LR2 design for the Usher 8945P and 810921 from Jay Kim

[Laurence Platt]

This project is based on Jay Kim’s design for the Usher 8945P woofer with the Peerless 810921-HDS tweeter. Jay's original design used an LR4 crossover. Jay suggested that I may like to try his latest design which is based on a LR2 design with a ladder delay circuit to align the tweeter and woofer. Jay is planning to publish his latest LR2 design soon. Please see Jay’s web site at: http://www.geocities.com/woove99/Spkrbldg/
I used the PE 302-743 0.75ft3 curved enclosure, with this size enclosure Jay’s design is a very capable full range design. Enclosure tuning is set low and lean at Fb of 35hz, using the Precision Port (PE# 268-348) cut to a final length of 7.5" including flare. The port is a very tight fit in the rear panel of the curved enclosure. The largest flange from the port is removed to fit through the lower internal brace hole of the enclosure
Three different Sonic Barrier thicknesses have been used for internal damping: 260-520 ½” sonic barrier on front sides. 260-525 1” sonic barrier on rear sides. 260-535 1.25” sonic barrier on the rear, top and bottom. I have used the low and lean bass response which for my room provide clean bass with no boom or bloat.
The RTA image is from a the Behringer ULTRA CURVE DSP8024, mic at 24" on tweeter axis, in listening room, each RTA step is 0.5db this is an un-equalized inverted RTA.
I have been listening for several weeks now and find these speakers low distortion and non fatiguing.

[jkim]

Re: LR2 design for the Usher 8945P and 810921 from Jay Kim

Laurence, thanks for sharing your build here. It may not be a fact to generalize, but with this driver combination, I do hear improvement of the LR2 crossover over the LR4 although their on-axis responses are nearly identical. That's why I decided to update my website.

[Laurence Platt]

Re: LR2 design for the Usher 8945P and 810921 from Jay Kim

I have added two more pictures.
1/The rear view showing the port.
2/ inside of enclosure
Laurence

[zach_t]

Re: LR2 design for the Usher 8945P and 810921 from Jay Kim

Nice work, and excellent looking project. Those curved cabinets are sweet. I like your stands also.

[rory57]

Re: LR2 design for the Usher 8945P and 810921 from Jay Kim

That looks like a nice piece of work. Ever considered a pentagonal cross section?

[Laurence Platt]

Re: LR2 design for the Usher 8945P and 810921 from Jay Kim

Hi Rory 57
I was wondering about putting them into a cardboard tube! Just happen to have one around from my Ted Jordan days!
The trouble with the pentagons is the difficulty of making the angle correct!
The PE enclosure sure saves a lot of time and frustration.
All the best
Laurence

[240sxguy]

I know this is super old, but does someone still have Jay Kim's documents for this build? I built a pair YEARS ago and wanted to revisit them, as they've been shelved for awhile after a move. I printed out the stuff from the geocities site years ago but lost it of course!

[steveslagle]

Hi 240sxguy,

I tired to paste the LR2 information below, but the schematic and graphs won't paste.
I a word document of the original write-up (LR4) and the LR2 note pasted. I am working this weekend, but could do an message attachment too you on my Monday = your Sunday. (I moved from US to New Zealand, so most of a day ahead.)

Steve Slagle


From J Kim old site:

New Crossover:
I have been working on my LR4 crossover to fix some of the flaws, but I also decided to try a LR2 configuration. The results are interesting. Once the drivers were made to hit the LR2 targets the phase was not tracking well at all with the tweeter polarity reversed (as it should be in a LR2). Switching the tweeter back to positive polarity got the phases closer, but would still have required a very asymmetrical filter to align the phases with any accuracy and they only tracked for a few hundred Hz. So I chose to use a ladder delay network to help align the phases. It is a lot of fiddling, but I think it came out quite well.


(This was the response graphs, but won't paste)


Crossover Info

​
(This was the schematic)


LR2 @ 2200
​

[dld]

I would love copy of the documents too. I built these years ago and would like to them together again to see if my current setup compares.

[steveslagle]

Hello All,

I have the info, but the forum won't let me post the schematic or frequency response.
I may need emails to send this to you.

Cheers,
Steve

[dld]

Steve sent you a pm with my email.
thanks

[billfitzmaurice]

I have the info, but the forum won't let me post the schematic or frequency response.

Upload them as images.

[dld]

I think I found it!

[steveslagle]

Hi did,

I did just send a word document with the 2nd order schematic and the 2 graphs Jkim included. The full original write up of the 4th order was included as well.
Sorry, I am not tech savvy enough to figure out how to convert my document graphs to images to upload.
The image you posted is not the 2nd order crossover I saved from Jkim's site a few years ago.

Hope you get my email and the document.

Cheers,
Steve

[billfitzmaurice]

Take a screen shot, paste that into your photo program, save it as a jpg.

[Chris Roemer]

Like Bill says,

Take a screen shot (by pressing the "PrtScr" key near the top right of your keyboard), paste that (from your "clipboard") into your photo program (like (MS)"Paint"), and save it as a jpg.