Major sub issues

Posted by: Potatohead

Major sub issues - 11/18/09 12:08 PM

First off, I'll post a link to a thread on AVS I created, which explains the problem in more detail and what I've done to try and alleviate it.

http://www.avsforum.com/avs-vb/showthread.php?t=1197293

The bass in my room is just totally dead. I am getting some ok levels around the back walls near and behind my sofa, but in the center of the room or towards the screen, there may as well not even be a sub in the room. I've tried everything short of starting to throw a bunch of money at the problem.

My next option I think is some acoustical panels, but I don't know if they'll do anything with lower frequencies. The only other thing I can think of is to order an EP350 to compare and see if perhaps the SVS is just not a good match for the room, but then I either have to deal with selling the SVS or return shipping the 350.

Anyway guys, any ideas are greatly appreciated.
Posted by: Riker

Re: Major sub issues - 11/18/09 12:17 PM

All I can think of right now is do the sub crawl with your sub in the listening position. I have my system in the basement, concrete everywhere, so lack of bass was an issue for me as well. Now I'm running with EP500 AND another 10" sub up front. With both subs going and my main tower speakers to LARGE, and having done the sub crawl to determine the best bass sound in the room, I finaly have the amount of bass I want.

As for acoustic panels, they certainly will not increase your bass response, but they will help with echo / ringing etc.. if you have those issues.
Posted by: Wid

Re: Major sub issues - 11/18/09 12:23 PM


Have you done any frequency sweeps to see if you are really lacking @ certain frequencies.
Posted by: jakewash

Re: Major sub issues - 11/18/09 12:28 PM

The problem is that the punch in your chest is not from your sub, it is usually from the mains and as you have M22's it won't happen. The chest thing is said to be around 60 -90hz and the sub is busy playing ALL low frequncies and smoothly. If you want to feel it in your chest you need to try to optimize the frequency response for around 60-80hz. I have seen this question many times, check out MikeC on AVS, he bought MANY subs looking for that chest thump only to find out he was searching in the wrong frequency range. You could possibly benefit from Hsu and their Mid Bass Module(MBM) System. . This was one reason I went to M80's, with them I get more impact than I did with M22's/sub.
Posted by: ClubNeon

Re: Major sub issues - 11/18/09 12:31 PM

What's the height of the room? You said it is 12' wide by 19' long.

With those two anyway, I can tell you that you'll have the biggest problems at 93 Hz because of the width, and 60 Hz from the length.
Posted by: Wid

Re: Major sub issues - 11/18/09 12:32 PM


That's a very good point Jay.
Posted by: Argon

Re: Major sub issues - 11/18/09 12:34 PM

 Originally Posted By: jakewash
The problem is that the punch in your chest is not from your sub, it is usually from the mains and as you have M22's it won't happen. The chest thing is said to be around 60 -90hz and the sub is busy playing ALL low frequncies and smoothly. If you want to feel it in your chest you need to try to optimize the frequency response for around 60-80hz. I have seen this question many times, check out MikeC on AVS, he bought MANY subs looking for that chest thump only to find out he was searching in the wrong frequency range. You could possibly benefit from Hsu and their Mid Bass Module(MBM) System. . This was one reason I went to M80's, with them I get more impact than I did with M22's/sub.


I can tell you that when I stood (with an unnamed Commander) on the flight line at NAS JAX at a Blue Angels preview several years back, the low level, low speed demo by the F14 - I had no problem feeling that in my chest. My face, legs and arms as well. I didn't have to do the crawl either - although I am sure many have at the receiving end of that awesome sight.
Posted by: Murph

Re: Major sub issues - 11/18/09 12:37 PM

Interesting. I had never heard of a Mid Bass Module. Does it get fed by the LFE channel and go first in the chain and have a built in crossover stripping the mid bass from the LFE channel before sending it to the sub or does the sub still get the full frequency load. Didn't seem clear to me from the article.
Posted by: jakewash

Re: Major sub issues - 11/18/09 12:47 PM

I don't know the exact working either, I just know it is out there and there are reports from those that have one that it has helped with that slam feeling. I know I had LOTS of slam with the M80s and A1400, oh how I want one...........

Just to add, I know many are looking for that slam like in a bar, if you look at the specs of those pro speakers many only play into the 30-40 hz range with a bit of a boost in the mid bass range (60-90hz) which gives them that slam(along with oooddlles of power) and believe it is a sub doing the job, but it is not. I also know there are some pro subs out there spec'd for this slam range as well.

The graphs of the PB12-NSD has a bit of a boost in the 50-60hz range, (I had one briefly but didn't like the thump it had) but your room could be killing that frequency and Chris has nicely pointed out it looks to be the case.
Posted by: Potatohead

Re: Major sub issues - 11/18/09 01:49 PM

 Originally Posted By: Riker
All I can think of right now is do the sub crawl with your sub in the listening position. I have my system in the basement, concrete everywhere, so lack of bass was an issue for me as well. Now I'm running with EP500 AND another 10" sub up front. With both subs going and my main tower speakers to LARGE, and having done the sub crawl to determine the best bass sound in the room, I finaly have the amount of bass I want.


It seems the concrete could be an issue for me as well. I do have all walls insulated and a proper subfloor, but maybe that is not enough. Now I wish I didn't sell my smaller Velodyne, at least to test. I have done the sub crawl with the sub in my listening position twice, same result both times.

 Originally Posted By: wid

Have you done any frequency sweeps to see if you are really lacking @ certain frequencies.


I don't know how, to be honest. I looked into this REW thing but I have no idea where to even begin. I know nothing at all about computers and sound cards. It certainly sounds like I am lacking in the 50 - 80 range though. I have my crossover on the W22's set at 80, which is where Audyssey set it. The very first time I ran Audyssey (sub in a different position) it set them at 60hz. Maybe I should lower it back to 60?

 Originally Posted By: jakewash
The problem is that the punch in your chest is not from your sub, it is usually from the mains and as you have M22's it won't happen. The chest thing is said to be around 60 -90hz and the sub is busy playing ALL low frequncies and smoothly. If you want to feel it in your chest you need to try to optimize the frequency response for around 60-80hz. I have seen this question many times, check out MikeC on AVS, he bought MANY subs looking for that chest thump only to find out he was searching in the wrong frequency range. You could possibly benefit from Hsu and their Mid Bass Module(MBM) System. . This was one reason I went to M80's, with them I get more impact than I did with M22's/sub.


Thank you, I think this just has to be the problem, there really is no other explanation. I will look into this.

 Originally Posted By: ClubNeon
What's the height of the room? You said it is 12' wide by 19' long.

With those two anyway, I can tell you that you'll have the biggest problems at 93 Hz because of the width, and 60 Hz from the length.


It's 8' ceilings, but with a bulkhead on one side which makes it about 7' which takes up about 14" of ceiling space.

 Originally Posted By: jakewash


The graphs of the PB12-NSD has a bit of a boost in the 50-60hz range, (I had one briefly but didn't like the thump it had) but your room could be killing that frequency and Chris has nicely pointed out it looks to be the case.


Is there any way to correct this? I assume not. Is it possible a different sub would change anything? I guess this mid bass module would solve it, it's just a major pain to ship stuff back to the US if it doesn't help.

Again guys, thank you for the help.




Posted by: jakewash

Re: Major sub issues - 11/18/09 02:05 PM

I am afraid a different sub wouldn't help much other than it might feel louder for the same volume level, this was what I experienced moving up to the PB13 from the PB12. I would still try the sub in various locations to see if you can achieve the sound/feel you are looking for, the sub crawl is more for even/loud sound, you may find a spot that works better for your tastes.
Posted by: Potatohead

Re: Major sub issues - 11/18/09 02:24 PM

I have tried it all around, if I put the sub in my seating area (moving the couch), where it is I have the most feel and the most db. Crawling up front by screen there is literally nothing there, it's super weird to feel in person, it's almost like turning the sub off other than the pressure difference.

I'm glad you responded though because this just has to be the issue, I can't see how it could be anything else. I must have a hole in the 50 - 80 hz range. It also makes sense why Audyssey set my W22's to 60hz crossover when I had the sub in a different spot which didn't output as much. According to Axiom the W22's will do 60 hz without more than 3db loss, so perhaps they should be set there.

Perhaps I will go to Best Buy and buy a small sub to test with, see if it can fill that hole. My only concern is if I just split the signal and feed both subs, the smaller one may get overdriven at high levels, unless there is a way to send the small one a certain frequency range.




Posted by: bridgman

Re: Major sub issues - 11/18/09 02:27 PM

I would place the sub right behind the couch, a couple of feet away from the wall, and see if that helps. The AVS post indicated you had the sub in the back left corner; that seems problematic since the couch appears to be roughly centered in the room (front to back).

If your seating position is on the left seat of the couch (furthest from the wall), putting the sub against the wall will leave you in a null, but putting the sub too far from the wall will result in a frequency dip as well. I'm thinking maybe 2 feet from the wall would be best.

Note that with your room size and construction even a foot or two will make a big difference, so your sub crawl will have to be much more precise than normal, ie you can't stick your head close to the wall (a foot or two away so you don't bang it), hear bass, and then stick the sub right against the wall and get good results.

Good luck. You will get it worked out. You'll need multiple subs to get decent bass in all the listening positions but most of us only care about getting good bass in one seat anyways ;\)
Posted by: MarkSJohnson

Re: Major sub issues - 11/18/09 02:49 PM

Spud, I haven't read the AVS thread, but I can tell you that people frequently underestimate the room itself in seeking good bass.

I have a square room and get get 20dB swings by moving the meter a foot and a half because I have nasty nulls (places where the bass waves cancel each other out).

So relax, You don't need a new sub. Only a new house!!

Well, start by trying the sub crawl first.... \:\)
Posted by: Potatohead

Re: Major sub issues - 11/18/09 02:52 PM

^ Well, here is how it is now:

I like to sit in the right side of the couch, which is basically right against the wall, which is where I placed the sub to do the sub crawls (about 18" from the wall, firing toward the screen. My head is only about 18" from the QS8 but with level adjustment sounds the same as the other one. I currently have the sub on the other side of the loveseat than what is shown in the pics, closer to the A/V equipment. The back half of the room sounds not too bad especially close to the walls, the front half is severely lacking, but like you said I do not care about up there.

Now, I do not mind moving the couch into the center of the room at all, but I just do not seem to be getting as much bass there. Maybe what I should do tonight is put the sub right in the middle of the room about four or five feet from the back wall, and do the crawl again. I think I am getting the most response in that back corner because the ceiling is lower there as well. Maybe I should place it somewhere with a little less db, but then turn the gain up a bit to compensate.

I guess it's back to experimenting tonight... Darn work strikes again.

EDIT :

Mark, thank you for that. It's good to know I'm not alone in this, there are definate db swings in my room as well. It seems this is totally normal, I just want to find the best solution. Without boards like this... Man, I couldn't imagine.
Posted by: Wid

Re: Major sub issues - 11/18/09 03:01 PM

One thing you do not want to do is sit in the middle of the room, you will have bass nulls for sure.

Have you tried the sub in a front corner?
Posted by: Murph

Re: Major sub issues - 11/18/09 03:04 PM

Corner placement helped my square room a good deal. Unfortunately, the sub crawl resulted in my best placement options as being roughly 1/3 in the middle of the room between the couch and the TV wall. Not something that would sit well with my wife for too long.
Posted by: bridgman

Re: Major sub issues - 11/18/09 03:22 PM

 Originally Posted By: Potatohead
Now, I do not mind moving the couch into the center of the room at all, but I just do not seem to be getting as much bass there. Maybe what I should do tonight is put the sub right in the middle of the room about four or five feet from the back wall, and do the crawl again.


Bad assumption on my part - I guessed that you sat in the left seat of the couch (closest to centerline of the screen) which would be roughly centered in the room L-R. As others have said, being in the center of the room is a Bad Thing if the sub is by the wall. Being in the center of the room if your sub is also centered is fine - you just don't get bass by the walls ;\)

Just checking - when you did the sub crawl did you actually have the sub sitting up in your preferred spot on the couch ? It doesn't need a beer but it should be sitting *exactly* where you do.

IMO having the couch by the wall like you do now is best, but I think you'll want the sub very close to the couch for best results. If you sit by the wall then I would try the sub by the wall, either right behind the couch or right in front of it with a cushion for your feet ;\)
Posted by: Potatohead

Re: Major sub issues - 11/18/09 03:33 PM

I did the sub crawl with it on the ground. I could place it on the couch I guess, I'll try that tonight.

There is room in the back corner directly behind where I sit. I do get decent response there but not quite as good as the other corner by the A/V equipment, again I assume because the ceiling is higher. I would actually prefer it here because it's out of the way and behind the door when it's open. I also don't know if it makes any difference at all but having my equipment 12" from the sub doesn't exactly appeal to me either.

Hmm, five more hours and I can start experimenting again.
Posted by: Potatohead

Re: Major sub issues - 11/18/09 03:35 PM

 Originally Posted By: wid
One thing you do not want to do is sit in the middle of the room, you will have bass nulls for sure.

Have you tried the sub in a front corner?


The very first place I put it was about 1/3 of the way back from the front wall, on the side wall as it makes a great end table for my loveseat. I wasn't getting much impact which is what made me start this whole process in the first place. I figured this thing was overkill and I could place it anywhere and get good results, which I am clearly finding out, is not the case.

When I did the sub crawl, there is no impact near the front wall in either corner, at all.
Posted by: bridgman

Re: Major sub issues - 11/18/09 03:59 PM

If all else fails, putting a cushion on the sub and sitting there usually works \:D
Posted by: cb919

Re: Major sub issues - 11/18/09 04:26 PM

Apologies if this was already covered and I missed it - but have you checked that the sub doesn't have any kind of crossover filter engaged? Is it possible your W's are crossed at 80Hz and your sub is filtered above 60Hz creating that hole in frequencies you are experiencing?
Posted by: tomtuttle

Re: Major sub issues - 11/18/09 04:32 PM

 Quote:
I did the sub crawl with it on the ground. I could place it on the couch I guess, I'll try that tonight.


Good. This may make a big difference. Dan's observation about disengaging the sub crossover is very good, too.

It's GOT to be a placement issue.
Posted by: Potatohead

Re: Major sub issues - 11/18/09 05:24 PM

The sub crossover is disengaged, and the knob is turned up all the way (200 hz I believe) for good measure. I have the phase set at 0.

As I said in the AVS thread, I was able to get the sub to crank out some serious couch-shaking last night, but I had to crank the gain, its level was way higher than the rest of the speakers.

I do have the Denon Bass Setting to "LFE", which is says reverts all LFE from any speakers set to "small" and passes it to the sub. This seems to me to be the correct setting as all my speakers are set to small. There is also an "LFE + Main" setting which sends ALL LFE info the sub, regardless of speaker size setting, but in my case I don't think it should matter since they're set to small anyway. I can't remember what I have the low pass filter in the receiver set to, although default is 80 hz and I doubt I changed it. Maybe I should try 90, or even 100.



Posted by: Micah

Re: Major sub issues - 11/18/09 10:19 PM

 Originally Posted By: jakewash
The chest thing is said to be around 60 -90hz and the sub is busy playing ALL low frequncies and smoothly.



Thank you for making this point. This is precisely why I leave my M80's set to large even when I have a subwoofer. Expecially a subwoofer designed to dig really deep like the EP800 is. We've already discussed the fact that subwoofer designs are all trade-offs. You trade this for that. With subs like the EP800 tuned to hit 12 hz in a room, you give up some of the ability to do 60 - 90 hz really well. This is the reason some cheaper subs costing only a few hundred dollars seem really impressive as far as slam goes. They might not play much lower than 25 hz, but they can hit 60 hz like a M1 Abrams tank slamming throught your living room wall at 80 miles per hour!

I still say it's personal preference. But for me, the M80's take care of the slam much better than the EP800 did.
Posted by: HAY

Re: Major sub issues - 11/19/09 12:01 AM

I see you had the phase at 0 but have you played with it back and forth in the different locations? Sorry if you answered this in the other thread, didn't read it.

Also, when you were saying the gain was way up, is that on the receiver you're referring to? If so, it could be the signal just needs to be cranked on your receiver? And I don't think that should be an issue, not ideal but it should harm anything...chime in experts \:\)
Posted by: Potatohead

Re: Major sub issues - 11/19/09 01:53 AM

Well, I feel like a bit of a dork (as if that isn't obvious anyway ), as I decided to just start from scratch tonight, and noticed I had the low pass filter in the receiver set at 250 hz . I guess I raised it to max for the Audyssey calibration and forgot to reset it back. I changed it down to 80 hz and noticed a decent difference, especially in the front which I was complaining about earlier. I guess with the filter that high, the fronts aren't getting a full range.

After all this I re-did the sub crawl, and decided to leave it where it is. It's 10 - 12 db higher than other areas of the room there and is mostly not in the way. I re-ran Audyssey, bumped it a couple db, and I really think that is all I can do with it.

I think the best course of action from here is to purchase another, smaller sub in the future, and probably place it in the other rear corner. I'm just annoyed I sold my old one before testing this all in the first place. If I do this though, is there any way to limit the amount of LFE sent to it? I guess it would be a high pass filter which would limit the lows so I don't overdrive it while the SVS is walking in the park.



Posted by: Potatohead

Re: Major sub issues - 11/19/09 03:15 AM

On that note, does anyone have an EP175 they want to sell?


\:\)
Posted by: CV

Re: Major sub issues - 11/19/09 03:43 AM

 Originally Posted By: Potatohead
On that note, does anyone have an EP175 they want to sell?


\:\)


You're in luck. Axiom has a subwoofer by that name.
Posted by: ClubNeon

Re: Major sub issues - 11/19/09 09:47 AM

 Originally Posted By: Potatohead
After all this I re-did the sub crawl, and decided to leave it where it is. It's 10 - 12 db higher than other areas of the room there and is mostly not in the way. I re-ran Audyssey, bumped it a couple db, and I really think that is all I can do with it.

You're not looking for the location where the sub sounds the loudest. You're listening for smooth, even bass. If it sounds loud, it may be that there's one frequency piling up which will make all the others suffer.

I think it is the Digital Video Essentials DVD which has some low bass sweeps, which also show the current Hz on the screen. Anything with a bass sweep would work though. While you're doing the crawl listen to the full sweep in each location, it should sound (or even better, measure) equally loud through out. If using the DVD, you can even get an idea what frequencies are being accentuated or lacking. Sort of a poor-man's REW.
Posted by: Potatohead

Re: Major sub issues - 11/19/09 11:11 AM

I have a DVE Blu-Ray disc, I'll check it out tonight.

Just using the test tone in the receiver I only get a 2 db swing, but I guess that's only at whatever frequency the test tone is at.
Posted by: Potatohead

Re: Major sub issues - 11/19/09 11:12 AM

 Originally Posted By: CV
 Originally Posted By: Potatohead
On that note, does anyone have an EP175 they want to sell?


\:\)


You're in luck. Axiom has a subwoofer by that name.


They even have different colors!
Posted by: ClubNeon

Re: Major sub issues - 11/19/09 11:43 AM

 Originally Posted By: Potatohead
I have a DVE Blu-Ray disc, I'll check it out tonight.

Just using the test tone in the receiver I only get a 2 db swing, but I guess that's only at whatever frequency the test tone is at.

If you don't find the bass sweep on DVE, it may be the Avia disc. I have too many calibration discs--basically every one I've ever heard of I've bought.

The test tone from the receiver is broadband noise, it covers the entire range reproduced by the sub. Without a real-time audio spectrum analyzer you wouldn't know if one part of the spectrum is accentuated or attenuated over others. But a sweep will play one frequency at a time, so you can hear how the room responds to each.
Posted by: jakewash

Re: Major sub issues - 11/19/09 01:21 PM

 Originally Posted By: Potatohead
I guess with the filter that high, the fronts aren't getting a full range.
Correct, they were only getting frequencies down to around that crossover and a little lower as it is a roll off not brickwall.

 Quote:
If I do this though, is there any way to limit the amount of LFE sent to it? [\quote]The high pass filter would work but by limiting the lows you won't be able to smooth out the response throughout the room, just run the second sub like the first.


You can download some test tones from Realtraps.com and burn them to CD to check your in room response on the sub.
Posted by: Potatohead

Re: Major sub issues - 11/19/09 01:57 PM

That Realtraps tones looks like something pretty useful, at least if I do that I'll know if I do have a hole. I'll probably try that out tonight as well, can't hurt.

I have been looking into this HSU MBM a little more, seems most people are pretty pleased with it.
Posted by: chesseroo

Re: Major sub issues - 11/19/09 11:56 PM

 Originally Posted By: ClubNeon
Anything with a bass sweep would work though. While you're doing the crawl listen to the full sweep in each location, it should sound (or even better, measure) equally loud through out. If using the DVD, you can even get an idea what frequencies are being accentuated or lacking. Sort of a poor-man's REW.

I've done this before, with my surrounds actually, and it works quite well.
It really gives you an idea of what your ears can and cannot really hear.

In manual measurements there was a low valley in a narrow range in our original listening room, but during the sweep, because the frequencies move along at a relatively fast pace, you cannot pick it out.
One Hz out of so many, or a small range and depending on the dB down may not make an audible difference in music/movie playback with everything else that is going on sonically.
Posted by: BigHonu

Re: Major sub issues - 11/20/09 01:27 AM

I know it is not supposed to make a difference, but did you try and 'aim' the driver in different directions after you placed the enclosure? At this point, it may be worth a try...
Posted by: Potatohead

Re: Major sub issues - 11/20/09 03:46 AM

 Originally Posted By: BigHonu
I know it is not supposed to make a difference, but did you try and 'aim' the driver in different directions after you placed the enclosure? At this point, it may be worth a try...


Funny you mention this, as I was going to bring it up. At least in my room, the driver direction makes a HUGE difference. I'll explain in a minute.

So, thanks to jakewash I burned the CD of the frequencies from RealTraps tonight, and just finished spending 5.5 hours down here messing around. It's a pretty cool thing, the driver extension at 10 hz is pretty comical. Anyway, it let me graph out my findings and what it would accomplish to place the sub elsewhere.

To make a long story short, it was pretty much a bunch of wasted time that the sub crawl didn't tell me already. I did actually find one position that the sub flattened out a bit in, but listening to it with some U-571, I just didn't like it as much, so I put it back where it was. It's amazing to see with the SPL meter just how much one foot can make a difference. Right behind my seating area to right in front could be a 15 db swing in some frequencies, and then in another range it would be the exact opposite. It's no wonder people go mental over this stuff.

The point I wanted to make about the driver direction was that in one place I tested, just by turning the sub 180 degrees, I picked up twenty-four decibals at one point around 57 Hz I believe. With the sub in the "bad direction" I was getting 59 dB (lol) whereas it was 83 the other way.

I do have about 10 dB lulls at about 56 and 78 Hz, which was the same pattern no matter where I put the sub, so it has to be my room. According to SVS's graph the sub does dip a bit at these points, so that probably contributes a bit as well.

One thing I did find odd, was that I am down a decent amount as well at about 95 - 110 hz... I don't know if this is just from coming out of the range of the sub, which level was probably set a bit too high, but I don't really have another explanation for it as the W22's should handle that frequency with ease.

I think the next step is going to be a couple bass traps in the back corners of the room and maybe some panels on the walls. Can't hurt I guess.
Posted by: BigHonu

Re: Major sub issues - 11/20/09 05:07 AM

It seems that in the one spot in my room, the way the driver faces makes a difference as well. That is the only reason I mentioned it.
Hope you can get it worked out!
Posted by: MarkSJohnson

Re: Major sub issues - 11/20/09 06:29 AM

 Originally Posted By: Potatohead
It's no wonder people go mental over this stuff.


Yeah, I was pretty normal until I tried to set up an HT in my small, square room. \:\)

Glad you're making headway, spuddy.
Posted by: Micah

Re: Major sub issues - 11/20/09 09:51 AM

 Originally Posted By: chesseroo
One Hz out of so many, or a small range and depending on the dB down may not make an audible difference in music/movie playback with everything else that is going on sonically.



Uh-hu, I suppose 1 out of 20,000 ain't bad! ;\)
Posted by: ClubNeon

Re: Major sub issues - 11/20/09 10:02 AM

 Originally Posted By: Potatohead
I do have about 10 dB lulls at about 56 and 78 Hz, which was the same pattern no matter where I put the sub, so it has to be my room. According to SVS's graph the sub does dip a bit at these points, so that probably contributes a bit as well.

One thing I did find odd, was that I am down a decent amount as well at about 95 - 110 hz... I don't know if this is just from coming out of the range of the sub, which level was probably set a bit too high, but I don't really have another explanation for it as the W22's should handle that frequency with ease.

I think the next step is going to be a couple bass traps in the back corners of the room and maybe some panels on the walls. Can't hurt I guess.

As I was saying, you get the hole around 60 Hz from the length, and the 93 Hz because of the width. It isn't only the sub's bass which is affected by the room. Any bass which is produced will interact, even that from the W22s. Oh, and an 8 foot ceiling is contributing one more major room mode at 140 Hz.

Definitely start with traps, I wouldn't even worry about the wall panels unless they are nearly two feet thick, they won't be able to capture that low of frequency. Wall panels are used more to control treble reflections.
Posted by: Potatohead

Re: Major sub issues - 11/20/09 01:47 PM

Chris,

Would something like this (the 4" thick, 24" x 48") be a good choice for the corners?

http://www.atsacoustics.com/cat--ATS-Suede-Acoustic-Panels--109.html

I would bridge the corner with them, leaving a gap behind. I could do three of the 24" squared ones as well and stack them, leaving a few inches between, which may look nicer and cover more area.

I am also considering building my own, I have read cutting the fibreglass in triangles and stacking it up in the corner under a frame/fabric works well. Those ones are cheap enough though they just wouldn't look as nice.
Posted by: ClubNeon

Re: Major sub issues - 11/20/09 02:07 PM

Treatments labeled as "acoustic panels" will usually have no effect in the bass range. You want something actually sold as a "bass trap".

You're on the right route with building your own. From that site, try the Roxul Rockboard 60, cut into half and then diagonally, so you get 4 triangles which are 2 feet long on the short sides, and 2 inches thick. The $49 gets you 6 sheets by 4 triangles by 2 inches is: 4 feet thick. So you'd need $200 worth to do the 2 rear corners (really you only need to do 2 corners, as you're trying to break up standing waves between a pair of walls, break the pair, break the waves) from floor to an 8 foot ceiling.

If you want to cover the diagonal between the walls with their acoustic panels, that'll be a good use for them. But you'll need a custom size being 2'10" wide to cover the long side of the triangle.

EDIT: I just found their absorption coefficients for the 4" thick panels. Just as I figured, they're good down to 250 Hz, but fall off quickly after that. If you do want to do the custom one to cover the rockwool, just go with the 1" thick and request that they be made with an open back (even though they don't usually do that for the less than 4" panels).

ADDITIONAL: Their 96"x34"x1", open backed, panels run $212 each. You'll probably just want to stretch your own fabric over a frame. The panel is just for looks anyway, because the rockwool is doing all the work.
Posted by: Potatohead

Re: Major sub issues - 11/20/09 03:28 PM

 Originally Posted By: ClubNeon
Treatments labeled as "acoustic panels" will usually have no effect in the bass range. You want something actually sold as a "bass trap".

You're on the right route with building your own. From that site, try the Roxul Rockboard 60, cut into half and then diagonally, so you get 4 triangles which are 2 feet long on the short sides, and 2 inches thick. The $49 gets you 6 sheets by 4 triangles by 2 inches is: 4 feet thick. So you'd need $200 worth to do the 2 rear corners (really you only need to do 2 corners, as you're trying to break up standing waves between a pair of walls, break the pair, break the waves) from floor to an 8 foot ceiling.

If you want to cover the diagonal between the walls with their acoustic panels, that'll be a good use for them. But you'll need a custom size being 2'10" wide to cover the long side of the triangle.

EDIT: I just found their absorption coefficients for the 4" thick panels. Just as I figured, they're good down to 250 Hz, but fall off quickly after that. If you do want to do the custom one to cover the rockwool, just go with the 1" thick and request that they be made with an open back (even though they don't usually do that for the less than 4" panels).

ADDITIONAL: Their 96"x34"x1", open backed, panels run $212 each. You'll probably just want to stretch your own fabric over a frame. The panel is just for looks anyway, because the rockwool is doing all the work.


If I was going to do a DIY trap I would probably just build my own panel for the front, some wood, fabric and staples is pretty simple.

Problem I have though is I cannot really put this type of trap in the one rear corner, as my equipment is there. Is it possible I may not even need one there as there is nothing to really bounce off of? I could do it above on the bulkhead, and along the bottomside of the bulkhead against the wall instead if I had to.

Lastly, is the Roxul stuff you find in the store (safe and sound) which I used to insulate the room, no good for this? Not dense enough perhaps?



Posted by: ClubNeon

Re: Major sub issues - 11/20/09 03:43 PM

To be effective the corner needs to be filled from bottom to top.

Are you saying you'd build a horizontal trap? That'd cover the resonance modes for the length of the room, and the ceiling to floor, but not the width. Imagine literal waves rolling back and forth between the parallel surfaces of the room. When you have a stack up and down in a corner of the room, waves going front to back, and side to side will come into contact with the most volume of the trap. But waves moving up and down will only catch it slightly. That's not to say that a horizontal trap doesn't help with the up to down mode. To control the two worst room modes though, you need two vertical stacks in two corners. You could put them in the front of the room.

To build a stack you really need the rigid board, so it can support 8' of it's own weight and not compress over time. If you built support shelves every foot, you could go with the flexible stuff, and not lose too much total volume over time.
Posted by: ClubNeon

Re: Major sub issues - 11/20/09 03:49 PM

I just went back and looked at the pictures of your room. Yeah, that doesn't leave you many options. A trap in just one corner, and then a false bulkhead full of rockwool opposite the real one may be your best bet.
Posted by: Potatohead

Re: Major sub issues - 11/20/09 05:52 PM

Ok, hopefully the last question.

I think I am going to build a simple frame, and fill it with Safe 'n Sound. I can build it up to about a foot thick, so it should be dense enough.

Should I do the triangle thing, or should I build it so that I can stand the SnS up inside the frame, and make it about three rows deep (about 10.5"). This would allow me to leave an air gap behind the trap.

I don't know if building a soffit on the other side is something I want to do, it would make it pretty claustrophobic in there. Is there somewhere on the bulkhead side that you can see may benefit from the same treatment? I am thinking the bulkhead to back wall connection may be a good idea, although it's kind of short. I could also build about an 8 - 12" deep trap between the equipment and the sub(just to the right of the equipment), which is about 18" wide space. Being a couple feet from the corner though I don't know if it'll help.


Posted by: ClubNeon

Re: Major sub issues - 11/20/09 07:12 PM

An air gap isn't as good as material all the way to the wall. The only reason some products are designed to employ a gap is to have the sound pass through them twice. But if they were solid all the way to the wall they'd be even more effective. Just be less flexible in their installation and cost more.

The triangle into a corner has the largest volume for the smallest floor space. Instead of a full squared off soffit, picture a triangle which comes 2 ft across the ceiling and 2 ft down the wall. It shouldn't intrude too much.

That small of a trap won't do too much. When dealing with very small traps they need to be tuned exactly to the frequency you want to absorb, and make use of some advanced techniques like Helmholtz resonators. The reason the traps need to be big is because the wavelengths at these frequencies are that long. A 60 Hz sound wave peak to peak is 18.6 ft long.
Posted by: JohnK

Re: Major sub issues - 11/20/09 10:19 PM

Chris, better cut those room mode frequencies in half to allow for the round trip.
Posted by: fredk

Re: Major sub issues - 11/20/09 11:58 PM

I'm just catching up on this thread, but have a couple of comments.

For that null in the 90-110 Hz range, I would look to your M22s as they are contributing most of the sound in this range. Try playing with their positioning if you can.

For bass traps to be effective, you need them as thick as possible and you need as many as possible. For the corners I would go with 6" thick minimum, and would fill the corner solid as Chris suggested if you can. Make sure the stuff you use is a minumum of 3lb/cu.ft. in density or its useless for LF.

You need to fill all 4 corners at a minimum, and if you can, also treat wall/floor and wall ceiling intarfaces as well.

You might be better served to spend the money on a second sub. From reading about others here that have done this, it goes a long way in smoothing out the frequency response.
Posted by: Potatohead

Re: Major sub issues - 11/21/09 01:56 AM

 Originally Posted By: fredk
I'm just catching up on this thread, but have a couple of comments.

For that null in the 90-110 Hz range, I would look to your M22s as they are contributing most of the sound in this range. Try playing with their positioning if you can.

For bass traps to be effective, you need them as thick as possible and you need as many as possible. For the corners I would go with 6" thick minimum, and would fill the corner solid as Chris suggested if you can. Make sure the stuff you use is a minumum of 3lb/cu.ft. in density or its useless for LF.

You need to fill all 4 corners at a minimum, and if you can, also treat wall/floor and wall ceiling intarfaces as well.

You might be better served to spend the money on a second sub. From reading about others here that have done this, it goes a long way in smoothing out the frequency response.


"Unfortunately" I have the in/on wall version of the 22's, so I can't move them. I can physically feel them putting out decent bass when the sub is off, so I think I probably just had the sub too high in level when I performed the test at that higher frequency, which I only did once. I was just charting the graph so volume wasn't really important, so I didn't bother to change it when I moved the sub around. I had the LPF set at 90 hz, so it makes sense to me.

After easing my mind of this for a few hours tonight and watching the hockey game, I think I do (and my wife, surprisingly) agree with you in that the next step should probably be a second sub. Why spend even a few hundred bucks and hours of my time on some traps which don't look too hot, when I can put that towards a second sub which will help more anyway? I think I'll do the traps after that, and first reflection panels. I think those things look cool... Kind of hardcore \:\)
Posted by: BigHonu

Re: Major sub issues - 11/21/09 02:12 AM

One more sub! You have a smart wife!
Posted by: fredk

Re: Major sub issues - 11/21/09 09:46 AM

+1 on the smart wife!

FWIW, trapping works very well for stuff over 100Hz and this can still affect bass a lot. Since you can't move your M22s around, that corner trapping may help out with the null around 100Hz.

I spent a lot of hours looking for a solution to help with the sub 100Hz stuff including a studio design site, and its just not that easy.

Another thing you can try if you have nulls around the crossover area is to run the M22s full range and set your AVR to LFE + mains. This is what Earl Geddes does (his mains roll off at around 50Hz) to help fill in the mid bass. There are a couple of members here who do this as well and say they get good results.

If you are serious about tackling this, it is worth while to figure out REW. Its really not that bad once you get it set up.
Posted by: Potatohead

Re: Major sub issues - 11/22/09 04:37 PM

Audyssey set my W22's to small, so I think I'll just leave them there. I watched Valkyrie Blu-Ray last night and in a word, it was fantastic. The scene at the beginning in Africa, and then the bombing scene when they are in the shelter with his family... Just amazing, hard bass. The shelter scene I was not expecting and I almost spilled my drink. I think what I did certainly helped, although a second sub is a definate possibility down the road, same with the trapping.

I am having a very small issue with my Panasonic BD-55 dropping the HDMI link once in a while, maybe once every couple movies, but then it picks it up again within seconds... Kind of weird. It was really bad on one input in the Denon, tried another and it's 90% better. I bought another cable as well and will try it out if it doesn't sort of fix itself. I have a 6' run from the BD-55 to the Denon and 20' to the projector... Perhaps this player just doesn't like longer runs.

Anyway, at this point I am 90% satisfied and can start to enjoy. Thanks again everyone for your help.


Posted by: Potatohead

Re: Major sub issues - 11/24/09 04:05 PM

Quick question:

Currently have the crossover for the W22's and LPF in the receiver both set at 80 hz, the W22's are set to small. If I set the LPF to 90 in the receiver, but leave the crossover at 80, does this accomplish anything? Seems to me it would just be like moving both the LPF and crossover to 90, unless you had your speakers set to large.
Posted by: jakewash

Re: Major sub issues - 11/24/09 04:38 PM

LPF= Low Pass Filter?

My Denon has a LFE setting seperate from the crossover and I seem to remember reading it is recommended to run that one around 120hz, just in case the sound engineer added some LFE that high up in the range and small speakers wouldn't do it justice so it then is routed to the sub.
Posted by: Potatohead

Re: Major sub issues - 11/24/09 04:54 PM

Yeah, low pass filter, it's under the "Bass Setting" in my Denon.

That makes perfect sense, I'll try that. The fronts would still produce sound in the non - LFE channel below the LPF setting, so some overlap there can't hurt.
Posted by: JohnK

Re: Major sub issues - 11/24/09 09:56 PM

Tater, there wouldn't be any "overlap"; the setting for the low pass filter on the LFE channel affects only that, and none of it, regardless of what frequency you pick for the setting, is played by the speakers.
Posted by: Potatohead

Re: Major sub issues - 11/24/09 10:04 PM

Right, perhaps my terminology was incorrect. I just meant numeric overlap. I bumped the LFE setting from 80 - 100 hz.

I can't get enough of this bombing scene in the Valyrie blu-ray. The initial impact of the first bomb is just awesome, I've watched it about six nights in a row now... hah.