SWithey DIY Dual 15” Subs – Down to 15Hz

**ThomasW** · 31 May 2006, 01:27 Wednesday

Excluding the plinth you might find something like that HERE

Plan on dealing with a weight ~300lbs

**Dotay** · 31 May 2006, 09:35 Wednesday

Have you ruled out an Infinite Baffle installation in your room? It's pretty much the consensus for low clean bass and with your false wall your room seems to be a good candidate. Four of the new Dayton RS 15"s would probably fill that room nicely. :T

**swithey** · 31 May 2006, 09:45 Wednesday

Originally posted by ThomasW

Excluding the plinth you might find something like that HERE

Plan on dealing with a weight ~300lbs

ThomasW,

Yes, I had seen that build before. It was a real inspiration. However, 300lbs may be a bit difficult to carry up the stairs. Anyway I could get that box to a manageable size (maybe 150lbs) and still achieve some nice low sound?

If I did do a tube, I would want to veneer it with Maple to tie in with the rest of my room. As far as I know, the tub material will adhere to the veneer.

**dyazdani** · 31 May 2006, 09:53 Wednesday

Originally posted by swithey

However, 300lbs may be a bit difficult to carry up the stairs. Anyway I could get that box to a manageable size (maybe 150lbs) and still achieve some nice low sound?

An enclosure around 4 cu. ft. would work well given your dimensions - a 22" cube would be just right, double walled. Most people who build sealed RL-p15 subs are in this range, so it seems (including myself).

Weight would be dead on 150lbs (each).

**swithey** · 31 May 2006, 10:48 Wednesday

Originally posted by Dotay

Have you ruled out an Infinite Baffle installation in your room? It's pretty much the consensus for low clean bass and with your false wall your room seems to be a good candidate. Four of the new Dayton RS 15"s would probably fill that room nicely. :T

Actaully, I did consider a few IB setup (using 4 15" as you suggested). Check out this LINK.

The first idea uses the attic space behind the false wall. The issue was the sound would then resonate around the rest of the house attic space which would make night viewing a bit challenging with "sleeping" small kids. The second location was actually to build the IB inside the false wall area (as you suggested). While this is possible, I have to work around the corner bass traps, my floorstander speakers next to the traps and a center channel either behind a AT screen or below the screen. There is not enough room above the screen because of a 45deg sloaped. This design would require me to seal off the center false wall area and would block the sides of the bass traps (reducing their effectiveness).

Here is my room layout to give you a better sense of what I'm talking about.

Top View

Image not available

Side View

Image not available

If I've missed something, please let me know.

**swithey** · 31 May 2006, 11:01 Wednesday

Originally posted by dyazdani

An enclosure around 4 cu. ft. would work well given your dimensions - a 22" cube would be just right, double walled. Most people who build sealed RL-p15 subs are in this range, so it seems (including myself).

Weight would be dead on 150lbs (each).

Sealed would be a lot easier to build and from what I've read can do quite well. However, I was thinking the only way to get down that low would require a port to boost things "naturally" as the woofer started giving out. Keep in mind, only one of my subs (rear) can be corner loaded (which from what I've read can give this type of design a nice boost). The other (front) will be up against one wall but open on the other 3 sides.

**ThomasW** · 31 May 2006, 11:06 Wednesday

My advise is build the IB.

A tremendous amount of the rearwave is absorbed by the insulation in the attic space. Other than that they output no more SPL than a standard sub driven to the same output levels.

And other than Bruce Thipen's rotary sub, no other sub has as much output down low as an IB

**swithey** · 31 May 2006, 11:31 Wednesday

Originally posted by ThomasW

My advise is build the IB.

A tremendous amount of the rearwave is absorbed by the insulation in the attic space. Other than that they output no more SPL than a standard sub driven to the same output levels.

And other than Bruce Thipen's rotary sub, no other sub has as much output down low as an IB

Thomas,

If the drivers are directly behind the screen, won't the air-pressure ripple my screen? The drivers will only be about 2' from the screen.

**ThomasW** · 31 May 2006, 12:10 Wednesday

Mount the drivers below the screen.

**swithey** · 31 May 2006, 23:52 Wednesday

Thomas,

Thanks for your suggestions. Okay, you may have me convinced to go IB. Which option(s) would work in my room? And feel free to suggest something else.

Option #1:
Woofers up against the front of the false wall. (2) special sealed boxes would separate the upper part of the false wall area from the IB area below. The back of each box would be open to the attic space. The middle area between each pair of woofers would be for the center channel speaker.

Image not available

Option #2:
Woofers are in the rear wall. No box -- woofers just shoot into the false wall area

Image not available

Option #3:
Same as Opt #1 but entire bottom area below screen would be separated from the screen area above. Center channel would be behind am AT screen.

Image not available

Option #4:
Same as Opt #2 but center channel moved behind AT screen.

Image not available

QUESTION: How much power would I need to drive these (4) woofs? Would an Behr EP1500 be enough or do I need to move to the EP2500?

Side Comment -- the attic area behind the false wall is floored with particle board. The roofline of the house starts at 6'5" at the false wall then drops to ZERO about 8' back. There is no insulation in this space except what is in the false wall. There is no insulation below the floor boards (in the attic space) since it is above the garage. I could, however, add some R19 in the rafters if needed and/or below the particleboard floor if needed.

**ThomasW** · 01 June 2006, 00:49 Thursday

Option #1 or #3

Here's one installed like it

Below you can see the shaft connecting the front of the baffle to the room behind it

I'd use the EP2500. Probably won't need the extra power but given the minimal cost difference it's nice to have the amp just off idle when playing loud passages.

Yes insulate the attic area, if possible cover all available surfaces with as thick a product as you can install.

**swithey** · 01 June 2006, 10:10 Thursday

Originally posted by Dotay

Have you ruled out an Infinite Baffle installation in your room? It's pretty much the consensus for low clean bass and with your false wall your room seems to be a good candidate. Four of the new Dayton RS 15"s would probably fill that room nicely. :T

Okay, IB it is. I believe I can make that work in my room :T

Now, onto the drivers. I've heard nothing by rave reviews for the SoundSplinter RL-p 15. However you (Dotay) mentioned these new Dayton RS 15"s. The Daytons are about $94 cheaper per speaker but I do not want to make a huge sacrifice to save $375. I want clean sound. But, if the Daytons will do the job as well as the SS, I can get them.

Here are the costs:

SoundSplinter RL-p 15: Qty 4 = $980 + shipping
Dayton RS15: Qty 4 = $607.50 + shipping

If SS RL-p 15 is the choice, do I get the 2ohm or 4ohm version? I plan to run them in pairs. Do I wire these in parallel or series?

If Dayton is the choice, which model do you prefer for IB setup? The RSS390HF-4 goes lower but the RSS390HO-4 looks to be a bit more heavy duty. Also, since these only come in a 4ohm version, should they be run (in pairs) in parallel or series?

**ThomasW** · 01 June 2006, 11:05 Thursday

With IB's a primary consideration is the swept volume (Vd) aka amount of air moved. The RL-p15s Will move almost twice as much air as an equal number of RS15's. So think V8 vs V6 motor.

If you have the extra height there are several 18" IB specific drivers under development. So unless you need your drivers in a hurry, it might be prudent to wait and see what comes to market in the next couple of months.

If the choice must be made immediately, my vote is for the RL-p15"s. If you buy the 4 ohm units they can be series/paralleled wired into pairs = 4 ohm load per channel.

**Dotay** · 01 June 2006, 11:16 Thursday

I'll defer to Thomas when it comes to subwoofer choice. My initial suggestion of the RS15s was based on the fact that you could do four of them for the cost of two SS drivers plus building materials (veneer, ports etc) for the box subs.

But if the budget permits cram as many of those buggers in there that you can. :B Does anyone know the status of the IB Lambda 15"s drivers that AE offers? They're supposed to be the best displacement/$ available...when they're available IIRC.

**swithey** · 01 June 2006, 13:43 Thursday

Originally posted by ThomasW

With IB's a primary consideration is the swept volume (Vd) aka amount of air moved. The RL-p15s Will move almost twice as much air as an equal number of RS15's. So think V8 vs V6 motor.

If you have the extra height there are several 18" IB specific drivers under development. So unless you need your drivers in a hurry, it might be prudent to wait and see what comes to market in the next couple of months.

If the choice must be made immediately, my vote is for the RL-p15"s. If you buy the 4 ohm units they can be series/paralleled wired into pairs = 4 ohm load per channel.

I've got some time. Does that mean I could get away with (2) 18's vs. (4) 15's -- OR should I just go with Dotay and fill 'er full to the top? :B

The question is how much more expensive will the 18s be over the 15s? (4) SS 15's is pushing my budget as it is. I just need to re-work the studs below my screen to be spaced right to accomidate the drivers. They are currently 16" on center so adjustment will need to be made. I just don't want to do it twice.

**ThomasW** · 01 June 2006, 13:56 Thursday

18" drivers will fit between 16" OC stud spacing because the frame tapers so quickly after the baffle.

The pricing on the 18"s isn't set since all are being beta tested.

If it's a 'do it once' project then get 4-RL-p15"s or 4-18"s depending on what's available when you're ready to buy.

**swithey** · 02 June 2006, 09:05 Friday

Originally posted by ThomasW

Option #1 or #3

Thomas,

Just curious, what is wrong with Option #2 (or #4 if I go with an AT screen)? The entire front wall will be covered with AT fabric (GOM). So, this will allow the waves to escape. With this said, would either/both of these options be viable?

Option #2:
Woofers are in the rear wall. No box -- woofers just shoot into the false wall area

Image not available

**ThomasW** · 02 June 2006, 10:39 Friday

Firing into the area created by the false wall will have a negative impact on the sound quality.

In addition it's best to have the all the speakers in the system somewhat aligned.

**bpape** · 02 June 2006, 21:02 Friday

While I totally understand time alignment, the issues caused by the huge box and the forcing of the center speaker to be behind the screen (and the obligatory perf screen) IMO are more of a compromise than a small time alignment issue.

The false wall made of studs and cloth should not cause any performance issues. Whether you're behind a grille only or a pair of studs with the closth over the top, the differenc in performance should be negligible.

I'd love to hear what you think the potential performance issues would be sitting behind basically nothing but GOM cloth for a subwoofer of this caliber - or maybe it's just a misunderstanding of exactly what the false wall is and how it's constructed.

Bryan

**ThomasW** · 02 June 2006, 22:40 Friday

My tolerance for rude people in this forum is officially zero. So those people don't get answers, they get banned.

Come back in a week with a different attitude and you'll be able to post again.

**swithey** · 02 June 2006, 23:20 Friday

Originally posted by ThomasW

My tolerance for rude people in this forum is officially zero. So those people don't get answers, they get banned.

Come back in a week with a different attitude and you'll be able to post again.

Thomas,

I think Bryan's question/comments may have came across differently than he had intended. He is a very well respected and knowledgeable poster over on AVS.

I think his concern (as well as mine) was with the 100% GOM front false wall and how that would have much impact putting the woofers on wall shared with the attic (vs. up front on the false wall). I understand that the 24" distance between the woofers and the fronts of my L/R speaker may cause some "small" audio delay but I "think" I can fix that with my Pre/Pro.

My major reason to see if I could put the speakers flush with the attic wall is so the center channel will not be "boxed" in the middle between each of the IB boxes (hurting the performace of the center channel). If this is the preferred setup, I would require me to go with an AT screen and push my center up behind the screen. However, I'd prefer not to use an AT screen if it not required.

Thanks again for your help

**ThomasW** · 03 June 2006, 13:39 Saturday

Steve,

I wanted to post just so you know your thread isn't being ignored. Later today or possibly early Sunday, one of our more notable forum members will post a thorough analysis of the situation.

Hint, bring a pencil.....

**Evil Twin** · 03 June 2006, 17:14 Saturday

Originally posted by swithey

Thomas,

Just curious, what is wrong with Option #2 (or #4 if I go with an AT screen)? The entire front wall will be covered with AT fabric (GOM). So, this will allow the waves to escape. With this said, would either/both of these options be viable?

Option #2:
Woofers are in the rear wall. No box -- woofers just shoot into the false wall area

I don't know how far along you are with this project, but I'd like to raise a few questions as well as some comments. I understand there's a pretty long thread at AVS on this project, but due to the demands of the Emperor, reading it from start to finish is not an option.

The screen size vs room size is at the crux of some of your issues. I am not a fan of perf screens in general, though I'll acknowledge that at times they may be a necessary evil. Let's consider the screen and room issues first, then the speaker ones.

You have a very large screen planned for a small room/wall combination.

I trust you're planning on solid light control, including your choice of paint colors for the third of the room near the screen. I'd recommend a black or very dark neutral gray (check out Behr paints) for the ceiling (in total), and for the first third of the walls, a similar treatment- a dark matte neutral gray may be more aesthetically acceptable. What won't work with this large a screen in this small a room is light colored walls, like white, beige or tan. The light throwback to the screen of walls and ceilings so close will kill your ANSI contrast ratio.

The large screen is aggravating your potential problems with speakers. Let's consider your basic layouts.

All of your options have problems. There are two basic problems to be concerned about. One is LF boundary loading and frequency response interaction, the other is combfiltering from strong early reflections with a time path difference. They'll be discussed in turn.

LF frequency response (from ~250 Hz on down) is influenced by the proximity to nearby hard boundaries, when the speaker isn't set flush into a wall boundary such as is often down in recording studios. This can be analyzed in depth by methods based on finite element analysis (such as SoundEasy or Cara Labs use), or by fixed single point calculations (as I have done in the past with MathCAD or by matrixed calculations such as RPG Acoustics employs in Room Optimizer. Experience works well, also, as well as simple reciprocity tricks like putting a speaker in a spot where you intend to listen, then moving yourself to where you want to place the speaker and seeing what it sounds like.

In general, the main trick is to space the dimensions to the three nearest boundaries on golden mean ratios, and avoid boundaries so close that their can be strong early reflections high up in frequency. First, I'll illustrate simple calculations of reasonable boundary distance choices and unreasonable ones. BTW, this is not just an LF issue below 100 Hz. The worst thing to do is space LF drivers from boundaries at similar distances. Many supposed problems with integration of subs and mains are due to this.

Poor Choice #1

Mediocre Choice, #2

Fairly reasonable choice, #3

the LF driver response is a function of the box tuning and driver; this is what one would measure as nearfiled or anehoic response. It's combined with the the theoretical boundary response from hard, low loss boundaries at the specified distances.

One other point to remember is that the LF system should have predictable response close to an octave either side of the crossover frequency, othwer wise the "ideal" transfer function of the electronic crossover is compromised.

Problems may exist with your mains speaker positions, and almost certainly do for most of your proposed center channel locations below the screen and only 14-18" above the floor. I would probably forgo an active center channel speaker and use a phantom center rather than placing it so close to the floor.

The other problem with speaker positioning when you have them close to a side wall, ceiling, or floor, is that you get strong early reflections with a time path delay which causes combfiltering in the frequency response, sometimes severe.

Room Effects

The link above discusses the basics of these and other room issues.

If you can't place the speakers well away from walls near them, then the only other option is a combination of diffusion and absorption. RPG Diffuser systems is one place to read up on that.

For absorption and diffusion, any wall or surface for which if you place a mirror on, and you can see the speakers from your seating position is a potential problem area. Long narrow rooms exacerbate the issues, because the difference in reflection paths is small, and the reflected sound from a wall close to the speaker hasn't dropped much in intensity.

But, the room you have is the room you have.

While I dont' like Perf screens, depending on the projector type, it may be the lesser of evils, if you get a good quality one (think Stewart). In that case, I'd use identical speakers, and locate all three behind the screen (L, R Mains, Center), and do an EQ check with a swept chirp as well as more conventional RTA to assess the need for any equalization to compensate for the screen and speaker interaction.

Were it my room, I would probably reduce the size of the screen, use a non-perf screen, and move the screen height up next to a matte black ceiling (velvet is good for controlling light scatter close to a screen), in order to get some working height for the center channel. I probably wouldn't use over a 96" size screen in this size room.

Actually, I'd probably assess the L+R mains in phantom center against a physical center. I would locate the mains at golden ratios from the floor, back wall, and side wall, and use separate EQ to flatten out the midbass hump that will still result from such close proximity to boundaries, before implementing the processor crossover. May also have to take care of any issues from the cloth wall in high frequency performance. I would locate the subwoofers in the rearward position away the mains, compensating the time offset in the HT processor.

If using a physical center below the screen, I'd do my best to locate it as high as possible (after moving the screen up), and measure it in place and EQ it separately as for the mains.

The screen would be a permanent wall mount type, which should give adequate tension to avoid "flapping" from the subs. If not, back it with a sheet of HDF or BB ply. On general principle I'd probably loosely stuff the whole area behind your GOM cloth wall (except in front of the IB subs) with sheet fiberglass product; too bad Miraflex isn't made anymore.

Remember, you're building a new system at a time when new standards for sound and video are being introduced, and what gets you most of the way there to decent sound with DD or DTS may be found wanting compared with DD+ or TrueHD. The latter can be better than standard non-lossy PCM audio, and is subjectively (in my opinion) a clear step up from our existing HT Audio, even on modest speakers such as designed and built on this forum with Parts Express Drivers.

Good luck with your project and system, and I hope it brings you and your family many satisfying hours of entertainment and escape from the day to day world.

**ThomasW** · 03 June 2006, 18:07 Saturday

Now if all that was a bit much, here's the "Cliff's Note's" version specifically dealing with the IB, and it's impact on the center channel.

What follows relates to the horizontally mounted center below the screen......Compounded distance issues (proximity of the center to the floor, and it's proximity to the rear wall) will cause problems with the low frequency output from center regardless of whether or not the IB drivers are in boxes at the frontal boundary of the false wall, or mounted on the rear wall.

You can put the IB drivers where ever you want, and it will still sound better than any standard 'box' sub. But understand that having the IB drivers in boxes at the false wall will not significantly exacerbate the already compromised output from a horizontally mounted center speaker given the issues already discussed.

Although there's no such thing as a sonically transparent screen, personally I think a perf screen is the 'better' option in this situation. Having the tweeters all at the same level, and getting the center up off the floor is the better compromise than dealing with the issues created by the floor bounce.

**Dennis H** · 03 June 2006, 20:44 Saturday

Well, here I go again, tooting my unpopular 3rd party line of dual centers above and below the screen, fully recognizing that I may suffer a remote choke hold from ET.

Jon proposes an L+R phantom center but let's think about that. The left and right tweeters will be about 130" apart and the seats may be as much as 80" apart on that horizontal axis. With dual centers, the tweeters will be about 62" apart and the seated listeners' ears will all be within 6" or so on the vertical axis. Which will have the worse comb filtering? Inquiring minds and all that.....

Edit: However, Evil Twin and I agree strongly that having a center on the floor or the ceiling sucks bigtime. Who wants to hear voices from a singer 1' tall or 9' tall? The (real or phantom) center needs to be at the same height as the L&R both for voices and smooth pans.

**jtt** · 04 June 2006, 03:58 Sunday

I know this isn't the advice you were looking for, but I would tend to agree with Jon's advice on screen size. I have a room thats slightly wider and longer then your room with 8' ceilings and put in a mid quality (high end da-lite) fixed frame 106" screen. I'm very happy with the fixed frame screen, but I have white ceilings and a lighter carpet and that kills my screen even though the walls are dark.

When I was shopping around a few years ago, putting my theater together, I saw similar advice that 2-3X screen height should = viewing distance. 106" was pushing 2X, but I wanted big. The larger screen has turned out to be too much for me in that size room at a 9' viewing distance when theres lots of action and it doesn't work well with video games. If I had it to do over again I'd get the 92" and never look back for that room. That's still a good sized screen and overall I think most people would be more satisfied with that size (although everyone has different tolerances).

If reducing screen size can help achieve a balance with the audio it might be worth more consideration.

jt

**bpape** · 04 June 2006, 08:42 Sunday

I've modded my other post to come across better. It was not my intention to be rude in any way. I've spoken to Thomas about this offline. Just want to apologize in public.

Now, back to the topic...

Steve and I have discussed for a long time the issues caused by this large screen. I understand the suggestions about the center channel and the boundary issues. My personal opinion in general would agree with his initial statement that he doesn't like perf (AT) screens.

My concerns with the perf are as follows.

- serious comb filtering caused by the speaker(s) behing behind the screen. Even the really nice Screen Research screens cause some combing. This can be dealt with somewhat by treating the front wall behind the screen but you'll never totally eliminate it. It also requires adding EQ into the reproduction chain on the LCR to better timbre match them with the surrounds. I personally strongly resist using EQ on anything but the sub unless absolutely necessary. YMMV

- loss of brightness and clarity on the video picture. Even with the nice Stewarts, Screen Research, etc., a perf screen IMO is just not of the same picture quality. I've seen to many side-by-sides with the 2 different matierals and never seen a perf I could live with that I couldn't get a non-perf that looked as good or better for half the money.

- potential moire issues iwth a perf screen and a digital PJ. Sometimes it's minor, sometimes it's very noticable and to me, very distracting.

Now, couple those with the budgetary restrictions that are going to preclude him from buying a Stewart or SR AT screen and I would have to recommend against the perf screen (though I would agree that a smaller screen is more appropriate and have told him so in the past).

Anyway - now for a solution. If we go ahead and build the 'boxes' for the IB subs to bring them out more flush with the main speaker faces. Then we build another box to mount the center channel in (very solid, very tight front, etc. - basically baffle mounting) we can minimize the 'doubling' of effect based on distance to floor and distance to wall being similar. Obviously this would have to be a precision mount and have the front face treated since most of the center channels he's considering are not designed to be baffle mounted.

We can also treat the floor heavily with material that has good absorbtion down to below 80Hz (where the center will be crossed over anyway). Treating the boundary in this way can definitely assist in drastically minimizing the SBIR effect.

Bryan

**ThomasW** · 04 June 2006, 09:49 Sunday

It's the traditional 'Catch-22' of human wants vs the laws of physics.....

Another option would be to modify the crossover in the center channel. Removing any baffle-step compensation in the crossover would be beneficial in optimizing it's performance in the horizontal under screen location.

Since the center is a factory assembled unit access to the XO schematics might be limited. So I'm not sure how practical this option is. But it can't hurt to ask the speaker mfgr if they'll provide the information.

**bpape** · 04 June 2006, 11:11 Sunday

Well, it may be a little bit easier as Steve has also been considering the DIY option for his speakers as well as the subs. In that case, the xover could absolutely be designed specifically for the application.

Decisions decisions. Every one has an effect on each of the others.

**chasw98** · 04 June 2006, 12:27 Sunday

That was a helluva an answer from Evil Twin!

**ThomasW** · 04 June 2006, 14:08 Sunday

That was a helluva an answer from Evil Twin!

As was expected after the 'conference call' yesterday morning.....:B

ET and I started designing custom HT's in 1984 with my stepfather's front projection system. We did the design for my current theater in 1988. So we don't have quite as much experience with HT's as we do speaker design, (started that in 1969), but we're not exactly neophites to the process either ... :wink:

**Evil Twin** · 04 June 2006, 15:32 Sunday

Another site worth checking out regarding concepts for acoutical treament

Rives Audio

**chasw98** · 04 June 2006, 16:30 Sunday

Originally posted by Evil Twin

Another site worth checking out regarding concepts for acoutical treament

Rives Audio

And ET.... What about Ethan Winer (www.ethanwiner.com) or his company www.realtraps.com. I have had some interesting discussions with Terry Montlick (www.tmlaboratories.com) but I believe he is more EQ oriented than physical, shall we say. And I always go back to "The Big Yellow Book" by Don and Carolyn Davis! (Does that date me?)

Chuck

**ThomasW** · 04 June 2006, 17:51 Sunday

What about Ethan Winer (www.ethanwiner.com) or his company www.realtraps.com. I have had some interesting discussions with Terry Montlick (www.tmlaboratories.com)

They both lose out of the gate to Rives, since Rivers has a much cooler website...... :W

(Does that date me?)

The Zappa stuff you posted dates you buster..... :B :B

**swithey** · 04 June 2006, 23:45 Sunday

Thank you eviltwin -- what a post. I really appreciate the detail!! Thomas and Bryan, thank you too for your input.

Before I ask my comments/questions, let me answer a few of your questions/assumptions about my room (since my AVS thread has grown quite a bit):

1) Room is 100% light controlled. No windows at all. So "outside" light will not be a problem.

2) 1st reflections (walls and ceiling) and RT60 times are being addressed and I have a pro helping me with absorption thickness, locations, etc. So, I should be covered there but totally understand your concern about that. In a nutshell, I will have panels on the walls filled with a TBD thickness of OC 703.

3) I will have 2'x1.5' bass traps in each of the front corners as well as 3" thick x 22" wide x 42" tall traps on the rear wall. I cannot utilize the corners because I have door in one of those corners. And the panel cannot go from floor to ceiling based on WAF.

4) The panels to absorb 1st reflections as well as along both walls and in the rear of the room are a dark chocolate brown. Walls will be painted a darker color also (well as dark as the wife will allow -- we're still trying to figure that out).

You can fine more detail HERE (kind of a summary post)

Now my thoughts...

Yes, a smaller screen would make life a bit easier. Bpape has said more than a few times to tame my screen size down. My original plan was for a 110" diag 1:78 screen (96" wide) -- just as you guys suggested. However, I was really eyeing 2.35:1 material and thought it might be a little small on a 96" wide screen. However, because only about 40% of the movies out there are scoped at 2.35:1 and that I watch HGTV and all those 1.78:1 Pixar movies (aka. kid movies), I wanted to maximize both environments as much as possible. I have been playing around with the idea of a 9' wide 1.78:1 screen as a compromise. However, this would only move the speakers in toward the center another 6". And, since this screen is "taller" than the original slated 2.35:1 screen, I would need to move the screen up to get the center at the "dreaded" 18" from the floor

DIY speakers are an option for me. I am very handy with wood and electronics but speaker and x-over design are something I've never done before (but am up for the task). I've been reading about the Dayton towers that are sticky'ed. They do look like could perform quit well for the price. The only concern I have about them are all the designs use aluminum/metal tweets. I just not sure if I will like that sound. However, with that said, I do love the Paradigm sound and they use metal tweets. So, I'm just a confused listener.

I know you have issues with my L/R speakers and their proximity to the wall but IMO a phantom just does not work for me. I've tried it in the past (maybe not in a perfect environment) and I did care for the way it impacted the surround experience. I really cannot explain how but it just did not sound right. So, I guess I may be stuck with either a DIY speaker with a special x-over or the baffle design bpape suggested. I'd prefer the DIY design but making the x-over will be over my head. I do have some drivers and design ideas in mind for my DIY speaker, though. I have thought about contracting the x-over out but still thinking about it.

Any my questions:

1) It looks like the idea of an IB sub in the front of the room (be it in the rear or the front of the false wall area) will have some boundary issues you don't think will perform well. Am I correct in this assumption? You seemed the most comfortable with #3 Boundary Effect but that appears to use a ported sub 6.5' from the rear of the room which is where my seating is. The (2) locations I have available in my room for sub(s) in/behind (IB) the false wall area and in the back left corner of the room.

2) I do love bass but was wondering based on my room size (about 2500cu/ft) will (2) SS 15" in an IB setup be plenty for my room -- or will I crave more? Should I consider (2) ported subs (one in the back and one in the front) to balance things out a bit because of my "troubled" room?

3) If I could somehow put the center above the screen, would that help things out any? The ceiling vaults from 8' to 10' at that level so it would have more room to breath. The only issue is I may have to drop the screen a bit more to allow enough room for the speaker. See my pic to understand the room layout -- notice the vault inside the false wall area which restricts depth unless it is pushed down a bit. Of course, I would need a front-ported center to perform better in this location -- right? X-Over will be set globally at 80Hz (as bpape stated earlier).

Image not available

**KJP** · 05 June 2006, 13:19 Monday

The boundary issues dont just effect IB installs but standard box speakers as well.

I agree with the notion that your screen is probably too big for that room. Sorry if this has been asked but what projector will you be using?

That said I have heard "over/under" center installs and would prefer that to dragging the center image to the floor/ceiling or doing a phantom center.

**ThomasW** · 05 June 2006, 13:40 Monday

This is a really nice theater and I think you want to invest the money for 4-15"s. It maybe too much sub, but with the increasing use of subsonics in soundtracks, too much sub may turn out to be just enough..

Dennis' thought with the dual centers maybe just the ticket if you do DIY speakers. Might start with the one below the screen and add the upper later if needed/wanted

With any DIY speaker design you can contour the crossover do work with the location. Something not easily done with a premade design.

RE: multiple position subs. Since the room is basically square you have bass issues from the starting gate. Obviously Bryan has worked with square rooms before, (something I've been lucky enough to avoid)

I'd build the IB (on the rear wall of the front section) then do a series of in-room measurements to see how real world plots compare to the computer sims, if you need a rear sub you'll know then...And you'd want to use a sealed low Qtc box design to even out the in-room response, since it's the best match to an IB.

**swithey** · 05 June 2006, 13:50 Monday

Originally posted by Dennis H

Well, here I go again, tooting my unpopular 3rd party line of dual centers above and below the screen, fully recognizing that I may suffer a remote choke hold from ET.

Jon proposes an L+R phantom center but let's think about that. The left and right tweeters will be about 130" apart and the seats may be as much as 80" apart on that horizontal axis. With dual centers, the tweeters will be about 62" apart and the seated listeners' ears will all be within 6" or so on the vertical axis. Which will have the worse comb filtering? Inquiring minds and all that.....

Edit: However, Evil Twin and I agree strongly that having a center on the floor or the ceiling sucks bigtime. Who wants to hear voices from a singer 1' tall or 9' tall? The (real or phantom) center needs to be at the same height as the L&R both for voices and smooth pans.

Dennis,

Seems your idea has gotten a few more votes (thanks KJP and Thomas). On "paper" the dual center has always sounded like a great solution but I have ready multiple times that it is a real no-no for reasons already discussed. However, if there is a chance it might work, Thomas's approach to try lower to see how it works and add an upper if it is needed, maybe an option.

**swithey** · 05 June 2006, 14:16 Monday

Originally posted by ThomasW

This is a really nice theater and I think you want to invest the money for 4-15"s. It maybe too much sub, but with the increasing use of subsonics in soundtracks, too much sub may turn out to be just enough..

My thoughts exactly! :T

Originally posted by ThomasW

Dennis' thought with the dual centers maybe just the ticket if you do DIY speakers. Might start with the one below the screen and add the upper later if needed/wanted

This will be considered and I like your idea of rolling them out as needed. Assuming I only have 7 channels on my amp and 7 speakers, I would need to use a single amp channel to power both centers. I should be able to adjust the gain in my Pre/Pro to level them out. BTW, I think I'm going separates-- either the Outlaw Audio 970 Pro/Pro and 7125 Amp or the Sherwood Newcastle P-965 Pro/Pro and A-965 Amp. Yes, I could buy a 2-channel amp just for the centers but my budget is stretched as it is getting one of the setups above.

Originally posted by ThomasW

With any DIY speaker design you can contour the crossover to work with the location. Something not easily done with a premade design.

Might have to head over to the Dayton DIY area and see what I can find out there.

Originally posted by ThomasW

RE: multiple position subs. Since the room is basically square you have bass issues from the starting gate. Obviously Bryan has worked with square rooms before, (something I've been lucky enough to avoid)

I'd build the IB (on the rear wall of the front section) then do a series of in-room measurements to see how real world plots compare to the computer sims, if you need a rear sub you'll know then...And you'd want to use a sealed low Qtc box design to even out the in-room response, since it's the best match to an IB.

I think I can live with that. The wife would love anything that could be hidden to be hidden so let's hope I will not need to put a sealed sub in the back corner unless necessary. BTW -- Sorry for my ignorance, but what does "low Qtc Box" mean?

**ThomasW** · 05 June 2006, 14:31 Monday

Raw loudspeakers have T/S parameters. I'm lazy so here's the info from the 12volt website

Q Parameters "Qms, Qes, and Qts are measurements related to the control of a transducer's suspension when it reaches the resonant frequency (Fs). The suspension must prevent any lateral motion that might allow the voice coil and pole to touch (this would destroy the loudspeaker). The suspension must also act like a shock absorber. Qms is a measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs. Qes is a measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock. Qts is called the 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same.

When the driver is mounted in a box there's a total "Q" of the system, that's the Qtc. A low "Q" box is 0.50. That's called 'critically damped'. And it's the closest one can get in a portable box sub to the 'sound' of an IB.

**Dotay** · 05 June 2006, 14:33 Monday

Originally posted by swithey

Might have to head over to the Dayton DIY area and see what I can find out there.

No need to travel that far.

Dayton WMTW Center

**swithey** · 05 June 2006, 14:36 Monday

Originally posted by KJP

I agree with the notion that your screen is probably too big for that room. Sorry if this has been asked but what projector will you be using?

These are the projectors I'm looking at (all at or under 3k street):

- Infocus IN76 (DLP)
- Optima HD72 (DLP)
- BenQ PE7700 (DLP)
- Panasonic PT-AE900U (LCD)
- Epson PowerLite Cinema 550 (LCD) (LCD)

One last model I really like is the Samsung H710 (DLP). It's performance is suppose to meet or beat Optima H79 for quite a bit less (around 3k street).

All have positive and negative points but, depending on screen size, I may have to rule a few of them out anyway (I won't bore you with the details). Based on a lens at 15.5' from the screen, some can do something as small as an 8' wide 1.78:1 screen but some cannot. If I go with a 9' 1.78:1 screen (maybe even 8.5'), all the projectors listed above can work in my room. Overall, the Panny has the most flexible zoom but the picture might be a bit soft for my tastes. The Infocus IN76 looks good too. So, to answer your question, the jury is still out.

**swithey** · 05 June 2006, 17:59 Monday

Originally posted by Dotay

No need to travel that far.

Dayton WMTW Center

Thanks Dotay. I've been lurking around over there from a while -- guess I need to dive in a bit.

**KJP** · 05 June 2006, 23:19 Monday

Originally posted by swithey

These are the projectors I'm looking at

So they are all 720x1280 models. To me that makes them all essentially the same and IMO the difference between them become moot by running them so large.

You room diagrams look to put you about 10.5 ft from the screen, from a 128" screen displaying 720x1280. I implore you to seek out a 720 setup on 128" and make sure that is going to be ok with you. I have not seen 720 that big, I have seen a few 120" at 720 with $10-15k projectors and did not find them to be very pleasant looking. I am way more picky than most people when it comes to video, so a YMMV disclaimer is in order here :T