JBL 4367: Inside Photos/Video

[amirm]

If you mean this:

The capacitor and resistors create a high-pass filter with a corner frequency of around 1.5 Khz (I ignored the D2 impedance for this). There is also a voltage divider of R1 and R2 but hard to say what that does without knowing the impedance of the D2 driver.

It is possible this is there also to keep the amplifier from oscillating due to impedance of the D2 by itself. Or a safety measure.

You could build this easily as it is.

 

[dallasjustice]

If you mean this:

View attachment 10264

The capacitor and resistors create a high-pass filter with a corner frequency of around 1.5 Khz (I ignored the D2 impedance for this). There is also a voltage divider of R1 and R2 but hard to say what that does without knowing the impedance of the D2 driver.

It is possible this is there also to keep the amplifier from oscillating due to impedance of the D2 by itself. Or a safety measure.

You could build this easily as it is.

That's what I'm talking about. I imagine that a similar network is inside the passive crossover inside the 4367 speaker. It looks like it also serves as protection. Do you think I could still connect the D2 to my ahb2 amp without such a network in between the two? Of course, I'd need to be careful to adjust the amp's gain downward to make up the difference between drivers. The High Pass filter is not a big deal. I always include such a filter in my linear phase target curve anyway.

 

[amirm]

I am scared purple for you doing this work. If you could at all, I would put a non-polarized capacitor in series with the driver to start and then remove it later.

I looked up another compression driver from JBL and this is their spec:

So they don't say at all what it does below 500 Hz.

Do you have a multimeter and can check its terminal with ohm range after you remove the crossover wires? That would give is the DC resistance so we would know better what load it is going to put on the amp.

 

[dallasjustice]

I am scared purple for you doing this work. If you could at all, I would put a non-polarized capacitor in series with the driver to start and then remove it later.

I looked up another compression driver from JBL and this is their spec:

View attachment 10265


So they don't say at all what it does below 500 Hz.

Do you have a multimeter and can check its terminal with ohm range after you remove the crossover wires? That would give is the DC resistance so we would know better what load it is going to put on the amp.

I don't think I can do that without taking the upper cabinet apart. It would be very difficult to disconnect wires from the D2.

Are you saying that the impedance could shift too low for the amp during a sweep? Once the crossover is set, the D2 would only really get 500hz-24khz. However, a logsweep may start lower than that. Most likely it would start around 300hz or so. Are you saying that's where i could do damage to my amp or driver?

 

[amirm]

I don't really know and am just going by what JBL has done. Why would they put that circuit in there if it were not for something that the driver does that the amp doesn't like? Maybe it is specific to Crown.

The amp you have has a bunch of protection circuits but if it goes into oscillations, it could damage the amp and or the driver. It is really impossible to tell.

If you do want to proceed, what you said is your best protection: absolutely making sure the volume is extremely low and going from there.

How are you getting access to the inside right now? You took the bass driver out?

 

[dallasjustice]

How are you getting access to the inside right now? You took the bass driver out?

Yes. It’s pretty easy to remove the midwoofer. But it would difficult to hook up a multi meter to the D2; sort of like laparoscopic surgery.

 

[amirm]

Could you reach in there and by feel attach two alligator clips to it?

If you are going this route at some point you are going to have wires connected to the driver, right? Just measure those before turning things on.

 

[DonH56]

A little more info in this one: http://www.jblproservice.com/pdf/VTX Series/VTX-V25.pdf

As Amir said, the network both high-pass filters to block DC and LF from the driver and attenuates the signal so it is a closer match in sensitivity to the woofer. Not sure why they'd include it with the M2, which I thought required external amps anyway? The obvious answers are to protect the driver in case of amp failure or a user glitch, and to facilitate use of two identically-powered amplifiers so the overall gain from amp input to ear is roughly the same for highs and lows. That may also help reduce hiss from the tweeter.

 

[RayDunzl]

I imagine that a similar network is inside the passive crossover inside the 4367 speaker.

Yes.

Eliminate the level control(R2-R5), biasing for dual caps (the diodes), HF boost/cut (C7-C12), and the fixed "tunings" (L1, L2, C3-C6), substitute values, and it matches.

 

[dallasjustice]

Why not just buy a pair or M2 cabs and play with them?

Starting to seem like not such a bad idea.

 

[sebackman]

dallasjustice, any chance to see if there any markings or part no on the 4367 waveguide?

The filter in the M2 is indeed part of the XO and not only an attenuator and protection cap. The digital XO is only 6db. If one is confident in the electronics you can just ditch the capacitor and use a 12db digital XO, the curves will be identical. Xo in M2 is electric 36db LP and 12 db HP and acoustic filter adds HP for the driver to give the right overlap at XO and keep phase where they want it. 4367 is 18db LP and 12db HP elelctric bythe looks of the schematics.

If you are using external correction (DSP) you can ditch the rest of the passive components in the filter. Make sure you make a house curve first with passive XO set at your liking. They are not 100% flat curve.

2430K/D2 is reverse polarity so you should connect your positive lead to negative terminal on the driver if running fully active.

I think you should always try to use the attenuator circuit as the impedance of these drivers on waveguides are not very pretty and the resistors do help. They will also bring down background amplifier noise as the drivers are have very high sensitivity (typical 110db) and noise can be audible otherwise.

I don't have the impedance of the 2430K/D2 on the 4367 waveguide but I do for the M2 with several different drivers.

Kind regards
//Rob

 

[vitalii427]

dallasjustice, any chance to see if there any markings or part no on the 4367 waveguide?

Michael sold 4367 long ago and got M2 to go full active. But I have 4367 and going to make them active. M2 not an option for me. So maybe I could be able to answer your question soon.

I don't have the impedance of the 2430K/D2 on the 4367 waveguide but I do for the M2 with several different drivers.

From 4367 Whitepaper:

Impedance: 16 Ohm (supposedly measured on 4367 horn)

 

[sebackman]

Hi vitaali427,

That would be great! Please port or PM if you find anything.

I got the first M2 spare part WG's on the market back in early 2015 so maybe the 4367 WG's can be sourced.

Attached is the impedance of a brand new D2 on the M2.

Kind regards
//Rob

 

[martin900]

The harman measurements look quirky, it keeps dropping from 3.5KHz on?

 

[DubbyMcDubs]

Two questions:

- Does anyone know if the 4367 parts, like the horn, are available for purchase?
- Has anyone tried using the passive crossover design from the 4367 on a DIY M2, or because of the waveguide design that is not going to work?

 

[VOVA-76]

Hello!
Sorry for my English, I use a translator.
Please tell me, how to open JBL 4367?
I could not remove the woofer, it is like glued.

 

[beatelund]

Two questions:

- Does anyone know if the 4367 parts, like the horn, are available for purchase?
- Has anyone tried using the passive crossover design from the 4367 on a DIY M2, or because of the waveguide design that is not going to work?

It is possible to order
-Horn/waveguide
-Woofer
-Tweeter

 

[gene_stl]

I don't see the point of having a 110 db efficient driver and then padding away half the power. Isn't that one of the reasons we multiamp in the first place? I had missed this thread until today but it makes me much less interested in these two systems. (Historically big JBL repeat offender) I had not previously seen an explanation of how the dual voice coil systems work in these models. Does anyone know exactly how they work? Are they push pull each transducing the same signal in opposite phase to increase the power (after reducing it with a network and throwing away amplifier damping?) OR do they each cover a particular frequency range like some manner of co-axial two way, thus needing a crossover between them. This question applies to both the compression driver and to the mid woofer.

 

[Scgorg]

I don't see the point of having a 110 db efficient driver and then padding away half the power. Isn't that one of the reasons we multiamp in the first place? I had missed this thread until today but it makes me much less interested in these two systems. (Historically big JBL repeat offender) I had not previously seen an explanation of how the dual voice coil systems work in these models. Does anyone know exactly how they work? Are they push pull each transducing the same signal in opposite phase to increase the power (after reducing it with a network and throwing away amplifier damping?) OR do they each cover a particular frequency range like some manner of co-axial two way, thus needing a crossover between them. This question applies to both the compression driver and to the mid woofer.

Having a 110dB efficient driver and then padding it down means you can get away with less compression due to heat in the VC when playing at higher levels, of course this requires the circuit used for padding to be up to the task as well, so you don't simply get heat compression there instead.

The compression drivers are in a push-push configuration where the front of the diaphragms face each other, but the phase plug and internal pathways makes them act in phase, one benefit of this is lower IMD (less movement per driver) and the heat is spread out across two voice coils rather than one, once again leading to less compression due to heating of the VC. They do not have a crossover between them.

 

[DubbyMcDubs]

I don't see the point of having a 110 db efficient driver and then padding away half the power. Isn't that one of the reasons we multiamp in the first place? I had missed this thread until today but it makes me much less interested in these two systems. (Historically big JBL repeat offender) I had not previously seen an explanation of how the dual voice coil systems work in these models. Does anyone know exactly how they work? Are they push pull each transducing the same signal in opposite phase to increase the power (after reducing it with a network and throwing away amplifier damping?) OR do they each cover a particular frequency range like some manner of co-axial two way, thus needing a crossover between them. This question applies to both the compression driver and to the mid woofer.

I guess we always trade off some technical benefits for convenience. Maybe even compatibility with more common systems.