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Old 11th November 2011, 10:19 PM   #1
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Default Active crossover for tapped horn?

I've done enough searching and reading to know that if I choose to build a tapped horn subwoofer, I should use some kind of high pass filter to keep away the frequencies lower than the capability of my system. If I don't, I should learn to enjoy frequent replacement of the damaged driver.

What do most people use for a crossover? I'd like something with adjustable frequency points as well as some kind of level control for matching the gain of the amps and sensitivity of the speaker systems. If there are other features (phase?) that you think I need, please feel free to suggest them as well. I'd prefer to have something dedicated and self contained. I don't want to keep a PC around running some software package to do my filtering.

All my signal connects are simple unbalanced RCA types. It'd be nice if they were all balanced, but alas they are not. I intend to run one modestly powered vacuum tube amplifier for the left and right channels, which will run primarily full range. A high pass (~100 Hz) filter would be most helpful here, I think. I've got two channels of modestly powered (150 watt/ch) solid state amplifier for the subwoofer(s). I can bridge the amp mono and will most likely do so until I can build the second sub. (note - the first sub is not yet built either). I'm guessing the sub ought to be some kind of band pass from ~30 Hz to ~100 Hz, or wherever the filters for the mains are set.

Any recommendations? I'm also interested in ideas for the subwoofer driver and specific box plans. I think I want something about 12" for the driver, and 6' to 8' long for the box. William Cowan's "30 Hz Tapped Horn" is pretty much what I have in mind, though perhaps with a different woofer? I want to learn how to use hornresp, but that will take a little time and experimentation.

Click the image to open in full size.
(note: crossover points shown in the diagram are too high for my purposes.)
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Old 11th November 2011, 10:23 PM   #2
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Sallen and key or butterworth filters work well.
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Old 11th November 2011, 10:25 PM   #3
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Ty, for a TH I'd suggest a higher order filter for the HP, and they are very difficult to make adjustable due to the amount of values that need to change in perfect synchrony. I'd have a look at Bob Ellis's Active Filter PCB GB. Though the frequencies are fixed, it's well documented and will give you all the facilities you need to build an excellent crossover.
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Old 11th November 2011, 10:30 PM   #4
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A DSP (digital signal processor) is the best way to go for tapped horns. As well as HP and LP, you will need to delay the top cabinets to time align the output, the time delay roughly equates to the path length of the horn. Many TH designs have large out of band peaks, the parametric EQ available in DSP allows those to be tamed so the acoustical crossover ends up being correct.

DSPs come in a wide price range and feature set, many use Behringer units which tend to have reliability issues but a great feature set for the cost.
I use the DBX DriveRack PA, which is quite reliable and reasonably priced.
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Old 11th November 2011, 10:46 PM   #5
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Quote:
Originally Posted by weltersys View Post
A DSP (digital signal processor) is the best way to go for tapped horns. ...many use Behringer units which tend to have reliability issues but a great feature set for the cost. I use the DBX DriveRack PA, which is quite reliable and reasonably priced.
I noted one mention for the Behringer DCX2496. I admit I didn't read the feature specifications too closely, but it seemed like maybe it did approximately what I might want. After I saw all the balanced connectors on the back, I quickly lost interest in that unit. I'll go look up the DBX DriveRack PA and see if that looks like a closer fit more me. Thanks!

edit: Hmm, all balanced connectors again. Is there an easy way to deal with that?

Last edited by Ty_Bower; 11th November 2011 at 10:54 PM.
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Old 11th November 2011, 11:09 PM   #6
Tajzmaj is offline Tajzmaj  Slovenia
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Diy or ready to buy crossover ?
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Old 11th November 2011, 11:29 PM   #7
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Quote:
Originally Posted by Tajzmaj View Post
Diy or ready to buy crossover ?
Either, but more than a slight nod to "ready to buy". Price will quickly make the decision. I'm happy enough to sling solder. I did see the Elliott Sound Products P09, which was interesting. I wish it had some accommodations to adjust the frequency points and levels of the outputs.
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Old 11th November 2011, 11:37 PM   #8
Tajzmaj is offline Tajzmaj  Slovenia
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I might have some p-cad files for crossover with fixed frequency....
Did you see that mini dsp units?
It looks promising.
Well if you decide to build it diy i can search for files...
I would recommend you something really sharp if you want to avoid that annoying bass over 100Hz....muuuuuup...muuuup....
Regards, Taj
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Old 12th November 2011, 01:38 AM   #9
doug20 is offline doug20  United States
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MiniDSP is superior to all other choice posted so far, IMO and I own them all.
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Old 12th November 2011, 01:42 AM   #10
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Quote:
Originally Posted by doug20 View Post
MiniDSP is superior...
So, what is a MiniDSP? How do I set one up? Are there different versions, and if so which do I need?

I see... miniDSP in a BOX looks a lot like what I want. But how do the plug-ins work? So many choices, a good thing, but which one?

Last edited by Ty_Bower; 12th November 2011 at 01:49 AM.
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