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Old 15th June 2006, 12:31 PM   #11
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thanks guys,i think i will stick to a normal series/ parrallel, 4 front facing woofers in their own sealed compartment.
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Old 15th June 2006, 07:03 PM   #12
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Quote:
Originally posted by chainenoble
thanks guys,i think i will stick to a normal series/ parrallel, 4 front facing woofers in their own sealed compartment.
You are missing a big opportunity by not mounting them push-push.

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Old 18th June 2006, 12:34 PM   #13
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Quote:
Originally posted by planet10


You are missing a big opportunity by not mounting them push-push.

dave
And an even bigger one IMHO by not going push pull. Back to back push push does what you can achieve with a very solid box. What push pull does can't be done any other way.

But why choose? You have 4 drivers - do both!

If you have 4 drivers, why not make each box push push, then wire one box with polarity reversed. This is the best of both worlds. Back to back push push as planet10 advocates is effective from a box vibration point of view. Done as I suggested you also get push pull.

Push pull gives lower distortion (2nd order harmonic). The drivers combined in this way are more linear. Subjectively they sound tighter. I tried this recently and the result surprised me - much less subtle than I expected.

Interesting - wire two subs with incorrect polarity on one of them and the bass becomes very weak. Do this with a H frame dipole and the reduction in bass goes to the next level - it's quite strange as the box vibrates, the drivers move yet the sound is as if the subs are turned off and there is NO BASS below 200 Hz!

You can only use push pull where the drivers don't deal with midrange.

I'm surprised I haven't seen that driver before. I didn't know Vifa made aluminium drivers.
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Old 18th June 2006, 01:13 PM   #14
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i will try push pull,but later.i have already built the boxes with 2 per box in individual chambers sealed.also i need to learn more about push-pull.like my original idea was a standard push pull.then there's the compound push- pulls.the front-front,the back - front and the back-back.i'm not sure which is best.also i run these up to 100hz.not sure how this would effect the above designs.i could easily change my box for a standard push-pull,but is the compound much better?
as for this woofer by vifa,i think it was made as a custom woofer for totem acoustics and maybe madisound as the left over stock.it's a real little gem.
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Old 18th June 2006, 02:32 PM   #15
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Changing is simple, you don't need to learn anything. Take one driver in each box and mount it so that the magnet faces out. Reverse the polarity of the wiring. Try it and see what you think. Just watch that you don't lose the seal of your box.

What would also be interesting is these drivers push pull in a TL.

I'm not sure exactly what you are rerferring to with "compound." If you are referring to isobarik, I see no real use for that here.

For home theatre I'd consider vented.

Quote:
If the cones move in the same direction, you will need a box of twice the volume, you will get a sensitivity increase of up to 6dB, the impedance will halve, and you will get a higher maximum SPL.
Not quite. Sensitivity will increase 3db due to the doubling of SD. Power handling will increase by a factor of 2x yielding 3db extra if the additional power is available. Two drivers driven with 100w each will have up to 6db more SPL than a single driver driven with 100w. This depends on how they couple as well. In stereo configuration considerably less will be gained.
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Old 18th June 2006, 02:52 PM   #16
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actually!!,i have not finished the second box yet.the first box has a divider seperating the to chambers.the second box i will leave open and build as a push-pull.leave the first as-is and do a side by side comparison.if i like the push-pull more i can cut out the divider in the first box..this will be fun
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Old 28th June 2006, 02:13 AM   #17
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so here's my test set-up.i tried regular 2 front facing and as you see the push-pull.the push-pull does sound better-tighter bass.but not by much.enough that i will go with push pull.to bad in a way as 2 of these woofers facing forward looks fantastic-such a good looking woofer!!

i have them crossed at 100hz as i really like the impact of the upper bass from these woofers.tight and fast.am i safe putting them away from the mains.i don't like the sound anywhere close to the wall or corner and since i have 4 and the power,i don't need wall or corner reinforcement
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Old 28th June 2006, 05:35 AM   #18
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My box looks like that now, except that mine are 12" drivers and very heavy. The bottom driver has a magnet so heavy it topples even a 0.9m box easily. I'm currently running mine in a U frame.

It's nice to see the guts of the driver - I like to see that, but I get what you are saying - those drivers do look great at the front.

Tight is the word that comes to my mind as well - not huge, but noticeable.

They don't need to be right up close. Linkwitz discusses this for his woofers in the Phoenix, which has them separate and crossed at 120 Hz IIRC. The path difference should not be greater than 1/4 wavelength of the xo IIRC. For 100 Hz that would be 0.86m. As a result , you can move it to the side a fair amount without increasing the path difference to the point where it is a problem.
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