The JBL 4345 Club

[Ian Mackenzie]

David,

Thanks for the picture

This that a dang rocking chair I see yonda between them speakers.

Ian

[speakerdave]

David,

Thanks for the picture

This that a dang rocking chair I see yonda between them speakers.

Ian

'Tis, and that's where I am winters, by the fire, wrapped in a wool shawl. It just shows you how monstrously Brobdingnagian these '45's really are.

[boputnam]

It just shows you how monstrously Brobdingnagian these '45's really are.

Yea, they dominate any room they are in - both sonically and physically!

[Ducatista47]

A big, beautiful room and a big, beautiful pair of JBL's. Isn't life grand?

Since I aquired my pair, I am no longer seeking pinpoint imaging either. I like the way 4345's wrap you up and cuddle you in the sound field they generate. Perhaps they are unique in that respect; I haven't heard enough big speakers lately to know for sure. But it is the most satisfying presentation I have heard so far. Powerful, dynamic, subtle, even...assured. And very JBL. And somehow very inviting and friendly. And, oh yeah, thrilling. Not audio terms, but I tell it the way I hear it.

Clark

PS I'd better explain my setup. they are separated by only five feet and I sit only seven to ten feet back from the center. They are switched left to right, an old methodology that links the tweeters (slots here). I practically wear them. They sound really cool when I sit only five feet back, just before the imaging goes to hell. I always did like headphones! Actually, I move up or back depending on my mood. It's like having a variety of setups to chose from.

PSS If this seems strange, remember, they are monitors!

[Ian Mackenzie]

4345 Headpones anyone

[Ian Mackenzie]

I am currently investigating some options for self powering the 2405 with in built active crossover/amplifer per Greg Timber's earlier post.

There are a couple of clever ideas on the table. I should have some details soon.

If you are interested, a show of hands would be welcome.

Ian


"The ring radiator hates passive networks. A major improvement in the upper range would be to drive the 2405 from its own little amp. You only need 3 or 4 v rms. The 2405 does 110 dB for 2.83v. It is padded way down in the system. There is little real power at those frequencies anyway. You only need to know the voltage output of the amp, power is irrelevant. The 2405 is about 12 ohms and won't draw much current".

[Chas]

Greg's comments interested me too. I was thinking that it would be nice to build some EL84/6BQ5 based amps for the job.

I still haven't got my 4345's up and running yet, so it will be a while before I can play with them.

Let's see what you have in mind, Ian.

[Tom Loizeaux]

Hey, I'm always interested in hearing about ways to make my 4343s sound their best!
Greg's comment about the 2405 certaily raises some questions. One of them being: Why didn't JBL ever make a tri-amp or quad-amp that would have driven their studio monitors to perfection?
I guess it's not up to us to decide if that should be done.

Tom

[Chas]

Hey, I'm always interested in hearing about ways to make my 4343s sound their best!
Greg's comment about the 2405 certaily raises some questions. One of them being: Why didn't JBL ever make a tri-amp or quad-amp that would have driven their studio monitors to perfection?
I guess it's not up to us to decide if that should be done.

Tom

My guess would be it's because inexperienced users would blow up the 2405. In a studio when they rewind or fast forward the tape machines, there is tremendous HF energy generated if someone forgets to lower the level in advance.

[Ian Mackenzie]

Greg's comments interested me too. I was thinking that it would be nice to build some EL84/6BQ5 based amps for the job.

I still haven't got my 4345's up and running yet, so it will be a while before I can play with them.

Let's see what you have in mind, Ian.

I am waiting on a request for some data.

When those details come to hand I will elaborate.

If you are astute and read carefully, I have already hinted at the approach in my recent posts.

Ian

[Ian Mackenzie]

Hey, I'm always interested in hearing about ways to make my 4343s sound their best!
Greg's comment about the 2405 certaily raises some questions. One of them being: Why didn't JBL ever make a tri-amp or quad-amp that would have driven their studio monitors to perfection?
I guess it's not up to us to decide if that should be done.

Tom

Its always interesting to speculate. Cost would be one reason and as I recall there were numerous customised offerings by third party studio designers and consultants during that era.

I propose to test the idea shortly as soon as I can finalise the details.

If its works to expectation and is practical, self amplification of the horn with built in active crossover will be a natural progression.

[Ian Mackenzie]

There are some obvious technical advantages but it will be interesting to measure the output of the 2405 direct coupled to a dedicated amplifier (I'll bet Zilch posts a graph by sunrise).

For example, most domestic / professional amplfiers are least linear at very low power levels. Meaning they don't sound very good at low power levels, particularly high frequencies.

Even with the UHF and HF transducers cranked back 10 db or more you are still talking only a watt or less of power for 95 db @ 1 metre in these systems. Under normal circumstances (unattenuated) the 2405 will produce 105 db and the 2307/2308 108 db @ 1 metre for 1 watt. However, as discussed above, its really a case of the level of voltage drive and not power that has to be understood.

Add to this the issues of the crossover capacitor (as we have been informed) and you have a receipe for dirty highs.

I have previously advocated class A amplfiers for the bi amping of the high section of these 4 way systems which by design eliminates these distortion issues at low power levels and is a subjectively obvious improvement.

It is intended that the 2405 with in-built active crossover/amplifer will be the next phase of improvement. Pending the outcomes we can consider similar duty for the 2307/2308.

Someone is bound to disagree but they probably gave up on listening to these systems a long time ago!

Ian

( I dont propose to outline the detail of the design here, that may appear in a dit thread at some point)

[Chas]

If you are astute and read carefully, I have already hinted at the approach in my recent posts.

Ian

Understood. I am still trying figure out how to design and build a good sounding active H/P xover at 290 Hz just to simply biamp mine - the LF isn't nearly as demanding IMHO, I plan to use my Ashley's for the low pass. I'd be interested to see what you plan for the 2405 in this regard. Maybe a third order passive in front of the amp would be the way to go? Not exactly good engineering, though.

I'm just thinking out loud, here.

[Zilch]

(I'll bet Zilch posts a graph by sunrise).

Alas, no chip amp here.

But, it'll be interesting to see (hear) the difference between a regular amp and one of those.

Off to Parts Express, then....

[#300-952, 15W Stereo Class-T, $29.87]

[yggdrasil]

Will be following the progress with interest.