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Old 19th July 2007, 04:37 AM   #1
Klook is offline Klook  Brazil
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Default Building push-pull subwoofers

Hi people,
I tried to search on the internet about building push-pull subwoofers but it seems that there is a lack of info about it.

Does anybody has a link with tutorials/theory/calculations about building a push-pull sub?

best regards
Klook
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Old 19th July 2007, 12:12 PM   #2
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Default hello

I am not sure what u mean by push pull sub, heard of push pull amp thou,
i think what u might be looking for is called ISO BARIK loading of 2 woofers, face to face, try searchin ISO BARIK loaded
or see this
http://en.wikipedia.org/wiki/Isobaric_speakers
let us know if ur looking for this

best of luck with your search,bbye
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Old 19th July 2007, 01:33 PM   #3
BHTX is offline BHTX  United States
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I'm interested in doing this as well, with 4 high excursion 15's in 2 separate sealed enclosures. I've decided not to do isobaric loading, as I don't want to lose all the maximum output and efficiency. I've heard that a push-pull arrangement can reduce certain types of distortion etc, but I've never tried it before. And no, it doesn't have to be an isobaric enclosure to be push-pull (take M&K, EAW, and many others, for example).
Isn't there push-push as well?
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Old 19th July 2007, 01:38 PM   #4
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There's loads of info both on here and the wider web.

It's just a method of cancelling odd-order harmonics. Isobaric is a different thing, although you can have isobaric push-pull which effectively halves Vas.

You just put one cone facing out like normal and the other one facing in, then drive them in opposite phase.
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Old 19th July 2007, 02:07 PM   #5
BHTX is offline BHTX  United States
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Yeah, I was interested in push-pull isobaric loading when I was wanting to use these drivers previously mentioned in massive vented enclosures. But, I soon came to the conclusion that it just wasn't an option, mainly due to space constraints. On top of that, I've changed plans (again!) and a sealed alignment with LT or EQ would be better for use strictly under 40Hz or so, I think. So, now a push-pull sealed enclosure seems more logical.

Thinking about it.. one driver moves in, while the other moves out. Theoretically, odd order harmonics from the drivers and their motors should be cancelled out, or at least a large portion of it. Am I looking at this correctly? Sounds right to me, anyway.

My main question is.. are there ANY disadvantages to push-pull versus the conventional methods? If not, why don't we see it more often in commercial designs? I've seen many, but it seems that most designs using 2 or more subwoofers don't utilize it, which doesn't make sense to me. The only thing that comes to mind is that a tad bit more complicated enclosure design might come into play if hiding the back of the driver is desired...but I would think that would be very easy to do the majority of the time.
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Old 19th July 2007, 02:09 PM   #6
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Decent drivers don't have such bad non-linearity problems to make the benefits that big.

But the main reason is cosmetic.
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Old 19th July 2007, 02:21 PM   #7
BHTX is offline BHTX  United States
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So, with 4 Ascendant Avalanche 15's (XBL^2 motors, 27mm xmax, etc), you don't think the difference would be very noticable? I'm very curious to know what it'd sound like this way. Because if I did them push-pull, 2 per sealed enclosure, I'd build it to where the bottom driver is mounted backwards...with the bottom section of the enclosure several inches shallower than the top part, but with the MDF extending from the bottom portion to meet flush with the top part, and kind of hide the back of the bottom driver some how...know what I mean? I'd probably try to make it where at first glance, it only looks like a single 15 in a larger sealed enclosure. But if it's not worth it, I won't bother building it like that. What do you think?

Also, one thing I've never been absolutely clear on..
In a push-pull, the two drivers have to be in the same enclosure, right?
Because if I ended up not doing push-pull, I'd put them in 4 separate enclosures.
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Old 19th July 2007, 04:14 PM   #8
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yes non linearity is not a big issue, richie is rite if u have a decent enclosure and driver u dont need any non linearity complensation
iso-barik, reduces the enclosure volume but is less efficient

iso barik and push pull both coupling removes odd harmonics
bridge mode push pull amplifer, that will also cansel out the even harmonics

BTW , i refered to this link
http://www.eaw.com/technology/nonpro.../pushpull.html

diffrence-
isobarik is less efficient, but pushpull is more efficient
isbarik reduces the enclosure volume, but pushpulldoes not reduce any volume
similarity-
is both reduce distortion due to non-linearity

in isobarik, example u stick 2 subs front to front. push pull is like in a single enclosure u fix 2 subs 1 facing inwards other 1 facing outwards(they share common enclosure twice the enclosure size for 1 sub)
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Old 19th July 2007, 04:15 PM   #9
Klook is offline Klook  Brazil
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Check this:
http://danmarx.org/audioinnovation/theories.html
there is an explanation about what push-pull configuration is.

But I can't find in web detailed explanation about how to design the cabinet according to the driver parameters.

regards
Klook
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Old 19th July 2007, 04:47 PM   #10
BHTX is offline BHTX  United States
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Quote:
Originally posted by Klook
But I can't find in web detailed explanation about how to design the cabinet according to the driver parameters.
What do you mean? It'd be the same as designing a subwoofer of any other enclosure type.. If you're doing a sealed push-pull with two identical drivers, it's the same as a sealed enclosure for one of those drivers x2. Same thing goes for vented, or bandpass, or whatever. Perhaps I don't understand what information you're trying to obtain? If you're just wanting to figure out how to design subwoofer enclosures around different types of drivers, in regards to theile-small parameters, that's another whole subject. Otherwise, those rules don't change for designing a push-pull cabinet.
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