push-pull design

[nukaidee]

hey guys, I just seem to be brimming with wacked out ideas recently. Here is my newest. since I my goal is decent sound in a small package, and I find its almost impossible to get any low end with a single driver, yet I do not want to double up my volume.. someone commented I can half my volume if I do a push-pull design.

therefore..

What if I took a box, and mounted 2 speakers on either side as L and R. that would half my volume needed for those 2 drivers and keep my sub idea on the bottom facing down.

|----------|
|............|
<-D.............D ->
|............|
|----------|
---- W ---

D's are drivers with the arrows indicated direction, W is the woofer pointing down

Appreciate your feedback.

Thanks

[tinitus]

Originally posted by nukaidee

someone commented I can half my volume if I do a push-pull design.

Only "isobaric" pushpull will half the volume

Its also called "clamshell" mounting, but doesnt need to be

[nukaidee]

umm.. then how does the sound come out? its just like placing the drivers facing each other, wont that muffle everything? from what I am reading here, there are many ways to mount it. http://www.audiogearreviews.com/tech...n/isobaric.asp

and I'm guessing that isobaric only works for subwoofers and not particularly good for the high ends.. maybe I will mount my subs like this and use a stand alone tweeter.. usually tweeters don't need a big volume right? maybe I can just place one on top like something sticking out?

[Moondog55]

There are commercial speakers with drivers set up PUSH <-> PUSH as you propose although I cannot remember which ones they are and haven't heard them.

While technically they would need double. the volume actually needed seems to be less, at least for woofers/subwoofers, and I do not know why.

boxes built like this would I believe have a sound and imaging qualities similar to Open Baffles.
it is one of those experiments I have been meaning to do for quite a few years but haven't yet

Such boxes need double the amount of drivers.

Regards
Ted

[planet10]

Originally posted by Moondog55
There are commercial speakers with drivers set up PUSH <-> PUSH as you propose although I cannot remember which ones they are and haven't heard them.

NAIM used to do one, Mirages subwoofers do, i know there are more, but they escape me

dave

[56oval]

Goldmund used isobaric bass modules .

Cheers

[nukaidee]

alright.. after a long long time and alot of websites later.. I'm back with more wierd ideas.. just wanted to double check.. for a push pull style.. the "pushing" driver should be in a sealed enclosure with the minimal air space while the outer driver should be in a proper volume box correct? is there such thing as a ported push pull design?

[Willitwork]

Originally posted by Moondog55
There are commercial speakers with drivers set up PUSH <-> PUSH as you propose although I cannot remember which ones they are and haven't heard them.

In a similar vein some commercial speakers (Totem) use two midbass drivers placed in series one behind the other to produce more bass from a small volume, the second driver is mounted on a hidden baffle inside the cabinet on axis with the forward one which is visible on the external baffle under the tweeter. Externally the speakers look like normal bookshelfers except for their weight. I don't know if the cutoff frequency is the same for both drivers but obviously only the rear wave of the internal driver would be useful. Since they are in phase I guess it's a push-push situation. Drivers used are Hi-Vi D series, originally Dynaudios were used.

[Brett]

Originally posted by Willitwork


In a similar vein some commercial speakers (Totem) use two midbass drivers placed in series one behind the other to produce more bass from a small volume, the second driver is mounted on a hidden baffle inside the cabinet on axis with the forward one which is visible on the external baffle under the tweeter. Externally the speakers look like normal bookshelfers except for their weight. I don't know if the cutoff frequency is the same for both drivers but obviously only the rear wave of the internal driver would be useful. Since they are in phase I guess it's a push-push situation. Drivers used are Hi-Vi D series, originally Dynaudios were used.

That sounds like isobaric.

[fwater]

Originally posted by nukaidee
alright.. after a long long time and alot of websites later.. I'm back with more wierd ideas.. just wanted to double check.. for a push pull style.. the "pushing" driver should be in a sealed enclosure with the minimal air space while the outer driver should be in a proper volume box correct? is there such thing as a ported push pull design?

Push-pull, push-push, heave-ho... the titles and meanings are mostly interchangable and get muddled by noobs (absolutely no offense implied) thinking that it might be important to use those terms.

Isobaric is any time two drivers are working in tandem with a small fixed airspace between them. I think that most times when the word is used alone, it will invoke the image of a woofer in a sealed or ported enclosure with another woofer very close to and directly in front of it, coupled to each other with a small chamber. Clamshell isobaric is, of course, just that, a woofer in a box with another mounted face-to-face, or sometimes referred to as push-pull, though both are moving in the same direction at the same time. The "outside" driver is wired backwords from normal. The advantage is less complication from not needing to assemble a coupling chamber and also something to do with the distortion inherent in any driver being cancelled to some degree. I've done this many times in my car audio days. The advantage to both, of course, is the smaller enclosure requirements. It is not exactly half, but close enough.

Earlier in this thread there was what looked to be a bipole, or two drivers, one facing forward to the listenning space, the other backward. What happens to enclosure size requirements depends on what kind of load one is going to end up with through driver wiring- parallel or series. Two woofers in parallel will need double the volume for one woofer to maintain the same bass extension. Two woofers in series will require around the same volume as one woofer for the same bass extension, but the rolloff will be a little different (not always audible, in practice). These two examples are traditionally wired normally. Wiring the rear one backwards results in a loss of bass, to what degree isn't always easy to predict, but it is usually profound.

Maybe you could post you size requirements and output goals. It would certainly make steering you toward a solution a little easier.