Geddes multiple subwoofer method - 3 subs vice 4

Dear @deep_333 ​@phusis  and friends:

Here the mode calculator and other 2 interesting links for almost all of us:

Room Mode Calculator_0.xls (live.com)

Microsoft Word - whitepaper10.doc (harman.com)

Harman How to Listen

R.

Dear @m-db  : " on a used Plus in any size I think you might be amazed. "

hings are that I already had the DD Plus experience not in a home system but with an audio distributor. Rally good.

However the pulp/paper cone of my HGS ones are the ideal for my speaker woofers where the DD driver build material is different with a different bass reproduction signature. Thank's for your advise.

R.

Dear @deep_333 : My room geometry is not easy to use the Harman calculator, these are more or less the dimensions/shapes:

as I posted my apartment has 2 parlors from the entrance door. First parlor where is not seated the system its wall distance to the other extreme, where is the second parlor/listening area/system, are 9.70m to the window that’s behind the speakers.

Now the speakers are at 95cm. in front of the windows and the left speaker is at 30cm. from the side wall, the rigth wall is at 8.5m from the left one.

The center of the speaker tweeters in between are at 2.60m and the speaker woofers at 3.05m.

Listening area length is 4.70m and the wide is around 4.5m. Exist a passageway of 1m. wide by 14+m. in length. This apartment has 3 bedrooms and two complete bathrooms. All in one floor, so is a little big.

Dining room is big and the dining room central/rectangular table is for 10 seated people.

Both parlors are full of ( mainly ) wood furniture as the dining room and all around exist wood display cabinet ( like seven of them ). The parlor furniture are made from natural absorbtion materials and due to the shape of the wood furniture it works as difussors.

Rigth now the system is working truly fine and till today I think that I can’t do ( ? ) anything to improve its very high quality MUSIC reproduction and very high resolution.

It does not matters the SPLs the room/system just refuse to distort: MUSIC stage always is there/nothing change but SPL. Yes, its noise floor and distortions levels are so low that can be dangerous to the ears with out taking in count due that we can’t be aware of those distortion levels. No, I normally listen at around 82 or even a little lower db SPL and only during some kind of system audio items tests I listen at 95db with peacks at 105+db for only a few minutes.

R.

Dear @phusis  : " I don't buy into the music vs. HT subs distinction. "

Agree, my mistake.

" while I myself opt for horn-based subs.... "

In general I like the immediacy of the MUSIC reproduced sound that's a main live MUSIC characteristic. One " but " on horns ( at least to me ) is that I don't like its reproduced sound seated at near field position ( say 2m. ) I think we need at least no less than 3m. and obviously that depends of the room too. At near field position my ADS are way better than horns or electrostatics.

Unfortunatelly  I never had the opportunity to listen a true horn subwoofer ( at least that goes to 16hz. ) but I tend to beleive you.

R.

Another advantage in my sub/speaker is that the sub driver is of pulp/paper cone as are the ADS speaker woofers drivers, so exist synergy in the sound reproduction.

R.

Dear @deep_333 : I really appreciated your post and you can be sure that I will do all those.

Tou touched a critical issue in the subs correct integration to the room/speakers: PHASE that almost no one really speaks about when are talking of subs and " playing "/changing with comes with very high rewards that for me were unexpected to say the least.

By coincidence and before read your post last nigth I was " playing " with subs Phase making some changes ( btw, we modified the phase control in the HGS to go from only two phase positions to almost continuous changes. My HGS have several modifications made it by a friend and me: I changed the stock internal wiring from the drivers to the amp for pure silver KK cable, I by-passed all the internal fuses and changes passive and active parts in the input board and internal crossover circuit board. Even I change the damping foam by long hair virgen wool. The subs are at around 20 cm. from the floor and have a dead weigth of 30kg at the top plate. ) and I did it using CD MUSIC source as " Day after Tomorrow " that at its very first track comes with deep bass made/using synthesisers and I use other film soundtracks as Gladiator and the like and late in the nigth I gone to sleep but not totally satisfied.

So, I wake up early today and followed playing with phase changes this time doing with LPs mainly using the Telarc 1812 that has a wide kind of different bass frequency ranges and recorded with acoustic instruments and not synthesiser that’s different and after the changes with the phase finally I was truly satisfied with and learned the critical importance of PHASE about.

Thank’s for your knowledge advise. I’m just learning what it’s exiciting to me in that critical sub/speaker subject. Thank’s again.

R.

Dear @deep_333  : I agree with you in everything and specially in " I am only concerned about my main listening position. ".

My 2 subs are rigth at the front stage side looking each to other: the drivers sound reproduction  does not goes " direct " to me as the sound from the main speas.kers.

My room is an inverted L with two parlors ( first smaller one ) in the second and main parlor is where the speakers/subs are seated in front of my listening position. Exist a left side wall behid de left sub but the rigth side sub has not a direct wall because there is is the dining room a big one with wood furniu.ture.

Through several months maybe over 1 year I tested every imagined subs positions and was exactly where are seated today what works in that room/system. 

Even that I can be seated at 4m. from the speakers my prefered and day by day listening sessions are at 2.5m ( around ).

R.

Dear @deep_333 : " " Not true...depends on what you get...I use 8 of the acoustic fields ACDA panels ....clean down to 30hz. ""

Problem with room treatment and especially in the bass range because its main importance is that " clean down to 30hz ". First question could be at which frequency starts to " clean " and if exist in room measurements of frequwency response with and with out those kind of panels. Always is important not only what we are avoiding with but what we are losting with, obviously always exist trade offs and depends of each one of us what kind of trade off we are ready to take. Other alternative is something as the C20 electronic bass trap that operates between 15hz to 150hz :

AVAA C20 - Active Bass Trap - PSI Audio

I don’t have a dedicated room/system and when I had professional room treatments ( several kind of through the years. ) I really never been totally satisfied with. At random with the stuff in my parlor as wool carpets and the kind of the parlor furniture and treatment diffusors and curtains and mainly to the subs position I’m lucy enough to stay really satisfied as ever with no apparent troubles in all the room/system frequency range quality level reproduction at diffrent S¨PLs and different kind of MUSIC.

In the other side and about the ported loudspeaker still today is what almost all top manufacturers use it and the customers jut buy because there are not to many sealed/acoustic suspension speaker alternatives. Even Wilson uses ported.

For subwoofers I totally agree: must be sealed not ported.

R.

@phusis :  " Looking at the CEA-2010 maximum peak output of the DD18+ puts it in the upper middle range of all subwoofers ever tested and near the top of all sealed subwoofers. It produces output easily in excess of 110dB over the critical music range and offers impressive deep bass output as well mustering over 103dB at 20Hz and almost 99dB at 16Hz which is impressive for a sealed subwoofer. The DD18+ CEA-2010 output is amplifier limited above 20Hz and was distortion limited at and below that point. The DD18+ is the first commercial subwoofer that I have ever evaluated that was able to produce a CEA-2010 passing result at 10Hz. 86.1dB may not seem like much but any passing result at the 10 and 12.5Hz bands denotes rather prodigious deep bass output capabilities due to the amount of displacement involved to produce any meaningful output that low in frequency, not to mention that distortion must be under some amount of control as well. If distortion is ignored completely the DD18+ can almost muster 90dB at 10Hz. "

R.

Dear @phusis : Velodyne ( at least my HGS, not the DD models with Kevlar driver. ) were made for MUSIC sound reproduction systems and not HT where needs are different and especially on SPL.

The Velodyne aceleromete/servo ( patented. ) avoid that THD can goes over 0.5% and when it’s approaching that figure power gone lower but not the bass frequency.

I never had a problem with my HGS and maybe because my main speakers has 95db efficiency but I measured at my seat position ( near field. ) 97db SPL with peacks at around 105db and the bass range is fabolous.

I readed other reviews on the DD models where what you read it did not happens but at the ned the critical subject is to mantain ( for listen MUSIC not HT. ) the THD at minimum in the bass frequency range. This is the why of my post more than about thisor that sub.

In your link review we can read this ( HT ):

" 

Batman Begins followed by the Dark Knight, both of which offer not only a very powerful and engaging audio track but also are enjoyable movies to watch. The master volume was set to -15 for the entirety of both films.

Throughout the various action and dramatic sequences of the films the DD18+ provided a stellar performance. Subtle background bass undertones were just that and when demanded the DD18+ provided a lot of power and room shake. On sections that contained deeply extended bass the DD18+ had generous extension that provided an extra feel or size to the sound that lesser subwoofers simply do not. As previously discussed the performance of the DD18+ as far as definition and ability to track notes is excellent. If there was any small caveat to the DD18+ performance it might be that it was not quite as sharply dynamic on a few parts as I recall they can be, the tumbler chase scene being one example, the gatling gun test, bankers shotgun blasts and the hospital explosion being others. My large listening room acoustics are such that it is very difficult for a single subwoofer, even a very capable and powerful one such as the DD18+, to handle alone so perhaps the DD18+ was being limited a little on a few extremely loud sections. Audio memory is a hazy thing at best so I can’t be sure and to be quite honest I’m stretching to find even that small caveat with the DD18+’s audible signature. It is that good. What I can be sure of is that the DD18+ always sounded composed throughout and easily produced one of the top performances that I have experienced from a single subwoofer in my room. Very deep bass was presented with apparent ease and fundamental tones or pitches of bass transients were spot on.  "

Not so bad as those measurements and the reviewer seats one DD-18 at 4 meters from his seat position, not near field.

R.

Dear @james633  : Mainly I'm talking of MUSIC home/system reproduction where the whole frequency range belongs/"lives" through the bass range. As better the bass range in any audio system as better the whole quality MUSIC reproduction levels.

That's why THD in the bass range is just so critical due that high THD levels as the JTR ( that are for HT not MUSIC: ) subs afects all the whole MUSIC frequency range system due that the different bass frequency ranges develops harmonics that has direct influence in the midrange and from here to the HF range.

You are fine with that 5%-10% on THD and no problem with me, it's only that's way to high in frony/against the 0.5% at 120 db in the Velodyne.

We can have a perfect room/system sub blend with a " marvelous " frequency chart but the main issue down there is not that perfect blend but the developed THD level by the subs inside the subs system range at seat position. That's all, it's not about to subs it's about MUSIC reproduction quality level.

Just my way of thinking,

R.

Dear friends: For me exist a critical issue to use DSP for the  high-pass filtering and blend the subs to the mains.

The question is for each one of us way of listening MUSIC. I own thousands of LP's and only hundreds of CD and I really don't care about streaming even that today digital in many ways surpass the analog alternative but due that I listen mainly to LPs I can't contaminates the overall analog signal doing it that pass through a digital domain .

Apples can't mix with oranges at least for me. Main difference between analog and digital and where digital outperforms analog is in the bass range but even that I know that I prefer to stay all the way down to analog but as I said: this is me and only an opinion.

R.

Dear @james633 : " I don’t see anyone using JTR stuff for music.."

Well the main reason is that JTR subs are designed for HT in specific and not for MUSIC systems.

In HT THD is not to important and even that the enty level RS1 measured more or less " fine " its THD goes to high but your JL are not way better in that regards and certainly not only in the RS1 price range but with out the " impact " in the low bass that has the RS1.

Btw, it looks a lot to the Velodyne 18"/15" that are higher in price but more important is that Velodyne's THD goes at 0.5% thank's that the design checks in real time over 16K times each second the woofer excursions.

In the other side:  " I would like to try 4 at some point.."

Of course you can but at one specific seat position we need only 2 subwoofers and Harman showed 30+ years ago why even that in its study said the optimal are 4 for the " room space " not one and only seat position as with dedicated MUSIC system .

R.

Dear @lonemountain  :  I don't know if you know the Harman Subwoofer White Papers that are a scientific modeling used to avoid standing waves and those null points, it's truly extensive and here Harman Inernational ( JBL between other audio items. ) conclusions:

" 74 CONCLUSIONS • How many subwoofers are enough? Four subwoofers are enough to get  the best results of any configuration tried. Two subwoofers is very nearly tried. Two subwoofers is very nearly as good and has very good low as good and has very good low frequency support as well "

That's at room/system seat position.

Top speaker manufacturers with passive designs use the passive crossover ( high-pass, band-pass, low-pass and the like ) to blend " perfectly those speaker used drivers and not only the crossover but time alignment and several other issues.

There are several ways to implement the high-pass filter when using a pair of self powered true subwoofers with out " problem ".

In my case ( audo system ) the high-pass was implemented at ampifiers input doing only a change in the input value capacitor that comes/came by amplifier design and blended almost " perfectly " using the subwoofers own low-pass filters , phase and volume. 

Never is an easy task to blend the mains with subs but it can do with a little of patience . Btw, my subs are ( acoustic suspension. No ported/reflex. ) positioned in front of the main speakers and facing each to the other not looking to the seat position as the main speakers but side to side ( I don't know how to explain it. ).

R.

Dear @audioquest4life :  ​​​@erik_squires is rigth even with bigger speakers than monitors smaller ones and I disagree with Geddes.

In the other side you are doing nothing new and nothing as what Geddes says because you are talking of what speaker manufacturers do: midrange, mid bass and bass no matters wich kind of drivers they use in their speaker designs ( field coil or not ). It depends what the manufacturer is looking for and at which market price he wants to offer.

R.

R.