The 1st is push-push, the volume for 2 drivers is twice what it is for one.
The 2nd is completely impractical for a small FR. First, you are introduceing significant ripple to the upper mid/top end and 2nd, given material thickness and driver size the extra total box size for the coupling chamber will mean no volume savings over the first.
dave
The 2nd is completely impractical for a small FR. First, you are introduceing significant ripple to the upper mid/top end and 2nd, given material thickness and driver size the extra total box size for the coupling chamber will mean no volume savings over the first.
dave
3rutu5,
This is a conclusion often reached with modern drivers, and the volume savings was the main reason for most DIY'ers going isobaric.
30 years ago, Vas values were substantially higher. And this value is proportional to the box size required to house a driver properly. It was not easy to find a 10" woofer to work properly in 1ft3, if you could find one at all. It was pretty common to need twice that for a 10", and 3-4 times that for a 12." Going to an isobaric solution was sometimes our only option to get what we wanted in the space we had available.
That changed as manufacturers began to produce woofers that traded off efficiency for intrinsically lower Vas, and a much smaller box size needed for a single woofer. Now, there are plenty of modern drivers, large and small, that are already suited to good small box performance.
With this type of modern driver, when you factor in the extra volume occupied by (a second woofer + a means to connect them + material thickness + cosmetic/mounting treatments), it can add back 70% or more of what you were saving by taking this route to start with.
As Dave already said in much more succinct fashion.
Right.....I had a feeling I was trying to do something that wasn't intended for. When I saw a video and did some reading I got the impression that I could build a speaker box that was half the size, but going back before and rewatching a video and reading Dave's response with affecting mids and highs, it sounds like people really only use it these days for subwoofers or mid/low drivers.
Sorry about being that guy and cheers for the help
Sorry about being that guy and cheers for the help
long ago I had Audio Concepts isobarik Dynaudio woofers and leaky - sealed cabinets in trade for some forgotten gear. Qtc was very low - box big - bottomed out at very low levels - IMO a waste of woofers and cubic space in that instance. I'm sure a CSS Trio 12 in a tapered pipe would trounce it.
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Hi, dave.
I'm putting together a rough sealed sub with 2 drivers and like this push-push method as the box is less than ideal.
Could you achieve push-pull action at same time by mounting the opposing driver back to front and reversing it's polarity?
physically it wouldn't be symmetrical, but the forces should still be I think.
Thanks for the quick reply.
I thought the P830668 was a pretty decent woofer but considering price it must fall into the not great category, if it can get better that will be really nice.
It will be interesting to try out both methods and see what there is to gain/lose, it's definitely something you dont see a lot.
I thought the P830668 was a pretty decent woofer but considering price it must fall into the not great category, if it can get better that will be really nice.
It will be interesting to try out both methods and see what there is to gain/lose, it's definitely something you dont see a lot.
SLS are purported to be good. And Peerless in general doesn’t ship bad stuff. No pole vent, so that is not an issue. Paper cone, i would coat with puzzlekoat/modpodge.
Personally i would just push-push them.
Without running the numbers, the highish Q and biggish Vas likely indicates a largish sealed box.
dave
HPD headphone drivers also had great bang for buck also ime, there wasn't much doubt the SLS would offer a lot for the price.
I can manage about 70L with stuffing (Qtc 0.9), a bit underkill but this way it is much easier to try it out with the materials I'm using, also if performs well it will be probably be better in long run if it's a more manageable size.
Shouldn't be too difficult to compare both, as a tiny benefit push-pull will save a small amount of volume at least.
For coupling, applying some silicone sealant and running a thin paper or plastic card with small groove cut into it (e.g)over it and letting it cure will create a makeshift gasket with uniform thickness and width around driver hole, can be messy but has worked well before.
I can manage about 70L with stuffing (Qtc 0.9), a bit underkill but this way it is much easier to try it out with the materials I'm using, also if performs well it will be probably be better in long run if it's a more manageable size.
Shouldn't be too difficult to compare both, as a tiny benefit push-pull will save a small amount of volume at least.
For coupling, applying some silicone sealant and running a thin paper or plastic card with small groove cut into it (e.g)over it and letting it cure will create a makeshift gasket with uniform thickness and width around driver hole, can be messy but has worked well before.
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As usual, you were right on the money.
I was hard pressed to hear anything resembling THD cancellation with push-pull, at such low frequencies THD is even harder to detect, if there was any to begin with at these low levels.
I thought the slight acoustic low pass with back to front driver would be useful, but in practice did not like the uneven high frequency output from each side at all, made it stick it out more in the room, as it also does visually.
Push-push wins by default.
Ultimately there is no need for this sub, the sealed a11ms bass performance is just absurd for woofer, let alone full ranger.
With large vented box tuned low the sub could make more sense, but very low bass creates more trouble than its worth. Also unlikely it would be better than the A11ms in a ported enclosure or horn.
I was hard pressed to hear anything resembling THD cancellation with push-pull, at such low frequencies THD is even harder to detect, if there was any to begin with at these low levels.
I thought the slight acoustic low pass with back to front driver would be useful, but in practice did not like the uneven high frequency output from each side at all, made it stick it out more in the room, as it also does visually.
Push-push wins by default.
Ultimately there is no need for this sub, the sealed a11ms bass performance is just absurd for woofer, let alone full ranger.
With large vented box tuned low the sub could make more sense, but very low bass creates more trouble than its worth. Also unlikely it would be better than the A11ms in a ported enclosure or horn.
A friend was interested in buying the sub so we were playing it pretty loud to demo.
the box is made from only 20mm pine but with some 2x4 braces (wall to wall, in the centre of walls) inside to make up for weak walls, you could really hear the differences the braces made from knock, it may not be a bad box at all.
When played loud the advantage of push-push really started to show. The bass remained tight and dynamic, if anything it improved. I have never heard very high SPL bass of such high quality, quite spectacular.
the box is made from only 20mm pine but with some 2x4 braces (wall to wall, in the centre of walls) inside to make up for weak walls, you could really hear the differences the braces made from knock, it may not be a bad box at all.
When played loud the advantage of push-push really started to show. The bass remained tight and dynamic, if anything it improved. I have never heard very high SPL bass of such high quality, quite spectacular.