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Mr. Widget
09-13-2003, 12:48 AM
I have gone on about this before, but here it is again with a bit more detail and info that may be of interest to others planning on a similar adventure.

As most of you know the JBL 4355 was the largest example of the JBL 43XX series of monitors. It was an updated version of the 4350. It used slightly different components than the 4350 with a more sophisticated crossover design. The 4350 used the 3107 crossover and the 4355 used the 3155 crossover.

http://www.jblproservice.com/pdf/Network%20Schematics/3107%20Network.pdf

http://www.jblproservice.com/pdf/Network%20Schematics/3155%20Network.pdf


Shortly after deciding to tackle the 4355 project I discovered that the 3155 crossover that I planned on copying used several tapped autoformers in lieu of standard inductors. I called JBL parts seeking these custom parts and was informed that I was SOL. In my search for a solution Giskard generously offered to contact G.T. (The original designer of the 3155 network.) and together they worked out the L-R networks to create an equivalent circuit to the original 3155 with autoformers.

Below is a schematic of the new 3155. I added the 16 ohm and 8 ohm L-pads as per the original 3155, other than that I built this design exactly as suggested matching L, R, and C values to within 1%.

Now the 3155 crossover is a passive 3 -way design meant to be used in conjunction with an active crossover to complete the 4-way system.

I have used a 24dB/octave and a 12dB/octave active crossover to complete the system. I also tried the system with a 12dB/octave low pass section on the twin woofers and allowing the 2202 woofer to run out naturally being limited by enclosure tuning.

I was not satisfied with the sound quality of my Rane AC22 crossover as to my ears at least it is not as clean and musical sounding as I would like. Unfortunately every combination that I tried with the 12dB/octave crossover sounded thick and mid bass heavy. Changing crossover frequency between 100Hz and 400Hz would change it slightly but not fix it. I even tried a natural run out for the 2202 and crossing the 2235Hs at 100Hz. Still not right. Shooting the system with my RTA confirmed this showing a broad bump centered between 200Hz. and 300Hz. I try to avoid EQ if at all possible, but I was thinking that a notch filter was in my system's future.

Then Giskard came to the rescue again! He posted:

http://www.lansingheritage.org/html/jbl/reference/technical/inside-monitor.htm

If you read the last column of the second page it clearly addresses my problem. It was the mutual coupling of the woofers and the 2202! I scratched my head a bit, thought about getting a 5234A with the appropriate card in it, and then tried a fix with equipment that I have here. I used the low pass section of the Rane AC22 to feed the 2235Hs. The crossover frequency is around 275Hz. With a parallel output of my preamp I fed an Audioarts 12dB/octave crossover with it's high pass section set to around 275 Hz. Bingo!!! The asymmetrical slopes help create the needed notch and the steep slope on the 2235Hs helps prevent them from contributing too much mid bass.

Mr. Widget
09-13-2003, 12:49 AM
The active setup described above feeding a pair of Hafler 9505s powering my project box 4355s is truly beyond my expectations. I expected the tonality to be good. I knew the transient response would be great. But with the physical modifications that I have made to the system the imaging is the best I have ever heard from a JBL system. It seams to be keeping up or even bettering my upstairs "audiophile system". It is even better than the 4430s I've heard, plus it has the extension in response that the 2405 allows. The drawing below shows my current setup along with my proposed one box solution. Originally I was using the 2397 horn, but now I am using a pair of my Westlake copies... smooth, natural, all of the dynamics of a horn system, but so smooth and natural! My other JBLs never sounded as good at low levels as they did at kick-in-the-pants levels. This system still sounds spectacular even at very low levels and because it is a 4355 it can play scary loud!

Mike C
09-13-2003, 02:45 AM
Hi Mr W. I too am getting a little closer to my idea of a nice system. I posted the other week how I had been playing around with a pair of 4691B's I bought. Well this week I purchased 2 2220-h's and put them into some bins. It goes like this:

One channel - VLF 2241-H 18" in 6.5 cuft tuned to 40hz
- MB 2220-H 15" in 5 cuft eq'd to minimise response under 100 hz ( will build 1.5 cuft bin soon )
- Mid 2123-H 10" in .5 cuft bin
- HF Altec 909-16 and modified 511B horn
Apart from the 2220-h in the 5 cuft bin ( ex 4331 cabinet ) the other drivers seem to be in their correct enclosures. Well I hooked it all up this afternoon, ( both channels ) and after tuning everything I listened to one of my favorite tracks. Harry Connick Jnr ( Star Turtle track 12 "Never Young" ) Wow I near shit my self, the slam of this system is incredible, the kick and snare drums were in the room with me, I swear !!!!!. The mid bass is better than any thing I have heard to date. The sound stage is so large and life like and the imagery is very precise. Apart from the HF section I think this system is getting close to the ancient Drew Daniels system with out the grunt. I have a total of 600 watts rms per cannel. Any way this system has given me some clear directions on where I'm going from here with it all.
Mike.C

Robh3606
09-14-2003, 06:55 AM
Thanks Mr.Widget

For posting your impressions. Sounds like a killer set-up. I was wondering about the improved imaging. I would think it is at least partially related to the verticle array on the mids and highs. In the 4350 Tech Manual it states you should be at least 8 feet away. How are they near field now?? With my set-up using the 2344 and a verticle array I can get real close and not loose driver blend or imaging. I would guess these are the same way in spades. Are they toed in at all??

Rob:)

4313B
09-14-2003, 07:07 AM
Originally posted by Robh3606
Thanks Mr.Widget

Are they toed in at all??

Rob:)
He has a posted drawing here: :)

http://www.audioheritage.org/vbulletin/showthread.php?s=&postid=6042#post6042

Robh3606
09-14-2003, 07:14 AM
He has a posted drawing here:


Thanks!

Rob:)

Mr. Widget
09-14-2003, 12:29 PM
Originally posted by Robh3606
Thanks Mr.Widget

For posting your impressions. Sounds like a killer set-up. I was wondering about the improved imaging. I would think it is at least partially related to the verticle array on the mids and highs. In the 4350 Tech Manual it states you should be at least 8 feet away. How are they near field now?? With my set-up using the 2344 and a verticle array I can get real close and not loose driver blend or imaging. I would guess these are the same way in spades. Are they toed in at all??

Rob:)

The only changes from the 4350/4355 that I made that would influence the imaging are the vertical alignment and the 2397/Westlake horn. One of the factors that determine image stability is an even polar response. This is one of the hallmarks of the 2397. The image stability of my 4355s is remarkable, but what I found so surprising was how well these speakers convey stage depth. Most JBL systems have a sound that is projected or is forward, these speakers while certainly not laid back, are not at all forward.

I would like to make the comment, that while I am raving about a system utilizing a horn that I am also selling, the factory 2397 has all of these traits as well and in my listening tests in this system both horns sounded equally wonderful.

As far as near field listening goes, the drivers are spread too far apart for that application. I am listening at a distance of 10' and there the pair of speakers form a cohesive sound stage.

Robh3606
09-14-2003, 01:07 PM
"The only changes from the 4350/4355 that I made that would influence the imaging are the vertical alignment and the 2397/Westlake horn. One of the factors that determine image stability is an even polar response."

Yes and the horizontal placement must effect the polar response especially through the crossover region. There has to lobbing somewhere.

"As far as near field listening goes, the drivers are spread too far apart for that application."

Yes my array has the same issue. I should have asked the question better. What I was curious about is could you hear the 4355's loose their cohessive sound stage as you got closer and can you get closer now before that happens??

Rob:)

Mr. Widget
09-14-2003, 01:47 PM
" Yes and the horizontal placement must effect the polar response especially through the crossover region. There has to lobbing somewhere."

Yeah, I don't know why they went that route. The earliest 43XX had a vertical alignment. With the 4350/55 there are baffle real-estate issues, but as you know they chose to offset the 2405 on all of the later 43XX.

I would love to test the near field for you, but unfortunately each "4355" is made up of three boxes plus one big ass horn sitting on top. The only way to test it would be to shrink the equilateral triangle to 8', then 6', then 4' and compare the results. I am not willing to go to that much trouble.:( .


The thing is these speakers are so large that even sitting 10' away from them, the response of my non audio friends is a sarcastic, "Could you sit any closer to them?". This is probably prompted in part from this setup being in my HT where the screen and HT speakers are about 16' away. I set the 4355s up in a 10' equilateral triangle based on JBL's recommendation of an 8' minimum and the room I am in.

If I move closer to one speaker with only one playing, I am not aware of the source being made up of a multiple of elements until about 6'-7' away.

I think the bottom line is, to really get the most out of a speaker like this you must have a fairly large room. These speakers would probably not image worth a damn in a 12' by 14' room with all of the early reflections. The other thing, I don't know if you took a close look at the room drawing in the "Toe-in" thread, but most of the 10' high walls are covered with heavy velvet drapes.

Robh3606
09-14-2003, 02:09 PM
If I move closer to one speaker with only one playing, I am not aware of the source being made up of a multiple of elements until about 6'-7' away.

That what I was looking for! Thanks.:D


I would love to test the near field for you, but unfortunately each "4355" is made up of three boxes plus one big ass horn sitting on top. The only way to test it would be to shrink the equilateral triangle to 8', then 6', then 4' and compare the results. I am not willing to go to that much trouble.

Don't move thing!!! I am in a smaller room and about 7 feet away. I was curious about the walk up effect not a true nearfield set-up test. I would not move mine either but then again I got no place to go!!

Thanks Rob:)

boputnam
09-14-2003, 04:51 PM
posted by Mr. Widget
Shooting the system with my RTA confirmed ... a broad bump centered between 200Hz and 300Hz. ... my problem ... was the mutual coupling of the woofers and the 2202!

Hey, Widget...

I've been pondering this all week-end, since the Friday taste-test. (Nice! :thmbsup: )

If I'm deciphering your "3155 Modified" schematic correctly, you are running all transducers off the 3155 as Red input to Red transducer terminal post. Right? If so, they are all running JBL convention, negative polarity.

I'm guessing your LF's (2235's) are also running JBL convention negative (Red input to Red terminal). So, the area of frequency overlap between the LF and the 2202 would be summed, not cancelled. That is not what JBL do with the 4343 and 4345.

Both the 3143 and the 3145, when either biamped or four-way passive, run the LF negative (Red input to Red terminal post), and the "uppers" (MF, HF, UHF) all opposite polarity, positive (Red input to Black transducer terminal).

I'm wondering if the troubling 200-300Hz "hump" could be obviated or lessened by reversing polarity between the transducer groups (i.e, LF and others), and simplifying your active crossover configuration.

:duck:

Earl K
09-14-2003, 06:28 PM
Hello Mr Widget

Great to see your projects coming along so nicely.

Your following statement has me very intrigued,


Most JBL systems have a sound that is projected or is forward, these speakers while certainly not laid back, are not at all forward.

It's actually been years since I heard a stock JBL "system" so I'm pretty well out of the loop for having hands-on experience with the 43xx line.

Irregardless of that, I use JBL transducers for my own purposes.. My present quasi-MTM setup has extremely strong imaging capabilities ( side to side ) and most important ( for me ) - front to back depth . The thing is , all that front to back imaging is behind the enclosures front line or "upstage"( for the theatrically inclined ). This has kept me transfixed for more listening hours than I'm willing to admit to. In my (MTM) case, this imaging appears to be the combination of the round mouthed horn and the DC blocking caps I'm using ( among other system things ). In another thread I've talked about my recent foray into different caps. Well, all these newer caps I'm trying have moved the soundstage forward and/or collapased it quite a lot. Certainly not what I was after when I started my cap. exploration.

In the case of your 435Xs' , to what, do you attribute that receeding soundstage ?

regards <> Earl K :)

Mr. Widget
09-14-2003, 08:45 PM
" I'm wondering if the troubling 200-300Hz "hump" could be obviated or lessened by reversing polarity between the transducer groups (i.e, LF and others), and simplifying your active crossover configuration."

In my original setting up of the system, flipping the polarity of the 2202 was one of the first things that I tried. While it did change the sound a bit, it didn't solve the problem. In any event the JBL article that discussed this coupling problem was talking about it in the 4343. A system with switched polarity. Personally, all things being equal, I would prefer to maintain system phase if possible.


" In the case of your 435Xs' , to what, do you attribute that receeding soundstage ?"

I am really happily surprised by the stage depth forward and backward as well as extending left and right beyond the physical spacing of the speakers. I have no concrete conclusions as to why it is working so well. As I said the polar response is probably responsible for the rock solid stability, but the overall stage depth was a happy surprise. I haven't tried to "time align" the system, so unless by some happy accident it just worked out, I wouldn't say that it is time or phase coherent. I am a firm believer in vertical alignment, I am sure that it helps, but I have heard many other systems that were in vertical alignment and they did not image as well.

TimG
09-15-2003, 11:59 AM
Your custom horns look awesome and that's great that you were able to get plans for an updated version of the 3155 crossover. Do you know what the R values are for the inductors listed in the schematic? They all appear to be aircore inductors. If you knew the gauge of wire used the R could probably be estimated.

Mr. Widget
09-15-2003, 01:47 PM
Thanks, I am using inductors throughout with minimum R values.

For the 2.4 mH coil on the 2202 I am using a premium laminated iron core inductor to keep R low. For the three inductors on the 2441 I am using Goertz Alpha-Core flat ribbon coils, and for the two inductors on the 2405, they are moderately large gauge high purity air core coils.

Off the top of my head I don't remember the gauges of the wire or ribbon used, but I did make sure all of the DCRs were quite low. None of the inductors were stock as I trimmed all of them to length to achieve the exact inductance specified.

Dwight
09-15-2003, 05:59 PM
Are any of the "clones" using the 2234H or dual 2235H's? Maybe
the "broad bump between 200Hz - 300Hz" was a problem that
JBL addressed by using the 2234H to limit the "2235H's from contributing too much mid bass".

Mr. Widget
09-15-2003, 06:30 PM
JBL built the 4355 with dual 2235s and the 4435 with dual 2234s concurrently. They are different design philosophies and some prefer the former and others the latter. In the case of the 4435, the use of the 2234 woofer does not solve the midrange peak problem, their crossover does. It is designed to only allow both woofers work in tandem below about 100Hz, above that the woofer directly below the HF unit becomes the sole driver with increasing frequency.

Here is the excerpt the describes the situation I am talking about with a large cone mid driver and a 15" woofer, or in the case of the 4355 a pair of 15" woofers. JBL recommends the same special active crossover card for both the 4345 (an updated big brother to the 4343) and the 4355.

4313B
09-15-2003, 06:37 PM
Yet another voltage drive :p

boputnam
09-15-2003, 06:56 PM
Originally posted by Giskard
Yet another voltage drive :p OK, a challenge for you, if you're in a goofy enough mood for it. You're the only one I know could get it done...

Can you show the two cases of, say, either the 4343 or 4345, in biamp mode with the LF and "others" both in phase and in opposite phase (polarity)?

I'm dang curious how much of the troublesome summing is obviated by having the LF and low-MF out of phase.

Pretty please? :yes:

We need a smily face for a dog barking up a tree... :rotfl:

Mr. Widget
09-15-2003, 07:09 PM
I'll add on to Bo's question, does anyone have an idea why JBL would design the 4345 with the 10" mid with reversed polarity and the 4355 with it's 12" mid in correct polarity?

The one difference that I can think of is that the 4355 is ALWAYS bi-amped.

4313B
09-15-2003, 07:43 PM
Originally posted by Mr. Widget
I'll add on to Bo's question, does anyone have an idea why JBL would design the 4345 with the 10" mid with reversed polarity and the 4355 with it's 12" mid in correct polarity?

The one difference that I can think of is that the 4355 is ALWAYS bi-amped.
My guess would be that it has to do with the lengths of the horns. I think one is 4" longer than the other.

boputnam
09-15-2003, 08:25 PM
Originally posted by Giskard
My guess would be that it has to do with the lengths of the horns. I think one is 4" longer than the other. Very close...
If the brochures can be trusted :nutz: the 2307 is 7-3/4in and the 2311 is 4-5/8in (4345 and 4355, respectively), for difference of 3-1/8in.

So, whaddya think - is it possible to model the 4343/4345 biamped, and see the effect of opposing the phasing? Or should I :thnkfast:

I'm still marvelling in the improvement of the new diaphragms for the 2421B's. I'm willing to try ANYTHING :dancin:

boputnam
09-16-2003, 10:44 AM
Holy smokes! :shock:

That'd be that 4343 255Hz "bump" the Widget was referring to, eh?

Busy boy/girl, Giskard...

:thmbsup:

Mr. Widget
09-16-2003, 10:53 AM
Bo, those are phase angle plots, not frequency plots.

boputnam
09-16-2003, 10:59 AM
Originally posted by Mr. Widget
Bo, those are phase angle plots, not frequency plots. I realize that, but I'm trying to understand if that phasing is contributing to the "bump". Whaddya think?

boputnam
09-16-2003, 11:00 AM
Originally posted by Giskard
You guys know each other? You're being goofy...

But I've laughed at the other post, all morning. I have no clue what that meant.

Mr. Widget
09-16-2003, 11:02 AM
" I realize that, but I'm trying to understand if that phasing is contributing to the "bump". Whaddya think?"

I don't think that it is that simple of a relationship that one can infer one from the other.

In any event, I think the girl/boy with bread breath is far more amusing.

4313B
09-16-2003, 11:23 AM
Originally posted by boputnam
OK, a challenge for you, if you're in a goofy enough mood for it. You're the only one I know could get it done...

Can you show the two cases of, say, either the 4343 or 4345, in biamp mode with the LF and "others" both in phase and in opposite phase (polarity)?

I'm dang curious how much of the troublesome summing is obviated by having the LF and low-MF out of phase. Use an RTA and find out.

boputnam
09-16-2003, 11:56 AM
Originally posted by Giskard
Use an RTA and find out. Widget? Are you game? I'll run wires and sling beers. :yes:

Closest I'll get to Tahiti... :smthsail:

Ian Mackenzie
09-16-2003, 02:55 PM
Yeah,

And Mr Widget we wanna an email/post card from Tahiti please.

:smthsail:

Ian

4313B
09-16-2003, 08:31 PM
Originally posted by boputnam
OK, a challenge for you, if you're in a goofy enough mood for it. You're the only one I know could get it done...

Can you show the two cases of, say, either the 4343 or 4345, in biamp mode with the LF and "others" both in phase and in opposite phase (polarity)?

I'm dang curious how much of the troublesome summing is obviated by having the LF and low-MF out of phase.
Ok, here is what I get for the 4343 / 4350 crossover card in the 5234A. The dip is with the 2235H and 2122H in phase and the hump is with the polarity on the 2122H reversed.

4313B
09-16-2003, 08:41 PM
Originally posted by boputnam
OK, a challenge for you, if you're in a goofy enough mood for it. You're the only one I know could get it done...

Can you show the two cases of, say, either the 4343 or 4345, in biamp mode with the LF and "others" both in phase and in opposite phase (polarity)?

I'm dang curious how much of the troublesome summing is obviated by having the LF and low-MF out of phase.
Here is what I get for the 4344 / 4345 / 4355 crossover card in the 5234A. The hump is with the 2235H and 2122H in phase and the dip is with the polarity on the 2122H reversed.

boputnam
09-16-2003, 08:42 PM
Originally posted by Giskard
Ok, here is what I get for the 4343 / 4350 crossover card in the 5234A. The dip is with the 2235H and 2122H in phase and the hump is with the polarity on the 2122H reversed. You're not goofing on me, are you? :confused:

I would have expected the hump to be where the two were in-phase and additive... Oh NO!!! :banghead:

Thanks, heaps, for the model. You do truly great work. :yes:

4313B
09-16-2003, 08:48 PM
I'm too tired to check my work yet again tonight. Maybe I'll look at it again in the morning. It will take about 1/10th the time for you to measure the whole mess with an RTA as opposed to me trying to model an active filter in a software package that only supports passive filters. However, I was pretty tenacious and feel that I got damn close with the model. The graphs I posted earlier were very good at showing the phase of the two filters. Feel free to repost them if you want.

boputnam
09-16-2003, 08:55 PM
Originally posted by Giskard
It will take about 1/10th the time for you to measure the whole mess with an RTA as opposed to me trying to model an active filter in a software package that only supports passive filters. I knew - or had a feeling - it was that difficult. Thanks for the effort.

And, I'd gladly do the RTA thing, but Widget's gone "AWO4355" for a week-ish, so it will wait.

I think the models are excellent - I only question the text description you posted for the 4343 / 4350 - it is opposite that for the 4344 / 4345 / 4355 and of my intuition (which is often wrong, but never in doubt, as dear ol' mom used to remind... :D ).

However, thinking on the phasing plots you posted earlier today, it IS making sense - at least it hangs together. I take it back - your annotations are consistent with the phasing plots. But the reason for the difference between the 4343 / 4350 and 4344 / 4345 / 4355 boggles my feeble mind.

Separately, I agree an RTA test would be most revealing, when Widget beaches here, again. Will do.

"See ya" tomorrow, and thanks again.

4313B
09-16-2003, 09:03 PM
I've posted the voltage drives of both filters elsewhere on the forum. The 4344 / 4345 / 4355 is an 18 dB / octave active filter with both knees set at ~ 290 Hz. The 4343 / 4350 is a 12 dB / octave filter with the low pass knee set at ~ 230 Hz and the high pass knee set at ~ 280 Hz with a mutual -4 dB downpoint at ~ 255 Hz. The phase plots I posted for you earlier should be helpful now that you see what else is going on.

*****

"But the reason for the difference between the 4343 / 4350 and 4344 / 4345 / 4355 boggles my feeble mind."

Don't let it, the 4344 / 4345 /4355 is a better solution in my opinion. I've posted this at least twice before. I would run it with a 4343 or 4350 as well. The 4343 / 4350 card is simply an older design.

Mike C
09-17-2003, 02:24 AM
Hi Widget, A couple of year ago I owned A pair of 4350B's. I sold them along with a lot of other stuff hastely when I found out I had the big "C". Well I got over the cancer but not the sale of the 4350's, They too had a real muddy spot I'd call it around 250-300hz just above the crossover point with the urei network that came with the speakers. A friend of mine lent me a DBX active network to try and after some tinkering the muddyness disapeared. We ended up with the network set at 180 hz and the sound tightened up a whole bunch. I sold the whole system shortly after that so I didn't get to play with them too much. All in all thought I'm sure they didn't have anywhere near the mid bass of the stuff I'm playing with now. I think the benifit of active networks help tune these things and saying that my next purchase will be the DBX drive rack PA system to control the gear I have.

Ian Mackenzie
09-17-2003, 02:36 AM
Giskard,

I appreciate your graphs and note with the 3145 network, these are 12/db slope graphs where in the active network as you state is 18 db slope, hence the assumed reversal of the dip in the graphs.

This is why I conclude the passive network 2122 conections are reversed and the other drivers are wired in phase with the 2122 as they are 18 db 3rd order end render the smoothest response in the passband and xover points.

Ian

:smthsail:

4313B
09-17-2003, 04:40 AM
Hello Ian,

As a follow up here is the passive 12 dB / octave 3144 /3145 filter. The dip is with the 2235H and 2122H in phase. The flat response is with the 2122H polarity reversed.

Ian Mackenzie
09-17-2003, 04:50 AM
Wow,

I wonder whay GT would say to this...excellent stuff.

I have to say GT was certainly on the money with these designs, back then Xover design was so primative, he seems to have covered all the angles and those auto trannis chokes are way too cool.

Can't wait to try out that jasper Router and try some bi amping with the 700B!

Thanks again for these excellent graphs

Ian:cool:

4313B
09-17-2003, 06:54 AM
Originally posted by Ian Mackenzie
I wonder what GT would say to this
As far as what? He thinks I'm goofy for messing around with all these old drivers. :p

Originally posted by Ian Mackenzie
I have to say GT was certainly on the money with these designs, back then Xover design was so primative, he seems to have covered all the angles and those auto trannis chokes are way too cool.
Yes, he really raised the bar and hasn't stopped since! :) I don't think he's too fond of tapped autotransformers though, at least that's what he's indicated to me on a couple of occasions ;)

Originally posted by Ian Mackenzie
Can't wait to try out that jasper Router and try some bi amping with the 700B!
Very cool! :)

Originally posted by Ian Mackenzie
Thanks again for these excellent graphs
You're welcome :) I wasn't really in the mood at first but I got over it :p

boputnam
09-17-2003, 06:56 AM
Originally posted by Giskard
Don't let it, the 4344 / 4345 /4355 is a better solution in my opinion. I've posted this at least twice before. I would run it with a 4343 or 4350 as well. The 4343 / 4350 card is simply an older design. Agreed. The 4344 / 4345 /4355 solution seems an important evolution of JBL's four-way engineering.

And,


Originally posted by Giskard
I wasn't really in the mood at first but I got over it :p Mighty glad you did! Glad I nudged you for it, to begin with! :yes: Proved a very interesting study.

Ian Mackenzie
09-17-2003, 09:29 AM
Seems I have stired at the right time,

(just woke and have a nice pussy purring beside me muhhaha)

Testing my memory here, but I recall the 1977 JBL brochure said something about the mutual coupling of the 2121 & 2231.

By luck or good fortune the Nackamichi active xover we were using back then (1980) was in fact 6 db down at the crossover point so I neatly avoided this hump.

Ian:)

4313B
09-17-2003, 09:55 AM
Originally posted by boputnam
Agreed. The 4344 / 4345 /4355 solution seems an important evolution of JBL's four-way engineering.
Well, if one absolutely has to have that exponential doohicky coupled to a plastic slant plate thingamajigger then I would think the 4344 / 4345 / 4355 would be the ticket ;) What's quite interesting is the co-developement of the L250 :) Hello! Night and Day! :rotfl:

boputnam
09-17-2003, 10:25 AM
Originally posted by Giskard
Well, if one absolutely has to have that exponential doohicky coupled to a plastic slant plate thingamajigger then I would think the 4344 / 4345 / 4355 would be the ticket ;) What's quite interesting is the co-developement of the L250 :) Hello! Night and Day! :rotfl: Yer RIGHT! I don't see how they get it done without the exponential doohicky coupled to a plastic slant plate thingamajigger :D

But, let's get back to who Ian's sleepin' with :snore:

Ian Mackenzie
09-17-2003, 03:18 PM
Purrr,

boputnam
09-17-2003, 03:50 PM
Originally posted by Ian Mackenzie
Purrr,

:bs:

Tom Loizeaux
03-25-2004, 06:00 PM
Guys, I've read this thread with the greatest interest! Thanks to all of you.
After reading these posts on humps, dips and polarity, I went down and reversed the banana connector on one of my 4343's bass speaker inputs (I'm bi-amping these). In this "reversed" position the bass became boomy!. I put a battery on the banana pins and, in my original normal position, the 2231 and 2121 were out of phase!
I was shocked! I feel this "out of phase" position is more correct in terms of balance. Be aware that I'm running these 4343s with a Rane 24dB active crossover with no phase shift dialed in. I set the phase shift for maxium output at the crossover freq. of 250Hz, which was zero. ...wow, I'm beginning to get confused.
When I run these using my 5235, using the "optomized" cards for the 4343, with the wiring in my normal position (2231 and 2121 out of phase) am I getting proper balance?

Please can someone clear this all up?
Thanks,

Tom

boputnam
03-25-2004, 06:29 PM
Oh no... :banghead:

Without looking backwards, so I don't get confused :spin: the 3143 network is wired such that:

UHF - positive
HF - positive
MF - positive
LF - negative

Note - this is what the 3143 does, passive. And, if you've hooked-up the 5235 + to red biamped, the above also stands.

So yes, the 2231 and 2121 are out-of-phase in the 4343, by design. Sleep well, lad... ;)

Ian Mackenzie
03-25-2004, 06:32 PM
The JBL cards have been optimised with the correct drive voltage to thr 2121 & 2231. Do a search as Giskard has posted sims of this. The slope is a modified 12db slope. I think the phase of the drivers will still need to ne reverse as is the case with all 12db butterworth networks.

Now, The Rane is all pass 24 db slopes with ouputs in phase. This will not provide the right slopes for this system. The overlpa b/n the 2121 & 2231 requires some degree of equalisation to avoid a hump caused by mutual couple of the drivers, this is incorporated in the JBL cards.

The JBL crossover does the JBL but is old and dated, its has class A/B follower buffers which are not the best for sonic excellence.

I have a better crossover in the works with discrete low feedback class A buffers soon to handle this..stay tuned.

Ian

pemoobi
10-29-2006, 09:30 PM
Salve ragazzi i have the attached.
Woofer Altec could be 416a.
I don't like crossover.
Could i try the Mister Widget 4355/3155 clones?
And if, as Hiraga suggestion, woofer 600Hz with 3.0 mH and 24 uf, what happen to the other interested values?
Grazie
Federico