jwgorman

I started another project that I'll never finish. These have been used for living room listening but are as new. I have a pair of 3015LF_4s for sale for $320 for the pair I also have a pair of HF1440 1.4" Compression drivers for sale for $400 for the pair I'd ship everything for $25 to lower 48.

Sorry man, I do not know. I paid a cabinet maker to make these.

I think I am going to build a smaller box, built around a 12” that can go up to 1.5khz without a crazy resonance peak and the ESS AMT1 driver.

Thanks. Yes, I have gotten a lot of enjoyment from them. Thanks for pointing out my 2.25” comment. The front of the motorboard is 1.5”, where the t-nuts mount for the woofer is 2.25”. I’ve edited that part.

In 2019 I had a local cabinet maker build me some Cornwall/Altec 19 inspired two ways from 3/4” baltic birch. He even used baltic birch for bracing and at my request, we ended up making the motorboard 1.5” thick (2.25” where the t-nuts for the woofer mount) for no good reason. These speakers have provided countless hours of crossover and driver experimentation. I have left them configured with 15PR400-4s and HF-146 on ZXPC horns. They are crossed at 700HZ and sound very balanced. I’m sure a digital active crossover would have been much easier to work out but clearly I like old school stuff. The crossover was by far the most frustrating part of working through this design and I don’t claim it’s perfect. They are very dynamic/efficient and more polite than my Cornwall IIs were but still posses a front and center presentation. Alas I think I am ready to move to a smaller box for continued scientific experiments. These are 23.5x24x43.5” and guessing they are roughly 150 pounds each! You can experiment to your heart’s content or leave them as they are. I am near Cedar Rapids Iowa. $2000

Ha. Oh man. Good old days 😀

I think that would probably be worth a try. I have a luxman 550AXII and it got along well with lascalas stuffed into corners. My buddy has a Schitt 20 watt amp and it drives his 96db/w/m speakers to very high spls and sounds good.

I need to keep up. I still look at Fortes as new fangled. Looks like JBL does use a selector that allows switching in various cap values.

Sure. I was talking about the cap in parallel with the series resistor of the attention circuit.

Thanks. I was actually aware of this. It makes sense that, given the correct capacitance, that would help bypass hf attenuation. Do you think it could be as simple as a bypass cap in the attenuation circuit? Or maybe several caps connected to the hf and uhf boost knobs on the front panel?

Ha.I sure would like to see the uhf circuit. And the hf circuit.

That good to know. I’m very curious as to the passive correction done in the 4367. From about 8db down at 10k to essentially flat. I have no doubt Roy has this figured out but I would like to know how.

Klipsch’s networks (the classics that have schematics on this forum) do pass specific frequencies to drivers, and by increasing the slope of the crossover they can effect, to a limited extent, how much high treble comes out of a K77 (for example) but beyond that there is no eq. If you look at the raw frequency response of the JBL driver/horn in the white paper I linked to they have provided considerable eq to get their driver/horn flat.

Agreed! Any idea how they passively eq’d the compression driver/horn?

I found a JBL 4367 white paper today that has piqued my interest in a couple things. First I should mention that it’s really more of a white paper lite, something the marketing guys worked out with a couple engineers. But it’s still a good read. The first thing that caught my eye was the biased crossover using signal power rather than a battery or external source of power. Not sure I understand how they pull this off. The second thing that looked cool was the passive eq they allude to that corrects the raw frequency response of the driver in the horn. The 4367s use differential drive woofers and some advanced compression drivers. If you have a minute please go check it out https://www.jblsynthesis.com/on/demandware.static/-/Sites-masterCatalog_Harman/default/dwc07f5318/pdfs/JBL Synthesis 4367 White Paper.pdf