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Where to put bass traps with speakers close to corners?

post #1 of 23
Thread Starter 
Hello,

I have some OC703 and will be making some some absorption panels and possibly bass traps with them for my room. I have all inwall speakers and the fronts are very close to the outside wall. Probably only 4" between the outside of the wall and the side of the speaker. I plan on cutting each 2x4 panel into 8 triangles and using them in the corners. That will make the trap about 12" thick.

I was going to use a mirror and hang 2" thick panels at the first/early reflection points for my front and rear speakers.

Can I just build triangle bass traps in the corner and stop a few inches below and above the speaker??

Will that negativity affect the sound with too much absorption directly above and below??

My room is 22 feet long and my seating is at 12'. Do I need traps for the rear corners as well??

I have attached a picture so it is easier to see what I am talking about. Thanks for the help.

CanadianZ
post #2 of 23
Before you go any further, I would contact GIK Acoustics or try to PM Ethan Winer here on this site.

Take this with a grain of salt but for one, your front stage looks way out of spec.....I dont like how the FL and FR are up so high and close to the side wall. The center looks ok if you're sitting on the floor. tongue.gif

To your original question, building traps below and above those speakers is going to give you problems IMO.
Edited by Yosh70 - 6/14/13 at 2:05pm
post #3 of 23
Thread Starter 
Ceiling height is under 7' and front speakers are ear height. Center speaker is low but needs to be to fit under the screen. The screen is painted on the wall so in order to fit it I had to sacrifice speaker placement somewhat.
post #4 of 23
Quote:
Originally Posted by CanadianZ View Post

Ceiling height is under 7' and front speakers are ear height. Center speaker is low but needs to be to fit under the screen. The screen is painted on the wall so in order to fit it I had to sacrifice speaker placement somewhat.

I've had identical LCRs both above and below display, with care either can work.

In this scenario, I may have chosen above the screen, angled down toward the seating. But this above and angled down and in, pro audio style, ... is often my preference. Your bottom of screen center may work, however I prefer all my LCRs in one uniform horizontal plane.
post #5 of 23
Thread Starter 
Quote:
Originally Posted by FOH View Post

I've had identical LCRs both above and below display, with care either can work.

In this scenario, I may have chosen above the screen, angled down toward the seating. But this above and angled down and in, pro audio style, ... is often my preference. Your bottom of screen center may work, however I prefer all my LCRs in one uniform horizontal plane.

We start with the ideal theater and build with what we have to work with. I made sacrifices along the way for certain things. (ie room size) Yes the LR speakers are close to the outside walls. If they weren't the screen would be too small. Yes the center in not ideal, I could not afford a high end acoustically transparent screen and place it in the center of the wall. I did the best I could with the room and funds I had.

THanks, CanadianZ
post #6 of 23
Quote:
Originally Posted by CanadianZ View Post

Hello,

I have some OC703 and will be making some some absorption panels and possibly bass traps with them for my room. I have all inwall speakers and the fronts are very close to the outside wall. Probably only 4" between the outside of the wall and the side of the speaker.

Big mistake - putting the L & R speakers in the corners like that.

I can't see trying to fix a mistake like that by trying to compensate for it. Move the speakers in a foot or two, and put the bass traps in the corners where they belong.
post #7 of 23
The speaker placement is what it is.

Regarding where to place bass traps; I'd massively treat the rear wall behind the LP. I'd make them as thick as possible. Depending on how close the rear wall relative to the LP is, would determine if the treatment would warrant some measure of return treatment/facing, slats, scattering or full diffusion.
post #8 of 23
Thread Starter 
Quote:
Originally Posted by FOH View Post

The speaker placement is what it is.

Regarding where to place bass traps; I'd massively treat the rear wall behind the LP. I'd make them as thick as possible. Depending on how close the rear wall relative to the LP is, would determine if the treatment would warrant some measure of return treatment/facing, slats, scattering or full diffusion.

Thanks. Finally someone understands that the room is what it is and I am trying to make the best out of a less than ideal situation. Which is really what we all do with the circumstances we have to deal with.

Anyways, the room is 12w X 22.5l. The seating is at 12' and its a single sofa.

I can easily treat the rear wall with doubled up 703( for a total 4" thick)

Should I just treat the top half above the level of the couch or should I do the entire wall??

Thanks for the help. I can take some more pics tonight and post them as the room is finished.

Thanks, CanadianZ
post #9 of 23
Quote:
Originally Posted by CanadianZ View Post

Thanks. Finally someone understands that the room is what it is and I am trying to make the best out of a less than ideal situation. Which is really what we all do with the circumstances we have to deal with.

Others understand as well, however we're all used to applying best practices, sharing what we've learned with other enthusiasts.


Quote:
Originally Posted by CanadianZ View Post

Anyways, the room is 12w X 22.5l. The seating is at 12' and its a single sofa.

I can easily treat the rear wall with doubled up 703( for a total 4" thick)

Should I just treat the top half above the level of the couch or should I do the entire wall??

It depends ... your seating is about 10' off the rear wall?

4" of 703, spaced 4" off a boundary is a good treatment for broadband reflections. Typically, that'd be the approach for first reflection points at sidewalls, ceiling etc.

For bass trapping, I'm curious what sub(s) you're using, where they will be located.

Again, 4" of 703 spaced significantly off the rear wall, like 8"-10", would make a superb bass trap. But if you're that far away, I'd likely prefer some scattering or diffusion on the front of the bass trapping ... this retains the precious MF/HF spectra, otherwise one could easily over deaden a room.

If you're right adjacent the rear wall with your seating, then I'd consider a thick treatment approach.


Pics would be helpful.
post #10 of 23
Quote:
Originally Posted by CanadianZ View Post

Anyways, the room is 12w X 22.5l. The seating is at 12' and its a single sofa.
Placing the seating at one of the odd divisions (thirds, fifths) of room length will help smoothen frequency response (less peaks & dips). Can you move your sofa so that it is 13.5' or 15' from the front wall?
post #11 of 23
Quote:
Originally Posted by CanadianZ View Post

Thanks. Finally someone understands that the room is what it is and I am trying to make the best out of a less than ideal situation. Which is really what we all do with the circumstances we have to deal with.

Sacrificing the audio the way you did just to have a "big" screen is not what should've been done IMO.
With the reflection that your front speakers have to deal with and the CC just above the floor (I hope its at least aimable?) the audio portion of your theater will be one big mess.

I'm not sure why a Plasma or LED TV wasn't considered..... would've been fine for that room and then the audio wouldn't have to suffer.

Curious tho, when you say the speakers are "at ear level", are you talking about the bottom of the in-wall.....because ear level in that pic looks like over 5' from the floor.
You sitting on stools perhaps? wink.gif
post #12 of 23
Quote:
Originally Posted by Yosh70 View Post

Curious tho, when you say the speakers are "at ear level", are you talking about the bottom of the in-wall.....because ear level in that pic looks like over 5' from the floor.
Keep in mind that the ceiling in that pic is under 7' according to the OP, so the L/R speakers look like they're between 3-4' high.
post #13 of 23
Quote:
Originally Posted by sdurani View Post

Keep in mind that the ceiling in that pic is under 7' according to the OP, so the L/R speakers look like they're between 3-4' high.

Yep, I realize that sdurani.....but the top of that speaker where the tweeter should be situated looks to be 5'+.....no?
post #14 of 23
Quote:
Originally Posted by Yosh70 View Post

....but the top of that speaker where the tweeter should be situated looks to be 5'+.....no?
Don't know if the tweeter is at the top of the speaker. Since the cut-out looks tall and skinny, I was going to guess a MTM design. Either way, it looks close enough to ear height that I don't see it as a problem. YMMV.
post #15 of 23
Thread Starter 
Okay some clarification and pictures. I remeasured the room. 21' long 11'2" wide.
The seating is 12' to ear from the screen. Couch back is ~1' thick and there is 8' behind the couch.
The tweeter level of the LR is at 45" above the floor and ear level on the couch is ~38". (speaker config is woofer tweeter woofer) The side of the speaker is 3" from the wall and the side of the woofer (within the speaker) is 5.5" form the wall.
I wanted a bit higher because sometimes I do have bar stools set up behind the couch for hockey or UFC events. (a sacrifice I know)

The speakers are Mordaunt Short and the sub is an SVS PB 1000.

Yosh70: I did make some sacrifices to have the larger screen size. I really wanted a big screen. You have excellent equipment but IMHO your screen size is too small unless your seating is 7-8' from your screen. smile.gif




Thanks for all the advice, CanadianZ

PS As you can see from the picture of the back of the room this is a shared space/ play room. It is about sacrifices after all. wink.gif
post #16 of 23
Since the speakers are 3 inches away from the side walls, I would place 3-inch thick absorbers along the side walls, butted up against the front wall (at speaker height). Reflections that close to the speakers tend to muddy the direct sound. Put another one of those panels on the floor below the centre speaker, for the same reason.

If you can put a rug (with thick padding underneath) on the floor in the front part of the room, that would help as well. Bass traps in the corners (above and below the speakers) can't hurt.

Finally, I would place the subwoofer directly behind the couch, exactly at the midpoint of room width. This will knock out a room resonance around 51Hz, improving the bass across your entire seating area. The nearfield placement will let you hear more of the sub and less of the room, giving you tighter/smoother bass.
post #17 of 23
Thread Starter 
Thanks for the reply.

I've already purchased 2" 703. I will but that up against the wall like you mentioned. Hopefully the angle of incidence will help it with absorbing a little deeper than 2" normally would.

The flooring is carpet over thick underpaid so that should take care of floor reflections.

Unfortunately I don't think I can place the sub behind the couch. It pretty much has to stay up front as behind te couch is a bit of a play area. I can move it along to front wall a bit to see what sounds best.

I was going to build some " super chunk " style bass traps as I have a lot of 703 that will be left over. How close to the bottom of the LR can I bound them?? I was thinking I should leave at least a few inches so it doesn't deaden the sound too much.

What can I play to test my sub in various locations?? Should I use a test tone file or just play some bassy music movie??

Thanks again for all the help. I really want to refine the room as much as I can and these are great suggestions.

CanadianZ
post #18 of 23
You could listen to music, but some measuring capability such as OmniMic (or equiv), would allow you to ideally mate the mains output, with that of the sub.


There exists an ideal time relationship between the two signals, and with the distance setting, you'll be able to either tame a horrible peak, or fill in an empty canyon. Also, you can find the ideal placement and EQ setting for the LF response. This is significant, especially if you don't possess Audyssey (or equiv) goodness. Both work even better.


Superchunks are fine. However, given a finite amount of material, perhaps they would likely do best spread across the most surface area ... ie, more material over more area, trumps fewer deeper well executed traps. A four inch thickness spanning a corner is very effective. The gap is key, as is surface area "seen" by the LF energy. Your rear wall, up high ... all across would be a great start.

If the drivers exciting the room (below transition F) are all upfront, then perhaps the treatment is best served in the rear first. If excessive energy is removed, steps taken to mitigate this are easy. Then add more elsewhere too.


The sidewall panels, IMO, would be best out a ways to take full advantage of the edge effect. In my experiments with this very situation, it's often best to allow the incident energy encounter the thickness of the side edge,..in addition to the full front of the panel too. I'd ray trace and determine where the panel would be best placed so the main sidewall hit is attenuated by the panel side, and allow the remaining energy to encounter the front. Grazing angles don't absorb and catch as one would like, so care must be taken. I like thin divider wells too to "catch" energy.

Anyway, bring them out from the corner IMO, so the edge helps too.

Ideally sidewall panels need to be min 4", w/4" gap. If you merely want 4" on the wall, that's ok too if that's the width you wish to forfeit. Maybe 6" on wall, no gap.

Be mindful, as oft stated ... any reflected energy needs to be spectrally as identical as direct sound,....otherwise you're merely filtering the reflection. That said, thick and effective (grazing angles), or diffuse, scattered, or redirected. When it comes to early/first reflections, if you absorb, absorb it all.



These two below are significant;

---The issue, the total energy at the LP, is the combo of the direct field, and the reverberant field. The closer any object in the room is that affects the wave launch off the drivers, the more important that object is. That wave-like recreation of the recording, needs to encounter as few physical disturbances as possible early in it's flight. Your sidewall areas are very important. The room, and it's influence, is overwhelmingly your biggest concern. That said, you're doing the right thing, asking the right questions.


---Treating the room, and addressing the reverberant field, is meaningful because if we delay the impact of this energy, there is sufficient time before the reverberation field has built up. This allows us to hear the direct sound energy relatively free from the reflection effects from the room. Attenuating/delaying this room influence adequately, allows the reverberant sound to become a separate event from the direct sound. This affects imaging, and the intention is to be transported to the recorded event. More realistically, it would be more of a window upon the recorded event...but certainly a step in the right direction.


With the exception of the benefits associated with PVG/Room Gain, the room is quite destructive to the process.


Other than test software, you may try some acoustic bass w/ vocals. Any good driving clear bass lines ... Sheffield Track Record, one of my long time faves (Nathan East is a monster*) Or you could try the opposite approach, subwoofer crawl method. Place the sub in your LP, and move about listening for smoothness. Listen to sdurani, regarding his (selective mode cancelation) placement strategy.


Remember, the room's standing waves and characteristics that influence the sound, are determined by the room’s dimensions.
-The degree of this excitation entirely depends on the loudspeaker's/sub's position.
-The degree of audibility depends on the listener's position.

These above items are very simple, yet quite critical.
The speaker positions determine which modes are excited, and the listening position will determine which modes are heard.


With your bass traps, however you approach them, the room's effects will be lessened. The FR smoother, the decay tighter. When you combined those two attributes, with the careful adjustment of the distance (delay) setting in your AVR/PrePro, the sense of "speed" and clarity will make the whole exercise worthwhile. smile.gif


Best of luck



(*Daft Punk hired him for their current "Get Lucky" track. Solid collaboration. )
post #19 of 23
Quote:
Originally Posted by CanadianZ View Post

I've already purchased 2" 703. I will but that up against the wall like you mentioned. Hopefully the angle of incidence will help it with absorbing a little deeper than 2" normally would.
Since the woofers in your speakers are 5.5" from the side walls, you'd be better off doubling the 2" pieces to get 4" thickness, which will make their absorption closer to broadband. By comparison, 2" thickness will absorb more highs than mids. If you do that, you'll have to play with your receiver's tone controls to restore the spectral balance.
Quote:
Originally Posted by CanadianZ View Post

The flooring is carpet over thick underpaid so that should take care of floor reflections.
Not with a speaker that close to the floor it won't. But if that's not a concern...
Quote:
Originally Posted by CanadianZ View Post

I was going to build some " super chunk " style bass traps as I have a lot of 703 that will be left over. How close to the bottom of the LR can I bound them?? I was thinking I should leave at least a few inches so it doesn't deaden the sound too much.
You'd likely get more value out of that material if you made 6" thick flat panels that straddled the corners (with an air gap behind them) than superchunk traps.
post #20 of 23
Quote:
Originally Posted by CanadianZ View Post

Yosh70: I did make some sacrifices to have the larger screen size. I really wanted a big screen. You have excellent equipment but IMHO your screen size is too small unless your seating is 7-8' from your screen. smile.gif

Yes it is small when placed on that wall....funny tho, a 65" TV even 5 years ago was considered pretty big.

I am 10' feet away and altho the dimensions are not quite "theater size", the pic and clarity more than make up for it.
I also consider the audio portion a more important factor than screen size.......doesn't mean a projector isn't in my future tho wink.gif

BTW, your painted wall/screen, that isn't pure white, is it?
post #21 of 23
Thread Starter 
Quote:
Originally Posted by Yosh70 View Post

Yes it is small when placed on that wall....funny tho, a 65" TV even 5 years ago was considered pretty big.

I am 10' feet away and altho the dimensions are not quite "theater size", the pic and clarity more than make up for it.
I also consider the audio portion a more important factor than screen size.......doesn't mean a projector isn't in my future tho wink.gif

BTW, your painted wall/screen, that isn't pure white, is it?

The wall is painted with RS Maxx-Mudd. It turned out great and compared to a friend of mine that just painted his white mine is considerably better.

CanadianZ
post #22 of 23
Thread Starter 
Wow, I knew when I decided to start treating the room I had some learning to do. I thought I had it all figured out.

Thanks everyone for your help. I am hopefully going to get a chance to apply some of the things I have learned this weekend. You really can't under estimate what a valuable resource a website like this is with some smart passionate people that can help.

Thanks again, CanadianZ
post #23 of 23
Quote:
Originally Posted by CanadianZ View Post

Wow, I knew when I decided to start treating the room I had some learning to do. I thought I had it all figured out.

Thanks everyone for your help. I am hopefully going to get a chance to apply some of the things I have learned this weekend. You really can't under estimate what a valuable resource a website like this is with some smart passionate people that can help.

Thanks again, CanadianZ

Good luck

The area of acoustic science, is the most counter-intuitive aspect in all of audio.
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