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Old 22nd June 2013, 03:30 PM   #11
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You said that you don't like resonances, but I see all the drivers attached by the baskets.
Why don't you suspend 'em with rubber bands ?
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Old 22nd June 2013, 03:46 PM   #12
DrDyna is offline DrDyna  United States
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Quote:
Originally Posted by puppet View Post
My OB attempts have evolved into something like this recently. It's active 4-way and sonically is the best thing I've tried so far. An H or U frame can help boost the lower end but the resonance(s) aren't for me ... after trying it without. I have been using 3rd order bessel elect filters with spread frequencies to knock down the peaks at the various xo points. Simple enough to do.

The 15" driver has a 6db shelf w/5db boost starting @ 320hz .... his HP is 144hz or so. The 12" lower mid is rolled off @ 80hz .... varying this can allow a petty large contribution to the low end or not depending on the room or one's listening tastes.

Sorry that I don't have proper data to offer, however, I think it's worth a look see Doc.
Oh, that looks like a big Heil, I already love it.

As far as the sonic size and having the upper driver, that was when I was considering having those drivers play a bit higher than 200 hz, my original plan was 300hz...or maybe even more, if my measurements and MiniDSP coaxing could work it out. It's really only after some discussion that some have said having them play up that high is probably a bad idea...although that was when we were talking about H frame resonances...now that they're just on a flat baffle (and going by the measurement) the first phase swing doesn't happen until quite a bit higher than 300 hz, so...now I'm wondering.

Would, say, WMTW be bad if they're all on a flat baffle? In my head I imagine something like 72" h x 18" (maybe more) w.

WAF isn't really a factor here and I don't mind if my speakers dominate the room.
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Old 22nd June 2013, 03:57 PM   #13
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Hi DrDyna,

Why don't you start with something simple ?
A 3 ways WWMT ?
WW HFrame til 100Hz
MT simple 8"+1" above 100Hz.
Something like Linkwitz Orion, simple and efficient.
I think OB is difficult to make sing right, a lot diffraction problems. Small surfaces on openbaffle is very tricky.

Just my 2cents
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Old 22nd June 2013, 04:13 PM   #14
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Quote:
Originally Posted by DrDyna View Post
Oh, that looks like a big Heil, I already love it.

As far as the sonic size and having the upper driver, that was when I was considering having those drivers play a bit higher than 200 hz, my original plan was 300hz...or maybe even more, if my measurements and MiniDSP coaxing could work it out. It's really only after some discussion that some have said having them play up that high is probably a bad idea...although that was when we were talking about H frame resonances...now that they're just on a flat baffle (and going by the measurement) the first phase swing doesn't happen until quite a bit higher than 300 hz, so...now I'm wondering.

Would, say, WMTW be bad if they're all on a flat baffle? In my head I imagine something like 72" h x 18" (maybe more) w.

WAF isn't really a factor here and I don't mind if my speakers dominate the room.
Here's some info on an OB/nude prototype that I built recently, and used with a pair of the MiniDSP 2x4s. Pic:

Click the image to open in full size.

Frequency Response on and off axis:
Click the image to open in full size.

It's from this system that I learned the things that I wrote in post #2 of this thread.

Anyway, this was easy to build, looks ugly (it's a prototype after all) but sounds great. I used it with a pair of 12" subs and this was OK in a small room but in a large room was horrible. I am currently planning the next version that will include u-frame subs.

Drivers are the Exodus Audio Anarchy (6.5") on the baffle, Seas MP12vc midrange, and Tang-Band W2-800SL. The mid and tweeter are operated nude. The high location of the woofer helps to smooth out the ripples in the frequency response that result from the open baffle loading. The baffle is 24" wide and 30" high. I initially used a 24"W x 48"H baffle and that was also good, but I ended up not needing such a tall baffle because I crossed over the woofer to the subs at 100Hz. In the USA,I can buy sheet goods (like MDF) precut to 24x48 so mt first try was just done by mounting the drivers without any cutting of the sheet.

-Charlie
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Old 22nd June 2013, 04:23 PM   #15
DrDyna is offline DrDyna  United States
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Here's what I was testing, this is what I got the measurement from yesterday (I held a piece of wood over the mid cutout and had someone else click measure :P

Edit: I probably won't stick with this baffle though, I really think it should be wider...and when I put in the Neo3, I was thinking of making a square cutout around 8 inches and suspending it with wire.
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Last edited by DrDyna; 22nd June 2013 at 04:27 PM.
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Old 22nd June 2013, 04:32 PM   #16
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A large u-frame properly stuffed with Bonded Logic or fiberglass (see John K) can damp the cavity resonance of the u-frame........in theory anyways. I haven't done it personally but I intend to sometime this year. More of a super-cardioid pattern but at these low freqs the room modes will dominate as Rudolph points out.
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Old 22nd June 2013, 04:54 PM   #17
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And...just for kicks, I stuck an Eton 7-360 Hex that's been in my driver bank for nearly 15 years into the midrange slot and measured it.

This is a lot better than I expected.
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Old 22nd June 2013, 05:03 PM   #18
Rudolf is offline Rudolf  Germany
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Quote:
Originally Posted by DrDyna View Post
Here's what I was testing, this is what I got the measurement from yesterday ...
The H frame is 12" deep and - I guess - 12" from the front wall? That is way too near. Make the distance from wall to baffle at least 3-4 feet. The mic distance is ok, if it is at least 2x baffle width.
Quote:
Edit: I probably won't stick with this baffle though, I really think it should be wider...
... because of ...?
Quote:
... and when I put in the Neo3, I was thinking of making a square cutout around 8 inches and suspending it with wire.
A good point to start from
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Old 22nd June 2013, 05:13 PM   #19
DrDyna is offline DrDyna  United States
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Quote:
Originally Posted by Rudolf View Post
The H frame is 12" deep and - I guess - 12" from the front wall? That is way too near. Make the distance from wall to baffle at least 3-4 feet. The mic distance is ok, if it is at least 2x baffle width.
... because of ...?
A good point to start from
The H- Frame isn't being used atm, it's really just a stand. Right now I'm seeing if I can get just the top 3 way going, which is the reason I was thinking a wider baffle might help the 831757 go a little lower so it won't be a trapeze trick to get the subs to come up and meet it.

The mic is about 25" away, but I move it between where it is and ~ 40 inches and scoot it around to check various distances.
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Old 22nd June 2013, 05:23 PM   #20
Rudolf is offline Rudolf  Germany
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Quote:
Originally Posted by DrDyna View Post
The H- Frame isn't being used atm, it's really just a stand.
The H frame was only a means to guess the baffle distance from the front wall. Just make sure that your baffle is at least 3 feet from the front wall. Below that the bass response will drop severely.

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