push-pull design

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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
 
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nukaidee said:

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
 

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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/theory/enclosure_design/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?
 
diyAudio Member
Joined 2007
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
 
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?
 
Moondog55 said:
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.
 
Willitwork said:


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.
 
nukaidee said:
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.
 
well.. essentially I'm trying for a multidriver.. smaller than standard bookshelf speakers with decent everything. sounds impossible.. i know..
my current plan..
exterior - single box style, interior is going to be 2 different spaces, so hidden baffle.
bass - 1 or 2 (isobaric) 3 inch subs from tangband
top section - full range drivers from tang band (3")

its just a thought for now. isn't heavier better? =P but I want to keep it small, and the sub will be downward firing, speakers will be on 1 inch standoffs.

oh. btw. anyone know where else to get tb speakers in canada? solen doesn't have any bamboo series.
 
Brett said:
Unibox shows no difference in Vbox for two drivers in series or parallel to get the same Qt and F3.


Jeff Bagby's Box Modeller 3.20 shows differently. In some (maybe many) cases, the f3 will appear similar in numbers, but the Qts is different for either wiring, even if you're using the same volume. The curve also appears different, the rolloff often having a hump or sometimes a more "rounded" bottom. The volume requirement for similar output isn't exactly 50%, more like 60-70. I can't recall exactly why this is, maybe someone a little more well-read will jump in.
 
nukaidee said:
well.. essentially I'm trying for a multidriver.. smaller than standard bookshelf speakers with decent everything. sounds impossible.. i know..
my current plan..
exterior - single box style, interior is going to be 2 different spaces, so hidden baffle.
bass - 1 or 2 (isobaric) 3 inch subs from tangband
top section - full range drivers from tang band (3")


One single (mono) box containing all the drivers or two (stereo) boxes each housing a woofer and a fullranger?

I am continually impressed by the amount of bass that can be extracted from any number of 4" drivers, but that 3" woofer might not get you any satisfying output in any other situation than desktop comuter speakers. A quality 4" do the job that you're trying to accomplish. At any rate, I can't think of any situation where the tiny volume requirements for a 3" driver would need to be reduced even further, unless it's going into a matchbox car ;)
 
ok ok i can do a footprint of 4" =P
lets see if i can explain it better..
this is going to be a stereo setup, 2 boxes in total. each "box" will house 2 drivers, 1 full range and 1 subwoofer. each will be separated by an invisible sealed baffle? i think that is what you call it.. i don't mind porting the sub, but i think i calculated something stupid like 0.5 inches in diameter and 2 inches length.. where am i going to find pipe like that.... if you say the 4" are good, can you recommend one? i'm trying to source them in canada, and hopefully around 25-30 each. the enclosures will be mdf.

thanks for your help!
 
nukaidee said:
ok ok i can do a footprint of 4" =P
lets see if i can explain it better..
this is going to be a stereo setup, 2 boxes in total. each "box" will house 2 drivers, 1 full range and 1 subwoofer. each will be separated by an invisible sealed baffle? i think that is what you call it.. i don't mind porting the sub, but i think i calculated something stupid like 0.5 inches in diameter and 2 inches length.. where am i going to find pipe like that.... if you say the 4" are good, can you recommend one? i'm trying to source them in canada, and hopefully around 25-30 each. the enclosures will be mdf.

thanks for your help!


O.K., now I get it, we're simply using just a little bit of different language. A baffle is the name given to whatever seperates the front wave from the backwave (usually the front of the cabinet), what you're referring to can simply be called a separator or divider.

A 4"x4" footprint isn't very big. If the enclosure could be 36" or more tall, then there would be something to work with. At 12" tall, you're going to net less than 1.5 liters. I can't think of any 4" driver that could live in that volume with any output below 100Hz. I also can't imagine that a 3" driver would do any better, even if the Fs is 65Hz.

By no means do I want to discourage anyone, but if it's bass you're after in this small of a package, I cannot see a way to do it, even with an isobaric setup. If you can do a seperate sub in a more remote location, then I have a list of the usual 4" suspects, but a 3" fullranger will probrably do a fine job at less cost.
 
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