Flex Your PCD Mettle:

[Pete Schumacher]

Re: Flex Your PCD Mettle:

The new set of FRDs was taken from a single point in space, at the midpoint between the drivers and on axis horizontally, so the responses would include the relative offsets.

They include minimum phase. I don't know how CLIO calcs that, but I did not alter the time window.

I also provided the same measurement for the two drivers combined, from which the relative offsets may be derived by matching the response with no filters.

I did that, and came up with a crossover having a beautiful response curve and phase behavior. I built it up, measured the response, and it had a perfect inverse notch at the design axis, which I take to mean that the correct offsets should be derived with the HF polarity inverted.... :p

I took those individual curves and applied the offsets based on the PCD summed and measured summed response. I set the woofer forward of the tweeter by 60mm and the woofer .125 meter below center and the tweeter .125 meter above center.

L2 = 4.5mH .3 Ohm
C2 = 12uF

C9 = 5.6uF
R10 = 4.7 Ohm
R16 = 2.7 Ohm

The forward lobe looks very good, especially moving toward and above the tweeter position. the overlay is 45 deg above center point.

[Zilch]

Re: Flex Your PCD Mettle:

Here's the Geddes topology for the equivalent design; we don't know the component values:

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Here's the Geddes topology for the equivalent design; we don't know the component values:

My 5 components looks a little simpler.

[Zilch]

Re: Flex Your PCD Mettle:

L2 = 4.5mH .3 Ohm
C2 = 12uF

C9 = 5.6uF
R10 = 4.7 Ohm
R16 = 2.7 Ohm

Give me a couple of minutes to build it up here.

[Gotta put some shoes on.... :p ]

[Zilch]

Re: Flex Your PCD Mettle:

My 5 components looks a little simpler.

And it is a most EXCELLENT one; the forward axis is right where we want it to be!

I'll run the vertical polar map to verify....

Notes:

1) HF polarity inverted.

2) Red = Zilch's design.

3) Lower L2 to 4.0 mH, maybe?

[Pete Schumacher]

Re: Flex Your PCD Mettle:

And it is a most EXCELLENT one; the forward axis is right where we want it to be!

I'll run the vertical polar map to verify....

Notes:

1) HF polarity inverted.

2) Red = Zilch's design.

3) Lower L2 to 4.0 mH, maybe?

It's easy to play with the main inductor value. Smaller will raise the mid levels a bit (less BSC), so blending the tweeter may be necessary. Tweaking the tweeter level is simply a matter of playing around with the shunt resistor. the benefit of keeping it small means that maintaining a first order response to compliment the waveguide is very easy to do with just a single cap. If you lower the inductor to 4mH, raise the shunt resistor to 3 Ohm, maybe 3.3.

[Zilch]

Re: Flex Your PCD Mettle:

Thank you, Pete; I'm callin' it "Done."

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Thank you, Pete; I'm callin' it "Done."

I am looking forward to your detailed listening impressions and write up on the cabinet construction.

I'm amazed at what 5 components and the right drivers can do.

[Pete Schumacher]

Re: Flex Your PCD Mettle:

Here's the Geddes topology for the equivalent design; we don't know the component values:

And when you say Geddes topology for the equivalent design, do you mean the same drivers and waveguide????

[Zilch]

Re: Flex Your PCD Mettle:

That's the crossover for the Geddes Abbey design, which uses the same B&C DE250-8 compression driver on a 12" round Geddes axisymmetric waveguide with B&C 12DBX100 12" woofer. I'm using the KappaLite 3012LF because it can accept a Q=2 assist at 30 Hz to make extended bass in this small cabinet. Used with sub(s) in HT or for SR, they don't need that, of course....

[Jeff B.]

Re: Flex Your PCD Mettle:

That's the crossover for the Geddes Abbey design, which uses the same B&C DE250-8 compression driver on a 12" round Geddes axisymmetric waveguide with B&C 12DBX100 12" woofer. I'm using the KappaLite 3012LF because it can accept a Q=2 assist at 30 Hz to make extended bass in this small cabinet. Used with sub(s) in HT or for SR, they don't need that, of course....

Geddes sure uses a lot of real estate for a crossover.

[Zilch]

Re: Flex Your PCD Mettle:

I am looking forward to your detailed listening impressions and write up on the cabinet construction.

I'm amazed at what 5 components and the right drivers can do.

The cabs are here:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=245-325

Your crossover just made these slam-dunk simple to build....

[Pete Schumacher]

Re: Flex Your PCD Mettle:

The cabs are here:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=245-325

Your crossover just made these slam-dunk simple to build....

Well how cool is that?

Are you adding internal bracing? Damping material? Owens corning 703, 705?

[Zilch]

Re: Flex Your PCD Mettle:

Well how cool is that?

Are you adding internal bracing? Damping material? Owens corning 703, 705?

They could certainly use a cross brace, tied to the rear panel as well, probably.

I just lined the walls with R-13, which adds up to "heavy fill" by some standards. These probably deserve some attention to details by others. I'm vectored toward getting a second one built and running tomorrow.

There's two 2" x 10" ports cut in the back with elbows. They run up alongside the woofer magnets inside. I think they're 10", anyway; you can see they're tuned ~30 Hz in the impedance plots. They'd fit on the front baffle, probably, but I want to roundover the woofer opening, so it should be mounted with clamps on the rear, probably. I suppose the clamps could be laid out so as not to interfere with front ports in the lower corners.

[Pete Schumacher]

Re: Flex Your PCD Mettle:

They could certainly use a cross brace, tied to the rear panel as well, probably.

I just lined the walls with R-13, which adds up to "heavy fill" by some standards. These probably deserve some attention to details by others. I'm vectored toward getting a second one built and running tomorrow.

There's two 2" x 10" ports cut in the back with elbows. They run up alongside the woofer magnets inside. I think they're 10", anyway; you can see they're tuned ~30 Hz in the impedance plots. They'd fit on the front baffle, probably, but I want to roundover the woofer opening, so it should be mounted with clamps on the rear, probably. I suppose the clamps could be laid out so as not to interfere with front ports in the lower corners.

I wonder if anyone is bringing an Econowave to InDIYana?