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Mikhail
01-24-2015, 02:02 AM
I want an active crossover for bi-amp for 4343.
The cut on 300Hz.
Here's a cross:Pioneer D-70.
Pioneer D-70 (http://audio-database.com/PIONEER-EXCLUSIVE/etc/d-70-e.html)
The cut: 250Hz and 320Hz.
How much it will be good?
It would be correct to connect it to 4343

hjames
01-24-2015, 05:45 AM
I want an active crossover for bi-amp for 4343.
The cut on 300Hz.
Here's a cross:Pioneer D-70.
Pioneer D-70 (http://audio-database.com/PIONEER-EXCLUSIVE/etc/d-70-e.html)
The cut: 250Hz and 320Hz.
How much it will be good?
It would be correct to connect it to 4343

The typical Low crossover point for the big JBL 4-ways is 300Hz ...
If your choices are 250 or 320, I'd probably try 320 and see how that sounds ..

http://www.jblpro.com/pub/obsolete/4343b.pdf

The factory design (like the 4345) came with a built in bi-amp switch which is a point of failure -
over the years the switch contacts can get dirty and fail, so it doesn't work right.
JBL senior engineer Greg Timbers has recommended bypassing that switch.
http://www.audioheritage.org/vbulletin/showthread.php?10613-4345-Includes-Designer-s-Post&p=110349&viewfull=1#post110349

I had a pair of 4341 (slightly older 4-ways with similar drivers) that I biamped
I made a new rear connector plate with 4 connectors (2 pairs of 5 way).
I ran a new pair of wires in the cabinet directly from the low pair of connectors on the back panel to the Woofers.
I ran a new wire from the OTHER pair of connectors to the input of the internal crossover.

I used an Ashly XR1001 Active crossover when I did mine. I took the output of my preamp, ran it into the Ashly,
and had 2 pairs of outputs for the speakers - a Low pass pair, and a high pass pair.

Its best when you use 2 power amps with similar tone - maybe even 2 identical amps.
Some folks like to do a vertical biamp - use one amp for the left speaker, one for the right speaker.
To do that,
For the left amp, one channel to feed the woofer, one channel to feed the "high split" - the other 3 drivers (mid-bass, horn and slot tweeter)
The other amp hooks up the same way for the right speaker.


You can also do horizontal biamping where you use one amp to run the "high pass" speakers,
and use another amp to run just the woofers. Doing it that way you can use a bigger amp to run the woofer.

But thats the basics - play around and see what sounds good to you.

BMWCCA
01-24-2015, 07:27 PM
Another vote for the Ashly XR1001. I'm using one with my 4345s and I can't find any fault with their performance. I'm using a Crown PS200 for the upper speakers and a Crown PS400 for the LF so that would be "horizontal" bi-amp mode. You can find a good Ashly used for small money or still buy them brand-new for around $250.

In my experience, the XR1001 without the hyphen in the model number were all American-made. The later and current models are labeled XR-1001 and some are Chinese-made, but not all, FWIW.

Mikhail
01-25-2015, 04:58 PM
Thanks for the answers!
I will buy ASHLY XR-1001 it near there.
How is the signal in 4343 when switching on the outside a Cross? whether there is a drawing? What is the difference in the internal crossover?

Ian Mackenzie
01-26-2015, 01:57 AM
The Pioneer crossover is an excellent unit if it is in full working condition.

Try a search for 4343 crossover schematic.

As I recall its a 4 pole rotary switch that bypas the LC low pass filter on the 2131Awoofer and bypass the LC high pass filter on the 2121 10 inch cone .

You will need to connect the high power amp to the second set of binding post on the rear speaker box terminal plate.

As I recall JBL engineers measured the acoustic response of the bi amp 12 db filter set at 320 hertz and discovered a Hump in the response that effected the subjective performance.

This hump was caused by mutual coupling of the woofer and mid cones and was resolved by spreading the crossover points to 230 hertz and 350 hertz from memory.


Hope this helps.

Ian

Mikhail
01-26-2015, 03:19 AM
Can anyone help me find a native jbl 4343 crossover schematics.

hjames
01-26-2015, 04:14 AM
Can anyone help me find a native jbl 4343 crossover schematics.


Sure! The 4343 System came with the 3143 Crossover network

Link to 3143 schematic - http://www.jblproservice.com/pdf/Network Schematics/3143 Network.pdf

Link to 3145 schematic (the newer 4345 crossover is recommended as an upgrade to the 4343 design) -
http://www.jblproservice.com/pdf/Network Schematics/3145 Network.pdf

Also read 4343 Crossover thread here - (31 pages!) http://audioheritage.org/vbulletin/showthread.php?t=1388&highlight=Giskard+networks

LINK to the Techbot post about the 4345 - Includes Designer's Post
http://audioheritage.org/vbulletin/showthread.php?t=10613

Oh - a few years back I did compile a series of reference threads for the various big 4 way JBL Monitors ...
you may find some interesting information there

http://www.audioheritage.org/vbulletin/showthread.php?16924-Technical-Ref-Threads-for-434x-monitors

martin2395
01-26-2015, 02:19 PM
The Pioneer crossover is an excellent unit if it is in full working condition.
This hump was caused by mutual coupling of the woofer and mid cones and was resolved by spreading the crossover points to 230 hertz and 350 hertz from memory.
Hope this helps.

Ian


Hi Ian,
Are you referring to 230Hz lowpass on the 2231A and a 350hz highpass for the 2121, wouldn't it cause a hole in characteristics around 300Hz?

grumpy
01-26-2015, 07:36 PM
...to compensate for a peak/hump, yes. Sort of the point.
(sorry, my moniker is alive and well tonight)

Mikhail
01-27-2015, 02:36 AM
Thanks for the help! See diagram! But do not understand! When in an external crossover, how to move the signal?

Ian Mackenzie
01-27-2015, 12:24 PM
Hi Ian,
Are you referring to 230Hz lowpass on the 2231A and a 350hz highpass for the 2121, wouldn't it cause a hole in characteristics around 300Hz?

Under normal circumstances yes.

But the measured response show bump (not a hump) so JBL shifted the crossover points in the crossover points (see JBL crossover cards in JBL manual) to compensate.

Bearing in mind the slopes were 12 db this is what was done way back in the day.

Years ago we went over this in a thread discussing obsolete JBL crossover cards for the 4343.

For home use this is perhaps not so critical but for monitoring JBL could measure the bump and hear it so they made some adjustments. Crossover design at JBL was empirical back then but it does tell you JBL was serious then they quoted response variations.

martin2395
01-28-2015, 08:10 AM
Interesting! My Bryston xover has separate controls for low- and highpass so I could fiddle around with it a little.
Some time ago I opened a thread here on LH and asked if the 3155 CC network was suitable for 2123H because to my ears that region sounds rather strange, some male voices sound too thick/heavy.
Maybe it is that bump that I'm hearing!

I assume that the bump is caused by mutual coupling of the midbass and the woofer so even if my 4343's have 2235H and 2123H, the bump would still be there?

Ian Mackenzie
01-28-2015, 11:42 PM
Interesting! My Bryston xover has separate controls for low- and highpass so I could fiddle around with it a little.
Some time ago I opened a thread here on LH and asked if the 3155 CC network was suitable for 2123H because to my ears that region sounds rather strange, some male voices sound too thick/heavy.
Maybe it is that bump that I'm hearing!

I assume that the bump is caused by mutual coupling of the midbass and the woofer so even if my 4343's have 2235H and 2123H, the bump would still be there?

Affirmative

martin2395
01-30-2015, 06:57 AM
I guess I have to test that and put RoomEQ wizard to work.

I finished placing my 3155 CC networks in a pair of el-chapo 2U rack enclosures, and I have to say I like it a lot with no L-pads :blink: