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Doug
05-10-2003, 08:58 AM
Hello all:
I have an S8R set up ( LE 15A ,PR15A, 375, HL-93 horn/diffuser,075, LX-5 and n7000) in a Soverein cabinet (about 5 cu. ft.) I am not happy with the sound of the midrange. It is very sharp sounding, and a bit horny, not quite "hiss and spit" but close. I have been reading much about these elements and crossovers on this forum and that has encoraged me to try and replace the N7000 .(I would like to attack the LX-5 but I am intimidated by the center tapped inductor) This would mean essentially building a new one using currently available components to the original schematic. However I have read several accounts these crossovers are perhaps not the best configuration to copy. I have looked at the various schematics of other more modern JBL crossovers but did not find any that use the 375/075 complement. (perhaps that should be a clue!) Does anyone have any suggestions or should I try the existing configuration and parallel the caps with small caps like some of the later models? Experiment ?
Thanks for reading and the replys,
Doug

4313B
05-10-2003, 09:19 AM
I would probably start with installing 61098 or N14-61098 polypropylene bypass capacitors and maybe even 36168(?) bypass capacitors. At least get your system up to post L110A "standards" before making any further decisions?

http://www.jblproservice.com/forms/parts_order.html

I need to check and see what those 36168 caps really are... I think they are the polystyrene bypass capacitors but I could be wrong.

Mr. Widget
05-10-2003, 12:00 PM
"I am not happy with the sound of the midrange. It is very sharp sounding, and a bit horny..."

I may be showing my personal bias again, but I would seriously look at the HL93 as the primary source for your dissatisfaction. I would agree that the LX-5 and N7000 can certainly be improved upon also, but to my ears the family of JBL cone shaped exponential horns all exhibit this type of sound. That said it appears that there are those who like that sound.

If you find the sound a bit honky or megaphone like as I do the ultimate solution is change the horn as well as the crossover.

4313B
05-10-2003, 12:30 PM
That is definitely the nature of the beast Mr. Widget. The exponentials are definitely exponentials. When I first heard the 2344 in comparison I cried "Eureka!" There appears to be many who still like the exponential sound though...

BTW, Are you running the 2397?

Mr. Widget
05-10-2003, 02:39 PM
"BTW, Are you running the 2397?"

Yep!

And I am pretty happy with it. It is the best sounding (most natural sounding to my ears) JBL horn that I have used.

The 2344 and other CD horns require EQ so it is hard to objectively compare them horn for horn. I think that it is better to compare them as a system. In the 4430/4435 they are quite nice also.

Doug
05-10-2003, 03:43 PM
Thanks for the help gentlemen. I will let you know what I end up with and how i like it.

Doug

4313B
05-11-2003, 12:34 PM
I think everyone would like some feedback on this. The S8R is pretty classic in my opinion. Have you considered biamping and/or EQ?

Earl K
05-12-2003, 03:13 PM
Hi Doug

(a) I'd love to see a response curve of your system to help in identifying its problem. Any chance of posting one ? Do you have a RTA and digital camera ?

(b) Have you ever had the le15s & 375 compression drivers remagnetized ? If not, I'd suggest you get them done sooner than later. With the LX-5 crossover points set at around 500 hz, that H93 horn setup you're using runs unloaded from about 1200 hz on downwards. The response area of your setup uses the top end of the woofer blended with judicious amounts of "unloaded" compression driver output over this particular musical octave ( 500 hz to 1000 hz ).

- The need to remagnetize ( a practical example )

I'm running a biamped system . The crossover point is usually about 900 hz, sometimes higher, the crossover is "tunable". This point is "dialed in" between twinned le14s/le10 woofers up to 2440 drivers retrofitted with 2450sl aquaplas-dusted titanium diaphragms. The horn is a cast aluminum type made by the Brazilian company "Selenium". This horn is essentially a 2311/H93 but is 3/4" deeper because the bell mouth of the horn actually "finishes" quite flat - unlike the 2311 which abruptly terminates mid flare . Either horn ; JBL or Selenium will only provide acoustic loading for these drivers to about 1200 hz ( don't beleive the cut sheet from Selenium ). Beneath that frequency the compression driver is acting as a somewhat "stressed out" direct radiator ( certainly , above a certain volume level it'll stress-out ). Now, just yesterday I compared a newly remagged horn/driver against it's mate on the other channel. With pink noise driven into the newly magged driver, & a new crossover point of 250 hz ( & not even bypassing the DC blocking caps ) there was very good response down at 630 hz . The newly remagnetized 2440/2450 combo had no measurable db difference between 1250 & 2500 hz and only a 3.25 db down point at 630 hz from 1250 hz .
The other non-magged side ( same setup - but this time with the DC blocking caps removed ) had a response that shows 630 hz is 9 db down compared to 1250 hz. And 1250 hz is 6 db down from 2500 hz on that channel. A differential of 15 db ( 2500 hz to 630 hz )- if not compensated for in other areas of the system, should make for a virtually unlistenable system ( this is a frequency response anamoly that will definetly bite your sonic ears off ). This situation could apply to your system to some degree.
So, now, I'm waiting for 3 more large format drivers to return from being magged up before the final 6 go in .

(c) Have you had the compliance ( surrounds ) of the le15 woofers & pr15s checked to make sure they are still in spec ? The Fs of the le15 should be in the neighbourhood of 20 hz. Above 30 hz ( or below 17 hz ) and I'd get some professional attention for those le15 woofers. If the freeair resonance (Fs) of that 15" woofer has shifted upwards because of stiffening Lansaloy surrounds then the voicing of the speaker could change quite significantly. Since the cone is a mid-weight cone this change could shift upwards 1 to 3 octaves ( worst case ). Significant changes in this area wouldn't enhance your listening experience ( & that's a real understatement ).

(d) By all means update the components in those crossovers; I think the lx-5 is the main crossover to focus on , not so much the tweeter circuit. Though, I wouldn't put the mid signal through so many passive components. I'd strongly suggest biamping between the woofer & the compression driver. I'd also try using a 800 to 1200 hz point if biamping.

(e) Compliance stiffening and drivers losing magnetism are insidious changes because they occur over years if not decades. The day to day change won't be noticeable ( not like a catastrophic failure of a component ). With changes this slow, it's easy to blame a lot of things including changing musical tastes / kids / dog / cat /wife / neighbours / gov't / etc. .
" Everything but the real culprits " . :p

I hope some of this helps :)

regards <> Earl K

Doug
05-12-2003, 11:12 PM
Gentlemen:
Giskard: I will try to be good and post the results I discover. I have considered bi-amping but my budget is not currently there. I do have two amps but they are different and I have not discovered an easy way to compensate for the different outputs of each. As well they are solid state which may not be the way to go. I am driving them now (non bi-amped) with a Mccormack DNA1. Lots of juice but I don't think it is very refined. I would be interested in EQ but I do not have a meter to give me any readings. Perhaps you or some of the others might have some suggestions in this area as far as equipment recommendations and methods that are consistent. EQ'ing seems to be popular for dialing in these horn systems.

Earl K:
No I do not have an RTA, I dont know what that is either! (I'm embarassed)
I have not had the magnetism checked on the midranges, that sounds like that might be in order.
I have had the surrounds replaced on the le15's. They seem ok. I did try a 3110 crossover (800hz) but it sounded similar in the midrange. But with what you said the horn is still unloaded so perhaps that is why it did not sound better.
Updgrading the LX-5 intimidated me because of the center tapped inductor. I read with interest the previous threads on this exercise some people went through for one of the 43xx (?) monitor crossovers. It was quite involved. Perhaps I should consider biamping. The thing is my father has a pair of these speakers and I grew up with them and I don't recall them sounding this harsh but my ears are probably not what they used to be and the memories could be clouded. I will call my local repair shop and see if they do remag work or should I send them to JBL?

Thanks for the replys you two. The posts have given me some areas to pursue.

Doug

Doctor_Electron
05-13-2003, 01:40 AM
I used some 3107 crossovers (from the 4350 monitors) with 16 ohm 2440 drivers / 2380 horns (flat-front biradials), and 16 ohm 2405's. and the mids/highs sounded very nice.
These crossovers have the mid drivers running second-order high-pass from -3 Db@1200 Hz to "wide open" at their top end, and third order high pass on the 2405's, -3Db @9.5 Khz.
I agree on the use of the newer "cheeks" biradials, but for a quick try at it using your existing components the 3107's might be worth a try...BTW I had also tried using other JBL crossovers (model number not recalled, N-5000?), which rolled the 2440's off second-order, -3Db@5000 Hz / & had
high pass on the 2405's with -3Db@5000 Hz, which to me sounded horrendous. The 3107 arraingment was quite "squeaky clean" compared to those. I think the 3107's are still available "in tent" for a very reasonable price. Good Luck on this whatever you decide on, though!

Earl K
05-13-2003, 09:06 PM
Hi Doug

Here's a thread that had info about busnesses remagging in your area.
Read about it at Remagging / California (http://www.audioheritage.org/vbulletin/showthread.php?s=&threadid=95&highlight=Remag). I would remag one side at a time. One side being ; 1 x le15 and 1 x le375 . The 075 is up to you. I would also do any modifications to the crossovers 1 side at a time so you make comparisons. I don't know anything about those center-tapped autotransformers but unless it's burned out from overpowering, then I don't think there's much about it to go wrong. I'm not aware of any " old-age issues" with them . Maybe someone else could chime in if they have seen autotransformers die of old age . Caps can age and can always be "updated" with transcapping . Once you've worked you're way through these first steps I have some ideas about the 075s that doesn't involve retiring them for 077s. It involves creating a "lens" to enable them to blend somewhat better with the lens of the 375.
.
regards <. Earl K :)

gorg
04-22-2005, 11:09 AM
doug: I have been experiencing the same issue with midrange and high range from my s8r. I am wondering if you have your n7000 upgraded and I hope it resoved the issue. I am thinking to upgrade my n7000 with caps/bypassing caps and even upgrade the inductors. Thanks!:barf:

mike
04-22-2005, 03:45 PM
As some have already said this is just the character of the system you have. You may be able to change this with modifications but something like a pair of Sovereign's with S8R's is too nice, rare and valuable to modify in my opinion.

The trick to getting the best sound out of the truly vintage JBL stuff is to mate it with an amp and preamp that smooth out the "rough edges" of the speaker's sound. Most of the really serious vintage JBL collectors use either Mcintosh or Marantz tube equipment. This was the equipment that most of the really classic vintage systems were intended to be used with. My advice would be to enjoy the speakers for what they are and if you want something smoother or more transparent get newer speakers.


Mike

gorg
04-23-2005, 09:01 AM
Mike: Sure, it is obvious an option. I have to agree they are rare and valuable. Actually it sounds great for some music. I am just wondering if I can make the high a little smoother. I saw people talking about the same experience. I have a spare n7000 and would like to do some experiments of upgrading it with the new parts (caps and inductors). Is there any body has successfully done so? george :banghead:

Mr. Widget
04-23-2005, 11:30 AM
I completely agree with Mike on this one. I would suggest if you are compelled to mess around with the N7000, that you make a new one from scratch... there is plenty of info in these threads.

The suggestion of using mellower less revealing electronics may be the answer, alternatively while it isn't the "purist audiophile" solution, your speakers are very similar to the JBL studio monitors that so many on this forum love. Most of us have learned that they can be improved markedly with a little EQ help. If you use high quality external equalizers, they will allow you to tame the harshness and preserve the dynamics and life in your music.

Widget

Paul Joppa
04-23-2005, 12:21 PM
Just a few comments here, mostly theoretical.

The 075 has more low end capability than the slot (or even the "sweet-cheeks") which is probably why the slot was crossed a little higher (8000Hz?). In both cases, the old-style 375 diaphragm had a pretty sharp cutoff around 8kHz which is an important part of the crossover; a newer diaphragm will need a much different crossover.

For crossovers in general, I would keep the autoformers. I have not seen anyone comment on the importance of keeping the leakage inductance small to maintain true transformer action, but it is (I think) important. It is not easy to make an air-core autoformer with low leakage inductance - I have tried to design one, it can be done, but you would have to do some fancy interleaving of windings to get it right. I say, stick with the original iron core unless you want to make a real research project out of it! Changing the caps is more realistic, either with bypasses or all new caps.

On the subject of horn loading, Olsen observed many decades ago that the acoustic response of a horn with a too-small mouth is very much more flat than the electrical impedance would make you think. That's because the resonances increase horn efficiency at the same time as they increase electrical impedance, reducing the current. For this to work well, the source impedance should be low - hence the autoformer in the crossover. The first resonance peak is (I think) around 600Hz with a 375/HL93, and the driver/horn is quite efficient at that point, with a small excursion. Yes, it will suck up the power and displacement at 900Hz before settling down above 1200Hz, but the actual response should be within a couple dB spread. The bass horn guys use these ideas all the time, but it seems rarely extrapolated to these classic JBL small-mouth horns.

Finally, I seem to recall that the LE-15 is not that hot above 500Hz; if you want to cross higher you might want to get a 2235 or similar woofer. The very short HL93 allows the woofer and midrange to have a small time delay difference, but at a higher crossover frequency you would have to take the delay into account to get the phase right through the transition.

Full disclosure - I have a 4440/HL93 clone crossed at 800Hz to a 2220, and yes, it does honk. I still love it for the "explosive midrange transients" though!

Zilch
04-23-2005, 12:24 PM
I have a spare n7000 and would like to do some experiments of upgrading it with the new parts (caps and inductors).

Sure, have at it:

http://www.jblproservice.com/pdf/Network%20Schematics/N7000.pdf

Replace and bypass the caps and use air-core inductors. DCR of the inductors may be known in the forum. If not, measure them.

A/B testing after could be revealing. We wanna know. :D

[Doubtful just redoing N7000's gonna render S8 a listenable system, tho....]

Paul Joppa
04-23-2005, 07:00 PM
OK, so I poked around in the library and educated myself. Apologies for my inaccurate recollections above!

The N7000 (aka 3105) models as a 5250Hz crossover, -8dB at crossover. It was specified for use with the 375 and either the bullet or the slot. Nowhere near 7000Hz though...

The N8000 (aka 3106) models as a 7500Hz crossover, -8dB at crossover. It was specified for use with the LE85 and either the bullet or the slot.

They are identical, plain second order networks except the 3106 inductors are half the value of the 3105, and the 3106 has 20 ohms paralleled with each output to get the same damping. They must have done this so they could use the same capacitors - simplifies inventory!

In the 3133A (4133A monitor) the LP crossover to the 2420 is the same as the 3106, including the 20 ohm resistor, but the HP to the slot is a third order. It models as having some nasty peaks and dips, but probably the actual inductor has just the right resistance to make it work well.

Fascinating study!

4313B
04-23-2005, 10:28 PM
Here are the voltage drives.

http://audioheritage.org/vbulletin/showthread.php?p=3082


In the 3133A (4133A monitor) the LP crossover to the 2420 is the same as the 3106, including the 20 ohm resistor, but the HP to the slot is a third order. It models as having some nasty peaks and dips, but probably the actual inductor has just the right resistance to make it work well.No comment.

gorg
04-24-2005, 12:11 AM
Thank you all very much for the help.



I have been looking / researching the possibility of improving my S8R mid and high frequency for a while. Through the helps from a friend of mine (also a S8R owner), I replaced the coupling caps in my EL34 SET amplifier with Jensen copper foil in oil caps. I can say this, it has brought my speaker system up to a different level, very rich and warm bass as well as the midrange has dramatically improved. However, I can still feel the high frequency could be improved. I have been thinking for the crossover. I found people have the crossover upgraded for other high end speakers with success. Here are some interesting readings,



http://www.meta-gizmo.com/Tri/rubbers.html (http://www.meta-gizmo.com/Tri/rubbers.html)



http://www.meta-gizmo.com/Tri/speak/jenson.html (http://www.meta-gizmo.com/Tri/speak/jenson.html)



Within our JBL community, I am just wondering if there is any successful story of upgrading crossover with our current technology, air-core inductors and new oil caps. Or could we still keep the original iron-core inductors. Paul Joppa has brought a good concern.



I am thinking replace all components with Jensen parts,



I will keep the original design but just replace two inductors with 0.6 mh Jensen air-core inductors and two caps with 1.5 u Jensen copper foil in oil speaker caps. They are expensive. It hesitate me a little if I should still keep the original JBL inductors.



Thank you guys,



Gorg