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post #451 of 1113 Old 03-08-2014, 02:56 PM - Thread Starter
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Update:

*Front wainscot is now at the right height
*Painted the bottom of the soffit today (took longer than I expected)
*Bought some more UltraTouch (sale ends tomorrow)
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post #452 of 1113 Old 03-09-2014, 06:25 PM
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Quote:
Originally Posted by dlbeck View Post

Update:

*Not too much to report the last couple days. The trimmers should start back up tomorrow.
*Received all the 2" & 4" OC703 that I ordered from ATS Acoustics. The 4" is for the ceiling treatments and the 2" is for behind the screen per Nyal's acoustic plan.
*Finalized carpet color and style and ordered
*Decided to put rear speakers in rear columns. Original plan was to put them on the face of the rear soffit.

I think that's a good decision...it would be a shame to cut up that nice soffit. smile.gif
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post #453 of 1113 Old 03-10-2014, 01:47 PM
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I searched AVS and found another build that had blue plum. Here is a blue plum "wainscot." I really like that color.

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post #454 of 1113 Old 03-10-2014, 06:11 PM
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I made some progress this weekend on the MBM's for The Savoy. Each one uses a little over 1 sheet of plywood.

Here is the cut plywood all stacked and ready to put together for two MBM's:



You can see a finished MBM for comparison:


I first attach the baffles to the sides. These are all cut exactly the same height.. If you use a circular saw to cut your boards you can use a flush cut router bit to make all baffles/sides the height of the shortest board. In this picture the MBM is rotated. Those are the sides and not the top/bottom.



I cut the top/bottom about 1/8" oversized which leaves about 1/16" all around. After they are attached, I trim the with a flush cut router bit. This ensures your edges match exactly and allows your assembly to be a little out of square. You can see the slight overlap in the red circle. I use a single clamp and PL Premium glue to assemble everything. While clamped, I use 18 gauge nails to hold it together.



After I flush cut the top/bottom, I then attach the second front/back baffle. This is also over sized and then flush cut. For these you don't even need to wipe off any excess glue. You can just let it dry and the flush cut bit will clean up excess glue. Now you have a box that has all the sides matching exactly. I then use a roundover bit on all corners.

Here are all MBM's ready for Bondo.

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post #455 of 1113 Old 03-10-2014, 06:50 PM
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Quite the tower of power you have created .
So what do they neighbors think??

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Check out a video of my theater here
CuznEddy Cinema
Officially Hanesamatized on 8/1/09

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post #456 of 1113 Old 03-10-2014, 07:21 PM - Thread Starter
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post #457 of 1113 Old 03-11-2014, 09:55 AM
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Haha, great picture! Quadruple chest pounders.

Do they need any bracing from front to back or does that not matter as much since they won't be needed for very low frequencies?
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post #458 of 1113 Old 03-11-2014, 11:32 AM
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I Bondo'd my sub that I built last fall. It was a lot of extra work, but made for a nicer finished product.

Are you going to "groove" the seams and fill them with Bondo too so that the seams never "crack" or show down the road?
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post #459 of 1113 Old 03-11-2014, 11:55 AM
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Quote:
Originally Posted by carp View Post

Haha, great picture! Quadruple chest pounders.

Do they need any bracing from front to back or does that not matter as much since they won't be needed for very low frequencies?

The front and back are double walled so they are 1 1/2" thick with both Green Glue and PL Premium between them so officially it is triple layers. wink.gif

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I Bondo'd my sub that I built last fall. It was a lot of extra work, but made for a nicer finished product.

Are you going to "groove" the seams and fill them with Bondo too so that the seams never "crack" or show down the road?
For those that don't know, here are a couple pictures of what is meant by "groove" the seams:




No, I won't groove them although my Makita track saw could probably do it pretty quick. It has a built in depth stop for 1/16" inch for preliminary cuts to prevent any tear out. These MBM's are going in dlbeck's screenwall behind the AT screen. They don't need to be absolutely perfect (I hope). I haven't had any other subs crack at the seams later on. The PL Premium probably helps with that. Also, the Duratex seems to resist any cracking.
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post #460 of 1113 Old 03-11-2014, 12:10 PM
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damelon (The Bacon Race Theater) bought almost $4000 is Submersive subs, and they were coated in a Duratex type of material, and you can see the seams. Then again, in his case he got a better price for going with the lower grade finish, and his are behind his screen wall...

Submersives with seams
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post #461 of 1113 Old 03-11-2014, 01:05 PM
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Quote:
Originally Posted by desertdome View Post

The front and back are double walled so they are 1 1/2" thick with both Green Glue and PL Premium between them so officially it is triple layers. wink.gif

Wow, yeah I would say that is a study enclosure.... understatement. cool.gifsmile.gif
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post #462 of 1113 Old 03-11-2014, 02:10 PM
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Quote:
Originally Posted by desertdome View Post

The front and back are double walled so they are 1 1/2" thick with both Green Glue and PL Premium between them so officially it is triple layers. wink.gif

Wait, so you are saying that you used PL Premium AND Green Glue between the two layers? Doesn't the PL Premium negate any benefits of the Green Glue? Or maybe more correct, why even bother with Green Glue if you are using PL Premium? Green Glue isn't really glue at all. It stays sticky and pliable and doesn't "dry". PL Premium is a SUPER adhesive (glue) that does dry.
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post #463 of 1113 Old 03-11-2014, 03:00 PM
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I asked David to bring some Green Glue since I figured he had some extra laying around. He wasn't at his new house and bought a tube from Menards so I used it anyway. The PL Premium was used in a few small dots at the corners to provide adhesive strength with the Green Glue covering the rest of the area to remove any panel resonance. I don't think the hardness of the PL Premium is affecting the damping of the Green Glue. Since Green Glue acts as a damping layer, I figured it could only help. The panels are also nailed together.

Some people use mass loaded vinyl in their subwoofers/speakers as a damping layer. You can see here a comparison with Green Glue:

GREEN GLUE VS. MASS LOADED VINYL (MLV)
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post #464 of 1113 Old 03-11-2014, 03:27 PM
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I see what you did... I was thinking that you intertwined the Green Glue and the PL Premium together. What you did is find acoustically.
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post #465 of 1113 Old 03-11-2014, 04:15 PM
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Will the MBMs be placed around the room or in the same vicinity as the subs? I anticipate greatness with this build in all regards.
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post #466 of 1113 Old 03-11-2014, 04:25 PM - Thread Starter
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Three of the MBMs will be the "stands" for the LCR. The fourth MBM will be in the back of the room supplementing the surrounds with mid bass.
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post #467 of 1113 Old 03-11-2014, 04:52 PM
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Quote:
Originally Posted by dlbeck View Post

Three of the MBMs will be the "stands" for the LCR. The fourth MBM will be in the back of the room supplementing the surrounds with mid bass.

What electronic crossover will you be using?  With the three MBM's stacked with LCR, perfect alignment for sending full LCR signal to each pairs for full range effect.  How low with the MBM's?  40.............50 hz?  Two S2's can definitely handle below 40 hz quite well.

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post #468 of 1113 Old 03-11-2014, 05:14 PM - Thread Starter
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Originally Posted by doublewing11 View Post

What electronic crossover will you be using?  With the three MBM's stacked with LCR, perfect alignment for sending full LCR signal to each pairs for full range effect.  How low with the MBM's?  40.............50 hz?  Two S2's can definitely handle below 40 hz quite well.

Hey Doublewing - some of this is explained in the original post but it sure doesn't hurt to recap. I am using JRiver to set the crossovers and that outputs to a SSL Alpha Link D-A/A-D converter that can handle 16 channels. The plan currently is to utilize the MBMs from 40-150Hz. S2's will handle below and the 212's will handle above 150.
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post #469 of 1113 Old 03-11-2014, 05:38 PM
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Quote:
Originally Posted by dlbeck View Post


Hey Doublewing - some of this is explained in the original post but it sure doesn't hurt to recap. I am using JRiver to set the crossovers and that outputs to a SSL Alpha Link D-A/A-D converter that can handle 16 channels. The plan currently is to utilize the MBMs from 40-150Hz. S2's will handle below and the 212's will handle above 150.

Thanks..............

 

This thread is growing like an ant colony.............................guess that explains how you are planning on doing it........too lazy to search...........sorry!  Makes perfect sense though I'm not familiar with either JRiver or other dac. Much more cost effective than what I plan to do.............and will most likely out perform my plan too.  :cool:

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post #470 of 1113 Old 03-11-2014, 05:54 PM - Thread Starter
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Thanks..............

This thread is growing like an ant colony.............................guess that explains how you are planning on doing it........too lazy to search...........sorry!  Makes perfect sense though I'm not familiar with either JRiver or other dac. Much more cost effective than what I plan to do.............and will most likely out perform my plan too.  cool.gif

All good...I don't mind answering questions at all. These threads get so long it takes forever to find the answer you are looking for. Trust me, I asked Mario plenty of questions eek.gif

I looked at other options like the QSC (recommended by EG) but it was a lot more money and it was difficult to configure. I'm sure they work great along with products such as the Trinnov and Lake processors but those are out of my league. I believe JRiver will work perfectly for me.
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post #471 of 1113 Old 03-11-2014, 06:00 PM - Thread Starter
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Update:

*Today was fabric frame completion day.

Picture of the ceiling fabric frames (top of picture) that will conceal the 4" OC703 on the ceiling


Picture of the room with the frames roughly laid out where they will eventually go


Picture of the fabric frames for the stage front
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post #472 of 1113 Old 03-11-2014, 06:29 PM
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All the things listed that you'll be using J River is awesome. I've just recently assembled a HTPC and was interested in J River to eq among other things. Would I need a DAC to carry that out or?
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post #473 of 1113 Old 03-11-2014, 06:43 PM - Thread Starter
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Quote:
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All the things listed that you'll be using J River is awesome. I've just recently assembled a HTPC and was interested in J River to eq among other things. Would I need a DAC to carry that out or?

gpmbc - DesertDome may chime in but wanted to send you this link. Nyal has started some good threads on this topic and also links to some of his blogs on his website.

http://www.avsforum.com/t/1476117/how-to-replace-your-home-theater-pre-pro-with-a-htpc/0_100
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post #474 of 1113 Old 03-11-2014, 06:53 PM
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Thx for the info.
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post #475 of 1113 Old 03-11-2014, 07:37 PM
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Quote:
Originally Posted by dlbeck View Post

Hey Doublewing - some of this is explained in the original post but it sure doesn't hurt to recap. I am using JRiver to set the crossovers and that outputs to a SSL Alpha Link D-A/A-D converter that can handle 16 channels. The plan currently is to utilize the MBMs from 40-150Hz. S2's will handle below and the 212's will handle above 150.
Just a quick correction - I was planning on having the 212's still play down to 70 Hz. The S2's will still get the LFE channel with frequencies up to 120 Hz.
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post #476 of 1113 Old 03-11-2014, 10:06 PM
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Quote:
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Just a quick correction - I was planning on having the 212's still play down to 70 Hz. The S2's will still get the LFE channel with frequencies up to 120 Hz.
So where do the midbass come into play?
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post #477 of 1113 Old 03-12-2014, 08:27 AM
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I posted this info on the JTR thread a couple weeks ago. It explains the background into why David is using MBM's so I thought I'd post it here.

There is a reduction of SPL caused by deconstruction interference between the direct sound of a speaker and the reflected sound. This cancellation is called Speaker Boundary Interference Response (SBIR) or Allison Effect. It is discussed in the Acoustical Treatments Master Thread, at GIK Acoustics, and elsewhere. Since the effect is based on the speaker's position, the cancellation occurs regardless of where you sit.

SBIR's effect can be calculated by the following formula: Speed of sound (1130 ft/s)/distance in ft X .25
The formula can be simplified to 282.5/distance in ft
This is 1/4 wavelength and can also be calculated using the calculator at Real Traps and viewing the 1/4 wave frequency.
For a speaker 2 ft from the front wall, the cancellation occurs at 141.3 Hz (285.2/2).

For most people, SBIR causes issues with their midbass since the cancellation ranges from 80-200Hz.

There are several ways to reduce/eliminate SBIR:
1. Use a baffle wall. This eliminates reflected sound.
2. Use absorption on the front wall. It takes a lot of absorption to reduce reflections at the midbass frequencies.
3. Position sub(s) and speakers so they each have interference at different frequencies. Set the crossover around the 1/4 wavelength frequency. This will help get a little overlap. The problem is that many use subs with lots of excursion for low frequencies. Some of these rolloff early above 80 Hz or have lots of distortion (IMD). If playing below 40 Hz, you don't want the sub playing above 150 Hz.
4. Use an MBM in a different location and overlap the midbass frequency range. For example, you can use a 200 Hz low pass on the MBM and a 80 Hz high pass on the speaker. They will then overlap in the problem frequency range. To correct the SPL, you use a high or low shelf filter.

#4 is basically the same as using flanking subs as advocated by Wayne Parham. In order to get the maximum midbass coverage, the driver of the MBM should be a different distance from both the front wall and side wall than the speaker. I think Wayne recommended no more than 4 ft away, though, so their aren't audible timing issues in the frequencies. The MBM under the speaker changes the speaker to floor distance, but the other two are the same unless you rotate the MBM so it faces a different direction.

Below 1/4 wavelength the direct/reflected frequencies couple and you get bass reinforcement.
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So where do the midbass come into play?
The MBM's will be used like #4 above. However, now that there is a baffle wall SBIR is less of an issue and the MBM's will be placed below the speakers. The floor to driver distance is still different for speaker vs MBM so these cancellations will be mitigated.

I started a thread in the DIY Speakers and Subs forum documenting the MBM's:
Acoustic Elegance PB18H+ Sealed Build x 4
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post #478 of 1113 Old 03-12-2014, 10:26 AM
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How does one seamlessly integrate a mbm with the speaker? Any rifts in continuity would be very apparent at the upper crossover point, I would think. It would take some expert calibration to make this happen. Then again, this is a forum full of experts; it might not be that difficult to pull off after all.
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post #479 of 1113 Old 03-12-2014, 11:28 AM
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How does one seamlessly integrate a mbm with the speaker? Any rifts in continuity would be very apparent at the upper crossover point, I would think. It would take some expert calibration to make this happen. Then again, this is a forum full of experts; it might not be that difficult to pull off after all.
That is a good question. They will be integrated just like you would when designing an active speaker. If the varying crossover points don't work out so well, one can also use a crossover in the midpoint, such as 110 Hz, and use very shallow slopes. This still provides overlap of the speaker/MBM for a couple octaves.

Paul Spencer's Bass Integration Guide discusses subwoofer and speaker overlap and the benefits it provides. The approach I'm suggesting is similar with higher crossover points.




I have two of David's 212HT-LP speakers. As soon as I finish two of the MBM's these will go in my living room and I can show some measurements. I hope to do the following:

Close mic of 212HT-LP showing native frequency response and phase
Close mic of PB18H+ showing native frequency response and phase
In room measurements of each showing the effect of the room
Measurements of various crossovers and other filters showing frequency response and phase - the MBMs might also be moved closer to the walls to for a different SBIR than the mains

I'm looking forward to experimenting. cool.gif
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post #480 of 1113 Old 03-12-2014, 06:46 PM - Thread Starter
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Update:

*Bar supports were completed
*Progress on the main entrance door
*Transported the 42 fabric frames to an off-site fabric frame processing facility (my basement). Will be painting and wrapping them in fabric over the next couple weeks



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