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subwoof
09-10-2003, 12:47 PM
Anyone have the experience of using the 2123 instead of the 2122 in the 4343 monitors?? Aside from the obvious efficiency difference any suggested changes to the network? sub...:0)

4313B
09-10-2003, 01:39 PM
Originally posted by subwoof
Anyone have the experience of using the 2123 instead of the 2122 in the 4343 monitors?? Aside from the obvious efficiency difference any suggested changes to the network? sub...:0)
Rather than go on yet another rant ;)

Look at the 4344 Mk II schematic to see how JBL delt with the rising response of the 2123 in a 4343/4344/4345-type system :)

4313B
09-10-2003, 01:43 PM
4344 MK II

Guido
09-10-2003, 03:19 PM
Giskard,

please give some advice to the schematic. It's a charge coupled and I'm not into this as many other maybe.

What is the important difference between both networks (4343, 4344)?

Where do you have the info of rising response of 2123? In the spec sheet JBL show a toooooo flat response.

Do you have a own spec sheet? Please post.

4313B
09-10-2003, 03:56 PM
"Where do you have the info of rising response of 2123?"

In my head. My ears have stopped ringing :D

Here are the voltage drives of the MF passbands in the 4343 and 4344 Mk II. The 4343 uses the 2121, the 4344 and 4345 use the 2122, the 4344 Mk II uses the 2123.

Guido
09-10-2003, 04:05 PM
If this is the voltage drive then the response of the 2121 is falling with rising frequency?
I'm confused. Thought it is rising:confused: :confused:

Heeelp!

4313B
09-10-2003, 04:20 PM
Originally posted by Guido
If this is the voltage drive then the response of the 2121 is falling with rising frequency?
I'm confused. Thought it is rising:confused: :confused:

Heeelp!
Don't confuse me Guido ;)
The 2121 has breakup issues due to it's soft inverted center dome. The 2123 has a rising response so the 4344 filter attenuates it faster.

Anyway, just pop a 2123 into a 4343 and see how you like it. You might think it's just fine. Try a 2122 and see how you like that one too. Seriously, it's the only way to see which one you prefer.

Guido
09-10-2003, 04:37 PM
:banghead: We should sit together with a German Beer and discuss this personally.

I went through this many times as you know that I am using a 2012H in my 4343. They have rising response from 800Hz and up. At 1200Hz its plus 6dB.

You once posted a response curve of the 2122H. It have slightly the same problem between 800 and 1000Hz. Beyond 1000Hz it's solved. I never saw the curve of the 2121.
So if my 4343 network rises the response than I have a peak in my 4343 response. I think I do hear that.
What to do?

And how do you calculate the voltage drive? What program is it?

Thanks!

subwoof
09-10-2003, 06:41 PM
OK - I'm impressed...:)

Second question for the JBL TECHBOT: Do you have the part number for the ME150H recone kit? My JBL service center doesn't have it in his consumer listings ( I assume due to the overseas use only ) and unfortunately we cannot call carla at JBL anymore...:(

I have a pair of 2226H frames they could drop in - this should be an improvement over the 2235H if I'm going to do all the other mods...

Thanks in advance!

PS to guido - Zwei Deutch bieren sounds good to me...:)

4313B
09-10-2003, 07:01 PM
Hello subwoof :)

Both the ME120 and ME150 are marked "Cone/Diaphragm Kit Not Available. Defective Speaker Should Be Replaced".

subwoof
09-10-2003, 07:33 PM
Figures on the recone kit....they pull the "FSO" with the 1400Nd and mose of the Neodymium stuff too....Oh well....

4313B
09-10-2003, 09:38 PM
Originally posted by Guido
:banghead: We should sit together with a German Beer and discuss this personally.

I went through this many times as you know that I am using a 2012H in my 4343. They have rising response from 800Hz and up. At 1200Hz its plus 6dB.

You once posted a response curve of the 2122H. It have slightly the same problem between 800 and 1000Hz. Beyond 1000Hz it's solved. I never saw the curve of the 2121.
So if my 4343 network rises the response than I have a peak in my 4343 response. I think I do hear that.
What to do?

And how do you calculate the voltage drive? What program is it?

Thanks!
You might want to try a little notch filter around 900 Hz then. Search the web for parallel and series notch filters. You'll want to use a parallel notch filter which goes in series with the transducer.

You can measure the voltage drive of a filter with a voltmeter and an oscillator. You can measure it using the actual transducer or with an 8 ohm or 16 ohm dummy load. Obviously you will get different results depending on which you use ;) Using transducers is fine but you should also use a dummy load to get a proper "mapping" of the filter.

Any spice software package should be able to allow you to model filters. I think pspice still has a free version or student version that should be adequate.

Here is the standard test setup for running voltage drives on JBL networks:

http://www.jblproservice.com/pdf/Network%20Schematics/Standard%20Test%20Fixture.pdf

***

Oh, and if you are going to get serious about modeling filters for different transducers then you will want to create the equivalent circuits for the transducers you are planning to use. Equivalent circuits can be determined from the TS parameters. For instance, here is an example of the equivalent circuit of a 2235H:

luxmanlover
09-10-2003, 10:04 PM
If that's the kind of stuff I need to know in order to design passive filters in PSpice, I'd better stick to active ones.
Kelly

Guido
09-11-2003, 04:31 AM
Originally posted by subwoof
OK - I'm impressed...:)

and unfortunately we cannot call carla at JBL anymore...:(

PS to guido - Zwei Deutch bieren sounds good to me...:)

Whos carla?

Your German is good! Sounds like you have been on the oktoberfest once ;)

Guido
09-11-2003, 04:31 AM
Thanks Giskard!

Guido
09-11-2003, 04:25 PM
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
09-11-2003, 04:33 PM
:cheers:

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
09-11-2003, 04:46 PM
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
09-11-2003, 04:46 PM
Look at your smilies....
Again this 2 Beers thing :p

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:hmm:

Tom Loizeaux
09-12-2003, 02:59 PM
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
09-12-2003, 03:20 PM
"I use this set up with my 4343s and find them very smooth and very satisfting."

Yeah, but is it less filling? :cheers:

4313B
09-12-2003, 03:33 PM
voltage drives

Earl K
09-12-2003, 08:01 PM
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
09-14-2003, 06:22 AM
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
09-14-2003, 06:34 AM
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
09-14-2003, 07:09 AM
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
09-14-2003, 07:49 AM
Yep, hence the need to also know the acoustical response. The 2012 is a very cool transducer :)

GordonW
09-14-2003, 08:19 AM
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... :D

Regards,
Gordon.

4313B
09-14-2003, 08:33 AM
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... :D

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 :rotfl:

Earl K
09-14-2003, 10:28 AM
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 :)

4313B
09-14-2003, 10:31 AM
Originally posted by 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 :)
Yeah Guido, have you tried the notch filter yet? If so, what's the scoop? :)

Guido
09-15-2003, 04:31 AM
Originally posted by Giskard
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 :rotfl:

Yeah! Build it in the backyard:D

Guido
09-15-2003, 04:39 AM
Originally posted by 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 :)

Until last week I did nothing. The result was good but not perfect.

One thing was this peak in the 1kHz region that I know well from former projects. Peaks in that frequency range become disturbing exactly when listening at higher levels.

So I popped into this thread and asked Giskard for that notch posted above.

Also @ Giskard
With the components I had at home I did a fast and dirty notch.
Cap 50 uF Electrolytic (Ugh!)
Resistor 5,6 Ohm
Inductor 0,25mH

The peak is gone but the sound quality suffered (no wonder with that cap). All in all the mids are more ?punching? without that peak.
As soon as I have the better components I will tell you.

IMO the 2012 and the 4343 is a good combination. But be aware that I never compared (A/B'd) them with a 2121 or 2122.

4313B
09-15-2003, 06:11 AM
Originally posted by Guido
But be aware that I never compared (A/B'd) them with a 2121 or 2122.
Ignorance is bliss and that's a fact. Nothing can take the place of a direct A/B.


Originally posted by Guido
IMO the 2012 and the 4343 is a good combination.
If it sounds good go with it! :)

Earl K
09-15-2003, 06:53 AM
Hi Guido

Until last week I did nothing. The result was good but not perfect.


Does that mean you used/followed the original 4343 crossover component values ?

If it was my project using a 2012 ( and I may be doing this sooner than later ) I would implement/experiment with some of the LC ratio techniques that JBL utilise to "flatten" the midband response curves of their hightech K2 cone transducers. These K2 woofers , most likely ( I've never seen a published curve ) exhibit some portion of a "rising midband response" such as found in your 2012 .

One of those "techniques" is to effectively lower the turnover frequency by increasing the value of the second pole/element in a second order network. The capacitor values JBL plays around with are often 1.5 to 3 times the classical stated "Butterworth" values. The final value of this capacitor ( for a low pass circuit ) really needs to be determined by empirical tuning methods ( or a very good crossover modelling package ). To understand what I'm talking about , study/analyse the LC values for the S3100, 4348, 4344mkII, S9800. It would seem that all these "deep-gapped" woofers need special midband attenuation to give optimal ( flat passband ) results . The 2012 "fits" into this deep-gapped transducer family.

Another technique used to accomodate single area "peaks" ( if they exist at the top end of the pass-band like your 2012 ) is to employ an 18 db /per octave low pass. The trick here is to set the first pole/element (filtering action) just below the offending peak while playing with the LC values of the second & third pole/elements. This will tune the steepness ( or Q ) of the whole roll-over section of the filter. This tuning/tinkering allows you to decide how much to include/exclude the specific area of the offending peak. A quick analysis of the 4344mkII circuit ( for the 2123 mid-bass ) would indicate that something similar has been employed to avoid some of the peaks as found in the 2123h . Here, the first poll/element seems to be set at around 900 hz.


The 2012 would seem to need both of the above design tricks to be engaged to offer a net "flat" power response - for a net 95 db sensitivity from 300 to 1200 hz .

Do you have crossover modelling sowtware ?

regards <> Earl K

4313B
09-15-2003, 07:12 AM
One question Earl? Do you have my phone line tapped? :rotfl:

The staggered poles idea is another solution, which I wasn't going to get into if the notch filter worked. It's definitely nice to see someone really tearing these filters apart and giving them a thorough examination :)

Earl K
09-15-2003, 07:32 AM
Hi Giskard

No phone tap here - though I have relatives in the Cdn security services. I'm sure my border-crossings are well scrutinized. :wave:

regards <> Earl K

Guido
09-16-2003, 05:45 AM
Originally posted by Earl K
Hi Guido


Does that mean you used/followed the original 4343 crossover component values ?

Do you have crossover modelling sowtware ?

regards <> Earl K

I had the original X-Overs and just plugged the 2012 in.

Result was good as I described except the peak around 1k.

I will be travelling next 2 weeks so I can earlist tell the notch results in 2 to 3 weeks.

No, I don't have x-over modelling sw.

If you do some x-over design to fix compensation for the 2012 please let me participate.

Thanks!

Earl K
09-20-2003, 05:46 PM
Hi Guido

Here's something you can look at. This is a response curve from one of my 2012h mids as used in one of my companies small boxes. This is full range pink noise run into the woofer section. The box has an approx. effective volume of .65 cu' with a 110hz tuning.

As you can see, the response curve is actually a lot flatter than the JBL cut sheet would lead one to believe. Of course the original 1985 , 2123h cut sheet shows a straight line - and that's not correct.

You can easily see a 2/3 wide - 3 db high bump in the 800 to 1100 hz area. I haven't yet run sine wave test to see what frequencies this "bump" starts & stops at.

Be aware that this RTA response is taken with the enclosures' protective foam backed - metal screen still in place. The mic was on axis to the center of the 2012.

I see this driver as needing similar treatment as the 2123h as used in the 4344mkII. You might be able to add a third pole or element ( inductor ) to your existing crossover - but since the present values are chosen for a 2 pole design - only trial & error or someone with design software can give you the needed value . If it was me - I'd try a .5 to .7 mh inductor in line ( easy for me to say since I own some ) with the midbass circuit. I haven't done any math on what that "T" pad is doing to the circuit impedance - but I'd be inclined to wire in the new inductor just before the 16 ohm Lpad.

It seems I have the necessary parts on my bench that will allow me to wire up a close approximation ( including the Tpad) of this modified 3143 . I'll let you know when that happens and what the results are .

:cheers: ,> Earl K

Guido
09-21-2003, 05:14 PM
Thanks Earl K!

This driver looks good. It isn't as bad as I thought.

But anyway it has that peak at 1 k.

I would appreciate the results from your test.

Earl K
09-21-2003, 05:31 PM
Hi Guido

- You're correct - the published JBL response curve doesn't do this driver justice.

Here's a pic of my todays' efforts to see what happens when the second pole ( the capacitor ) in a 2-pole low pass is increased beyond the "text-book" butterworth value.

This picture is taken after I built up the low pass portion of the midbass section of the 3143 crossover. I didn't have the exact LC values but I came very close. Instead of a 1.7 mh inductor - I used my 1.6 mh aircore type.
The capacitor was 22uf instead of the 20uf in the original circuit. The "T" pad
was builtup from 2 x 2.5 plus 30 ohm shunt resistor instead of the twin 2 ohm with 30 ohm shunt. The Lpad was a stock 16 ohm JBL unit.

- I obtained this curve by adding 15uf to the existing 22uf for a total of 37uf.

- As you can see - this method works quite well .

- My next posting will show the 2012h curve with my version of the stock values .

- This curve gives 1K as minus 3.75 db referenced to 500 hz while 1.6k is minus 13.75 - also referenced to 500 hz. The low-pass crossover slope ( between 800 and 1600 hz ) is 13.75 db per octave .

- Running pink noise through this 2012h as I added the additional capacitor was very enlightening. It was very obvious a " lot of hi-mid energy was disappearing as the capacitor was clipped into place .

- This is a "Simple - Stupid" approach to the 900 hz peak. It's the one I'll use if I ever build a 43xx thing and if I don't triamp. If in your shoes - I'd first try adding a 15uf capacitor in parallel to the existing 20uf cap. Give it a listen.

- It may be just the ticket for integraton to a 4343 system .

regards <> Earl K

Earl K
09-21-2003, 06:07 PM
Hi Guido

- Here's the curve that shows the resulting peak when I use the 2012h with the mock-up of the midbass , lowpass section of the 3143 xover. The 900 hz peak is quite evident.

It's worth pointing out that the "Q" of your circuit is now a little "off". Just dropping in the 2012h without some other changes seems to result in a bit of sagging in the middle of the passband. This becomes more evident when the Lpad is used a lot. Where do you usually set the Lpad ? ( as a percentage of its' rotation ). Altering the values of the resistors in the "Tpad" may mitigate this effect. I won't know until I get to my local electronics surplus store later this week.

<. Earl K

Guido
09-22-2003, 04:31 AM
Hi Earl!

Great work!

This looks very good and very easy. I will try this within the next days.

2 Questions:
What was the peak in dB when you just connected the 2012 to the original x-over mockup?

Where should I connect the additional 15 uF cap? Just parallel to driver or do you think I should dismount the whole xover network?
Maybe you can try with your test installation?


I usually set the LPad middle, means 0dB.

Earl K
09-22-2003, 05:00 AM
Hi Guido

Parallel the 15uf capacitor to the existing 20 uf capacitor - it's found in the midbass section of the 3143 crossover.

I can't remember offhand how large that peak was when referenced to 500 hz. It was at least 3 db - I can remeasure later today since this mockup is still on my bench.

regards <> Earl K

Earl K
09-22-2003, 08:12 AM
Hi Guido

- The peak was 3 db.

- My mistake ; the additional cap I added to my mockup circuit was 22uf not 15uf. So start with an additonal 18uf cap and then add a little more capacitance on 2uf increments. Tune this by ear. FWIW ; I just threw the 15uf ontop of the 44uf ( for 59uf total ) and it started the rolloff around 600 hz ( this is just mentioned as an indicator of the effects of adding even more capacitance. )

- a word of caution, there's no free-lunch to this exercise. At some point changing the LC ratios like this will result in the creation of an underdamped resonant circuit . As a guideline for how far one can wander away from the path ( of years of proven circuit design ) - look to JBLs' own schematics for guidance . They don't seem to get much beyond doubling the text-book capacitance value.

regards <> Earl K

GordonW
09-22-2003, 09:34 AM
Yep, at some point, you have to start looking at increasing the series inductor value as well. Damping is important to maintain... something I've personally learned the HARD way here and there!

Regards,
Gordon.

Guido
09-22-2003, 12:28 PM
Hi Earl!

I changed that cap value in my SIMPLE Network calculation programm.

The programm shows me rising midband response with increasing the cap value.

Am I wrong with something? Or is my program too simple.

4313B
09-22-2003, 12:56 PM
Hi Earl,

Can you please post impedance curves of the two 2012H's that you have for us?

Thanks :)

Earl K
09-22-2003, 02:05 PM
Hi Giskard

Because of present show duties , I'll be unable to provide full motional impedance curves for a 2012h (minus the circuit & enclosure ) until sometime next week .

- But having said that - I do have some notes I made yesterday .

-The following values are AC circuit impedance measurements ( in box with circuit ):

With the 16 ohm Lpad "fully open"

400 hz - 4.5 ohms
800 hz - 4.9 ohms
1000 hz - 7.2 ohms

With the 16 ohm Lpad " approx" 1/2 on

400 hz - 5.2 ohms
800 hz - 4.5 ohms
1000 hz - 6.7 ohms

1.6 mh inductor - with a DCR of @ .4 ohms

As one can see from the above values this circuit is far from being optimized for a 2012h. The changing impedance ratios induced by rotating the Lpad show that. I did add a 1 ohm resistor in series with the 2012h this morning to see its' effect but ran out of time to do real measurements. A quick check with the RTA showed a bit of leveling or improvemet in the pass-band.

This is why I asked Guido how much rotational room he has left in the Lpad.

I suspect the Tpad needs reworking & perhaps a bit of series resistance after the Lpad. Hopefully someone with modelling software can figure this out. I would have to do this empirically - which I don't mind doing - but not until next week .

Guido ;

I don't know what you might be doing different without having the actual 3143 circuit on which to make AC impedance measurements. I would also need to be familiar with the software you own .

regards <. Earl K

Guido
09-22-2003, 02:25 PM
Originally posted by Earl K
Guido ;

I don't know what you might be doing different without having the actual 3143 circuit on which to make AC impedance measurements. I would also need to be familiar with the software you own .

regards <. Earl K

Take your time Earl.

I'm sure you will come up with a good solution for optimizing our 2012H transducers.:)

Looking forward to it

4313B
09-22-2003, 02:37 PM
Ok Earl, thanks. :)

"Hopefully someone with modelling software can figure this out."

Well, actually my electroacoustic model of the 2012H is coming up short. Hopefully a couple of free air impedance plots will clear it up. :)
Whenever you happen to get to it is fine :)

GordonW
09-22-2003, 07:56 PM
Originally posted by Guido
Hi Earl!

I changed that cap value in my SIMPLE Network calculation programm.

The programm shows me rising midband response with increasing the cap value.

Am I wrong with something? Or is my program too simple.

Guido, try making the 2012's LP inductor bigger instead... might be a damping thing you're already running into. Let us know if that models any better... I'm guessing it will, because that will both (1) decrease the effective F0 of the filter (lower crossover point) and (2) decrease the Q (increased damping) of the filter, which will reduce the output at F0.

Try it, see if it works!

Regards,
Gordon.

TimG
09-22-2003, 08:54 PM
I have LspCAD modelling software on my computer. If you can measure impedance, SPL and phase response for the driver in your cabinet I can develop a crossover model for you. The program cannot compute absolute SPL though so it would be good to have a reference SPL such as from the woofer or tweeter to match the levels up. If you can't measure phase I know where I can get a program that can estimate phase response. If would also be helpful to have the existing crossover schematic so that could be included in the model.

Guido
09-23-2003, 04:28 AM
Originally posted by GordonW
Guido, try making the 2012's LP inductor bigger instead... might be a damping thing you're already running into. Let us know if that models any better... I'm guessing it will, because that will both (1) decrease the effective F0 of the filter (lower crossover point) and (2) decrease the Q (increased damping) of the filter, which will reduce the output at F0.

Try it, see if it works!

Regards,
Gordon.

Yep!

I increased the 1,7mH to 2,5 mH (in program).

The result is -3 dB at 1 kHz.

Q at 290Hz is 1,325
Q at 1100 Hz is 0,545

Earl K
09-23-2003, 03:38 PM
Hi Giskard

-Here's the best I can do for impedance plots - for the two 2012h I had here last week.

-These values were quickly taken ( in their respective enclosures ) - before they were sent back to inventory - to be then sent out .

- I don't anticipate seeing these specific units again for some time. So , these values are going to have to suffice as a general impedance guide ( relating to all 2012s ).

-I chose 6.2 ohms as a mean target impedance to restore to. This would be the "working impedance" for the lowpass portion of that midbass section. Motional Impedance checks indicate that I've more or less gotten there by putting a 1 ohm resistor between the hipass section and the lowpass section of the midbass circuit. Won't really know how it works with that preceeding section without buying the inductor needed for the highpass portion - ( and I'm not planning on that anytime soon ).

- If I was starting with a clean sheet - I'd build up the circuit around an 8 ohm Lpad . A 16 ohm Lpad with these 2012 is just too wobbly ( the Lpads' impedance tracking is all over the place ) . ie - without some resistive compensation - it' changing the "Q" of the filter as well as gain.

regards <> Earl K

4313B
09-23-2003, 03:58 PM
Ok, thanks Earl! :)

GordonW
09-23-2003, 09:53 PM
Guido, IIRC, that crossover response curve there, looks very much like the OPPOSITE of the 2012 response curve... so, the SUM of that and the driver (as in working together) MAY come out just about dead-on flat.

I'd be really inclined to try that, and see how it sounds...

Regards,
Gordon.

Guido
09-25-2003, 11:54 PM
Originally posted by Giskard
Ok Earl, thanks. :)

"Hopefully someone with modelling software can figure this out."

Well, actually my electroacoustic model of the 2012H is coming up short.

Giskard, any progress with your model of the 2012 and modification suggestions for the 4343 network?
I'm ready to try it on my stock pair of 3143.

Thanks

4313B
09-26-2003, 04:44 AM
Originally posted by Guido
Giskard, any progress with your model of the 2012 and modification suggestions for the 4343 network?
I'm ready to try it on my stock pair of 3143.

Thanks
Actually, I haven't fiddled with it further. Sorry :(

In your case I don't think it would be wildly helpful anyway since you're operating in such a limited bandwidth. You pretty much have a constant impedance in the range you're using it in.

Did you try the notch filter?
Have you tried what Earl and Gordon suggested?
Try both of those suggestions and let us know?

Variac
10-05-2003, 12:17 PM
Second question for the JBL TECHBOT: Do you have the part number for the ME150H recone kit? My JBL service center doesn't have it in his consumer listings ( I assume due to the overseas use only ) and unfortunately we cannot call carla at JBL anymore...

Hello, I am a new member here, but a regular at DIY Audio.
I just bought a pair of New Old Stock JBL's so I guess I am in this club too.

It was suggested that I could find out more about my NOS
JBL ME 150H woofers in this forum. They are mentioned in this thread so I'm hoping for the best! I would like to know what model speakers they were in, what years?, specs, any good? Overseas only- what countries?etc.

Thanks
Mark

Guido
10-08-2003, 04:28 PM
Originally posted by Giskard
Did you try the notch filter?
Have you tried what Earl and Gordon suggested?
Try both of those suggestions and let us know?

I tried the notch and it just didn't sound right. I could not explain but the sound was bad.

I tried the 2,5mH Inductor and there was even more mids:confused:
Please somebody explain me that:confused:
Every crossover program prognose the mids to decrease and then they increase......

Finally I tried the 22 uF in parallel to the 20 uF.
A Wonder:confused:
The whole sound of the 4343 changed. It's much more soft now. I still A/B the one with additional cap to the one without and can't believe.

Thanks Earl for this. And please try to explain this to me.

The additional cap really is the ticket to implement the 2012H in the 4343.

:cheers:

4313B
10-08-2003, 05:03 PM
Excellent! :cheers:

Nice R & D Guido! :)

Earl K
10-08-2003, 05:38 PM
Hi Guido

Glad it worked out. :yes: I still think the circuit needs more tweaking - but if you "don't think its broke then don't attempt to fix it".


Thanks Earl for this. And please try to explain this to me.

The idea is directly from JBLs own implemention of massaging/handling rising midband response on their deep-gapped speakers ( like your 2012, the ME150H, the 1500al, etc. ). Though the extra value in the cap "upsets" the classic LC ratios and their stability quotients - those rules seem to be able to be bent that much easier when dealing with transducers that are inherently better damped / or have that extra percentage of motional control from the motor topology . :blah: :blah:

I'm sure most software packages just can't account for this. The wizards at JBL designing these circuits know better than the standard text-books.

regards <. Earl K :)

Earl K
10-09-2003, 07:48 AM
Hi Guido


I tried the 2,5mH Inductor and there was even more mids
Please somebody explain me that

The replacement of the original 1.7mh inductor with the 2.5mh inductor should have knocked down that 1K peak as GordonW suggested - if - they had similar DCR values.

So, what are the DC resistance values for these two chokes ?

I suspect your replacement was a couple of ohms lower.

If so, that will change a lot of things in this finicky circuit. For instance the preceeding high pass section in this MF band will be working with (seeing) the wrong impedance. This actually creates a new high-pass point around 200hz instead of the original 350hz ( based on the motional impedance figures I have from my mockup circuit ). With that 2012, you should hear that change if you are not biamping. I forget if you are.

Anyways, that's the best explanation I can offer without a 2122h and the original circuit in front of me.

regards <> Earl K :)

Guido
10-09-2003, 11:16 AM
Originally posted by Earl K
Hi Guido
The replacement of the original 1.7mh inductor with the 2.5mh inductor should have knocked down that 1K peak as GordonW suggested - if - they had similar DCR values.
So, what are the DC resistance values for these two chokes ?


Mhmm:hmm:

My inductor have 0,3 Ohm and the original have 0,6 Ohm. Should this be the reason?

Earl K
10-09-2003, 12:13 PM
Hi Guido

The difference in the DCRs' would need to be greater than the .3 ohms you just quoted. Now, 2 ohms would be a significant change .

So differing DCRs for that part substitution isn't reason .

regards <> Earl K :)

Ian Mackenzie
12-12-2004, 07:36 AM
I am planning a new diy version of the 3143 JBL for my brothers 4343 crossover using 8 ohm L Pads for the HF and UHF with fixed R1/R2 pads (not T section) . In order to get the most gain from bi amping I was planning to omit the midrange T section and its Pad.

Can anyone make any suggestions if the LC values will need adjustment?

Ian

Earl K
12-12-2004, 08:47 AM
Hi Ian,


Can anyone make any suggestions if the LC values will need adjustment?

- Which LC values are you referring to ?

- Just the MF (midrange) leg of the crossover ?

- Or all of the legs ?

- I built up a portion of the (3143) MF last year and measured ( no documentation was done ) the AC impedances in various portions of the leg. The "T" pads do go a long way in "stabilizing" the working circuit impedances that the preceeding LC components will see ( even when those whacky 16 ohm Lpad are adjusted up or down ). These "TPads" help provide a meaningful foundation from which to calculate the necessary LC values - again, when using 16 ohm variable Lpads.

I think you ought to explore "why" 16 ohm Lpads were used in the first place with these transducers . Even a bit of conjecture in this area can be useful . As in; perhaps they provided better "damping" for the existing transducers .

- Moving to 8 ohm variable Lpads ( might ) need to be accompanied by a relocation of the conjugate inductors ( in the MF and HF sections) . You can look to the 4344mkII and 4348 tech sheets for inspiration in this area ( of inductor - relocation ). I use inductors in this position with my horn drivers - I feel they provide better "damping" in that position ( ie , after the resistors in the circuit ) .


regards <. Earl K

PS ; so I guess my answer is ; yes , some ( if not most ) LC values should be recalculated .

4313B
12-12-2004, 09:27 AM
"I think you ought to explore "why" 16 ohm Lpads were used in the first place with these transducers ."

The 16 ohm L-Pads in the early 43xx monitors were used for power handling. Reference was usually at 12 o'clock so set the 16 ohm L-Pad there and measure the two legs. Use those values to rework your attenuation. To get it real close include the impedance loads of the drivers.

Ian Mackenzie
12-12-2004, 01:42 PM
Thanks for that. I suppose I need to build the real networks and work it out from there.

I'll let you know what happens.


Ian

ralphs99
12-12-2004, 03:45 PM
At least part of the reason of the rising response above 800Hz is due to the directivity index (DI) increase with increasing frequency. Most drivers are designed to produce flat power response which means a direct response that rises with frequency. The obvious exception are horn loaded transducers that feature constant directivity.

In order to model the driver in an analog simulator some account needs to taken of this effect, assuming the aim is to produce a flat direct amplitude response. But that depends upon the listening environment. If the room is very dead and the listening position is relatively close to the speakers, ie a near field type listening environment, the direct sound dominates in the midband and a flat direct amplitude response should be the target. If the room is quite live and the listening distance more than a few of meters from the speakers, the listening environment for the midband will be in the diffuse field, and the power response of the speakers comes more into play. I suspect that for most typical home environments something between the two will be most suitable. I have to stress that this effect is frequency dependant. The critical distance (ie the change from near field to far field) increases with decreasing frequency.

Guido: This may explain why the notch filters you have been trying are not sounding good to you. Notch filters are also problematic for the phase reponse. I suggest a simpler way around your problem may be to increase the toe-in of your speakers so that you are no longer directly on axis. 10-15 degrees should be enough. This solution works well for 4430's with constant directivity horns. For 43xx series monitors, the changing DI vs frequency of the exponential horns will negate the advantages of the extra toe-in to some degree ( HF loss). But it's worth a try as it's such a simple experiment.

Cheers, Ralph

Ian Mackenzie
12-18-2004, 09:53 AM
I think I will build the 3145 network and be damned, I figure the only change will be the mid range LC values.


Ian

Ian Mackenzie
11-22-2006, 10:22 PM
Heather,

Perhaps this thread may prove useful to you. There will be some degree of tweaking required . Regards all this humpty do, I measured the real gain of the mid filter passband quite sometime ago. The difference in spl of the mid cone driver was about 1 db between the biamp and full passive mode. That can be levelled with the L pads if you wish without stessing out over voltage drives too much. More important is balancing the driver outputs to blend and your taste. I find +- 1/3 db audible with four drivers.

There is so much play in those pads I wonder if they are a virtue or a sin. Regardless you will need to carefully balance all four drivers so they work as one!

Giskard is also discussing filters in another thead, an educational and insightful discussion for some and no doubt incomprehensible for others.


Ian

4313B
11-23-2006, 10:12 AM
Giskard is also discussing filters in another thead, an educational and insightful discussion for some and no doubt incomprehensible for others.http://www.audioheritage.org/vbulletin/showthread.php?t=13043

Ian - I deleted all my posts and will consider addressing your concerns in full in a new thread.

hjames
11-23-2006, 11:07 AM
Thank you very much - I hadn't seen this thread before!
Even with the search engine there is so much that just doesn't show on this site! I often email myself bookmarks of useful threads when I find them - or when you heavy-hitters point them out to us! Again, much thanks!

I took a few glances at it and will definately read it in more detail over the weekend. Its Thanksgiving Day stateside and we've fixed a small feast to take to my dad (he's 84) about an hour away in Maryland. The family doesn't get together much like when we were younger, but if it makes him laugh and smile, I'm all for it.

I've plans to pull my stereo gear down off the media room shelving - I'll move the media shelves around and assemble the electronics in a rolling teak rack I used to use. Sad to say I did like the look of the beechwood shelf system (IKEA), but its just not conducive to the kind of periodic dinking I'm prone to do ... (not to be confused with the single-malt drinking I'm also prone to do).

Anyway - I've got to get the monitors down from "on high" and probably build some small platforms to get the slots at ear level. Once thats all arranged I'll take more pictures to post in another thread later.

Too much to do, but gotta run - have a great day! Thanks to everyone!

-= )-(eather =-


Heather,

Perhaps this thread may prove useful to you. There will be some degree of tweaking required . Regards all this humpty do, I measured the real gain of the mid filter passband quite sometime ago. The difference in spl of the mid cone driver was about 1 db between the biamp and full passive mode. That can be levelled with the L pads if you wish without stessing out over voltage drives too much. More important is balancing the driver outputs to blend and your taste. I find +- 1/3 db audible with four drivers.

There is so much play in those pads I wonder if they are a virtue or a sin. Regardless you will need to carefully balance all four drivers so they work as one!

Giskard is also discussing filters in another thead, an educational and insightful discussion for some and no doubt incomprehensible for others.


Ian

boputnam
11-23-2006, 01:29 PM
... no doubt incomprehensible for others. That's the best part about this forum - contributions range from from reveling in joy of finding an old pair of JBL's to incredibly insightful engineering pursuits.

I was rivited by the thread you refer to - I found myself reading and re-reading it. While exhibiting a high level of understanding, all the posts in that thread were incredibly legible and supported by graphics. While not contributing to the thread pesonally, I found much that matched observations of my own, which I didn't understand the reason(s) for. That said, the discussion of the change in the voltage drive of the 2122 when going from passive to biamp has caused me to go take additional measurements out of curiosity.

You can't match the depth of this place.

Ian Mackenzie
11-23-2006, 01:48 PM
We must remember most members are each at a different stage of understanding hence my remark. But we can all grow by watching and if you wish participating.

Yes its all a lot of fun and you will serve yourself well by doing some logical hands on stuff. But remember to use your ears, what you see is not always what you get with this stuff, even drivers have their own personalities!

boputnam
11-24-2006, 08:49 AM
...most members are each at a different stage of understanding...Uh, yeah - each member IS at a different stage in everything. I don't understand the point of your prior post, or of this one - they are each redundant.

Ian Mackenzie
11-24-2006, 12:48 PM
Uh, yeah - each member IS at a different stage in everything. I don't understand the point of your prior post, or of this one - they are each redundant.

Oh, The point is you learn by doing and by all means model and measure it but try and listen it at each stage of development, science ain't the whole story with audio!

All redundant now:)

Ian

4313B
11-24-2006, 01:28 PM
Oh, The point is you learn by doing and by all means model and measure it but try and listen it at each stage of development, science ain't the whole story with audio!

All redundant now:)

IanIt is redundant. We've gone over it time and again since this forum started.

Here's a thought, and I'm just tossing it out here for consideration. How about we deal with the topic of this thread - 2123H vs 2122H in a 4343 monitor. Let's start over?

Anyone have the experience of using the 2123 instead of the 2122 in the 4343 monitors?? Aside from the obvious efficiency difference any suggested changes to the network? sub...:0)The 4343 used the 2121. The 4344 and 4345 used the 2122. Which system are we discussing?

I'll start off with one of my favorite lines from JBL - "Won't work." Very common answer. Let's discover why? Or if it's even a reasonable answer. There, I've thrown down the gauntlet. You guys figure it out.

4313B
11-24-2006, 01:29 PM
As soon as I can I am going to lay my hands on a pair of these 2123H's and give them a go.Ok, that's a good start. Which system will you be trying them in?

Ian Mackenzie
11-24-2006, 01:46 PM
I can see your point and I agree, that is why when I did a search I found this thread with some useful stuff. There are other threads too, it needs to be put somewhere where those who need it can find it!!

Here's a thought, and I'm just tossing it out here for consideration. How about we deal with the topic of this thread - a 2123H in place of a 2122H in a 4343 monitor. Let's start over


I think this would be the most useful for the majority.

Ian

Ian Mackenzie
11-24-2006, 01:48 PM
Ok, that's a good start. Which system will you be trying them in?

In may case initially the 4345 (with some mods) but ultimately a 4344mk11 clone.

In any case as this is a technical forum I suppose any mention of non standard drivers in a JBL design makes it DIY subject matter and that is probably where this thread should be.

Ian

Zilch
11-24-2006, 01:54 PM
Until last week I did nothing. The result was good but not perfect.:p

4313B
11-24-2006, 01:57 PM
:pThanks Zilch! That's splendid!

Guido
11-24-2006, 05:47 PM
It was as it was :o:

Tom Loizeaux
11-24-2006, 07:59 PM
If we are talking 4343s, I believe the foam-surround 2121 is the driver to use because it reaches down best to meet the woofer. As I recall the 2122 and 2123 don't go down quite as low.
Is this correct?

Tom

4313B
11-24-2006, 08:30 PM
If we are talking 4343s, I believe the foam-surround 2121 is the driver to use because it reaches down best to meet the woofer. As I recall the 2122 and 2123 don't go down quite as low.
Is this correct?

TomThanks Tom.

From http://www.audioheritage.org/vbulletin/showpost.php?p=135258

The 4343 used the 2121. The 4344 and 4345 used the 2122. Which system are we discussing?From some of my ancient posts - I'll leave it to others to run the curves to see which goes deepest.

The published xmax on these drivers:

.060"
.120"
.100".

All three have a 0.280" top plate.
All three currently have a moving mass of roughly 26 grams.

The 2121 has a voice coil winding depth of 0.280"

The 2122 has a voice coil winding depth of 0.180"

The 2123 has a voice coil winding depth of 0.420"

They are not interchangeable... Yeah, that's what I said then and I was paraphrasing a JBL engineer so let's see if it's true. You guys try them and report your findings.