Subs and the quest for bass.

I recently picked up a Rythmik Audio F12SE subwoofer to compliment my B&W 805S. Happy with it, and the Rythmik has very musical bass. I am using an active crossover (NHT-X2 crossing at 80hz) and a Velodyne SMS-1 sub equalizer to even out the low end response. (I have a lot of bass modes.) The SMS-1 is very useful, and with help of quite a bit of EQ, my low end response is almost perfectly flat.

While it sounds great, I keep wondering how different the sound would be if I didn't have to use so much EQ. Then I started thinking maybe I should add another sub? When I started I told myself I would not do it. Also I had so much trouble getting good placement and setup with the first sub, I don't know if I even want to further complicate things.
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I was happy with using one sub before,and didn't realize what a second sub could do for the music.
Musically,a second sub gave the music what I'd call more of
complete foundation.
I didn't realize how much of a improvement a second sub would
bring to the music.
If your sceptical,I'd see if you could borrow one and let your
ears decide.I think you'll be quite surprized and I bet you'll
wonder why you didn't do it earlier.
For me I won't go back to one sub,that's how much an improvement two will give you.
If two can improve the music in my not so ideal room,
I'm sure you'll like what two can do for you.

As you probably know, I use exactly the same set-up, but with 2 Rythmiks. If you go this way, you will definitely reduce the amount of EQ you deploy but:

1) I didn't hear much/any difference between a single sub and dual subs with the SMS. The amp in a single sub never sounded remotely taxed by the EQ'd signal, so I was never aware of the EQ being applied. Partly, of course, this is the result of the EQ needed for my room which may differ dramatically from yours. If so, all bets could be off.

A single sub just sounds neutral, powerful, and perfectly integrated in my set up. One sub was enough, but I started with two and decided to stay that way. Doesn't hurt, but - honestly - it might well be overkill.

2) The SMS is still a great tool for dual subs. Even though the "native" response of dual subs is much, much smoother, I still use 3 bands of EQ to address meaningful deviations in response. However, it's the "fine tuning" with the SMS right at the x-over point that really makes a difference. One sub, two or even four, the SMS (or equivalent) is still the best customizable subwoofer high cut that I've found.

The good news is the the Rythmiks are money back - so you can try a second one on their dime. Just don't expect a lot of impact.


PS Make sure that you experiment with the Q setting on the Rythmik - it does make an audible difference.
I see that I dropped one sentence re: my specific set-up.
I always sit in 1 spot - no variation. If you move around in your listening room, the second sub will definitely provide benfits vis a vis an EQ'd single sub.

I added a second subwoofer (B&W) and it does make a noticeable difference in room loading. While the first sub probably provides enough LFEs, there was an obvious dead area in the far corner of my large room. The second sub simply fills that void and provides far more balance in the low frequencies. Not absolutely necessary but simply a strong preference.
If I get the second sub, I'm guessing the best possible placement would be to pair one with each speaker, correct? Another benefit of that is I could also cross over higher. Right now my room is set up so the speakers are in the exact middle of the room. Should I place one sub on each side wall, lined up with it's respective speaker?

Also right now my speakers are in a dedicated room and have nothing to the right or left of them. Would placing subs near them affect the sound of the speakers any, or cause any negative impact in imaging? The bottom of each speaker (using b&w 805s bookshelfs on stands) is 7 inches taller than the subs.
Sorry for the triple post, but one last thing, if I were to use the above mentioned placement, how would I set the phaseof each sub? Would it be the same on each of them? (0 I'm guessing?)

If you're looking for the least EQ, my guess is that the corners wide of and behind the speakers will work well. I tried pretty much every combo of corner/corner, corner/midwall, and midwall/midwall (note: my room has no wall behind the listener). Some were slightly better than others, but there wasn't a ton of benefit (as measured by the SMS' RTA function) to any other location and the corner placement is symmetrical and eye appealling. OTOH, you will almost certainly see deterioration in the native (non-EQ'd) response if you pull the subs away from the wall and place them near the speakers.

Good Luck

Well I also have no way to time delay my main speakers, which is also why I like the idea of placing them near the speakers.

I understand your point. Take a listen. Take a look (at the SMS-1 readout). Both will confirm that near wall placement (at least IME) yields much smoother response (pre- EQ).

If you don't care about the amount of EQ, it may not matter. Put the subs where you want and EQ them to your preferred response. If you want to minimize EQ, the subs will (probably) have to be against the wall. Corner placement raises the overall output level of the subs, meaning you'll be optimizing response for reducing peaks rather than boosting troughs, generally IME a good thing - though probably not essential with dual Rythmik 12 inchers in your room.

BTW, if you're crossing below 100hz, I don't think you'll hear any impact on imaging (at least, I don't) relative to sub placement. As your crossover point moves north, well....

Best of luck with the project.

Are you placing your rythmiks in back corners as well? Do you have any sort of delay for your mains? How far are your mains from your sub? Have you noticed any delay in when the sub hits?

Subs are behind and wide of the mains and crossed at app 75 hz. No delay applied. Overall, this is the best bass I've ever managed to achieve. Zero complaints and integration is seamless. Blind, I would never guess that there were subs in this system

Good Luck

Sorry I should have mentioned that the subs are app 3 feet further from my listening position than are the mains (13 feet vs 10 feet) and maybe 4 feet wider apart in total.

So are you using two SMS-1s so each SMS-1 gets it's own seperate signal? (true stereo)
Summed with common EQ. Works fine (for me, anyway) when crossed at 75 hz.

If I were to go the stereo bass route, how would I eq for 2 subs? Each sub would be getting it's own singal (right sub gets the right channel signal, left gets left) What process should I use for EQing? After level matching the subs, should I just EQ them together to get a combined flat response? What I am wondering about though, is if a certain track has the bass on one side of the soundstage, then it will only come out of one sub, right? wouldn't that make it no longer have a flat response?

I've thought about the "how to" issue with stereo subs and a pair of SMS-1s, but never actually tried it, so I can't really say. At these low frequencies (i.e. crossing below 100hz), I really don't think that you'll hear any impact from stereo subs.

If you want to test that theory, find a highend HT store that will set up a pair of subs for you in a way that allows you to kill the main speakers and listen to the subs alone. Then have a shot at the balance control. I tried (a variation of) this test and decided that stereo subs didn't matter to me. Of course, YMMV.

BTW, I'm pretty confident that the SVS/Audyssey does true stereo/independent channel sub signal EQ which solves the issue.

So i got my second rythmik... Having some problems. I actually had to EQ MORE with 2 subs. Is it maybe becuase of my non symmetric room setup? Also even though everything is EQed to flat just like it was before, it seems like I have slightly less bass now. The only real benefit I've noticed so far is the sub is I can no longer localize the subs.
Here is a pic of how I have the subs set up right now in my room:

The subs are placed symmetrically, but as you can see, one corner of my room sticks out farther than the other (about 2 feet) I'm wondering if this is causing me problems. Any suggestions?
Hi Nemesis, I see that you are measuring your system with the SMS. I find that this system is resolution limited, amongst a few other problems. The main problem though is the lack of ability to save graphs.

You asked, "any suggestions?"

May I suggest that you try the FREE program REW available at the Home Theater Shack. You allready have a mic, meter and Laptop. All you need then is to download the new version 5, which just came out, for FREE. Then you will be able to post pictures of your response and help will be easier to dispense.