JBL 3677

General HiFi discussion, using the Tune Method to evaluate performance

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Re: JBL 3677

Post by lejonklou » 2019-10-28 09:35

It's a relief to hear that your familiar with the tune method, JH. That bodes well for your experiments.

Apparently you have an older version of the 3677. When I bought my pair a few years ago (just before they were discontinued), I bought them new. And on their filters were zero electrolytics. All the capacitors were of the yellow type on your board.

The schematic was also drastically different, as there were several resistors and I believe
three big inductors. The whole board was filled.

Perhaps you should try getting hold of one of the latest filters? Not that I know where you'd find it. As a spare part from JBL perhaps? I think you can find the schematic of it online, in case you prefer building it yourself.

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Re: JBL 3677

Post by matthias » 2019-10-28 11:02

This seems to be the technical manual with the latest specs:

http://www.jblproservice.com/pdf/Theatr ... s/3677.pdf

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Re: JBL 3677

Post by JH. » 2019-10-28 11:08

The schematic that was linked on this forum is identical to what I have. This eBay unit is the same as mine, except the electrolytics are blue that can be seen and mine are orange/black.

Can you take pictures of yours?

This is the schematic from pdf, identical to mine.

Image

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Re: JBL 3677

Post by lejonklou » 2019-10-28 11:21

I have sold my pair, so can't help you with any pictures. I do recognize that schematic, though. Hmmm. Maybe my memory is playing me tricks. Need to be really big film caps to reach 33 uF.

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Re: JBL 3677

Post by matthias » 2019-10-28 11:33

The ebay unit seems to be the same as mine.

I bought my pair new in 2016 just before they were discontinued.

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Re: JBL 3677

Post by lejonklou » 2019-10-28 13:47

Apologies, JH! I've been mixing things up in my memory. Please disregard my comments on the filter, they all seem to be the same and indeed with some electrolytics on the rear side of the board.

K400 can be found cheap second hand and if you cut off 5-10 cm in each end they show no signs (sounds) of ageing even after 20+ years. We tested various other cables for the internal wiring (and externally to the filter) and found K400 to be the best by far.

Best of luck with the modifications!

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Re: JBL 3677

Post by JH. » 2019-10-28 18:40

Thank you, I'll report back.

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Re: JBL 3677

Post by Music Lover » 2019-10-29 19:22

I have linnofils contact details if you like buying the "Ofil 3677" stands.
They makes the speakers a LOT better. I was just to write, twice as good, but no-one going to believe me... well I just did :-)
It's all about musical understanding!

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Re: JBL 3677

Post by JH. » 2019-11-01 23:38

I replaced series resistors with the MOX resistors. When I looked closer at the wiring I noticed it was tinned copper so I just twisted it and put some heatshrink towards the end to make it manageable. I cannot see any reason to replace the speaker wire, as tinned copper is perfect for the speaker.

The MOX resistors didn't change the sound a lot, but it is slightly nicer. Some music reads slightly different, a bit less dryness so it's not quite as analytical but good albums still show obvious character. For the very little money and time required it's an easy half hour of work that's worth it.

Any electolytic to film is still a ways off. I'd like to properly measure ESR of each cap first. A friend suggested the notch filter will probably be more accurate with a film replacing the 11uf electrolytic.

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Re: JBL 3677

Post by JH. » 2019-11-02 01:53

While the box is braced ok, I'm thinking from what I've read a bit of better insulation inside is advisable. I'm going to see if I can locate some denim insulation that I don't have to buy a pallets worth to get... And then look at the back of the horn to see if I can use non-hardening clay to cut any resonances from it.

While I like "tweaking" it's really nice that the speakers are superbly enjoyable without having to really do anything to them. That has not always been the case with speakers I've had.

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Re: JBL 3677

Post by lejonklou » 2019-11-02 10:47

JH. wrote:
2019-11-01 23:38
I replaced series resistors with the MOX resistors. When I looked closer at the wiring I noticed it was tinned copper so I just twisted it and put some heatshrink towards the end to make it manageable. I cannot see any reason to replace the speaker wire, as tinned copper is perfect for the speaker.

The MOX resistors didn't change the sound a lot, but it is slightly nicer. Some music reads slightly different, a bit less dryness so it's not quite as analytical but good albums still show obvious character. For the very little money and time required it's an easy half hour of work that's worth it.

Any electolytic to film is still a ways off. I'd like to properly measure ESR of each cap first. A friend suggested the notch filter will probably be more accurate with a film replacing the 11uf electrolytic.
The speaker wires can definitely be improved. There's nothing perfect about tinned copper, every model performs differently and needs to be judged by ear.

The same goes for twisting the wires - it's essential to evaluate every turn by ear, as the optimal number of twists varies from case to case. It can be anything from zero to a lot of twisting, and this makes a surprisingly big difference to the musical performance. Not so much to the sound, though.

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Re: JBL 3677

Post by JH. » 2019-11-02 17:33

Tinned copper inside speakers always sounds more musical to me. It has tone and scaling. Copper without might have more introspective but it certainly isn't in tune for me.

The twisting I might play with. But I can say most the time it doesn't do much either way when I've played with it for speakers. IC's is very different though.

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Re: JBL 3677

Post by matthias » 2019-11-04 16:32

My 3677s are stock with one exception:

Between the terminal where the crossover is mounted to and the speaker box is a thin piece of rectangular cardboard.
I removed this and found them a little bit more tuneful.

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JBL 3677 Mods

Post by Ron The Mon » 2019-11-04 21:14

JH. wrote:
2019-11-02 17:33
Tinned copper inside speakers always sounds more musical to me. It has tone and scaling. Copper without might have more introspective but it certainly isn't in tune for me.

The twisting I might play with. But I can say most the time it doesn't do much either way when I've played with it for speakers.
JH.,
It appears you have quite a bit of experience improving speaker systems. I would appreciate you making before and after recordings and sharing them with us on this thread or the "Playground" thread. I have learned quite a bit from other members here and my hi-fi has improved because of it. I'm sure I can acquire quite a bit of knowledge from you.

Have you made any YouTube videos I can watch showing your soldering techniques? I'd also be quite interested in your soldering station; what brand and model iron do you have. What temperature did you use to solder the new resistors in your crossovers and what brand and type solder did you use?

Concerning the twisting of wires, what I find most important is both left and right speakers are as identical as possible; using the same number and type of twists. I have also found twisting counter-clockwise from crossover to driver sounds best.

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Re: JBL 3677

Post by JH. » 2019-11-04 22:30

It's a bit late now for a YouTube video. Maybe I'll try that if I get into something more extensive. (My phone is pretty bad quality though, iPhone's audio is BAD)

For soldering I use Kester 44 63/37. My station is an old Weller that won't quit! There's plenty better like MetCal ($500+). I recommend something for cleaning the tip during use.

To remove the solder already on the board I used a combination of a solder sucker to get most of it. Then I cut the leads to the sandcast resistors because it's hard to pull them from the holes since the resistors are glued to the PCB. If you grab the lead with needle nose pliers, it'll cool down the solder and you won't be able to pull it. By cutting them I can just push the lead off the board with the soldering iron. Then I used some channel locks to pry the resistors off the board. After that I solder sucked what I could, and cleaned up with solder wick (I buy a larger size, usually, the tiny stuff is worthless unless you do MacBook repair or something maybe).

The heat I use varies a little but usually floats around 770F on my station. It's about as high as it can go without making the resin flow out of the solder too fast on anything that is PCB board level. But sometimes on stuff like this or binding posts you need more heat so I'll crank it up to 800F. The issue is that large stuff absorbs too much heat. What you want to avoid is trying to match solder melting temperatures as a starting point. What happens if you do that is the heat will creep heavily into everything around what you're soldering before the point you wish to solder gets hot enough for the solder to grab. You do less damage with heat by getting it up to temp quick and having the solder grab sooner. Usually you put the iron tip against whatever you're about to solder and wait a short moment, then push solder in. You can also try putting a dab on the tip and putting that dab at the joint you wish to solder, then feeding some in. There's lot of YouTube videos to watch people doing all of this.

For this crossover I used closer to 800F, those 10w resistors dissipate a good amount of heat. It took a few seconds to get the solder to grab. Overall it was a pretty easy job though. It'd be even easier if you had a desolder tool. I need a new one.

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Post by Ron The Mon » 2019-11-05 18:36

JH. wrote:
2019-11-04 22:30
It's a bit late now for a YouTube video. Maybe I'll try that if I get into something more extensive. (My phone is pretty bad quality though, iPhone's audio is BAD)
JH.,
I'd advise you to read (and listen to) the "Playground for practical listening exercises" thread here. iPhone's audio is GOOD. You can improve on any iPhone 6s or newer by using a better external microphone. The new cable Apple sells to connect headphones through the Lightning port works for external microphones as well.

A stock iPhone is all you need. It is not about ultimate quality. The idea is to compare. Before and after recordings are relative.

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Re: JBL 3677

Post by JH. » 2019-11-07 04:12

I don't understand that topic, at all. People talking about stuff I don't know how they got to or context.

iPhone sounds horrrrrid. I've tried many times. Many friends say same thing. But newer Samsungs work better. (I have an older one that makes marginally better videos that new iPhone)

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Re: JBL 3677

Post by Spannko » 2019-11-07 10:47

JH,

In a sense, you’re right. No one would ever use an iPhone to make a commercial recording. As you say, it’s not good enough.

However, the iPhone/Pad, almost unbelievably, has an ability to capture most of the important musical elements of the performance. Not to an absolute degree, but good enough. This is why the recordings are best used for comparative evaluations. Using the recordings in this way, we can say is that one recording is more or less musical than another with a reasonable degree of confidence.

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Re: JBL 3677

Post by JH. » 2019-11-07 23:43

Ok so I've done one speaker with R13 denim insulation. The improvements are very good. I'm recording before and after. Hard to say how obvious it'll be, but in person it's obvious. On a single speaker it has more bass, clearer, and less forward harshness.

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Re: JBL 3677

Post by JH. » 2019-11-08 02:43

Both done. Sounds better overall, makes you sing more. Reveals more character in some stuff for sure. Piano is much better.

This is not a shock, the insulation in it before was so thin it probably didn't do anything at all except annoy me when taking it out. (It wasn't that hard to do, just had to be done) The Ultratouch denim insulation worked excellent, very easy to do. Just used some wood glue to hold it in place, didn't stuff overly tight, covered everything that was previously covered plus the bracing directly above woofer but not on the tweeter side of that.

I have to re-record the second part, I accidentally delete the wrong one so YouTube videos are pending.

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Re: JBL 3677

Post by JH. » 2019-11-08 04:34

Btw if anyone is wondering I choose denim insulation because it has the best coefficients across the board. R13 is right thickness, thicker can cause some reflection.

A better way would be to glue on thick vinyl tile or something first, then denim. I’ll just build new cabinets before I do that. It’s beneficial but the bad insulation was problem, reducing cabinet resonances is not at the same level of 100% reflections in box.

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Re: JBL 3677

Post by matthias » 2019-11-09 11:01

JH. wrote:
2019-11-08 02:43
The Ultratouch denim insulation worked excellent, very easy to do. Just used some wood glue to hold it in place, didn't stuff overly tight, covered everything that was previously covered plus the bracing directly above woofer but not on the tweeter side of that.
How thick is the UDI R13 and is it available in Europe?
Thanks

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Re: JBL 3677

Post by JH. » 2019-11-10 04:06

Supposedly 3.5" (in) but I'm not sure it poofs up that much.

I apologize but being in the US it's really hard to search the EU anywhere. BondedLogic makes it, the product is called Ultratouch denim insulation, R13. I don't know any building supply places in the EU.

https://www.bondedlogic.com/ultratouch- ... nsulation/

I cut it with scissors but a better tool would be nice if you were going to be doing a lot with it. I also used a razor blade a little bit it kinda frays it, scissors are fairly clean. I guess the insul-knife doesn't work, foam cutter might work better.

On the big back portion I just let if fold a crease to go onto the 2x4, instead of cutting a skinny piece.

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Re: JBL 3677

Post by JH. » 2019-11-11 22:23

Playing around. I untwisted tweeter leads. I prefer that. Makes sense to me.

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Re: JBL 3677

Post by fatjulio » 2019-11-12 11:07

JH. wrote:
2019-11-08 02:43
Both done. Sounds better overall, makes you sing more. Reveals more character in some stuff for sure. Piano is much better.

This is not a shock, the insulation in it before was so thin it probably didn't do anything at all except annoy me when taking it out. (It wasn't that hard to do, just had to be done) The Ultratouch denim insulation worked excellent, very easy to do. Just used some wood glue to hold it in place, didn't stuff overly tight, covered everything that was previously covered plus the bracing directly above woofer but not on the tweeter side of that.

I have to re-record the second part, I accidentally delete the wrong one so YouTube videos are pending.
Are there clips coming? I have 3677's and think this might be good for me too.

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