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mulletdude 9th November 2010 10:29 AM

18 inch labhorn design.
Hello i have two behringer b1800x pro PA subwoofers rated at apparently 1600 watts a peice RMS. i was wondering if there is any way to design a labhon or a similar horn based design out of these subs that would fit through a standard 30 inch door and carryable by 2 people that would dwarf the apparent 136 DB per sub im getting now. I dont have a SPL meter to measure but im sure i could scrounge one up easily. i always run the subs together which according to this forum and many others will give me a 3 DB gain bringing it to 139 if the specs of the bins are correct. if anyone has measurements of these bins already and can help that would be awesome. thanks in advance

Rademakers 9th November 2010 02:57 PM

From the specs I've gathered they're 450 Wrms and 1600 W peak. Meaning at 97 dB/W/m they would get you 124 dB/1 m + 5-6 db if you're using two standing next to each other. Forgetting power compression for a moment you're getting 130 dB/ 1 m.

Figuring Behringer used some medium Qts, medium Vas drivers for these bins (though you could always measure the T/S-specs for sure), there are some 30-40 Hz diy-designs floating on the web, that would meet your door-constrains and add another 3-5 dB dependant on how large it might get.

You could always put them against a solid wall or in corner so they will truely live up to the specs ;)

Best regards Johan

mulletdude 9th November 2010 03:01 PM

ok thanks for that information. where would i find information on measureing T/S specs. also can you link to a couple designs.

davygrvy 9th November 2010 03:51 PM

sorry to be the bearer of sobriety, but a horn works by transforming pressure at the driver to displacement at the mouth. When you choose to start with an eighteen inch driver, you lose some ability to create pressure as the cone is more fragile compared to a twelve. Cerwin-Vega gets away with it by having very little compression ratio so as not to tear their driver to shreds. Low compression ratio is low efficiency. The idea with a horn is to create pressure at the throat. The horn makes the displacement. Small drivers are better at creating pressure before they tear.

mulletdude 9th November 2010 03:56 PM

well then could someone at least suggest a better box design that will increase my SPL?

davygrvy 9th November 2010 04:10 PM

I can't without knowing the T/S data. One size doesn't fit all drivers... by a long shot.

Measure the T/S params with this.

AndrewT 9th November 2010 04:38 PM

Theoretically an 18inch folded horn could be similar to a dual 12inch folded horn.

But the Labhorn has a pair of drivers designed to get the best out of that Labhorn shape.
Any other driver (of any size) is unlikely to have the optimum T/S parameters to get the best out of an equivalent folded horn.

How about displacement? Can the Xmax of the 18 match the Xmax of the dual 12 for similar displacement?

It only has to be less than 29inches wide to fit through your doorway. With an 18inch driver and 19inch internal width, 3/4inch ply comes to 20.5inches wide. lot's of room to spare.

kornnylike 9th November 2010 11:03 PM

Mulletdude ckeck out the Ciare 18 inch bass horn that Soho design for me under Can this work.We build six of them in the summer and they sound crazy.

davygrvy 10th November 2010 01:07 AM


Originally Posted by AndrewT (
Theoretically an 18inch folded horn could be similar to a dual 12inch folded horn.

Generally speaking, the twelve(s) will squash the eighteen as you can run the twelve(s) with a higher compression ratio compared to a fragile eighteen. Compression ratio comes into play at the LF cutoff, which is responsible for how deep it goes with any authority.

But its hard to talk in generalizations when we don't have the T/S params to experiment with.

Do you have a horn for an 18 inch driver?

soho54 10th November 2010 01:23 AM

The old smaller driver is always better theory doesn't hold much water any more, unless you are limiting the enclosure size to something really small.

DSL uses 18"s and 21"s in tapped and regular horn flavors, and have no problems running them at insane levels. They even use 18"s in the new answer to the Labhorn.

10 years ago you couldn't find may 18"s that could handle +3:1 compression, but now there are a few. It seams like almost every manufacturer is putting them out now.

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