I have a couple of these waveguides (WG) and the Dayton D250P-8 compression drivers (CD). I first tried a passive crossover at ~1.5kHz to Beyma 15LX60V2. Used the Clio system and MLS measurements. I got the crossover to have a distinct 1.5kHz cancelation with the polarity of one of the drivers switched. So I think the phase at the crossover frequency isnt too bad. But it sounds like a pair of old megaphones. The beymas measure ok, but I dont know how well they actually sound up to 1.5kHz.
I tested a bit more with an old 8" woofer using minidsp for crossover. That sounded a lot better. Not honky, but very laid back. A bit distant even.
So I dont know if the problem is with the WG+CD or the combination of woofer and WG+CD.
One thing I also noticed is that the waveguides I have are quite rough. The first inch or so of the waveguide is not very smooth. It is a bit bumpy. Is this normal? Does anyone have these waveguides and can check? I am a bit worried that I got a bad pair of WGs.
I tested a bit more with an old 8" woofer using minidsp for crossover. That sounded a lot better. Not honky, but very laid back. A bit distant even.
So I dont know if the problem is with the WG+CD or the combination of woofer and WG+CD.
One thing I also noticed is that the waveguides I have are quite rough. The first inch or so of the waveguide is not very smooth. It is a bit bumpy. Is this normal? Does anyone have these waveguides and can check? I am a bit worried that I got a bad pair of WGs.
Are you aware of "CD"(constant directivity) response compensation m. Basically, a compression driver's response falls off with frequency but usual exponential horns beam at high frequency, which kicks up the HF on axis. A waveguide like the QSC doesn't beam, so it leaves the tweeter rolled off 10dB or so. You need a network to flatten it.
The waveguide in the center? It's literally the best measuring waveguide I've ever seen. On mine the throat is a *perfect* match to the compression driver. It was designed to be used with Celestion's neodymium compression driver. (Which bolts right on.)
But it should work fine with anyone's compression driver.
I believe Parts Express sells a clone of it, from Selenium IIRC
Here's the one I mentioned, it's a clone of the QSC:
PRV Audio WG35-25-B 1" 90 x 60 ABS Waveguide 2-Bolt
I thought it was Selenium, but it's not, it's PRV. (I get those Brazilian companies mixed up lol)
I wish I had both of them here right now. While the PRV is clearly a clone, it's much much heavier than the QSC. I can't recall if the throat is a perfect fit.
By the way, this is a SCREAMING deal. It's a good deal for $50, but for ten bucks, this is awesome.
Agreed. I got a couple of them just-for-the-hell-of-it, and they seem to work nicely. They really seem to like the new Tympany compression driver, too. I'd be hesitant to do any new publishable designs because of its discontinued status, but for some one-off designs it would be very hard to beat. I even considered making a wooden horn extender to use it as the basis of a big Synergy horn, but not if it isn't going to be available anymore.
@bwaslo
Yep, this is how I have the response setup on the 8" +1" that are used with the Beyma 15" now. It works better with falling treble in a speaker that is played loud at home in my opinion.
@Bateman
Yes, the middle one. It does have perfect directivity when I measure it too. But it is also a bit rough in the response and sounds honky.
I expected the waveguide to have something like 6-7degrees entrance angle, but mine have 20-30. There is no adaption to the CD what I can see.
Are yours also bumpy in the first inch of the throat?
Yep, this is how I have the response setup on the 8" +1" that are used with the Beyma 15" now. It works better with falling treble in a speaker that is played loud at home in my opinion.
@Bateman
Yes, the middle one. It does have perfect directivity when I measure it too. But it is also a bit rough in the response and sounds honky.
I expected the waveguide to have something like 6-7degrees entrance angle, but mine have 20-30. There is no adaption to the CD what I can see.
Are yours also bumpy in the first inch of the throat?
I suspect the honkyness is because it is an exponential horn unlike the QSC CD horn. With that horn, the eWave crossover might not work as well so that would have to be addressed. Good looking horn though.
It's not an exponential horn... it's a CD waveguide. Very different. Honkiness may be due to too-high levels or too-shallow slope or some combination of the two. If possible, adding absorptive or profile-continuing edge roundovers would help mitigate the termination, particularly on the vertical with its smaller dimensions.
Not familiar with the performance of the daytons- presumably they're not the issue, but they might be.
Not familiar with the performance of the daytons- presumably they're not the issue, but they might be.
Still no one has any comments on the rough +-1mm bumps in the first inch of the throat of the waveguide? This would seem like very bad in a waveguide to me.
1mm is about 6 hundredths of a wavelength at 20kHz, so it doesn't seem like it could make a lot of difference. But maybe Earl Geddes is reading and might comment, this is more his area of specialization.
Take a pic. My QSCs are perfectly smooth. My PRVs are a clone, but the mold quality isn't quite as good. But it's close.
I wonder if PE got a bad batch?
I've *definitely* seen gaps in some of the Pyle horns, and this will absolutely ruin the response. The gap creates diffraction and reflection in the throat, basically the wavefront gets ruined in the first 2" of the horn, and there's nothing you can do to fix it electronically. The solution is to use putty to smooth out the throat, but it's annoying to have to put in the work. Particularly when you're sloppy like me. (Not all the Pyle horns are like this; the PH612s are awesome.)
Thinking about this, a 1mm overlap represents more than a sixth of the area of the remaining 23.4mm diameter opening. Seeing as it is small vs wavefront, it might excite a HOM or two.
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OP, you're not doing this by ear are you?
It's basically impossible to get flat response from a compression driver and a waveguide without a microphone. Besides the falling response of the waveguide, there is also the significant pathlength difference which can create a peak or a null when you add the woofer into the mix.
I am using MLS measurements with microphones at 0 and 45degrees horizontal from the speaker axis. 3m to any surface so I can measure down to 100Hz. Have not done any vertical measurements though.
The measured response is not as smooth as what I have seen here on diyaudio and other places. And I dont mean smoothing here, it looks like there is a bit of resonance going on in the waveguide.
I like to measure speakers to have a starting point. I have only worked with tuning/developing speakers for a year, but what I have learned is that a speaker can have a great frequency response and dispersion and still sound terrible.
I think frangus is on to something. It is probably the woofer that is the main problem.
One big difference between the 15" and 8" test is the passive vs active filter. But I have heard some questionable crossovers, and this was much worse.
I will test with a known good midrange and see if I can make the waveguide sing...
Thanks for the advice!
The measured response is not as smooth as what I have seen here on diyaudio and other places. And I dont mean smoothing here, it looks like there is a bit of resonance going on in the waveguide.
I like to measure speakers to have a starting point. I have only worked with tuning/developing speakers for a year, but what I have learned is that a speaker can have a great frequency response and dispersion and still sound terrible.
I think frangus is on to something. It is probably the woofer that is the main problem.
One big difference between the 15" and 8" test is the passive vs active filter. But I have heard some questionable crossovers, and this was much worse.
I will test with a known good midrange and see if I can make the waveguide sing...
Thanks for the advice!