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Old 10th November 2010, 05:03 PM   #11
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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?

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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.
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Old 10th November 2010, 05:26 PM   #12
soho54 is offline soho54  United States
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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.
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Old 11th November 2010, 05:16 AM   #13
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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.
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Old 11th November 2010, 05:44 AM   #14
soho54 is offline soho54  United States
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Quote:
Originally Posted by davygrvy View Post
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.


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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.
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Old 11th November 2010, 08:44 AM   #15
CLS is offline CLS  Taiwan
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No compression (1:1)

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Old 11th November 2010, 11:33 AM   #16
AndrewT is offline AndrewT  Scotland
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I have quite a few sims with compression ratios between 1:1 and 2:1.
I never considered going to 3:1 or more after reading about throat distortion at high SPL levels.

I have to admit that I have not completed my corner loaded bass horn.
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Old 11th November 2010, 03:39 PM   #17
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Do you need 30 Hz or is 40 Hz fine (just as the B1800X does)?

Do you want a FLH or will a RLH or TH also do?

Best regards Johan
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Old 11th November 2010, 04:53 PM   #18
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No compression (1:1)
That's a nice sim, but a 9600cm2 mouth is kinda large. Given the width to fit a doorway is 74cm wide, just the mouth would be 129cm (51") tall. You have a fold for this? To get that response in 1/2 space, you'll need 4 of those cabs in a stack.
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Old 11th November 2010, 05:12 PM   #19
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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.
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Old 11th November 2010, 05:23 PM   #20
AndrewT is offline AndrewT  Scotland
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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.
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