of subwoofers for a music/accurate sound reproduction at home ".

Of course, if you like, you can use it in your stereo system but is totally inadequate an inaccurate for the MUSIC reproduction. Maybe you could use, in the right way, the REL subs with the help of an external electronic crossover.

Regards and enjoy the music.
Raul.

Dear Goatwuss: About fast/low subwoofers please read the links on this link: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&4&4#4

Regards and enjoy the music.
Raul.

Dear Darkmoebius: I'm not very familiarized with the Bailey subwoofers but I understand that has integrated low/high pass filters: why you are using the Paradigm XO?

Regards and enjoy the music.
Raul.

Dear Scott: Good luck with your Edgar integration.

Regards and enjoy the music.
Raul.

Dear Sirspeedy: Remember the REL subs thread that suddenly " disappear?

Well, in your last post you write something like: " I think there will be no improvement in my system taking out the 80Hz and below from my Ascents. "

With all my respects and in this critical issue, what you " think " or what I " think " it does not matters and don't help you. The only way is to TRY IT, you don't have almost nothing to loose: the second hand subs market is a very " healthy " one.

Please read very carefully at: http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1117893153&openflup&27&4#27

If some day you decide to try you will be shocked with the improvement about.

Regards and enjoy the music.
Raul.

Dear friends: This is an article, that an Auiogoner send to me yesterday, from Audio Perfectionist Journal about the subwoofers subject and doing a Vandersteen review about: this is not the issue, only the statements about the whys of the subs:

ntroduction
Suppose I told you that you could add two
components to your system that would reduce
intermodulation distortion in the midrange by a
factor of two or more, dramatically improve the
resolution of midrange and high frequency detail,
double or triple the dynamic range capability of
your system without changing your existing
amplifier or speakers and improve imaging more
than you can imagine. You would probably be
interested, right? But wait, there’s more.
These same components would allow the
amplifier to maintain tighter control over the
speakers in the mid-bass and lower midrange.
They could extend bass response to infrasonic frequencies
while lowering bass distortion and
improving the system’s ability to accurately convey
the rhythm and pace of music. And these
same components could virtually eliminate the
uneven response at lower frequencies caused by
room standing waves.
Does all that sound too good to be true?
Are you concerned about the possible cost of all
this improvement? If all this is so easily achievable,
are you wondering why you’ve never heard
about it before?
Let me assure you that all these sonic
improvements can be yours and I’ve been conservative
in my estimates of the level of audible
improvement you’ll get. You can have all this for
$2,500 and you can upgrade in two steps of
$1,250 each. If you are starting from scratch, you
may actually reduce the cost of a complete system
by purchasing a less expensive amplifier and a
lower cost speaker model, along with these components,
and end up with better overall performance.
Few people have figured this out and fewer
have spread the news, but it’s all true.
Of course the components I’m talking
about are a pair of powered subwoofers—but not
just any subwoofers. These subwoofers need to
Page 12 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
Page 13 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
have some special characteristics which we’ll get
to in a minute.
Subwoofers?
I’m sure you are shaking your head in disbelief
right now, and thinking that I’ve lost it. You
may have auditioned some popular subwoofer
models and been less than impressed with their
performance and I won’t disagree. Most subwoofers
available today are simply unacceptable
for use in a system designed for critical music listening.
Yes, we have all heard those thunderous
thudpuckers, commonly called subwoofers, that
add to the excitement of movie sound and simply
ruin the sound of music. How can I claim that
these things can actually be beneficial in a highend
audio system?
Here are two reasons that your experience
may conflict with my statements: most subwoofers
weren’t designed for good musical performance,
and most dealers set subwoofers up
poorly, on purpose.
When properly integrated with the system,
subwoofers blend seamlessly with the main
speakers and don’t make their presence known.
But that’s a very hard sell to the average consumer
and selling is the name of the audio game.
Subwoofers are supposed to add bass, right?
After their initial forays into the market,
few manufacturers continue to try to make subwoofers
that accurately represent music. Why try
to educate consumers when it’s easier to just give
them what they think they want? Boom!
Subwoofer makers soon learned what
dealers had already figured out: if they can’t hear
it woof they won’t buy it. Manufacturers started
to build subwoofers with high-Q alignments and
vents in order to provide more “slam.” Dealers
started to set up their demonstrations for maximum
thump, and maximized sales figures.
Awareness of the basic concepts of specialized
bass reproducers faded or was suppressed.
Home theater exacerbated this situation.
People today expect a subwoofer to rattle their
fillings and the exaggerated bass that most subwoofers
deliver is incompatible with accurate
music reproduction.
But there is more to bass than boom—bass
is the foundation of all music. And there is more
to subwoofers than bass. They reproduce bass frequencies
to be sure, but bass extension is possibly
the least of the sonic benefits offered by good
powered subwoofers.
Why Good Subwoofers Improve Sound
In order to provide the benefits mentioned
at the beginning of this article, subwoofers must
utilize a dedicated bass amplifier, and the main
amplifier and speakers must be high-pass filtered
using a passive, first-order device.
A high-pass filter does just what you
would expect: it allows frequencies above the cutoff
point to pass, and blocks frequencies below
that cut-off point. The attenuation of a first-order
filter is 6dB per octave. That means that the signal
will be reduced in amplitude by 6dB, one octave
below the crossover or cut-off point. If the
crossover point is 80Hz (-3dB), the signal level at
40Hz will be -6dB relative to the signal level at
80Hz, and -9dB relative to the signal level in the
midrange. The signal amplitude will continue to
fall at a rate of 6dB per octave as the frequency
decreases.
A passive, single-pole filter at the input to
the amplifier is the only sonically transparent way
to high-pass the main speakers.
The subwoofer amplifier will require a
low-pass filter to prevent frequencies above the
selected crossover point from being sent to the
subwoofer. A low-pass filter passes low frequencies
and blocks higher frequencies.
A subwoofer with an internal amplifier,
commonly called a powered subwoofer, will
require electronic compensation to allow both
infrasonic response and acceptable dimensions for
home use.
Given these stipulations, a pair of powered
subwoofers can provide the following benefits:
Page 14 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
1. Better performance from your speakers.
Full range loudspeakers utilize the same
driver to reproduce both the bass range of frequencies
and at least part of the midrange. For
optimum reproduction of midrange frequencies
little cone movement is required, and a relatively
small driver is necessary to provide quick
response and good dispersion.
Low frequencies require lots of air movement,
demanding greater cone area and more cone
movement. In engineering terms, the back-andforth
movement of the cone is called excursion.
Cone excursion quadruples with each halving of
frequency.
Good midrange reproduction requires the
use of moderately-sized drivers and good bass
reproduction requires lots of cone area, so most
full range speakers compromise the quality of
both bass and midrange by utilizing woofers that
are too small to provide good bass yet too large to
deliver the best midrange quality.
The cone of the 8-inch or 10-inch woofer
typically found in a full range loudspeaker will be
required to make peak-to-peak excursions of perhaps
an inch to deliver audible levels of output at
40Hz and it will have to do this while producing
300Hz (or higher) midrange signals at the same
time. A 6.5-inch woofer will make a better
midrange driver but it will have to work even
harder to deliver low frequencies and IM distortion
in the midrange will rise.
Intermodulation distortion occurs when
one frequency modulates (alters by its frequency)
another. Peak-to-peak cone excursions of an inch
or more, which may be required to reproduce a
40Hz signal, will have a substantial effect on a
signal at 300Hz. The 300Hz signal will increase
slightly in frequency when the cone is moving
towards the listener to reproduce the 40Hz portion
of the signal, and decrease in frequency when the
cone is moving away from the listener. This is
only one mechanism of IM distortion, which is
sometimes called Doppler distortion. There are
other forms of IM distortion.
All dynamic drivers exhibit some nonlinearity
in outward versus inward cone movement.
High cone excursion exacerbates nonlinear driver
response and causes harmonic distortion.
Harmonic distortion occurs when a harmonic
(multiple) or side-band of the desired signal is
produced due to nonlinear behavior of the electrical,
magnetic or mechanical mechanism of the
driver. If you want to reproduce 40Hz and you get
some output at 160Hz as well, that’s harmonic
distortion.
The results of high excursion of the
woofer cone are intermodulation distortion of the
midrange signal and increased harmonic distortion
of the bass signal. And there’s more.
The small woofers required to maintain
reasonable midrange performance in a full range
speaker don’t do a very good job of reproducing
the lowest bass frequencies but they do put a lot
of energy into the speaker cabinet structure and
this is very detrimental to sound quality.
As the woofer cone makes these large
mechanical movements to pressurize and rarefy
air, an equal and opposite force is applied to the
woofer basket, or frame, which is attached to the
speaker structure. This force excites resonances in
the cabinet structure and tries to move the whole
speaker back and forth. Cabinet resonances color
the sound in the midrange. Cabinet movement
distorts high frequencies.
A backward and forward motion of just a
few thousandths of an inch may represent a major
percentage of the total excursion of the tweeter
diaphragm as it attempts to reproduce subtle high
frequency details. The result of structural movement
is IM distortion of the midrange and high
frequencies.
If you are skeptical about the sonic consequences
of woofer energy moving the speaker
cabinet, think about speaker spikes. A reduction in
cabinet motion is the main reason that spikes
beneath the speaker improve sound. Remove the
spikes and see (no, hear) what happens.
As you can see, a full range loudspeaker is
a bundle of compromise. It is asked to perform
many conflicting tasks. There is an old Chinese
Page 15 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
proverb that goes something like this: “man who
chase two rabbits have no meat for dinner.” By
the same token, a speaker that tries to provide
both bass and the rest of the spectrum compromises
the quality of both.
A single-pole, passive high-pass filter at
the input to the amplifier can cure or minimize all
these speaker problems and improve performance
dramatically. This sonically transparent filter will
reduce woofer cone excursion which will reduce
distortion in the bass, midrange and treble as
described above. The result will be better definition,
better imaging, tighter control, greater
dynamic range and a better presentation of the
rhythm and pace of music. The only thing missing—
besides distortion—will be low bass and that
will be reproduced by specialized devices
designed just for that purpose—powered subwoofers.
2. Better performance from your amplifier.
The major energy demands in music occur
at low frequencies. The major current demands
from an amplifier are at low frequencies. When an
amplifier distorts because of demands for power
that it cannot meet, the output waveform is flattened
at the top and bottom. This distortion is
called clipping because the positive and negative
signal peaks have been “clipped” off.
Amplifier clipping becomes evident at
high frequencies but clipping is almost always
caused by energy demands at low frequencies that
exceed the capability of the amplifier.
Clipping is the primary cause of speaker
damage because a clipped waveform “fools” the
crossover network in the speaker which then passes
high power to the high frequency drivers.
An amplifier in normal use will be clipping
at least occasionally. The percentage of time
that the amplifier is driven to the point of clipping
or beyond will have a profound effect on sound
quality. As the amplifier approaches clipping the
sound will become slightly hard, then harsh, and
then, as the amplifier clips, a shattering distortion
will be heard. This distortion eventually destroys
tweeters and crossover networks.
A single-pole, passive high-pass filter at
the input of the amplifier can eliminate all these
distorted sounds and make the amplifier sound
smoother and more relaxed. The amplifier may
seem to be three times more powerful. Removing
the huge low frequency current demands from the
amplifier, by reducing the level of the input signal
at low frequencies, allows the amp to coast along
with lots of power in reserve. The system will
play at much higher levels with much lower distortion,
providing a greatly improved listening
experience.
The high current necessary for accurate
bass reproduction will be provided by specialized
amplifiers designed just for this purpose—the
amplifiers in the powered subwoofers.
3. Better bass.
Designing a product to perform a very
specific task requires less compromise.
Subwoofers are designed to reproduce a small
range of frequencies at the lowest audible range.
That’s about as specific as it gets in audio.
When compared to full range speakers,
powered subwoofers can provide the following
advantages: more cone area, greater linear excursion
capability, more amplifier power at low frequencies,
and electronic compensation for falling
output at the lowest frequencies. Subwoofers can
also have smaller, stiffer, less resonant enclosures
and can be placed in the optimum position to
introduce bass energy into the room.
Eliminating the compromised bass output
from the main speakers by high-pass filtering the
input signal to the amplifier will dramatically
improve the quality of reproduction in the midbass
range. Improving the mid-bass provides a
better sense of rhythm and pace and makes it easier
to follow the tune of the bass.
4. Better room interface.
The pressure-zone microphone (PZM) was
developed after it was determined that smooth frequency
response at lower frequencies could not be
Page 16 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
obtained from a stand-mounted microphone due
to interactions with the room boundaries. Placing
a conventional microphone on the floor smoothed
the response curve but caused a gradually rising
bass output. Compensating for this bass rise gave
us the PZM microphone. A similar effect occurs
with speakers.
For good imaging and midrange detail full
range speakers must be placed well out into the
room. Bass response from these speakers will be
uneven due to room interaction. This phenomenon
is frequently attributed to “standing waves.”
Removing bass from these speakers and
redirecting it to a subwoofer placed in the corner
of the room will ameliorate most of these room
anomalies. The subwoofer will load the room
from a pressure zone, smoothing response across
the bass range. Adding a second subwoofer,
placed in a second corner, allows low frequencies
to be introduced from two different positions
within the pressure zones of the room virtually
eliminating bass irregularities. (You must remove
other sources that store and release energy at low
frequencies as described in the room treatment
article.)
5. Reduced system cost.
In a given manufacturer’s amplifier line,
the more expensive models usually offer more
power and little else. In fact, smaller amplifiers
frequently sound better than their big brothers and
they always cost less.
The Levinson 33H mono amps that I use
cost about $15,000 less than the Reference 33
amplifiers from the same company. Both models
are essentially the same design, with the larger
version offering only higher output power.
Most loudspeaker manufacturers offer a
range of models that differ only in their ability to
produce bass. Bigger, more expensive models provide
extended bass response with bigger woofers
and larger cabinets. Except for bass extension, it’s
not unusual to find that the smaller models in a
given line of speakers actually sound better
because they have smaller woofers that offer better
midrange performance and the smaller cabinets
add less box sound. Compare the smaller Dunlavy
models to their larger brothers for example.
The Vandersteen 3A Signature speakers
that I use in conjunction with a pair of 2WQ subwoofers
deliver 90% of the performance of the
Vandersteen Model 5s for 60% of the price (3A
Sigs and two 2WQ subwoofers cost about $6,000
and Model 5s sell for about $10,000). My speaker
system delivers a time- and phase-accurate
response over a usable range of 18Hz to 30kHz.
What other speakers can offer that for $6k?
Some reviewers claim that the 3A
Signatures lack the “detail and definition” of the
Model 5s. You may find this puzzling because
both models share identical midrange and tweeter
drivers and use essentially the same crossover network
in this range. Why the perceived performance
difference? Model 5s have a slightly more
inert cabinet structure and they have built-in, powered
subwoofers.
The use of powered subwoofers can allow
a smaller amplifier and a pair of lower-priced
speakers to equal or outperform their more expensive
counterparts. The result is better sound for
less money. Who doesn’t want that?
Why Most Subwoofers Don’t Work Well for
Music Reproduction
Not so many years ago, few people were
aware of the concept of specialized bass speakers.
Explaining what a subwoofer was and the sonic
benefits it could provide were difficult tasks
before the home theater craze hit the public.
Today, people are rushing to add subwoofers to
their audio systems to provide the visceral excitement
that only thunderous bass can supply.
Thunderous bass output makes an onscreen
explosion or gun shot more physically
involving but it can also alter the tonal balance, as
well as the rhythm and pace, of music. Most subwoofers
seem to march to the beat of a different
drummer instead of the one who is playing with
the orchestra.
Today the average consumer believes that
Page 17 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
These illustrations compare frequency response (black trace), phase response (purple trace), impedance (yellow trace), and
group delay (blue trace) for the same JBL 2235H 15-inch driver mounted in a second-order sealed enclosure (above) and in a
fourth-order vented enclosure (below). You can learn a lot about the performance trade-offs involved in the choice of vented
versus sealed enclosure design from studying these graphs. In my opinion, the trade-offs make vents acceptable for use in full
range speakers and totally unacceptable for subwoofers that are meant to reproduce music. A conventional vented design offers
inferior performance in every area except one: output level capability.
the only purpose of a subwoofer is to add bass
and many music purists derisively refer to them as
“fart boxes.”
There are many reasons why boom-box
subwoofers may do a good job of reproducing
explosions and perform poorly when reproducing
music.
1. Phase shift and group delay cause subwoofers
to start late.
Picture a marching band with the bass
drum following about a block behind the rest of
the players and you’ve got a pretty good image of
the major problem with most subwoofers—the
sound they produce is just out of step with the rest
of the music. There are many reasons for this but
most revolve around phase shift and group delay.
Acoustic phase in this instance has to do
with the time relationships of the launch of air
pressure waves towards the listener. Phase shift
that varies with frequency alters the time relationships
between different frequencies. A resonance
in the pass band causes phase shift. Filters cause
phase shift. A speaker in a box is a filter.
When two elements like a subwoofer and
a main speaker have an overlapping frequency
range, or are reproducing different parts of a single
note, such as the fundamental and the harmonics
of that fundamental, you want both to be in
step. If the subwoofer cone pushes out when the
main speaker’s woofer cone is moving inward,
things get out of sync.
Group delay is a complex concept. It is the
negative of the derivative of the phase curve with
respect to radian frequency. Group delay describes
how well the time relationships between a small
group of frequencies are preserved within a narrow
range of frequencies. Time delay and group
delay are not necessarily equivalent but a delay to
one group of frequencies changes its time relationship
to the rest of the spectrum.
Look at the illustrations on page 17 comparing
phase response of vented and sealed enclosure
designs. Trying to synchronize the phase of
the main speakers and the subwoofer will be diffi-
cult with a sealed enclosure subwoofer design and
virtually impossible with a vented design because
of phase shift as the system passes through resonance
in the pass band. Note the 17ms group
delay at the 32Hz tuning frequency of the vented
design.
Subwoofers with a fundamental resonance
in the pass band and a steep slope low-pass filter
at the input will produce output that is delayed in
time relative to the main speakers, and this delay
will vary with frequency.
Subwoofers that start late sound slow and
plodding. They distort the overall waveform even
if their own distortion products are low.
2. High Q makes subwoofers stop late.
An electrical filter will oscillate or ring, to
some extent, after the signal stops. The steeper the
slope of this filter, the more it will ring. The higher
the “Q” of this filter, the more it will ring.
Mechanical filters work the same way. In
fact, all the mechanical properties of a loudspeaker
can be expressed with electrical equivalents and
modeled by electrical circuits.
A woofer in an enclosure is a high-pass filter.
It passes frequencies above the cut-off or low
frequency limit of the design and the signal rollsoff
below this point at a rate determined by the
design. A sealed box acts as a nominal secondorder
high-pass filter and a vented enclosure will
typically display fourth-order high-pass characteristics.
The vented design will ring (oscillate)
about twice as much as the sealed design after the
signal stops.
The “Q” of the mechanical system affects
oscillation, too. System “Q” defines the shape of the
response curve and the amount of damping to overshoot
or ringing (oscillation after the signal stops) that
the system will provide.
Asealed enclosure with a Q of .5 is considered
a “critically damped” alignment with a step response
that has no overshoot. For a given driver, a Q of .5
requires the largest box. This low-Q alignment has a
downward-sloping response curve but offers the best
possible transient performance and the lowest frequency
extension at -10dB.
Page 18 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
Asystem Q of .577 is a Bessel alignment
which has the most linear phase response and offers
slightly less damping.
When Q =.707 we have a Butterworth alignment
with the flattest amplitude response. This is the
most common alignment for “high-end” subwoofers
because it offers a “full” sound which is still well controlled.
System Q near 1.0 delivers a peaked response
but allows the smallest box size still considered by
some to be high-fidelity. Asubwoofer with a system Q
over 1.0 is a boom box with a peaked response curve
and lots of overhang. Guess where most home theater
subwoofers fall.
Subwoofers that play on after the signal has
stopped (due to oscillation), sound slow and muddy.
The Q and slope of the high-pass filter formed
by the subwoofer acoustical system has a major effect
on the sound of the bass the subwoofer produces, but
there’s more. The subwoofer is a mechanical high-pass
filter but it must be used with an electrical low-pass filter
and those cause problems as well.
3. Steep filter slopes and direct-radiating drivers.
Most subwoofer designs include one or
more drivers that radiate directly into the room.
It’s commonly assumed that subwoofers shouldn’t
be allowed to encroach on the midrange where
they perform poorly so the conventional wisdom
mandates a steep-slope low-pass filter to prevent
output above the bass region. There are some
drawbacks to this approach.
Page 19 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
This illustration shows the effect of system Q on frequency response. Notice that the low-Q alignments start sloping down sooner but
ultimately extend lower in frequency at the usable low frequency limit of -10dB. Remember that the low-Q alignments provide far better
damping to oscillation after the signal ceases.
A low-pass filter with a fourth-order slope
will cause another complete phase rollover,
increasing signal delay. Even with this steep attenuation
curve, side band distortion will still be
audible if the driver radiates directly into the
room.
All drive elements will break-up (display
non-pistonic cone behavior) at some frequency.
Filtering below this frequency prevents the signal
from stimulating this behavior. Many other anomalies
such as cone resonances, surround reflections
and “flapping,” magnetic nonlinearities and basket
ringing will remain audible as side-band distortion
even without frequency-specific stimulation. And
some midrange frequencies will still pass through
the filter at attenuated levels.
Midrange signals (even at low levels) and
side band distortion detract from the quality of
sound from the main speakers and draw attention
to the position of the subwoofer which should be
spaced away from the main speakers.
4. System resonance in the pass band.
Removing resonances from audio components
is generally considered to be a good idea but
subwoofers are designed to create resonance.
A vented subwoofer has two resonances
right in the middle of its pass band. The vent resonance
is tuned to play at frequencies where the
output of an unassisted driver would be falling.
Much of what you hear from a vented design is a
production of the subwoofer rather than a reproduction
of the signal.
Sealed enclosures are better with only a
single resonance in the pass band. One is better
than two, as you can see from the graphs on page
17, but none is better yet as we’ll see later.
When the subwoofer passes through a resonance
a big shift in phase occurs. Look at the
graphs of phase response for sealed and vented
enclosure designs and see the effects of resonance
on phase. (System resonance occurs where the
impedance peaks. Note the single peak in the
graph of the sealed enclosure and the dual peaks
in the graph for the vented enclosure. The dip
between the impedance peaks indicates the tuning
frequency of the vented enclosure.)
Subwoofers with a resonance in the pass
band will tend to emphasize the frequencies
around this resonance. The higher the Q the
greater the emphasis. Ever hear the term “onenote
bass”?
5. Dissimilar amplifiers for high and low frequencies.
A powered subwoofer may have an internal
amplifier that is designed for optimal performance
when driving the specific load of the subwoofer
drivers. This amplifier will almost always
have electrical compensation for the falling
response of the subwoofer driver(s) which will
typically be housed in an enclosure that is smaller
than ideal—because nobody wants a subwoofer
the size of a refrigerator in their living room.
A perfect subwoofer amplifier and the
amplifier that is best suited for driving the main
speakers may be very different electrically and
sonically. For instance, a bipolar solid-state ampli-
fier will offer the best performance for bass but a
MOSFET or tube amplifier may sound better driving
the main speakers.
Transfer function is a measurement that
compares the frequency and phase response of the
output from a device under test to the input signal.
If the transfer function of the main amplifier is
very different from the TF of the subwoofer
amplifier, this sonic dichotomy may have a negative
impact on overall sound quality.
Making a Subwoofer to Play Music
A subwoofer should march in step with the
rest of the band and stop playing when the song
has ended. Most do neither.
Subwoofers should be positioned in the
room corners to properly load the room from pressure
zones, creating the smoothest bass response.
If the subwoofer has a “Q” higher than .5 (most
do) it will exhibit a rising response when placed
in a corner.
So how can a subwoofer be designed that
Page 20 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
doesn’t suffer from the performance deficits
described above?
We can eliminate the problem of subwoofers
that start late by blending the subwoofer
and the main speakers using a first-order
crossover for transient-perfect phase response.
This filter system can be implemented in an
unusual way: the high-pass section can be placed
at the input to the amplifier driving the main
speakers and the subwoofer amplifier can sample
the output from this amplifier, including its sonic
signature and phase characteristics. The subwoofer
amplifier can have its frequency response
tailored to compensate for the falling response of
the input signal and the falling response of the
acoustic system that is operating primarily below
system resonance. (More about that in a minute.)
Blending the amplifiers in this way will
ameliorate the discontinuous sound created by
dissimilar amplifier designs driving different parts
of the spectrum.
We can eliminate the overhang of subwoofers
that stop late by designing for a target Q
of .5 to achieve critical damping, along with the
greatest usable bass extension, and to allow corner
placement without a rising low-end response.
The driver(s) can be slot loaded to
mechanically filter out side band distortion and
midrange frequencies. And the system can be
designed to operate primarily below the fundamental
resonance so that no resonance can cause
sonic emphasis or phase shift in the pass band.
This all makes perfect sense and I’d like to
take credit for thinking it up all by myself. But I
didn’t—Richard Vandersteen did. What I have just
described is the Vandersteen 2WQ powered subwoofer
which has been subtly but continuously
refined since it was first brought to market sixteen
years ago. It is the most sophisticated product of
its kind available today.
The Vandersteen 2WQ Subwoofer
The Vandersteen 2WQ subwoofer is completely
unique in a number of ways. It takes
advantage of the fact that loudspeakers in sealed
enclosures offer very predictable amplitude and
phase response characteristics at frequencies
below the fundamental resonance of the system.
The 2WQ operates primarily below fundamental
system resonance to provide frequency and phase
linearity that cannot be achieved by conventional
designs with resonances in the pass band.
It uses a phase-perfect first-order crossover
with special characteristics. The 2WQ samples the
output from the amplifier that is driving the main
speakers for better system integration.
It uses feed-forward error correction to
prevent output errors before they occur and a
unique protection circuit that does not compress
signal dynamic range. The 2WQ will not produce
audible distortion regardless of the frequency or
level of the input signal.
It utilizes three small drivers instead of
one larger unit for greater power-to-weight ratio
and better diaphragm control. The 8-inch drivers
in the 2WQ are slot-loaded to linearize pressure
on the front and rear of the cones and to mechanically
filter side-band distortion.
The cabinet is constructed using constrained-
layer lamination techniques and crossbracing,
resulting in the most inert, resonance-free
subwoofer enclosure that I’ve ever seen.
It has adjustable Q. You can adjust the output
response curve of the 2WQ to suit room
acoustics and placement.
No other commercial subwoofer offers all
these features and virtually all high-quality competitors
cost more.
The 2WQ Operates Primarily Below System
Resonance
Conventional subwoofers operate above
system resonance. They exhibit uneven response
and lots of phase shift as they pass through the
fundamental system resonance which typically
Page 21 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
occurs at the lower end of the pass band.
Designers try to get the resonance frequency low
because output falls off steeply below this frequency.
A vented design with a B4 alignment falls
at 24dB per octave and a sealed design with a Q
of .7 falls at 12dB per octave below resonance.
Take a look at the illustrations in the previous article
to see what happens to phase.
A driver mounted in a sealed enclosure
with a Qtc (total system Q) of .5 will have an
amplitude response curve that falls in a linear
fashion at about 8dB per octave below system resonance
with limited and linear phase shift. Output
will theoretically extend down to DC without the
sudden drop-off and phase shift that occurs when
conventional systems pass through resonance.
This predictable and linear frequency and phase
response is easily compensated for with electronic
correction in the amplifier to produce ruler-flat
output to subsonic frequencies.
Since output is more linear below system
resonance and flat response can be achieved with
amplifier compensation, why not design a subwoofer
that operates below resonance rather than
above it? That’s just what Vandersteen has done.
The result is a subwoofer with virtually no
resonance in the pass band, minimum group delay,
linear phase response, flat amplitude response to
subsonic frequencies, critical damping and a low
system Q making it suitable for corner placement.
A Better Blend with the Main Speakers
The Vandersteen 2WQ subwoofer is integrated
with the main speakers using a unique system
that is not a crossover in the usual sense.
Transitions between the subwoofer and the main
speakers are made with gentle 6dB per octave
slopes using phase- and transient-perfect firstorder
filters that are completely transparent.
Page 22 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
This illustration shows the amplitude and phase characteristics of a sealed enclosure subwoofer with a Qtc of 0.5,
at frequencies below system resonance which, in this example, is 40Hz.
A passive, first-order filter is inserted at
the input to the main amplifier. This filter causes
the signal to the main amplifier and speakers to
roll-off at 6dB per octave below 80Hz.
A 300 watt subwoofer amplifier, designed
specifically to deliver high current into the low
impedance load of the three drive elements, samples
the signal at the output of the main amplifier
and compensates for the roll-off to produce flat
output from the subwoofer. The output from the
subwoofer amplifier is tailored to produce firstorder
low-pass response above 80Hz and a rising
response below 80Hz to compensate for the
falling response curve of the filtered input signal
as well as the falling output response of the subwoofer
which is operating primarily below system
resonance.
Output that could exceed the power limits
of the amplifier, or the linear excursion limits of
the drivers, is prevented by dynamically raising
the low frequency cut-off point rather than compressing
the signal. A unique circuit analyzes the
input signal and dynamically alters the feed-forward
error correction characteristics to accomplish
this feat. The 2WQ cannot be driven to produce
audible distortion under any conditions, yet
it never compresses the dynamic range of the signal,
maintaining the natural rhythm and pace of
music regardless of level.
A passive, first-order high-pass filter at the
main amplifier input is completely transparent so
the sound from the main speakers is not negatively
impacted in any way and all the positive bene-
fits listed in the Subwoofers From a High-End
Perspective article can be realized.
Sampling the output from the main ampli-
fier passes along the sonic and electrical characteristics
(particularly propagation delay) of that
amplifier to the subwoofer system for a better
blend between the subwoofer and the main speakers,
even if the main amplifier is a tube or MOSFET
design. This results in superior integration
between the subwoofer(s) and the main speakers.
Less Audible Distortion
In addition to the feed-forward error correction
system and the specially-designed internal
amplifier, the 2WQ uses several other distortion
reducing techniques.
Three 8-inch drivers have the combined
cone area of a single 14-inch unit but three motors
can provide far better control over the lighter,
stiffer cones. Smaller cones produce less sideband
distortion than larger, more flexible cones,
and any distortion that remains will be at higher
frequencies which can be mechanically filtered by
the indirect radiation path.
These three drivers are slot-loaded providing
an indirect radiation path into the room. Slotloading
the front of the drive elements equalizes
the pressure on the front and back of each
diaphragm making resistance to fore and aft
movement more linear.
A driver in a sealed enclosure “sees” a
diminishing volume of air and increasing pressure
within the box as the cone moves inward, and an
increasing volume of air and reduced pressure as
the cone moves outward. Covering the front of the
driver(s) with a plate so that radiation from the
front of the drive elements enters the room
through a slot or slots between this plate and the
enclosure is an attempt to compensate for this
phenomenon.
Slot-loading provides a reduction in distortion
by linearizing cone motion and also acts as a
mechanical low-pass filter to absorb residual distortion
products at higher frequencies. This
mechanical low-pass filter is far more effective
than a steep-slope electrical filter for the reasons
described earlier.
The cabinet is elaborately constructed
using constrained-layer laminates and cross bracing
to completely eliminate panel resonances and
spurious noise. The 2WQ enclosure feels like a
solid block of material. Rapping on any panel is
like banging your knuckles against a rock. Panel
flexing is simply out of the question.
Page 23 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty
Caveats
The Vandersteen 2WQ subwoofer provides
tightly-controlled bass that is “critically damped”
and limited in output level compared to a typical
home theater subwoofer. Two units will be
required in all but the smallest rooms to provide
the THX-recommended output level of 105dB at
35Hz. I recommend using two subwoofers anyway
and 105dB is much too loud for music listening
so I don’t see these as problem areas.
Tightly-controlled bass that is perfect for
music may not satisfy explosion fans who use
their audio systems for both music and home theater.
Vandersteen makes another subwoofer, the
V2W, for these folks. It looks the same but trades
some control and integration for the ability to play
much louder.
Other subwoofers that offer excellent performance
for those with a strong home theater
bias include many of the M&K models and the
Bag End InfraSub. These subwoofers will still
perform well on music and deliver more visceral
output. Don’t use their high-pass filters. Choose a
passive single-pole filter instead.
Best Value
In my opinion, the Vandersteen 2WQ is
the best subwoofer available for reproducing
music regardless of price, and the price is a mere
$1,250 each! If that’s not a bargain, I’m a bad
shopper. I have four 2WQ subwoofers and they’re
not on “long term loan;” I bought them. I want the
best possible performance and I’m willing to pay
for it, but if the product that offers the best sound
quality also costs less, I won’t complain.
Page 24 Audio Perfectionist Journal Issue #2 Copyright © 2000 R. L. Hardesty

Regards and enjoy the music.
Raul.

Dear Tbg: +++++ " I stopped suspending my speakers when I bought the 350 pound per side Duntech Sovereigns. " +++++

I think now you can do it again with your Acapella's !!!!

Regards and enjoy the music.
Raul.