More info on the way minidsp is used in the IRS V setup at PS Audio

I remember on one of the Ask Paul episodes he mentioned that they use minidsp products with the IRS V setup they have.

I would really like some more details about that.

I’ve done a bit of searching but nothing has come up.

Anyone? Paul?

Well, we’ve tried a couple of different products from minidsp with pretty good results.

The IRS woofer towers have a custom amplifier from Bob Stadtherr here (that is 6 x 700 watt). We’re currently using a minidsp 2x4 balanced (now EOL) for crossover and EQ. We’re not running any DSP/EQ on the rest of the system, just the woofer towers.

Long term, we may put something a little nicer in there or upgrade the power supply on it but it’s working reasonably well.

There are some pretty significant room modes in that room (and you don’t have as much placement flexibility with 7’ tall, 350 pound woofer towers) so I used some measurements in room EQ wizard and a a multi sub optimization tool to do some advanced biquad filters for each tower.


Hi Chris,
I’m a little off subject here but had a speaker question. I have a pair of custom JBL speakers I built myself. They have a 15 inch pro driver and a 4 inch compression driver on a small horn. The crossover is a rebuilt LX5 passive unit that has been rebuilt, new caps and resisters but old coils. I have a DBX Driverack 2 that I can use as a crossover. I’m powering with a pair of M700’s. I’m thinking of using two S300’s to biamp vertically. Do you think this is a good idea? Any thoughts?

Well, why don’t we start a new thread? This is the classic active versus passive question.,

Horn: What horn are you using. I’d try to put that JBL on a modern waveguide that is close to the size of the woofer itself. I can make a few recommendations.

Passive crossover:
Get a measurement mic (about $100) and impendence testing jig (about $110).

learn about speaker measurements (gated + close miking/ground plane), passive crossover design with free tools like vituixcad or Xsim. I’m sure that the crossover could be improved from what you have (as it was designed for another system)

alternately, use your driverack and some EQ and be off to the races.

The M700 sound noticeably better than the S300 and a high efficiency compression driver is more sensitive to noise than just about anything else.

The third option would be to use something like the minidsp SHD, in place of the driverack, as it can do the active crossover stuff and has an integrated measurement/room correction solution with dirac live that is very cool. You’d need to change the target curve of the correction a bit (being that you’re using horns and typically want a -1-1.5 dB per octave response above 1 khz.

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Thanks Chris for the info.
I guess if I were to bi-amp, I would use two sets of M700. I like the sound I’m getting after eliminating the tweeter and the high frequency crossover. The mid range driver is now running all the way out, much better to my ears. The diaphragm is beryllium so it does pretty well at higher frequencies. The horn is a JBL HL93 out of a S8R system so it’s only about four inches long and has a lens at the opening. The balance is not bad. I just thought eliminating another crossover might smooth out the sound a little more.
Thanks, Roger

Did you swap in a truextent diaphragm? I would imagine this would sound really and it wouldn’t be necessary/desirable to have an additional tweeter.

I’m not that familiar with that series of lenses/horns from JBL, though I know that it’s a classic augsberger design from the 60’s.

However, I would probably be interested in a more modern profile and better directivity match with the 15". There are relatively few 1.4"/2" throat waveguides available though.

My coworker recently bought some eminence N314X textreme drivers and is doing a 15’ 2-way with them with some large waveguides and I’ll let you know how it goes.

There is a misconception that a passive crossover is going to be worse than active and that definitively isn’t always the case in home hifi. A well designed passive network may be better actually better than an active setup (because of additional A/D D/A conversion, noise floor (with a very high sensitivity driver like a compression driver) etc.

Either is going to take at least a basic measurement setup to get right, the cost of which is way lower than the components that you’re talking about, so that would be one of my first recommendations.


I did install truextent diaphragms. I’m interested in the newer wave guides but I would be worried that the output of the mid-range would be to loud. I could add resistance in the crossover if that would help. Here are some pictures, Roger

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I’ve been using minDSP 2x4 Balanced as well on my Bose 901 Series 1 & 2 Speakers, the Woofers, on my Open Baffle Frankenstein’s and on my friends KEF R3 Woofer’s just for a 60Hz null in my room (it’s cheating but it works).

Hope to come up there and visit you Guys again once it’s safe to.


It’s not that the output of the midrange would be louder, it’s that a compression driver on a modern constant directivity horn isn’t flat (it falls at about ~6 db per octave or so about 4khz) and so most of the “crossover” is contouring/flattening the response of the tweeter etc.

This is why something like an active system the minidsp SHD / dirac system or a DEQX may be worthwhile, as it can handle the driver response correction for you and has measurement system build-in.

However, this is still kind of an advanced project because you’re kind of engineering the speaker to a degree.

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