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ngccglp
06-22-2007, 01:45 PM
Hi,

Is there a simple mod that can be perform to separate the low and mid/high/uhf segment of the crossover so that I can use two stereo amps to drive the low and high freq segments passively separately?

Thanks

subwoof
06-22-2007, 02:00 PM
just rotate the switch on the crossover input plate. Search the library on this site for the manual and schematic.

sourceoneaudio
06-22-2007, 02:09 PM
Just rotate the switch on the crossover input plate. Search the library on this site for the manual and schematic.


Subwoof,
Does that not disable the internal x-over when that is done, and the drivers are then wide open? I do not think he mentioned he was going to use an electronic x-over (outboard). I think he wants to run them in a bi-amp mode using the internal x-over. ??? :blink:

Correct me if I'm wrong. ?

Robh3606
06-22-2007, 02:33 PM
just rotate the switch on the crossover input plate. Search the library on this site for the manual and schematic

Nooooooo Don't do that. You switch out parts of the passive networks. There is no easy way without an internal modification to Bi-Wire.

Rob:)

hjames
06-22-2007, 02:57 PM
Hi,

Is there a simple mod that can be perform to separate the low and mid/high/uhf segment of the crossover so that I can use two stereo amps to drive the low and high freq segments passively separately?

Thanks

No - you need an preamp level crossover to split low and High frequency, then an amp for each. Its called BiAMPing - Biwire is not the same thing and is not recommended

Ian Mackenzie
06-24-2007, 01:35 AM
Hi,

Is there a simple mod that can be perform to separate the low and mid/high/uhf segment of the crossover so that I can use two stereo amps to drive the low and high freq segments passively separately?

Thanks

Hi Ngccglp,

I have never heard of anyone Bi wiring a 4343.The newer 4344mk11 had this feature but not the 4343 sorry.

As mentioned above it is possible with modification. However if you were leaning towards this for improved performance biamping with a hi level active crossover or re building the passive crossover network would be a priority.

For example you could replace the existing terminals (or the terminal plate) and re wire the circuit for bi wiring with twin binding posts like this image. The older terminals use steel through connecting bolts and this may not be attractive to someone wishing to bi wire as they effect sound quality in my practical experience. The bi amp switch should then be completely bypassed (see 3143 schematic). This is not a simple modification and it maybe preferable to re build the crossover network.

What sort of amplifier are you using?

(I have infact have however Bi wired my own diy 4345 JBL (when I am in the mood!) and I think it makes a difference with the Zilch Master twisted Cables..Yippy.)

The Bi wiring incidentally usually means twin sets of cables from a common stereo amp to the loudspeaker that is set up with bi wireable terminals.


Please search for threads on Bi amping this model and crossover upgrades.

ngccglp
06-29-2007, 05:19 AM
Thanks Ian for the advice.

I am using the Mcintosh MC2500 500 Watter to drive the 4343B. I noticed the Mac character to be a good match to the forward sound of the 4343B.

May I know what is the L Pad setting most of the 4343 owners use? I used to have 4333Bs and its easier to get right because there's only 2 L Pads. With 4343Bs, its difficult to get the right combination. I've heard the 4333Bs bass and I should be able to extract out better performance from the 4343Bs.

Could anyone give a brief description of the type of musical instruments to use to adjust the mid-bass L Pad? I use Sax to adjust the high freq L Pad.

Thanks

Ian Mackenzie
06-29-2007, 07:03 AM
Land of Sushine?

Well it rises and sets with theses.

You can try using my Tandy spl meter method with the 4343 (see elsewhere, for net db measurement)

http://www.audioheritage.org/vbulletin/showpost.php?p=60625&postcount=7

Some members tend to disagree with this approach but I have found it to be only reliable and inexpensive means of calibrating the individual driver levels to +- 1/3 db resolution and in every instance the 2 metre gated MLS testing is always the smoothest overall usng this method.

I find 1 db steps way to coarse and 1/2 db steps often miss the sweet stop. Another v.important point is to get consistancy between left and right channels.

Set the L pads up for 0 db position. However the plastic caps tend to move and twist and do not give an accurate indication of the markings while the L pads themselves have a lot error in adjustment.

So do not rely on those foil cal markings.(see above)

I note that some members adjust the horn and UHF for -2 db on the L pad. One reason is the 4343 in its vintage native state is a bit brash in the upper midrange, particularly if using the original 2420 driver diaphragms. A typcially live listening room will sometimes dictate the final setting.

I also tend to find it useful to set the woofer/mid cone level first, even turn down the horn to do this if required. Most people get the woofer/mid balance wrong and end up messing with the horn out of frustration for a long time.

See how you go. I would expect the final adjsutments to take some weeks.

The above meter method is a means of obtaining a baseline for the output of each driver. Otherwise you are all over the shop.

John Nebel has a similar set of amps and 4343 so it may pay to pm John.

I heard them go and was impressed.

Hope this helps

Ian

ngccglp
06-30-2007, 03:37 AM
I tried the horn at -2 db, not bad. I kept the UHF at 0 db, sounds more airy that way. I think it will take a long time to dial in the performance with many cds.

Anybody has the owner manual for 4343?

Thanks

JSF13
06-30-2007, 08:18 PM
Very useful information Ian. Thanks!

Joe:)

Ian Mackenzie
07-01-2007, 12:16 AM
Joe,

I take it you have a pair of 4343's?

Its perhaps also worth mentioning the JBL 4343 is more difficult to optimise than the later versions of this model which had more highly refined drivers, diaphragms and crossovers and an offset baffle configuration that helps reduce ripple in the response.

What I am saying is up to a point the design is what it is. But with a careful, systematic approach to setting up you can yield quite acceptable results. The Mac's (smooth with plenty of punch) do seem to work quite nicely as I recall with John Nebel's 4343's..although John prefers the JBL 4435 for classical recordings.

Something about setting them up should perhaps go into that reference thread.

JSF13
07-01-2007, 08:25 PM
Joe,

I take it you have a pair of 4343's?



No actually I don't. But I was able to use a variation of your Tandy SPL meter procedures to adjust the L-pads on my 4430's with great success (at least to my ears).:) ;)

Joe

Ian Mackenzie
07-01-2007, 11:17 PM
Good,

Glad it worked.

Ian

ngccglp
07-02-2007, 06:02 AM
Reporting in...

Somehow the mid bass at the 0 db position produces the most pleasing bass response, enough low end with a strong "thud" to the kick drum. There's a tendency to lower the mid bass to get more bass output but somehow that muddled the bass articulation.

Surprise, I ended up with mid 0, high -2, UHF -2. Is this really the optimal setting with modern amps and digital sources? :)

Ian Mackenzie
07-02-2007, 06:05 AM
Okay,

See how that setting goes for a little while.

Ian

Mannermusic
07-02-2007, 07:05 AM
Thanks Ian for the advice.

I am using the Mcintosh MC2500 500 Watter to drive the 4343B. I noticed the Mac character to be a good match to the forward sound of the 4343B.

May I know what is the L Pad setting most of the 4343 owners use? I used to have 4333Bs and its easier to get right because there's only 2 L Pads. With 4343Bs, its difficult to get the right combination. I've heard the 4333Bs bass and I should be able to extract out better performance from the 4343Bs.

Could anyone give a brief description of the type of musical instruments to use to adjust the mid-bass L Pad? I use Sax to adjust the high freq L Pad.

Thanks

Re which musical instruments to use for the "mid bass" - I call it mid range; this is where the meat of the instrumental fundamentals lie - a good rule of thumb is to remember that the trumpet "high C" is approx 1000 Hz. The bottom of the trumpet range is 2 1/2 octaves below that, approx. 200Hz. I find the trick is to turn off the upper two transducers and balance the mid to the woofer, listen to that for a while and tweak. Then bring in the treble horn gradually - keep adding until it gets a bit edgy (irritating), and then back off a tad, say one number. Then add the UHF. Actually, a neat trick is to modify the crossover to allow the mid horn to roll off with no attentuation and then add the UHF as a "supertweeter." In fact, many would find they prefer the horn alone . . . all this depends on the particular application, the room, the kind of music, in my experience. I use an RTA as a double check for problems but the room acoustics basically nullifies any hard science at this stage.

ngccglp
07-05-2007, 06:54 AM
Nope, the mid bass 0 mid high -2 UHF -2 setting is not right for my room. Bass lack weight, chest did not feel the whack. Too much mb.

I used Manner's method and I think its very effective. Now the setting is mb -4 mh -7 UHF -7 (my foilcal are calibrated/printed in db). Now the 4343Bs are beginning to sound like a million bucks. Man, Lenny Kravitz is in the house! :applaud:

Ian is right, the Lpads are very sensitive, even 0.5 db is too gross an adjustment. Patience is key.

Thanks

Mannermusic
07-06-2007, 12:10 PM
BRAVO! :applaud:

ngccglp
12-06-2007, 12:23 AM
Hi Guys,

Finally took the plunge and bought a Behringer electronic 2-way XO to bi-amp my 4343B as follows:

Pre - Mac C40
MAC MC2500 - Highs
Krell KAV300i (using as poweramp) - Woofers.

First impression is the highs are much cleaner and less distortion, details can be easily picked up. More importantly, the brightness/forward sounding caused by the high freq driver/horn is gone, surprise surprise...:applaud:

Any advise on preferred XO freq? Or should I just stick to 300 Hz as recommended for 4343B? Also what to expect in the difference in sound between 12db (JBL recommended) vs 24db (my XO) per octave

Thanks.

ngccglp
12-07-2007, 03:55 PM
Hi,

Any recommendations for active XO that has better S/N ratio? i.e. lower noise. Also, for JBL speakers, do I need the time delay functions or am I better off without them.

Thanks