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Old 13th November 2012, 05:07 AM   #1
diyAudio Member
Join Date: May 2012
Default Tapped Horn amplification and signal processing

I'm looking to build a Tapped horn style home theater subwoofer. This would be my first speaker build in 15 yrs (first was a box for my car that had nearly zero 90* angles.) I'm looking at building the Kraken 1x12, however I have no idea how to power it. Or if it needs any signal processing. I had been researching a ported 12" sub, but I have the space and want the lows the TH brings. However, the reading I've been doing with Tapped Horn and it sounds like it's amplifier and signal processing is quite a bit different. My old home theater receiver has a cutoff at 100/150/200hz. I had been thinking on a plate amp and changing resistors as needed, But I'm not sure that would be enough in the way of signal processing.
I'm open for suggestions.
I'm not afraid of building this, and I can handle a soldering iron, so changes to a factory amplifier would be acceptable.

I was also wondering how the Kraken would handle the dual voice coil version of the JBL gto1214 ff I chose a stereo amplifier.

Thanks again
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Old 13th November 2012, 01:17 PM   #2
diyAudio Member
Join Date: Jan 2011
M 2cents....
Go with a used pro amplifier (qsc rmx, qsc mx, crown ce, etc)
And a mini dsp for high pass filter and parametric EQ

Most receivers (even some of the middle-high end) don't provide high pass filters for the subwoofers. They only low pass the signal to the subwoofer, and don't really provide a ton of EQ options for the Low frequency.
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Old 13th November 2012, 03:08 PM   #3
jbell is offline jbell  United States
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Join Date: Apr 2003
Location: .
Yes the BASH amps have a high pass, using a salen-key filter. By changing resistors, you can alter the high pass to provide the needed driver protection for a TH.
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Old 23rd November 2012, 10:11 PM   #4
diyAudio Member
Join Date: May 2012
Update: I found a guy who happens to live locally on e-bay with a few QSC MX 1500a's that were pulled out of a theater. I purchased one for this project. After getting it out of the car, I look at the back of the amp and find it has the QSC SF-1 subwoofer filter in it. A quick search on Google came up with a PDF.

"Ideal for adding subwoofer amplification to an existing full-range system, the SF-1 offers adjustable and selectable low-pass filtering for both channels of the amplifier, in addition to adjustable high-pass subsonic filtering. The filter slopes are 12 dB per octave, and the filter frequencies are programmable via provided
SIP resistor networks."

also in the documentation

"Typical subsonic
frequencies available with the provided SIP resistor networks are 20, 25, 32, 35, 40, 50, 63, and 80 Hz."

Filter type:
second-order butterworth, Q=0.707
(LPF and unboosted subsonic filter)
second-order, +6 dB boost, Q=2
(boosted subsonic filter)

The lowpass is currently at 100hz. (18k Ohm)
The highpass is currently at 32hz (56k Ohm)

I now need to select a good high pass filter setting for the single driver tapped horn. Or should I still look at a miniDSP?

I know the DSP helps flatten out the eq with the room and what maybe generated from the sub. I do not have equipment to take accurate measurements of the rooms frequencies.
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Old 24th November 2012, 07:10 AM   #5
epa is offline epa  Netherlands
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Join Date: Apr 2010
Location: amsterdam
the active filter should do fine for your purpose.
you just need to adjust the rn for your th.
one good thing about music ,when it hit you feel no pain.
so hit me with music
. hr driver db
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Old 24th November 2012, 03:13 PM   #6
diyAudio Member
Join Date: Jan 2011
That's the amp I'm using. THX approved for theater applications. BEAST of a sub amp (not 5kw, but for your application it's way overkill and a great amp)

I modded the fan with this, made it much more tolerable for low level listening, my amp is only 10 feet from my listening position.

Thermocool 110 VAC Fan 80 x 25mm Sleeve Bearing 19 CFM 250-010

If the pots are scratchy when you adjust the gain, get some new ones from QSC. They were like $25 shipped for the pair, and then you have to solder them onto the boards.

Come to think of it...I have the 1500 not 1500a.....the 1500a has a two speed fan. So check the fan voltage before ordering a new one, if you are planning on modding.
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