Discussion Thread JBL 4343 to 4344 upgrade

[Ian Mackenzie]

More experiments.....

Been listening to the stock JBL 5325 crossover today with 4345 cards that just arrived from Santa Rosa CA....thankyou SpeakerDave.

Well its been very interesting.

The good news is it's very clean sounding.

The bad news is the 5235 crossover makes every recording sound the same ....... .

A . By this I am referring to the presentation......there is a very strong sense of presence in the midrange, lots of drive.

If your JBLs sound in your face then this is why.....and ultimately fatiguing.

I think this is another long held characterisation and a false one at that of JBL's in particular the 4343 that is going to be sorted out in this project.

Basically the speakers are a hi end system and it these sort of issues that ear mark hifi from hi end.

B. I compared it to my own crossover and it by comparison sounds perhaps reserved, not in your face. Once I played different stuff the skill of the recording engineer becomes obvious. The music has soul and natural energy.

Removing the active crossover gives the same result as B with some loss of bass detail.

I will attempt the null dc offsets the discrete opamps and bypass the coupling capacitors (B) and see what happens.

I decided to completely bypass (short out) the audio coupling capacitors in a key area just to see what might happen.......

Well let me say its going to stay that way......

I will refer to this as the Earl revision to the design.

The very fine detail and nuance at frequency extremes has opened up while the mids now a sheer clarity that is difficult to describe. Individual tracks appear to take longer to play while at the same time I now feel compelled to focus on the characteristics of specific instruments.

This perhaps is a sign of one being at ease and accepting the sound as correct.... I think so.

I now propose to charge couple the polystyrene capacitors in the actual crossover filters. This will be referred to as the Giskard revision to the design.

What amazes me is that one easily can pick and hear all these refinements up on a 20+ year old loudspeaker design.

Ian

[Tom Loizeaux]

...With the slots on the side/outer the action of the crossover polar geomtry is to angle the 8K frequencies and above towards the listening in the middle.

Ian

I've always set up my 4333s & 4343s with the slots on the inside, feeling that having a direct line-of-sight to the 2405 slot is better then having some of the slant plate fins in the way. Am I mistaken?

Tom

[Ian Mackenzie]

Each to his own Tom and I would normally agree "if" all the drivers are in the same vertical plane...but not in this instance.

This my graphic below...I'm not much of an artist but there we are.

In the region of the crossover point both the horn and slot overlap and there will be a polar tilt in the direction of the arrow...its that simple. hence I prefer the slot on the outside....I recall the 4344 manual says a much somewhere.

If you put the slot above the horn some of the highs will be pointed at your ceiling!

Ian

[Ian Mackenzie]

More experiments.....

Been listening to the stock JBL 5325 crossover today with 4345 cards that just arrived from Santa Rosa CA....thankyou SpeakerDave.

Well its been very interesting.

The good news is it's very clean sounding.

The bad news is the 5235 crossover makes every recording sound the same ....... .

A . By this I am referring to the presentation......there is a very strong sense of presence in the midrange, lots of drive.

If your JBLs sound in your face then this is why.....and ultimately fatiguing.

I think this is another long held characterisation and a false one at that of JBL's in particular the 4343 that is going to be sorted out in this project.

Basically the speakers are a hi end system and it these sort of issues that ear mark hifi from hi end.

B. I compared it to my own crossover and it by comparison sounds perhaps reserved, not in your face. Once I played different stuff the skill of the recording engineer becomes obvious. The music has soul and natural energy.

Removing the active crossover gives the same result as B with some loss of bass detail.

I will attempt the null dc offsets the discrete opamps and bypass the coupling capacitors (B) and see what happens.

I decided to completely bypass (short out) the audio coupling capacitors in a key area just to see what might happen.......

Well let me say its going to stay that way......

I will refer to this as the Earl revision to the design.

The very fine detail and nuance at frequency extremes has opened up while the mids now a sheer clarity that is difficult to describe. Individual tracks appear to take longer to play while at the same time I now feel compelled to focus on the characteristics of specific instruments.

This perhaps is a sign of one being at ease and accepting the sound as correct.... I think so.

I now propose to charge couple the polystyrene capacitors in the actual crossover filters. This will be referred to as the Giskard revision to the design.

What amazes me is that one easily can pick and hear all these refinements up on a 20+ year old loudspeaker design.

Ian

After evaluating the 5235 Crossover and the earlier comparisons Ed did b/n full passive an the Ashly active crossovers I am convinced active crossovers can be the route of all Evil in attaining hi end sound quality.

The driver upgraded 4344 is quite capable of hi end sound reproduction if
only given a chance.

Sure, nice passive crossover parts refine and improve transparency but the effect of the Pro PA active crossover cannot be undone..ever....

My tests and modifications which I am yet to finalise on my own class A
active crossover confirm the level of subjective sound quality the 4344 can
provide.

Done right, an active crossover can provided pin sharp bass transients and
mid range clarity unattainable with a full passive crossover.

Done wrong and its all a pointless exercise...unless of course you prefer listening to Mid Fi.

Yes this does sound like a rant and maybe some of you already appreciate the above. I just find it very annoying that JBL never put out a better unit for these vintage monitors......its not as though they were'nt selling in Japan.

Ian

[Lancer]

I just find it very annoying that JBL never put out a better unit for these vintage monitors...

Yep...

[porschedpm]

Ian, if I hear you correctly Pro PA components may not be the best choice for someone looking to wring the last bit of musical enjoyment out of their Hi End home system. Is this because:

1) For the most part, the intended use of Pro PA quality components is different than the indended use of Hi End components. Pro PA needs to reproduce music usually at sound levels that would be unacceptably loud for most home environments. At these louder sound levels, the sound engineer is would be concerned more with accuracy, lack of distortion, room acoustics, feedback, etc. than looking for the nuances and delicacies within the music. I think both the sound engineer and the audiophile both would be looking to minimize hum but a noise level that what would be acceptable to the sound engineer would not be for the audiophile.
2) Certain of the goals of Pro PA components are achieved at the expense of the some of the goals of Hi End components.

Did JBL ever produce a Hi-End audiophile type active crossover, say for the Synthesis or K2 series.

[Ian Mackenzie]

Ian, if I hear you correctly Pro PA components may not be the best choice for someone looking to wring the last bit of musical enjoyment out of their Hi End home system. Is this because:

1) For the most part, the intended use of Pro PA quality components is different than the indended use of Hi End components. Pro PA needs to reproduce music usually at sound levels that would be unacceptably loud for most home environments. At these louder sound levels, the sound engineer is would be concerned more with accuracy, lack of distortion, room acoustics, feedback, etc. than looking for the nuances and delicacies within the music. I think both the sound engineer and the audiophile both would be looking to minimize hum but a noise level that what would be acceptable to the sound engineer would not be for the audiophile.
2) Certain of the goals of Pro PA components are achieved at the expense of the some of the goals of Hi End components.

Did JBL ever produce a Hi-End audiophile type active crossover, say for the Synthesis or K2 series.

1.Not really, the JBL BX 63 was aimed at the home user and was designed as such, so was the now defunked DX1. What's in the 5235 is ancient but well executed, the chips used in it were the order of the day however have been since outlawed from consumer CD players and pre amps because they sound bad compared to other more recently developed options.

2. I don't know........

If the truth be known I think they would be somewhat frustrated but what's done is done and water under the bridge.

[Lancer]

Did JBL ever produce a Hi-End audiophile type active crossover, say for the Synthesis or K2 series.

The DX-1 is considered to be a very good example of how to do a proper bi-amp network. JBL still uses the DX-1 for R&D. There is plenty of information about it here on the forum. The JBL M9500 and the JBL XPL200A with their specific DX-1 crossover cards are very good examples of properly bi-amped systems.

[saeman]

Ian, Lancer and other Electronic Gurus contributing to this thread - I've read a lot on the forum about custom x-overs but have seen NONE in person. JBL put everything in a neat metal box and it just screwed into the cabinet interior. All of you guys that are building custom x-overs leave me wondering what the end product looks like, how big it is and how/where they are mounted and how much room one should allow in the cabinet to mount a custom x-over. On the forum I have seen all kinds of pics of different x-overs - hugh toroidal coils, jumbo caps, circuit boards with IC's on them, etc. Does anyone have a picture that shows the end product, of a custom built x-over project, for a 4343, 4344,4350 type system - Thanx in advance Rick

[Ian Mackenzie]

Rick,

The general idea is to buy the parts build the crossover first.

However if space is a premuim the passive crossover can be build on layers.

You can assume an electronic crossover will occupy 1-2 19 inch rack unit.

Ian

[Ian Mackenzie]

If the WAF is an issue hide everything in wifey's pantry..that's what Bo does.

Ian

[saeman]

Rick,

The general idea is to buy the parts build the crossover first.

Then I was looking at the project ass backwards. I figured the x-overs were the last thing to worry about.

However if space is a premuim the passive crossover can be build on layers.

I have seen, I assume x-overs, with stacked boards so this makes sense.

You can assume an electronic crossover will occupy 1-2 19 inch rack unit.

1-2 rack units is quantatative so now I have a picture of necessary volume.

This whole idea is new to me - can't blame me for wondering. If this was a private forum all the "newbies on certain subjects" would not be cluttering up your thread with stupid questions (stupid to some I suspect).

As always, thanx for your answers.

[saeman]

Ian:

Earlier in this thread there is a pic of a mounting board that is the entire height and width of a 4343 cabinet. On it are mounted tons of coils and other caps and gadgets. Obviously it's the cross over for this monitor. So.....As a new guy on this subject - on the outside looking in - is this a typical custom x-over in size and complexity - or - is this something exotic and not what you would call a run of the mill custom x-over. This baby obviously takes up some space.

Regards - Rick

[Ian Mackenzie]

Rick,

That was an exotic approach to contruction and not absolutely necessary.

You need to decide on the drivers, then the crossover and so on.

The active crossover is an anciliary device best placed near your pre amplifier and power amps.



Ian

[Zilch]

Hi, Rick.

Assuming Ian doesn't mind me jumpin' in, here's the deal as I see it:

1) Generally speaking, an improved passive crossover can be constructed in the same space that JBL's original occupied. That would include adding bypass capacitors and aircore inductors where appropriate, as JBL did not pay much attention to space conservation in layout of early designs.

2) Further upgrading to a biased (charged-coupled) version of a standard passive crossover requires twice as many capacitors, and those capacitors are also larger than the originals. Typically, this can be accomplished in less than twice the space of the original. Stacking components and boards can reduce the footprint, but it requires knowledge and experience to get it right.

3) There are tradeoffs involved in passive crossover design and component selection. We have all seen the result of a "no compromises" approach in B&KMan's project. I believe anyone with experience building passive crossovers would characterize the effort as interesting, intriguing, even, but patently "excessive." We have yet to hear even from Jean himself whether the expense was warranted.

4) The crossovers you see here with transistors and IC's on them are "active" crossovers, a different approach in which the filtering is accomplished before the amplifiers rather than after. Being interposed between the source and amplifier, they're typically enclosed and mounted in an equipment rack rather than at or in the speaker cabinet like the passive type, which is connected between the amplifier and the individual drivers.

5) Either approach can be employed to accomplish the task, and sometimes it's a combination of both. Which is better is, well, ummm, "debatable" in nearly every instance....