Can You Design Me a Crossover That:

[edgewound]

Todd...

Following Giskards recommendation and doing a little searching through my service lit...the L200B uses the HL91 crossed over at 800Hz but uses the LE85 driver with a 136A woofer. The L200A also used an LE85 & LE15B driver crossed at 1200Hz with the same horn. So Giskard seems to know that the LE175 will be fine with the HL91 at 800Hz so go for it. Personally I'd opt to cross the LE175 at 1000Hz just for a margin of safety at higher power levels and transients with home theater sound tracks. Besides that...the 4430 (2235H) crossover is at 1000Hz and that seems to sound pretty good. Theres plenty of software available at Parts Express to design that crossover for you...and they have the parts too. Have at it!!!

[Paul Joppa]

...
Changing out the 130As to 2235's left a "hole" in the area between 500 - 1,000Hz. To me, this is perceived as a muffling of peoples voices.

I am currently using an N1200/N8000. I would like to crossover the woofer to the horn at about 800 Hz. This should be high enough to let the horn operate within its range while reducing the size of the "hole." A two-way that retains the N8000 would work fine. All components are 8 ohm.

Thanks

First, the "hole" as others have noted may just be the reduced woofer sensitivity. The N1200 won't adjust the horn down far enough to match. It's also possible the different woofer HF rolloff changes its effective time delay, and a phase reversal of the woofer might help fill in.

OK, then here's my perspective on the technical history.

Originally, the LE-15/LE175 (S-7) crossed at 500Hz. My perspective - that was to keep the phase difference small enough to run the drivers in phase. (Plus, the LE-15 crapped out above 500Hz.) The 130A/175 combo at 1200Hz has a phase difference close to a wavelength so the drivers can be in phase at crossover.

The first monitor (4420?) upped it to 800Hz, probably to protect the 175 from damage. But the phase difference at 800Hz is about 1/2 wave length (assuming the woofer phase origin is some 4" behind the front panel). I don't know if they reversed the woofer phase for that or not. The longer H92 at 800Hz came closer to matching the 1200Hz crossover with the H91 horn, again allowing the woofer phase to be the same as the HF.

The crossovers, N500 and N1200, are pretty straightforward and easily adjusted to an 800Hz crossover - or just use the 4420 design, with the reversed phase as necessary. But do the calculations to get the sensitivity matched!

[Zilch]

Paul: S7 was LE-85, and you mean 4320, not 4420, I would assume....

Can you design me a crossover that can better integrate the 2235 with the LE175 on an HL-91 with an 075?

http://www.lansingheritage.org/image...omp/page08.jpg

[Paul Joppa]

Paul: S7 was LE-85, and you mean 4320, not 4420, I would assume....

http://www.lansingheritage.org/image...omp/page08.jpg

Shouldn't trust memory at my age!

Anyhow, the LX5 was specified for LE175, LE85, and 375 in the earlier versions; in fact before the 4320 with LX13 at 800Hz, the studio monitor used the LX5 at 500Hz. All of these were specified for use with the LE175/HL91 at one time or another, though in later years the minimum crossover for the LE175 drifted up to 800, 100, 1200, and eventually 1500Hz in the "potato masher" horn. I always assumed that was because amps got bigger and people were blowing out the drivers.

Sounds like several classic crossovers could be adapted, and a few were actually meant for the 2235. AFAIK, anything that used the LE85 will work fine with an LE175, losing mostly a litle HF extension. The big problem is always the tapped inductor/autoformer in the crossover, so an original JBL on the used market would be a lot easier than a new scratch-built crossover.

Always wondered if there was much market for suitable tapped inductors. It should not be that hard to get some made up, if one could amprtize the design and tooling costs (and if JBL did not object!)

[Paul Joppa]

Giskard- sorry, I should probably not have stepped in so fast after being gone so long. (Have no idea what an "LCS" is ...)

Back to occasional lurk mode for me!

[Zilch]

I should probably not have stepped in so fast after being gone so long.

Naw, stick with us here. We'll figure it out.

LE175 was S6, or something. LCS was JBL "Loudspeaker Component Series," I think. Just found out about that recently in the EN3 thread....

Todd:

If LX200B is N200B, that's what I'd build, 'cause there's no tapped inductor in it, but leaving out the HF boost loop (1uF, 0.16 mH, 5 Ohms,) since you're adding on the N8000 and UHF driver. It's pretty simple. Add bypass caps. Done.

I can measure the inductor DCR's, if that's what you decide to do....

http://manuals.harman.com/JBL/HOM/Te...L200B%20ts.pdf

[toddalin]

Naw, stick with us here. We'll figure it out.

LE175 was S6, or something. LCS was JBL "Loudspeaker Component Series," I think. Just found out about that recently in the EN3 thread....

Todd:

If LX500B is N200B, that's what I'd build, 'cause there's no tapped inductor in it, but leaving out the HF boost loop (1uF, 0.16 mH, 5 Ohms,) since you're adding on the N8000 and UHF driver. It's pretty simple. Add bypass caps. Done.

I can measure the inductor DCR's, if that's what you decide to do....

http://manuals.harman.com/JBL/HOM/Te...L200B%20ts.pdf

Thanks Zilch.

I assume that the N200B is similar (at least in function) to the LX200B referred to by Giskard. There don't appear to be any tapped inductors in the N200B schematic. I assume that I can get the other parts at Parts Express? Would there be a way to bias this design using the 9 volt battery, and if so, any idea if the difference would even be noticable?

There is currently a pair on N200Bs on epay with a BIN of $185. Seems kind of steep for the value of the parts.

http://cgi.ebay.com/Mint-Pr-Vintage-...QQcmdZViewItem

BTW, in the mean time, I've found that 3 dB of PEQ boost around 1,000 Hz does a nice job of filling in the "hole" thereby restoring vocal intelligability.

[Zilch]

There is currently a pair on N200Bs on epay with a BIN of $185. Seems kind of steep for the value of the parts.

Yeah, and OLD parts, too. The ones you build will be better. We seem to have confirmed it's the one to do.

Parts Express, yes.

Lemme look at biasing here....

EDIT: Yup, biasing's gonna be easy, if we just do it in the HF section. I'll draw it up here, what I propose.

Key to getting it right is DCR of the 0.8 mH inductor.

$20 apiece more will bias the LF, as well, if we change the Zobel per N3134 (bottom). $30 apiece more if not, 'cause the big caps get expensive.

Bypass caps omitted for clarity. Them alone's gonna be $20 to $25 per crossover.

Check me, please:

[Ian Mackenzie]

I would have thought with Spice and Clio that would be a piece of American Pie (I mean cake for the rest of the world)

A useful and well written article here for those interested to learn the finer points of passive crossover design incl Zobels and their effect.

http://sound.westhost.com/lr-passive.htm

But this is only the beginning.

There ain't no substitute for a good set of ears. The more I learn to appreciate and understand the original vintage JBL crossovers the more obvious the amazing skill of engineers like G.T and others is who painstakingly tuned and voice each system so carefully.

[Zilch]

SO, Ian, you suggesting to go with the calculated Zobel, or the original design?

Per N3134 is the upper curve, vs calculated (middle) and original design (lower), all with 7.5 Ohms.

'Course, it's how it intereacts with the actual woofer impedance vis-a-vis the total network and system, in the end.

That's an "empirical" determination.

O.K., 2 X 47 uF, then.

Them 68's are $18.43 apiece.

OR, put in the 68's and try 6 Ohms for the calculated Zobel, 7.5 Ohms for the original spec....

[Titanium Dome]

(snip)

But this is only the beginning.

There ain't no substitute for a good set of ears. The more I learn to appreciate and understand the original vintage JBL crossovers the more obvious the amazing skill of engineers like G.T and others is who painstakingly tuned and voice each system so carefully.

(With apologies in advance to the thread's contributors for going a bit OT. None of these comments are aimed at the present effort.)

That very thought always leads me to this conundrum:

JBL/Harman have the money, the facilities, the brains, the experience, the ears, and the theory to do just about anything they damn well please, and IMO their better efforts are going to have a very high likelihood of kicking the ass of anything we do; YET one always has the nagging suspicion that what happens in the lab gets mucked up in the translation to production by marketing, accountants, sales decisions, etc., SO we probably get some compromises that result in "it is what it is for a variety of reasons" comments by some of our more experienced hands. HOWEVER we all want to believe we can take a good thing and make it great with just a bit of tweaking, so maybe we can figure out where JBL/Harman cheaped out or took "good" instead of "great" and we can create a better way to do it. MAYBE my very serious effort to improve things will result in my greatest crossover ever which will be better than GT's "it is what it is for a variety of reasons" crossover, but I have to tell you, I seriously doubt it.

I think the biggest improvements for some of us will be in bringing old crossovers back up to spec or maybe hotrodding them a little with better parts than were available with the originals or by bypassing the caps.

I've studied the simple crossovers in the Performance Series for some time, and I've decided anything I do will probably F them up. I guess I'm deliberately placing myself in Giskard's cynically invoked 95% who couldn't do this on his best day, and happy to do it. Now I'll have more time to just enjoy the darn things.

To the other 5% of you, I salute you, and maybe someday I'll pay you a thousand bucks to kick somebody's crossover butt for me.

[Zilch]

Your observation is relevant, Ti Dome. These old networks are reputedly sound, but the total systems aren't up to today's sonic standards (read "pretty awful," above, and "dreadful" by others). I'd say that's licence for us DIY hacks to "mess" a bit, ourselves.

[Ian Mackenzie]

Not necessarily. You need to determine empirically the desired target acoustic rolloff (taking into account the raw response on the baffle) of the woofer and work from there empirically.

Regards the target acoustic rolloff there is no text book solution for an individual system. Theoretically calculated crossovers often fail to win favour over the empirical method.

Remember the voltage drive and the amplitude response are two different things..you really need to be measuring both to arrive at the rolloff characteristic that best suits the system at hand.

This may end up being a compromise of on and off axis smoothess in the crossover region and a host of other factors.

SO, Ian, you suggesting to go with the calculated Zobel or the original design?

Per N3134 is the upper curve, vs original spec.

'Course, it's how it intereacts with the actual woofer impedance vis-a-vis the total network and system, in the end.

That's an "empirical" determination.

O.K., 2 X 47 uF, then, per Giskard.

Them 68's are $18.43 apiece.

OR, put in the 68's and try 6 Ohms for the Giskard calculated Zobel, 7.5 Ohms for the original spec....

[Ian Mackenzie]

I was really thinking more of the consumer JBL L series and corresponding Prof 43xx series and one might wish more finely tuned than the kits.


EDIT: Okay I know see your system:Todd it would be helpful if you could post some close ups of your enclosures in this thread.

Sorry it has taken me a while to catch up with Todd's stuff per the thread below. Todd's drivers do not necessarily mate with any of those above and it appear not to be of the woofer for that original box.



http://www.audioheritage.org/vbullet...ead.php?t=8591


If Todd prefer to keep with what he's got then its a case of working something out like a poor mans L300 with the ring radiator..nothin wrong with that. But these H 91/92 /93 horn designations confuse the crap out of me. Am I right in thinking the 91 is the 2307 ..a 1200 hertz horn or am I sun struck?

Not meaning to de-rail any noble efforts but if it were me I would use the 175 (I think Rob uses one successfully) with the bum cheek 2344a and it would fit on the front baffle I think. Use the 075 to zap aliens or trade it for a set of 2344's and some change on Ebay

There is no question that that horn works very very well with the 2235 woofer (and with some tweaking others) and will result in a quantum leap in subjective improvement over any reworked crossover for the device on hand (horn) in IMHO

(With apologies in advance to the thread's contributors for going a bit OT. None of these comments are aimed at the present effort.)

That very thought always leads me to this conundrum:

JBL/Harman have the money, the facilities, the brains, the experience, the ears, and the theory to do just about anything they damn well please, and IMO their better efforts are going to have a very high liklihood of kicking the ass of anything we do; YET one always has the nagging suspicion that what happens in the lab gets mucked up in the translation to production by marketing, accountants, sales decisions, etc., SO we probably get some compromises that result in "it is what it is for a variety of reasons" comments by some of our more experienced hands. HOWEVER we all want to believe we can take a good thing and make it great with just a bit of tweaking, so maybe we can figure out where JBL/Harman cheaped out or took "good" instead of "great" and we can create a better way to do it. MAYBE my very serious effort to improve things will result in my greatest crossover ever which will be better than GT's "it is what it is for a variety of reasons" crossover, but I have to tell you, I seriously doubt it.

I think the biggest improvements for some of us will be in bringing old crossovers back up to spec or maybe hotrodding them a little with better parts than were available with the originals or by bypassing the caps.

I've studied the simple crossovers in the Performance Series for some time, and I've decided anything I do will probalby F them up. I guess I'm deliberately placing myself in Giskard's cynically invoked 95% who couldn't do this on his best day, and happy to do it. Now I'll have more time to just enjoy the darn things.

To the other 5% of you, I salute you, and maybe someday I'll pay you a thousand bucks to kick somebody's crossover ass for me.

[Zilch]

What are we up to now?

1) 1 ea. inductor, 2.2 mH, Erse Super Q - $13.55
2) 4 ea. capacitor, 47 uF, Jantzen CrossCap - $44.20
3) 2 ea. capacitor, 68 uf, Jantzen CrossCap - $33.78
4) 1 ea. N/I resistor, 7.5 Ohms, Mills MR - $3.50
5) 2 ea. capacitor, 33 uF, Jantzen CrossCap - $17
6) 1 ea. inductor, 0.8 mH, Jantzen 18 Ga (tentative) - $3.67
7) 1 ea. N/I resistor, 2.5 Ohms, Mills MR - $3.50
8) 1 ea. N/I resistor, 5.0 Ohms, Mills MR - $3.50
9) 1 ea. L-Pad, 16 Ohms, Dayton 50W - $7.50
10) 1 pr. input terminals, Dayton - $6.88
11) 8 ea. capacitor, 0.1 uF, AudioCap Theta - $25.76
12) 4 ea. resistor, carbon film, 2.2M - $0.20
13) 1 ea. battery holder, 9V - $2.10
14) 1 ea. battery, lithium, 9V, UltraLife - $7.99

Total = $173.13 ea., plus shipping and construction materials.

Add 1 ea. N/I resistor, 6.0 Ohms, Mills MR - $3.50 to tweak the Zobel, as desired....