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View Full Version : Jbl M552 vs JBL/UREI 525 crossover



wpod
02-26-2008, 12:38 PM
Greetings- I 've been using a JBL M552 electronic crossover for biamping my 4343s for about the last two years and have been quite pleased with the results. However, never wanting to leave things as they are, I've been considering switching to a JBL/UREI 525 crossover to replace the M552. What are your thoughts on this unit? , would it be an upgrade or should I just leave things as they are? I'd appreciate your feedback, Thanks very much, Paul ps- As I don't own a JBL/UREI 525 at the moment, are there any available here on the forum?, and if not, what should I expect to pay for one? Thanks again, wpod

hjames
02-26-2008, 01:04 PM
http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/UREI-525.pdf

They have been, apparently, going for insane prices on the bay lately ...
The manual (Link above) is copyright 1980, 1989 which makes them 19-28 year old gear. Based on the schematic, its (quad) op amp circuits - generally called negative feedback design. Thats older tech, and not as clean as the better designs of today. If you can get one cheap and spend some money to clean up the power supply caps and such, its probably fine, but if you want to upgrade from what you have - there are better crossovers around.

Have you seen Bo's comments on his system?

http://audioheritage.org/vbulletin/showpost.php?p=202132&postcount=43

In his summary he mentions Ashly XR1001 (specs) (http://www.ashly.com/genspec/gs_xr-2.html)(manual) (http://www.ashly.com/manuals/xr-manual-n.pdf), and the Bryston 10B - (http://www.bryston.ca/10b_m.html)probably worth looking into those as a start.




Greetings- I 've been using a JBL M552 electronic crossover for biamping my 4343s for about the last two years and have been quite pleased with the results. However, never wanting to leave things as they are, I've been considering switching to a JBL/UREI 525 crossover to replace the M552. What are your thoughts on this unit? , would it be an upgrade or should I just leave things as they are? I'd appreciate your feedback, Thanks very much, Paul ps- As I don't own a JBL/UREI 525 at the moment, are there any available here on the forum?, and if not, what should I expect to pay for one? Thanks again, wpod

grumpy
02-26-2008, 01:37 PM
also consider M552 is 24dB/oct, 525 is 18dB/oct. I would anticipate an audible
difference.

Without mods (I can hear ScottyJ coming down the hall already...), I'd be more concerned
about what either of these units would do from the crossover point on up.

Still would be biamping? Plunking down $$$ cash for an old 525 that is likely not "in fine
tune" might be better spent (as others have suggested) on a fine 2-way (crossover).

-grumpy

(seems like 525's in fair shape have gone for $400-500)

scott fitlin
03-06-2008, 10:59 PM
Came running from down the hall, thanks Grumpy! :applaud:

The urei 525 was, IMO, a great sounding crossover WITH mods. Stock, its untity gain in and out.

The better sounding units, IMO, were the ones with the TLO84 IC,s, later they switched to the TLO74, I just like the 84 better.

Power supply, 1000mfd axial 25v caps stock, good to upgrade to an axial 2200mFd 50v cap, there are three to replace. You may want to consider better diodes ( high speed, soft recovery, Vishay diodes come to mind ) for the power supply rectification as well. As far as PS components are concerned, I " DONT " think they may make a difference, I " KNOW " they do.

Gain, both input and output IC feedback loop resistors should be changed to increase available gain, how much is the question!

There is a row of yellow "Century" brand caps, I think these are film caps, and they can be upgraded to a better quality cap, will make an audible and positive difference.

IF you increase the output gain, there are thru holes for additonal disc capacitors in the quad IC feedback loops, stock units have four 33pf caps, and two for the last TLO84 IC, upgrade by adding the additional caps in the the trhu holes already provided, same value. You could use silver mica disc caps, said to be superior.

If you want to get REALLY involved, there are a couple of resistors jumped out, you will have to PM me for this info, and Ill give it to you.

Some prefer the 525 with the output transfomers removed from the signal path, this may or may not be to your liking. I personally like them, as they color the sound in a favorable way, IMO, BUT, maybe not truly HI FI!

The 525 had a nice sound, and with work, still does, IMO, BUT, know this, there are crossovers avaialble today that legitimately surpass that crossover in sonic traits. I have found that although my modded 525,s have an enchanting sound for analog, vinyl playback, it is NOT always the best when it comes to playing CD.

The IC based circuits are just not up to snuff for playback of digital source material, IMHO. Another thing, is while I still do love the sound of the 525, I love it with certain speakers, and NOT with others. Example. I love the sound of the 525 with JBL 2441 compression drivers, and I absolutely HATED the way my TAD 4002 compression drivers sounded with the 525 as the crossover. Conversely, now I am using customized Bryston 10B crossovers, and the JBL 2441,s sounded OK, but the TAD 4002,s sound WICKED, PHENOMENAL using Bryston 10B,s.

So, not knowing what amps, and speakers you have, I dont know what I would tell you as my #1 choice. But, I can say, IMHO, IF you have TRULY High resolution, SOTA current modern speakers, they will reveal flaws in signal processing and amplification and source material. If you have vintage speakers, that are less highly resolving, you might like the coloration the 525 produces. But, it is coloration, for sure.

Another thing to point out, is that although the Urei 525 can produce what I call a charming sound, hit it a bit too hard, you will hear the IC,s distort. I run a HIGH SPL commercial system, and the discrete circuit topology, ( NO IC,s ) of the Bryston 10B,s does not fall apart and get crunchy, or distorted sounding. It seems no matter how hard I hit the BRYSTONS, they just dont distort. Fantastic power supply, discrete circuitry, and high quality components, with superb engineering at work here.

Then, another thing to consider is the state variable filter frequency controls of the 525 and output level attenuator pots. Although the 525 has the LED frequency readout to tell you where your crossover points are set they are not always 100% accurate, and they do drift. That is a known problem with the 525. I mean, if you have an excellent tweeter, and your crossover point is 8000hz, you want it to be 8000hz, not 7884hz, or changing ( drifting ) on it's own. You will also want to have the silver contact wafer switches cleaned. I have also come to adore the steeped attenuator output level and frequency selection controls of the Bryston, with 1% metal film resistors, repeatability of settings is a BREEZE! Sometimes, its a bitch getting the EXACT setting you had when you futz with the 525 trying to dial it in to sonic perfection.

Yet still another known problem, most 525,s had waffle IC sockets, so, the IC plugs into the socket, and these can be intermittent. Sometimes, you lose the output on ch 1, ch 2, ch 3, etc, and a tap obn the faceplate brings it back. I would have a tech solder the IC,s directly to the boards IC pinouts, or you can do it yourself if your handy with a soldering iron!

IMHO, a "WORKED " Urei 525, in the right system, can make some enchanting sounding vinyl playback, but, I'm telling you the known problems of the unit, as well as the fact that I feel that sound can be, and has been surpassed today, especially for digital playback of Cd and downloads.

I, personally, have been a long time urei 525 user, AND I loved it back in the vinyl days. However, I have moved on, to bryston, and I havent looked back yet.

On the positive side, the 525 was about the MOST flexible analog crossover made, 2 OR 3 WAY stereo operation, or 4 or 5 WAY mono operation, 2 required for stereo in this mode, obviously. As well as any frequency you desire can be dialed in, and the output level controls allow one to find those in between settings, unlike detented controls with their factory settings in 1DB increments.

If you find a mint 525, I will be more than happy to pass modification info to you, and whatever assistance you want, to achieve the best you can get from the 525.

If you would like to talk further on the pro's and cons of the what I think are the 525,s strong and weak points, please feel free to PM me, I am happy to try to help!

The one thing I will disagree with about current trends in filter technology today, is slopes, I like 12 and 18 DB slopes. I do not like 24DB slopes. I find 24Db to not have quite enough overlap between filter bands, sometimes 12db too much. However, this is also VERY dependent upon your speakers and their design. With just about EVERY speaker I, and my friend, who also does commercial audio, we just find 18db Butterworth filters allow us to create a much more seamless sound with 3 way or 4 way active setups. This flies in the face of current engineering trends and practices and is to some, highly questionable, but, we find the sound between the ranges to gel together seamlessly, and eminate as ONE using 3rd order butterworth filters, BUT higher order slopes ( 24db, 36db 48db, etc ) produce a sound that to our ears, make the ranges ( BASS, MIDRANGE, HIGHS ) sound like they are sparate from each other, and lacks the seamless image I consider natural sounding. Of course, 24db slopes, and higher, allow higher power to be used for compression drivers and tweeters, but, unless your doing HIGH POWER commercial sound, I don't think this is a problem for you. The other thing about 24db slopes, is they are acoustically in phase at crossover point, 18db is considered out of phase at crossover point. But, 18db Butterworth sums flat at unity, which I think sounds nicer. My Bryston 10B,s have switch selectable slopes, 6, 12, or 18 db slopes, and I run my TAD 4002,s and JBL 2404,s 18db but I run my horn loaded TAD 1603 woofers 12db slopes. Again, speaker design, and cabinet type have EVERYTHING to do with what slope works and sounds proper. TODAYS top quality crossovers, like Bryston, have selectable slopes, and the dsp crossovers have 6,12,18,24,36,48, and 52 db slopes, as well as one dsp unit having 300db brick wall linear phase filters available. DSP crossovers also have the option of selectable filter types as well. Bessel, Butterworth, Linkwitz-Riley, and Neville-Thiel, and the Linear Phase filter. I just am not totally into digital crossovers at this time, but, at some point, I feel they will get it to the point where I believe digital crossover filters will become indiscernible, sonically, from the best analog filters



:)

Baron030
03-07-2008, 10:37 AM
Posted by scott fitlin:

Power supply, 1000mfd axial 25v caps stock, good to upgrade to an axial 2200mFd 50v cap, there are three to replace. You may want to consider better diodes ( high speed, soft recovery, Vishay diodes come to mind ) for the power supply rectification as well. As far as PS components are concerned, I " DONT " think they may make a difference, I " KNOW " they do.

Without having ever seen a urei 525 schematic, upgrading from 1,000mfd to 2,200mfd caps should reduce the hum level by about 6.8 db. And I am basing this value solely on the estimated reduction of the power supplies ripple voltage.
When dramatically increasing the size of the power supply capacitors, it is certainly a good idea to also increase current handling capacity of the rectifier diodes. During start up the initial surge current will be higher with the much larger capacitors, which could potentially over load and fry the original rectifier diodes. So, if you are going to change the caps, then change the diodes as well. Otherwise, your project could go up in smoke.

Baron030 :)

scott fitlin
03-07-2008, 10:49 PM
Without having ever seen a urei 525 schematic, upgrading from 1,000mfd to 2,200mfd caps should reduce the hum level by about 6.8 db. And I am basing this value solely on the estimated reduction of the power supplies ripple voltage.
When dramatically increasing the size of the power supply capacitors, it is certainly a good idea to also increase current handling capacity of the rectifier diodes. During start up the initial surge current will be higher with the much larger capacitors, which could potentially over load and fry the original rectifier diodes. So, if you are going to change the caps, then change the diodes as well. Otherwise, your project could go up in smoke.

Baron030 :)I do recommend changing diodes to a high speed, soft recovery diode, and certainly a higher current diode could be used.

HOWEVER, my original modded Urei 525 had bigger PS caps, but same diodes the unit had stock, I ran it from 1984 to 2007. It NEVER fried, not a day in its life, and the thing ran 6 to 9 months a year, 7 days a week, up to 16 hours a day.

But, I do agree, IF your gonna rework the PS, rework it, make it sturdy, and make it cleaner than it was.

I also advocate having the mods performed by a competent tech, one who can also make recommendations to brand, type, and values of critical components. Unless you do really know what your doing.

CoralRockSound
01-28-2017, 06:28 PM
Greetings- I 've been using a JBL M552 electronic crossover for biamping my 4343s for about the last two years and have been quite pleased with the results. However, never wanting to leave things as they are, I've been considering switching to a JBL/UREI 525 crossover to replace the M552. What are your thoughts on this unit? , would it be an upgrade or should I just leave things as they are? I'd appreciate your feedback, Thanks very much, Paul ps- As I don't own a JBL/UREI 525 at the moment, are there any available here on the forum?, and if not, what should I expect to pay for one? Thanks again, wpod
hey paul--i've got one in really great shape-call me at 305 359 1936

grumpy
01-28-2017, 06:47 PM
Seeing as that was almost a decade ago, I wouldn't wait up for a reply.