The Smallest Tapped Horn

[Patrick Bateman]

I saw some amazing measurements of the Danley Sound Labs Tapped Horn Mini (TH-Mini), and decided it was worth investigation.

So here's some info on it.

First, the measurements here show that it has amazingly flat response when used in pairs:

http://www.cobrasound.com/MDSubwoofers

Which made me wonder, what's inside of that box? Based on the size of the enclosure (4.17cf), the power handling, and the impedance curve, I'll bet Danely is using a B&C 12PS100.

http://www.partsexpress.com/pdf/294-665.pdf

The TH-Mini can handle 1400 watts, Danley has been known to use B&C and BMS woofers, and the 12PS100 is the *only* 12" woofer in the B&C line that can cope with 1400 watts... So I think it's our best candidate.

 

[Patrick Bateman]

Here's the measured response of the th-mini, showing a F3 about 50hz or so.

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

 

[Patrick Bateman]

I have a P-Audio SN12MB laying around, so what can I say, I optimized this clone to work with the woofer I got!

Here's a pic.

 

[Patrick Bateman]

Here's the frequency response. This is with 200 watts into an 8ohm load, which is about 300 watts into the 5.5ohm P-Audio woofer. At this level, you're just about running out of excursion, and you'll need a subsonic filter at high SPLs.

The enclosure is basically equal to the TH-Mini. The TH-Mini has an external size of 4.17cf. This clone has an *internal* size of 3.4cf. Once you factor in the woofer and the wood, you're looking at an equal footprint.

Note the efficiency is lower - however the F3 is slightly lower also.

 

[Patrick Bateman]

Wanna buy that P-Audio woofer? Here's where you get it for $150:

http://www.loudspeakersplus.com/product.asp?specific=johmmrq0

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

 

[Patrick Bateman]

Don't want to use the SN12MB?

Well here's some simulations with the exact same enclosure, and different woofers.

Here's a simulation of the enclosure above, with the B&C 12PS100, the same woofer I believe Danley Sound Labs is using in the TH-Mini.

The response is all but identical; it's a bit shallower in the midbass. The B&C has more excursion, will play louder, and costs more.

 

[Patrick Bateman]

So you don't want to spend $207 on a B&C 12PS100?
You're too cheap to spend $150 on a P-Audio SN12MB?

Well how about $50 for a pair of MCM 55-2421 woofers?

Here's what the response is like with my favorite cheap woofer.

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

Admittedly it's rougher than the B&C or the P-Audio, but that's because the FS of the MCM is way too low. In the real world, it won't be as peaky, especially if you use two or three cabinets.

 

[Patrick Bateman]

Interestingly enough, a *quad* of MCM woofers has the best response of all. They offer the flattest response, the lowest excursion, *and* the lowest price. At 45hz the MCM has a full four DB more output!

The MCM 55-2421 is very hard to beat.

Check out the response graph.

 

[Patrick Bateman]

I wonder if Danley Sound Labs should start using a quad of MCM woofers? Half the price, less excursion, in the same box.

WOW!

 

[Patrick Bateman]

Here's the parameters, if you want to model it yourself. I kept the enclosure identical for all woofers; all I varied was the woofer itself.

 

[MaVo]

Hi Patrick, you can make a TH with a mouthsize of about 1 * SD with good response. The simulation shows a Beyma 12P1000ND in a 60Liter tapped horn. Doubling the mouthsize gives you additional 3db maxspl.

 

[djk]

This is about an inch taller, and a couple of inches deeper. Kicks severe butt. A JBL2206 will also work in the same box.

 

[djk]

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

Mid-Bass / L12P540
--------------------------------------------------------------------------------

• high power 12" mid-bass
• very good power handling, excellent linearity and very low distortion
• diameter: 12"
• impedance: 8 Ù
• power: 400W rms, 800W program
• spl: 97 dB
• frequency range: 50 Hz–2 kHz
• voice coil: 3" copper
• baffle cutout: 11.2"
• depth: 6.1"
• weight: 18.7 lbs

 

[djk]

| 50 Hz Tapped Horn

Def_Const |Horn Dimensions

{
a1 = 150e-4; |Area at throat (cm^2)
a2 = 250e-4; |Area at rear of driver (cm^2)
a3 = 1100e-4; |Area at front of driver (cm^2)
a4 = 1200e-4; |Area at mouth (cm^2)
l1 = 15e-2; |Distance from throat to rear of driver (cm)
l2 = 178e-2; |Line distance from rear of driver to front of driver (cm)
l3 = 25e-2; |Distance from front of driver to mouth (cm)
}

Def_Driver 'Dr1'

| RCF L12P540

Sd=530cm2
fs=59Hz
Qes=0.36
Qms=11
Vas=45L
Re=5.6ohm
Le=1.8mH

system 'S1'

Driver Def='Dr1' Node=1=0=3=4
Waveguide 'W1' Node=2=3 STh={a1} SMo={a2} Len={l1} Conical
Waveguide 'W2' Node=3=4 STh={a2} SMo={a3} Len={l2} Conical
Horn 'H1' Node=4 STh={a3} SMo={a4} Len={l3} Conical

 

[FlipC]

Still cant get my head around Hornresp.

Driver specs:
Power handling: 600 watts rms
Voice coil diameter: 2"
Voice coil inductance: 1.81 mH
Impedance: 4 ohm
DC resistance: 2.60 ohms
Frequency range: 20-450 Hz
Magnet weight: 112 oz.
Fs: 18.8 Hz
SPL: 90 dB 1W/1m, 93.4 dB @ 2.83V/1m
Vas: 232.2.
Qms: 8.66
Qes: .39
Qts: .38
Xmax: 15.1mm
Re: 2.8
Le: 1.82
Mms: 297.1
CMs: 0.24
Sd:829.6
Vd:1252.7
BL: 16

Trying to put this into a box of roughly 104.5 L

I don't understand how to get some of HRs measurements. Like Rms and Mmd. I also haven't figured out how to define box parameters. Layout equals a 13 foot horn length (roughly) within the space of 7 folds. 13 foot would (roughly) get me the 1/4 wave length for 50Hz ?


Help a laymen comprehend?

 

[djk]

"Trying to put this into a box of roughly 104.5 L"

The driver you listed is not suitable for a 50hz tapped horn.

"I don't understand how to get some of HRs measurements. Like Rms and Mmd. I also haven't figured out how to define box parameters. "

You don't have to understand them, just enter as required. The 'HELP' section tells you how to do this. The program calculates what it needs from common T/S parameters.

"Layout equals a 13 foot horn length (roughly) within the space of 7 folds. 13 foot would (roughly) get me the 1/4 wave length for 50Hz ?"

The speed of sound is roughly 1130 ft/sec, the 1/4W of 50hz is thus 5.65 ft, or 67.8 inches.

As you can see from my 50hz AkAbak script, the main horn length is 1.78m, or about 70 inches.

 

[Patrick Bateman]

As DJK alluded to, that's one of the great benefits of a tapped horn. It doesn't require a "typical" subwoofer driver, where the FS is very low, nor a "typical" horn driver, where QTS is very low.

 

[GM]

Driver specs:

Trying to put this into a box of roughly 104.5 L

What make/model is this?

BTW, you didn't say what the XO point is, so don't know how much BW you want to try and get out of it.

As already noted, this is a very poor choice for a 50 Hz TH, especially in ~104.5 L due to its high Vas, but curiosity got the best of me to see how poor a choice it is:

GM

 

[Patrick Bateman]

After what I learned on my Tapped Horn for Dummies thread, I realized that the best driver for a 50hz horn would have an FS in the range of 60-100hz.

 

[djk]

Right you are.

RCF L12P540

Sd=530cm2
fs=59Hz
Qes=0.36
Qms=11
Vas=45L
Re=5.6ohm
Le=1.8mH