Horn Extender/Wave-guide for TH

[weltersys]

My main PA uses rather small horn top cabinets, only 26.5 inch wide. The horn does not do much below 200 Hz, but a lot of cones makes the response OK to around 70 Hz.
When I need a bit more low end and directivity I use wave-guides in front of the stack, it gives the low end of the horn a 3 dB boost down to around 70 Hz, and maintains the 90 degree pattern down pretty low.

Using bass reflex cabinets or standard horn cabinets below 70 Hz, the wave-guides did not show any level increase in that range.

However, in front of the Keystone TH cabinet, the wave-guide averages more than a 3 dB increase in level over the entire sub range.

The wave-guide/extender significantly increases directivity too.

The wave-guides are four pieces, break down to a package about 6 x 20 x 54.75. Ratchet straps are used to attach the wave-guide to the cabinet, no rattles with full power.

The wave-guides do take a few minutes to set up, but considering the cost to output level increase they afford in a small space, the equivalent of doubling the speaker cabinet without paying for a second speaker, quite worth it on gigs that need a lot of level with the minimum power.

Art

[Top Shelf]

Would/was there any difference to the output if the extender were to be made to fit just the height and width dimensions of the mouth of the keystone. Or did you find better results with the full length/width unit?
This is all very interesting and I wonder if this effect works on other types of enclosures. Looks like you have done a ton of work to get this box just right, good job!
Will this designs be replacing your lab 12 BR's?

[weltersys]

Originally Posted by Top Shelf

Would/was there any difference to the output if the extender were to be made to fit just the height and width dimensions of the mouth of the keystone. Or did you find better results with the full length/width unit?
This is all very interesting and I wonder if this effect works on other types of enclosures. Looks like you have done a ton of work to get this box just right, good job!
Will this designs be replacing your lab 12 BR's?

I will probably keep one pair of the dual Lab 12 for small shows.

The extender happened to work quite well with the Keystone sub, it may work well with other TH designs of similar aspect ratio.
Reducing the size to the height of the mouth would probably reduce the gain by half.

[Top Shelf]

Awesome , good to see your design will benefit your system.

[weltersys]

Originally Posted by Top Shelf

Awesome , good to see your design will benefit your system.

A TH extender may benefit many other systems.
A 3 dB increase with a sheet of plywood is a big deal.

[salzburgsoundsystem]

Art,

this is quite interesting, to say the least!

Wave guides have been in use for a long time, and are well known to work for front loaded horns. However, they are not really in the vogue currently, so for many they may appear ground breaking.

I am not sure, but I suspect you may be one of the first to use a wave guide for tapped horns. I would like to say, that like JBell and other builders, your research and voluntary sharing of findings should be lauded!

And now some questions:

Why is the wave guide the height of the cabinet, as opposed to being the height of the mouth?

Have you considered - If you built the wave guide as a rigid unit, but with at least 3 sides angled - you could nest/stack them neatly in one another?

What angle are your sides at?

What minimum length do you recommend for the sides or for path extension?

If I make them for the JBELL stadium horns, would you suggest any differences to your approach?

Thanks!

Kind regards, Ben

[weltersys]

Originally Posted by salzburgsoundsystem

And now some questions:

Why is the wave guide the height of the cabinet, as opposed to being the height of the mouth?

Have you considered - If you built the wave guide as a rigid unit, but with at least 3 sides angled - you could nest/stack them neatly in one another?

What angle are your sides at?

What minimum length do you recommend for the sides or for path extension?

If I make them for the JBELL stadium horns, would you suggest any differences to your approach?

Thanks!
Kind regards, Ben

A ridged side “Dixie Cup” approach could save time in set up if one has the room, the Community Leviathan did that for their horn extenders.
I don’t have the room for that, the wave guides (double in height to what was shown in front of the Keystone sub) fit on either side of speaker cabinets in the front “V” section of my 5 x8 foot trailer.
Having angled top and bottom also makes stacking problematic, another reason in favor of a flat top and bottom.

The wave guides I have were made to extend the mid/high horns in my system, the horn extension is 90 degrees (45 degrees each side), 15 inches from front to back.

As I mentioned in the OP, the wave-guide/extender increases the low end of the mid horn by about 3 dB down to around 70 Hz, but using it in front of bass reflex cabinets or folded horn cabinets below 70 Hz, the wave-guides did not increase level noticeably in that range.

So I really did not have high expectations when I tried the wave-guide with the Keystone sub, though a quick model using Hornresp looked promising enough for me to do the test.

I stack my top cabinets on top of my sub cabinets.
When I use the wave-guides, they stack from the ground up, so whether they would do anything for the sub response really made no difference .

The 3 dB increase across the entire sub range was a pleasant surprise .

The Keystone sub has a rather large front panel to mouth compared to many TH designs, which makes for a larger boundary. The wave guide more than doubles that boundary, and when mirrored by the ground plane, makes for five times the frontal area boundary.
The large boundary increases directivity so forward gain is increased, while level to the sides and behind is reduced, the same as what is observed when multiple TH are arrayed.

Extending an array’s front to double the area probably would also increase directivity by a similar amount as I measured.

As far as using a wave-guide with the JBELL stadium horns, (or any other tapped horn) I’d suggest the bigger, the better, but I’d expect from my test that doubling the frontal area should result in 3 dB forward gain, and a corresponding rearward loss.
My educated guess would be to make the wave-guide twice the width as height, as the height is doubled by the ground plane, and a large area square should be optimum as a boundary.

That said, a taller aspect ratio will reduce vertical coverage while maintaining horizontal coverage, so if the audience is all on one plane (no balcony seating) a square mouth shape may be preferable.

Won’t cost anything but time to prop up some plywood (assuming you have some sheets already) in various configurations and measure and listen to the results.

[weltersys]

Found a test done using FLH with the same type of waveguide/extension as used on the Keystone TH, the waveguide worked better than I remembered, chart below.
The pair of Chorn cabinets have a frontal area the same as a single Keystone.

Just did more testing using various BR stack configurations with and without flat extenders:
Multiple Cabinet Combined Response

[Djim]

[salzburgsoundsystem]

May I ask, isn't some flare important for these extensions?

Regards, Ben

P.S. nice sim!