JBL 3677

[ThomasOK]

Let me preface this by saying that I really know next to nothing about loudspeaker design. I might have some ideas having heard what works and what doesn't over the years but even there the main thing thing I have learned is that there seems to be no such thing as "one speaker to rule them all". Isobarik loading, infinite baffle and ported designs have all made quality music. I do tend to agree with Music Lover in that I am not a fan of 5 way designs as simplicity does seem to be a rule that applies to all the best Hi-Fi equipment. But there is also the quote that any device should be as simple as possible as possible but no simpler. In the world of loudspeakers this seems to mean the if you want full range performance you basically need to go three way. The fact that you will need a subwoofer with the 3677s if you want the lowest bass indicates that this is still the case with this speaker.

Which brings me to the reason I started this post. Despite the size of the woofer in the 3677 it is not ever going down to 20Hz effectively if my understanding is correct. The size of a woofer is only one part of the equation as to how low it will go and is important as it governs how much air it can move. But as important is how low the driver is designed to go and the answer for the 2035HPL driver in the 3677 is not very low. That driver's free air resonance is in the neighborhood of 45Hz to 48Hz depending on which specs you read. This means that its response falls like a stone below that point. By port loading it as the 3677 design does you can use the resonance of the ports to extend that a bit. I believe the ports in the 3677 are tuned to 40Hz so around there or a touch lower is about as low as they are going to effectively go. While JBL doesn't provide frequency graphs on the 3677 they do on the 4638 which uses two of these drivers with similar porting. Its low end frequency is claimed as -3dB at 45Hz and -10dB art 30Hz. In the frequency response graphs for it you can see that this is pretty accurate with it being down about 18dB at 20Hz, 20dB at 30Hz, 3dB down pretty close to 45Hz (the graph isn't very high resolution so it could be 46 or 47Hz) and about 6dB down right near 40Hz. Normally 6dB down is about as low as is considered usable as it is one quarter power. There might be a little lift from the close wall placement but I don't expect it would help this very much. Considering the free air resonance a larger cabinet will not effectively allow it to go lower - it it just how the driver is designed.

When a company designs a woofer they have a number of things to take into account to make it work. To make a driver go lower you have to lower the resonance of the unit. This can be done by making the driver itself more massive and/or by making the suspension softer or looser. But if you make it more massive you also make it slower and making a softer suspension can also have the same effect as it doesn't restore the cone as quickly. My guess is that this driver was designed for this specific theater application where it was expected to be augmented with one of their subwoofers as jajo has done. The other design objective was to deliver the rest of the frequency range with just two drivers to keep the cost down. The 2035H series was therefore designed to go up to 1.2kHz - an unusually high frequency for a 15" driver indeed. To be able to do this it has to be light and fast which pretty much eliminates the ability to also go really low. However, this has a theoretical big advantage, which is probably part of the reason for the reported good sound, in that it covers pretty much the entire human singing vocal range. From what I've read this runs from about 65Hz for some of the lowest bass male voices to about 1280Hz for the highest note of a female coloratura soprano. Now there are some singers who can actually hit a higher note but it is more of a whistle than a normal note at this point. It has been the stated objective of a few speaker designers I have seen to not have a crossover in the vocal range and it seems JBL have pretty much done it with this deriver - interesting.

Anyway, just thought I'd post some thoughts on how this driver appears to work and why there is likely a benefit to its design. In studying up on this I also found that there are actually two versions of this bass driver. The 2035H and the 2035HPL. It appears that they both use the same basket assembly, cone and magnet as common parts help to keep manufacturing costs down. But at least one source indicated that the 2035HPL, which is the one used in the 3677, is a lower priced version with an aluminum voice coil and some material applied to the cone for the main purpose of matching the mass of the 2035H which uses a copper voice coil. This gives them the same basic specs so they should be able to be used interchangeably. My guess is this doping material is why some of the photos of the 3677 I have seen have a darker cone in the center than at the outside. Interesting to note that the full designation for the driver now used is 2035HPL-1, so likely an update denoted the same way Linn does. I expect they changed how they apply the doping so the cone has a more uniform look. All this also begs the question of whether the 3677 would perform even better with the 2035H installed. I believe the two drivers do have the same, or at least very similar specs for free air resonance, efficiency and frequency extension so it is possible you could just swap out the drivers with no other changes. Yet another avenue for possible experimentation.

[Linnofil]

Linnofil,
what is the price for a pair of your superb looking 3677 stands?

Thank you Matthias! Right now they have an introductory price of 5500SEK + shipping. (€580/$650) They are bespoke handmade stands with all details, including spikes made in-house. Powder coated in black as standard. I don't know how much interest there is in these stands. But let me know if you are interested here or by pm. (This applies to all that are interested.) Right now there are some final tests to do before the design is final. (If there ever is such a thing as a final design.)

[Music Lover]

The pros and cons of the two bass versions have been discussed in the "3677-owner group".
Based on jajo's experience they need 4-6months 24/7 burn-in, so evaluation going to take some time.
The bass cones on my 4weeks old 3677's are moving less than 1mm at volume 70...
Stiff, you BET :)

[ThomasOK]

Where is the 3677-owner group? Is it in English?

[lejonklou]

Thank you for a great post, Thomas!

I am also very much a beginner when it comes to loudspeaker design and in addition haven't seen nearly any data on the 3677 apart from the crossover (which ML found pretty quickly) and some speculation on forums.

Those copper and aluminium voice coil versions of the woofer sound interesting. Too bad JBL don't seem very good at sharing detailed information and it also seems difficult to order specific parts and drive units. As the brand is heavily copied I think it's wise to stick to original parts.

As you found Fs of the 2035 bass unit, did you also find Qts? Doesn't that pretty much determine how low we can make it go? Without adding eq, that is.

In any case, while it's obvious that 2035 is not suited for reproducing low bass, it does have an impressively detailed and expressive bass, just as it is. There are just no sub frequencies present.

[Music Lover]

Where is the 3677-owner group? Is it in English?

It's a small number of very old friends. Recently, the main subject is 3677-tuning as most of us invested in a pair.
All of you going to read about our findings in this thread.

[ThomasOK]

Here are the driver specs I found in one thread on the 2035H:
: : The SD, Xmax and Le are JBL specs.

: : JBL 2035H
: :
: : SD= 0.088m
: : Xmax= 7.11mm
: : Le= 0.25mH
: : Measured Re = 4.1 Ohms (JBL spec 3.9 )
: : (Driver Re measured with a Fluke 87)

: :
: : JBL LAUD Praxis

: : Fs 48.0 44.84 44.964 Hz
: : Qes 0.36 0.379 0.38
: : Qms 5.0 4.469 4.834
: : Qts 0.34 0.349 0.352
: : Vas 140 172 171.2 Liters
: : Bl 16.6 16.026 16.07 T*m
: : Cms *** 148.9 147.9 mN
: : Mms 85 84.637 84.68 grams
: : eff 4.13 3.942 3.942 %
: : SPLsen *** 98.o 97.95 dB SPL @ 2.84Vrms

The above is a comparison of JBL specs vs. measured results using two different software programs: LAUD and Praxis. As you can see the Qts is pretty much 0.35.

I believe the specs are basically the same for the 2035HPL. I haven't been able to find anyone selling the 2035H driver. The spec sheet for the 4638 bass box shows it using two of them but the document is from June 1997 so not exactly up to date. This spec sheet is where they had the frequency response curves. It may be that the HPL replaced the original 2035H and they don't make the original any more.

JBL is definitely not particularly helpful. I have left a couple of messages for their Pro Cinema salespeople and have received no return call. Also some spec sheets, like the 4638, are very detailed and others, the 3677, are much less so. As you can see they also don't exactly update them very often.

[John]

Let me preface this by saying that I really know next to nothing about loudspeaker design. I might have some ideas having heard what works and what doesn't over the years but even there the main thing thing I have learned is that there seems to be no such thing as "one speaker to rule them all". Isobarik loading, infinite baffle and ported designs have all made quality music. I do tend to agree with Music Lover in that I am not a fan of 5 way designs as simplicity does seem to be a rule that applies to all the best Hi-Fi equipment. But there is also the quote that any device should be as simple as possible as possible but no simpler. In the world of loudspeakers this seems to mean the if you want full range performance you basically need to go three way. The fact that you will need a subwoofer with the 3677s if you want the lowest bass indicates that this is still the case with this speaker.

Which brings me to the reason I started this post. Despite the size of the woofer in the 3677 it is not ever going down to 20Hz effectively if my understanding is correct. The size of a woofer is only one part of the equation as to how low it will go and is important as it governs how much air it can move. But as important is how low the driver is designed to go and the answer for the 2035HPL driver in the 3677 is not very low. That driver's free air resonance is in the neighborhood of 45Hz to 48Hz depending on which specs you read. This means that its response falls like a stone below that point. By port loading it as the 3677 design does you can use the resonance of the ports to extend that a bit. I believe the ports in the 3677 are tuned to 40Hz so around there or a touch lower is about as low as they are going to effectively go. While JBL doesn't provide frequency graphs on the 3677 they do on the 4638 which uses two of these drivers with similar porting. Its low end frequency is claimed as -3dB at 45Hz and -10dB art 30Hz. In the frequency response graphs for it you can see that this is pretty accurate with it being down about 18dB at 20Hz, 20dB at 30Hz, 3dB down pretty close to 45Hz (the graph isn't very high resolution so it could be 46 or 47Hz) and about 6dB down right near 40Hz. Normally 6dB down is about as low as is considered usable as it is one quarter power. There might be a little lift from the close wall placement but I don't expect it would help this very much. Considering the free air resonance a larger cabinet will not effectively allow it to go lower - it it just how the driver is designed.

When a company designs a woofer they have a number of things to take into account to make it work. To make a driver go lower you have to lower the resonance of the unit. This can be done by making the driver itself more massive and/or by making the suspension softer or looser. But if you make it more massive you also make it slower and making a softer suspension can also have the same effect as it doesn't restore the cone as quickly. My guess is that this driver was designed for this specific theater application where it was expected to be augmented with one of their subwoofers as jajo has done. The other design objective was to deliver the rest of the frequency range with just two drivers to keep the cost down. The 2035H series was therefore designed to go up to 1.2kHz - an unusually high frequency for a 15" driver indeed. To be able to do this it has to be light and fast which pretty much eliminates the ability to also go really low. However, this has a theoretical big advantage, which is probably part of the reason for the reported good sound, in that it covers pretty much the entire human singing vocal range. From what I've read this runs from about 65Hz for some of the lowest bass male voices to about 1280Hz for the highest note of a female coloratura soprano. Now there are some singers who can actually hit a higher note but it is more of a whistle than a normal note at this point. It has been the stated objective of a few speaker designers I have seen to not have a crossover in the vocal range and it seems JBL have pretty much done it with this deriver - interesting.

Anyway, just thought I'd post some thoughts on how this driver appears to work and why there is likely a benefit to its design. In studying up on this I also found that there are actually two versions of this bass driver. The 2035H and the 2035HPL. It appears that they both use the same basket assembly, cone and magnet as common parts help to keep manufacturing costs down. But at least one source indicated that the 2035HPL, which is the one used in the 3677, is a lower priced version with an aluminum voice coil and some material applied to the cone for the main purpose of matching the mass of the 2035H which uses a copper voice coil. This gives them the same basic specs so they should be able to be used interchangeably. My guess is this doping material is why some of the photos of the 3677 I have seen have a darker cone in the center than at the outside. Interesting to note that the full designation for the driver now used is 2035HPL-1, so likely an update denoted the same way Linn does. I expect they changed how they apply the doping so the cone has a more uniform look. All this also begs the question of whether the 3677 would perform even better with the 2035H installed. I believe the two drivers do have the same, or at least very similar specs for free air resonance, efficiency and frequency extension so it is possible you could just swap out the drivers with no other changes. Yet another avenue for possible experimentation.

Wouldn't that be the case with most every two-way loudspeaker? My two way ATC loudspeakers cross over at 2.5kHz, my two way 10 inch Tannoys at 1.5kHz and two way 15 inch Tannoys at 1.1kHz.

[ThomasOK]

Wouldn't that be the case with most every two-way loudspeaker? My two way ATC loudspeakers cross over at 2.5kHz, my two way 10 inch Tannoys at 1.5kHz and two way 15 inch Tannoys at 1.1kHz.

I expect that most two ways do tend to cross over there or above as most tweeters can't go much below 1kHz. It is just unusual to see a 15" driver crossed over that high. I was not aware that the Tannoy 15" units were up there having little experience with them. But the 15" driver used in larger ATC three ways crosses over at 380Hz and I think the largest driver they use in a two-way is a 6" unit.

[John]

I think it's the difference between 2 and 3 way speakers. I noticed the older Klipsch Heritage 3-way speakers with 15 inch woofers also crossover in the vocal range.

La Scala - 400 HZ
Cornwall - 800 HZ
Klipschorn - 450 HZ

[ThomasOK]

Look what just showed up earlier today!

[lejonklou]

Very exciting, Thomas!

I can report that today we (mostly Christian, to be honest) are doing tests on the passive filter and so far we have ended up with the original as the most musical configuration.

Seems like someone has actually listened carefully when developing these speakers!

[tokenbrit]

I was going to wait for news from Thomas, and from this thread, before buying a pair of JBLs to get a better sense of what was involved in improving them... it's proving more & more difficult to resist buying a pair & sitting them in the basement to break in! I need to work out how I can sneak them by Mrs toke, and what to do for stands. It looks like it will take a big car to drive them up to Ann Arbor for Tom's magic touch assuming the rewiring benefits from optimal solder & soldering temps.

[ThomasOK]

Sneaking them by might be a difficult task. The cartons are quite large and heavy at 90lbs each packed. (I was going to say enormous but then I have uncrated truly enormous speakers and these don't quite compare). They are still in the boxes as I have other tasks that take precedence. However I unpacked one with an injured carton (the speaker was fine) and I have to say the photos give you no idea just how homely these beasts are! Back in the box for now.

There are wood crossover boxes and banana jacks on the way. I also built some 2.48m K400 and 1m split K400 and have some pieces for the internals so I'm good on wiring. Waiting to find out about the final stand version from Linnofil. I have an interesting idea for how to burn them in. This should be fun!

[tokenbrit]

General question: is there a particular reason for wooden crossover boxes? I already have enough different wood finishes between the tv stand, the hi-fi rack, and the LP12... If they're going to sit within 1m of the power amps, it'd be nice if they were in a metal case on a shelf in the main rack...
Fredrik, any thoughts of installing them in Lejonklou casework?
Tom, will yours be in movingui to match your LP12? ;)

On the subject of speaker cable, is there benefit to keeping the 2.48m as K400 from crossover out to the JBLs, rather than splitting into 2 x K200?

[ThomasOK]

Wooden boxes are what the Klangedang T1 uses. The designer says that you don't want any metal near the crossover. I suppose because of the energy going through big inductors there might be some magnetic interaction. christian has said they have stayed away from metal to the point of glueing, rather than screwing, the crossovers into the box. No Movingui at the moment - I found some quite inexpensive Basswood boxes on amazon that look good, at least for starters. But you never know! Movingui or Sitka Spruce could be used in the future!

As far as I know nobody has actually tried split K400 vs. single K400 for the 2.48m runs (although somebody could have tried it and I just haven't heard). I had some slightly longer scraps so I made a pair of 2.48m K400. But I have several sets of 2.48m split K400 so I'll find out sooner or later.

[matthias]

I have three questions:
Which lenght of K400 is the best INSIDE the 3677?
Which type of female bananas should be used at the terminal of the 3677?
What do the experts think about a Speakon connection at the terminal of the 3677 and at the output of the crossover box?

Thanks

Matt

[lejonklou]

I have three questions:
Which lenght of K400 is the best INSIDE the 3677?
Which type of female bananas should be used at the terminal of the 3677?
What do the experts think about a Speakon connection at the terminal of the 3677 and at the output of the crossover box?

Hi Matthias!

I have no idea about the optimal length inside the speaker. It will most likely have to be ignored, because there is a lot of stiffness and tension in K400, so to get a reliable connection between drive units and terminal, one will need to use the length that fits.

If female bananas are to be used, Deltron 563 sounds very good. I have compared a bunch of alternatives (including expensive ones from WBT which many audio companies use) and most musical was the cheap Deltron 563.

I don't know the exact musical performance of Speakon connectors, but I am sceptical of the four way versions I have briefly tried in the past. Right now I'm evaluating three way mains Speakons, the models that are not silver plated (silver just never seems to work, I will at some later point tell you about some mad experiments I've made). But those would require two, which is a shame. Better with a four way connector. But for now, I will stick with bananas for my 3677, because their performance is proven.

[lejonklou]

I have to add:

One doesn't have to remove the filters from JBL 3677. With proper installation, they sound fantastic with the filter in its original position.

I have yet to hear the effect of moving them out and rewiring internally with K400.

[beck]

In my system the splitting of K400 leads to out of tune music when still using bi-wire configuration. I wish I could go back.

[matthias]

In my system the splitting of K400 leads to out of tune music when still using bi-wire configuration. I wish I could go back.

Why not using the musically superior single-wiring?

Matt

[beck]

Yes, that I have tried on and off a couple of times but it does not agree with my musician ear. With single wire I also cannot tell when the musicians on a recording (analog) is in or out of tune with each other!
I know I am out of sync with most people on this forum in this matter but that is what I hear.

For me bi-wire (tri-wire) in connection with old Linn gear is the way forward (maybe even old fasion active). This allows me to enjoy the music the same way as when I play myself.

[matthias]

Right now I'm evaluating three way mains Speakons, the models that are not silver plated (silver just never seems to work, I will at some later point tell you about some mad experiments I've made).

Fredrik,

do you mean the Neutrik powerCON TRUE1 series?

Matt

[lejonklou]

do you mean the Neutrik powerCON TRUE1 series?

PowerCon, yes. But not TRUE1. Haven't seen them or know how they differ.

[matthias]

do you mean the Neutrik powerCON TRUE1 series?

PowerCon, yes. But not TRUE1. Haven't seen them or know how they differ.

The powerCON TRUE1 is a connector with breaking capacity (CBC), i.e. it can be connected or disconnected under load or live.
AFAIK, the normal PowerCon is silver plated, some types of the TRUE1 are not.

http://www.neutrik.co.uk/en-uk/powercon/powercon-true1/

Matt