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Considerations when designing a Logan Theater?

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giomania

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Hi, I am commencing construction of a dedicated home theater featuring Martin Logan Vantage, Stage, and Ascent i speakers. I am wondering if there are any special considerations to take into account during the design phase. I have posted excerpts from a thread I started on AVS Forum below. Since the first poster tried to talk me out of the Logan's, I thought it best to seek assistance here.

If you want to view the thread on AVS, it is located at: http://www.avsforum.com/avs-vb/showthread.php?t=731210


CineMark IV Design & Construction

-------------------------------------------------------------------

Introduction

Welcome to the CineMark IV design & construction thread. Before I get accused of stealing the name for my theater, let me explain. A long time ago in a galaxy far, far, away (Germany), I purchased my first projector—a Sony VPL VW 10HT—and screen. A friend of mine came over and remarked “Wow! It’s like a cinema…it’s CineMark!”.

I have moved several times since then—currently in southwest suburbs of Chicago—and every time I just added a Roman numeral at the end to reflect the new location. I actually constructed a quasi-dedicated theater room for the third location when I finished my basement. I am finishing my basement again, and this implementation of the theater shall be named “CineMark IV”.



Design philosophy

I notice a popular trend is to design and build home theaters which look like the real thing. While I think that is totally cool, it is not the direction which I am heading. My primary goal is audio/video performance…aesthetics is secondary. For example, I have Martin Logan Electrostatic speakers which need to be placed out into the room (away from the room boundaries) for optimal performance. As a result, speaker columns along the walls—a big part of the theater look—would not be an option for my theater, unfortunately.

I know that many will disagree with this philosophy, and that is fine…it takes all kinds to make the world go ‘round. That said; please feel free to chime in with advice—despite your design philosophy—as I welcome all opinions. I cannot think of and/or consider everything, and am always willing to learn.


General thoughts about the room

Room Size
Roughly 28’ Long, 20’ Wide, and ~7’-7” High; I have to plug these dimensions into the room mode calculator spreadsheet and adjust them as necessary. I want the ceiling to be a continuous flat surface for acoustic purposes, so the finished height will need to be just under the ever-present structural steel I-beam and HVAC trunk lines running through the middle of the room’s length.

Lighting
I was initially thinking to just install wall sconce lighting, but I like the idea of multiple-zone lighting with a Grafik Eye controller. The problem is that electrical code where I live requires metal conduit, which is much more difficult and tedious to install than romex.

I am doing the electrical myself, so light placement might be limited by my skill in bending the conduit. Then there is all the extra work building light boxes to limit the flanking noise…if I want to be that ambitious. However, it would appear that code allows flexible metal conduit (aka BX) for a maximum of six feet. So, perhaps I can do this…who knows. I need to do some more checking.


Sound Isolation
I want to try to keep the sound inside, naturally. The room will be bordered on three sides by the poured concrete basement walls. They are insulated on the exterior with 2 inch thick XPS (per the Building Sciences Corp. recommendations), so the insulation in the stud walls will be for sound isolation purposes only. On the wall which will be shared with the remainder of the basement, I was thinking of either a double wall or a staggered stud wall. I plan to install two solid-core exterior doors on this wall, creating an air lock for the theater entry.

I would like to go with a room within a room design with isolated ceiling joists. The only problem is that I have a steel I-beam and HVAC trunk lines to work around; I cannot span the entire width of the room with the isolated ceiling joists. I’m planning on 24” O.C. stud walls, as there is no load to bear. I’m not sure if there is a need for multiple drywall layers with Green Glue, since I’m planning on the room within a room isolation technique. I recall that Russ Hershelmann (spelling?) used to advocate using one layer of ½’ drywall to assist with bass absorbption, but that doesn’t seem to be very popular here.

Acoustic Treatments
I’m definitely interested in home-made bass traps. The electrostatic speakers utilize reflective surfaces, so there may not be a need for any other treated surfaces in the room. I could use some help in this area.

Power Conditioning
EquiTech 10WQ balanced power wall panel
Sort of like a 200 amp sub panel with an isolated transformer and balanced power output. Balanced power has 60 volts on the “hot” and 60 volts on the “neutral” lines, 180 degrees out of phase with each other.



Conclusion

While my equipment list suggests otherwise, I am not wealthy. I am just an average guy who lucked out with a real estate transaction. I applied the windfall to some screaming deals I got while employed at Tweeter.

Mark




10-03-06, 06:50 AM #2 (Print)
bpape
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Join Date: Dec 2000
Location: St. Louis(Wildwood), MO
Posts: 6,687 Congrats on starting your project. Looks like you're going to have a nice setup.

Just a couple of comments.

- I would seriously recommend using something else for speakers in a home theater. Many have tried the Logans and almost all have moved on to something else. They're great for music but just don't get it for HT.

- You will most certainly need additional treatments in the room. I do not say that because we are in that business. I say it because you'll need to deal with decay times in the room.

- Back to #1 - treating the front wall in a multi-channel environment is extremely important to eliminate reflections from the surrounds bouncing back off the front and messing up the soundstage. Also important to assist in dealing with SBIR issues. That said, this is contrary to proper function and output of most planar/open baffle speakers - especially those with rear firing woofers.

For ceiling isolation, you'll probably want to use RSIC-1 clips and hat channel if you can't do your own joists. Also decouple the new inner walls with DC-04 clips.

Bryan

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10-03-06, 08:44 AM #3 (Print)
giomania
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Bryan, thanks for visiting. I know you have helped many others, so I am glad you chimed in. I have heard that about the Logans, but was also thinking that maybe the others didn't spend alot of time on speaker placement or wanted them against the walls. Have you had any personal experience attempting to set up a Logan theater?

I'm not married to the Logan theater idea, because I know I can recoup my investment in the speakers. My previous setup--which I still have-- was a Mirage Omnipolar theater. I had four OM-7's, two OM-5's, and four BPSS-210 subs. I was happy with that setup, but was really looking to up the performance level. I fell in love with the Logan's while at Tweeter, but they were in a 2-channel setup in a very large room.

It would seem the problem is that room design is vastly different for traditional direct radiation speakers versus bipolar or dipolar radiation designs. Do you think the choice has to be made at this juncture or can the room be designed to go either way?

Regarding decoupling the walls with DC-04 clips, I assume you are talking about decoupling the four walls from each other with the clips at the corner intersections?

Thanks for your help.

Mark

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10-03-06, 10:48 AM #4 (Print)
Kevin_Wadsworth
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I think he is referring to decoupling the top of the walls from the joists with the DC-04's.
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10-03-06, 11:41 AM #5 (Print)
giomania
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Hmmm...my understanding of a room within a room design is that the walls will never touch the existing joists above. There enough distance between the bottom of the I-beam and the bottom of the existing joists so that the isolated 2x6 joists will never touch them. That is on the outide perimeter of the room.

Where the I-beam and HVAC trunk lines run, I need to use DC-04 clips to suspend the isolated 2x6 joists from the existing joists, as I cannot build a wall (that sits on the ground) to support them.

I'm not sure if this is making sense or not.

Mark
 

jmschnur

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My Vantage, Cenima i, + NHT rears (celiling) +NHT dipole sides work well. I have used a great deal of Auralex to cut down reflections-especially on the wall opposite my 50" plasma. I also surrounded the plasma with Auralex and used bass traps in the corners.

I hung the Cinema i on the ceiling pointing down just above the place where my screen come up to when I use my projector. The screen is a pull up Dalite.

Critical system balancing is a must!

My Lexcion DC-1 handles the speaker distances from the listeners-this will also be critical for good ambience and effects.

I used teh Digital Essentail DVD to to the balancing of all 7 speakers (I let the Vantages handle the lows).

Your room sounds like it wil be great.

Joel
 
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theWB

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Mark,

Having an all ML Home theater,I couldn't disagree with Bryan from GIK acoustics MORE,even though I use their product in my HT.I actually LOVE my ML HT. I feel the setup and placement of the ML'S in a HT is easier than 2 channel listening.I find myself always tweaking the placement of the mains when 2 channel listening,But have never had the desire to play with the placement when watching movies or listening to surround SACD'S or DVD-AUDIO. I definatly would think about a Sub Woofer,I even use mine when 2 channel listening.Sounds like you have your work cut out for you.

Good Luck -- Definatly go with ML'S You won't regret it. IMHO
 
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giomania

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Thanks for the encouragement, guys. By the way, I am going to have subs; two Velodyne DD-15's and a Bag End Infrasub 18. I posted my equipment list below. It seems like as long as the room has somewhat decent acoustics to start with, then I just need to tweak it with some treatments when it is finished. Is that about right?

I am going to use the room mode calculator spreadsheet to fine-tune the dimensions, but if anyone has any better ideas, I'm all ears.


General thoughts about the room

Room Size
Roughly 28’ Long, 20’ Wide, and ~7’-7” High; I have to plug these dimensions into the room mode calculator spreadsheet and adjust them as necessary. I want the ceiling to be a continuous flat surface for acoustic purposes, so the finished height will need to be just under the ever-present structural steel I-beam and HVAC trunk lines running through the middle of the room’s length.

Fade to Black
The room will painted flat black. I read all the pros and cons on this issue, and decided the pros outweigh the cons. Besides, I had the front wall of CineMark III painted flat black, and that worked out fine. Yes, it marks up easily, but this will not be a play room for kids, after all. I can see the headline now “Man goes ballistic after house guest touches the wall of his home theater”.

Sound Isolation
I want to try to keep the sound inside, naturally. The room will be bordered on three sides by the poured concrete basement walls. They are insulated on the exterior with 2 inch thick XPS (per the Building Sciences Corp. recommendations), so the insulation in the stud walls will be for sound isolation purposes only. On the wall which will be shared with the remainder of the basement, I was thinking of either a double wall or a staggered stud wall. I plan to install two solid-core exterior doors on this wall, creating an air lock for the theater entry.

I would like to go with a room within a room design with isolated ceiling joists. The only problem is that I have a steel I-beam and HVAC trunk lines to work around; I cannot span the entire width of the room with the isolated ceiling joists. I’m planning on 24” O.C. stud walls, as there is no load to bear. I’m not sure if there is a need for multiple drywall layers with Green Glue, since I’m planning on the room within a room isolation technique. I recall that Russ Hershelmann (spelling?) used to advocate using one layer of ½’ drywall to assist with bass absorbption, but that doesn’t seem to be very popular here.

Acoustic Treatments
I’m definitely interested in home-made bass traps. The electrostatic speakers utilize reflective surfaces, so there may not be a need for any other treated surfaces in the room. I could use some help in this area.



The obligatory equipment List

HD Video Source Devices
HD-DVD, Blu-Ray, or combo player, TBD
JVC HMDH30000U D-VHS VCR
Samsung SIR-T165 ATSC Tuner
Sony DHG HDD-500 HD-DVR

SD Video Source Devices
Pioneer Elite DV-59 Avi DVD Player
Pioneer Elite DV-79 Avi DVD Player

Miscellaneous Source Devices
Satellite TV STB, TBD
Satellite Radio Tuner, TBD
Sony CDP CA7ES 5-disc CD Player
Yamaha TX-492 AM/FM Tuner

Video Reproduction Chain
Vidikron VDP-80 Video Processor
OEM: Lumagen Vision Pro HDP
Vidikron Vision 80 Projector (1920 x 1080 3-chip LCOS)
OEM: JVC HD-2K
Stewart Filmscreen 110” (1.78:1) Luxus Deluxe ScreenWall with StudioTek 130

Audio Reproduction Chain
Lexicon MC-12B processor
Classe’ CAV-180, 5-channel amplifier
Proceed BPA-2, 2-channel amplifier
Velodyne DD-15 subwoofers, 2 each (Left & Right subs)
Bag End Infrasub-18 (LFE Sub)
Martin Logan “Vantage” Electrostatic loudspeaker (Front Left/Right, Side Left/Right)
Martin Logan “Stage” Electrostatic loudspeaker (Center channel)
Martin Logan “Ascent I” Electrostatic loudspeaker (Rear Left/Right)

Power Conditioning
EquiTech 10WQ balanced power wall panel
Sort of like a 200 amp sub panel with an isolated transformer and balanced power output. Balanced power has 60 volts on the “hot” and 60 volts on the “neutral” lines, 180 degrees out of phase with each other.

Equipment Rack
I will build an in-wall rack with rear access using the popular low-cost solution of mounting the rack rails to a framed opening. Rear access will be via an equipment room, where the wall-mounted EquiTech power panel will be located as well.

I plan to vent the equipment room using one of the Panasonic quiet bathroom fans feeding into the HVAC return. I am still undecided on whether to actuate the fan with a temperature switch or with a 12 volt trigger tied to a 120V relay. I like the idea of using a 2-speed fan; the lower speed setting is designed to be on all the time, and the high speed setting is activated when more airflow is needed.
 

jmschnur

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Two points

1. The ceiling is a bit low. A smooth run for the ceiling may not be the best choice. you might want to intoruce some texture in it.

2. AC/Heating considerations are very important with all the power being used. This means you should have at least one and perhaps two returns in your room along with several supplies It is imortant to ensure that the air supply registers are large enough so that air flow is not an issue for noise prodction.

Joel
 

giomania

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jmschnur said:
Two points

1. The ceiling is a bit low. A smooth run for the ceiling may not be the best choice. you might want to intoruce some texture in it.

2. AC/Heating considerations are very important with all the power being used. This means you should have at least one and perhaps two returns in your room along with several supplies It is imortant to ensure that the air supply registers are large enough so that air flow is not an issue for noise prodction.

Joel
Thanks for the reply, Joel. What about a "knockdown" finish on the low ceiling? I had this finish in my last theater. They applied a thin coat of drywall mud to the ceiling, used a round-head brush to "mess it up" and create little stalagtites, then used a trowel to knock off the stalagtites and smooth it out a bit. Is that the kind of texture you were speaking of?

I am going to get HVAC contractors to provide quotations once the wall are up. If they cannot make basic calculations like amount of BTU's per person or per wattage of equipment, they will not get the job. I can make those calculations, but cannot translate them into a well-designed HVAC system.

I am going to install a bathroom fan over the in-wall rack, which should remove most of the heat from that equipment. The amps are going to be at the top of the rack, since they run hot. This configuration should help alot, as the subs (and I think the speakers as well) all use class D amps, which do not run that hot.

Thoughts?

Mark
 

jmschnur

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Yes-that celing will help.

Just be sure there is at least one return in your HT room for the AC registerYou should be fine
 

cstory

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I just wanted to add an additional voice saying that a MArtin Logan Home Theater can be extremely sastisfying. I also wanted to toss out a couple of suggestions on the design.

1.For the ceiling you may want to consider a short drop ceiling with acoustical tiles in it. We had that done in our basement and despite our initial reservations, it turned out looking quite nice, it definitely helped to reduce the echo in the room, and it provides quite good sound isolation between the basement and the kitchen/living room above.

2. In case you haven't thought about it, you may want to position electrical outlets near the speaker locations for plugging them in.

You have some great equipment, it should be a real treat when you get it all complete. We love our system.

Chuck
System #111

The photo shows our ceiling so you can get an idea of what it looks like. It also makes running cables easy.
BTW, Mirage BP-150 subwoofer since replaced by SVS PC-Ultra.
 

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JonFo

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Hi Mark,

Great project, and I totally agree with your stated goals of Music reproduction taking priority over thematic looks.

A well executed ML based theater can both sound great and look good.
Although I’m still making slow progress on the later, I could not be happier with the former.

Concerns over the low ceiling are usually due to room volume and ‘ceiling bounce’ from mid-bass drivers. Also, the dynamic tweeter in the Stage will create a ceiling bounce of its own that should be damped, especially off a low ceiling, which shortens the delay of the reflection.

Therefore, first reflection boundaries on the ceiling should be treated to damp high frequency ranges (essentially, the tweeters range).

The other thing regarding the ceiling you could think about is using the extra depth where the I-Beam and HVAC runs are absent as space for a stealth bass trap. Look into some trap designs that could be built-in. One advantage is that if the positioning works out, you can implement pretty large traps without any in-room space sacrifice.
Aesthetically, part of the ceiling will have cloth over it, which if also black, will pretty much be invisible. You could even use some fiber optic starscape tiles on the ceiling were the I-Beam goes.

No big concerns for ESL radiation in the vertical dimension, as they have nice nulls above and below the panels. Although one reason I prefer older gen panels with straight baffles over newer, is that the newer gen, sloped baffle will put mid and high frequency energy into the room at incident angles that will start coming off the ceiling (from the rear of the room most likely) so it’s important to damp the rear and rear side walls to keep that bounce under control. But then, that applies to front waves as well.

While ESL’s do depend on some rear-wave reflection for their ‘sound’, it still needs to be managed, otherwise smearing results; and that’s not so nice.

For best results, very little of the rear wave from the L/R speakers should bounce off the front wall back between the speakers. The usual toe-out will help with this, but additional damping is required. So plan to put damping not only behind the L/R, but also spread it towards the center. In my setup, it extends almost 2 ft towards center for L and R.

In my theater, I damp using some RPG products right behind the mains and the front side wall (behind the speaker). I also damp the length of the side walls from roughly 2 ft from speakers all the way to parallel the seating positions. This works well to damp side-to-side slap-echo and broadens the room acoustically.

On the rear wall, good diffusion is recommended; otherwise the L/C/R will bounce back hard and really smear the intelligibility of dialog and the clarity of music.
I used two sets of RPG skyline (see pics on my System #45 thread), flanked by some additional absorption.

I went back and forth over whether to use a 3D diffusion or use a 2D specular diffuser, and settled on liking the sound of the 3D better.

Also on the rears, I recommend 2D specular diffusion for spreading out the rear wave of the rear speakers. Putting a 4ft tall set of 2D diffusers (or even abfusors) is recommended. This makes the rear surrounds truly enveloping.

Anyway, food for thought.

Oh, one final suggestion, get a copy of the GedLee book on HT design and construction. Very much worth the price when spending this kind of coin.
 

JonFo

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giomania said:
Power Conditioning
EquiTech 10WQ balanced power wall panel
Sort of like a 200 amp sub panel with an isolated transformer and balanced power output. Balanced power has 60 volts on the “hot” and 60 volts on the “neutral” lines, 180 degrees out of phase with each other.
Great choice. Balanced power not only improves the noise floor, but I find that equipment has fewer issues with a steady supply of clean power.
That big transformer soaks up power line fluctuations. I’ll see lights dim on other circuits and the system is totally unaffected.

Are you planning on feeding the ML speakers balanced as well?

I ran a totally separate circuit in my theater for eight outlets (front, center, right, sides, rears and ceiling), it terminates in a box in the equipment room that I then jumper to my Equitech via some relays, so I can turn off the Monoliths when amps are off.

ML’s work just great with balanced power.

A 10WQ is definitely plenty for what you're planning, and leaves a lot of headroom.
 

giomania

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cstory said:
I just wanted to add an additional voice saying that a MArtin Logan Home Theater can be extremely sastisfying. I also wanted to toss out a couple of suggestions on the design.

1.For the ceiling you may want to consider a short drop ceiling with acoustical tiles in it. We had that done in our basement and despite our initial reservations, it turned out looking quite nice, it definitely helped to reduce the echo in the room, and it provides quite good sound isolation between the basement and the kitchen/living room above.
Thanks for the reply, Chuck. How do you keep the dropped ceiling from buzzing and rattling? Did you put bags of sand on top of each tile or are the secured to the track somehow?

2. In case you haven't thought about it, you may want to position electrical outlets near the speaker locations for plugging them in.
Yes, I will have outlets near the speaker locations, but thanks for the sanity check. :D
 

giomania

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JonFo said:
Great choice. Balanced power not only improves the noise floor, but I find that equipment has fewer issues with a steady supply of clean power.
That big transformer soaks up power line fluctuations. I’ll see lights dim on other circuits and the system is totally unaffected.

Are you planning on feeding the ML speakers balanced as well?

I ran a totally separate circuit in my theater for eight outlets (front, center, right, sides, rears and ceiling), it terminates in a box in the equipment room that I then jumper to my Equitech via some relays, so I can turn off the Monoliths when amps are off.

ML’s work just great with balanced power.

A 10WQ is definitely plenty for what you're planning, and leaves a lot of headroom.
Jon, thanks for the reply. I was hanging that 400 pound EquiTech panel this weekend. I did it by myself using a come-along and pieces of wood and concrete blocks to support it as I raised it. Anyway, it is done...whew! That is the reason whey I did not have much time to reply to the posts here.

Yes, I am running the ML's off the balanced power panel. Every piece of electronics in the theater will be on the balanced power. In addition, I am running my family room system and home computer.

I had a long discussion with EquiTech about my wattage requirements before I ordered. Basically, my total demand (if everything was on at once and drawing full current) exceeds 10K. They assured me the 10WQ was sufficient, as not everything will be on at once or drawing full current.

I'm curious to hear about your listening / viewing impressions (improvements, etc.) when you added EquiTech balanced power to your system. Now, I am going to carefully read your detailed post about acoustic treatments.

Mark
 

giomania

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JonFo said:
Hi Mark,

Concerns over the low ceiling are usually due to room volume and ‘ceiling bounce’ from mid-bass drivers.
But the ML's do not have conventional mid-bass drivers, so that is not an issue?

I used two sets of RPG skyline, flanked by some additional absorption.
I saw that in your web site...looks cool!

So, it would seem like I just build out the room with drywall (using optimal dimensions) and add the acoustic treatments over the drywall. The exception would be if I decided to use the ceiling as a giant bass absorber, like you suggested.

Do you plan to cover the treatments with acoustically transparent fabric, or does RPG recommend against that? I'm thinking in an all black room with black fabric-covered treatments, it would all blend in.

Thanks so much for your time and advice.

Mark
 

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Room Dimensions

I have more accurate room dimensions after having used the room mode calculator spreadsheet to obtain the best modal distribution. I have attached the Excel file if you care to take a look.

I started with the following (finished) dimensions:
L: 27'-4" Limited by the maximum length of the isolated ceiling joists.
W: 20'-0" Limited by the concrete walls on both sides.
H: 7'-7.5" Limited by the Steel I-Beam running the length of the room.

After playing around with the spreadsheet, I ended up with the following (finished) dimensions:
L: 27'-3"
W: 19'-8"
H: 7'-7.5"

According to the spreadsheet, I only have four problem frequencies below 200Hz:
86.1Hz (3rd resonance in the width dimension)
145Hz (7th resonance in the length dimension)
148.1Hz (2nd resonance in the height dimension)
172.2Hz (6th resonance in the width dimension)

I manipulated the numbers one inch at a time and then compared the results. I felt the above dimensions provided the best performance for room modes.

Mark
 

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