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Author Topic: Twin folded horn - what specs for drivers?  (Read 749 times)

Tom Johnson

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Twin folded horn - what specs for drivers?
« on: March 10, 2019, 09:15:17 pm »

I have an ancient pair of Audio Centron subs, they are roughly 7ft long and weigh almost 300lbs each. I pulled the rear access panels off, and they had EV DL18-MT drivers inside, which desperately need to be reconed. I would like to get these things bumping again, and have been looking at replacement driver specs, but Iím not up to speed on what a twin folded horn needs. I see Rockville drivers for $60 each, which is less than the cost to recone the EVís. Iím looking at Emininence, SA, Dayton, and B52 Driverís on PE. What specs should I be looking for, to use these beasts in a mobile DJ / small band setup?
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Paul G. OBrien

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Re: Twin folded horn - what specs for drivers?
« Reply #1 on: March 10, 2019, 10:56:08 pm »

Can you post up some pics so we can get an idea of what you have? For a real horn the driver specs will be quite specific so to prevent you from wasting a lot of time and money you need to provide as much into as possible. I see a lot of PA speakers with the AC brand on them but not very many subs and no horn subs so there is a real question is what you have is one of their products or a DIY effort.
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Jeff Bankston

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Re: Twin folded horn - what specs for drivers?
« Reply #2 on: March 11, 2019, 02:20:07 am »

you could use the specs for the EV driver and find another driver with specs that are as close as possible. This guy has many PA woofers.

http://www.electrovoice.com/binary/DL18MT_Woofer_EDS.pdf


http://www.usspeaker.com/18.htm



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Scott Holtzman

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Re: Twin folded horn - what specs for drivers?
« Reply #3 on: March 11, 2019, 02:50:32 am »

you could use the specs for the EV driver and find another driver with specs that are as close as possible. This guy has many PA woofers.

http://www.electrovoice.com/binary/DL18MT_Woofer_EDS.pdf


http://www.usspeaker.com/18.htm

You want the Theile Small parameters to be as matched as possible.  A horn is an acoustic waveguide and has an impedance curve.  If the driver doesn't perform the same you could get unloading (no pressure on back of speaker) and other bad outcomes.  High Pass filters are incredibly important in these enclosures.

I would pay most attention to the Cms Vas Impedance Xmax Sd SPL
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Tom Johnson

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Re: Twin folded horn - what specs for drivers?
« Reply #4 on: March 11, 2019, 07:47:32 am »

Here is a video I shot this morning before leaving for work. https://youtu.be/mW2AFYTe3Rs
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Chris Grimshaw

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Re: Twin folded horn - what specs for drivers?
« Reply #5 on: March 11, 2019, 08:17:47 am »

It's a bit difficult to tell from the video, but looks like they're W-bins.

Chris
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Ivan Beaver

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Re: Twin folded horn - what specs for drivers?
« Reply #6 on: March 11, 2019, 12:50:24 pm »

Horns are very specific as to the driver parameters.

The cabinet/horn combination needs to be matched.

DO NOT assume that a "better" driver will give better performance.

Often a "wimpier" driver will give better performance in a horn.

It all depends.

I would stick with simply reconing the drivers and "hope" the design was properly done for use with those drivers and they just weren't stuck in there for whatever reason.
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Art Welter

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Re: Twin folded horn - what specs for drivers?
« Reply #7 on: March 11, 2019, 03:37:35 pm »

Here is a video I shot this morning before leaving for work. https://youtu.be/mW2AFYTe3Rs
Tom,

The EV drivers did not look that bad, other than the easily replaced dust cap. How did you determine they "desperately need to be reconed?"

They are not the original drivers, which were 4 ohm, the EV  DL18-MT are 8 ohm, so copying the EV TS parameters won't get you any closer to the original- not that there aren't far better options than either available for a FLH (front loaded horn) of this type.

The split horn path does not appear to be near 7 feet, more like 5 feet, so will cut off (Fc) around 60 Hz (one quarter wavelength), don't expect much output below that. Best to HP around 55 Hz to keep from tearing up the driver cones.

As far as the cheap cones you listed, for the most part, you get what you pay for regarding displacement- most of those have very small Xmax (linear displacement). Cheapo drivers may have only 5mm Xmax, while suitable drivers with Xmax in the 15mm+ range are available.

Doubling Xmax (and power) can allow a speaker to produce 6 dB more output, when you are lugging around a big, heavy cabinet, might as well go for something with lots of output.

Since you mention DIY, you could achieve output almost an octave deeper using a tapped horn design of a similar or smaller size, your FLHs are not going to go low regardless of the driver, putting much money in them won't change that.

Art
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