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Old 25th May 2004, 02:55 AM   #1
MtnBob is offline MtnBob  United States
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Default OB subs: Best compromise?

Since we can't have everything when it comes to T/S params, what compromises work the best or hurt the least? For example, which of these would you chose? (Assuming all are about the same $) All are 15.

Qts Fs SPL Xmax
driver 1 1.446 40 92 4.05
driver 2 .88 25.6 87.3 14
driver 3 .7 29 92 9.4
driver 4 .67 26.7 90 6

I want accurate music reproduction first, HT second. Not worrying about impressing (or bothering) the neighbors - nearest is about a quarter mile

Im thinking of possibly putting these in an H-frame, approx. 24x36. Could I set it on the long side and put the TV on top? Well, I know I COULD, but is it a good idea?

If I do a W frame is there a simple way to calculate the spacing of the middle section? Sorry, No hablo calculus.
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Old 25th May 2004, 03:11 AM   #2
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Probably driver 2. Relatively low Fs, the highest Xmax, decent sensitivity.
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Old 25th May 2004, 03:13 AM   #3
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If you brace the frame well enough, you can stack anything on top of it.
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Old 25th May 2004, 03:20 AM   #4
MtnBob is offline MtnBob  United States
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Thanks for the opinion. Sorry the formatting got messed up on the table, but I guess you figured it out. I would really like to use #1, it;s a cool looking alunimum cone, but that high Fs bothers me some, not sure if it would give me the opening notes of also sprach zarathrustra - I want to feel it.
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Old 25th May 2004, 03:25 AM   #5
tom1356 is offline tom1356  United States
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I agree with number two.
Scale this up to a 15" driver.
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File Type: gif d_woof1.gif (7.8 KB, 347 views)
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Old 25th May 2004, 03:50 AM   #6
MtnBob is offline MtnBob  United States
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Thanks, Tom. I've got that gif saved somewhere. WHen I said middle section, I was thinking of a design I saw where the drivers were facing each other. Wonder where I saved that?
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Old 25th May 2004, 04:07 AM   #7
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I gotta go with the croud and vote for door # 2 due to the Fs and Xmax. Loosey goosey (quite high Qts) at 40hz seems like a problem I wouldn't want to have to design around for driver #1, at least not for a sub.

Regarding cavity width for a W baffle, I had the same question and couldn't find a hard answer. The height and depth dimensions can result in cavity resonances, but they're well above a sub's frequency. You just don't want it too narrow to create air flow noise, so the narrowest possible with the push/pull alignment leaving reasonable clearance if the pole is vented should be fine.
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Old 25th May 2004, 05:09 AM   #8
MtnBob is offline MtnBob  United States
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How about if I made all three chambers the same size? Then I could try facing the drivers either way.

#2 is a Volfenhag - anyone ever heard of/used one? It's an auto sub, but try to find a "real" home audio sub with good OB specs for a reasonable price - $50-60 each
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Old 25th May 2004, 06:52 AM   #9
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Equal chambers will result in a larger than necessary enclosure. With cheap drivers like those, the distortion reduction of push/pull alignement will be even more important.
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Old 25th May 2004, 10:31 PM   #10
tom1356 is offline tom1356  United States
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Quote:
Originally posted by MtnBob
Thanks, Tom. I've got that gif saved somewhere. WHen I said middle section, I was thinking of a design I saw where the drivers were facing each other. Wonder where I saved that?
You may want to rethink the drivers facing each other. Here is
a response from Roscoe Primrose to the question of why is it better to have them oppose each other rather than face each other....

Second order distortion cancellation. Remember, in a W baffle the drivers are moving in opposite directions, so one cone is moving towards it's magnet structure wile the other is moving away...

Peace
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