Think We May Have a Keeper Here!!!

[edgewound]

While you're in there, try putting a horn on it and running up the ~500 eq bands for a flat response and see if that doesn't clear up male vocal intelligibility.

People been putting 2235's in L200 cabinets for ??? years and I'm the first to notice this 500 Hz suck-out phenonom???

L200's originally had an LE85 and LX16 at 1200hz

[toddalin]

Characteristic of the woofer??? If you go back to the thread where I compared the 2235 to the W15GTI in my center cabinet, you see the same phenonom but shifted up a little. While the 2235 was through the N1200 low pass during the test, the effect of the filter should have neen minimal at the frequencies we're dealing with here (as evidenced by the response above 900 Hz).


Frequency Response
1500 84.5
1450 78.9
1400 87.9
1300 89.2
1200 90.5
1100 94.2
1000 101.4
950 101.8
900 101.9
850 99.0
800 98.3
750 98.7
700 96.6
650 98.2
600 99.1
550 100.8
500 100.1
450 99.3
400 99.6
350 98.9
300 99.8
250 100.0
200 100.0
180 100.0
160 100.5
140 100.3
120 101.4
100 100.7
90 101.8
80 101.5
70 101.6
60 100.9
50 99.5
45 96.9
40 90.4
35 89.7
30 89.6
25 90.4
20 89.3

[edgewound]

I'll stay out of it...you're in good hands. My point is that there will be somewhat of a summation between the LF and MF drivers system response as the two drivers fill in the crossover area. the L200 and L300 both had BIGGER drivers (LE85)that are better able to fill-in at that octave that's giving you pains. Hence that 500Hz suck out....but maybe I'm peeing into the wind.

[toddalin]

Egads! Don't post that stuff. Zip it in a text file or make a graph!

Is Todd using my 2235H's or did he recone some other cores?

I know what you are alluding to edgewound. I think Zilch is running this measurement with just the 2235H and the box, nothing else.

2205Cs remagnetized and reconed as 2235s by OCS last December 2005.

[Zilch]

Ran 1000 points. Yup, it's one of your 2235H's. Todd's are recent recones, I think. He'll tell us.

Flat from 433 to 490 with a blip at 470
Hump at 808, then flat from 860 to 960

Shall I add more insulation to the box?

Edge: These are L200B-based crossovers, 800 Hz. Load was 136A (2231) and LE85 on the shorter horn.

[Zilch]

Pull the mic back and run another RTA.

How far? 1M?

[Zilch]

Reconfiguring for RTA....

Sorry. Gotta reboot. WT2 messes with the camera USB connection....

[toddalin]

Run another RTA with the mic further back.

I just don't believe you guys should be getting these depressions with these drivers.

I guess I'd put the networks back in and pull the conjugates off the 2235H's, see if that adds a bit in the 500 Hz to 1 kHz range.

Thought you were the one who asked me what I was going to do between 500-1k Hz? Sounded like you expected it all along.

[Zilch]

Sounds spooky. What was it configured for?

WT2. I moved everything to get the shortest possible WT2 connection without having to haul the L200 up 3 steps with no handtruck.

It's apparent why I never saw it before. I'd have just ignored the little notch at 900 Hz, though I believe it HAS irritated me in the past. It's nearfield measurements that show the 500 Hz notch here....


1 M RTA:

[Zilch]

Todd's sending me one of the networks to test, and I can try whatever you suggest after verifying the voltage drive. I don't have a problem with that RTA response, but it's Todd's problem I'd like to help solve. Clearly, there's something going on in the 4" nearfield, which he can hear and I measure as well.

I'll probably beef up the damping inside the box in the meantime and see if that helps. Another 6" on the rear, or 4" all around.

Todd: Your RTA - where are you measuring from? Did you get a boom and stand for your mic? I mean, it's not the pillow on the couch thing still, is it?

Let's get on the same page. Take the 16 Ohms out from the LF (it's just WRONG, trust me,) and dial down the MF to achieve the best balance. AutoEQ from there.

Perhaps Giskard can discuss the implications of the 1.0 uF you added to the HF, which I believe makes it an 18 dB crossover, and the change you made to the HF inductor as compromise between N7000 and 8000.

I'm off to dinner, as well. We'll reconvene later....

[Zilch]

Thank you, Giskard. Yes, those are the values.

[Guess I'd be removing that 1.0 uF, first. ]

Yes, it looks like tuning or removing the Zobel will help considerably....

[toddalin]

Todd's sending me one of the networks to test, and I can try whatever you suggest after verifying the voltage drive. I don't have a problem with that RTA response, but it's Todd's problem I'd like to help solve. Clearly, there's something going on in the 4" nearfield, which he can hear and I measure as well.

Todd: Your RTA - where are you measuring from? Did you get a boom and stand for your mic? I mean, it's not the pillow on the couch thing still, is it?

Let's get on the same page. Take the 16 Ohms out from the LF (it's just WRONG, trust me,) and dial down the MF to achieve the best balance. AutoEQ from there.

Perhaps Giskard can discuss the implications of the 1.0 uF you added to the HF, which I believe makes it an 18 dB crossover, and the change you made to the HF inductor as compromise between N7000 and 8000.

I'm off to dinner, as well. We'll reconvene later....

Mic is on a tripod with legs collapsed such that the mic is just about/under horn level. I tried both 1 and 2 meters as well as putting the stand on the couch where I sit, all to the same conclusion with only minor variation.

The 16 ohms of resistance is not in the system. In reality, the added 1 mfd cap that is after the choke in the HF section is directly on the tweeter as opposed to before the L-pad. Once I determine if it stays or goes, I will remount it before the L-pad.

The 1.0 mfd cap was not in the original configuration and is not shown on the N7000/N8000 diagrams. However, the N7000/N8000 are meant to be used downstream from a 2-way unit and that would put additional caps in the tweeter signal path.

Note that the typical JBL 3-way network uses both of these caps, albiet they put the 1.0 mfd before the choke and the 1.5 mfd after the choke. Mine are vise versa.

In one configuration, I had the L-pad on the woofer connected as a simple reostat variable from about 18 to 0 ohms. In this configuration, the L-pad serves as a "contour" control and allows me to flatten the 500 Hz band. By dialing it to 0, it is out of the system and everything is normal (with the dip).

[toddalin]

With or without the networks in place?I'm thoroughly familiar with the stock JBL networks. I even have schematics for systems that haven't been released yet. You really need a modeling program so you can see what all this is doing. At the very least you need to rig up a voltage drive measurement system if you don't want to bother with a spice backage and the time required to learn to use it. What I've been attempting to convey all along is that this is completely unnecessary. Nobody puts a variable resistor in line with a 2235H unless they are just screwing around to see what happens.

Network was in place for all testing.

L-pad (variable resistor) is out of system completely and was, just as you said, for test purposes.

On yout graph, which line represents what?

[toddalin]

Please excuse my ignorance... and the yellow and green?

As previously noted, the addition of the 1 mfd cap is possible, but based on the N7000/N8000 was not in my original design (that's why it is currently hung direcly on the tweeter as opposed to pre-L-pad where it would ultimately take up residence). Ultimately, if it stays, I can reorder them if that proves beneficial.

The cyan represents your reversal of the caps.

[toddalin]

OK, now you're confusing me... my arrangement is set up as 1.5 mF S/0.5 mH P/1.0 mF S so is the yellow line?

From post #57

1.5 uF S, 0.5 mH P, 1.0 uF S = yellow
1.5 uF S, 0.5 mH P = green

Post #63

1.0 uF S, 0.5 mH P, 1.5 uF S = cyan