# Suggestions for a NON-dedicated home theater



## JimP (May 18, 2006)

Here is my living room/dinning room where my home theater lives. 

Without making it look like a recording studio, (panels in ceiling wall corners and on the ceiling) what can be done to improve the acoustics? With that limitation, would the benefit of adding some bass traps and panels not be significant enough to bother with?

All comments are appreciated.


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## Bob_99 (May 8, 2006)

Well, in my opinion, I would start by measuring and see what the results look like and then go from there. You seem to have a lot of 'soft' furnishings so you may not need too much treatment (just my guess). I'm sure Bryan may give you better ideas.

Bob


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## JCD (Apr 20, 2006)

One thing I saw that could maybe help is to cover that glass table in front of your couches. Also, it may be beneficial to move the speakers in the back farther apart.

Other than that, maybe someone could offer up a different layout, but I can't think of anything without adding some acoustic panels, which don't seem to be an option.

Hopefully one of the guru's will offer up something.

JCD


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## bpape (Sep 14, 2006)

If you can do some bass absorbtion in the real space corners that you have on the floor - even though they're not technically in the listening area, that will certainly help. 

Doing a few panels on wall in the front and rear will also help knock things down a bit.

The biggest issue you have is non-symmetry left to right and no way to treat the wall that's close to make it appear farther away.

Bryan


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## JimP (May 18, 2006)

Bob_99 said:


> Well, in my opinion, I would start by measuring and see what the results look like and then go from there. You seem to have a lot of 'soft' furnishings so you may not need too much treatment (just my guess). I'm sure Bryan may give you better ideas.
> 
> Bob


I've got REW on a dedicated computer.

Which readings would I need to make?


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## JimP (May 18, 2006)

JCD said:


> One thing I saw that could maybe help is to cover that glass table in front of your couches. Also, it may be beneficial to move the speakers in the back farther apart.
> 
> Other than that, maybe someone could offer up a different layout, but I can't think of anything without adding some acoustic panels, which don't seem to be an option.
> 
> ...


What could I cover the glass table with and what will that do? (...and what will it look like?lol)

Regarding those rear speakers, depending on which website you go to, some will recommend close placement for the 7.1 sound field to be correct. I've seen examples of having them further apart too, so I know what you're saying. I think that my preamp manufacturer (B&K) actually recommends them even closer than I have them. But I thought the lazy boy chair between them would help with some of the midbass. I can see that they probably need to be pulled further away from the back wall as I'm probably getting a little comb filtering.

I'm open to a new layout, as I've been trying to figure that out as well.

As to not having any panels, that's not exactly what I was trying to say. I just don't want panels hanging on the ceiling or put up straddling ceiling/wall locations similar to a recording studio. Other than that, I'm open to suggestion. Ideally, I wouldn't mind it as soft furniture or looking like wall art as I kind of liked that look on one of the other threads. Again, I see how acoustical treatments take on a life of their own in some of the other threads and 16 panels later it sounds good. I understand that if you can't do certain things with the limitations I have, then it might not be worth doing at all.


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## JimP (May 18, 2006)

bpape said:


> ...snip...
> 
> The biggest issue you have is non-symmetry left to right and no way to treat the wall that's close to make it appear farther away.
> 
> Bryan


I was playing around with my SMS-1 the other day and by just putting one of my sofa pillows between the mic and the right wall (next to the mic) I could see an obvious change in the frequency response. 

As you said, though, how can you treat that right wall when its essentially windows and fireplace.

One question that I have is for corner treatments, just how much of the corner needs to be treated. With 12' ceiling, I'd rather keep it as minimal as possible.


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## Bob_99 (May 8, 2006)

> I've got REW on a dedicated computer.
> 
> Which readings would I need to make?


 In addition to minimizing peaks and nulls, you want to look at the waterfall plots to get your decay time (20 - 200Hz) down to something reasonable. For HT you would want lower numbers and for music, slightly higher but there are differences of opionions on that. Actual numbers depend on the room size and to be honest I'm not sure what number you would have for that room. For my room (17'x34'x9') I'm at about 275ms (70 - 200Hz) and I do mostly HT.

Bob


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## JimP (May 18, 2006)

thanks Bob,

I presume I should only use one speaker (probably the one closest to the sub) and the sub, right?

Or do I use all 7 speakers and the sub?


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## Bob_99 (May 8, 2006)

In acoustics, I find that there are as many different theories and opinions as there are speakers. Having said that, here's my thoughts. I would measure:

Sub + Left
Sub + Right
Sub + Left + Right

and look at the results. I feel that the center deals mainly with dialogue and the left and right surround deal mainly with environmental effects, so they can be treated essentially for first reflections which can be easy to do depending on the setup. With the sub and mains, you are dealing with bass absorbtion and first reflections. The measurements will give you an idea of what needs to be done and then you decide on how much you want to do. Room treatment in a non-dedicated theater is a challenge but if you like doing puzzles, then it's kind of enjoyable trying to encorporate treatment into the decor.

Bob


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## JimP (May 18, 2006)

Given everything else going on in my life at the moment, tinkering with non-dedicated home theater acoustics is a nice diversion. Should be an interesting challenge and I'll have some fun with it. 

With any luck at all, I'll get to run some test this evening.


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## Ethan Winer (Jul 21, 2006)

Bob_99 said:


> In acoustics, I find that there are as many different theories and opinions as there are speakers.


LOL, true. But what usually matters the most is the bass response with sub + L + R all playing the same test signal at once.

Most music has all bass instruments panned to the center. So when music plays, the low tones come from the left and the right, and the receiver's bass management routes some of that to the sub. So if you measure with the test tones going to L+R, and leave the receiver's bass management intact, your measurements will most closely correspond with what happens when music and movie sound tracks are played.

--Ethan


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## Bob_99 (May 8, 2006)

Ethan et al,

My comment was not to disparage anyone's opinions but merely to point out, that amongst a wide spectrum of thought and for better or worst, those were my thoughts. And my wife reminds me often, that I am seldomly as right as I think I am.

:bigsmile:

Bob


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## Fincave (Apr 20, 2006)

Just to throw something into the mix here. I realise that people without dedicated rooms, myself included, are not always all that keen on hanging panels up as they can be rather ugly. Artistic acoustic panels would be a lot more attractive and so I did a bit of searching and came up with this link. I must stress that I do not have any knowledge of how effective their panels nor the reliability of the company in question, I do however really like the idea. I really do like the idea of being able to choose what pictures or art would be on the panels, it would make them a lot more personal.


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## bpape (Sep 14, 2006)

As you found out with the pillow, while corners are a good place for overall treatment, they may not be the optimal ones to deal with a specific frequency related problem. In your case, you're experiencing some SBIR issus. To make it worse, only one speaker has that so there will also likely be some additional cancellations between left and right.

Bryan


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## Sonnie (Apr 11, 2006)

Jim... :time-out: Quit procrastinating... get off some of that money... :spend: and go ahead and add on to the back of your house and build that dedicated HT room... or wall in that room and have a separate dining room and foyer. :nerd:


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## JimP (May 18, 2006)

Hi Sonnie :bigsmile:

Building a dedicated theater has been in the back of my mind for a while. I just enjoy sitting in my living room and watching TV shows where I think of a dedicated home theater more suited for watching movies.


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## bpape (Sep 14, 2006)

A dedicated space doesn't have to be done up all fancy and proper. Just a dedicated space designed for audio video is the key. You can still just have a couch and a couple recliners, bar in the back, etc. and keep it more informal.

Bryan


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## JimP (May 18, 2006)

As long as its 22' X 30'. 

With any luck, I'll run the sweeps Sunday afternoon and post the results.

I've been thinking about something that might be a problem.

Should I position the mic where I normally sit as this position also has a pretty bad null.

Or move it over a few feet where the null is mostly gone.

Or do both charts.


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## bpape (Sep 14, 2006)

Measuring anywhere that you're not sitting tells you nothing. The only place that matters is where your ears are.

Bryan


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## a1161979 (Aug 26, 2007)

Maybe not appreciated but i have a little problem and, um, well, i would love to see a photo of you equipment rack :waiting:

Please....


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## JimP (May 18, 2006)

Here are the REW graphs.


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## JimP (May 18, 2006)

a1161979 said:


> Maybe not appreciated but i have a little problem and, um, well, i would love to see a photo of you equipment rack :waiting:
> 
> Please....


Lets handle this with PMs.


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## bpape (Sep 14, 2006)

38-45 is either a length issue with mains or a sub issue. The other null that shifts from 160 to 105 is an issue with SBIR/placement due to non-symmetry of the mains in the width dimension.

Waterfalls are predictably long for a room that large and untreated in the bottom end. Try to redo the vertical scale to show peak to -60db from peak for a better idea of what's actually happening. Also, try to redo the horiz scale to show 20-300Hz.

Bryan


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## JimP (May 18, 2006)

38-45 is related to distance from right wall as I can move the mic over a couple of feet and eliminate it. This is the null that I was aluding to in my question about mic placement. I was also able to influence this null by placing a sofa pillow on the wall side of the mic.

I'll have to rerun the sweeps tomorrow to get the changes you suggested. Might have to be tomorrow night.

Thanks for the feedback.


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## bpape (Sep 14, 2006)

OK. I was just looking that those dips didn't change with Left/Sub, Right/Sub, or LR/Sub. I neglected to mention the seating position issue since it was my understanding that you weren't moving seating - my bad.

Bryan


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## JimP (May 18, 2006)

As I normally run my subwoofer 3dbs hot, should these test be run with this setting or should I change it so the sub is flat relative to the mains.


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## bpape (Sep 14, 2006)

Start out with everything calibrated as it should be. After we get things smoothed out and the best we can, then if you want to add a little house curve or a couple extra db on the sub, that's fine. 

Bryan


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## JimP (May 18, 2006)

How's this?


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## JimP (May 18, 2006)

Any suggestions?


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## bpape (Sep 14, 2006)

Got one for just the sub?

Bryan


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## Sonnie (Apr 11, 2006)

Jim... I know you have two subs. Is this both subs?

Also, it would be good to see the response of just the sub, as Bryan suggest.

I can tell you that it's going to be almost next to impossible to do anything with that null you have between 30-50Hz with any kind of treatment or equalizing. 

I had a similar issue in my room, the only solution was adding another sub in the rear, but then I had to cross if over lower to keep away some cancellations at higher frequencies.


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## JimP (May 18, 2006)

Sonnie,

Boy, you've got a good memory. 

Although I have two identical Velodyne HGS-15 subs, the plots are of only one located between the display and the right front speaker. I've played around with these subs in all sorts of configurations and concluded that using just one up front with a Behringer DCX2496, nets me a cleaner sound. I can eliminate most of that null by running the second sub at the rear with the null notched out, but then when I move out of the primary listening position, I have a monster 35-45 hz peak. So that didn't work as one would expect. Interesting enough, when I had rear sub up front opposite the center channel, the null broadened. I think this is one of those room issues that I'm just going to have to live with.

At this point, I'm pretty sure that I'll be selling the rear Velodyne sub (eyes mist) and depending on a particular upcoming review of the SVS PB13 Ultra (friend with a good ear and substantial technical background), I may be replacing the front one as well.

I'll run a sweep of just the sub tomorrow and will post it.


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## JimP (May 18, 2006)

Subwoofer only


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## Sonnie (Apr 11, 2006)

I know you say you have a nasty peak elsewhere when you run that other sub in the rear... so what does that elsewhere look like with just the one sub up front? Can you run another response measurement from that location where you were getting the big peak? I'm wondering what the lesser of two evils will be.


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## JimP (May 18, 2006)

With just the front sub, as I move across the sofa (away from the right wall), the null completely goes away in a fairly flat response.

I can reconnect the rear sub and do all the equalizing, but already know that I'm not going to leave it like that as the peak gives the bass an overall one note-ish tone.


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## Sonnie (Apr 11, 2006)

IIRC, isn't the left side of the couch more centered than the right? Why not just move your primary listening position? Put the girlfriend in the null, she won't know the difference... :nerd:


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## JimP (May 18, 2006)

So that takes care of the null. 

What about the rest of the reverberation/long decay time?


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## Sonnie (Apr 11, 2006)

That's where the professionals come in... (Bryan and the others :yes: ) but I would suggest taking measurements from that area if that's the listening position you want to correct. Let's see what the waterfall looks like there.


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## bpape (Sep 14, 2006)

Decay time is only killed by absorbtion - sorry. That's going to take a willingness on your part ot treat the space with something of enough size and thickness to deal with the low frequencies.

Back to the other topic, I guess I'm baffled why if we can use a 2nd sub to cure the FR issues in the listening positions why we're not doing this. Do you really care that there's a monster peak between 35 and 45 Hz in places that nobody is sitting? There are monster peaks right against all the walls too but nobody is sitting there so who cares?

Not trying to be cavalier - am I missing something here?

Lastly to kind of combine the two topics....

If you can move off to one side and get the null to go away, what is the possibility of having some treatment directly to the side of the listening area (but against the wall)? We may not get rid of it but might be able to tame it a bit and help a tiny bit with decay times at the same time.

Bryan


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## JimP (May 18, 2006)

When you say "something of enough size and thickness", what exactly are we talking about? 

I've tried the second sub along with a MBM-12 in all sorts of configurations. One of the more interesting ones was to have a HGS-15 immediately behind the sofa with either the other HGS-15 and or the MBM-12 up front with a 50hz crossover. I could distinctly hear the sub audio coming from behind me even with a butterworth crossover with a 48db slope. Very flat frequency response, but I just couldn't get past the bass coming from the wrong direction. I know that 50hz is suppose to be non directional, but I sure could hear it coming from behind me. This was only one of the many configurations I have tried.

So at this point, I'm not so concerned about the null. Actually, sliding down the sofa to where the response is flatter doesn't sound that much different. I don't understand why there isn't more of a difference in the way it sounds. Technically, I would expect a major difference. In reality, there isn't.

So, I'm interested in what I can do otherwise.

Thanks for any and all comments!!!


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## bpape (Sep 14, 2006)

Size and thickness...

Bass waves are large, long, and of high intensity and persistence. Something thick enough to get a significant portion of a quarter wavelength in the absorbtion at any one point is required. A 50Hz wave is approx 10' long, a quarter wave of that would be 2.5' long. 4" thick is bare, bare minimum, 6" is better.

For size, my point is that if you're in a 3000 cubic foot space, having 8 sq ft of absorbtion isn't doing much. 99% of the waves will never 'see' the panel. Treating specific places can help in terms of frequency response. Treating more surface area and spread appropriately throughout the space is more effective than the same amount all in one place. We just need to get a treatment plan in place that will address a significant amount of the energy in the room in a reasonable span in the time domain.

You're likely not hearing the null as it's relatively narrow and not specifically on a fundamental note of an instrument or instruments. 

Having the sub directly behind you can be distracting. If it works there, then we can cheat and simply reduce it's level. This will allow the null to come back a bit but not with the same intensity and yet still not be as noticible.

Since you're having a width related issue, have you tried the 2nd sub at the mid point of the rear wall?

Bryan


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