Flex Your PCD Mettle:

[Zilch]

Re: Flex Your PCD Mettle:

I have no clue where the acoustic center of a differential-drive woofer might actually be, but it looks like we're in the realm. Flush mounted, the woofer would be about 1/4" farther back relative to the compression driver:

http://www.audioheritage.org/vbulletin/showthread.php?11345-2262H

[Zilch]

Re: Flex Your PCD Mettle:

Driver responses:




First attempt:

[Zilch]

Re: Flex Your PCD Mettle:

C/C = 10.5", woofer pistion 10", tweeter 1", mic @ 44". FRDs include minimum phase and are measured on the forward vertical axis midway between drivers.

The files:

[Pete Schumacher]

Re: Flex Your PCD Mettle:

The files:

What are the X, Y, and Z coordinates?

Ahh, I see them now. Thanks!!

[Zilch]

Re: Flex Your PCD Mettle:

What are the X, Y, and Z coordinates?

X = 0,0 Y = 0.133, -0.133, and I presently have Z = -0.130, 0. Note, I just changed the tweeter diameter to 1.5", the throat diameter of both compression driver and waveguide. I'll be reposting the measured crossover response, as the L-pad was set to 10:00 [Done]. Data files are correct at 1:00.

Using the square format of this PT waveguide, JBL crosses the system 4th order at 1.4 kHz for a max continuous rating of 123 dB and 95 dB/W:

http://www.jblproservice.com/pdf/AE%20Series/AM7212,95-WH.pdf

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Woofer: 1mH, .2 Ohm ; 18uF

Tweeter: 4.7 Ohm in series with 1.8uF; shunt .35mH 20ga; 15uf to tweeter + polarity.

Pushing these to a lower XO point requires a really funky transfer function on the tweeter.

[Zilch]

Re: Flex Your PCD Mettle:

CLIO says with tweeter polarity inverted, the forward axis is at +3.25°, and acoustic crossover at 2.192 kHz:



I'll run the polars using this.

[Gonna listen a bit first, tho.... ;) ]

[Skywave-Rider]

Re: Flex Your PCD Mettle:

Holy sh*#!

[Pete Schumacher]

Re: Flex Your PCD Mettle:

That really is a nice waveguide/tweeter combo.

And there is ZERO baffle step compensation in this XO.

[Mayhem13]

Re: Flex Your PCD Mettle:

That really is a nice waveguide/tweeter combo.

And there is ZERO baffle step compensation in this XO.

Given the cost of the components....it better be!

[Zilch]

Re: Flex Your PCD Mettle:

That really is a nice waveguide/tweeter combo.

And there is ZERO baffle step compensation in this XO.

Not a lot of fiction in this woofer:

http://www.audioheritage.org/vbulletin/showthread.php?11345-2262H

Holy sh*#!

Yah, it don't get much sweeter, but we're going there next. ;)

[I'm gettin' to listen to it, Heh! ]

O.K., it's instructive -- a 12" woofer cannot hold 90° beamwidth up to this crossover frequency, its dispersion begins collapsing at 10° off axis -- we gotta slide that down if it's going to mate with and transition to this waveguide seamlessly:

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Not a lot of fiction in this woofer:

http://www.audioheritage.org/vbulletin/showthread.php?11345-2262H

Yah, it don't get much sweeter, but we're going there next. ;)

[I'm gettin' to listen to it, Heh! ]

O.K., it's instructive -- a 12" woofer cannot hold 90° beamwidth up to this crossover frequency, its dispersion begins collapsing at 10° off axis -- we gotta slide that down if it's going to mate with and transition to this waveguide seamlessly:

OK, how's this:

Woofer: 1.2mH, .2 Ohm ; 22uf shunt ; 1mH, .2 Ohm ; zobel 15uF, 8 Ohm

Tweeter: 1.5uF ; 1.2mH .2 Ohm ; 10uF in series with 3.3 Ohm to tweeter.

[Zilch]

Re: Flex Your PCD Mettle:



I've never seen system minimum phase track 0° so nicely as this; can y'all say "Coherent?" Drivers both in positive polarity, the forward axis is up at +14°, though, 5.75" above waveguide center at 44" mic distance.

Third order like this, it may be easy to pull that down in PCD; I'll load it up....

[Pete Schumacher]

Re: Flex Your PCD Mettle:

I've never seen system minimum phase track 0° so nicely as this; can y'all say "Coherent?" Drivers both in positive polarity, the forward axis is up at +14°, though, 5.75" above waveguide center at 44" mic distance.

Third order like this, it may be easy to pull that down in PCD; I'll load it up....

I can see why the axis is angled up so much since the tweeter acoustic center is quite a bit behind the woofer. This monitor would be perfect sitting on the floor, where BSC isn't required. The fact that the axis is angled up 14 deg makes that an attractive placement option.

[Zilch]

Re: Flex Your PCD Mettle:

Surprisingly so. It's been sitting at -127mm pretty consistently here.

We could rear-mount the woofer as we did with others here, but it's a pretty deep form factor for that.

I'm succeeding in moving it down, but it's starting to look messy.

Mixed orders, maybe; we want the woofer to lag? :rolleyes:

Edit: Let's presume JBL knows how to run this woofer. Here's the AM7212 4th order lowpass:

1.3mH/33uf, 1.3mH/27uF; 4.0mH/15uF/17R5 series notch:




Footnote: Problem with +14° is the waveguide shuts down the vertical dispersion at 20° - 25°.... :(