OK boys, pick it apart!

[Mark65]

This is the XO I've come up with for the as yet unnamed RS180S-8/XT25TG30-04 project that I'm working on. Cab is going to be a PR alignment, ~33.5 liters, tuned to 34 Hz, modeled F3 ~32Hz.

LR4 slopes at 1800Hz, tanked second order electrical plus a series notch on the woofer, third order electrical plus a series notch to address the impedance spike on the XT25.

The thing that troubles me is the transfer function plot, and the fact that the woofer is showing up in the FR plot up high.










Soooo.....go ahead and give me your thoughts, good, bad or indifferent. I really want this project to be the best that it can be, so any and all opinions are welcome.


TIA,


Mark

[joeybutts]

Re: OK boys, pick it apart!

Amazing!!!!

uhmmmm:rolleyes: I have no idea. Hopefully some one can come in and confirm so I can see some build pics!

Good luck MArk!

[cjd]

Re: OK boys, pick it apart!

You have a 0mH .84ohm inductor? ...

This looks purely simmed?

I know this is weird coming from me, but the parts count vs the results seems high. Sure looks pretty though.

[PWR RYD]

Re: OK boys, pick it apart!

You have a 0mH .84ohm inductor? ...

That's the only way to sim a parallel tank cap across the low pass inductor.

[PWR RYD]

Re: OK boys, pick it apart!

Yeah, the parts count is a little high but.... wow! Fantastic looking FR, phase tracking, reverse null, and power response!!!!! Looks like a full 6 dB of BSC? Did you also sim the baffle diffraction? If so then "Great Shot Man!" I like it! I just purchased 4 of those RS180S-8's for an MTM with the RS28F.

[Brewski]

Re: OK boys, pick it apart!

Mark,

It looks beautiful the only change I might suggest is making it a bottomless notch by taking the .47 resistor out to prevent the bounce back up at 10K+ on the woofer side. Also as you probably already know from prior posts and Wolf's blogs you'll want a resistor after the .20 cap since there isn't a resistor in line with C2.

Take it easy
Jay

[dthomas]

Re: OK boys, pick it apart!

Wow a lot of parts...:o

Way to beat them drivers into submission.

[johnnyrichards]

Re: OK boys, pick it apart!

I have heard from reputable sources that 1800 is probably a little low for the XT25.

I also wonder if the second notch on the woofer is actually necessary - can you not get enough of a tank with just the one?

What did you use for offsets? Driver diameters? Just curious, as I have found playing in simulation land that power response on 4th order LR rarely ends up looking like that. Curious to see how you got there.

The unfiltered tweeter response looks fairly smooth, as well - did you run that one through the RM program? Generally there is a little more uneven response down low - speaking of which, the tweeters low end response needs to be extended instead of flatlining like that. As-is, your phase will not be accurate. In fact, you can see the tweeter phase tailing off at ~200 Hz, same as the point where the response flat lines. It is arguable if this is an audible issue or not, though.

If the offsets are more or less accurate and the FRD files have been cranked through RM than the sim looks good so far and you would be ready to start voicing. Well done!

[[email protected]]

Re: OK boys, pick it apart!

all of the above.
is this with measured response in box? if so, build it. well done.

[bolland83]

Re: OK boys, pick it apart!

Looks like you've been busy. Maybe we can get together when you're ready to make some sawdust, if you haven't already.

[Paul Carmody]

Re: OK boys, pick it apart!

Based on my experience, you might still hear the woofer "hissing" through at 8 KHz where the breakup is coming back. I had this issue when doing 2-ways with the RS180... I was hearing extra sibilance even with the tweeter disconnected. Once i went all the way to 3rd order (w/ tank notch filter), the breakup was down by 50+ dB, and it was no longer audible.

For the sake of experimentation, did you try my woofer filter from the Amiga? If not, feel free.

[Mark65]

Re: OK boys, pick it apart!

Based on my experience, you might still hear the woofer "hissing" through at 8 KHz where the breakup is coming back. I had this issue when doing 2-ways with the RS180... I was hearing extra sibilance even with the tweeter disconnected. Once i went all the way to 3rd order (w/ tank notch filter), the breakup was down by 50+ dB, and it was no longer audible.

For the sake of experimentation, did you try my woofer filter from the Amiga? If not, feel free.

Ok, this is the feedback I was looking for. Thanks to everyone who posted.

I actually was thinking about going third order electrical on the woofer, just to see what might happen. I agree that there are a lot of parts here, and I don't like that, not at all. BUT, I want these to surpass anything that I've done so far, so if throwing parts at it is the way to achieve that, then so be it. Still, if I can lose some of them, and keep things viable, I'm all for it.


Also, both drivers have been run through RM, positioned on the baffle, and I used .025m for the z offset.

I'll be looking at the Amiga xo, if for no other reason than to find out what I'm doing wrong....


Mark

[Mark65]

Re: OK boys, pick it apart!

Looks like you've been busy. Maybe we can get together when you're ready to make some sawdust, if you haven't already.

Absolutely. I'm 100% down with that.


Mark

[cjd]

Re: OK boys, pick it apart!

I don't tend to use PCD for this kind of stuff because I never remember exactly how to get the tool working the way I want - it's just not intuitive, I can't look at the spreadsheet and know what's where. I missed the "before" circuit below that. Sigh.

I was able to attenuate -40dB on breakup with just a 1.5mH+30uF+zobel on the RS180-4 on the surrounds I did for my HT. I often find myself at a 3rd order, or a 2nd order + tank (plain parallel LC no R), with the RS180. I always do the LC *after* a standard intro, which seems to provide better overall shaping for me.

I'm not sure if Paul found those sibilant or not, but he's heard them.

[Wolf]

Re: OK boys, pick it apart!

What's the tweeter Z look like? You're -3dB at 2kHz already, and the notch will help, so you may be okay. I'd still listen for nasality as-is.

Johnny- sometimes a double-notch is warranted. The effect of a resonance or energy storage usually has to be 'shorted out' after the voltage dividing lowpass. (If you want rid of it completely anyway.)

Looks pretty good to start with, Mark!

Later,
Wolf