The JBL 4345 Club

[Chas]

Do you know if both amps you are using invert phase or are non phase inverting? This is something that always needs to be kept track of in a multi-amp situation. Obviously it is a non issue wen you are using multiple identical amps.

Widget

Agreed. All my amps are noninverting. While the polarity issue is interesting and may certainly pertain to the entire 434X family of monitors when moving from internal passive to biamping with a fourth order network, my interest is primarily with Greg's comment about FR at crossover.

When I have some time, I'll run the RTA and see if there is something there that's measurable. Robh, you've been fooling with this sort of four way set up for a while, have you noticed anything and care to chime in?

[Ian Mackenzie]

Chas,

Yes it is quite confusing when talking absolute polarity.

I recall a while ago comparing the 24 LR slope and I got a similar reaction to you. It works better running both the woofer and mid section postive to positive on both the high and low was amps.

According the the LR filter theory it works better in absolute phase.

If you have the luxury of eq at the crossover point I think you could propably get a similar audible result using different filters.

The 18 db is definately more abrupt and more sensitive to setup. If you like the 24 LR filters in phase then sit back and relax. I also found the boundary effects, room modes and box location quite critical to obtaining a satisfactory midrange transition and you can kid yourself one filter type is better than another with all this. I currently have my system elevated and de coupled some 8 inches off the floor.

At the moment I am trying 12 db LR slopes and will advise on this soon on the result. I also like the XP 200 cards for the 4345.

By the way the 3145 stock network introduces significant insertion losses into either biamp or full passive mode so you are best to bypass the switch completely.

[Zilch]

When I have some time, I'll run the RTA and see if there is something there that's measurable.

Nearfield (1/4"), you'll be able to document the performance of the individual drivers.

At that frequency, I don't know how to get the summing absolutely other than ground plane, but some compromise position between the drivers seems to give a reasonable approximation....

[Chas]

Nearfield (1/4"), you'll be able to document the performance of the individual drivers.

At that frequency, I don't know how to get the summing absolutely other than ground plane, but some compromise position between the drivers seems to give a reasonable approximation....

Cool, I'll give it a whirl, Zilch. Hey, I'm new to this RTA stuff, what level pink noise do you run at?

[Zilch]

That close, you gotta dial the SPL way down so as not to overload the mic and input. It'll sound like a whisper from normal distance. Takes some experimentation to get into the normal reading range. Start low. I use -10 dB for nearfield, typical.....

[Robh3606]

Hello Chas

What kind or RTA do you have?? I have an Behringer 8024 and what I would do is set it up 1- 2 meters away and use pink noise. You can easilly see what the correct polarities are by the suck out at 300Hz when they are not correct. With the 4344's when I was running the M552 with 24dB slopes I had all the drivers in phase. I am using the DX-1 with 12dB slopes now and have the 2235 out of phase with the rest of the drivers like the original crossover.

Rob

[Chas]

Hello Chas

What kind or RTA do you have?? I have an Behringer 8024 and what I would do is set it up 1- 2 meters away and use pink noise. You can easilly see what the correct polarities are by the suck out at 300Hz when they are not correct. With the 4344's when I was running the M552 with 24dB slopes I had all the drivers in phase. I am using the DX-1 with 12dB slopes now and have the 2235 out of phase with the rest of the drivers like the original crossover.

Rob

Behringer DEQ2496. Thanks for your input, Rob. Did you notice anything funky at the LF/MF crossover point when using fourth order (or other) filters? Nice to see that your experience matches what I am hearing.

I have a university student studying directly upstairs from my listening room, so I'll have to wait until the weekend before I can give the RTA a try.

I am still intrigued by GT's comment about the LF/MFfilter design, he mentioned it would have to be non-standard. :dont-know

[richluvsound]

Hi Chas,
thanks for post suggesting that perhaps that I could post a thread to document the build of my 4345's. I had thought about it before and your reguest finally gave me the courage to do so.
I started out wanting to build the L 300 , the first JBL's I ever heard.
I lived in Canada for 20 years so I grew up with a taste for warm snapping bass and crisp ,vapourous highs.I spent 10 years as a DJ in Edmonton surrouned by JBL and BJW. I have fond memories of the after parties that took place when the punters had gone home and I could just sit on the dance floor and listern to the music I loved.
Anyway , I moved back to England to Study Art and now live and work as profesional artist in London. I have 2000 ft2 studio ,so some weedy little bose
satalite system just aint gonna do it. I listern to music from when I wake up until I go to bed ( itunes).I spend alot of time alone painting ,so my sound is by bestfriend.

So yeah! I stumble across this forum and I have'nt looked back since.I did have a little fling with Klipsch. They were a nice sound ,but not for me .They made my ears tired after short time of listerning to them.
There is just something about JBL that keeps me coming back. I'm not a E.E
so I can't justify the attraction with graphs and equations. They sound moves me thats all can say .
There are some very talented people on this site and they know the theory inside out.But, one thing shines through stonger than the facts and figures , and thats ..... PASSION!
I have been given all the support one needs to tackle a project like this, without which, I'd still be dreaming instead of building.
Guido is doing all the electronics and reconing and I'm building the boxes. I will ask Guido to post his progress as well.
I just tried to upload some picks ,seems I need to resize the files. so i'll have to ask for help on this too !
Rich

[Guido]

Hi Rich

Look here for picture posting advice:
http://www.audioheritage.org/vbullet...read.php?t=817

Why don't you start a own thread?

You should have the first packages by the end of this week.

[Chas]

Hi Rich and welcome. I look forward to hearing about your progress. 4345's ought to be just the ticket to fill 2000 cu. ft.!
Charles.

[JMD]

Hello to everyone,
The Slovakia in the middle Europe has big concentration JBL 4345

I've bought tree pairs of studio monitors from National Radio in Slovak Republic. I'd like to ask you to tell me if these serial numbers are corect:

Se. No.: 12759 - JBL 4345
Se. No.: 12690 - JBL 2245H
Se. No.: 15539 - JBL 2122H
Se. No.: 14891 - JBL 2421B
Se. No.: 11106 - JBL 2405H
+
Se. No.: 12676 - JBL 4345
Se. No.: 12844 - JBL 2245H
Se. No.: 15449 - JBL 2122H
Se. No.: 14203 - JBL 2421B
Se. No.: 11587 - JBL 2405H
___________________________________________

Se. No.: 12675 - JBL 4345
Se. No.: 12052 - JBL 2245H
Se. No.: 15535 - JBL 2122H
Se. No.: 14389 - JBL 2421B
Se. No.: 11593 - JBL 2405H
+
Se. No.: 12775 - JBL 4345
Se. No.: 13967 - JBL 2245H
Se. No.: 15509 - JBL 2122H
Se. No.: 14948 - JBL 2421B
Se. No.: 11137 - JBL 2405H
___________________________________________

Se. No.: 12631 - JBL 4345
Se. No.: ? - JBL 2245H
Se. No.: 14693 - JBL 2122H
Se. No.: 14226 - JBL 2421B
Se. No.: 10248 - JBL 2405H
+
Se. No.: 12752 - JBL 4345
Se. No.: 15217 - JBL 2245H
Se. No.: 14574 - JBL 2122H
Se. No.: 14846 - JBL 2421B
Se. No.: 11082 - JBL 2405H
___________________________________________

My frieend has bought next two pairs fo monitors:

Se. No.: 12475 - JBL 4345
Se. No.: ? - JBL 2245H
Se. No.: ? - JBL 2122H
Se. No.: ? - JBL 2421B
Se. No.: ? - JBL 2405H
+
Se. No.: 12637 - JBL 4345
Se. No.: 13929 - JBL 2245H
Se. No.: ? - JBL 2122H
Se. No.: ? - JBL 2421B
Se. No.: ? - JBL 2405H
___________________________________________

Se. No.: 12756 - JBL 4345
Se. No.: 12682 - JBL 2245H
Se. No.: ? - JBL 2122H
Se. No.: ? - JBL 2421B
Se. No.: ? - JBL 2405H
+
Se. No.: 12612 - JBL 4345
Se. No.: 13712 - JBL 2245H
Se. No.: ? - JBL 2122H
Se. No.: ? - JBL 2421B
Se. No.: ? - JBL 2405H
___________________________________________


Thanks


Bohdan

[Mr. Widget]

The Slovakia in the middle Europe has big concentration JBL 4345

I've bought tree pairs of studio monitors from National Radio in Slovak Republic.

So that's where they all went...

Thanks for checking in and letting us know. Maybe someone here will be able to tell you about the serial numbers, though I expect that like most of JBL's historical record the Northridge earthquake may have taken this from us as well.


Widget

[boputnam]

The Slovakia in the middle Europe has big concentration JBL 4345...

:shock:

Holy-smokes. I am speechless. Golly-gee-whiz.

- How did they find their way there?
- Where were they, before?
- What condition are they in?
- Have their drivers been refurbished?
- Can you PLEASE post many pictures!!??

Now, I really know where Disneyland is.

[JMD]

Hello Boputnam

All pairs the JBL 4345 are complete originate - original speakers. Monitors are in good condition. One pair JBL 4345 I'm using at home in the Bratislava capital of Slovakia (60km near the Vienna capital of Austria). Next pairs needs repair of foam surrounds (Bass and Mid-Bass).
The monitors originate from government purchase at early 80th to the National Radio in Czechoslovakia (like BBC in GB). This monitors was used in professional recording and broadcast studios.
Sorry, actually I have only these two pictures:

http://jmd.szm.sk/Audio/Loudspeakers/JBL4345.jpg

http://jmd.szm.sk/Audio/Loudspeakers/18palec.jpg

Sorry my English is rather poor and I apologies for it.


Bohdan

[caladois]

Excepted the cones, they looks very good.