Genelec 8351B Teardown (2nd Disassembled)

[Rntlee]

Not sure about them being less durable. Will they last 50 yrs, probably not. Then again who keeps speakers for that long anyway.

Hey, I resemble that remark! I have a pair of Jbl 4311’s that are approaching 50years old and the 123A’s (2212’s) in them look like and sound like new.

 

[jhaider]

That MDC coax really looks the part - huge midrange voicecoil, probably more magnet strength from that neo ring than most 8" woofers have. Given the size of the top plate I bet the coil is underhung, too.

The detail that most interests me is the inner side of the vent. In the 2nd picture looks like there's a felt (?) plug in it! Is that a solid piece, or a hollow roll?

 

[dfuller]

So Infineon chip amps? Nice.

Discrete Class D by the looks of it, but yes - Infineon. Chip amps (even class D) are relatively limited in power and distortion compared to discrete designs (note, this is more a speaker amp problem than a headphone amp) because with discrete designs you can just keep paralleling more output transistors.

Why paper
It's so much less durable

The cones are very rarely the part that fails on speakers. More often it's the suspension or voice coil. There are tons of paper cones around from 50+ years ago that still work fine. Regardless: paper is a totally fine material for woofers. Maybe it's not as pistonic in its passband as aluminum, but what is? It also has the advantage of having fairly predictable breakup modes that don't require notching.

 

[Matias]

Discrete Class D by the looks of it, but yes - Infineon. Chip amps (even class D) are relatively limited in power and distortion compared to discrete designs (note, this is more a speaker amp problem than a headphone amp) because with discrete designs you can just keep paralleling more output transistors.

Didn't they parallel 3 Infineon chip amps, one for each way (bass, mids, highs)?

 

[dfuller]

Didn't they parallel 3 Infineon chip amps, one for each way (bass, mids, highs)?

Not quite. 3 class D driver ICs, and then a high side and low side discrete MOSFET per driver IC.

 

[Jason K]

That MDC coax really looks the part - huge midrange voicecoil, probably more magnet strength from that neo ring than most 8" woofers have. Given the size of the top plate I bet the coil is underhung, too.

The detail that most interests me is the inner side of the vent. In the 2nd picture looks like there's a felt (?) plug in it! Is that a solid piece, or a hollow roll?

It's hard and it looks like it's press molded with plastic rather than sticking

 

[617]

The coax is very sexy. Thanks for the photos.

 

[jhaider]

It's hard and it looks like it's press molded with plastic rather than sticking

Are we talking about the same thing? See circled part. You wouldn't happen to have an "up the port" shot, would you?

 

[Jason K]

Are we talking about the same thing? See circled part.
View attachment 126104

Yes, I'm talking about that part too.
Rather than being mounted on a plastic vent, it is squeezed and tangled together.

I know this is to reduce the turbulence noise in the port.

 

[Jason K]

That MDC coax really looks the part - huge midrange voicecoil, probably more magnet strength from that neo ring than most 8" woofers have. Given the size of the top plate I bet the coil is underhung, too.

The detail that most interests me is the inner side of the vent. In the 2nd picture looks like there's a felt (?) plug in it! Is that a solid piece, or a hollow roll?

Looking again, the midrange looks like a shape with inner and outer surrounds, with the center of the diaphragm connected to the voice coil.

Did I understand it right?

 

[preload]

Reminds me of Bose cube construction. Paper cones, thin walled enclosures, exorbitant pricing. That being said, my 8351B's don't sound too bad.

 

[Pearljam5000]

Reminds me of Bose cube construction. Paper cones, thin walled enclosures, exorbitant pricing. That being said, my 8351B's don't sound too bad.

Saying Genelec and Bose in the same sentence is blasphemy

 

[BDE]

Not quite. 3 class D driver ICs, and then a high side and low side discrete MOSFET per driver IC.

Do you know a compareable board for DIY applications?

BTW: Any idea what DAC and DSP are used?

Best regards

 

[Jason K]

Do you know a compareable board for DIY applications?

BTW: Any idea what DAC and DSP are used?

Best regards

This is the part that comes out by opening the rear terminal panel.

 

[dfuller]

Do you know a compareable board for DIY applications?

BTW: Any idea what DAC and DSP are used?

Best regards

Well, there are the Hypex plate amps, but as far as just boards? Nope.

 

[Sebastiaan de Vries]

To OP, You are a courageous person to do this, and thanks a lot for it.

Those who are disappointed at first sight, shouldn't be—this very clever and top-notch engineering with a no-nonsense holistic approach.

Working in the ODM industry myself, I can assure you the choice of components is well-considered, and those days, not many manufactures will choose this route. On average BOM, WIMA, and Rubyocon, Wurth, etc., is very expensive.

The drivers must be costly to make, with all die-cast tailored chassis. The coaxial is a masterpiece by the looks of it. Beautiful (die-cast) basket, massive neodymium magnet, and voice coil. That might explain the excellence and clarity of the mid/high range. I remember KEF only utilize neodymium magnets in the uni-q drivers for the Blades but not for the reference-line.

The Infineon gate drivers are decent for solid and robust Class-D amplifier design. I would wish/hope Genelec applied some post-filter feedback (PFFB) scheme, which is possible with some work-around. But perhaps this is my wishful thinking on my part, but who knows..

Last interesting part, those "ribs" in the woofer surrounds on the sides. I guess similar in philosophy to the Purifi PTT6.5W04 woofers to battle cone-surround distortion.

What does concern me a little bit is the tearing? of the woofer cones?

 

[Sancus]

Reminds me of Bose cube construction. Paper cones, thin walled enclosures, exorbitant pricing. That being said, my 8351B's don't sound too bad.

Haha. They should make a "weird audiophile edition" that just doubles the thickness of the cabinets, switches to aluminum drivers and beryllium tweeter, and upcharge $3K for it. Sound will of course be worse but that's fine.

 

[preload]

Haha. They should make a "weird audiophile edition" that just doubles the thickness of the cabinets, switches to aluminum drivers and beryllium tweeter, and upcharge $3K for it. Sound will of course be worse but that's fine.

I'd pay $3k more for that! Those paper oblong woofer cones remind me of 6x9" car audio speakers selling for $29.95 at Circuit City in the 90's.

 

[Sebastiaan de Vries]

I'd pay $3k more for that! Those paper oblong woofer cones remind me of 6x9" car audio speakers selling for $29.95 at Circuit City in the 90's.

I guess you listen with your eyes, and even so, they are still uniquely hidden behind the slots.

I suggest take a closer look. This are pretty neat woofer designs.

1: Note the baskets. This aren’t common stamped steel designs, but open-frame (CNC-Ed?) chassis.

2: Look at the surround design, where they added ribbles to th sides to reduce distortion. I think there is a lot more into this woofer design than first impression might suggest.

 

[Sancus]

I guess you listen with your eyes, and even so, they are still uniquely hidden behind the slots.

I'm pretty sure he is joking btw, since he owns them

Maybe @Ilkka Rissanen would have something to say about the woofer tears though, if that's a cosmetic thing that isn't important, or actually a problem that shouldn't be there?