[cameraman]

Any guides on how to set up the system, tones, links, articles, etc.?

I’ve set up stereo listening using Home Theater Bypass and am really enjoying it and now want to dial it in as best I can.

Currently I use an Oppo HA-1 as the preamp and I’m already thinking about an upgrade but will work with it for the time being. I wish I still had the BP26 I used when I first set up my 2.1 system.

For a crossover I use a Bryston 10B-SUB Electronic Crossover in Stereo 2-way summed low pass mode.

It has been so long since I used the crossover in a stereo system, I forget how I set everything up. I remember using a sound meter to set the sub level via tones and still have the sound meter somewhere but can’t find the link or instructions on what tones, level, etc.

My “towers” aren’t really designed to produce much under 70 Hz and are sealed so it should make it pretty easy to balance the mains with the sub/s.

The room is not ideal for acoustics and I am experimenting with different subs, switching some that are currently connected to the surround system and trying them in my stereo via theater by-pass. I also want to try my 18" sub and possibly both. I’m finding I rarely use the room as a theater, it’s usually just for music. All my available subs are different sizes and all but one is a sealed design, the outlier has a passive radiator.

For mains I use Vision Signature Speakers, a DIY Kit using ScanSpeak Revelator drivers by North Creek Music, powered by a Bryston 6BSST. Currently I use an Aurasound - 12" NS12-794-4A in 2 cubic foot sealed box powered by a Bryston 7BST and the 10B-Sub using a High Pass at 80 Hz with a 6db slope and low pass at 80 with an 18db slope. I want to add a second sub, my DIY North Creek Music 18" Leviathan in 4 cubic foot sealed box. I have a 4BST available to power a second sub. The Bryston 10B-Sub can support two subs and I assume since the subs are different, I should run them summed.

Here are details on the speaker design with the expected hyperbole.

https://web.archive.org/web/20030412105145/http://www.northcreekmusic.com/Vision/VisionInfo.htm


George Short helped me when I first set the system up and possibly James Tanner but that was in the early 2000's. The 10B-Sub crossover allows me to mute the high pass and low pass separately. I seem to remember playing test tones for each and then adjusting the High Pass Level to balance High and Low. I understand high and low levels may not measure the same way but I thought it helped me get everything close. I think I still have the Radio Shack sound meter and probably some test tone CD's, I just don't recall which tones and the steps I used.

Thanks.

[James Tanner]

Hi

Just so I understand you are using two different Subs - how different?

james

[cameraman]

Hi

Just so I understand you are using two different Subs - how different?

james

I have a few available but was thinking

DIY - North Creek Music 18" Leviathan in 4 cubic foot sealed box

DIY Aurasound - 12" NS12-794-4A in 2 cubic foot sealed box.

[James Tanner]

Are they internally powered?

james

[cameraman]

Are they internally powered?

james

No, powered with a 7BST and a bridged (if needed) 4BST.

Thanks.

[James Tanner]

Hi

OK I would use the 10B in stereo mode. I am not sure if the efficiency of the subs are close but you can adjust the volume of the mains relative to the subs using the center controls.  You have plus or minus 5dB adjustment there.

You can use a sound pressure meter and a pink noise frequency to adjust and I find that works well.  Just try to get similar readings at about 85dB in and around the crossover point between the subs and the mains.

james

[cameraman]

Thank you.

Hi

OK I would use the 10B in stereo mode. I am not sure if the efficiency of the subs are close but you can adjust the volume of the mains relative to the subs using the center controls.  You have plus or minus 5dB adjustment there.

You can use a sound pressure meter and a pink noise frequency to adjust and I find that works well.  Just try to get similar readings at about 85dB in and around the crossover point between the subs and the mains.

james

[brucek]

DIY - North Creek Music 18" Leviathan in 4 cubic foot sealed box

DIY Aurasound - 12" NS12-794-4A in 2 cubic foot sealed box.

Unless the two subs are fairly evenly matched, there may be a problem. You appear to be combining a 12" and an 18" sub.

Yes, two subs positively re-enforce each other at frequencies where they are both capable. This results in increased output and headroom at those common frequencies and as such allows you to turn each sub down to realize the same output as one sub produced. That's the good part.

Here's the rub. The common frequencies that don't share a similar output are not reinforced and as such the output level for those frequencies are lower. This compromises the better subs overall response. Instead of the extended smooth response, the result is a lower response in the areas where the better sub should excel.

brucek

[cameraman]

Thank you.

I thought the main advantage of multiple subs was placement and smoothing response, not necessarily increasing bass decibels. My room is an odd shaped bonus room over the garage. It is a decent sized room but has a ceiling that slopes with the roof line from the front of the room to the rear. It also has two dormers with windows with flat ceilings in those areas.

I can use a single 18” and get plenty of bass but thought by using two or even more I could get a smoother response.

These articles for example:

Two Great Articles on Multiple Subwoofers by Dr. Earl Geddes

http://seriousaudioblog.blogspot.com/2012/05/two-great-articles-on-multiple.html

And this summation from Home Theater Review;

“Place a single subwoofer in a room, and it'll have huge peaks at some frequencies and huge dips at others. The frequency and magnitude of the peaks and dips vary tremendously depending on where you're sitting. Add another sub somewhere else in the room, and because of its different position, it will interact differently with your room's acoustics. It'll have peaks and dips at different frequencies, and thus will partially cancel the first sub's response errors. Add two more subs, and the response should get even smoother.”

Internet searches bring up lots of other information supporting the idea and if it is on the internet, it must be true 😊.

Unless the two subs are fairly evenly matched, there may be a problem. You appear to be combining a 12" and an 18" sub.

Yes, two subs positively reinforce each other at frequencies where they are both capable. This results in increased output and headroom at those common frequencies and as such allows you to turn each sub down to realize the same output as one sub produced. That's the good part.

Here's the rub. The common frequencies that don't share a similar output are not reinforced and as such the output level for those frequencies are lower. This compromises the better subs overall response. Instead of the extended smooth response, the result is a lower response in the areas where the better sub should excel.

brucek

[brucek]

I thought the main advantage of multiple subs was placement and smoothing response, not necessarily increasing bass decibels.

Yep, and that's if the subs are matched, then you can smooth the response in a room.

Your picture shows an 18" sub and a 12" sub. Think of the response of the two. One goes very low, the other doesn't. Consider the situation where the two subs both produce 50Hz and are similar in that response. They re-enforce each other and the volume increases, so to balance the level with the other mains speakers you turn down the two subs equally and now at 50Hz the level matches the mains. But also remember that the 12" sub doesn't have anywhere near the output level at 15Hz-25Hz that the 18" sub does. See the problem? By turning down the two subs to get their level to match the mains you are turning down your only source of 15Hz-25Hz. It's just an example, but it's a reality of combining a small and large sub.

brucek

[James Tanner]

Hi Folks,

Here are some graphs we did as we added the Bryston subs to the listening room.



james

[brucek]

Here are some graphs we did as we added the Bryston subs to the listening room.

Sure, but those are all identical subs with identical frequency responses. Makes sense.

But, the original poster is talking about using different sized subs (i.e. 12" and 18" mixed).

What happens is that the response will dumb down to the weakest sub. Not the best solution I would think.

The OP would be better off just using one of those two subs.

brucek

[cameraman]

I'm not an expert by any means and know not all agree with the Dr. Geddes method but I believe Geddes specifically recommends multiple and different (not matching) subs to force more randomness (and I assume averaging) of room modes. He also runs mains full range, which I am not doing, but possibly I could since they roll off pretty fast under 70 Hz.

Sure, but those are all identical subs with identical frequency responses. Makes sense.

But, the original poster is talking about using different sized subs (i.e. 12" and 18" mixed).

What happens is that the response will dumb down to the weakest sub. Not the best solution I would think.

The OP would be better off just using one of those two subs.

brucek

[brucek]

I'm not an expert by any means and know not all agree with the Dr. Geddes method but I believe Geddes specifically recommends multiple and different (not matching) subs to force more randomness (and I assume averaging) of room modes. He also runs mains full range, which I am not doing, but possibly I could since they roll off pretty fast under 70 Hz.

Your smoothest results will come from selecting a crossover point for the mains rather than relying on their natural drop at low frequencies.

If you select 80Hz for example, the signal will drop at the same dB/octave as the sub, and the resulting combined signal across the crossover frequency will be smooth (as shown in red in the following image).




brucek

[James Tanner]

HI Folks,

What's great about the 10B Sub electronic crossover is that you have control on both the low pass and the high pass at the crossover point. 

So if you want to overlap the low response of the Mains with the upper response of the Subs it is easy to do on the front panel of the 10B.

You can also adjust the slopes (6,12,18dB) on both the high pass and the low pass as well.

james

[ragg987]

One goes very low, the other doesn't. Consider the situation where the two subs both produce 50Hz and are similar in that response. They re-enforce each other and the volume increases, so to balance the level with the other mains speakers you turn down the two subs equally and now at 50Hz the level matches the mains. But also remember that the 12" sub doesn't have anywhere near the output level at 15Hz-25Hz that the 18" sub does. See the problem? By turning down the two subs to get their level to match the mains you are turning down your only source of 15Hz-25Hz. It's just an example, but it's a reality of combining a small and large sub.

This may not apply, it will depend on the capability of your subs. Both can give similar frequency response from 15 to 100Hz, the 18" will have the potential of higher SPL compared to the 12" of 6 to 8 dB, though of course you can try to level match them at sensible listening levels as anything beyond 80dBA is probably not needed in most homes and the 12"should comfortably deliver around 100dBA.

See here for example curves, both the 18 and 12" subs have very similar response curves, probably within ±2dB.
http://rythmikaudio.com/F12SE_specs.html
http://rythmikaudio.com/F18_specs.html

So I would say go for it. Have a search for Welti recommendations for positioning the 2 subs. And make sure you take care of phase matching at the crossover frequency, this is a bit harder to do than just measuring distances, but will yield a much smoother integration from mains to subs if you get it right.

[ragg987]

Your smoothest results will come from selecting a crossover point for the mains rather than relying on their natural drop at low frequencies.

If you select 80Hz for example, the signal will drop at the same dB/octave as the sub, and the resulting combined signal across the crossover frequency will be smooth (as shown in red in the following image).




brucek

100% that is your objective, but pay attention to phase as well as cross over frequency or you cannot achieve that target line.

[James Tanner]

Hi

With the 10B as you adjust the slopes from 6/12/18dB you are also adjusting phase.

I usually start with 18 on the sub and then try 6, then 12 then 18 on the highpass (Mains) and see which one gives you the best bass response and integration.

james