JMR Trente - Crossover Help

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kstylianos

Member
Joined 2006
A friend recently gave me a pair JMR Trentes that were damaged during shipping a few years ago and he never got around to fixing them. Both of the crossovers were damaged. One of the PCB's cracked in half and was "repaired". It also appears that a couple components fell off and were resoldered back on, possibly incorrectly. Listening to the speakers, they distort quite easily....something w/ the crossover network just isnt right.

New crossovers from JMR cost ~$180 a piece. As I'm a student, this is definitely not feasible at this time. I bought a couple PC boards and plan to re-wire the crossovers PTP. As my crossover knowledge is minimal, I'd like some help getting these figured/sorted out.

Doing some research I found:


The Trente has two drivers, a 6.5" woofer and a 1.1" freestanding tweeter (see picture). The crossover is described as a three way, leaving one to contemplate where the third driver has been hidden. There is no third driver in spite of there being crossover points at 1200 Hz and 3,800 Hz with 6 and 12 dB attenuation rates. The trick here appears to be the use of a double magnet system on the woofer; each magnet being treated like an independent driver. Unlike most speaker crossovers, the filters here are in series. Well, not exactly; themidrange/treble crossover is a series type. Which leaves us with a parallel configuration for the crossover at 1200 Hz.
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1st and 2nd order (6 and 12 dB/octave) design ensures a perfect transition between the two loudspeaker units with excellent phase response; Crossover frequencies at 1200 and 3800 Hz. Treble/medium crossover in a serial configuration, hand-wound pure copper air coils, tin armature capacitors for the tweeter, silver/copper thread wiring under kapton protection.
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A little more regarding the double voicecoils of the woofer:

The woofer is unusual in that it uses a double voice-coil. Each of which is driven separately, which is why the two-driver is specified as having a three-way crossover. According to designer Jean-Marie Reynaud, "the two moving coils are wound on the same mandrel but isolated from each other. We apply to the first moving coil a signal with a low-pass frequency and the second with a low-pass frequency. Thus we have good energy in the low part of the spectrum, the two coils working together in parallel configuration. Of course, the crossover is specially designed to avoid phase problems."
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Inspecting the network, the crossovers are currently wired as such (see attachment). Are they wired correctly, does this make sense....any help would be appreciated here?

An externally hosted image should be here but it was not working when we last tested it.



Even better, if anyone would mind inspecting or even taking some detailed pictures of their JMR Trente crossovers, that would be fantastic!

Thanks again all........
 
K

kstylianos

Member
Joined 2006
Goldal, Thank you.

L1 was definitely one of the suspect components. The connection/joint for L2, on the other hand, looks factory fresh. Also, connecting L2 in the fashion you mention 'may' be physically impossible as these components sit on opposite ends of the board. I'll inspect in more detail this eve.

Thank you again.....
 
K

kstylianos

Member
Joined 2006
I connected L1 in series as suggested and the speakers sound MUCH better. No distortion to speak of, crisp and clean.

Looking at the physical location, original soldering joints, etc. of L2, I honestly think the way it is drawn in my original schematic is the way it came from the factory.....just from mere inspection (Sherlock Holmes).......but will default to the combined wisdom of the forum.

Does anyone else think something is suspect with L2, or any other component for that matter?

One step closer, just want to make sure all is correct before building new networks on PC board.

Thanks again.
 
S

sreten

R.I.P.
Joined 2003
goldal110 said:
hi ,kstylianos
L1 on woofer 2 must be in serie ( between +in and + woofer)
L2 must be connected between 5µf cap and 3 Ohm resistor
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Hi,

L1 should be connected as stated,

L2 doesn't sound right, as shown its right - just a bizarre way of
wiring it, if you move L2 to between 3R and 5uF this effectively
puts the 5uF in series with the 6uF.

:)/sreten.
 
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