Isobaric sub cab?

[jondog]

Anybody ever try one of these?

http://cgi.ebay.com/ws/eBayISAPI.dl...MEWA:IT&viewitem=&item=130067013831&rd=1&rd=1

 

[bongomania]

I haven't, but I am impressed by how straightforward and BS-free his ad copy is. He shows a photo of the internal design, and talks plainly about what's involved in the build, and doesn't make any outrageous claims. I would be inclined to buy one just out of relief!

 

[lug]

I've built a couple. At lower frequencies the theory works well. In essence you get no dB gain but you do get to halve the size of the box. Expensive way to get it but would love to try it with 8" or 10" neo's for a small practice box with good bottom. I made a dual 8" once and it had impresive bass for the size.

 

[billfitzmaurice]

I've built a couple. At lower frequencies the theory works well. In essence you get no dB gain but you do get to halve the size of the box. Expensive way to get it

Quite right. The response and output is the same as one driver in a box twice as large (net volume). The downside is it has double the driver cost and double the driver weight. Because of the size savings isobariks were popular in home hi-fi use until about ten years ago, when long throw subwoofer drivers pretty much rendered them obsolete. Because of the weight and driver cost issues they never caught on for pro-sound applications. Performance wise a ten in a horn loaded cabinet of roughly the same size would beat it handily.

 

[Razman]

I built a 2x15" isobaric box for my car in the early 90's. Yes, that was back in the day when you needed a huge box for those subs, and going isobaric was a solution to that. However, this box was still big, but the bass was incredible--it had a 6db gain at around 35 Hz, and was great for playing bass CD's through. It lacked punch, however. A couple of 10's would have fixed that, but today's woofers require less space.

I don't doubt that you could get some incredible lows from it, but I wouldn't use it without a 4-10 or something on top of it to get good mids and highs. Keep in mind, the port of the box is what makes the sound, not the speaker. In that sense, it acts as it's own crossover, by only generating low frequencies via the port. The speaker acts as a motor only.

Eric

 

[A9X]

Keep in mind, the port of the box is what makes the sound, not the speaker. In that sense, it acts as it's own crossover, by only generating low frequencies via the port.

For the desription in your last paragraph, it seems to me like you're describing a dual driver 4th order bandpass enclosure (eg KEF 104/2), not an isobarik (eg Linn DMS).

 

[billfitzmaurice]

For the desription in your last paragraph, it seems to me like you're describing a dual driver 4th order bandpass enclosure (eg KEF 104/2), not an isobarik (eg Linn DMS).

It would appear from the picture in the link that it is indeed a 4th order isobarik.

 

[jondog]

Can you drop in any drivers, or are there T/S calculations?

 

[bgavin]

Almost any driver will do.

You do the T/S calculations for a single driver, then cut the cab volume in half. Only 1 driver is exposed to the enclosed cabinet volume.

As noted above, this is heavy, expensive, and generally pointless other than for experimentation.

 

[A9X]

It would appear from the picture in the link that it is indeed a 4th order isobarik.

I wasn't describing the auction link, but the last lines of Razman's post.

 

[billfitzmaurice]

I wasn't describing the auction link, but the last lines of Razman's post.

That is a simplification, but essentially correct. The 4th order part is the alignment, the isobaric part is the physical layout. Either feature can be used with or without the other.

Can you drop in any drivers, or are there T/S calculations

As in any cab the T/S specs are pertinent.

 

[jondog]

Almost any driver will do.

You do the T/S calculations for a single driver, then cut the cab volume in half. Only 1 driver is exposed to the enclosed cabinet volume.

As noted above, this is heavy, expensive, and generally pointless other than for experimentation.

You guys might remember from my other recent thread that I've got two Gauss 3883 18" drivers and can't find the T/S parameters. I'd like to do something with them. This cab is the cheapest 2x18 on ebay right now, so it surely would be heavy but not very expensive and the band I'm working with right now has no upcoming gigs on the calendar so I'm not really in need of a point

 

[Razman]

Go for it Jondog, sounds like a fun project to me. I used to have an older Sonic 2x18 cab and sold it - wish I never did, because if I set it on end and put my Trace 4-10 combo on top of it, it would be taller than me - and I'm 6'5" - and would sound just as huge.

On a different note, a while ago I saw a stand alone Fender 18" bandpass PA sub at a local guitar shop I frequent. THAT would have also made a nice addition to my rig.

Have fun,

Eric

 

[greenboy]

On a different note, a while ago I saw a stand alone Fender 18" bandpass PA sub at a local guitar shop I frequent. THAT would have also made a nice addition to my rig.

Would have been a blurry mud bath. There's a reason why almost nobody designs bandpass PA subs.

***

One instance where an isobaric still can be kind of cool: if you have a driver that would easily perform nicely in a cab twice the size it's currently in, and a lot of power available, you can make a clamshell isobaric out of it by adding a second identical driver and re-porting the cab as needed.