Two subs or To trap

[stanly.joseph]

Hey guys

I'm told that I need to do some bass trapping in my room to remedy certain acoustic problems but I also watched a YouTube video by audioholics stating that bass problems can be rectified by adding a second sub.

Is that accurate? And If I decide to add a second sub, does it need to be of equal size and caliber to the first sub?

I currently own have the B&W ASW855.


Thanks much guys. Appreciate it.

[Steve]

Hey guys

I'm told that I need to do some bass trapping in my room to remedy certain acoustic problems but I also watched a YouTube video by audioholics stating that bass problems can be rectified by adding a second sub.

Is that accurate? And If I decide to add a second sub, does it need to be of equal size and caliber to the first sub?

I currently own have the B&W ASW855.


Thanks much guys. Appreciate it.

Two subs will certainly balance out a room better than a single. Both subs should be the same, yes.

Room corners generally benefit with traps or similar treatment regardless.

[stanly.joseph]

Two subs will certainly balance out a room better than a single. Both subs should be the same, yes.

Room corners generally benefit with traps or similar treatment regardless.

So I should just treat the room first and see how it sounds? I don't think I'll be able to find the exact same sub. Its a pretty old model.

I was thinking of the SVS SB13 ultra sub.

[Family progtitioner]

I think it depends upon if you're talking about bass nulls vs peaks

[Steve]

If you have an old thin foam mattress, you could roll that into a tube and experiment with positioning in various parts of the room beginning with corners. Similarly stack a pile of pillows in the corners.

This would be a good starting point in understanding and potentially identifying peculiarities of your room, where standing wave reflections are originating causing frequency cancellations and peaks.

[FlexibleAudio]

Talk to Nyal at Acoustic Frontiers. He da man.

[ACHiPo]

My $0.02 is that you want both bass traps and multiple subs. The subs improve the peaks and nulls (ideally you have 4 with different damping factors, sizes, etc.), and the bass traps help the waterfall decay. Even with both it's still a struggle to get a really smooth response, but the faster decay makes my ears "hear" smoother sound, and the subs reduced peaks and valleys from ~20 dB range to <~10 dB.

[Al M.]

So I should just treat the room first and see how it sounds? I don't think I'll be able to find the exact same sub. Its a pretty old model.

I was thinking of the SVS SB13 ultra sub.

Yes, definitely treat the room first. Here is a recent experience of mine:

http://www.whatsbestforum.com/showth...-their-absence

I am also thinking about buying Isothermal Traps,

http://www.acousticsciences.com/prod...ermal-tubetrap

for the rear wall (behind my listening seat) in order to prevent deep bass bounce and thus having even better deep bass.

I have a single sub. I used to have two subs, but at the time it didn't make much difference. Room treatment is far more important, but perhaps multiple subs are the icing on the cake. Proper room treatment is probably cheaper too.

[LenWhite]

Talk to Nyal at Acoustic Frontiers. He da man.

I haven't done it yet but Nyal told me most speakers can benefit from subwoofers. But the main speakers/subs must be properly tuned using an external crossover that will allow control of both. Paraphrasing Nyal; properly integrated subs improve the transition from bass to midrange resulting in better articulation in that area.

Nyal is an excellent acoustician - I'm very pleased with my Nyal designed dedicated media room

[ACHiPo]

So I should just treat the room first and see how it sounds? I don't think I'll be able to find the exact same sub. Its a pretty old model.

I was thinking of the SVS SB13 ultra sub.

You don't need to match subs. Check out this article on Swarm subwoofer approach--basically you want different subs (or at least different cut-off frequencies, gain, volume, phase, and damping), with different sizes/types being advantageous to randomize the peaks and nulls (peaks are really hard to address even with trapping, so constructive interference can be your friend).
https://drive.google.com/file/d/0Bxg...Ums/view?pli=1

[stanly.joseph]

Gosh this is getting more confusing! Have anyone used this software measurement kit?

[ACHiPo]

Gosh this is getting more confusing! Have anyone used this software measurement kit?

I use something similar--you need some way to measure room response. I use REW free-ware and a used calibrated mic. It's pretty easy, but will take a few sessions to get the hang of it. I found it enlightening (if depressing) to see what my baseline performance was prior to treatments and subs.

[FlexibleAudio]

I haven't done it yet but Nyal told me most speakers can benefit from subwoofers. But the main speakers/subs must be properly tuned using an external crossover that will allow control of both. Paraphrasing Nyal; properly integrated subs improve the transition from bass to midrange resulting in better articulation in that area.

Nyal is an excellent acoustician - I'm very pleased with my Nyal designed dedicated media room

That is correct but crossover is only the beginning if the room is not properly designed. Room correction and time alignment are also critical to integrate the subs properly. The problem then is managing your analog sources. Time alignment (phase) and room correction get done in DSP. I opted for maxing out room treatments via Nyal as the first step. If the bass is not to my liking I may add subs and an analog crossover (like the Pass XVR-1) but time and room correction are out for me given my love of vinyl. That said, with a good room design, the timing and phase alignment can be handled by sub placement (assuming the room's design has minimized modes). Room correction is also less important if the modes are dealt with in the design phase.

[stanly.joseph]

I use something similar--you need some way to measure room response. I use REW free-ware and a used calibrated mic. It's pretty easy, but will take a few sessions to get the hang of it. I found it enlightening (if depressing) to see what my baseline performance was prior to treatments and subs.

What's the difference between the below room analyzer and let's say the Audyssey XT32 or Anthem room correction?

[Steve]

Sure the Audyssey XT32 will give you a compensation picture but it is has its own biases. For one it is heavy on everything above 5kHz.

[stanly.joseph]

I ordered the XTZ room analyzer. Might need some help interpreting the results since I'm new at this stuff.

[ACHiPo]

I ordered the XTZ room analyzer. Might need some help interpreting the results since I'm new at this stuff.

Contact me and I'll help if I can. I do not use room correction, which Audyssey, Dirac, etc. employ, but a mic and impulse and spectrum analysis software is your friend.

AC

[ACHiPo]

Here's a link to the REW download. While there's no absolute standard, this app seems to be pretty widely used which makes getting help interpreting results easier.

http://www.roomeqwizard.com/

[Steve]

I also use REW with a mic especially designed for it.

[stanly.joseph]

Can I use REW with the XTZ analyzer?

[CPP]

I also use REW with a mic especially designed for it.

Not to mention, the REW software designers regularly visit hometheatershack so getting help and setup and interpretation of what one sees in the results is helpful.

[Vapor1]

The XYZ system will give you the data you need. There are some things about it I don't like as a power user, but for the job of improving the speaker/room interface, it'll do what you want. Having data is one thing however, interpreting it is another. Once you start collecting data, post screen shots and we'll help you figure out what to make of it.

If I remember the picture of your room, you had a lot of left/right asymmetry where the right side was close to 2 wall boundaries. My guess would be the majority of your problems are coming from that side, bass boost from boundary gain, and short window reflections that hurt imaging cues. My suggestion is to collect some baseline data first for both left and right side individually, and both speakers together, gated and ungated FR (taken both at 1m and your listening position), and various forms of decay times. Then apply some treatments to the right side problem area, bass trapping in the corner and first reflection point absorption, then take the same measurements again and compare.

[ACHiPo]

The XYZ system will give you the data you need. There are some things about it I don't like as a power user, but for the job of improving the speaker/room interface, it'll do what you want. Having data is one thing however, interpreting it is another. Once you start collecting data, post screen shots and we'll help you figure out what to make of it.

If I remember the picture of your room, you had a lot of left/right asymmetry where the right side was close to 2 wall boundaries. My guess would be the majority of your problems are coming from that side, bass boost from boundary gain, and short window reflections that hurt imaging cues. My suggestion is to collect some baseline data first for both left and right side individually, and both speakers together, gated and ungated FR (taken both at 1m and your listening position), and various forms of decay times. Then apply some treatments to the right side problem area, bass trapping in the corner and first reflection point absorption, then take the same measurements again and compare.

Good advice, that!

[stanly.joseph]

The XYZ system will give you the data you need. There are some things about it I don't like as a power user, but for the job of improving the speaker/room interface, it'll do what you want. Having data is one thing however, interpreting it is another. Once you start collecting data, post screen shots and we'll help you figure out what to make of it.

If I remember the picture of your room, you had a lot of left/right asymmetry where the right side was close to 2 wall boundaries. My guess would be the majority of your problems are coming from that side, bass boost from boundary gain, and short window reflections that hurt imaging cues. My suggestion is to collect some baseline data first for both left and right side individually, and both speakers together, gated and ungated FR (taken both at 1m and your listening position), and various forms of decay times. Then apply some treatments to the right side problem area, bass trapping in the corner and first reflection point absorption, then take the same measurements again and compare.

I will post screen shots as soon as I'm done with the testing
Still waiting for the unit to arrive. Can't wait!!

Thanks.

[Nyal Mellor]

This is how I explain it to clients:

- the sub 100Hz range is very hard to fix, due to the fact that the room modes are spaced far apart, leading to big peaks and dips in the response
- multi-subs only provide benefits in the frequency range where they are working, which is typically below 80Hz
- benefits from multi-subs include flatter frequency response and reduced ringing, since room modes are driven destructively and speaker boundary interference dips filled
- the LR will contribute to response to about 60Hz with an 80Hz crossover
- yes, you need to crossover your LR to your subs, and not run them "full range" to get the benefits of multi-subbing
- so with multi-subs you still have the range from 60-300Hz where room modes are in "full effect", therefore you need bass trapping
- commercial off the shelf bass traps are seldom very effective below 80Hz, so it's hard to passively control room modes down to 20Hz, even with a lot of real estate...although if you build the room from scratch you can use the structure (walls, ceiling) as a bass trap. That's what we did in Len's room.
- with multi-subs I strongly advise having EQ capability on the sub feed. It's hard to control the response without it.

With multi-subs, EQ, an active crossover and bass traps you can achieve exceptional bass. Most people have bass that is pretty poor. Obviously I get to work with those whose bass is so bad they need me to help fix it, but I've been to very, very, very few rooms where the bass is what I would describe as good. Most people seem to just live with and accept crappy bass, or have not tuned their ears to it.

Ideally you'd want to get within a 5dB window at 1/3rd octave smoothing. That's quite challenging to achieve, especially in small rooms. But the most likely path to success is to use all the tools at your disposal, and to use them in the places they are most effective...ergo that means using multi-subs, EQ, an active crossover and bass traps, not just one of them.

[stanly.joseph]

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[stanly.joseph]

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[stanly.joseph]

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[stanly.joseph]

Single point measurement from main listening position

[ACHiPo]

With the caveat that I'm not familiar with the application, your bass response looks pretty darned good to me for just starting the process. You have a lot of bass energy, but that could just be the mic calibration? It looks like you have constructive interference (mode) at ~28 Hz and some suck out (destructive interference) at ~45 Hz. It also looks like you have a little ringing at 30 and 60 Hz.

What are your thoughts?

[stanly.joseph]

With the caveat that I'm not familiar with the application, your bass response looks pretty darned good to me for just starting the process. You have a lot of bass energy, but that could just be the mic calibration? It looks like you have constructive interference (mode) at ~28 Hz and some suck out (destructive interference) at ~45 Hz. It also looks like you have a little ringing at 30 and 60 Hz.

What are your thoughts?

LOL I have no idea! Used the XTZ hard/software to analyze my room and those were the results. I just know there's a dip and it would be preferable to have a flatter more even curve. I wonder if bass traps would help and if do they ones that will blend in nicely with my living room environment...

[kiwi_1282001]

Single point measurement from main listening position

That is a very good result as a starting point. If you want to know what a bad result looks like check out my system thread (link below).

The XTZ software is not identifying any room modes in the first image.

What you want to see in the first image is more dark blue colour. To get that you need to reduce decay times. To achieve that a combination of moving your listening chair position, your loudspeaker positions and introducing acoustic panels is needed.

Similar challenges at 30, 60 and 120Hz in my room were much improved with the use of GIK scopus tuned trap and Real Trap corners.

[stanly.joseph]

That is a very good result as a starting point. If you want to know what a bad result looks like check out my system thread (link below).

The XTZ software is not identifying any room modes in the first image.

What you want to see in the first image is more dark blue colour. To get that you need to reduce decay times. To achieve that a combination of moving your listening chair position, your loudspeaker positions and introducing acoustic panels is needed.

Similar challenges at 30, 60 and 120Hz in my room were much improved with the use of GIK scopus tuned trap and Real Trap corners.

You're Right!!! Soon after XTZ was done with analyzing, a box popped up on the screen saying "no room nodes found", what does that exactly mean?

So in your opinion, is there anything I can do to improve or should I just leave things alone? I was wondering about adding bass traps and some panels behind the speakers.

[FlexibleAudio]

You're Right!!! Soon after XTZ was done with analyzing, a box popped up on the screen saying "no room nodes found", what does that exactly mean?

So in your opinion, is there anything I can do to improve or should I just leave things alone? I was wondering about adding bass traps and some panels behind the speakers.

Call Nyal. He is the highest return investment you can make in your system. He will tell you what, where, and how. His prices are fair.

[soundsrealaudio]

What kind of acoustic problems are you having?

[FlexibleAudio]

If you are happy with frequency response just focus on diffraction and scattering to tighten imaging.

[soundsrealaudio]

Maybe the sub has a tendency to double at low frequencies. Just raise the low level cut off a little higher. You are not going to get clean musical bass at 30kHz are you?

[stanly.joseph]

What kind of acoustic problems are you having?

I was having issues with boominess/flat bass when the sub was located in a 90 degree right angle corner. All I did was relocate it to the side that's open to a hallway and BAAMMMMM it's much much tighter and musical now....At this point I don't think adding another sub is necessary unless I want to blow the roof top.

Though I might upgrade my current SW to one that has both balanced and unbalanced inputs somewhere down the road.

[soundsrealaudio]

Nice. Should pair well with a nice Pinot.