MCM 21" tuned LOW thoughts? - Page 4 - diyAudio
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Old 4th March 2014, 10:57 PM   #31
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Join Date: Dec 2011
Location: NC
Quote:
Originally Posted by a.wayne View Post
Finish the 2002 yet , what about the 21 inch sub ...?
The 2002 is not done There "only" thing left is to finish the wiring under the dash and exhaust work. Sadly the wiring is taking much longer than anticipated and I haven't had much dedicated time at all lately to work on it.

My 21's are still hanging from the ceiling. I love them there as they do not take up any floor space. I did draw up some more OB designs, however I do not have any plans to build them as of right now. The ported 21 idea was just that, an idea and was mainly looking for feedback. I feel that you can get much more bang for your buck and space by going with some SI HT 18s or some FI subs. I think those would be better choices. If I had to do it all over again, 4 18s from either SI or FI would be the ones I'd get.
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Old 4th March 2014, 11:00 PM   #32
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@CharlieLaub

The OBs are about 24" out from the rear wall. The right panel is only a few inches from the wall and the left is about 6-7" away. The total open area is rather large, so I was not expecting any resonances to occur. If my room was larger, I would have much liked to keep the drivers on the floor to get some good "bounce" and a bit further from the rear wall.

I'm looking forward to your prototype.
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Old 15th July 2014, 09:30 PM   #33
Decker is offline Decker  United States
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Well, I bought the woofers in April of 2013 and now it is July of 2014 and the boxes are finally done and I am getting ready to put the woofers in them. I decides to go with 24" square by 16" deep U-frames. The actual cone of the woofer is 18" across, so that is the size of the mounting hole for the woofers. I have taken pictures of the build as it progressed. After they are running I will post the photos and comment on the success or lack thereof.
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Old 15th July 2014, 10:07 PM   #34
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Thanks for the update and can't wait to read about the results.

It's moving time at my house - everything's getting packed up over the next three/four weeks and we're moving about a third of the way across the country.

Probably a new set of OBs will follow
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Old 17th July 2014, 04:35 PM   #35
Decker is offline Decker  United States
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WOOHOO! Finished the boxes, mounted the woofers and plugged them in. (Pardon my exuberance, but I am always amazed when something I build works the first time Sensitivity is about the same as the Alpha 15s on open baffle that they are replacing. Didn't get much chance to play them last night. Put on the Stereophile test CD #2, bass tracks, and got solid response down to about 30 hz or so. Put on Jennifer Warnes "The Hunter" and actually got a favorable response from the significant other, who normally couldn't care less about what we listen to music through. It was getting late, so I didn't want to annoy my apartment neighbors. Will post pics soon. I did want to mention that I tried a different (for me) box building technique. For this build I used "System 3" 15 minute epoxy, using their cartridges and mixing tubes in a caulking gun. I was originally going to just butt join the boxes, but got cold feet and put in wood bisquits at the joints. Turns out these were not necessary. After doing a dry fit to make sure of my assembly sequence, I squeezed glue on the mating surfaces with the caulking gun, spread it a bit, assembled the first box using a metal strap box clamp. By the time I got the second box set up to assemble, the first box was rigid enough to take the clamps off. By the time I got the second box glued and clamped, the first box was set enough to lift and move around. I didn't use epoxy for the strength, but for the fast setting time. System 3 also makes a 5 minute epoxy, but I don't think I could assemble the boxes fast enough to use it. 2 big boxes assembled and ready for finishing in 30 minutes. I will definitely use this glue for the next set of boxes, which will be new cabinets for my Fostex 166en full range drivers that match the MCM boxes and will sit on top.
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Old 17th July 2014, 05:58 PM   #36
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Quote:
Originally Posted by siruis815 View Post
@CharlieLaub

The OBs are about 24" out from the rear wall. The right panel is only a few inches from the wall and the left is about 6-7" away. The total open area is rather large, so I was not expecting any resonances to occur. If my room was larger, I would have much liked to keep the drivers on the floor to get some good "bounce" and a bit further from the rear wall.

I'm looking forward to your prototype.
Ah, I had forgotten about this thread, and my post. Just re-discovered it now, so I will give a follow up.

Initially I was thinking of a large open baffle subwoofer, something on the order of 2x3 or 2x4 meters (!) with four 12" high-excursion subwoofers mounted around the center line of the baffle and near the floor. But after thinking about it for awhile I became concerned that I would go through an expensive construction project (for such a large structure) only to end up with a resonating system that would not work well as a subwoofer. This is because I was envisioning something placed relatively close to the wall compared to your panel system (see post #15), e.g. on the order of 12" or less. I fear that such a small separation will make it behave like a transmission line or long U-frame, and that has certain drawbacks and introduces additional complexity. For the location in which I want to install the sub, you approach the room from the direction that would be looking at the "side" of the large panel, and something sticking out into the room 24" or more (to reduce the tendency of the rear space to resonanate) would not be well received by my wife! I have now decided to use these drivers for large sealed subs, since they are a perfect match for four plate amps that I current own.

But the original idea of an OB panel sub has not left me, and I may try something along the lines of what you have constructed except on the floor. I have a pair of 18" Peavey LowRider drivers that I can use and have modeled these in a wide floor standing OB (e.g. 30"H x 96"W). The response looks promising. This would also be a lot simpler to construct, even just with some temporary material for the baffle, since it would largely be along the floor. So this is the way that I will probably go with the OB sub concept. Even that might not pass the sniff test by wifey, but it would be something that I can easily pack up and bring to DIY events.
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Old 17th July 2014, 06:30 PM   #37
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Join Date: Jun 2003
Location: Hamilton, was Ottawa (Canada)
You are brilliant, Sky Baffle!

I love it!

Talk about 'out of the box' thinkin' (ba-dum, tish)



This might gain you some extra Hz and dB:

sky baffle- single baffle.jpg



PS And you could make it a more solid, single structure. Is it flush with the ceiling?

Last edited by AudioLapDance; 17th July 2014 at 06:34 PM.
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Old 17th July 2014, 09:26 PM   #38
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Join Date: Dec 2011
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Thanks! It has now been taken down due to the up coming move. Maybe in the new house I'll give it a try...maybe add two more?

Or I'll put them up in my soon to be classroom, but not sure how my boss will appreciate that one?!
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