Think We May Have a Keeper Here!!!

[Zilch]

Regarding the UHF sensitivity issue, I had to pad the 2402H down 10 dB to get it into the L-Pad adjustment range.

First try at remedy was to connect the HF after the fixed (2.5, 5-Ohm) attenuation in the MF circuit. That only got a couple of dB, though, so I reconfigured the sample per the standard 310x cascaded configuration.

That works very well; the full MF attenuation is also applied to the UHF. Once the MF/UHF balance is established with the UHF L-Pad, then the overall balance is adjusted with the MF control. It's intuitive, and easy to get it all properly balanced. There's still plenty of sensitivity left to overdrive the UHF for "air" or "sizzle," if desired.

I did observe one characteristic which may explain the different performance results Todd and I are obtaining: the 2402 is quite "beamy" in the higher frequencies. The two RTA plots below show the response on-axis versus 30° off-axis.

The difference is substantial (6+ dB). Note that response above 10 kHz falls off decidedly more (2-3X).

"Yeah, but 30° is a LOT, too!"

Well, no. It's the difference between being at 12:00 and 1:00, only, right? So, for comparable measurements, all must be taken precisely on UHF driver axis....

[Zilch]

O.K., so here's the final schematic and a proposed low-cost parts list.

For those who haven't followed this project from the beginning, what's important here is that it's a generic solution to building a DIY 800 Hz MF, 7 or 8 kHz UHF 3-way crossover for a variety of JBL woofers, 16-Ohm compression-driver midranges, and 07x/240x UHF drivers without using tapped inductors (autotransformers).

It is derived from combining N200B (LX200B) and 3105/6 (N7/8000), in cascade. I've tested it with 2235H LF, LE175, LE85 (2420), and 2446J MF, a bunch of different horns/waveguides, and 2402H (075), 2404H-1, 2406H, and 2407H UHF. It may also be suitable for use with 222x woofers.

Connect LF and HF inputs in parallel for single amp, or biamp passive, as shown. For triamp, separate the UHF section (bottom), as well.

Disclaimer: As with all DIY projects, mileage may vary.

[Let us know how it works for you, please, and any suggestions for improvement....]

[toddalin]

Looks good! You left off mention of the six 0.01 mfd by-pass caps.

O.K., so here's the final schematic and a proposed low-cost parts list.

For those who haven't followed this project from the beginning, what's important here is that this is a generic solution to building a DIY 800 Hz MF, 7 or 8 kHz UHF 3-way crossover for a variety of JBL woofers, 16-Ohm compression-driver midrange, and 07x/240x UHF drivers without having to mess with tapped inductors (autotransformers).

It is derived from combining N200B (LX200B) and 3105/6 (N7/8000), in cascade. I've tested it with 2235H LF, LE175, LE85 (2420), and 2446J MF, a bunch of different horns/waveguides, and 2402H (075), 2404H-1, 2406H, and 2407H UHF. It may also be suitable for use with 222x woofers.

Connect LF and HF inputs in parallel for single amp, or biamp passive, as shown. For triamp, separate the UHF section (bottom), as well.

Disclaimer: As with all DIY projects, mileage may vary.

[Let us know how it works for you, please, and any suggestions for improvement....]

[Zilch]

Looks good! You left off mention of the six 0.01 mfd by-pass caps.

Thanks, Todd.

Allegedly, Solens don't need bypass caps, so they're cheaper than Daytons + Thetas. Like you, I'd probably bypass, anyway.

Tomorrow's a holiday, so I get another day to play here.

I'll send your prototype back on Tuesday leaving in the changes I made for you to try. It's easily restored to your original topology, if you decide to do that, tho.

May have to build myself up a pair of these; they seem to work with just about anything here....

[johnaec]

Zilch - your crossover looks great to me - perfect for PA use with 2226H, 2446H/2380A, and 2405H. Or would it need to be modified for the flat-front 2380A constant directivity bi-radial horn?

And no - I haven't forgotten about the cabinet stuff we're planning. I actually finally got the 2214H's I want to work with, for L100T3 components/crossovers in your (what'd you call them - Z1??) special angled cabinets.

John

[Zilch]

Hi, John!

While, in theory, some compensation would be required between 3.5 and 7 kHz, I'm able to dial in 2446J on 2380A with 2402H fairly well (RTA below).

With 2445, the specs say it needs a little help between 800 and 1000 Hz, which can be provided by adjusting the Zobel, depending upon which woofer is used.

http://www.jblpro.com/pages/pub/components/2380a.pdf

Compare to two-way with 3110A results here:

http://audioheritage.org/vbulletin/s...4&postcount=75

Alas, no 2405H here to try.

[We're gonna build both Z1 and Z2 cabinets, remember? ]

[johnaec]

Alas, no 2405H here to try.

I can let you borrow a NIB 2405H if you want to experiment, (don't do it for me - I'm OK with my needs). I also have a couple 7K crossover cards for the 5235's coming. 'Gonna have to start putting all this stuff together sometime...

John

[Zilch]

If you can get down here tomorrow, John, you can hear it for yourself!

Gotta send this crossover back to Todd on Tuesday for him to complete his system. I've delayed him with all my tweaking around with it here.

Not that I mind storing your 2446J and 2380A horn, mind you.


[Listening to it right now. Be nice to have TWO of them, of course.... ]

[toddalin]

Actually, if you were to stick with one brand cap (excepting the bypass caps) like I did, I priced it out and the Solens were only slightly more than the Daytons. This is because Solen had the 33 mfd value (Dayton doesn't) and these are cheaper than two Dayton 16.5 mfds. (May mave also been the case for the Solen 24 mfd vs two 12 mfd Daytons).

On the other hand Dayton makes a 16.5 that could have replaced the two Solen 8.2 mfds and would have saved some money.

If this was done for PA use, or even just slightly less discriminating tastes, the $3.5 Mills resistors could be replaced by $<1 resistors. If cap types were mixed and lessor resistors specified, the crossovers would probably come in at under $100 each.

BTW, when I put this on the scope over the weekend, I found the actual crossover points (-3 dB) to be maybe a little under 700 Hz (on the bench). There is really no reason that couldn't even be used with the 375 drivers. I'll look at the one in the cabinet driving its actual load today.

Regarding cascading the tweeter. If the L-pad can attenuate the tweeter to the proper balance level with the tweeter signal only going through the cap/coil (not cascaded), wouldn't this more direct hook-up result in improved sound simply by virtue that the signal goes through fewer components that may each leave their own sonic signiture??? (The minimalist approach.)

Thanks, Todd.

Allegedly, Solens don't need bypass caps, so they're cheaper than Daytons + Thetas. Like you, I'd probably bypass, anyway.

Tomorrow's a holiday, so I get another day to play here.

I'll send your prototype back on Tuesday leaving in the changes I made for you to try. It's easily restored to your original topology, if you decide to do that, tho.

May have to build myself up a pair of these; they seem to work with just about anything here....

[toddalin]

If you want to hold on to it for another week, no problem. May as well get all the mileage out of it that you can.

Thanks, Todd.

Allegedly, Solens don't need bypass caps, so they're cheaper than Daytons + Thetas. Like you, I'd probably bypass, anyway.

Tomorrow's a holiday, so I get another day to play here.

I'll send your prototype back on Tuesday leaving in the changes I made for you to try. It's easily restored to your original topology, if you decide to do that, tho.

May have to build myself up a pair of these; they seem to work with just about anything here....

Yes, but compared to your others and personal experience, how do they sound???

[Earl K]

Hi Todd

If this was done for PA use, or even just slightly less discriminating tastes, the $3.5 Mills resistors could be replaced by $<1 resistors. If cap types were mixed and lessor resistors specified, the crossovers would probably come in at under $100 each.

- I use 50¢, 10 watt power resistors & quite like them . I never blame the resistors for all the different textures my various cap recipes conjure up .

BTW, when I put this on the scope over the weekend, I found the actual crossover points (-3 dB) to be maybe a little under 700 Hz (on the bench). There is really no reason that couldn't even be used with the 375 drivers. I'll look at the one in the cabinet driving its actual load today.

- I built up this networks' band-pass portion about 10 days ago. I measured an electrical 3 db down point ( with actual horn load in place ) of @ 780 hz ( if my memory is correct .) I used the "db counter" function on my Loftech/Goldline generator to measure the electrical drop . I did need to approximate the .8mH coil with 3 .56mH coils arranged in a parallel/series topology / so that would introduce a margin of error in my findings .

Regarding cascading the tweeter. If the L-pad can attenuate the tweeter to the proper balance level with the tweeter signal only going through the cap/coil (not cascaded), wouldn't this more direct hook-up result in improved sound simply by virtue that the signal goes through fewer components that may each leave their own sonic signiture??? (The minimalist approach.)

- My own preference ( for sonic concerns ) would be to avoid running the UHF signal through the entire HF portion . I don't feel that getting the benefit of the padding from that 16 ohm Lpad is worth putting the UHF signal through the 2 extra inline caps.

- I'd deliver signal directly to the UHF section and spend the minimal $$ on a two resistor "fixed" pad ( placed just before/"source-side of" the variable 8 ohm pad ) . This mid circuit pad will allow one to rotate into the more normal operational area of the 8 ohm variable pad . Assuming the variable Lpad still "reads" around 8 ohms ( with load in place & attenuated @ 9 db ) I would create a simple 6 db fixed pad with 4 ohm & 8 ohm resistors ( the 4 ohm is the build-out resistor ) .

[toddalin]

As noted, I did some more testing today. Using a sine wave generator through a working speaker system (under the actual load it is to drive), and using an a/c volt meter on the speaker input terminals the electrical minus 3 dB points are approximately:

Woofer LP is electrically (1/2 voltage) down 3 dB at about 700 Hz.

Mid HP (from woofer) is down 3 dB at about 650 Hz.

Mid LP (to tweeter) is down 3 dB at about 7,500 Hz (50 mH coil).

Tweeter HP (from mid) is down 3 dB at about 5,500 Hz (50 mH coil).

These pretty much confirm what the scope saw on the bench.

[Zilch]

Your remark was pointed out to me in an email and I felt compelled to respond.

You're insufferable!

UT, oh -

SYNTAX ERROR!!!

[How 'bout "Presumably," then.... ]

Todd built with Theta bypassed Solens, his option.

I merely affirmed my understanding that was not necessary with the parts list above.

But ALSO, that one might try it both ways.

I stated I've never built with Solens, and don't know.

I ain't rippin' the Thetas outta Todd's crossover to find out, nope.

It sounds fine....

BTW - It's a real sad day when you guys start sending me emails and PM's asking me about Zero's recommendations...

I hate riding herd on his bullshit and I don't have time for it.

Please don't be buggin' Giskard about what I post, folks. When I do really stupid stuff, he's not above calling me on it right here.

I don't mind that a bit. In fact, I appreciate it. It's usually illuminating.

["Allegedly" may raise issues, but I don't suspect it warranted a bunch of background correspondence....]

[Zilch]

- I'd deliver signal directly to the UHF section and spend the minimal $$ on a two resistor "fixed" pad ( placed just before/"source-side of" the variable 8 ohm pad ) . This mid circuit pad will allow one to rotate into the more normal operational area of the 8 ohm variable pad . Assuming the variable Lpad still "reads" around 8 ohms ( with load in place & attenuated @ 9 db ) I would create a simple 6 db fixed pad with 4 ohm & 8 ohm resistors ( the 4 ohm is the build-out resistor ).

Yep. Several options since I moved the MF L-Pad back into its original position per 310x topology.

For example, using 2406/7H as a tweeter on a CD horn uses most of the available headroom of the cascaded connection, because it's taking more energy to distribute the UHF more broadly as opposed to focusing it. I'm thinking I might connect the UHF filter for that combination ahead of the MF L-Pad with additional separate attenuation, as you describe, or direct, per Todd's original modification.

All of those choices for connecting the UHF are easily available, now....

[Johnaec just dropped off another 2446J/2380A and a pair of 2405H UHF drivers to try.... ]

[Zilch]

As noted, I did some more testing today. Using a sine wave generator through a working speaker system (under the actual load it is to drive), and using an a/c volt meter on the speaker input terminals the electrical minus 3 dB points are....

It's interesting to review JBL's own published measurements on the crossover points:

http://www.jblproservice.com/pdf/Net...%20Network.pdf

http://www.jblproservice.com/pdf/Net...%20Network.pdf

5 kHz for 3105 (I THINK that's a "5" there,) and 7 kHz for 3106?

If I understand correctly, that's electrical. The acoustical performance will vary with the drivers used....