JBL Bi-radial 2342 / 2415H / shouty / frequency-peak ?

[notengewirr]

Questions about my
JBL 4425 equipped with

> 2342 Bi-Radial Horn
> 2415H "salt shaker phase plug"
> Radian 1225/8 Aluminium

listening to this horn speaker sometimes causes 'slightly' peaking resonances in the 3.1kHz range. The 2342 horn seems to be a little "shouty" in midrange with some recordings, especially with femal voices hitting the 3kHz range. Also sampled "hand-claps" or other sounds in this 3.1K range causes this slightly fatigue sound. (this is not caused by my listening room !)
If i compare the 4425 to all my headphones (Audeze Lcd-2, AKG K701, Beyerdynamic T1,Sennheiser HD650) i can locate this 'hot' 3kHz area, but without the slightly nerving & peaking resonance.
My 4425 is stamped 1988 and original fitted with the 2415 Magnet. I do not have a 2416 with slit slot phase plug for comparsion.
The problem was also with the orig. Titamium diaphragm.
The freq. network and the pads are in perfect shape, no scratching noise from the mid/high pads.
So what cause this little frequency dip ? Is this a generally problem of this 2342 bi-radial design , or perhaps caused by the 'older' 2415 salt shaker phase plug ?
On different JBL 4425 freq./spec-sheets there is a very little dip in exactly that area.
Is there a side by side comparsion between the 2342/2344 with same drivers in it ?
...or do all horns generally suffer from this problems ?

[Earl K]

The roughness in response is caused by the diffraction slot used in the 2342 biRadial ( not the 2415H driver ).

Here's a timely thread for you to read ( that I just resurrected today ).

Yet Another 4425 DIY


If I were you ( & you're willing to try out a solution using your own cash ), I would build the final incarnation of the network that Espen ( jerv ) designed ( at the end of the linked thread above ).

From my perspective, it addresses some of the necessary issues ( by implementing LCR notches targeting 2 of the peaky frequency areas ).

[Ian Mackenzie]

Schematic of the 4425mk11 using the 175nd hf driver

http://www.audioheritage.org/vbullet...0&d=1112331484

You could try that.

Don Smith has blogged on the problems associated with the impedance using 2344 style horn impacting on the smoothness of the response. As l recall the exponential loading of the horn is not sufficient and the motional impedance modulation of the voltage drive causes the roughness. The problem appears worse in the smaller horn.

Don Smith has suggested Biamp with a negative impedance amplifier (like the First Watt F4)

It might be easier to simply upgrade to a better loudspeaker

There are numerous small near field monitors out there these days not to mention the Jbl 7 series
http://www.jblpro.com/www/products/r...i#.WpWjmXDZWEc

[notengewirr]

thanks for the reply !

now i'm playing here with a Sonnox Audio-Unit Plugin EQ addad to the player software pureMusic.
Sweeping arround the freq-band with pink- or white noise was helpful to locate the 'bad' resonance frequency.
Setting a little notch exactly at 3.1kHz reduces the main (bad) resonance successfully.
adding a shelf above 16-20kHz helpes to rise up the slight roll-off of these horn design.
Much ! better now !
So there is a generally issue with this horn design ?

[Earl K]

SNIP <> So there is a generally issue with this horn design ? <> SNIP

There's a real renaissance of love for wide-pattern waveguides ( as fitted into the 4430, 4435, 4425 etc. etc ) .

This is very apparent over at AudioKarma .

I figure this is partially driven by consumer lust for JBL's M2 .

In balance, the strengths ( of those older wave guides like the 2344 ) out-weigh their design weaknesses ( of which I count the horn slot and it's effects on response ).



BTW; Here's a look-see at an original 2415H on the H290B biRadial ( these are mine ).
- Pretty smooth ( raw ) response .

.

Here's it's mate loaded with the Radian 1225-8 diaphragm ( an old-style Altec loading cap was used to seal-up the diaphragm ).


- It would appear the Radian diaphragm doesn't much like this 2415H body ( an opinion based on seeing the rougher response ).

[notengewirr]

There's a real renaissance of love for wide-pattern waveguides ( as fitted into the 4430, 4435, 4425 etc. etc ) .

and that's why I'll stay with the 4425 !
I have heard many speakers in the last few years. Many were from the studio sector, many were high-end products from renowned manufacturers.Even the most expensive speakers could not really convince me in all disciplines.
Every speaker is just a compromise. That's exactly how it is with headphones...Every speaker or HP sounds a little different, and only very few hit the bull's eye. (correct translation ? ) :-)
And for the price I paid for the speakers a few years ago, these are unbeatably good!
Yes, the fully active M2 would certainly be the end of the flagpole.
Because i have enough good and identical power amplifiers, I'll eventually try to drive the 4425 completely active.

Is there anyone here who has tried this even on a 4425 ?
The 4430/35 have this "crossover" option.

@ Earl K

is the rougher respons of the radian perhaps caused by the Altec's cup ?
The Radian cup of the 1225/8 is "rubber-seald" and the plate& housing is very sturdy plastik.
The Radian housing is less resonant. If you tap the jbl's back-cover with your fingernail, it sounds like a yogurt cup. Even the diaphrgm sounds a bit like that...
Perhaps thats one of the reasons why the radian sound a bit less fatiguing/resonant.

[Earl K]

<>SNIP<>

@ Earl K

is the rougher respons of the radian perhaps caused by the Altec's cup ?
The Radian cup of the 1225/8 is "rubber-seald" and the plate& housing is very sturdy plastik.
The Radian housing is less resonant. If you tap the jbl's back-cover with your fingernail, it sounds like a yogurt cup. Even the diaphrgm sounds a bit like that...
Perhaps thats one of the reasons why the radian sound a bit less fatiguing/resonant.

The Altec loading cap that I used is ( is the older type ) made of very dense phenolic plastic / so I doubt there's any significant contribution from it to the response seen.

Additionally ( & as non-scientific that my comparison is ) , the Radian diaphragm is 5db hotter in the 10-14K region ( as measured ).

- That's really quite a huge difference / which can't be readily explained at this time .

FYI, IMO, you're doing the right thing.
- ie; Figure out the response irregularities ( peaks ) and then deal with them ( EQ them flat through either passive or active means ).

[Earl K]

Andreas,

Here's another one of your threads on the 4425 ( just for faster reference ).

Plus here's another reference thread ( in case you're wanting/wishing to upgrade your 4425's to Beryllium drivers in the future ).

Click the pic!



You asked for a comparison of some drivers on the 2344 vs the 2342.

Here are some traces belonging to other peoples threads (ie; Guido & Jerv )



One can see that the diffraction nulls ( suckouts ) found on the 2342 are no worse ( & they might even be called better ) when compared to those found in the 2344 BiRadial.

Guido's traces were turned into frd files ( via tracing software ) and are from his thread called 4435 Conversion to TAD 2001

[notengewirr]

Earl K

thanks for your effort ! Great work ! i know the thread and guido too ;-)
so in all graphs i can see a little peak in the 3K range !
i think in my situation the 4425 is definitly the better choice. My listening room is only 16qm and the distance from my listening position to the speakers is max 2.8m !
The phase allign (right word? ) is better than with 'bigger' systems , and i believe much better than with systems using more than 2 drivers.

I added some pics of my "modified" 4425 ;-)
We found out the back-plate of (most) older JBLs are flimsy and causes bass resonances ! So we added a second plate glued&screwed on. The design is following the black front edges. So it looks like a "sandwich" design.
The result is a slightly better response in the "upper bass -kick-bass" area. The next thing we replaced was the flimsy connector. Replaced by a sealed metal speakon !
The heavy custom made metal stands design was taken by a TAD speaker i found in the web.
Filled with fine sand this heavy stands can be adjusted in hight and degree very exactly to my listening position. Ok, it is not 100% original 4425, but it is a very unique "old 80's butt-cheek-speaker" now .
look at the pics !

[22214]

and that's why I'll stay with the 4425 !
I have heard many speakers in the last few years. Many were from the studio sector, many were high-end products from renowned manufacturers.Even the most expensive speakers could not really convince me in all disciplines.
Every speaker is just a compromise. That's exactly how it is with headphones...Every speaker or HP sounds a little different, and only very few hit the bull's eye. (correct translation ? ) :-)
And for the price I paid for the speakers a few years ago, these are unbeatably good!
...

.. I am with you.

I think your 4425 is a very good choice to listen music.
Powerful strong and tight bass with fast higher mids and highs … especially in your ‚small‘ listening room.

If you change from passive to active imo you kill the internal harmony of this monitor … which was also tuned by your 6 wall room (… result of room gain).

... Sonnox Audio-Unit Plugin EQ ...
Did you use a ‚spl qure‘ too ?

[Ian Mackenzie]

I think it comes down to being able to set up an active crossover to replicate the passive crossover technically.

That requires sophisticated test equipment and skills to design the active crossover to do everything the passive crossover does regardless of being analogue or DSP.

BTW you might be surprised at what a series inductor on the woofer does to the bass response and how the woofer inductance a screws up an ideal passive crossover.

Unfortunately going active is not easier and is not plug and play.

In diy terms you might get an okay result actively fudging standard crossover slopes but to get the best result out of the loudspeaker requires a lot more work.

[notengewirr]

@ Ian Mackenzie
I fully agree with you !
For that reason, I will leave the speakers the way they were originally designed by Greg Timbers.And the little peaks I eliminate with some phase linear EQ.
Now i'm trying the Waves phase linear EQ also with very good results.

[notengewirr]

I sold the SPL EQ last summer. The "sound" was to colored, and the parameters can never be set so accurately.

.. I am with you.

I think your 4425 is a very good choice to listen music.
Powerful strong and tight bass with fast higher mids and highs … especially in your ‚small‘ listening room.

If you change from passive to active imo you kill the internal harmony of this monitor … which was also tuned by your 6 wall room (… result of room gain).

... Sonnox Audio-Unit Plugin EQ ...
Did you use a ‚spl qure‘ too ?

[22214]

I think it comes down to being able to set up an active crossover to replicate the passive crossover technically.

That requires sophisticated test equipment and skills to design the active crossover to do everything the passive crossover does regardless of being analogue or DSP.

BTW you might be surprised at what a series inductor on the woofer does to the bass response and how the woofer inductance a screws up an ideal passive crossover.

Unfortunately going active is not easier and is not plug and play.

In diy terms you might get an okay result actively fudging standard crossover slopes but to get the best result out of the loudspeaker requires a lot more work.

I agree with you ..

[gibber]

i wasn't aware of the fact JBL used a saltshaker/pepperpot style phase plug at any ime. Are there other examples?
Can anyone point to pictures of the (open) 2415 or have own pics to share?

Ralph