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Genelec 8351B Teardown (2nd Disassembled)

q3cpma

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OK so if I understand correctly the LF driver comes off the production line looking exactly like the one in the OP (even before it is installed in a monitor), with the rough ridges in the diaphragm.

I found this video where at 2:58 we get a glimpse of a bunch of what look like 8331A racetrack drivers:

View attachment 163889

A few seconds later we see a close-up of a bigger racetrack drive, probably 8351A as it doesn't have the rubber surround with the corrugated sides:

View attachment 163890

In both of these images the diaphragm doesn't have the rough area, in fact, it looks perfectly smooth all around, unlike the driver in the original post:

View attachment 163817

I'm having trouble understanding why the top and bottom parts of the perimeter would have the rough finish, but not the sides. I still see cracked paper, sorry. If other parts of the perimeter can be smooth, I really don't see why the top and bottom can't be smooth. The diaphragm is a wet-pressed moulded pulp component. I am 99.999% sure the mould is perfectly smooth at that spot and so when the diaphragm comes out of the mould it is also perfectly smooth all around. I have seen plenty of wet-pressed moulded pulp packaging that has very intricate details and the finish is exceedingly smooth.

Also, the rough area seems to be angled in a way that follows the shape of the the diaphragm slope (see angled white lines in above image) and it only affects about 80% of the length of the top and bottom parts, respectively, which suggest a mechanical correlation between the tears the geometry of the diaphragm. I understand that the rubber surround is supposed to be the bit that flexes while the diaphragm is stiff and ideally doesn't deform; however, in this particular case, it appears the diaphragm is in fact flexing more than it should under a cyclic load which causes the tears.

I get what said about accelerated lifetime testing, and I believe it is a reliable way to test if properly implemented. I used to work in test development myself. I just have trouble believing the racetrack drivers are assembled with the tears in the paper.

I still think a picture speaks a thousand words and the best way to settle this and prove me wrong (which I would be infinitely grateful for) is to show us a picture of several brand-new and unused 8351B racetrack drivers from the assembly facility. If they have the micro tears like the one in the OP I will have made an ass of myself but I will also be able to put my mind at rest and order a pair of 8351Bs + subs, which was my original intention and the one I would like to go with. If, on the other hand, the brand-new drivers are smooth, then perhaps they might need reviewing, which is fine by me because these monitors are out of stock everywhere and I will have to wait till spring 2022 to buy anyway.

Sorry to be such a huge and persistent pain!
Thanks for your investigation, and I'm with you, we didn't get an answer about "why" it's supposed to look that way. The way the surround is affixed to the cone looks very different though (the cone making a roll before the actual surround in the B version), and could be the reason behind this "by design" fibre breakup.
 

Pearljam5000

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Well there are a lot of Ones owners here, maybe they could add some info about this
 

Scoox

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Thanks for your investigation, and I'm with you, we didn't get an answer about "why" it's supposed to look that way. The way the surround is affixed to the cone looks very different though (the cone making a roll before the actual surround in the B version), and could be the reason behind this "by design" fibre breakup.

Yep, I did spot that too but forgot to mention it. The drivers I saw in the video are from pre-8351B monitors with the smooth rubber surround and the diaphragm with no "bump". I don't think the corrugated rubber has anything to do with the tearing, I think it's the new diaphragm design that might be the culprit. What in the 8351A used to be a flat surface is now a curved surface, that is, the bump. Obviously the shortest distance between two points is a straight line (ignoring relativity), not a curved line, which means in the new design there is more length of paper standing between the driver coil and the rubber surround due to the new curvature. Because longer objects deflect more than shorter ones, I imagine the ridge is in fact flexing a bit to absorb a fraction of the cyclic stresses which over time cause it do tear. That said, it is very possible that the tearing eventually stabilises, once the material is becomes thin enough. Still, seems a bit dodgy.

Well there are a lot of Ones owners here, maybe they could add some info about this

I'd be interested too. They would have to be 8351B owners though, as the "A" models are different, as q3cpma pointed out.
 

Pearljam5000

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Yep, I did spot that too but forgot to mention it. The drivers I saw in the video are from pre-8351B monitors with the smooth rubber surround and the diaphragm with no "bump". I don't think the corrugated rubber has anything to do with the tearing, I think it's the new diaphragm design that might be the culprit. What in the 8351A used to be a flat surface is now a curved surface, that is, the bump. Obviously the shortest distance between two points is a straight line (ignoring relativity), not a curved line, which means in the new design there is more length of paper standing between the driver coil and the rubber surround due to the new curvature. Because longer objects deflect more than shorter ones, I imagine the ridge is in fact flexing a bit to absorb a fraction of the cyclic stresses which over time cause it do tear. That said, it is very possible that the tearing eventually stabilises, once the material is becomes thin enough. Still, seems a bit dodgy.



I'd be interested too. They would have to be 8351B owners though, as the "A" models are different, as q3cpma pointed out.
Unfortunately no one replied yet.
I also wonder if the 8361A has this issue or just the 8351B, but it's much less common so I doubt anyone would take them apart.
 

Scoox

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I also wonder if the 8361A has this issue or just the 8351B, but it's much less common so I doubt anyone would take them apart.

Good question. Were you considering the 8361A? If this turns out to be an issue I'm sure Genelec will be onto it soon enough.

My original plan was 2x 8351Bs + 2x 7360A (subs purchased separately probably a year later due to budget constraints), but recently I also considered the possibility of getting 2x 8331A + 2x 7350A which I would be able to purchase immediately including the subs. Ignoring SPL, do the 8351Bs sound that much better than the 8331As once you add subs? Since the 8331A uses the old racetrack driver, at least I wouldn't have to wait for Genelec to take care of the torn paper problem should the issue be acknowledged. Again, let's wait for Ilkka to comment.
 

Pearljam5000

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Good question. Were you considering the 8361A? If this turns out to be an issue I'm sure Genelec will be onto it soon enough.

My original plan was 2x 8351Bs + 2x 7360A (subs purchased separately probably a year later due to budget constraints), recently I also considered the possibility of buying 2x 8331A + 2x 7350A which I would be able to purchase immediately including the subs. Ignoring SPL, do the 8351Bs sound that much better than the 8331As once you add subs? Since the 8331A use6 the old racetrack driver, at least I wouldn't have to wait for Genelec to take care of the torn paper problem should the issue be acknowledged. Again, let's wait for Ilkka's to comment.
The 8331 has the smaller mid/tweeter driver so I don't even consider getting it.
The 8361A costs not a lot more than the 8351B and since I'm not getting subs anytime soon it makes more sense to me.
 

Scoox

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The 8331 has the smaller mid/tweeter driver so I don't even consider getting it.
The 8361A costs not a lot more than the 8351B and since I'm not getting subs anytime soon it makes more sense to me.
That makes sense. I still think the 8351B is Genelec's best value speaker, hands down. If I wanted to upgrade from the 8331A I would basically skip the 8341A and save up for the 8351B. The 8361A, on the other hand, crosses the line of diminishing returns for me. An extra 2k Euro for just 2 Hz of bass extension when I can buy a 7370A sub that can reach 19 Hz for a little more money is not too appealing.

I do prefer the simplicity of a system without subs but unfortunately the material I work with uses frequencies down to 27.5 Hz which means I'll be needing the sub anyway, hence I'd rather spend less on tops and put the rest towards subs.
 

Ilkka Rissanen

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Again, let's wait for Ilkka to comment.
Hi,

I commented this question already first time in April, and several times after that. If my word is not good enough for you, unfortunately that is as far as I can go. I consider this case closed, thank you. :)
 

Scoox

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Hi,

I commented this question already first time in April, and several times after that. If my word is not good enough for you, unfortunately that is as far as I can go. I consider this case closed, thank you. :)

Thanks Ilkka. Other forum members who were considering this or the 8361A monitor have contacted me via PM and expressed similar reservations because you have given us your word but not a convincing logical explanation about this tearing which you keep telling us is a feature but not really giving us any more details. I'm disappointed that you are being so argumentative about something that could be easily clarified with a couple of close-up photos from the production line (like the ones I took from that video). If you can't take those photos yourself, I'm sure you could ask a colleague to do it for you. Considering the combined cost of this system would be over 10k Euro (including two subs), IMHO this isn't too much to ask.
 

Walter

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Hi,

I commented this question already first time in April, and several times after that. If my word is not good enough for you, unfortunately that is as far as I can go. I consider this case closed, thank you. :)
I think that is a wise decision. I have thought for several weeks that this topic is a classic example of why manufacturers are very wary about commenting on forums. I've seen this same pattern repeated several times, and not just on audio forums:
1. Poster asks a question or criticizes some element of a product or service.
2. Manufacturer's rep responds.
3. Poster is not satisfied with the answer so asks the same question again, usually in a slightly different way.
4. Manufacturer's rep responds again, with more detail.
5. Poster is still not satisfied.
6. On and on...

Sometimes it results in the original poster and any who joined in later finally accepting the answer. Usually, it doesn't. Either they want more details than the company wants to reveal, or they simply don't believe they are being told the truth, or in some cases they think they know more than the people who designed it (and in some cases they probably did). It does a manufacturer no benefit to engage in what is essentially a public argument, and unfortunately it usually ends in them being much less willing to respond in the future.

I'm not saying anyone is out of line here, just that the question has already been asked and answered to a higher degree than anyone can reasonably expect (my opinion) from a speaker company, and that Ikka is smart to stop responding.
 

Elkios

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OK so if I understand correctly the LF driver comes off the production line looking exactly like the one in the OP (even before it is installed in a monitor), with the rough ridges in the diaphragm.

I found this video where at 2:58 we get a glimpse of a bunch of what look like 8331A racetrack drivers:

View attachment 163889

A few seconds later we see a close-up of a bigger racetrack drive, probably either 8341A or 8351A as it doesn't have the rubber surround with the corrugated sides:

View attachment 163890

In both of these images the diaphragm doesn't have the rough area, in fact, it looks perfectly smooth all around, unlike the driver in the original post:

View attachment 163817

Even with my optimistic hat on, I still see torn paper, sorry. If other parts of the perimeter are perfectly smooth, I really don't see why the top and bottom can't also be smooth. I assume the diaphragm is a wet-pressed moulded pulp component. The defining characteristic and the reason for using a mould is that it is able to produce consistently identical parts, but you said the "roughness" is not exactly the same in every drive, therefore the tearing must have happened later, not at the pressing stage. Furthermore, the mould is almost definitely perfectly smooth at that spot anyway, so I'm pretty sure when the diaphragm comes out of the mould the roughness isn't there. I have seen plenty of wet-pressed moulded pulp packaging that has very intricate details and the finish is exceedingly smooth and detailed. The tears therefore must have appeared afterwards, once the diaphragm starts is put through its paces.

I notice the rough area only affects about 80% of the length of the top and bottom parts (respectively) of the diaphragm "bump". The white lines in the above image show where the smooth/rough areas end and begin. Notice also how the angel of the white lines and the sides of the triangular shadow cast by the diaphragm on itself are basically parallel, which suggests a correlation between the tearing and the geometry of the diaphragm. I understand that the rubber surround is there to absorb most of the cyclic stresses so the diaphragm doesn't have to; however, in this case, it appears the diaphragm is in fact absorbing more of those cyclic stresses than it can take, which leads to tearing.

I get what said about accelerated lifetime testing, and I believe it is a reliable way to test if properly implemented, but it's still an imperfect approximation. I used to work in test development myself, so I know a bit about testing. I just have trouble believing the racetrack drivers leave the assembly line with the tears in the diaphragm.

Anyway, I think the best way to settle this and prove me wrong (which I would be infinitely grateful for) is to show me a picture of several brand-new and unused 8351B racetrack drivers side-by-side from the assembly facility. If they have the micro tears like the one in the OP I will have made an ass of myself but I will also be able to put my mind at rest and order a pair of 8351Bs + subs, which was my original intention and the one I would like to go with. If, on the other hand, the brand-new drivers are smooth, then perhaps the product needs reviewing, which is fine by me because these monitors are out of stock everywhere and I will have to wait until spring 2022 to buy anyway.

Regarding the warranty, I will contact support with my suggestions, thanks :)

Sorry to be such a huge and persistent pain!
Hey dude my 8341s have this . It has not changed since purchased 3 years ago . The top images look blurry around the edge maybe so people don't fall to peaces over it . I have seen two other pair's very similar. I have regularly hit Genelec up with support questions and the service is first rate. If you look at other driver manuefactures web sites quite a few have rough coned drivers.
 

Scoox

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Hey dude my 8341s have this . It has not changed since purchased 3 years ago . The top images look blurry around the edge maybe so people don't fall to pieces over it. I have seen two other pair's very similar. I have regularly hit Genelec up with support questions and the service is first rate. If you look at other driver manuefactures web sites quite a few have rough coned drivers.

OK we are getting somewhere :) I know it's probably a bit difficult to see much but would you be able to take a picture of your LF driver(s) rough spot, ideally both drivers and both monitors if possible, to see what it looks like? Obviously I mean without taking apart the cabinet, just looking into the slot from the outside. That'd be very insightful.

Re. their support it is very good—never had any complaints before and I've contacted a good number of times.

Re. the top images looking blurry around the edges, I think that's just because the camera was focused on the centre of the view, I really doubt it was intentional.
 
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YSC

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OK we are getting somewhere :) I know it's probably a bit difficult to see much but would you be able to take a picture of your LF driver(s) rough spot, ideally both drivers and both monitors if possible, to see what it looks like? Obviously I mean without taking apart the cabinet, just looking into the slot from the outside. That'd be very insightful.

Re. their support it is very good—never had any complaints before and I've contacted a good number of times.

Re. the top images looking blurry around the edges, I think that's just because the camera was focused on the centre of the view, I really doubt it was intentional.
LF close.png


just watched the video and when it zoomed really close up, right before it changes to another scene, I can see those "torn paper" type of pattern. it's likely the lower res of the video camera, which is somehow minutely moving a tiny bit, and the aliasing filter of the camera sensor which averaged out and removed the texture due to noise reduction algorithm.
 

changer

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Thanks Ilkka. Other forum members who were considering this or the 8361A monitor have contacted me via PM and expressed similar reservations because you have given us your word but not a convincing logical explanation about this tearing which you keep telling us is a feature but not really giving us any more details. I'm disappointed that you are being so argumentative about something that could be easily clarified with a couple of close-up photos from the production line (like the ones I took from that video). If you can't take those photos yourself, I'm sure you could ask a colleague to do it for you. Considering the combined cost of this system would be over 10k Euro (including two subs), IMHO this isn't too much to ask.
Sir, with all due respect: This is a world market champion in studio monitor technology, with stiff competition, and you are basically asking them to reveal their manufacturing procedure. It is a clear case for any major company not to disclose their secrets and the questions posted here since the initial explanation could easily qualify as an attempt in industrial espionage. If a designer of a world class speaker ensures you that his product is not faulty, and they even offer extended warranty which would cover such failures, it could be wise to believe the professional and let it be.
 

Scoox

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Sir, with all due respect: This is a world market champion in studio monitor technology, with stiff competition, and you are basically asking them to reveal their manufacturing procedure. It is a clear case for any major company not to disclose their secrets and the questions posted here since the initial explanation could easily qualify as an attempt in industrial espionage. If a designer of a world class speaker ensures you that his product is not faulty, and they even offer extended warranty which would cover such failures, it could be wise to believe the professional and let it be.

I'm not asking for the Coca-Cola formula here, I'm only asking for one or two clear photos of a feature that any person who owns this monitor brand-new could easily check themselves and share online, and that's perfectly legal and doesn't reveal any details about the manufacturing process or the underlying engineering. If there was a store near me that carried these monitors, I would have taken a look myself.
 

ivity

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It seems to me, that with such serious doubts/suspicions as yours, maybe it's better.....just not to buy Genelecs and pay attention to other brands.
 

Scoox

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View attachment 164139

just watched the video and when it zoomed really close up, right before it changes to another scene, I can see those "torn paper" type of pattern. it's likely the lower res of the video camera, which is somehow minutely moving a tiny bit, and the aliasing filter of the camera sensor which averaged out and removed the texture due to noise reduction algorithm.

Actually, it didn't zoom in really close up at all, and I can't see any "torn paper" in the video. If anything, it looks very smooth. But you could be right. The point is, a high-res image showing the detail of several drivers side-by-side would settle the case.
 

Scoox

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It seems to me, that with such serious doubts/suspicions as yours, maybe it's better.....just not to buy Genelecs and pay attention to other brands.

Do you happen to own the product being discussed though?
 

changer

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The usual way for such requests is to write an email and wait. This forum might offer the opportunity to publicly interrogate an engineer of a world market leader and try to enforce a preconceived answer level, but it does not mean that the possibility alone enobles one to do so or even expect such a strategy to succeed. I'd recommend you to return to the more private and humble way of the usual (would be!) customer request via individual communication, instead of beleaguering this thread and casting doubt, as anyway, and you may have noted it already, the professional already indicated that he "considers this case closed" ...
 
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