Push-Push or Push-Pull

[Bigun]

Now that it's no longer a question of using two drivers I should probably start a new thread with this.

Based on advice so far I have ended up with a simple box, birch play and braced internally. Two drivers in push-push and an integrated amp to avoid microphonics (although I'm not quite convinced on this front for solid state). There's no semblance of a golden ratio in this design of course.

But it seems a bit boring not to build a push-pull instead, given that it would be a bit more challenging and less a look-alike for an off-the-shelf sub. I recognize that the benefits should be more noticeable with less linear drivers and with larger excursions - but I may not be able to appreciate the difference. You see, I've never had a sub and I will have nothing to compare it with if I build it since I don't really want to get into doing too many experiments. I've also heard that there is the risk of unwanted noises from the vented magnet. So common sense says build a push-push and yet my hands want to build a push-pull.

It's a question that no doubt has been asked before, but I thought perhaps not with these specific drivers ???

Here's the push-push version

 

[Bigun]

And the Push-Pull version.

A little loss of box volume, easy to compensate for with an extra cm all round.

 

[JLH]

Push-pull 100%

 

[GM]

So common sense says build a push-push and yet my hands want to build a push-pull.

Well, at least you have some common sense which is more than can be said of many folks, but DIY audio is mostly about satisfying oneself, so why are we having this conversation?

GM

 

[MarkR]

Build both 😀
Two enclosures shouldn't take long or cost allot. Try them out see which one yours ears like better and if they can't tell them apart pick with your eyes.😉

 

[tinitus]

Both ways ought to be possible in the same box 😉

 

[Bigun]

Both ways ought to be possible in the same box 😉

It could be done, although it turns out easier if I wanted to try them both inverted rather than neither of them inverted.

I had a question about speaker grill/covers. For subs, the excursions can be large, so does this imply that the grill has to be spaced off from the cone surround by essentially xmax - which can be quite large ?

 

[tinitus]

For subs, the excursions can be large, so does this imply that the grill has to be spaced off from the cone surround by essentially xmax - which can be quite large ?

I dont think so

The surround doesnt move outwards to the same degree as the cone Xmax
But you should be able to carefully move out the cone, and see how much change it makes on the surround

 

[Cal Weldon]

The surround doesnt move outwards to the same degree as the cone Xmax
But you should be able to carefully move out the cone, and see how much change it makes on the surround

The surround will move 1/2 what the one way Xmax is (not P-P)

 

[Bigun]

My shipment arrived from Creative Sound Solutions today. First time I've seen or held a sub-woofer driver. They are quite different from the little Fostex full-range drivers. But I can say that I am very impressed with the out-of-box quality of the TRIO8s. They are nicely finished and look to me to be well thought out and made with good quality materials. Decision made. The Push-Pull will allow me to view the front and back of this lovely driver for years to come !

 

[chris661]

I know this is a bit late, but look at http://www.superfi.co.uk/index.cfm/page/moreinfo.cfm/Product_ID/2509

Uses push-push to make the box stay perfectly still.

You can get a glass full to the top of water, sit in on the sub and play music as loud as you want - none spills.

Also goes staggaringly low.

There are certain equalisers that would sort out the lumps in the frequency response.

 

[901Fixer]

What, pray tell, do they mean by "Built around the principles that keep deep-sea diving craft in one piece" ? Its made out of steel? Its spherical?

 

[AndrewT]

I know this is a bit late, but look at http://www.superfi.co.uk/index.cfm/page/moreinfo.cfm/Product_ID/2509

Uses push-push to make the box stay perfectly still.

It's not the push/pull or push/push that helps stop it vibrating.
It's the two drivers on opposing faces that helps cancel out the reaction of the accelerating cones.

 

[AndrewT]

The surround will move 1/2 what the one way Xmax is (not P-P)

Hi,
one edge of the surround should move the same distance that the frame moves.
The other edge should move the same distance that the cone moves.

The surround, in between those two edges, will be distorted into a variety of curves/shapes as the cone passes through various amplitudes and particularly frequencies.

 

[tinitus]

The surround will move 1/2 what the one way Xmax is (not P-P)

Yes ofcourse

BUT, imagine when the cone moves out, then the inner side of the surround that moves out actually lessens
The surround rolls and streches with this movement
This means that with greater cone movement there will be less surround pushed outwards
Untill the exstreme where the cone has totally streched the surround completely

In short, this means that when the cone moves out, there will be less sourround "in front" of the cone
This means that at 10mm Xmax one way, the measured difference on top of the surround will be less than the 10mm

 

[planet10]

It's not the push/pull or push/push that helps stop it vibrating.
It's the two drivers on opposing faces that helps cancel out the reaction of the accelerating cones.

My definition of push-push is that there are two tightly coupled drivers on opposing faces that actively cancel out (most of) the reaction of the accelerating cones.

A push-pull driver arrangement can also be push-push, bt it is haeder to get good coupling.

dave

 

[planet10]

Uses push-push to make the box stay perfectly still.

Looks like B&W missed the boat on this ... the cutaway shows the magnets tantalizingly close with no direct connection... so the forces need to travel the convoluted routre thru the cabinet.

dave

 

[Bigun]

Would it be fair to say, that a box designed as it should be, strong enough to be stiff with low energy storage for one large driver would automatically be strong enough to handle the internal forces from having two medium sized drivers whose magnets were not directly coupled - 'killing two birds with one stone' ?

 

[AndrewT]

Would it be fair to say, that a box designed as it should be, strong enough to be stiff.... enough to handle the internal forces from having two medium sized drivers

it should be, but some like to save money/weight.

 

[planet10]

Would it be fair to say, that a box designed as it should be, strong enough to be stiff with low energy storage for one large driver would automatically be strong enough to handle the internal forces from having two medium sized drivers whose magnets were not directly coupled - 'killing two birds with one stone' ?

I don't see why you would bother not to take advantage of tight driver coupling. In your propoed push-pull box, good coupling between the magnet in the box and the baffle on the other. Icing on the cake would be common ready rod as bolts for both drivers.

Note: the drivers pictured were designed to be bolted thru the pole-piece to the cabinet and this is repurposed for push-push.

dave