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
David
 
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
 
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.
 
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.
 
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?
 
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.
 
Aren't we talking about a stock 18" driver in a Behringer B1800X-Pro? It's a ported cab. How strong do you (all) think this is for use in an FLH? Without recommending mulletdude go to $1000 18" driver that's stronger and better suited for use in an FLH, what can he use it for as is?

[IMGDEAD]http://www.behringer.com/EN/images/lightboxphotos/B1800X-PRO_P0288_Left_XL.png[/IMGDEAD]

3:1 isn't much compression ratio. The Cerwin-Vega L36 is around 2.4:1 from what I calculated from the drawings. I found 5.25:1 worked pretty nice for an HT project I did using nine MCM 55-2421.

Tapped horns don't stress the driver for pressure, but do stress it for excursion in the pass-band, and require a deep high-pass for excursion protection below cut-off. This would be a good recommendation if only we knew the T/S params for his driver.
 
Your comments seemed more like an all encompassing one, not directed at just this driver. I'm sorry if my comment seemed like I was saying anything in particular about this driver, as I wasn't. I don't know anything about it, but there is no reason not to sim it out with a low compression horn. You don't have to have high compression in a horn.


As for TH not having high compressions, I would suggest looking at the ones used in the DSL full range lines. There are 12"s and 15"s behind those two little holes in there. The common DIY builds are one thing, but the originals are a bit different. :D
 
I've never seen inside a danely.. but the mouth size isn't related to compression as seen by the driver. it's the differential pressure across the cone.

if I can't do high compression(>4.5:1) for an FLH bass horn, it isn't really worth it. I may as well just have a sealed box. I mean, I'm going to have to eq out all that wonderful rise at 110Hz anyways if I have 1/4 wave tuning with low compression and short path. I want the cutoff in the high efficiency area. With higher compression I can keep a reasonable path length.

mulletdude could try experimenting (in a simulator) with a tapped horn once he gets those T/S values. Those do great when you have a nice balanced design to get the total efficiency up without being as massive as an FLH of equal performance.

Though FLHs do great when run with many cabs.. like eight for great mutual coupling so an 1/8 space sim on a single behaves with eight in full space for LF cutoff. Then a short 1/4 wave tuning works great and makes performance sense.

If he's staying with just a single cab, a low tuned TH might be a better choice.

Hopefully his driver can work in a TH.
 
I've never seen inside a danely.. but the mouth size isn't related to compression as seen by the driver. it's the differential pressure across the cone.
Mouth size? I never said anything about mouth size. :D


I mean, I'm going to have to eq out all that wonderful rise at 110Hz anyways if I have 1/4 wave tuning with low compression and short path. I want the cutoff in the high efficiency area. With higher compression I can keep a reasonable path length.
Short path? Low compression does not mean a shorter path. We don't want a Scope Bin.
 

CLS

Member
2005-06-17 6:58 am
Taiwan
No compression (1:1)

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:D
 
I never considered going to 3:1 or more after reading about throat distortion at high SPL levels.

Throat distortion comes from the opposite end of the cycle of doubling atmospheric pressure which is a vacuum. You can't get less than a vacuum, but you can still increase pressure, thus the distortion. Off-hand, I think it's 194dB.

I know that was a problem with the EV MT-4 where they put four DH-3 HF compression drivers through a single horn. It was a great space saver, but they bumped the physical limit where water both boils and freezes at the same time.
 
Triple point is not a physical limit. It simply defines a temperature/pressure at which that particular compound can change from solid to liquid to gas and back, i.e. the compound can co-exist in any of the three states at the triple point.

Distortion resulting from high compression ratios and high SPL does not just suddenly become audible when throat pressures reach 194dB.