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Old 13th May 2003, 02:26 PM   #1
Schaef is offline Schaef  United States
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Default Questions on push-push subs...

I'm contemplating re-building a pair of subwoofers I made several years ago. They are currently set up similar to the sono-subs in a passive stereo pair. Since I now have a digital HT, I have been thinking of going to a powered single-sub configuration.

So, with that in mind, that means I have a pair of 10" peerless subs to use. I have been toying with a half-a-dozen different ideas/configurations. Recently I've been toying with the idea of using the two in one box to help with the bottom end in a sealed enclosure, and thought maybe the push-push idea would be interesting.

Here's some specs/limits:

The woofers are 10" Peerless 260SWR (831727)
The maximum box size is in the 3 to 4 cubic foot range.
The box will be place in a corner in the room.
Transmission line, while a neat idea, is more than likely out. (I don't think it'll fit in the space requirements.)
The amp hasn't been purchased yet, but am currently looking at the ApexJr plate amp.

So, any thoughts on doing a push-push with these limits?
In push-push, do the speakers have to be back to back? (What about 90 degrees to each other)
Will having one speaker fire into the wall kill the push-push idea? (Up/down is out, as it will be used as a quasi end table as well)

Any other suggestions for other arrangements that would be fun?

Thanks for the help and info!
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Old 14th May 2003, 07:13 PM   #2
kneadle is offline kneadle  United States
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bump.

I'm interested in this project, even though I have no input. Here's hoping someone comes along who does have input.

Dave
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Old 14th May 2003, 11:03 PM   #3
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I heartily recommend push-push. Chris & i are working on V3. Pic is V1 using 2 x Philips 12". The box is about 2.8 ft^3, and in the cases of V1 & V2 are both aperiodic (the drivers would really like to see bigger boxes). The top 2 images show the brace used to ridgidly connect the 2 magnets together -- the blue foam is closed cel and quite thin and provides just enuff to tightly couple the magnet to the brace. It is important that the drivers are on oppossite sides & tied together mechanically.

Both V1 & V2 (customer supplied Foster 12s) turned out really well. Both use drivers that are more intended for midbass use than sub use. They go low cleanly and integrate very well with the sats (in both cases a quartet of BD-Pipes with RS 40-1197s). The push-push loading means very little mechanical energy transfer to the box.

dave
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Old 14th May 2003, 11:04 PM   #4
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A snapshot of the plans. If anyone wants a copy that are large enuff to read the dimensions and such, just email me.

Note: pics are of V1, plans of V2.

dave
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Old 14th May 2003, 11:41 PM   #5
7V is offline 7V  United Kingdom
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I have two alternative subs for my new Nonsuch range. The Little Awesome and the Bigger Awesome.

The Little Awesome is like an oval barrel with the driver (Bandor 150) firing out of the bottom.

The Bigger Awesome is a Push-Push, comprising one Little Awesome mounted upside-down so that the driver fires upward and the other one normal-way-up on top of it, separated by 2" - 3". The sound comes out of the middle, between the two drivers.

Clear as mud? Sorry I haven't got any drawings to show you. I just figured that the vibration cancellation would be even more effective if I could get the two drivers close together.

Anyway, if you can figure out what I mean, I put this forward as another alternative because the drivers are in the centre so you could still put coffee cups on top.

If you don't want to go for this vertical approach, I still wouldn't recommend the 90 degree thing as you would lose the vibration cancellation benefit.

As for whether you can fire into the wall (presumably there will be a gap between speaker and wall), I believe that this depends on the highest frequency the speaker has to produce. Down in the deep bass I don't think the speakers will care (some disagree) but if they go above, say, 150Hz - 200Hz you may have a problem.

For the particular driver you're using and the volume required, Push-push would require double the box size of a single driver.

Hope this is helpful.
Steve
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Old 14th May 2003, 11:59 PM   #6
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Quote:
Originally posted by 7V
Clear as mud? Sorry I haven't got any drawings to show you. I just figured that the vibration cancellation would be even more effective if I could get the two drivers close together.
Like the attached image? A very interesting design thou from a cosmetic point-of view.

Face-to-face is harder to get good coupling. The only way i can think of would be to use somesort of driver attachment that couples the 2 drivers together, but i can see complications with assembly.

Best is magnet direct to other magnet & the frame rims also tied together. If you can bolt the two drivers together even better.

Click the image to open in full size.

If this had the magnets touching it would exemplify what i'm suggesting.

dave
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Old 15th May 2003, 12:27 AM   #7
7V is offline 7V  United Kingdom
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Quote:
Originally posted by planet10

Like the attached image? A very interesting design thou from a cosmetic point-of view.
Yup, that's the one Dave.

Quote:
Face-to-face is harder to get good coupling. The only way i can think of would be to use somesort of driver attachment that couples the 2 drivers together, but i can see complications with assembly.
Yes, I think you're right. So far all I've come up with is connecting the baffles together. Not ideal. I haven't tested yet so I'll see in the next few days. The closeness of the two baffles should provide some cancellation. we'll see.

Steve
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Old 15th May 2003, 01:06 AM   #8
kneadle is offline kneadle  United States
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Quote:
Originally posted by planet10


Like the attached image? A very interesting design thou from a cosmetic point-of view.


dave
I've seen this before, somewhere. Now, is the basket a contraption that is housing the drivers for some reason? Am I reading that correctly?

What I mean is: are those baskets the things actually absorbing the mechanical energy, or are the drivers still driving against each other?

Dave
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Old 15th May 2003, 01:57 AM   #9
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Quote:
Originally posted by kneadle
I've seen this before, somewhere. Now, is the basket a contraption that is housing the drivers for some reason? Am I reading that correctly?

What I mean is: are those baskets the things actually absorbing the mechanical energy, or are the drivers still driving against each other?
The ultimate push-push is based on the PEARL PR2 woofer.

Click the image to open in full size.

The magnet assembly sits inside the basket and it is designed to be bolted thru the polepiece. This is a very rare driver. With more accessible drivers some compromises or other tricks would need to be enabled. But if you are getting an OEM batch of drivers it is worth thinking about using these features.

dave
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Old 15th May 2003, 03:55 AM   #10
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A lot of woofers frames' extend out enough that I think a few holes could be drilled close to the magnet and sleeve-nuts used to bolt the two magnets solidly together.

So does cabinet tuning differ for a push-push, or do you just design as if it was a regular dual woofer sub?
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