jbell's set of four tapped horns

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I'll trust you're joining the forum now and can tell us about your tapped horn project for live sound. I expect details! hehe without fear of getting the hammer. :smash:


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A bit more info

A few details, until Jim gets here and shares his side of the story.

Jim emailed me about the potential for a tapped horn design to cover 40 Hz up, and already had 3015's from another attempt that did not work.

I looked up the specs for a 3015LF and simmed a TH sub that made the numbers Jim needed, he took the ball and ran from there. I wish I could turn a hornresp output into reality as fast as Jim did.

He built a simple up/back prototype to test the design. When that worked out, he worked up a simple folding topology and tweaked the design to better fit the space he had and be much more plywood-friendly.

Initial email to the testing of four finished cabinets in a week, including a prototype tested in 2 days. Did you do anything else???

My hat's off to ya Jim. Excellent work.
Yes, the cabinets are large (approx 36"X46"X24"). This is a built-in install, so transportability was a secondary concern.

Drivers are Eminence 3015LF's.

These cabinets are not -13dB @ 40 Hz relative to 100 Hz.

Certainly they have a limited bandwidth (things do get ugly above 200 Hz), but they were designed for a purpose that takes the limited bandwidth into account.
Here's some more photos. I was going to wait for Jim, but think I'll jump the gun

An externally hosted image should be here but it was not working when we last tested it.

original test cab. He says he burned it, but didn't roast any weenies.

An externally hosted image should be here but it was not working when we last tested it.

That shows the fold he used.

An externally hosted image should be here but it was not working when we last tested it.

Here's a setup where Jim was wondering about phase steering patterns
Well they look very nice,

As I have said sometimes before, a tapped horn with the driver in the mouth is in fact very close to a normal back loaded horn (also known as 'Scoop') you can run them both in Hornresp and probably see very little difference.

I am wondering how these ones will sound compared to Rog Mogdales 'SuperScooper' loaded with an 18".

Best regards,

Was just commenting that the Hornresp simulation and Jim's measurements indicate that these are basically flat (outdoors, groundplane measurements) from 40 to over 100 Hz (which is the range Jim was looking for).

I'm sure Jim could provide more detail with respect to what he needed and how he measured them.

If I recall, efficiency was measured at ~102 dB, 1W/1M for a single, the set of four measured at 114 dB 20V/10 M, at 40 Hz.

They may look similar to a scoop, but they model and perform quite differently. The scoops I am familiar with do not have a sufficient horn path length to reach as low as these do.
I didn't mean these would perform the same as a normal 'Scoop'. Size, areas and hornlength are different so performance will not be the same. That should be clear

What I meant was, that when you use Hornresp and simulate JBells design as a Tapped Horn, or as a normal Back loaded horn, you will get about the same response curves.

This is because at the mouth of a horn, the pressure is very low (almost ambient pressure) so when the cone is in the mouth for LF performance this is not much different form the cone above the mouth.

Best regards,

@ contour

I have looked at the Super Scooper design since your post - it is quite different from the simple short-path scoop bins I have seen in the past. Indeed - a long-path back-loaded horn and a tapped horn such as this may be far more similar than I realized.

Ahhh, the more I learn, the more I find to learn......

Thank you.

Yes, I think the tapped horn variant with the driver close to the mouth is very similar to a 'classic' back loaded horn. I think the main advantage of the tapped horn is the ability to fill up the dip at around 80-120Hz which normally occurs with a back loaded horn because the direct radiating driver and mouth are out of phase.

As for stacking, I think Jbell will get the best results with the mouths of the cabinets as close to each other as possible. So virtually creating one very big horn mouth.

Best regards,

Don't Know - figured he would have been here by now.

I know these TH's are for a permanent install.
If they were to be moved frequently I would be concerned about the vulnerability of the exposed drivers to being poked...
An open grille perhaps...

It looks like it would NOT be possible to mount them reversed ( magnet in ) because of space limitations and the influence of the volume of the woofers frame & magnet structure on the horn throat?.
At least without a redesign?
The orientation of the driver was discussed somewhat, Jim elected to reverse-mount them. That bit of our discussion may have gotten lost in the other noise though - we probably exchanged 30 emails during this design, let alone the forum posts.

Anyhow - a driver flip complicates the construction a little bit and makes the cabinet slightly bigger due to some wasted space, but it certainly could be done.

Make the initial leg (L12) a rectangular section with depth sufficient to hide the magnet and basket. Use a side baffle (or two) in this rectangular section to get the taper you need.

Just don't ask me to draw it - my CAD skills suck.
It's use is for a football stadium sound system, on top of press box. That's why bass steering is important. I need to be able to spread wide the bass, without killing people right in front. (and split subs, with cancellations is not for me)

For anyone who wants to replicate this (not sure if anyone does) It's 46x36x25.5 wide. (because I used 3/4" 7ply arauco)

Points of interest in plan layout:
1st point is 10.75 down from top, 8.5 from front.
2nd point is 12.25 from top, 14.25 from back
3rd point is 18.5 from bottom, 16.25 from back.

Those are the horn fold (toward outside) measurements.

The front panel is 25.25 long, and the throat is exactly 4".

From that and the pic above showing the fold, you can get to everything needed.

Hornresp params are 600cm throat, 3000mouth, 16.9,235,16.9

I will be the first to say, this is nothing special. However it fulfills a need that none of the BF cabinets that I was working with at the time would.

If 40hz is your low frequency that you need for your PA, that efficiency at that freq sets the overall response you can achieve, as it's the hardest to reproduce and most power intensive frequency in the PA power band. (which we obviously know) A sub that's 13db more efficient at 100hz vs 40hz, helps little. If I need more 100hz out of a sub, I'll eq it in. However, If I need more 40hz... there's only one way to get that, big power and big excursion, and that limits the overall spl you can get out of your cabinet.

So.. this sub is very efficient at 40. 102.5@2.83volts according to hornresp, and it measured spot on. +-1db up to 100hz. Good enough for me. It actually measures +1 at 100hz, with 103.5. and yes, that's outdoors, over grass measurement, static test tone, calibrated spl meter, and voltmeter measurement... not an INDOOR fairy tale measurement... like some others...

anyway, I digress.

set up on a dcx2496, LR48@38hz high pass, LR24@90hz low pass, into a EP2500 really puts on a show on the cheap.

These use eminence 3015lf drivers, just under 2 sheets of 7ply 3/4" plywood per cabinet, a dcx, and a ep2500. All 4 cabinets were built in a day. They are brain dead simple to build. Yea, they probably could use some more bracing. And if built with 1/2" would require significant bracing everywhere. My tradeoff was the 3/4 was heavier, more expensive and needs less bracing, and allowed me to build super fast. So it was a good trade. Mouth doesn't vibrate, most vibrations I feel are in the front panel (no bracing... should have put some in)

This is a huge system on the cheap, so I guess that's it's value here.

oh, and yes, they'll be grilled, to keep the bugs out.
Yes, everything on pressbox.
My tops aren't dr's. They are my own designed slot loaded dual 10's with 18" long horn paths. I found the OT had too much boxy 250-500 sound and not enough mid-bass, and the longer horn path moved that cabinet gain down into the frequency range I really needed outdoors.

The only eq I 'have' to have is the 8.5khz piezo eq, to get rid of that spike. (-3db q10) The 1025's are just much better controlled than the 1016's.

This whole stadium project was an exercise in trying to get cabinets (tops and subs) to really provide the most output at the hardest to reproduce frequencies, knowing that everything else can be accomplished with a little eq.
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