Flex Your PCD Mettle:

[Zilch]

Re: Flex Your PCD Mettle:

Thanks, Pete!

I'm off to try your woofer notch and maybe tweak the forward axis, if required, then run the polars.

Crossing at 2 kHz is probably going to shorten the forward lobe too much. The QSC 152i and a snugged-up 12" woofer will get a nice +/- 15° (-6 dB) vertical listening window if crossed closer to 1.5 kHz, a prime objective in these waveguide designs....

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Thanks, Pete!

I'm off to try your woofer notch and maybe tweak the forward axis, if required, then run the polars.

Crossing at 2 kHz is probably going to shorten the forward lobe too much. The QSC 152i and a snugged-up 12" woofer will get a nice +/- 15° (-6 dB) vertical listening window if crossed closer to 1.5 kHz, a prime objective in these waveguide designs....

I'll see if I can pull it lower. The problem is that the tweeter response below 2000 is doing some really funky things. Sure looks almost like baffle diffraction.

I'm going to ignore it for now, and settle for the response anomalies between 1 and 2KHz, figuring that they'll smooth out with a flush mount waveguide.

[Pete Schumacher]

Re: Flex Your PCD Mettle:

How's this?

[Zilch]

Re: Flex Your PCD Mettle:

There's major overhanging edges in the trap cabs. I've never done the "moving the baffle foward" on those, largely because everything we've built in them sounds good and measures fairly well. The polars on these will show us more of what's going on, now that we know better know how to recognize the issues.

I've ended up with 0.3 mH, 125 uF, and 6 Ohms on the notch.

Woofer diameter 254 mm, tweeter 25.4 mm
y offset w -0.127, t 0.127 (PCD7, now)
z offset w -0.070, t -0.166

I'll confirm the z with another hunt for the maximal inverse notch after some forward axis setting tweaks.

We are mighty close. Your response is flatter; I'm doing it 2 x 2nd order w/inverted HF....

[Pete Schumacher]

Re: Flex Your PCD Mettle:

When I compared the summed response file with the summed response of the two individual drivers in PCD, the response that most closely resembled the "notch" in the summed file was when the woofer was placed 30mm ahead of the tweeter.

[Zilch]

Re: Flex Your PCD Mettle:

Yes. I trust the location of the maximal inverse null once a prototype crossover is built, however. Admittedly, that wanders around a bit with each iteration. It's an extremely sensitive determination; we're talking +/-1 mm on the offsets, typical....

[bwaslo]

Re: Flex Your PCD Mettle:

Looks like quite a setup there. Nice fit for the cabinet, too, all the drivers and box almost look like they were made for each other.

I'd take the baffle forward, though, if only because I think it looks better that way. Really quick and easy to do with a handful of 3/4 x 3/4 square dowels, too.

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Looks like quite a setup there. Nice fit for the cabinet, too, all the drivers and box almost look like they were made for each other.

I'd take the baffle forward, though, if only because I think it looks better that way. Really quick and easy to do with a handful of 3/4 x 3/4 square dowels, too.

You could simply run a router around the baffle edge and get it flush too.

[Zilch]

Re: Flex Your PCD Mettle:

Woofer should be rear-mounted with clamps. Then, once the waveguide is recessed flush, the woofer opening (including the waveguide edge) could be rounded over 3/4".

[Snazzy.... :D ]

Edit: There's reason for the recess, as well:

[Zilch]

eWave SR Directivity:

Horizontal polar response, 0° - 90° in 5° increments:






Horizontal polar map, waterfall, and conventional polar plot:








Insofar as directivity is concerned, I'm not seeing any major anomalies attributable to the 1.25" edge recess.

I DO, however, see 70° - 80° beamwidth (-6 dB) constant directivity in spades....

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Which XO are you using? Those horizontal plots sure look nice. Very consistent.

[donprice]

Re: Flex Your PCD Mettle:

What is the hold up? You have been working on this for almost 24 hours and have yet to post a final x-over design (with part # and costs) or the polars or the nifty waterfalls. What part of instant gratification do you not understand?

I guess we can wait another 24 hours :rolleyes:

Thank you for the schooling!

Well, don't I look like the slow-posting idiot.

[Zilch]

Re: Flex Your PCD Mettle:

Which XO are you using? Those horizontal plots sure look nice. Very consistent.

It's 2 x 2-pole with tank filter on the woofer as you suggested, tweaked a bit. If the vertical polars are good, I'd say it's a wrap.

Well, don't I look like the slow-posting idiot.

:D

[Skywave-Rider]

Re: Flex Your PCD Mettle:

Last edited by donprice; Today at 10:13 PM. Reason: Sarcasm is too slow...

LOL!

[Skywave-Rider]

Re: Flex Your PCD Mettle:

Zilch, is the inverse null at 1589 Hz?
And what is the forward measurement axis you are using?
Is that in-room response for the LF? Must be.
Looks great!