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Old 20th September 2012, 01:35 PM   #1
Sella is offline Sella  Finland
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Default 2-way using front loaded horn and (sub)woofers

Hi all,

I am starting new a project utilizing horn loaded co-axial compression driver and cone drivers in sealed enclosure. Whole system will be active with DSP.

I have aquired Stereo Lab SL190 tractrix horn (fc = 190 Hz) and BMS 4592ND compression driver. Yes I am aware of HF-beaming issues using deep horn but this first version will be with just one horn.

I am still trying to figure out the low register. Traditionally people have used large dimension woofers (15+ in) to match the off-axis response at XO frequency. For aestetic reasons I want to use max 12 in drivers.

I plan to equalize the CD-horn combination all the around 350 Hz where horn off axis response is about -2dB at 90 deg (there is one resonance on the way, but with manageable with EQ). Then cross my 2x12" subwoofer section with steep slopes while radiation pattern is also wide (almost omnidirectional).

I am planning to use new Peerless XXLS12 subwoofers which should be ok to cross this high. With this kind of setup I could even use 10" drivers since we do not need the cone beaming at all to match polar response at XO?

Does this make any sense or have I gotten something grave wrong? I attached polar maps for the horn and for the driver to half-space.
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File Type: jpg XXLS12.jpg (56.3 KB, 356 views)
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Old 20th September 2012, 08:24 PM   #2
Pano is offline Pano  United States
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Interesting question. As this type of system is usually done with a 15" woofer. I've heard it done with a 12", and don't remember any problems.

If that horn actually plays that low, it will be a surprise to me. I don't see a 58cm horn as loading a driver down to 190Hz. 400-500 Hz, maybe. The driver can do it, but can the horn? Please let us know what you find.
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Old 21st September 2012, 07:45 AM   #3
Sella is offline Sella  Finland
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I am going to try XO the horn from about 350 Hz. I was eyeballing this measurement of AH160 (fc = 160Hz) horn. The response starts to roll off around naturally around 250-300 Hz.

My biggest concern is to get power response without a dip at the XO frequency between woofers and the horn.
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Old 21st September 2012, 07:26 PM   #4
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Interesting project.
I am reckoning to get 350Hz out of a similar horn but with JBL2482 2" throat comp drivers. They use a phenolic diaphragm.
They currently play down to 330Hz no problem in a 70cm length conical and sound good.
I just had to try a tractrix on them.
I pick up the horns tommorrow...

Oh, what DSP will you be using?

Last edited by Speedysteve7; 21st September 2012 at 07:28 PM.
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Old 22nd September 2012, 06:26 PM   #5
Sella is offline Sella  Finland
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I am going to use miniDSP 2x8 unit. I also have 8 channels of amplification, so I guess this project, strictly speaking, will be a 4-way solution :-)
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Old 22nd September 2012, 09:42 PM   #6
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Even more interesting. I almost went miniDSP but decided to keep things analogue - have nice analogue source, so didn't fancy digitizing that.
I'll be very interested to hear how you get on - which slopes you end up using etc.
I still have not completely counted miniDSP out as the flexibility it offers is amazing...
The passive crossover part for my 5 way cost more than DSP would have done - so DSP is very tempting - esp if you change drivers / horns etc.
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Old 24th September 2012, 11:34 AM   #7
Sella is offline Sella  Finland
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I will certanly keep posting as the project goes on.

I am still wondering could somebody with insight give opinion in marrying large horn to smallish subwoofer?
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Old 26th September 2012, 06:49 PM   #8
Sella is offline Sella  Finland
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There is slight progress.

I decided to go with larger woofer, a 18 incher, as experienced Finnish speaker builder recommended. It apparently causes serious problems to integrate woofers to the horn with small cones.

I chose BMS 18S430 which goes for 280e/pcs here in Finland. I am planning to put it smallish 50-60l sealed box. Couple of quick renderings attached.
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File Type: jpg rear.jpg (9.2 KB, 135 views)
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