One or two subs?

[Bigmoney]

Hey guys I decided on adding a subwoofer to my bandw 602's. I have always heard two subwoofers placed symmetrically in a room are far superior to one subwoofer. While on a budget, my question is whether buying two inexpensive subwoofers and placing them symetrically will sound better than buying one more expensive subwoofer by itself. I know with two subs I can better integrate the subs seamlessly to my stereo configuration.

[blackraven]

Buy one good sub! One good sub will be better than 2 mediocre subs. I've heard 2 sub systems for music and I have not been impressed with the results. Most people with subs tend to have them adjusted wrong with way too much bass. For music, you should not be able to tell a sub is present, it should play seemlessly into the music.

Save your money and buy a very good sub, or just put the $600 plus on better speakers.

[Bigmoney]

Ok. As always I have a few more questions, but only because I trust your advice. A complement to you. I guess I should go with one sub and I can always match that sub with another in the future when I have saved up some more green. In the mean time I am looking for a sub with a high quality low pass and high pass filter so that I can no longer run my mains full range and have the sub pick up the harder bass frequencies. Considering my mains, 602's, are good till around 42 hz -6db I figure It would be best to relieve them right around 55-60 hz. I think I will have around 600 to spend on a sub, which I wil probably do used and cross my fingers. I think used audio is a great value as long as you are willing to sacrifice a few blemishes. I hope by going used I can get a sub that was atleast a 1,000 new because it is widely published on this site the importance of a good sub. Unless you have strong reccomendations for new subs ni the 600 and less range.
The sub I get is intended for two channel playback only, while I am not sure such a sub exists, my main concern is the musicality, tightness, and quality of crossover. Thereby, I am seeking a sub that would perform more hifi than hometheater.
Thanks again, as always, you all have been a big help :thumbsup:

[kexodusc]

I'd second blackraven's comment - get 1 good sub. You'll benefit the most from the improved performance of that one sub over 2 mediocre ones.

Adding a second sub will do two things:
1) Add 3 dB to the volume (not terribly noticeable) which will reduce the strain on the first sub - long story short, both subs should perform a bit better. But probably not as good as a lone, superior quality sub will perform. A single better sub probably plays louder any way.
2) The 2nd sub can alleviate some room induced peaks and nulls in the room response, but not necessarily. That's adding a whole other layer of acoustic complexity to your system, and it's just as likely to make things sound worse if you're not sure what you're doing.

So a good quality single sub is usually an easier, more efficient path to better sound. Guess it depends on "how much better" the better sub is though.

I still recommend people take a look at the Dayton 15" Titanic sub:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=300-764

I built the 12" version of the above for my parents - and it easily outperformed $800-$1200 subs I owned by HSU and Paradigm. So much so that I decided to sell mine and build one for myself. Far better sound quality for music performance (sealed cabinet!). The 15" is even better.

For a smaller profile where absolute loudness isn't the biggest concern, I would recommend
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=300-742

These are major league quality subs, and the Reference driver is a favorite in the DIY world when sound quality is the primary goal. Awesome value and I haven't heard anything commercial for even twice the price that approchse the performance. I'm skeptical you could find something as good used, but deals do pop up from time to time.

I do like ACI and REL subs as well if you decide to look to the used market, and of course HSU and SVS continue to be popular home theater choices.

[E-Stat]

While on a budget, my question is whether buying two inexpensive subwoofers and placing them symetrically will sound better than buying one more expensive subwoofer by itself.
I'll offer the dissenting opinion. If I were supplementing an otherwise full range speaker with good bass response, I might choose a single one for supplementing the bottom octave only. According to a test by Joe D'Appolito, however, the -3 db point of the 602s is a fairly high 48 hz. While reasonable for a 7" woofer, you need the subs to handle more of the range.

I went the dual route for my HT system and effectively made three-way speakers out of my Polks. After measuring the room and using an inexpensive EQ (subs only), I get very smooth response and increase the headroom of the mains using a 120 hz high pass. While my subs may not fathom the very bottom, what is there blends well with the mains and is neutral.

rw

[blackraven]

The subs that KEX. Recommneded are all good subs. Here's a few other subs to look at.

For a brand new sub, consider the Martin Loogan 10" dynamo for $600. Its non ported and very "fast" with no boomy bass. Its made to keep up with Electrostats. I find it very musical with no boominess or muddiness. I think its a real bargain at $600 for 2ch music and it sounds better than many subs costing hundreds more. Its high on my list when I decide to replace my old cheap velodyne. You can get a new REL for about $6-800 at www.sumikoaudio.net. Also consider used Velodyne SPL and Digital Drive Series subs. They are also non ported and musical and come with remote controls for adjusting them which is a nice feature. They are also servo controlled. I was on audiogon yesturday and there were a number of B&W subs for sale as well. Some of their subs are excellent.

[Feanor]

Hey guys I decided on adding a subwoofer to my bandw 602's. I have always heard two subwoofers placed symmetrically in a room are far superior to one subwoofer. While on a budget, my question is whether buying two inexpensive subwoofers and placing them symetrically will sound better than buying one more expensive subwoofer by itself. I know with two subs I can better integrate the subs seamlessly to my stereo configuration.

I once heard two subs recommended -- despite the fact that bass under 80Hz is non-directional -- because the two subs can reveal "out of phase" information. I don't know the veractiy of this theory.

I take "out of phase" in this context to mean sound recorded out of phase as between the left and right channels. Whether or not there is out-of-phase info would very much depend on the recording process and I doubt that it would be present in the majority of records. It would also depend on the usual sub considerations such as room placement.

[E-Stat]

I once heard two subs recommended -- despite the fact that bass under 80Hz is non-directional -- because the two subs can reveal "out of phase" information. I don't know the veractiy of this theory.
I don't think it has anything to do with phase. I believe the issue is that most woofers (and certainly ones that would blend with his satellites) would be operating well above 80 hz. My 12" subs respond up to about 200 hz without filtering.

rw

[Sir Terrence the Terrible]

I'd second blackraven's comment - get 1 good sub. You'll benefit the most from the improved performance of that one sub over 2 mediocre ones.

I absolutely agree with this.


Adding a second sub will do two things:
1) Add 3 dB to the volume (not terribly noticeable) which will reduce the strain on the first sub - long story short, both subs should perform a bit better. But probably not as good as a lone, superior quality sub will perform. A single better sub probably plays louder any way.

This has a huge caveat. It all depends on the placement. Two subs placed in the corners of the width of the room will cancel the first and third order modes. That leaves only the second order mode to deal with. I got a healthy 9db increase in output from my two subs in those corners without even increasing the volume on the pre-amp. You will not get this kind of extra output from a single sub no matter where you place it.



2) The 2nd sub can alleviate some room induced peaks and nulls in the room response, but not necessarily. That's adding a whole other layer of acoustic complexity to your system, and it's just as likely to make things sound worse if you're not sure what you're doing.

The second sub will most definately cancel the first and third order modes. Especially when placed in the two front corners of the room. It will also smoothen the response for more than one listening seat as well. Two are not any more complex to hook up than one. Just use a y-connector from the recevier to the(hopefully equalizer you gonna need it) seperate subs, and you are good to go.

Just my three pesos

[Sir Terrence the Terrible]

I once heard two subs recommended -- despite the fact that bass under 80Hz is non-directional -- because the two subs can reveal "out of phase" information. I don't know the veractiy of this theory.

I take "out of phase" in this context to me sound recorded out of phase as between the left and right channels. Whether or not there is out-of-phase info would very much depend on the recording process and I doubt that it would be present in the majority of records. It would also depend on the usual sub considerations such as room placement.

The out of phase information between the left and the right channels does not become useful until way above the subwoofers range. Within a subs range the wavelengths are so long, that any timing differences that would represent any stereo difference information would be completely zeroed out. Most recordings(especially vinyl) usually mono the bass anyway. Live recordings usually pick up the leading bass transients(which are components of higher frequency information), and the associated room bloom usually just perceived as mono information as well.

[kexodusc]

I
This has a huge caveat. It all depends on the placement. Two subs placed in the corners of the width of the room will cancel the first and third order modes. That leaves only the second order mode to deal with. I got a healthy 9db increase in output from my two subs in those corners without even increasing the volume on the pre-amp. You will not get this kind of extra output from a single sub no matter where you place it.

Sir T, I humbly defer to your experience in this area.

I can only speak from my own experience of two subs with corner placement - I didn't get anywhere near 9 dB extra and the in room response. If memory serves around 5 dB, I would have to check. Moving even a foot or so from the corners would diminish the gain rapidly.
Also, I noticed larger peaks at a few frequencies, but the "dips" were alleviated. Net effect being a smoother response overall, but trading one set of problems for another. The nice thing for me is the BFD could kill the peaks, I couldn't do much about the dips before. I have noticed that it is much easier to tell when the 2 subs are out of phase with the main speakers near the crossover region though and this was the complexity of which I speak. Integrating well took a lot longer (or maybe I was fussier?). But overall I'm much more satisfied.

May I ask, why does THX recommend placing the subs across from each other near the center of the walls as opposed to the corners?

[flippo]

The Infinity Kappa perfect 12 VQ is also an excellent driver for a diy sub.

[Bigmoney]

E- Stat: Are you mention that you have your sub accounting for the frequencies above 80 hz and I assume unfiltered, therefore you blend your sub without using a crossover by essentially let the sub fill in the gaps where the speakers roll and let the speakers handle the rest? Hope that made sense. Or I assume you have a high crossover. By the way, which equalizer do you use in your room.

I have a sub I am happy with and heres the link http://www.crystalaudiovideo.com/product.aspx
It was 650 dollars new, but only has an LFE input, no crossover and limited function. Seems like a quality woofer, I brought it to my dealer and even he said it was accurate, low distortion, andfairly well controlled. By far not the best sub, but worth keeping. I have refrained from using it for two reasons. With only and LFE input I assume the sub was made primarily for HT use and not HIFI. After all its maker, crystal acoustics is primarily a HT speaker company. The other being with no crossover, my purpose for using the sub would be defeated. I want a sub which can fill in for my mains via low pass filter and take some stress off of them via high pass filter.

I had considered keeping the sub, because I think it was blackraven who told me of an inexpensive crossover. The unit was the behringer SUPER-X PRO CX2310. I checked it out and decided against it for two reasons even though it was an affordable 100 dollars. The unit has a DJ style look which has no place in my hifi room, and because I was afraid that the crossover to my preamp would distor the signal to my mains. Unfortunately to my knowledge most other stand alone crossover units are very exepensive:frown5: .

As for DIY, I am seventeen and in all honesty am afraid I would mess it up. So DIY is not my best choice, but for those capable, has to be cost effective.

With a dedicated listening room I have the luxury of placing the sub anywhere in the room so if you think two subs are substantially better if place well, than I have the room to work with.

One more question for E Stat. You talked about the frequency response being very smooth in your room, do you have bass traps as I am strongly considering building some of those you mentioned in my last thread? Would you consider properly placed and constructed traps as or more important to the frequency response than the quality or lack of a sub?

[filecat13]

Well, I'll take the dissenting opinion to the extreme. Forget two subs in the corners and put four subs at the midpoints of each wall. Of course, putting four piece of crap subs in a room won't help.

http://www.harman.com/wp/pdf/multsubs.pdf

Still, I'll go along with the notion that one very good sub is better than two so-so subs.

[Feanor]

Well, I'll take the dissenting opinion to the extreme. Forget two subs in the corners and put four subs at the midpoints of each wall. Of course, putting four piece of crap subs in a room won't help.

http://www.harman.com/wp/pdf/multsubs.pdf

Still, I'll go along with the notion that one very good sub is better than two so-so subs.

Harmon studies are always interesting. And it's interesting that they consider four subs the practical optimum, and two sub good especially when place mid-front and mid-rear.

[E-Stat]

E- Stat: Are you mention that you have your sub accounting for the frequencies above 80 hz and I assume unfiltered, therefore you blend your sub without using a crossover by essentially let the sub fill in the gaps where the speakers roll and let the speakers handle the rest? Hope that made sense. Or I assume you have a high crossover. By the way, which equalizer do you use in your room.
No, I high pass the mains and low pass the subs. My point is that even when low passed, there is typically content found an octave higher unless you use an extreme slope. I experimented greatly with different combinations. I began with the notion of running the Polk satellites pretty much full range and attempted to blend. In my room, that didn't work. What I found was that I needed the EQ to handle the room modes. In order to do that, I had to run the subs higher (EQ on subs only!). So, the Polks nominally high pass at 120 hz and the subs low pass around 100 hz. Measured response is reasonably flat and I get more headroom from the mains because they were really not happy delivering 50 hz.


One more question for E Stat. You talked about the frequency response being very smooth in your room, do you have bass traps as I am strongly considering building some of those you mentioned in my last thread? Would you consider properly placed and constructed traps as or more important to the frequency response than the quality or lack of a sub?
I'm a big fan of bass traps, but alas can only use them upstairs in the two channel music system. In the den downstairs, I use EQ on the subs instead. More important than the quality of sub? Perhaps. I value linear response higher than eking out the last hertz or two at the bottom. I find that getting the upper bass/lower midrange really right is critical for neutral system response.

rw

[E-Stat]

Well, I'll take the dissenting opinion to the extreme. Forget two subs in the corners and put four subs at the midpoints of each wall. Of course, putting four piece of crap subs in a room won't help.
I've never found good results with corner placement. Mine are well away from the side and back walls. As for multiples, Duke over at AA has a array of subs he calls "The Swarm" which is said to work very well with Maggies and other planars.

rw

[Sir Terrence the Terrible]

Well, I'll take the dissenting opinion to the extreme. Forget two subs in the corners and put four subs at the midpoints of each wall. Of course, putting four piece of crap subs in a room won't help.

http://www.harman.com/wp/pdf/multsubs.pdf

Still, I'll go along with the notion that one very good sub is better than two so-so subs.

I just shake my head everytime somebody uses Todd Welti white papers to offset Floyed Tools. Todd Welti's paper address smooth response only, not low frequency support, not keeping distortion down, and not maximizing subwoofer perfornamce.

Floyd Tools papers address performance, low distortion, and low frequency support, and supports the use of electronic EQ to smoothen the frequency response. His way keeps distortion down, because as I have stated before, each wall the sub "see's" adds 3db amplitude without increasing the amps at the sub. Corner supports provides a free boost to the deepest frequencies, which mean less cone excursion at higher levels.

If you look at the frequency plots of Todd Welti placements, they all fall off rapidly below 40hz or so. Gene LaSalle of Audioholics got the same result with this placement in his room. Unless the subwoofers are extremely large(18"), this placement is not optimum for overall subwoofer performance

[Bigmoney]

I imagine your polks must sound a lot cleaner and detailed having been relieved of the lower frequencies, and also your amp must function more efficiently further benefitting the sound. Anyone hear the microvee from velodyne, small compact sub. I heard it at my dealer and thought it was accurate and musical. I am surprised to not hear more about velodyne in this thread or even in the forums. I thought velodyne to be the top manufacturer. I wonder, like anything, if there products are overpriced due to the prestige of the name and reputation velodyne has built for itself, like monster but on a much much smaller scale. A better comparison may be b and w which I have heard to be marked up a tad given the name.

[blackraven]

I havent heard it but its Freq response is 38-120Hz. There are better subs out there for the money. If you want a small sub from velodyne, consider the Minivee instead, 28-120Hz. These are very musical subs and quote-fast subs due to their non-ported designs. The minivee is basically an 8" SPL sub without the equilizer and remote control.
I'd rather go with the Martin Logan Dynamo over the minivee. Its also a sealed 10"sub and very musical.

[blackraven]

FYI, there are some ML dynamo subs on audiogon for under $500 now. Also look at the ML Grotto which is servo controlled and has excellent sound.

[Bigmoney]

May I ask three questions:

What is a servo controled sub?
What is the difference between a down firing and front firing sub in the characteristics of the sound they produce respectively? I would imagine they would have different sound characteristics gien their different design.
Lastly, can you reccomend a affordable EQ for a sub?

[blackraven]

A servo controlled sub uses a feedback to monitor and control the movement of the woofer and limit unwanted movement there by lowering distortion. Servo control is used on many more expensive subs.

http://en.wikipedia.org/wiki/Subwoofer

[emaidel]

I'm perfectly satisfied with the performance of my one subwoofer, but even in the literature for it, Definitive Technology suggests that two would be better.

Back in the 70's, when Dahlquist introduced its DQ-1W sub, the salespeople in the company recommended two subs, as opposed to one. I asked one of them why, and i've never forgotten the "audiophile-speak" response:

"With one sub you get better dynamic impact, but with two there's greater spatial dimensionality."

Uh, oh, I guess so. Still, considering the size of the DQ-10's, and that of the DQ-1W, I wonder how many people had listening rooms big enough to accomodate both the 10's and two of the subs.

[E-Stat]

Lastly, can you reccomend a affordable EQ for a sub?
I went really cheap with this Behringer model. Works great on a sub, but don't run it full range!

http://behringer.de//FBQ3102/FBQ3102_big.jpg

I use only the bottom three octaves.

rw

[Mash]

You connect a mic to the sub, place the mic where you will listen, and press EQ on the sub's remote. The sub then emits a sequence of 10 frequency sweeps. The mic measures the sweep's response where you sit and the sub then corrects the output levels for the next sweep. I have one of these subs in our kitchen. It keeps the fresh salmon jumping.

The servo feedback feature cancels out amplifier and speaker cone distortion by correcting the sub's final output to match the sub amp's input signal in real time. This is the same feature that is used on the Mackie HR824Mk2 speakers.

If you should ever use loudspeakers like Magnepans, a servosub is a must. A non-servo sub will usually sound rather 'soft' next to the Maggies.

[Bigmoney]

Mash.... If I understood you correctly the velodynes will self correct themselves for a flat frequency response. Thats amazing. Can only imagine what those subs cost. What are the cheapest velodynes with that function and is it as effective, or more effective than hooking up and separate eq such as the one suggested by e stat and adjusting manually?

[blackraven]

The velodyne SPL series comes with the automatic 6 band equalizer and sells for about $800 to $1500 depending upon the size of the sub. The more expensive Digital Drive subs with the servo control and 8 band equalizer are over $1800.

[Mash]

Bigmoney, I always preferred the 15" Velodynes as being the best choice for a home sound system. The usual difference between the 18" and 15" Velodynes was the 18" driver and a larger box. The units smaller than 15" did not ever seem to cut the mustard.

An yes, you are correct that "...the Velodynes with EQ will self-correct themselves for a flat frequency response."

Audio Advisor was selling the 15" SPL for $1000 a while back. This was about $200 below the next best price. The 15" servo-controlled DD will likely cost about $2000. The servo-controlled sub will be more distinct when reproducing a (struck) bass drum, string bass, and other instruments with sharp attacks. A pipe organ will sound about the same on either the servo-controlled DD or the non-servo SPL, since pipe organs generate sound using resonating air columns in pipes, i.e. their sound issues as sine waves.

The servo feature will shine with speakers such as Maggies and the Mackie HR824.

[Sir Terrence the Terrible]

You connect a mic to the sub, place the mic where you will listen, and press EQ on the sub's remote. The sub then emits a sequence of 10 frequency sweeps. The mic measures the sweep's response where you sit and the sub then corrects the output levels for the next sweep. I have one of these subs in our kitchen. It keeps the fresh salmon jumping.

The servo feedback feature cancels out amplifier and speaker cone distortion by correcting the sub's final output to match the sub amp's input signal in real time. This is the same feature that is used on the Mackie HR824Mk2 speakers.

If you should ever use loudspeakers like Magnepans, a servosub is a must. A non-servo sub will usually sound rather 'soft' next to the Maggies.

Non servo's also sound soft and less impactful with horn loaded speakers as well(really just my opinion). I know when I got the servo option added to my subs, it really drastically changed the low end response. No overhang, super quick transient response, and the sucker could play about 6db louder than before the servo's were added with far less distortion to boot.

The problem I have with auto setup/equalizing circuitry lays with the fact they do not take into account early first reflections rather loud amplitude, and the lower level late arriving reflections. Audyssey auto setup/EQ is the only one that takes into consideration the reflection "pattern", not just the loudest modes in the room. With most other setup and EQ routines, you get in the ballpark, but no homerun. I can go back and still find issues with a good old fashion lab grade microphone and a RTA at 1/6, 1/10, and 1/20th resolutions. The audyssey is pretty much on the mark, and only requires very little tweaking when its all done.

[Sir Terrence the Terrible]

Sir T, I humbly defer to your experience in this area.

I can only speak from my own experience of two subs with corner placement - I didn't get anywhere near 9 dB extra and the in room response. If memory serves around 5 dB, I would have to check. Moving even a foot or so from the corners would diminish the gain rapidly.
Also, I noticed larger peaks at a few frequencies, but the "dips" were alleviated. Net effect being a smoother response overall, but trading one set of problems for another. The nice thing for me is the BFD could kill the peaks, I couldn't do much about the dips before. I have noticed that it is much easier to tell when the 2 subs are out of phase with the main speakers near the crossover region though and this was the complexity of which I speak. Integrating well took a lot longer (or maybe I was fussier?). But overall I'm much more satisfied.

May I ask, why does THX recommend placing the subs across from each other near the center of the walls as opposed to the corners?

Kex,
The earlier THX certified subs had a low frequency cutoff at about 35hz, and relied on corner placement and room gain to extend the response down to 20hz. It used the rapid roll off of the ported systems in combination with the low frequency support that corner placement gave you to keep distortion and excessive cone motion and overloading to a minimum.

Subwoofers certified as THX ultra 2 are required to have a low frequency cut off of 20hz with no room gain needed to support the low frequency response. The subs are quite a bit larger and more powerful than their earlier approved models, so they recommend a placement that avoids exciting the rooms modes and nodes. The problem with this placement is once again, it places more demands on the subs themselves to provide the necessary gruntage to reach the second octave cleanly. Some do okay with this, and some have to struggle a bit depending on the size of the room they sit in.