2452H-SL in a 2-way

[Robh3606]

Here's a first crack at it. I was messing with it last night. Loaded the impedance file this morning. That's driver file #5. Basically I am driving this. I have tried using the Optimizer on compensations and gotten some really odd outcomes. I use Greg's basic filter and go from there. OK if you want crossover at 1.5K not going to work at 1K. I was hoping there would be a bit more loading before the crash. I may be able to get it to work @ 1K but the attenuation would be a problem.

The red curve is 24db L/R at 1.5K

Can you post the raw ungated MLS??

Rob

[Robh3606]

Here's a second shot that is OK out to 1K but there is no real network to roll off the driver just compensation. I could really use either a sine sweep of the ungated MLS. Will try the other curves later.

Rob

[4313B]

I may be able to get it to work @ 1K but the attenuation would be a problem.

Probably :dont-know

[Robh3606]

Hello JBL4313B

I don't know what the 1 meter SPL is. I am using the Quide Curve for the driver. So the attenuation isn't that bad yet figure about 15db @ the peak so maybe??? What surprises me is the roll off. I have a 12db passive on top of the horns roll off to get the 24db slope at 1.5K on the first plot.

With the second one I don't think I can get it to work real well @ 1K with a proper crossover in place??

Any ideas??

Rob

[4313B]

I don't know what the 1 meter SPL is.

It's really loud.

So the attenuation isn't that bad yet figure about 15db @ the peak so maybe???

Yeah, I think there's enough there.

Any ideas??

Just what I posted above. I'd have to actually build it and try it. It probably needs an inductor to ground to pull that leg around 500 Hz down. Since the driver/horn is dropping at 12 dB/octave you should only need a 12 dB/octave electrical filter. I used a 6 dB/octave above. As you can see it is 3 dB down at 1 kHz. I have no idea how it would actually sound since it naturally wants to start attenuating around 1.5 kHz. It might sound strained. But who cares, JBL's done the same thing with some of the smaller Consumer horns to get them down into the 700 to 900 Hz range and those are $18,000 loudspeakers that no one is complaining about. I'm anxious to hear what Bo thinks about the VP7212MDP.

*****

Well bloody hell! I didn't save off the schematic properly so I could post it for you. I really hate the way LEAP does the whole file save thing.

[Robh3606]

Well we must have been thinking the same thing here it is with a big cap and an adjustment to the "trim" inductor. It rolls off below 500Hz. Yeah I agree the save sucks and you can't really undo. So I have a single pole instead of 2 pole.

Rob

[boputnam]

...As you can see it is 3 dB down at 1 kHz. I have no idea how it would actually sound since it naturally wants to start attenuating around 1.5 kHz. It might sound strained.

Do we know the crossover point JBLPro uses in the VP7212MDP? I've looked and can't see that you guys have discussed that. Granted, that is a 2-way with an incredible 12-in woofer, but some of the smartest guys I know are doing 12-in 2-ways... Maybe JBL take the 2452H-SL up to 1.5kHz...?

...I'm anxious to hear what Bo thinks about the VP7212MDP.

Yo tambien. I have uniformly positive reports from a universally tough crowd. I will report soon as I can.

[Earl K]

Some nice looking curves there guys ! Bravo !

I have no idea how it would actually sound since it naturally wants to start attenuating around 1.5 kHz. It might sound strained.

,,,here it is with a big cap and an adjustment to the "trim" inductor. It rolls off below 500Hz.

- I do something similar in that I use a "big cap / small inductor to give a higher "Q" curve " to buttress up the drive voltage of my impossibly small horn setup . It has worked well for HiFi purposes .
- It's not something I'd practice in my SR work .

- This technique seems to be easier to successfully implement ( sonically ) when the driver has a lowish Fs ( which is why I was interested in the PWT pic for the 2452 ).
- The Altec 288-8K ( which I use ) has a pretty low Fs ( lower than 500 hz ) .
- I'd think that forcing EQ ( LF, near cutoff ) onto the 2431 in a likewise fashion ( when it's fixed onto a overly tiny horn with no loading ) would dictate the use of some other form of damping filter ( such as a series LCR ) to stop audible weirdness at 900 hz.

[Robh3606]

Hello Bo

As far as I know it's an active system. I will see if there is anything on the spec sheet. With DSP they can do whatever they need.

Here's a schematic for the graphs posted. They are not converted to standard values and the attenuation is unknown at this point so they are for reference only. Gregs filter is a real champ!!

Rob

[boputnam]

...As far as I know it's an active system. I will see if there is anything on the spec sheet. With DSP they can do whatever they need....

Yes indeed, it is active, and there is an onboard DSP.

But the spec sheet gives few details on the engineering... I cannot find anything on the JBLPro site about the 2452H-SL and recommended crossover points.

However, there are two ways to skin this cat.

The VP7212MDP uses the 2262FF woofer, a not-too-distant brethren of the 2262H. The 2262H is very linear to ~1.2kHz (cf. Figure 5).

The 2262H is used in the SRX712M, a passive/biamp wedge I know very well. The recommended crossover point for bi-amping is 1.2kHz. Grist for the mill...

[Zilch]

Note: All FRs done with 47 uF protection capacitor.

[Zilch]

But the spec sheet gives few details on the engineering... I cannot find anything on the JBLPro site about the 2452H-SL and recommended crossover points.

Look for my FR curves in theirs. I see it rolling off at 1.5 kHz.

Also see the DI curve. The slope changes to flat at 1.5 kHz, where the waveguide takes control, looks like....

[Zilch]

O.K., got close, unit #8, 9 dB of comp:

2 uF || 8 Ohms, then two series notches:

1.5 mH, 5.6 uF, 5 Ohms, and
0.13 mH, 0.47 uF, 4 Ohms.

Can LEAP refine and optimize this topology?

[4313B]

1.5 mH, 5.6 uF, 5 Ohms -> 1.5 mH, 6.6 uF, 6 ohms (1.6 kHz notch)

0.13 mH, 0.47 uF, 4 Ohms -> remove

You might want to try something like a 2.0 mH, 2.2 uF, 20 ohm or 3.0 mH, 1.5 uF, 20 ohm as well. (2.4 kHz notch)

Your two big problems are at ~ 1.6 k and ~ 2.4 k and the dip at ~ 3 k is a real bummer.

Maybe Rob has a bit more time and other ideas to try.

[boputnam]

Look for my FR curves in theirs. I see it rolling off at 1.5 kHz.

Also see the DI curve. The slope changes to flat at 1.5 kHz, where the waveguide takes control, looks like....

Dunno if you're "seeing" it right.

In the SRX712M, JBL takes that 12-in 2262H up to only 1.2kHz. That same woofer is mated to the 2452H-SL in the newer VP7212MDP. I'd guess that cabinet crosses at the same point.

As well, regarding a 15-in 2-way, the VP-series uses the 2265H mated to the 2452H. While JBL again don't disclose the crossover for the VP-series, the VRX-series uses that same woofer, the 2265H and again, the crossover point is 1.2kHz.

I think you might find that you need to run the 2452H-SL down to 1.2kHz to get a good crossover to the woofer - otherwise you are running the woofer up too high. JMO...

Your two big problems are at ~ 1.6 k and ~ 2.4 k and the dip at ~ 3 k is a real bummer...

Yup. I particularly don't like that dip at 3k "coming out of" the hump at ~2.4k. Once you treat the ~2.4k anomaly, the one at 3k might worsen...