8 subs and 2 tubes

[Dr1v3n]

8x SB23MFCL45-4.
2x (10" dia x 4'tall) PVC pipe

How to arrange the drivers?

1 driver on each end for push/pull?
Clamshell arrangement in middle of tube?
Clamshell arrangement on both ends of tube?

 

[globalplayer]

I would cut the tubes in half and make a ported isobaric arrangement.
Cone facing cone as close as possible. Magnet at the outer end of the tube.

 

[Dr1v3n]

I would cut the tubes in half and make a ported isobaric arrangement.
Cone facing cone as close as possible. Magnet at the outer end of the tube.

How about instead of ported, have 10" passive radiators on both ends and the 2 cone isobaric arrangement you suggested somewhere in the middle?

 

[globalplayer]

PRs will be somewhat heavy when intended to go low and therefore will sound slowish.
I doubt it will work in the middle.
It might probably work at 1/4 or less.
But I am not sure.

 

[scottjoplin]

It's a shame the tubes aren't longer to make a couple of push-push transmission lines

 

[Dr1v3n]

It's a shame the tubes aren't longer to make a couple of push-push transmission lines

I actually wanted to match the array tower height @7' tall just for looks. But there's extra freight charge for length, of that style PVC pipe, over 4'.

Isobaric definately in the plans, just need to experiment with different setups. I'm going by ear/feeling only on this sub project. A few pics soon.

 

[globalplayer]

I like those speakers.
Very good for the money.
Need to build something where they can shine.

 

[Sonce]

How to arrange the drivers?

Cut the tubes in half, put one driver on one opening, on the other opening put Passive Radiator. Internal volume is adequate for that configuration, isobaric is wrong (too much internal volume). Buy additional 2 tubes (4', than cut in half) for the other 4 drivers.

 

[Sonce]

PRs will be somewhat heavy when intended to go low and therefore will sound slowish.

That is common misconception. They will be heavy, but definitely will not sound slow.

 

[globalplayer]

I had some speakers with passive radiators although not high end. They sounded somewhat sluggish.
But I read just before if done right they can sound very good.
So...
I will take that back and on the other thread also, although I don`t remember where.

 

[Sonce]

I had some speakers with passive radiators although not high end. They sounded somewhat sluggish.

The problem is in the woofer (high Qts) and maybe not optimal volume/tuning.

 

[planet10]

I have justthe same collection of bits. I have already cut the 12” PVC to the appropriate length for a sealed enclosure, cut baffles and get sufficient ready-rod to bolt 4 12s into each pipe in this push-pull-push-push configuration.

dave

 

[globalplayer]

Interesting.
Looks like it will eat a lot of power though.

 

[planet10]

No more than any other isobarik. Depends on how efficient the drivers are.

The ‘box’ is the volume of that used for a single driver, so a big savings there, a good thing because i only had so much pipe, and with 20 or so of the woofers i need to figure a way to use them up.

dave

 

[Dr1v3n]

Dave, fascinating design.

How are you wiring those?
Also, why push/pull and push/push configs sharing the same enclosure?

 

[planet10]

I always like push-push woofers for the huge advantages of active vibration cancellation. The push-pull isobarik pairs allow for a reduction in cabinet volume of 1/2 so 4 arranged like this need the volume of a single driver. So a push-push pair of isobarik woofers. I happen to have lots of the woofers (vintage Foster 12” woofers suitable for sealed boxes) and got a free 12” PVC pipe that was just long enuff to make 2 enclosures.

Everything is wired so that everything is acoustically the same phase. Could be wired for 2Ω or 8Ω.

dave

 

[Dr1v3n]

What is lost by separating the push/pull and push/push pairs by any distance in the same enclosure? For instance, if I kept the tall PVC tubes and had 1 pair close to the top and the other pair towards the bottom.

 

[planet10]

With the PVC pipe you end up with a separation. I intend on putting a brace between the magnets and attach the baffles with ready rod the length of the enclosure. It will end up with s sort of steam-punk look with the external threaded rod (probably heat shrink then to damp the exposed sections).

dave

 

[Dr1v3n]

With the PVC pipe you end up with a separation...
dave

I get what you're saying about separation between the edge of the driver and ID of the PVC, but that's not what I was getting at. Looking at your pic, if you took the left pair and the right pair of sub's and stretched them out, what would be the advantages and disadvantages be IYO? (I would like to keep my precious tubes, they were not cheap)

 

[scottjoplin]

They wouldn't be acting in opposition then because they'd be in different planes, you could put a pair in each end of the tube, then you'd still get force cancellation, also the larger enclosure give you lower bass extension