JBL 4312M II 3-way Studio Monitor Review

[CamilleScholtz]

Don't change anything.. best advice
Don't even think about changing anything of you don't know what you're doing... Best of the best advice
Listen music, be happy. If no happy, change speaker

I mean that's no way to get into the hobby right

 

[dougi]

These are full size - any idea at all how good or not they are?

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A grand in UK terms and for a pair...

That is incredible value. I bought a pair locally in Oz on sale (A$6000->$3500) which I thought was OK.
They are good, but you need measurements and at least tone controls to set them up. At flat knob settings they are midrange heavy (intentional I gather as a control monitor) and designed for wall placement so need a bass lift. Once EQed I really are enjoying them and have more bass slam in my large room that my Wharfedale Heritage Lintons. Strangely, one woofer failed a couple of months in. Concerned once I determined servicing was done centrally in Sydney, they however paid and arranged for return shipping and somehow even had a spare (black for the white model here) woofer in stock.

 

[617]

So I have these speakers, and whilst the measurements might be bad, I am really in love with the looks. I'm considering upgrading the crossover, but I never did something like this. Could anyone give me some pointers?

These are some pictures I found on a Japanese blog of the crossover. I am planning on just doing away with the attenuator.

View attachment 399575View attachment 399577View attachment 399578

The current crossover points are 7kHz and 12kHz, which seem awfully high, though I have to admit I don't know anything about crossovers or audio really, I am a complete noob. Should these be lowered?

Without full 3d measurements you cannot make a better crossover, and even then it would require quite a bit of expertise.

If you want to change the sound, use equalization. There is nothing that can be improved on the inside of the speaker.

 

[CamilleScholtz]

Without full 3d measurements you cannot make a better crossover, and even then it would require quite a bit of expertise.

If you want to change the sound, use equalization. There is nothing that can be improved on the inside of the speaker.

I'm already using Dirac, which makes the speakers actually enjoyable. I was kind of planning on just slapping in a prebuilt 3-way crossover (Visaton HW 3/80 NG) which has crossover points similar to other similar sized 3-way bookshelf speakers. Considering the woofer is currently doing pretty much all the work I thought I could not get much worse? But you are saying it will definitely be worse and I should not even try?

 

[617]

I'm already using Dirac, which makes the speakers actually enjoyable. I was kind of planning on just slapping in a prebuilt 3-way crossover (Visaton HW 3/80 NG) which has crossover points similar to other similar sized 3-way bookshelf speakers. Considering the woofer is currently doing pretty much all the work I thought I could not get much worse? But you are saying it will definitely be worse and I should not even try?

View attachment 399786

Do not even try. Crossover filters don't just high pass and low pass drivers. They high pass and low pass at specific points tailored to the driver's breakup, distortion profile and directivity. They also account for the baffle step transition, diffraction effects and peaking within driver passbands. They do this while keeping the summed impedance of the speaker appropriately high by taking into account the variable impedance of each driver at every frequency. In addition, speaker drivers have dramatically different acoustic efficiencies, with different tweeters, for example, being twice as loud as others - the crossover pads them all exactly as needed.

An off the shelf crossover will do none of these things; the most egregious error will be the tonal balance being completely off due to the off the shelf model not having the proper baffle step on the woofer side and the tweeter being totally off due to it not having enough padding, or too much.

A three way speaker engineered by JBL may not have a tonal balance you like, but the directivity and distortion characteristics are probably well optimized, so even a very careful crossover redesign would have a very modest effect on sound quality. Three way speakers have smooth DI almost automatically.

 

[mhardy6647]

A three way speaker engineered by JBL may not have a tonal balance you like, but the directivity and distortion characteristics are probably well optimized, so even a very careful crossover redesign would have a very modest effect on sound quality. Three way speakers have smooth DI almost automatically.

I mean... maybe
Quoth @amirm:

Looks like Bikini Atoll at detonation.

By any standard, the 4312 M II is broken.

Maybe they designed the XO on a Monday morning -- or the day after the annual holiday party.

Fiddling with the XO might make the loudspeaker sound better on axis, even if the dispersion got worse.
Seems like one of those why not go for it? kind of cases to me.
Build 'replacement' XOs from scratch so that the loudspeakers could always be put back to factory stock condition (for resale) anon.


EDIT: There will always be a market for 'em since 1) they say JBL and 2) they have white woofers.

 

[617]

I mean... maybe
Quoth @amirm:

View attachment 400730
Looks like Bikini Atoll at detonation.

Maybe they designed the XO on a Monday morning -- or the day after the annual holiday party.

Fiddling with the XO might make the loudspeaker sound better on axis, even if the dispersion got worse.
Seems like one of those why not go for it? kind of cases to me.
Build 'replacement' XOs from scratch so that the loudspeakers could always be put back to factory stock condition (for resale) anon.


EDIT: There will always be a market for 'em since 1) they say JBL and 2) they have white woofers.
View attachment 400732

The DI is as smooth as it's going to get without designing a crossover to attenuate all those resonances with notch filters.

It could be done but you'd need so many components you'd end up shifting the port tuning when you stuff it all back in the box.