Double 15” and Horn Drum Fill

Peter Morris

Senior
May 8, 2011
987
89
28
Australia
I decided I needed a decent cost-effective loud drum fill. This is what I came up with and I though some others on this forum may be interested.

1 x Box 1220mm high x 550mm wide x 500mm deep

2 x ports – 100mm dia 80mm long plastic pipe

1 x BMS 4592nd + BMS HF crossover 16 ohms
http://www.bmsspeakers.com/index.php?id=bms_4592nd

2 x Faital Pro 15hp1060
https://faitalpro.com/products/files/15HP1060/8/15HP1060_datasheet_8.pdf

1 x EV HP940 ( had to cut a little of the side off to get it to fit}
https://www.electrovoice.com/binary/HP940_Horn_EDS.pdf

1 x Behringer iNuke 6000 DSP

The design

In my opinion the traditional double 15” + horn speakers don’t really work. The two 15” drivers don’t play well together above 500Hz and their directivity and the phase cancellation between the two 15's becomes problematic. The trick with this design was to find a horn and compression driver that can cross happily that low and still produce serious SPL. In this case I have selected 600Hz crossover as a bit of a compromise - not perfect, but it seems to work well enough.

Being intended for use as a drum fill I could not afford the latency associated with FIR filters and a cheap solution was to use a Behringer iNuke 6000 DSP to provide amplification, crossover, PEQ and limiting … I know, not the best solution but cost effective and simple.

Here are the results. I actually managed to get a slightly better frequency response (40Hz to 20KHz +/- 1.5 dB at the drummer ear :)) but did not save the screen shoot.
 

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David Morison

Freshman
Aug 21, 2012
146
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18
Aberdeen, Scotland
Hi Peter,
Great looking project well executed as always, thanks for sharing it.
Can I ask, do you find that the 2 100mm ports are enough for the 2 15" drivers when it's cranked up?
I've not used those drivers but a quick play in WinISD suggests they might be happier with a bit more vent area.
Many thanks,
David.
 

Peter Morris

Senior
May 8, 2011
987
89
28
Australia
Yep ... the vent area is a bit small. I would suggest unacceptable for a sub application but in this case the 15's are operating up to 600Hz so its unlikely they will be getting full power at 40Hz. I was also hoping that it may provide a bit of Xmax limiting should the engineer do some crazy EQ-ing on the drum monitor ... which does happen.

I was also expecting the box could be on top of a double 18 for FOH or side fill applications. Crossed at 80Hz there are no issues with port velocity.

If you want more of a general purpose box or a sub I think you should use 4 or more vents and they should be flared, in fact I would use a different port design all together. In this case I wanted to get the two 15's and horn as close as possible to minimise the problems between 2/3 different acoustic sources.

The big issue for me was getting the directivity correct and having it sound really nice with great impact - which it does. The box is a little large for this driver and there is a small bump in the frequency response - accordingly there is a -3 dB filter Q2 at 40Hz to get things to perform correctly in the time domain.

Edit - Just to add a bit more – by crossing over at 600Hz allowed the use of LF drivers more optimised for sub applications than mid-range performance, and hence more LF output.

Often a drum monitor is a 15”+2" horn on top of an 18” sub, however by not crossing over to a sub at 80 – 100 Hz you can save about 5ms of group delay and hopefully give the drummer more impact and have a box that performs very well for this application. I don't think a drum monitor requires extended LF performance.

What was also critical for me was ensuring that the driver remained in its linear Xmax range during its intended operation – in this case about +/- 8.5mm (Hvc – Hgap)/2 although the driver is rated +/-12.5mm.

By keeping the VC in the magnetic gap you have a better chance of maintain mid-range clarity.

The 15hp1060 has a long VC (28.9mm) and is quite efficiency. It also has an FS of 40Hz which is very high for a driver with a rated Xmax of 12.5mm and suited the alignment I wanted – solid performance to 40Hz, but I didn’t want to go lower.

Here is the Xmax at 2000 watts with the applied filters -



Hi Peter,
Great looking project well executed as always, thanks for sharing it.
Can I ask, do you find that the 2 100mm ports are enough for the 2 15" drivers when it's cranked up?
I've not used those drivers but a quick play in WinISD suggests they might be happier with a bit more vent area.
Many thanks,
David.
 

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Max Warasila

Graduate
Feb 20, 2013
1,140
40
48
Richmond, VA
I've started using the new NX[x]000DSP amps for my latest 12" 2-way build. They're killer little amps, and have a slightly better sound than the iNukes.
 

Peter Morris

Senior
May 8, 2011
987
89
28
Australia
Hi Max,

The initial concept was to build a simple cost effective drum fill using some parts I already had. I was going to build a passive crossover but I found a secondhand iNuke for about the same price as it would have cost me to build the crossover, so it became an active 2-way with a passive crossover on the BMS 4592ND.

The box seems to have turned out much better than I expected ....and the iNuke performs very well for the price. I think 3 of the new NX series with a passive crossover on the HF driver would be a cost effective way of powering the PM60 / PM90 or my double 10".
 

Peter Morris

Senior
May 8, 2011
987
89
28
Australia
Tested the drum fill on Friday and Saturday on a couple of small shows (not the one in the video) with the LOUD Australian rock band Rose Tattoo

The limiters were on all night but the drummer thought it was "awesome" :)

The idea of a large horn and a BMS4592ND crossed over quite low to a couple of state of the art 15's seems to work.

FWIW I ended up crossing at 550Hz, a bit lower than my inital settings, it adds a bit more clarity.
 

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Joris Achternaam

New member
Nov 29, 2019
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0
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Belgium
Thank you for sharing this Peter.

I actually have been looking at ways to cross an efficient 12" with my BMS 4592 over some 15" kickbins; but reading this thread I'm wondering whether it wouldn't be an option to just take the more straightforward route and just use double 15's, ditching the kickbins.

The drivers I have are Eminence Kappa Pro LF2's, and I would like to couple the 4592ND with the official BMS 2236 horn (60x40°) in trap cabinets so if needed I can splay them horizontally in pairs. These cabinets would be used in stacks, on top of tapped horns which run up to 90Hz.

The processing available is an XTA DP446 with powersoft k-series amps.

I realize that these drivers aren't top of the line, but since I already have a whole bunch of them it would be nice if they could be used. If not, do you think getting a different driver (like the FaitalPro, suggestions welcome) would still be a better option than going the 15" kick + 12" mid route? It would definitely make for a simpler build and setup.

Any advice?
 
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Peter Morris

Senior
May 8, 2011
987
89
28
Australia
Hi Joris,

I’m not sure how low you can use the BMS2236 horn, its cut off frequency is 400Hz so you maybe able to use it to around 600Hz with good results.

If you can do this then 2 x 15” speakers will work quite well below it. The Eminence Kappa Pro LF2's have about half the Xmax of the Faital Pro 15hp1060’s I used … but if you are crossing over to a sub at 90Hz there should not be an issue with Xmax.

You will however need to use a different box volume and tuning frequency to suit these speakers.

With this combination I don’t see any advantage with a kick bin. If you were to use 12” drivers under the BMS horn then you could cross over to the horn a little higher and get a bit more SPL out of the 4592 but you would have less low mid capability.

If you use this combination for EDM then I suspect there would be an advantage using a kick bin between the 12's and the sub.
 

Peter Morris

Senior
May 8, 2011
987
89
28
Australia
What's the internal volume for the 15" drivers?
No sure, I did calculate it from the box dimensions at the time ... it was a little large and I suspect if I reduce the volume a little I could have got slightly better results, but I more or less had some spare cabinets that were a perfect match with my double 18's for truck packing ....and the drivers and horn I had fitted perfectly.

The basic concept was a double 15 and horn that crossed over low enough (600Hz or less) to work properly and still produce high SPL's.