push-pull-push-push

[Chris8sirhC]

Recently i have been toying around with doing a push-pull-push-push TL sub design. On this forum this topography was brought up. The only downside to this design is you have the speaker baskets sticking out of the enclosure. I was just wondering if somthing like this would still work. I'm thinking that a possible reason it may not work is that there is a much greater air volume between the two drivers as opposed to the original design where they are facing eachother. I'm thinking the two paris of drivers would be in a sonotube that fits snugly around the circumfrence of the driver. Is this just a dumb idea, or is there a chance something like this would work?

[sreten]

It will work just as well as the other arrangement.

Though why you'd use isobaric in a t/l has me mystified.

A push pull pair would seem to be the most sensible.

sreten.

[Chris8sirhC]

Well i have 16 of these 10'' drivers sitting around my house, i got them for about $5 each. I'm really looking for some way to use them up. I read that having this configuration helps cancels out any non-linearitis in the speaker, so I mighnt as well use 4 even if there is only a marginal improvement in sound.

[sreten]

A single pair in push pull will cancel non linearities.

Have you the specs of the drivers ? some are much
more suited to isobaric pairing than others.

You can use 2 isobaric pairs in the same box as
a single driver, but a t/l would need 2 x the area.

sreten.

[kneadle]

Originally posted by Chris8sirhC
so I mighnt as well use 4 even if there is only a marginal improvement in sound.

Build it. I want to know how it turns out because I have a dozen (!) drivers lying around doing nothing. I'd like to try something using two drivers in tandem somehow. So, if yours is successful, then mine will be too. If yours fails, then I'll learn at least one thing NOT to do.

Dave

[Svante]

Originally posted by sreten
A single pair in push pull will cancel non linearities.

Have you the specs of the drivers ? some are much
more suited to isobaric pairing than others.

You can use 2 isobaric pairs in the same box as
a single driver, but a t/l would need 2 x the area.

sreten.

I think the arrangement has a wonderful symmetry and would cancel both even harmonics and much of the cabinet vibrations. But as you say, that would happen also with a non-isobarik, 2 driver, push-pull arrangement. Shouldn't it be called push-pull-pull-push, though?

I am unfamiliar with TL dimensioning though, I would have thought that it would have worked just as with the box. How is the cross-sectional area usually selected in a TL?

[Chris8sirhC]

here is a link to the specs I think i read that the cross sectional area of the transmission line should be between 100% and 125% of the drivers surface area.

[sreten]

*Power Handling: 30 watts RMS/60 watts max *VCdia: 1" *Le: 1.50 mH *Znom: 8 ohms *Re: 7.20 ohms *Frequency range: 44-2,000 Hz *Fs: 44 Hz *SPL: 92 dB 2.83V/1m *Vas: 3.57 cu. ft. *Qms: 5.80 *Qes: .90 *Qts: .78 *Xmax: 3 mm *Driver Dimensions: A: 10-1/4", B: 9-3/8", C: 4".


Well thats a whopping Vas for a 10" driver with a 0.8 Qts.

And Xmax is not impressive.

Sensistivity is pretty good.

What do you expect for $5 dollars ?

How to use them effectively is a major issue.

Reflex is out of the question, except at huge cabinet volumes.
Sealed box possibly, in isobaric configuration, but tight bass is
not on the agenda unless you use a Linkwitz transform.

I'd say twin 4x10 open baffles for low power valve equipment,
assymetrically crossed over to an open baffle full ranger around
92dB/W, such that the bass has already lost 6dB.

For all sixteen units possibly twin opposed paired 4 x 10 arrays,
similar to the SL6 dipole subwoofer, but I readily admit the theory
of such units has me somewhat perplexed.

(Push pull can be easily used in dipoles, isobaric has no advantage)

sreten.

[sreten]

Sealed box is possible but you need an amplifier with
low crossover frequencies to roll the sub off early.

Volumes are for one driver or 2 x isobaric pairs.

Optimum volume = ~ Vas.

sreten.

[Chris8sirhC]

I always figured that OB subs would have to be huge, im not sure if i have that much space for speakers to take up. Maby since their qts is near .76 i could just do an IB experiment with 4 or so of the drivers along with the TL.