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Multi-Way Conventional loudspeakers with crossovers

JBL E60 very strange crossover
JBL E60 very strange crossover
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Old 6th August 2011, 11:14 PM   #1
-_nando-_ is offline -_nando-_  Brazil
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Question JBL E60 very strange crossover

Hi There!

I'm about to make an adaptation using the excellent Beyma T2010 tweeters on my Northridge E60 JBL Speakers.

After some stupid abuse, I've blown the original tweeters. OK, sh*** happens, but I was surprised when I removed the cover and I found a very small tweeter in there, which was 4-Ohms! Digging deeper, I found more weird things. The crossover for the TW is just a 2.5uF capacitor, that if I'm correct, will provide a 16khz cut 6Db/oct for a 4Ohms driver. The owner manual says that the crossover frequencies are 1000 Hz and 4000 Hz. So, what the heck?!

I've attached the crossover schematic, it is 100% reliable as I drew it myself and I measured the inductors. I couldn't figure out the frequencies, neither the type myself. I was hoping that you could help me figure that out!

By the way, why would the tweeter be 4Ohms if the rest is 8Ohms?

Why would the midrange be inversed?

What are the actual xover frequencies and type?

Thank you very much!

Best Regards
Attached Images
File Type: png E60 Xover.png (11.8 KB, 266 views)
File Type: jpg tweeter.jpg (34.8 KB, 251 views)
File Type: jpg tviter2.JPG (9.4 KB, 246 views)
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Old 9th August 2011, 10:52 AM   #2
erjee is offline erjee  Netherlands
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Maybe this is the answer to your question:

JBL E60 quick review

Click the image to open in full size.
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Old 9th August 2011, 02:13 PM   #3
-_nando-_ is offline -_nando-_  Brazil
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Yes, it did! Basically the E60s are crippled from factory by a shocking bad crossover. The Mid isn't there because of a 7R5 attenuation resistor. There's a lot to work on them, but they really have potential to sound awesome! Will just require a measurement tool and time to work on it.
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Old 9th August 2011, 03:10 PM   #4
DrDyna is offline DrDyna  United States
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I think the majority of inexpensive manufacturers use crossovers like this, I've got a pair of Cerwin Vega 3 ways in the basement that have I think 4 or 5 parts (if you count the fuse) on the crossover that's glued to the terminal cup, and another pair of Altec Lansing outdoor-type speakers that I'm using for my surround-back left and right that have only a capacitor on the tweeter if I remember right.
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Old 9th August 2011, 03:45 PM   #5
-_nando-_ is offline -_nando-_  Brazil
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Yeah... But 4-Ohms tweeter is really TOO BAD! E60's arent that cheap anyway...
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Old 9th August 2011, 04:08 PM   #6
DrDyna is offline DrDyna  United States
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Quote:
Originally Posted by -_nando-_ View Post
Yeah... But 4-Ohms tweeter is really TOO BAD!
I don't get what you mean, lots of superb tweeters are 4 ohms.
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Old 9th August 2011, 04:22 PM   #7
-_nando-_ is offline -_nando-_  Brazil
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In a 8-Ohms loudspeaker?
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Old 9th August 2011, 04:27 PM   #8
DrDyna is offline DrDyna  United States
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Quote:
Originally Posted by -_nando-_ View Post
In a 8-Ohms loudspeaker?
Sure, the speaker can be labeled as 8 ohm nominal impedance, but at any given frequency the impedance moves around quite a bit. Chances are the amount of the frequency spectrum that the tweeter covers in a 3 way wasn't significant enough to change their rated average impedance.

They probably just got a better deal on the 4 ohm version and figured it wouldn't alter the average impedance enough to be of concern.
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Old 9th August 2011, 04:56 PM   #9
-_nando-_ is offline -_nando-_  Brazil
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Yeah, but they were receiving twice the power, consequently, they toasted.

Anyway, apart from that, I would like to show you all how the E60 are "capped" of its true potential. Attached are the service manuals of borth E60 and E80 loudspeakers. You can observe that the Mid-range and Tweeters are the SAME for both. The only difference is that the E80 uses 2x 6" woofers instead of 1x 8" of the E60. Anyway, that does not justify the HUGE crossover difference.

The E60's manual claims that the crossover frequencies are 1000 and 4000Hz. CLEARLY the crossover frequency of the tweeter is not 4k, but it is 16k, as it uses a 2.5uF cap on a 4-Ohms tweeter.

The Mid-Range is too much attenuated with a 7R5 resistor, that's why it has reviewed as pointed out from our friend erjee:

Quote:
While it feels like JBL has great smooth and powerful bass and are perhaps more detailed then Athenas at the high end they totaly lack any sort of midrange. It's so muted with the E60, it simply isn't there and that takes away the joy of listening to anything that has any midrange.
Anyway, I'll build a crossover similar to the E80's but with an additional 2Db attenuation for the mid-rage, to couple with the E60's lower sensitivity single woofer. The tweeter Will be the Beyma T2010 which is EXCELLENT, attenuated in 3Db (from 92Db to 89Db), so it couples with the rest.

I think I'll hear a GREAT improvement!

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Old 9th August 2011, 05:10 PM   #10
DrDyna is offline DrDyna  United States
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Quote:
Originally Posted by -_nando-_ View Post

The E60's manual claims that the crossover frequencies are 1000 and 4000Hz. CLEARLY the crossover frequency of the tweeter is not 4k, but it is 16k, as it uses a 2.5uF cap on a 4-Ohms tweeter.
You can't be certain without seeing the impedance and frequency curves of the tweeter rather than just it's nominal value. It's nearly impossible to look at crossover values and then try to know the crossover frequency knowing only nominal impedance.

The crossover frequency of the tweeter may very well be 4khz if the impedance of the driver in that range is high enough.

You'd have to measure the drivers frequency response and impedance curves to know for sure, simply changing the crossover component based on the nominal impedance airbrushed on the back of the magnet probably won't yield very good results at all.
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