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Will adding more subs really improve bass response in a properly calibrated setup?


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#1 of 62 Jeff_M

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Posted July 16 2004 - 05:13 AM

God bless all of you maniacs out there with multiple subs. I love chest pounding bass as much as the next guy, so this is no knock on you. I have a fairly basic question. I will use my system as an example. I own an SVS 20-39 PC+. My calibration was fairly simple. I got out the Avia DVD, an SPL meter, and ran a test tone to set the 5 speakers and sub to the same db level. I never run my receiver any higher than -10 (which is really loud). The SVS is definitely a stud, and handles everything I throw at it without bottoming or audibly distorting. I love it. Now I have to admit that I contemplate adding a second sub from time to time (not because I am dissatisfied with the sound, but because I hear you guys rave about multiple sub setups and I am curious). If I were to add a second sub and recalibrate, wouldn't I simply be backing off on the subwoofer gain so that the two subs would match the db level of my speakers. In this case, how would there be any more bass while watching movies?

#2 of 62 John S

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Posted July 16 2004 - 05:22 AM

How large is your room?

Larger rooms, benefit the most from dual subs in my experiences.

#3 of 62 Jeff_M

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Posted July 16 2004 - 05:32 AM

My question is more of a general one, and not specific to my situation (I have a small room). I'm not looking for advice on whether or not to get the second sub, I'm tying to see what other members have gained by adding 2nd or 3rd (or 8th!) subs. If you are running your subwoofer at the calibrated level (not hot), how does more subwoofers equal more output? Lets say that my sub and speakers are calibrated to 85db. I play a particularly bassy movie scene and my meter reads 115db. If I add a second sub, recalibrate to 85db, won't my meter still read 115db for the same movie scene. If so, aren't the extra subs a waste?

#4 of 62 John S

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Posted July 16 2004 - 05:38 AM

In larger rooms, if you get much away from your sweet spot for calibration area, and you see inordinantly drastic dips in the DB response of the sub channel. Then you are a good candidate for a 2nd sub. If not, then it really would not have all to much benefit, aside from the fact each sub would not be working as hard in general. So it could prolong the life of any given sub.


One the budget mined, 2 relatively inexpensive subs being run, can be a cheaper and just as effective of a solution as one quite a bit more expensive larger sub as well.

#5 of 62 Chris Tsutsui

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Posted July 16 2004 - 07:38 AM

I've had some experience swapping between 2 tempests in a room that's no larger than 11 feet by 8 feet.

The bass quality got better, especially during loud bass scenes. It improves the headroom, and you'll find that you can turn down the volume of your single sub when you upgrade to two. I think you can get as high as 3-6 decibels of added headroom. I forgot what I measured, but I think it was about 3 decibels extra. This may not seem like much, but most of it will be heard in the bass quality...

I did setup my dual subs in stereo, instead of stacking or side by side positioning. This resulted in a significant change in the dips and peaks of my bass response. I used to have it all graphed.. but I remember that by positioning the subwoofers in the right locations I was able to eliminate some standing waves.

If you wanted to maximize the output of your system, I would take all your multiple subs and bunch them tightly in one corner. hehe.. then put your listening position in the opposite corner and take some SPL measurements.. lol You'll get some incredible peaks I think..

I wouldn't consider more than 2 subs though unless you really need the output. Oh and to answer your question.. if you added a second sub, you would probably be setting both of the levels the same, and it would be about 3 decibels less than what you have your sub set at now. As for SQ, you might notice the bass sounding a bit cleaner and sound less like a thundering subwoofer. It could also sound more integrated with the bass that your mains produce.


#6 of 62 steve nn

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Posted July 16 2004 - 09:51 AM

Your assessment imo is correct Jeff.

If I were to add a second sub and recalibrate, wouldn't I simply be backing off on the subwoofer gain so that the two subs would match the db level of my speakers.

You would be backing the gain off 6 db to achieve the same calibration dual colocated.
In a smaller room dual or more is not needed imo if you have good response. EQ is another option also.

I have run multiple 25-31CS+'s for quit some time and have decided to back off. One is in the den just sitting and the other two are still in the HT. I generally just run one now with the second as a compliment to the single when I feel it's called for. My listening habits do not exceed -15 most of the time and -10 would be very seldom. My HT is 2880 cf / 12 X 24 X 10 with one very leaky wall.

The subject matter of your Thread has been on my mind for some time and it's interesting to see it come up. Headroom is very important to me so please don't take this wrong. The simple fact is in my mind i'm over powered. I have more headroom than what I feel is appropriate, for me.

Most likely I'll sell two of the 25-31CS+'s (keep one) and pick up another SVS option, maybe two. (Talks are in the works) So I guess I'll be a collector of SVS subs in the future instead of seeing how many multiple I can run.

If I add a second sub, recalibrate to 85db, won't my meter still read 115db for the same movie scene.

If it is a second like sub then yes 115 with less stress and possibly a little better sounding? Just depends on how much headroom you have with the single.

I was very surprised to see what one 25-31CS+ could do in my HT on account of me running multiple for so long. One heck of a woof I tell yeah.

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Thnx Ed

#7 of 62 SteveCallas

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Posted July 16 2004 - 11:14 AM

I can answer this question - Chris already touched on it. You gain 2 things by using multiple subs.

First, you will hear a large difference in the QUALITY of the bass, it will be much more detailed. I do not own any SVS subs yet, but with my first sub, when it would play something low and loud, it sounded good, but kinda blah. When I added a second sub of the same model, collocated in a corner about a foot apart, the low and loud bass scenes were better because the bass seemed to have more texture(for lack of a better word). In other words, with one sub it would be like listening to a speaker with a blanket over it and when I used two it was like the blanket came off.

Secondly, you gain more output AT LOWER FREQUENCIES. You will have to back the first sub down a bit and recalibrate the two subs so they play at the same level and combined they only reach what your preference was before, but now, since they each can work slightly less hard, the lower frequencies will be louder. For example, if you liked one sub at 85db, but its response started to drop at 20hz, by backing it down to maybe 80db, it can now play 18hz more solidly, and by adding the second sub and having it calibrated to 80db, where it can also play 18hz solidly, you now have two subs playing 18hz at 80db which will total around 85db (depending on room placement), which it was not capable of doing before.

These may not seem like huge benefits to you, but I would never go back.

#8 of 62 Kevin C Brown

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Posted July 16 2004 - 01:00 PM

2 subs gets you more output, but it doesn't improve low freq response unless you were reaching the limits of the single sub before. That's probably not the case since Jeff says he has a small room. Jeff, you might consider a better sub (with more low freq extension) rather than just another of what you already have. The PB2+ is a nice one. Posted Image
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#9 of 62 steve nn

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Posted July 16 2004 - 01:10 PM

>>I do not own any SVS subs yet, but with my first sub, when it would play something low and loud, it sounded good, but kinda blah. When I added a second sub of the same model, collocated in a corner about a foot apart, the low and loud bass scenes were better because the bass seemed to have more texture(for lack of a better word). In other words, with one sub it would be like listening to a speaker with a blanket over it and when I used two it was like the blanket came off.<<

You were definitely beyond your subs capacity Steve so hence adding the second was really a nice improvement. Totally understand and agree. Now lets say you were running a much more capable sub. Lets say a PB2+ for instance in a closed off 10 X 18 X 9' room calibrated to a +2 db calibration. Do you think you would gain by adding another PB2+ and calibrating them together to the same level? You would definitely have more headroom but will it be utilized considering the headroom you already had? It gets kind of tricky and a blanket statement will not cover. All aspects need to be considered. Boiled down it depends on what sub your running in what room and the headroom if any the single sub has correlated to your listening habits.

If we get into increasing the sweet-spot, Rounding, taming. Then thats a whole different matter and not really the question Jeff presented.

EDIT> Jeff, you might consider a better sub (with more low freq extension) rather than just another of what you already have. The PB2+ is a nice one.<<

Agree and imo sound advice. But then you have a 20-39PC+ and headroom to boot so your sitting good.

#10 of 62 SteveCallas

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Posted July 16 2004 - 02:44 PM

Steve nn, you're probably right, my subs weren't anywhere near the best to begin with, and with the dimensions of your room, you again are right in that you would probably see no benefit. But if the room were bigger, even with a PB2+, I would still have to think you could achieve better base with 2 subs...if anything it would at least help flatten the frequency response if placed correctly.

#11 of 62 Nick Laho

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Posted July 16 2004 - 03:11 PM

This is what I believe I have to eventually convince my dad to do. (Get another PB1-ISD) We are definitely at the subs limits in our current room.(Which is rather large, and odd shaped in the rear) It is just barely loud enough, and sounds strained. It has NOT bottomed ever though, so we aren't damaging it. I feel that it is good volume wise, but the quality is lacking because, again, its strained. If I can get him to buy another one in the future, I think the extra 6 db will really help. (Just turning both subs down a little so its the same volume as before, just neither sub is running beyond its limits.)

#12 of 62 steve nn

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Posted July 16 2004 - 04:25 PM

But if the room were bigger, even with a PB2+, I would still have to think you could achieve better base with 2 subs...if anything it would at least help flatten the frequency response if placed correctly.

I understand your logic SteveC and I did mention it in a earlier post. I agree. >>>If we get into increasing the sweet-spot, Rounding, taming. Then thats a whole different matter and not really the question Jeff presented.<<<

Another PB1-ISD colocated in your HT Nick would be like a cold drink of water on the hottest day. 6 db's equates out to much more than what some would think.

#13 of 62 frank manrique

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Posted July 16 2004 - 04:36 PM

quote:

"If you are running your subwoofer at the calibrated level (not hot), how does more subwoofers equal more output? Lets say that my sub and speakers are calibrated to 85db. I play a particularly bassy movie scene and my meter reads 115db. If I add a second sub, recalibrate to 85db, won't my meter still read 115db for the same movie scene. If so, aren't the extra subs a waste?"

This is the sort of question that would be better answered by such savvy people as Tom V, Ed, Mark, or Craig--to name but a few--but let me give it a shot anyway...

In addition to gaining output capabilities, more subs will also allow for higher dynamic range, greater overall power handling capacity...and much, much better chances of pushing distortion components to well below the level of what the human ear can detect at moderate and higher sound pressure levels.

Other benefits are also gained (all other things being equal), but the above should be enough data to help you understand the benefits brought by the application of multiple sub-bass transducers included within a single sound system...

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

#14 of 62 steve nn

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Posted July 17 2004 - 03:58 AM

Frank there are bassaholics and then there are bassaholics.Posted Image I consider myself a bassaholic and admittedly I want them all but you are the big kahuna. If I could just get my wife on board. If your HT were 4 X 4 X 4 you most likely would see a need for at least one B4-PLUS if not dual and then you would see reason to keep adding.



In addition to gaining output capabilities, more subs will also allow for higher dynamic range, greater overall power handling capacity...and much, much better chances of pushing distortion components to well below the level of what the human ear can detect at moderate and higher sound pressure levels.

I agree with you fully except to say imo there is a limit. (Depends on room and sub/subs) Lets say you decided to increase your dual B4+'s - Eight 20-39 CS's to Four B4+'s and Sixteen 20-39 CS's. Nope no need to answer. I think you would consider it a major improvement.Posted Image I say that playfully Frank.

If you were the owner of SVS I can imagen a mail going like this>>

Mr. Frank M
I have been contemplating the purchase of a SVS sub woofer for some time now and feel like I could use a little direction. My HT room is 12 X 14 X 8 all closed off. Could I bother you to give me a good suggestion on what it would take to fill my room with good quality bass? My listening level is generally around -18 up to -12.

Thank you for your time. Jimmy
__________________________________________________ _______

YOUR REPLY

Jimmy,

Thank you for considering a SVS product. What I would like to suggest to you is Two PB2-ULTRA's and Two B4-PLUS's. This option ought to get you by until budget permits you to add another set of PB2-ULTRA's. Please let me know if I can be of any more help.


"...by, my name is Frank...and am an SVS bassaholic..."

__________________________________________________ ______

Once again I agree with you Frank but I just think there is a limit. It really depends on how easy Jeff can hit the 115 dB he spoke of. Most likely he would gain by adding another, as many would. Thanks for being a good sportPosted Image

#15 of 62 Kenneth Harden

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Posted July 17 2004 - 09:18 AM

Having twice the cone area HAS to count for SOMETHING.

I would love to experiment with a few subs (run one, then run two) and see what the numbers said.

#16 of 62 frank manrique

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Posted July 17 2004 - 09:25 AM

steve nn,

Great post! Am still laughing...though my stomach now hurts a lot, so thanks a lot, pal! Posted Image

Regarding my "tutorial" above...it was given in the vein of pure rhetorical generalities.
Of course you're right; it all depends on the size of a particular room otherwise it would be as crazy as to attempt placing a huge diesel engine in one of 'em 'lil trucks: it would be absolutely impossible! Posted Image

As to my "crazy" idea of using (or wishing to, anyway; can't ascertain things will work as one wishes) that many SVS infrabass systems...please refer to what I postulated earlier in another thread; you just might be surprised by what I have to say...

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."

#17 of 62 steve nn

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Posted July 17 2004 - 10:38 AM

As to my "crazy" idea of using (or wishing to, anyway; can't ascertain things will work as one wishes) that many SVS infrabass systems...please refer to what I postulated earlier in another thread; you just might be surprised by what I have to say...

I'm glad your laughing Frank.>Seriously..... We're on the same page and I enjoyed reading the post you alluded to. It ads allot of insight to where your coming from.

Can't get this post to post rightPosted Image

#18 of 62 dave alan

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Posted July 17 2004 - 03:04 PM

I just wanted to add that all of the above posts refer to multiple subs playing the same summed signal.

There are other configurations that require multiple subs.

Stereo subs, in which the left sub gets the left surround, left front and 1/2 of the center redirected bass plus the LFE signal and, conversely, the right sub gets the right surround, right front and 1/2 of the center redirected bass plus the LFE signal.

Assuming identical subs:

The output will be the same as a single sub with music program and 1-3 dB more with program that contains LFE or .1 signal, but you'll have more headroom in each sub.

Rebase routing, in which 1 sub gets discrete LFE signal only and the other sub gets discrete redirected bass only will also yield equal output to the single sub, but each sub will have 5-6 dB more headroom.

SPL and headroom, of course, aren't the reasons to use these multiple subs configurations. The benefits of seperating the .1 channel's signal (DVD, SACD, DVD-A) from the redirected bass signal(s), are many, and in-the-near-future formats will be even more conducive to use of multiple subs.

#19 of 62 Glenn Shoemake

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Posted July 17 2004 - 05:21 PM

Currently running two SVS Cylinders a PC+ 16-46 and a PC Ultra in a room 12'x11' and I immediately noticed an improvement in the intensity of the bass. Once calibrated they are both backed down quite a bit, however when a bassy scene hits the room shakes over twice as much as it did before. When doing a subwoofer sweep in Avia once it gets below 30hz everything in the room shakes, walls, doors, projector, projector screen, etc... its almost scary. My PC+ 16-46 never scared me like that when I did the sweep.
The end result is no need for Bass Shakers as both subs do quite nicely.

#20 of 62 frank manrique

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Posted July 17 2004 - 08:46 PM

quote:

"When doing a subwoofer sweep in Avia once it gets below 30hz everything in the room shakes, walls, doors, projector, projector screen, etc... its almost scary. My PC+ 16-46 never scared me like that when I did the sweep.
The end result is no need for Bass Shakers as both subs do quite nicely."

Ah...more SVS bassaholics!... Posted Image Posted Image

-THTS

"...hi, my name is Frank...and am an SVS bassaholic..."