What I built, impressions and solutions?

[IG81]

Adding series R reduces Fb peaking, just not as efficiently as stuffing the vent, not to mention a tonally balanced (maximally flat) system tends to ameliorate minor Fb peaking as long as Fb is low enough and/or room gain doesn't severely under-damp it and why speakers placed in a small room near one or more boundaries need to have a relatively high F3.

With such a long whizzer, it's definitely optimized for PA/car audio.

WRT kneading it, you don't do the whole thing, just the mouth to damp its bell modes. That, or rim it with foam, though finding the right density is a tedious affair, so some folks just coat them with rubber cement, but kneading them works best overall IME.

Right, to have max effectiveness, the phase plug must extend beyond the whizzer to at least its height + its radius *0.613, so if it's 1" high from the pole piece and has a 2" i.d. bell, then the phase plug minimum height = 1 + (1*0.613) = 1.613" with its shape being the inverse of the whizzer's flare as a first approximation to fine tune from there.

The whizzer has horn action along with transmitting the signal through its material, so reducing its height/mouth area raises its cut-off and reduces its directivity, so depending on its FR it could cause an audible notch as well as increasing its polar response down low (in the whizzer's BW), which may/may not be a good thing overall, so without a measured response to make an educated guess as to what to do with it, this one-way tweak may force you to cut it all off and add a tweeter.

GM

Good stuff as always!

If I cannot manage to get a good FR measure using puretones and an SPL meter, I'll definitively leave the whizzer full lenght.

I'll try the edge kneading.

I'll test with my 4.7ohms and parallel them if necessary on one channel only to test lower R.

My phase plugs are a tad shorter than what you instructed, but I still have ~40" of dowel left so no prob if I want to experiment!

Thanks!

 

[GM]

Yes, you got the right Dammar, though if you buy any more, no need for any but the cheapest you can find since it needs to be thinned so much. Use Japan Dryer to make it cure faster.

FWIW, for pipes, horns, I recommend lining walls rather than stuffing.

Use a freeware pink noise generator to do response measurements since it has the same harmonic structure as music, IOW the same
energy per octave (AKA the 1/f noise).

GM

 

[IG81]

Yes, you got the right Dammar, though if you buy any more, no need for any but the cheapest you can find since it needs to be thinned so much. Use Japan Dryer to make it cure faster.

FWIW, for pipes, horns, I recommend lining walls rather than stuffing.

Use a freeware pink noise generator to do response measurements since it has the same harmonic structure as music, IOW the same
energy per octave (AKA the 1/f noise).

GM

The Damar I got was the cheapest in the store!

WRT pink noise, I'd then need a spectrum analyzer to read the response. The sonometer I have access to will just give an instantenous reading. I'll give it a try to see if readings make any sense with pure tones that way.

 

[GM]

OK, then you did good! I didn't notice you're in Canada, so the local prices I have obviously don't apply.

True, but there's freeware ones on the net, so all you need is a mic hook-up to your computer. It won't be any good for accurate measurements down low without calibration, but otherwise should be good enough for near-field (< ~3/16 - 1/4" from whatever point on the driver you want to measure).

GM

 

[IG81]

OK, then you did good! I didn't notice you're in Canada, so the local prices I have obviously don't apply.

True, but there's freeware ones on the net, so all you need is a mic hook-up to your computer. It won't be any good for accurate measurements down low without calibration, but otherwise should be good enough for near-field (< ~3/16 - 1/4" from whatever point on the driver you want to measure).

GM

I also have access to a 100dBSPL sound calibrator, so I could try to perform a basic calibration of the mic perhaps. I could get the mic relatively flat from 125Hz to 2000Hz with this.

IG