# Acoustic Improvement (Home Theater and Two Channel)



## Sonnie (Apr 11, 2006)

I feel like my acoustical treatments are lacking a bit and want to hopefully improve on what I have now. I also want to see if there is any need to do anything for my two channel setup.

My room is 19'6" wide x 23'2" deep x 8'6" high, with a 6" riser stage across the front and a 12" rear seating riser across the back.

Here is my current setup... all panels are from GIK Acoustics...

3 x 242 panels (24" x 48" x 3.5") on each side of the room that handle side reflections.

 

1 x 242 panel (24" x 48" x 3.5") behind each main front speaker. You cannot see it from the MLP (main listening position) because the front speaker blocks it.

 

1 x Monster Bass Trap panel (24" x 48" x 7.5") on each side of the rear (back) wall behind the surround speakers.

 

So at this point I have some 242 panels on the side and front wall and a couple of the 244 panels in the back.

I am considering adding a couple of GIK Spot Panels 24" x 48" x 2" on the ceiling at the first reflection points... or for about the same price I could get the 242 panels at 24” x 48” x 3.5”... although I am thinking the 2" thick panels might be less obtrusive and obstructive for the rear seat listener.

Those would be placed here... in black, which should also help in light reflection from the screen. 

  

The first reflection points on the ceiling just happen to line up with the sides of the return air vent.

You can see I installed thin plywood covered with velvet, which helps tremendously with light reflection off the ceiling... however, where it ends and the paint starts, there is still light reflection there... although not that noticeable for the MLP. I know the velvet looks bad, but when the lights are off and the only light is the screen reflection, you don't notice them. The only time you can see them is if you use a camera flash.


I am curious about the *Tri-Trap Corner Bass Traps* from floor to ceiling in all four corners of the room. Would this help with the acoustics in the room and would it be worth the expense?

Also... is there any need for diffusor panels anywhere? 

I would not have enough room for the 244's in the back if I installed the Tri-Traps. I could move those to behind the rear seats and place them sideways on the lower wall below the DVD/BD/CD shelving... or put them somewhere else... not sure. I may could use those in the front instead of the 242's behind the main speakers, then move the 242's to somewhere else.

I am also curious about any need for some type of acoustic panels for my two channel setup. I hope to be able to use the Cardas Room Setup Guide suggestions for placing my two channel speakers, which means my speakers will be well into the room... 5.5 feet from each side wall and 8.8 feet from the front wall. (For clarity sake... Cardas calls what I call the front wall the rear wall... it seems more logical to have a front and rear wall ... or front and back, which is in the rear of the room when sitting in the MLP... :huh: )

Here is an overview of the room and approximate two channel speaker placement. If I follow Cardas recommendations, then these may not be positioned just right on this drawing (I am sure I will try different placements anyway), but you get the idea.

 

I would appreciate suggestions and recommendations.


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## Jason_Nolan (Jul 4, 2008)

I know that Martin Logans interact with rooms differently than cone speakers, so those familiar can weigh in more.

I had a lot of room treatment from GIK and my before and after measurement in the bass wasn't really improved. What was improved was imaging, but at the expense of making my room close to too dead for music. I had 6 tritraps and I'm not sure I'm sold. Could've been my difficult room, which was open to many other rooms. I had a lot of treatment though.

I'd be more interested in diffusion and some of the lower tuned bass traps in the future. Everything is in storage now.


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## Sonnie (Apr 11, 2006)

There seems to be a lot of debate about whether to use absorption or diffusion on the wall behind electrostatic speakers. :huh:

I have researched owners of MartinLogans and there have been several who have tested absorption vs. diffusion on the wall behind the speakers. The consensus seems to be that if the speakers can not be placed well out into the room (8 feet or so), then absorption over the entire wall behind the speakers is optimal. Diffusion is preferable for rear surround speakers.

Maybe I should look at diffusion panels for the rear and move those 244's up front... and add Tri-Traps to the front corners.


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## Jason_Nolan (Jul 4, 2008)

Yes, there is that. Also, their sound dispersion patterns are different and the project sound in a manner that doesn't interact with the ceiling. First reflection points on the ceiling may be negated and the money may very well be spent better somewhere else?

This was always my understanding with MLs. Interacting with the room less to improve the sound, but narrowing the listening window.


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## Tonto (Jun 30, 2007)

Did you fill the riser cavities with fluffy pink stuff? That is an easy trick to help with bass tactile responce. The riser has to have openings front & back in each cavity.


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## bpape (Sep 14, 2006)

Tri Traps will help considerably in the corners. At this point, IMO, you're sorely lacking in deeper bass control. Behind the Logans, it's your call. What you could do is move the 242's you have now (or 244's) to the ceiling and then replace them with the same thing, but with our new scatter plate added. That keeps the low and lower mid at 100% absorption, cuts the mid/high absorption by 50%, and adds scattering to the mix to kind of get you the best of all worlds.

Bryan


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## Sonnie (Apr 11, 2006)

I filled some of the cavities with insulation and some with sand... but the bulk of it is sub enclosure for the rear subs.

So Bryan... you are saying more absorption up front, particularly for the lower end? Adding scatter plates to a 242 or 244 is going to help?

I like the idea of using the Tri-Traps up front.


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## bpape (Sep 14, 2006)

Just saying make use of what you have and add Scatter Plates to provide both absorption and scattering for the rear wave of the ML's. They love diffusion behind them but I would agree, if very close to the wall, many times better with absorption. This gives a bit of both. We can also do Scatter Plates on the Tri Traps. The plates reduce mid/high absorption by about 50% but still give all the bass control.

Bryan


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## AudiocRaver (Jun 6, 2012)

FWIW, since I will be joining you for some fun speaker eval time there, I have always preferred absorption at the speaker end of the room, sort of a dead-end/live-end kind of guy, abhor those early reflections even if diffused, even with dipole. I think tighter imaging and soundstage result. But that's just me, gotta honor your ear's preferences, too - your room, after all. Somewhat less of an issue with the speakers well into the room, which I like also.

Bass traps - good. Room too dead - you will have a hard time making a room too dead for me.

Cardas setup guidelines are GREAT. But placement for imaging & SS comes first, they almost always end up being moved a bit for that.

You might want a laser distance meter for precisely repeating placement and angle, assuming you will move the 2-channel speakers aside for cinema viewing.

My 2-cents worth.:bigsmile:


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## Sonnie (Apr 11, 2006)

I'll plan on getting an order up tomorrow. :T


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## phazewolf (Feb 5, 2012)

If you are looking for bass trapping have you thought about using the GIK acoustics scopus tuned membrane bass traps and place them in the corners? They would leave the mids and high's alone but would really tame the lows like nothing else.

Is there a frequency range your trying to target maybe a mix of the ones for 40hz and 70hz would really dig deep into the bass where normal traps have a hard time going. Just a thought.


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## Sonnie (Apr 11, 2006)

I have actually been discussing those with Bryan and Glenn. I do have some issues between 30-45Hz depending on the listening position. I can equalize out the MLP, but then I still have issues on the back row. I think there is a little more to placement than just sticking them in the corners though... and I understand they require quite a bit of experimentation. Also... how many to get is another question. 

What would be nice is to get rid of the peaks before equalization, so maybe getting a couple of them and trying them seems to be worth a shot.


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## phazewolf (Feb 5, 2012)

I was thinking that a corner would be a good starting place to try. They do cost a bit but they dig deep and with a issue in the 35 to 40hz area they would be hard to match.

As for how many maybe start with 4 and play with them and see how they work out for you.

I am working on building some I got a great deal on 2 rolls of 2lb mass loaded vinyl basically 2 rolls 4x10 for $70 shipped so I am going to play with that for now and start off with 10 2x2 panel's and see how they work out.


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## bpape (Sep 14, 2006)

Actually, we experimented with Scopus in the corners but they don't work well there. The back is very dense and rigid and causes some unexpected consequences when straddling corners. We've had much better luck with them flat against walls in specific places. 

Even if we can't tame the FR problems in the back row, we can certainly reduce the bass ringing - then a bit of EQ to finish it off in the rear row - but understand that will also impact the front row.....

Generally 4 of any single tuning are required at a minimum.

Menana!

Bryan


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## phazewolf (Feb 5, 2012)

If it is not too much to ask. What kind of issues does corner placement cause these type of devices? 

I would love to learn more about them.


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## bpape (Sep 14, 2006)

The whole point of these is to not let anything vibrate except the front membrane - kind of like a drum in reversed. When you straddle a corner with them, you can get a lot of cancellations from the thick solid back facing into a corner. Typical velocity type absorbers work great straddling corners.

If you have a problem that needs to be addressed in the corners, you can still use these, just put them against one wall and flat on the other wall so there's little to no gap behind them.

Bryan


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