2123H vs 2122H in a 4343 monitor

[Guido]

I calculated the following parallel notch (series with speaker)

C = 68uF
L = 0,22 mH
R = 6,8 Ohm

What do you think?

What power need the Resistor to have?

[4313B]

How does it sound?

Start with a 10W and see if it gets too hot.

Use your program there to see how varying the resitor value affects the band.

[luxmanlover]

I'm definately not getting something here. JBL shows the 2123H/J as being dead flat from around 400 Hz - 6000Hz. Is JBL telling fibs or did I make a wrong turn somewhere?
Kelly

[Guido]

Look at your smilies....
Again this 2 Beers thing

I need to organize the components. Wait until next week. I will post the results.

The 2012 sound perfect in the 4343 but always I have this feeling of disturbing level in the 1 KHz region. Especially at high level listening.

We will see

[Tom Loizeaux]

I recently learned that JBL, in an effort to fine tune the 4343, modified their 250 Hz crossover card for use in their 5235 active crossover, and developed a card specifically for the 4343. I read that they found that the 2121 wasn't dropping quite fast enough and added a touch of signal to the 2235 - creating a very slight rise at their crossover frequency (250 Hz) when used in the bi-amp mode.
This implies that JBL engineers carefully measured the response of the 4343 and felt they could slightly improve it's response in the bi-amp mode by tweaking the response from their active crossover.

I use this set up with my 4343s and find them very smooth and very satisfting.

Tom

[4313B]

"I use this set up with my 4343s and find them very smooth and very satisfting."

Yeah, but is it less filling?

[4313B]

voltage drives

[Earl K]

Hi Kelly

First - the 2123 is a great sounding transducer. Is the 2122 better ? I don't know - I've only listened to the le10 (a/h), 2123 and the 2012 ten inchers. Those are the types I own. These 3 types, have unique strengths and weaknesses - the 2122 - I'm sure woud garner a similar description .

Second - about the 2123s' response curve;

The 2123 does have quite a flat response curve - it's just not as flat as that "idealized" curve in the JBL cut sheet. I don't think JBL is fibbing - it's an "interpretation" . If you read the JBL spec. closely , it does say that no unit deviates more than 2 db ( plus or minus ) from the published curve. Put 2 such deviations side by side and you'll have a 4 db ripple ( peak to reciprocal peak ) . You would see that on an 1/3 octave RTA and you'd hearing would/should pick that up. But, the speaker would still be up to spec.

As far as a rising response. Most of the 2123s that I own have a fairly wide bulge/blip up around 1K ( 2/3 octave wide ). After that, if they are measured directly on axis, they are quite flat out to 5 K ( as in the published spec. ) . If the speaker is measured 45° off axis - well then, they won't measure flat. They exhibit a slow roll-off at around 1600 hz . It can be argued that the speaker has a rising response ( on axis ) - though this ( rising response ) has a net result of creating a flat response ( on axis ) .

You ought to consider buying True Audios' RTA software ( or some other competitors version ) - that way you can measure the response curves of your specific speakers. Having that respone info helps one design proper passive crossovers - etc. .

regards <> Earl K

[4313B]

Originally posted by Earl K
First - the 2123 is a great sounding transducer. Is the 2122 better ?

The 2121 is best in the 4343. The 2122 is best in the 4344 and 4345. The 2123 is best in the 4344 Mk II. The 2123 is a great sounding transducer, we've been over this numerous times.

Originally posted by Earl K
I don't know - I've only listened to the le10 (a/h), 2123 and the 2012 ten inchers. Those are the types I own. These 3 types, have unique strengths and weaknesses - the 2122 - I'm sure woud garner a similar description.

Yes, they all have their specific design goals and their specific intended applications.

Originally posted by Earl K
You ought to consider buying True Audios' RTA software ( or some other competitors version ) - that way you can measure the response curves of your specific speakers. Having that respone info helps one design proper passive crossovers - etc.

True, if one is seriously going to start designing their own filters it would be quite beneficial to know the electrical and acoustical parameters of the intended transducers.

As far as the 4343, 4344, 4345, and 4344 Mk II go, simple inspection of the transducer TS parameters hint that none of these transducers are interchangeable electrically. I know some engineers at JBL who are unwilling to even suggest swapping an LE5-10 (round wire voice coil) with an LE5-11 (ribbon wire voice coil), that's how seriously they take the electrical and acoustical characteristics of each transducer. Like I posted before, just try your ideas and see what happens. You might actually like the results.

[4313B]

Notice the differences in the Re and Le values of the three different transducers. Using a spice package one can model these transducers and see the electrical effects each one would have on a particular filter.

The other parameters hint at what each transducer can do. Obviously the 2122 is the least efficient with it's heavier moving mass. It will exhibit the lowest low frequency extension and it's Xmax figure shows that it will remain linear in it's output at those lower frequencies. The 2123 gives up this characteristic to attain maximum efficiency in a higher frequency band.

[Guido]

MODEL FS QTS QMS QES VAS EFF
2012H 60 0.22 4.34 0.23 31 3.47
PE XMAX RE LE SD BI MMS
300 5 4.65 31 13.9 25

From the parameter the 2012 fits better than the 2123 but the rising response.....

[4313B]

Yep, hence the need to also know the acoustical response. The 2012 is a very cool transducer

[GordonW]

Dang, the 2012 has a 5mm Xmax? Man, THAT oughtta HURT you in the midbass. What woofer/mid/tweeter combo could keep up with THAT kind of acoustic output (300 watts/5mm excursion)??

Sounds like someone should make up a monitor with dual 2242HPL's, a 2012, and something mondo for horns for mid/highs...

Regards,
Gordon.

[4313B]

Originally posted by GordonW
Dang, the 2012 has a 5mm Xmax? Man, THAT oughtta HURT you in the midbass. What woofer/mid/tweeter combo could keep up with THAT kind of acoustic output (300 watts/5mm excursion)??

Sounds like someone should make up a monitor with dual 2242HPL's, a 2012, and something mondo for horns for mid/highs...

Regards,
Gordon.

Are you hinting that I should try a 2012 with my 2242's and see what happens?
Frankly, I don't have the physical room for such unless I build it all in the backyard

[Earl K]

Hi Guido

What crossover modifications have you done with your 43xx clones to flatten the 2012s' rising response curve ?

( I've looked through most of your postings but can't find this info if it was ever posted )

thanks <> Earl K