Yet another 4425 DIY

[jerv]

I see two problems, both of which you've already recognized:
1) You need more HF attenuation to balance with the 2214.
2) The slope of the compensation provided by the 2.2 uF is a bit too steep.

I found them a little too bright also. I ended up with a switch on the back that lets me change between 0, 3.5 and 6 db down on the upper end. I couldn't find the exact resistor values without opening them up, but normally use them on the -3.5db level.

Thanks for the suggestions. I will try some more simulations tonight, and keep you posted!

[jerv]

This is the simulation with L1=3.0 mH and C1=20 uF (as with the original L200t3 crossover). This increases the level 200-1000 Hz by 2-3 dB, while maintaining good phase coherence (in fact: it's even better).

But I find it almost impossible to use only L-pads to balance the 2416. Any L-pad - front or back end - or series resistance also changes frequency response and HF attenuation quite a lot.

The 2.2 uF and/or the inductor has to change as well.

[jerv]

This is the best simulation I came up with yesterday - with (basically) the same filter topology. Further developments will (I think) change filter topology more drasticially.

L1 reduced even furter to 2.2 mH and C1=22 uF. This increases the level 200-1000 Hz even more.

In the HF section the 2.2 uF is parallelled with 16 ohm. Then, to compensate for the crossover rolloff at 1200 Hz the inductor has to be reduced all the way down to 0,27 mH / 0,3 ohm. R3 is now 8 ohm.

All is now within 5 dB 100Hz-20kHz, buth phase coherency has suffered somewhat. I will build this network, measure it to see if it corresponds to the simulations and then compare it sonicially with the L200t3.

[Dougie]

Hi Jerv;

I decided to do an impedance / phase measurement on my 2214H drivers anyway as I've had them here in boxes for a couple of years and have been wanting to do something with them ( or sell them ) LOL!!!

The first plot is for the first driver (a) Fs is 29.474 Hz and reached a max Z of 49.989 ohms at resonance. The Fs is a bit higher than JBL's specs of 23 Hz, but my drivers are not broken in yet and may account for the higher Fs !!

Dougie

[Dougie]

I measured the second 2214H just out of curiousity. Fs measured out at 28.274 Hz and the max inpedance reached was 46.637 ohms, a bit lower than the first driver.

I overlaid the 2 measured curves to show you the comparison. See attached pdf file......

Dougie

[Dougie]

Jerv;

The color differences in the overlaid plots didn't come out all that well on the pdf's posted here, seems to have lost something in transit.

You can PM me with your email address and I would be glad to send you both pdf's that way. The plot lines are much wider and the color differences in the two plots are of much better quality in the origonals.

Let me know;

Dougie

[jerv]

Thanks for sharing your results, Dougie!

Your impedance plots looks basically the same as mine - accounting for that I measured mine in 4425 cabinets and you measured your (as I understand) in free-air.

Very nice to have results verified by some other's measurements.

From 200 Hz up the curves look very similar - including the small anomaly at 1,9 kHz (which corresponds with the annoying peak in the frequency response).

BTW: What measurement gear and SW do you use?


Espen

[jerv]

I made up new a new filter as described some posts ago.
For the LF the components are: L1 = 2,2 mH 0,2 ohm DCR, C1 = 22 uF, R1 = 47 OHM, no R2.
For the HF, the components are: C3 = 2,13 uF, L2 = 0,27 mH 0,31 ohm DCR, R3 = 8,2 ohm.

Here are the simulation for the filter (top) and the measured result (bottom). Almost, but not quite similar. The HF is about 2 dB up compared to the simulation. The HF is easily damped by taking R3 down to 4-5 ohm, but anyway, I have to investigate this.

Meanwhile, I listen to music and compare them sonically.

[Dougie]

Thanks for sharing your results, Dougie!

Your impedance plots looks basically the same as mine - accounting for that I measured mine in 4425 cabinets and you measured your (as I understand) in free-air.

Very nice to have results verified by some other's measurements.

From 200 Hz up the curves look very similar - including the small anomaly at 1,9 kHz (which corresponds with the annoying peak in the frequency response).

BTW: What measurement gear and SW do you use?


Espen

I use LMS from LinearX Systems.........

http://linearx.com/

Dougie

[Dougie]

Jerv;

I don't see an anomaly at 9 Khz in my impedance plot Dosent matter as the 2214H wont be used way up there anyway.

The small " hump " in my plot around the 2 Khz area is the result of my measurement system pausing and switching decades, then continuing on...

The roughness between 1 and 2 Khz is the result of some cone breakup in the midrange region.

Dougie

[jerv]

Jerv;

I don't see an anomaly at 9 Khz in my impedance plot Dosent matter as the 2214H wont be used way up there anyway.

The small " hump " in my plot around the 2 Khz area is the result of my measurement system pausing and switching decades, then continuing on...

The roughness between 1 and 2 Khz is the result of some cone breakup in the midrange region.

Dougie

I meant 1.9 kHz. (In my country, the "," is used as the decimal delimiter - not the "." I forgot. ).

My thought was that the impedance anomaly at 1.9 kHz was caused by cone breakup in that region. The 1.9 kHz resonance is quite pronounced.

Espen

[jerv]

After much experimentation I have ended up with 3 filters to compare sonically. Filter A is based on the L200t topology, but with different component values. L1=3.0 mH/ 0,2 ohm, C1=15,6 uF, R1=47 ohm.
C3=2,2 uF, L2=1mH / 7,5 ohm, R3=8 ohm.
Filter slopes approximate 4th order. The revese null is deep. Sound is very good and lively - but somewhat bright. Measurements confirm this. The curves are roughly the same as my sumulations some posts ago, with the HF 2-3 dB more down.

Snapshot here:

[jerv]

..has a somewhat different topology, with a more traditional 4th order layout in the HF section to attenuate the 2416 without messing up the filter slope. Slopes are still 4th order, reverse null is deeper and narrower and phase traching better.
In the LF section L1=3.0 mH / 0.2 ohm, C1=15,7 uF
In the HF section C1=8,2 uF, L1= 3.3mH / 0.25 ohm, R1=16 ohm, C2=2.7 uF, L2=0,2 mH / 1.66 ohm and R2=4,7 ohm. Sound is pleasant and warm - a little subdued compared to filter A.

Schematics and measurements:

[jerv]

The last one is an 8th order slope experment. This was the only way I could get rid of the 1.9 kHz 2214 peak. This filter measures the best. Reverse null and phase tracking is very good. I haven't listened to it much yet.

Schematics and measurements and pict of filter A and B:

[Zilch]

RLC 1031 is a notch filter, no?

Looks like you've still got the 1.9 kHz peak, tho.

Or am I not quite understanding yet?

I think I'd have gone after the peak with a series notch filter to common....