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post #151 of 171 Old 10-27-2012, 03:33 PM - Thread Starter
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To address my bass needs, I decided to build a subwoofer - a 30.5"-wide THT (Tuba HT). It's total outside dimensions are 36" x 36" x 30.5" (23 cubic feet)

The bass it puts out is ridiculous. The seats in the theater shake. My wife two floors up said it felt like a monster truck was driving through our house. My brother said his balls vibrated eek.gif

Here's a pic up it behind the screen - I outlined it in blue:



I've done new measurements with REW, which I'll be posting the the We Built it, We've measured it, HELP US TWEAK IT thread shortly

Stay tuned!

Black Cat Theater (Now going BIG!)
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post #152 of 171 Old 11-01-2012, 07:01 PM
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What is the status of your wall fabric?
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post #153 of 171 Old 11-02-2012, 07:04 AM - Thread Starter
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Quote:
Originally Posted by Spaceman View Post

What is the status of your wall fabric?

No update there - still just the one top/bottom section done


If you look in the "HELP US TWEAK IT" thread, you'll see that I now need to put in some traps to cover the 80-300Hz range. These could take different forms, so I'm glad the fabric is not put up yet...

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post #154 of 171 Old 01-06-2013, 08:33 PM
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Updates?

-----------------------------------------------
Chase "Fetch"


Current Theater Build
 

New House Build

 

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post #155 of 171 Old 01-07-2013, 07:23 PM
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Just read through, and I really like your design. I had the same plan as you for cooling the HT, down to the Panasonic fans installed in a utility room. I was really concerned about not having enough of a delta between supply and return air temp to make a difference and don't have the budget to install a mini split. My solution is to add a portable ac unit in the utility room, like the ones found at a local HD. http://www6.homedepot.com/acselector/index.html?storeId=10051&langId=-1&catalogId=10053

$400 and cold air supplied! I didn't find one that had the flexible duct, just blows air out through louvers, so I modified a rectangle to 8" register boothttp://www.homedepot.com/h_d1/N-5yc1v/R-202542040/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=register+boot&storeId=10051#.UOuOCXf0-ZQ and duct taped it over the louvers. With the portable AC supplying and the fan drawing return hot air out, all should be well even if I'm dumping the return air back into the utility room. I may change that though now that I think about it. I'll plug it into an outlet controlled by a switch in the HT. I really need to find a wall mount thermostat that can turn on the outlet, but no luck yet.
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post #156 of 171 Old 01-09-2013, 05:21 AM - Thread Starter
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Originally Posted by cdika17 View Post

Updates?

I'm in the process of trying to dampen frequencies between 80-200Hz. I placed another order for OC703 from a local supplier and, just like last time, it's taking them forever to get it in. I have three ideas as to what to do with it and likely will do them all. First I'll replace all the Linacoustic on the back wall with the 4"-inch thick sheets. Next, I'll cut up what's left into triangles having 17" on their hypotenuse and then build "baby" corner traps for 1) some spots behind the screen, 2) around the recessed light tray, and 3) on the floor behind the rear row. I plan to do it in that order and measure in between. Stay tuned!

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post #157 of 171 Old 01-09-2013, 05:40 AM
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You may consider a second sub. Not for output, but it will smooth out the frequency response across the room greatly. I went from having one good row for LFE to having all 3 rows equal. Side benefit is that you will gain output which allows you to run each sub further from its limits.

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post #158 of 171 Old 01-09-2013, 05:51 AM - Thread Starter
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Originally Posted by ragged View Post

Just read through, and I really like your design. I had the same plan as you for cooling the HT, down to the Panasonic fans installed in a utility room. I was really concerned about not having enough of a delta between supply and return air temp to make a difference and don't have the budget to install a mini split. My solution is to add a portable ac unit in the utility room, like the ones found at a local HD. http://www6.homedepot.com/acselector/index.html?storeId=10051&langId=-1&catalogId=10053

$400 and cold air supplied! I didn't find one that had the flexible duct, just blows air out through louvers, so I modified a rectangle to 8" register boothttp://www.homedepot.com/h_d1/N-5yc1v/R-202542040/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=register+boot&storeId=10051#.UOuOCXf0-ZQ and duct taped it over the louvers. With the portable AC supplying and the fan drawing return hot air out, all should be well even if I'm dumping the return air back into the utility room. I may change that though now that I think about it. I'll plug it into an outlet controlled by a switch in the HT. I really need to find a wall mount thermostat that can turn on the outlet, but no luck yet.

This is an interesting idea. Actively cooling the supply's air has a lot of merit.

From reading my thread, you know I struggled some with cooling system - mostly due to static pressure in the supply line and too much noise from the velocity of the airflow. As for cooling itself, it so far seems OK, not great, but good enough that I'm not actively searching for a fix... But if I had to fix it, my first thought was to try to increase the "delta", as you put it, by rerouting the exhaust to dump into a rather large and relatively cooler part of my basement. That way, it seems that, by the time the air comes back to theater's supply, it would've cooled off quite a bit.

An alternative idea I have is to use another fan to actively move air around the whole basement. If you recall the pics of my basement from the early posts, it can be roughly thought of as being shaped like the letter 'C', with the only thing preventing it being an 'O' is a mechanical/storage room (the stairs come down in the middle of the basement). The supply is currently on one end of the 'C' and the exhaust is near the middle of the 'C', in a hallway that leads the supply on one side and the large space on the other. I'm thinking that a new fan could close the loop, that is, make an 'O', by piping air from one side to the other, though the mechanical/storage room, perhaps cooling it off some in the process, which would be good for me since I have some computers in there...

Anyway,since it's outside the theater and the current solution seems OK enough, I'm holding off on playing with it for now. But if it comes around again, I'll give your idea some more thought - thanks!

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post #159 of 171 Old 01-09-2013, 05:58 AM - Thread Starter
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Quote:
Originally Posted by tony123 View Post

You may consider a second sub. Not for output, but it will smooth out the frequency response across the room greatly. I went from having one good row for LFE to having all 3 rows equal. Side benefit is that you will gain output which allows you to run each sub further from its limits.

My issue isn't uneven LFE - actually, both rows seem pretty darn good (no nulls or nodes). My issue is that the LFE isn't being reduced by at least 20dB within 150ms, thus causing it to not be as accurate sounding as it could. My huge corner base traps seem to be doing the trick for the 15-80Hz range, now I need to target this next frequency range. The concern doesn't exist so much for higher frequencies, as the 1" Linacoustic grabs them...

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post #160 of 171 Old 01-09-2013, 08:43 AM
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Some 4" deep QRD's would get down into that range.

-




Is it solipsistic in here, or is it just me?
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post #161 of 171 Old 04-28-2013, 12:17 PM
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Morph1c, do you know if the whisperline fans can be mounted inside a cavity filled with insulation, or do they need to be exposed (i.e. in an attic)? I'm getting my ventilation details ironed out and I need to figure out how to mitigate the fan noise.

Dude, are you made of leprechauns? Cause that was awesome!

The Plains Theater Has Begun
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post #162 of 171 Old 04-28-2013, 05:12 PM
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It has been over 4 months since Morph1c posted on the forum so I'll take a stab at this question. You can stick the fans in cavities, you can surround with insulation, but here is the gotcha. The assembly needs to be treated as an electrical junction and can not be sealed over permanently. You need to provide access via a removable panel and you would be smart to make the access large enough to swap the fan if it were to fail.

Morph if you see this I knew it was a mistake to hang the projector and screen so you could do the acoustical testing.
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post #163 of 171 Old 04-28-2013, 05:28 PM
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Originally Posted by BIGmouthinDC View Post


Morph if you see this I knew it was a mistake to hang the projector and screen so you could do the acoustical testing.

This is what I have done to prevent the very same thing from
Happening to me lol!!
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post #164 of 171 Old 04-28-2013, 05:55 PM
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Thanks, BIG! I'll definitely add an access panel, I just wanted to make sure it wasn't a fire hazard to seal it up in a DD+GG enclosure.

Snickers1, you can add an electric fence to that pretty cheaply if you are still tempted smile.gif

Dude, are you made of leprechauns? Cause that was awesome!

The Plains Theater Has Begun
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post #165 of 171 Old 04-30-2013, 10:34 AM - Thread Starter
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While I managed to install more OC703, I haven't retested the sound yet - it's on my short list now that the bar and AV rack are almost finished. The AV rack has been quite a challenge - building the drawers and drawer fronts myself - at least I got more tools for the effort biggrin.gif Seriously though, the room sounds great and there isn't any room left to put more OC703 if I wanted to. At this point, I can only play with batting and scrim. BIG, We're going to get this thing buttoned up this summer!

Regarding the fan, BIG's response is spot on regarding insulation and access. My fans are outside the theater room, each fan connected to the theater room via 25' of 3M's acoustical flex duct with a number of 90-degree turns in their runs. The fans' noise is not audible through this flex duct. Outside the room, the fans can be heard through their plastic access panels, but it's not loud enough to irritate me.

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post #166 of 171 Old 04-30-2013, 10:55 AM
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Morph, just a little piece of info on the audio testing. A week ago I was over at DIYhometheater's house and he had a guy come in with some audio test gear. He was using a lap top and mic on stand. He kept getting a measurable peak around 60hz. and had a decay response issue as well. His laptop was sitting on one of the chairs. I suggested that we turn off the chairs each with a transformer and luckily they were all on one breaker. DIYHT hit the switch and the graphs flattened immediately in real time. I seem to remember we were getting peaks around 60hz in some of your measurements and that your chairs had big transformers.
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post #167 of 171 Old 05-30-2013, 08:25 AM
 
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any updates? Looking awesome so far, I love the colors.
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post #168 of 171 Old 05-31-2013, 12:33 PM
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Quote:
Originally Posted by Morph1c View Post

To address my bass needs, I decided to build a subwoofer - a 30.5"-wide THT (Tuba HT). It's total outside dimensions are 36" x 36" x 30.5" (23 cubic feet)

The bass it puts out is ridiculous. The seats in the theater shake. My wife two floors up said it felt like a monster truck was driving through our house. My brother said his balls vibrated eek.gif

Here's a pic up it behind the screen - I outlined it in blue:



I've done new measurements with REW, which I'll be posting the the We Built it, We've measured it, HELP US TWEAK IT thread shortly

Stay tuned!

I am curious to learn some more about this.

What is the SPL or DB level at say 20hz ?

-

"Too much is almost enough. Anything in life worth doing is worth overdoing. Moderation is for cowards."
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post #169 of 171 Old 05-31-2013, 12:48 PM
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here is the source link for the Tuba HT some measurements included. Some woodworking experience required. Access to quality Baltic Birch recommended. It is a folded horn design. Imagine putting a subwoofer at the small end of an expanding horn. (Think megaphone) For real world use you fold that horn inside a manageable size box.

http://www.billfitzmaurice.com/THT.html
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post #170 of 171 Old 05-31-2013, 01:01 PM
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Cool link and idea. Thanks!

Why baltic birch ? Just because of the Sound Quality ? Could you replace with MDF ? I've build many sub boxes out of MDF and have a bunch of higher end 15" car subs laying around that I have nothing to do with them. I've ground out of car sound at my age.
It this something I could use a high quality 15" driver- and build as a project ? (I already have dual 12" in my theater, and I am planning a new theater build and won't be ready for such things for a while- but it looks fun to try)

I am wondering if this requires a special type of driver- or would just about any driver benefit ?

-

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post #171 of 171 Old 05-31-2013, 03:01 PM
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All quality sub-woofers are engineered. The operation characteristics of the driver is computer matched/optimized to the the size and type of enclosure and in this case the length and expansion rate of the horn. Do some research there is discussion of the appropriate woofers (relatively inexpensive). recommendations are in the plans which you should buy from Bill. (Cheap)

The plans call for a high quality 1/2 inch thick plywood, and no not a good idea to try to use MDF. I've built plenty of speakers with MDF. Trust me this design requires quality plywood. You will be doing a lot of screwing into the edges and you can't do that with 1/2 MDF. Baltic Birch is a high ply count void free plywood. Unfortunately something you don't usually find at the big boxes. SandPly has been used by some.
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