A 1" compression driver that can play low / mate with a 15" ?

[billfitzmaurice]

Re: A 1" compression driver that can play low / mate with a 15" ?

Looks OK to me. 5 ohms at 20kHz isn't a concern, but you do want to be sure it doesn't drop much lower above that.

[Eigenmind]

Re: A 1" compression driver that can play low / mate with a 15" ?

Thanks for having a look, guys.

I take it you're worried about the 5 ohm at 20k (and falling for a short while above)? A small series inductor on the tweeter might be helpful, both to suppress the 20k peak and to boost that HF impedance slightly, some amps don't like low impedance at HF because it can mess with feedback or modulation loops if the design isn't solid. (the inductor will require some re-tuning of the other components, most likely) I also might do some additional shaping to suppress that 6k bump- I suspect this design will sound pretty hot if it's left in.

I agree with you about the 6kHz hump being a potential hot spot. The problem I'm having now is that I've all but run out of PCB space for the crossover - I'm already having to populate the rear of the board with the inductors. Since this is a retrofit job, I'd like to stick with the original terminal cup and PCB size and just etch new 4"x6" boards for the speakers.

What I've done with this next revision is tweaked the Lpad resistor values a little to bring the whole HF response down about 1~1.5dB. I know this isn't much, but I'm trying to bring the peak more inline with the response at lower frequencies. I know psychoacoustic-wise, we are more sensitive to an abundance of one frequency than the absence of it. I think its better to have a slight hole at 4kHz.

As for the 20kHz peak, I'm not too concerned about it. I don't know how many people can hear that high, and the peak diminishes off axis. Again - PCB space is a limitation!

Nice job working with what you've got there.

Thanks!

Looks OK to me. 5 ohms at 20kHz isn't a concern, but you do want to be sure it doesn't drop much lower above that.

I've changed the topology for the tank circuit in a way that I am pleased with. I have replaced the parallel RC with the series L with a series arrangement with the shunt C. This achieves a deeper null and eliminates the need for a series R which allows it to fit on the board. More importantly, the impedance is much better controlled and is 8ohm at 20kHz and flattening. This looks to be one of those rare win-win engineering decisions!

Let me know what you think!

Thanks guys for the feedback.

[Eigenmind]

Re: A 1" compression driver that can play low / mate with a 15" ?

Well, I'd like to order the parts for this project soon so they can ship on Monday.

So if anybody knows any reason why these two transducers should not be wed in holy crossover, speak now or forever hold your peace. :D

[Cuppa Joe]

Re: A 1" compression driver that can play low / mate with a 15" ?

You may now kiss the speaker....

[badman]

Re: A 1" compression driver that can play low / mate with a 15" ?

Good call dropping the overall HF if the additional complexity of another notch is a nonstarter. Not thrilled with the 20k peak but it'll be fine- many listeners may just call it "detailed" or "airy"

Looks really solid for the retrofit.

[Eigenmind]

Re: A 1" compression driver that can play low / mate with a 15" ?

Well, the project is coming along nicely. Got my parts in and etched the boards. As you can see, I'm reusing the original connectors. I must have gotten something right because everything is lining up with no problem!

If only every project could go that smoothly...

[Eigenmind]

Re: A 1" compression driver that can play low / mate with a 15" ?

The crossovers are assembled and installed in the speakers. I was able to listen to each one in mono to check that everything is wired correctly and they are certainly a huge step up from the old setup. Soon I'm going to set them up in stereo and have a good listening session - probably from 30 yards away!

Thanks to the folks who chimed in and helped me make some decisions! If I get a chance to measure them before it gets too cold, I will post the results.

Regards,
Dan