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Multi-Way Conventional loudspeakers with crossovers

Yet another query re TMM vs.MTM (using DEQX)
Yet another query re TMM vs.MTM (using DEQX)
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Old 25th February 2014, 02:58 AM   #21
DEQXter is offline DEQXter  United States
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frangus,

Thanks for reopening the thread--it has given be an idea. Basically I think Jim is right and I appreciate his comments on the DEQX, but it occurs to me now that there may just be a work around.

If you were to try this as a three way using the DEQX in that mode Jim is absolutely right--it won't allow any overlap between bands. But here is how I think it might be done.

Here is the overall picture: we are going to run he DEQX in two way mode with stereo subs. The two ways will go to the extended range woofer and tweeter just like any two way, but the sub outs will be directed to the 0.5 woofer. In this mode the DEQX allows overlapping the sub and main outs and also allows the use of asymmetric filters.

So lets say you want to use it in a conventional 2.5 with the extra woof providing baffle step compensation and improved LF dynamics. One might set the woofer limits with the HF XO set for say 250 Hz with a 24dB/octave slope. The type of filter could be Butterworth, L-R, or linear phase (tho I think the delays would become problematic with the linear phase XO and likely overkill in this context in any event).

Next you would configure the full woofer and tweet just as you would do normally, using correction filters and measuring at a meter or whatever. Once the two ways are dialed in to your satisfaction I would engage the subwoofer while the DEQX is hooked to your laptop. I would then use the LF output levels and parametric EQ at that point to tune the low freq by ear. Alternatively you could engage the room measurement option and dial in the "sub" outputs that way.

What you will lose is the option of using a true sub or at least controlling a sub with the DEQX--not that big a deal IMO with so many good atand alone DSP sub options these days. Also notice that while you could "correct" the 0.5 output with the DEQX by measuring at say 1 to 6 inches, this will be w/o the output of it's brother. I don't see a downside to doing this as one flat woofer is better than none and the combined output can be dealt with as above in any case.

The real question is: would it be worth it? With all due respect to Mr. Griffin whose work I greatly admire, a definite maybe. This is based on my experiences using the DEQX with the MTM project that got this thread started. I'll detail that in a separate post as this is long enuf already, but as good as it is, I have some lingering issues with my rig that I can't seem to correct and makes me want to give the above method a try when I can corral a little free time.

Last edited by DEQXter; 25th February 2014 at 03:20 AM. Reason: test
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Old 25th February 2014, 03:08 AM   #22
frangus is offline frangus  Australia
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Quote:
Originally Posted by Jim Griffin View Post
I don't think that the DEQX has that configuration as one of its capabilities. Usually a 2.5 way configuration is a passive crossover artifact that uses an inductor to achieve a 6 dB per octave slope on one of the two mid-range drivers that would otherwise cover the same frequency band. Essentially you can adapt this arrangement to achieve 6 dB baffle step compensation.

With its ability to calibrate amplitude, phase and time you have considerable capability built-in to the DEQX unit. This includes equalization and high order linear phase crossover slope capabilities, so the DEQX takes compensation to a new level. Typical slopes are 48 dB/octave or greater. I do not believe that the DEQX has the capability to separately calibrate over two overlapped frequency bands. I would just use a two-way DEQX configuration. You can set the amplitude EQ limits range to easily adjust the amplitude response so that you attain flat amplitude response so that a 2.5 way configuration is not needed. Bottom line is that you have race horse capable DSP so don't limit it to solving donkey era problems.
I am considering 2.5 way for the benefits of higher efficiency and Sd.

I believe I could use the sub integration feature to allow overlap of the frequency bands before the "subwoofer" cut-off at say 400hz.

Hoping someone can confirm - my DEQX is still in the box and I wont get a chance to play with it until we move into our new place.
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Old 25th February 2014, 03:59 AM   #23
DEQXter is offline DEQXter  United States
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So the saga of the MTM vs MMT question continues. Here is my experience.

To cut to the chase: For various reasons, I ended up going MTM--not the least of which was that the Dayton 1 cube enclosures I bought had a big brace running crosswise down the middle which I didn't want to remove. Am I happy? Sometimes ecstatic other times miffed which may have nothing at all to do with the MTM but has lopped some of my confidence away and given me some major appreciation for the less obvious aspects of speaker design.

What I used: two Usher 8948a 7" paper/fiber woofers, SB acoustics Sartori tweeters, 6 channels of decent amplification--each of the 4 woofer gets its own 150 W, the tweeters 100/side. No internal XO's. DEQX used in biamped mode with optional mono subwoofer (in this case a Dayton 18" HO woofer driven with 2KW Classe monoblock). The woofers share the 1.0 cubic foot cabinet which results in something like a 0.55 Q sealed alignment. (Here the port would have been problematic plus I have a fair amount of headroom and adding EQ is no problem). The tweeters are inboard of center by about 1/2 the available distance and the C2C distance between the woofers almost 12" exactly.

So how does it sound: very good dynamics giving the small moving coil drivers and plays as loud as I care to listen which on occasion is very dmn loud--my younger and better hearing friends run for cover, and provides all the inner and outer detail I crave and have come to expect having owned a number of planar driver systems before this one. In fact it is overall the best system I have owned and compares favorably to most anything I have heard that costs say less than a new small car. The fly in the ointment is that it has FR issues that on some material are disconcerting if not an outright embarrassment. They are hard to characterize as I don't have a decent rig with which to measure,;What I see in the uncorrected swept tone FR curves is a lot of ripple between 1 and 3K. Some of this was predicted by the diffraction software I used and it may be that the cabs are just not up to the overall caliber of the system, but I hate to blame them. What was unexpected are the woofer passband FR irregularities which prior to correction are like +/- 5 dB (ouch!!). These measurements were made at both 1 and 2 meters midline with the mic centered between the woofs. What I hear are timbral errors here and there--a tad bright/thin occasionally even hollow but only on some material and nothing I can EQ out--not that I have much skill in this dept. I have always found parametric EQ difficult except in the bass.

Anyway at first I thought it was just combing but does this make sense at those distances, especially since the mic is equidistant from both. I must say I like the MTM as for the first time I'm living with hardwood floors and I don't have any issues with floor bounce that I detect--or at least not like what I've heard with other systems on hardwood.

Anyway all of this has me wondering is there might be something about DEQX and MTM that's non-sympatico, but for whatever reason got great results in the past with big B&G planars where I would think the DEQX would be completely miffed. Any insights appreciated.
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Old 25th February 2014, 04:04 AM   #24
DEQXter is offline DEQXter  United States
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Quote:
Originally Posted by frangus View Post
I am considering 2.5 way for the benefits of higher efficiency and Sd.

I believe I could use the sub integration feature to allow overlap of the frequency bands before the "subwoofer" cut-off at say 400hz.

Hoping someone can confirm - my DEQX is still in the box and I wont get a chance to play with it until we move into our new place.
Yes. Please see my detailed post from earlier today in case you missed it. One wrinkle that you may wish to avoid is having much overlap between the corrected full woof and the 1/2 woof. My notion is that the freq correctionwindow that is available to you with typical speakers and ceiling dimensions usually is good to about 500hz lower limit, Big room, tall ceiling, all the furniture out of the way might get down to 350,, Assuming the software is doing its job, you should have close to flat response transducer to the lower limit, below which a bit of a crap shoot the driver is in its own. My point I that then overlapping the other driver well out beyond that may throw a fly in the ointment, and unless you really need the augmented output at 600HZ I might be tempted to keep it out--0.5 be almost like a separate driver and may spoil the soup. Of course in the end I'd try both ways and see what sounds best. Honestly 'm pretty psyched about tying some of this out.

Last edited by DEQXter; 25th February 2014 at 04:30 AM.
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Old 25th February 2014, 04:29 AM   #25
dumptruck is offline dumptruck  United States
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So, basically you're saying "I set up this active speaker, it seems to have some problems, I can't really measure them, any insights"? To this, I say "no".
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Old 25th February 2014, 12:43 PM   #26
DEQXter is offline DEQXter  United States
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Yea, I suppose so.
And you're right not much to go on short of investing in some decent software and making the measurements. Just wondering in the meantime if anyone has done an MTM with DEQX I suppose, and whether they ran into any unexpected hiccups. Hopefully trying it as a 2.5 may lead to some insights as I have no doubts whatsoever about the quality of these two drivers I used. And the speakers are pretty phenomenal 90% of the time--just trying to get the voicing just so. Never faced this in the past with the DEQX.
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Old 25th February 2014, 01:21 PM   #27
DEQXter is offline DEQXter  United States
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Quote:
Originally Posted by frangus View Post
I am considering 2.5 way for the benefits of higher efficiency and Sd.

I believe I could use the sub integration feature to allow overlap of the frequency bands before the "subwoofer" cut-off at say 400hz.

Hoping someone can confirm - my DEQX is still in the box and I wont get a chance to play with it until we move into our new place.
Frangus,
A couple of thoughts I forgot to include and which may cause issues--probably minor--if the subwoofers share the same volume with the woofers the loading will obviously be affected and if turned off will be driven antiphase from the rear wave of the active woofer; I would be inclined to leave the 0.5 out of the enclosure until you have done the two way f that's the case. Also I said HF XO for the 0.5 when I meant LF. Finally I have an old DEQX--the PDP2.6 and the subwoofer integration feature you mention is pretty much all done by hand--newer units may allow you to automate the process.???
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Old 25th February 2014, 04:00 PM   #28
dumptruck is offline dumptruck  United States
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ARTA, REW, HolmImpulse, all take measurements for $0 investment, and DEQX units come with a mic and calibration file (or is that only newer ones?), so all you need is a soundcard/interface with an appropriate mic pre in it. Or maybe you can use the DEQX for that purpose - I do not know.
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Old 26th February 2014, 01:41 AM   #29
DEQXter is offline DEQXter  United States
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Dumptruck yes I have a mike and cal file. Was unaware of these products. Many thx, I will look into it.
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