Do you think you need a subwoofer?

I just acquired Cain & Cain IM-Ben fullrange speakers with a pair of matching C&C Bailey subwoofers. The Ben's are still burning in 10 hours a day, out of phase, facing each other.

But, I have been trying to figure out the best way to integrate them. The Bens are 40Hz-31kHz and run without any x-over except to attenuate/high pass the tweeter output. The 6" Fostex FE-168 Sigma fullrange driver rolls off naturally at the low end.

Terry Cain suggests starting with the subwoofers crossed in at 80Hz. As Raul has pointed out, this means that they will probably still produce some sound up to 100Hz. Which got me thinking, this is into the range of stereo reproduction, so my current Paradigm X-30 sub x-over may not be the best tool.

The X-30(like most sub XO's) takes L/R channel input and sums the channels into a mono signal for the subwoofers. This is ok for music below 60Hz(maybe even 80), but above that I don't know. Perhaps it is best to run true L/R stereo signals to the subs instead of summed mono. Though, i don't know how this affects room interactions. Mono LF signals supposedly help cancel some room nodes.

The X-30 also only accepts line-level inputs, while the X-20 uses amp/speaker level inputs. I remember reading somewhere that speaker level inputs are actually better because the subs see the exact signal the mains are from their amplifier.

Regardless, in my case, line level RCA inputs won't work because I run 40 ft. balanced cables from my preamp (S&B TVC) to my 300B SET monoblock amps which have Jensen XLR->SE input transformers. I'd have to buy 4 new line transformers to do this with the X-30. At that cost, it would be easier to simply buy two X-20 speaker levels x-overs.

Any thoughts on this guys? Is stereo subs best in my situation?

The obvious downside of running true stereo subs is cost. I have not been able to find any affordable crossovers that do true stereo output.

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.

Hi Raul,

Believe it or not, I actually picked up a Pass Labs XVR1 crossover for a friend, but had to ship it back to him one day later. So, I never got to use it.

The Pass X-O is built like a 200wpc amp, it must weigh 40-50lbs.

I also did some reading about the Bryston 10b a few nights ago. One just sold here on Audiogon for $500 in under 8 hours.

I was hoping to find a cheap solution, but a good crossover is going to cost money. I guess the results will be worth it. I'll let you guys know how it works out.

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.

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

Regards and enjoy the music.
Raul.

Rauliruegas...It happens that I have a spectrum analyser in my system, and can therefore give sure answers about frequency response.

The Maggie 1.6 low end rolls off rapidly around 40 Hz, which is exactly what Magneplanar says. For most music their low end sounds better than you would expect because it is very smooth, and the planar format means that SPL is quite uniform throughout the room (at least in my room).

My SW systems exhibit flat SPL to 1250 Hz. (And they are flat to 20 Hz). This is when driving them with a full range white noise signal. However, if you drive them with a swept-frequency tone, distortion becomes evident around 400 Hz. So the SPL is there at 1000Hz, but some of it is harmonic distortion.

Advocates of small drivers may find it hard to believe that a 15" driver can do 400 Hz or higher. Actually it is not the size (mass) of the cone that matters, but rather the ratio of the motor power to the cone mass. My 15" driver has a 4" voice coil, and about 20 pounds of magnet, driven by 600 watts, so it is not at all surprising that it can perform well up to 400 Hz. I also have a set of JBL LE15A drivers (used in some of their classic top-of-the-line systems) and they are good for 800Hz (but they won't do much below 30 Hz).

About the 200 to 300 Hz crossover...this is just for certain types of music, most notably theatre organ, but also brass bands and massed choral music. There is no way that three MG1.6 can deliver the impact of six big cones.

4yanx...The integral subwoofer that you describe in the Vandersteens is a very good approach. What you end up with is a four-way system. A passive crossover for a three way system is a tough design job, and a four way would be worse, hence the use of the electronic crossover and separate power amp. Also the inductor and capacitor values that would be needed for a passive SW crossover are large and expensive. Last, but not least, the all-in-one aspect has definite cosmetic benefits.

The only drawback that comes to mind is that the SW enclosure size is probably less than what you could use for a separate SW. When I built a tower system with integral powered SW I used the "isobaric" design (two drivers mounted one behind the other in a short tunnel) so as to cut the enclosure volume requirement in half.

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.

Thanks, Eldartford. Interesting the mention of isobarics. As yoy may know, the Vandy's incorporate two sub drivers in each cabinet (facing each other - actually virtually stacked). These sound great just positioned properly but, when dialed in are fantastic and a wonderful alternative to separates - WAY better than any three-ways I've heard and as good as most two-way/monitor + subs I've heard.

Very interesting topic, Raul. Based on the responses here from you and Eldartford I'll be holding on to my 10t's for quite a while! These are good down to 28Hz, assuming a good supply of current that is. It's funny since this was always the most frequent complaint about these speakers, "the bass is too loose because of those 12 inch woofers". Now, I have spent a good deal of time and effort building DIY tube traps and absorbers to help treat the room responses and I also use the heavy Aerial stands. It seems to me that speaker designers sometimes shy away from really strong low frequencies because this makes them difficult to place in many rooms, with no control of treatments or flexibility as to placement, and get them to sound good quickly, as in the case of demonstrations. I mean, the first thing I have learned about sound and speaker placement is that 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.

I know that many times when I go to concerts, even an all accoustic night with Godsmack, I do here more bass than what I would normally think I should here. Other times I here bands playing in small venues. I always come away thinking that the bass was too prevelant or the overall sound was too bright. But I have come to believe that this thinking on my part is due to my expectations from listening within my own specially treated and tuned environment. Yes, we do need to here these low frequencies when they are present to get the feel of a live performance.

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.

Greetings Raul,

You seem to be the resident subwoofer expert. I own a pair of Avantgarde speakers (110dB/watt sensitve) designed to have 2 small subs per speaker, however, due to cost constraints, I only have one small sub per speaker. With bass heavy or extremely dynamic material, the subs obviously clip and is quite noticeable. I am currently augmenting the subs with a Velodyne HGS-18 Series 2 with very good result. I am thinking of getting another Velodyne HGS-18 (or DD-series) and have a stereo sub set up, retiring the low powered Avantgarde subs in turn. Am I on the right path or should I just buy another pair of the Avantgarde subs instead? Your thoughts please....

Best regards!

Hi Raul,

Thanks for your comments about how to hook up the 2 subs in stereo - it makes sense, just send one channel to each sub (either RCA, XLR, or high level).

However, your response did give me another question...

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). Do you use the built-in crossover in the subs, and run your speaker cables from your subs to your main speakers? Or do you use some other crossover? If you use another external crossover, do you have examples of appopriate products? If the main speaker is a monitor that is -3db at 40hz, is it really necessary to use a crossover?

Thanks,

Todd

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 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.

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

What do you use? Is it the same size, smaller, or larger as the top panel? Details please.
Thank you

Thanks Raul,

I must have missed that part of the thread. Thanks! It does make sense.

You say:
"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"

I am curious to find out what crossover frequency you use and recommend for different types of speakers? ie.
> Large floorstanding speaker -3db at 25hz
> Medium Size monitor speaker -3db at 40hz
> small monitor speaker -3db at 60hz

Just ballparks are fine.

Thanks! and I apologize if there was already iterated on the thread.

Todd

Raul,

No need to respond - I read your system notes and I see that you cross over at 80hz.

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.

Raul,
I'm assuming you mean "plates" which are round weights that are used in conjunction with barbells for conditioning by body builders and folks into the fitness thing.

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 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.

Very interesting discussion. In the past month, my first experience integrating a sub-woofer into my system had some unexpected results. My Edgar Seismic Sub arrived about a month ago, before the Edgarhorn speakers. The Seismic is a 6' tall folded horn driven by a 18" JBL 2440. While waiting for the Edgarhorns, I practiced integrating the sub with my Alon Circes, which are rated flat ~ 20 Hz. Rather than bass reinforcement, the most noticable difference with the sub and Alons was improvement in sense of accoustic space. There were more cues to the physical size of the recording. For example, it was clearer to sense an intimate jazz venue from a symphony hall from a recording studio. The next difference was improvement in the clarity of mid and high frequencies. On the other hand, it was alot of work finding proper balance between sub bass level and overlap with the Circe, especially since there was no low-pass option on the dedicated sub x-over to roll-off the Circe's output level. I ended up using the lowest crossover setting of 30 Hz, and fairly low level. Now, with the Circes replaced by the Edgarhorns, it is completely different. The horns roll off at 80 Hz, and I'm still trying to find the proper x-over point and level and placement. Placement is limited due to the physical size of the horn sub. It is almost, but not all the way, into a corner. Also, the x-over point is much higher and more audible, ~ 70 Hz. The slope is 24 dB/octave, so I may need to go still lower. And still working on level matching, especially since Bruce recommends up to 6dB boost ~ 30Hz. So many variables to lock down. As for proper stereo reproduction, I am not prepared to commit to a second Seismic Sub, since my room size is only 15' x 18'. Anyway, my experience taught me that the benefit of the sub is NOT so much bass reinforcement, as spatial and clarity up higher. Thanks for a good thread.

Skushino, I've seen those Edgar subs at his shop which 15 minutes from my home. The Seismic is about the size of a refrigerator, but does bass in a way that I hve never heard before. Sound just eminates from all directions rather being pushed AT YOU. It can literally charge the room with acoustic waves from the nether regions.

Edgar's Titan/Seismic sub combo is a system that everyone should experience a few times whether you like horns or not. It is one of the most effortless, seamless, presentations of sound likely to be heard. No shouting, or typical "cupped hands" sound associated with most poorly designed horns. Just sound appearing out of space.

Having said that little advertisement for Edgarhorns, I've been having the same problems properly placing my dual Cain & Cain Bailey subwoofers in the proper spot to seamlessly integrate with C&C's six foot IM-Ben horns.

I'm using a Paradigm X-30 subwoofer x-over, which does summed mono outputs. Intial sub x-o point is 80Hz which seems to be a fairly transparent spot, any higher and bass tends to become boomy.

So far, placing both subs just inside the two, 8 foot apart horns overloaded the room. The Baileys are ported on the side, but I have them with the drivers facing forward and ports facing each other. Outside the horns was a little cleaner with seemingly less spl output.

A few months ago, Terry Cain set these exact speakers up in another person's home and he had the Baileys between the IM-Bens just as I have, but he had the subs angled twoards each other. That room was much smaller than mine, but I am going to try variations of that next.

I need a true subwoofer amp, though. The intermediate Denon AV receiver that I'm using to power them seems completely out of it's league, powerwise.

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.

Hi Raul,

I have the passive version of the Baileys, so I need an external crossover and amp(s) to use them with the fullrange Bans.

But, so far I've been really concentrating on getting proper placement for the IM-Bens. These things really put out the full 40Hz range on their own. It is more than enough for the vast majority of people and rooms whe placed right for room gain.

I'm getting a little bit of bass overload due to my room right now. I need to fine tune things and then add the subs in.

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.

Darkmobius - We should start a support group together! My setup originally had the preamp outputs feeding SET amps, and running full range to the satellite speakers. The sub signal was summed mono, with a 4th order low-pass filter. I heard the satellite and sub signals overlapping too much, so now am using a high-pass filter to the satellites. This definitely cleans up the overlap. In the article Raul posted, the author advocates 1st order filters. I may try this in the future, since with horns we are deep into phase and time alignment issues. But then I'm back to freq overlap issues. So, how to find the proper balance?????

scott

Raul,I do think I'd like to try that second sub,since you say I have "nothing to lose".I've seen my sub on the used market,and can get a second one for about 2500 U.S.dollars.Can you lend me the money,to verify that it will be a big enough improvement?I've done a dumb thing,by promising my family a vacation,this summer!Best regards!

Thanks Raul for posting the exerpts from the review of the Vandersteen 2wq for fellow audiogoners; As you know i,m already getting the 2wq and i hope its somehow a poorman version of the velodyne,s you recomended me. I,m really looking forward to meet you on monday at your place. Regards, Carlos

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.

yes most people need subwoofer. ironically it should be removed from the system unlees you can truly identify that your source has low frequency information that requires it. your crossover can act as low pass filter. this takes the strain of your main amp and main woofer.it provides an improvement like you will not beleive.

Skushino - Dave Whiner's ModeCalc shows that I have 2 room modes at 70Hz, 3 at 141Hz, 2 at 211Hz, 3 at 282Hz, and 2 at 353Hz.

Running the IM-Bens w/o the subs is no real problem except when a sustained note(s) hit that 70Hz fundamental mode and it's harmonics(?) 211/282/353. Especially the 282Hz notes, seems like there is a 6+dB jump in output with distortion. Noticable, annoying because everything else is so pure and clean, but not ehough to destroy the music.

So far, I've found that lower Marimba/Xylophone/Vibraphone keys really overload the room because of their sustained resonance and decay. Cello can, but i haven't found any works that have hit that long note yet.

I've been looking at pro sound crossovers(Rane) or even some of the digital crossovers(Behringer, etc.) this last week.

But, the IM-Ben's are designed to run fullrange without any crossover at all on the 6.5" Fostex FE-168 Sigma drivers. The only components used (I think) is an adjustable 12dB/octave high-pass filter for the Fostex T-900A supertweeter >16kHz.

I'm a little leery of introducing any X-O into the mix even though all the room modes fall in teh IM-Bens range.

As for the subs, my inital experiments with both subs added into the mix have been pretty bad. I don't have a dedcated sub amp(s) yet, so I've been trying to use some solid state integrated amps/receiver that I have lying around. One's a Audio Refinement Complete(50wpc) and the other is a Harmon Kardon AVR 20 II (60 wpc).

Needless to say, it sucks - flabby, mushy, unrecognizable bass. The other problem is that the Paradigm X-30 sub x-over that I have is outputting noticable distortion/breakup.

Currently, I have the Bailey's in between the IM-Bens(10 ft. apart) facing directly forward. Terry Cain suggested starting with this position because it provides the most bass energy.But, the subs do seriously the room even at low volume - wall panels start to buzz/rattle and there is some extremely low frequency energy being generated.

I need to try positioning the subs at various angles inwards, then outwards to see whether that reduces some interactions. After that, I'll move them outside the main speakers at various angles to see how that works.

Unfortuantely, I cannot locate the subs in the corners because the living room side that the speakers are on is open and overlooks my dining room below. The rear wall is 5 feet behind the railing.

As Raul has pointed out, dialing the sub/mains intergration in perfectly could take months.

Raul -

***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.***

I will first try placing caps before my amp inputs, for easy changes. I like the idea of permanently locating the filter inside the amp.

***I think there are no rules here other than: test, test and more tests***

My satellites go to ~80Hz. My concern is that a 1st order crossover accomplishes too little for my goals:

1) minimize overlap between sub and sats (only 6dB down at 40Hz and 12dB down at 20Hz!!!)
2) eliminate LF signal from amp, for less distortion

I will test, test, and test. How did you deal with the overlap?

scott

Darkmoebius - Like you, I am on the steep part of the learning curve. Here is an article about sub integration I found interesting:

Getting the bass right

Unlike Terry, the author advocates many reasons for corner placement of subs, to cancel nodes. In any case, you might enjoy the article. Let me know your results if you try placing the subs outside your mains.

scott

Skushino - Fantastic article!!!!!

I didn't get the concepts the first time I read it, but the next morning I went through it again using the Excel Room Mode Calculator spreadsheet with my room measurements and everything made sense.

First of all, I had to re-measure my room because I realized that I was using a false length distance AND I got my room width wrong. I had been using 16'x20'x8', when in reality my room is 15'x23'10"x8'. Length-wise, I hadn't accounted for the distance that the rear wall that extends back over the dining room.

Then, using the Room Mode Spreadsheet, I was able to find the proper 12' mid-length seating position at the 1st & 3rd(71Hz/24Hz) order nulls. Then, position the speakers at the 2nd order 5.75'(47Hz) null. That leaves me with the lone 4th order 94Hz length mode.

Width-wise, sitting dead center of the room puts me at the nulls of the 1st & 3rd (38/113Hz) modes. I can then put the mains and subs exactly on the the 2nd & 4th nulls (75/151Hz) at 2ft & 3.75ft from the side walls. That looks to provide almost complete cancellation of the the width problems.

So, by experimenting with speaker & seating placement< i should be able to do away with most of problem bands except the single 94Hz legth mode. Although, I an sure I can find a way to dampen that one, too.

Unfortunately, I won't get a chance to try any of this out until next Monday because my brother and his wife are visiting with their 2 year old. Everything gets packed away from Natasha's curious fingers.

Screenshoot of my RoomModeCalc ouput.

Unfortunately, in the length mode, the closest my speakers can be to the rear wall is the 2nd order 47Hz null(5.75ft). Which makes sitting at te preferred mid-room 1st & 3rd null (12 ft) serious near field listening six feet from the speakers. That just doesn't work for me.

But, it is possible to sit right in between the 3rd & 4th nulls at 19.75 ft and 20.75 ft. Both the 71Hz and 95Hz modes should be as close to their nulls as possible.

On the other hand, the 24Hz mode will be at it's absolute worst. Since I don't have an amp for my subwoofers yet, and the main IM-Ben's only go to 40Hz, this shouldn't be a problem. When I do have an amp, EQ'ing that mode down should be no problem.

I kind of like that solution because I didn't want to add any crossover into my main fullrange signal outside of it's stock 12dB/octave high pass filter for the super tweeter.

I think this is one of the most important threads on Audiogon for all to read and understand.

I have purchased a Velodyne DD15 (should arrive in about 4 weeks), and when funds allow I will try adding another for true stereo low freq. I'll experiment with crossing over my Dynaudio S1.4s ~80hz and see how that goes.

Questions: What is the difference between high-pass and low-pass? Also - on the DD series, there seems to be a graphic EQ as well as a parametric EQ. The parametric EQ has a Q value that can be modified. Is that parametric EQ something that I would want to fiddle with, or should I be able to accomplish everything with the more simple visual EQ? The velodyne documentation is a little light on describing what the purpose of the parametric EQ is relative to the visual EQ.

Thanks,

Todd

Dear Todd: Congratulations for your choose !!. The high-pass filter is the one that do the crossover for the frecuency range that will handle for the main speakers, example: frecuencies from 80Hz and up; and the low-pass is the filter that send the frecuency range to the sub, example: 80Hz and down.

The parametric EQ allow to perform adjustements with a specific frecuencies, that's it that the filters in a parametric EQ are variable and with a variable Q ( broad band ). In a graphic EQ the frecuencies and the Q are fixed.

Maybe you will have to use both of these EQ. You can know it when you try to do the integration to your system/room.

Regards and enjoy the music.
Raul.

What does it sound like when running strictly a subwoofer or two below 80Hz?

And what should I listen for when adjusting phase?

I finally got a decent amp for my pair of passive subs, a Samson Servo 550 (275wpc). It's a pro/live amp used in clubs/bars/etc.

Anyway, I feed my subs via a Paradigm X-30 active subwoofer crossover with line-level inputs.

I am currently feeding the X-30 directly from my cd player's "fixed" outputs and my monoblock tube amps from it's "variable" outs while rebuilding my passive transformer volume control.

Anyway, last night while playing assorted jazz, classical, and rock I would intermittently turn the volume down on my main speakers to listen strictly to the subs output.

I expected to hear distinct, clear-cut, drum strikes or the clean resonance of standup bass strings, but that isn't what I got. Everything was rather muted in a undefined way. It certainly fleshed things out when mixed in with the mains speakers, but I expected more attack, I guess.

The best description would be a line that an audio reviewer once used - the subs recreate the trailing edge of a note rather than the leading edge. More resonsce and decay than strike.

I've tried varying the x-o frequency from ~60Hz-120Hz.

Does this seem right?

.
Great thread guys; thanks for sharing the great information.
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Rgds,
Larry
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Dear Darkmoebius: What you are hearing is right: "Everything was rather muted in a undefined way. ".

For the low bass reproduction has " means " for our " ears " it has to be working with the midrange sound, other way ( 80Hz and down ) you will heard what you already heard.

Regards and enjoy the music.
Raul.

Thanks for clearing that up Raul, I was just a little worried that I somehow burned up my subwoofer crossover. Everything sounded great when both the subs and main speakers were playing, but when I turned down the mains, the subs sounded muted and out of focus.

Amazing what an influence such a bad sound can have. I thought instruments and voices sounded pretty damn good before, but now after hearing things with the subs, mains-only sounds thin and one dimensional.

The subs added depth and flesh to everything. Amazing because it does so with very little output. It really doesn't take very much volume wise. Although, what little it does, pushes my 275 wpc sub amp to it's limits on organ music and other sustained low frequencies.