Troubles with EQ parameters - JL Tun Software

[flyboyusa]

I'm having a problem transferring the auto-generated PEQ settings.

I run an initial sweep and get my target aligned at 72 dB and run the auto generate pictured here....

REW does it's thing well and predicts a spectrum that will match the target well at my chosen SPL of 72 dB (Using the Twk-88 EQ preset).

When I then transfer those PEQ band settings into my JL Tun 3 software and then re-run the sweep, my overall level has dropped considerably.
Here's what it's ending up with....

Here's what the EQ looks like in TuN

The PEQ parameters don't transfer well into the JL Tun software....they sum up to much too large cuts than predicted in REW. It's almost like the synergistic additive effect of each filter isn't being taken into account in REW and when Tun stacks them on top of each other, the signals are being over attenuated because of the additive effect.

Anyone seen this before?

 

[Wayne A. Pflughaupt]

There are several problems here.

For starters, a big issue probably is that REW doesn’t have a specific setting for JL Tune.

Different equalizers calculate filter bandwidths differently. This is why REW has settings for specific equalizers.

What’s likely happening is that the program’s bandwidth calculations are wider than what the REW setting is doing.

Another part of the problem is that you’re over-equalizing. Look at Filters 2-3 and 9-10 for instance – they are so close together they can’t help but overlap. Most subs don’t need more than 3-4 filters tops. All you need to do is eliminate the worst peaks and depressions. Look up my article at Home Theater Shack on minimal EQ.

Lastly, the Target should be roughly half-way between the worst peaks and depressions. Putting it as low as you did requires deeper filters. Filters “spread” wider the deeper they are boosted or cut, which makes them more prone to overlap adjacent filters.

Regards,
Wayne

 

[John Mulcahy]

The PEQ parameters don't transfer well into the JL Tun software....they sum up to much too large cuts than predicted in REW.

Response shown in TuN matches the response in REW when I try it, using the TwK-88 setting and TwK emulation in TuN. Perhaps post a screenshot of your TuN settings and response display and the REW filter settings window.

 

[dotnet]

I just like to chime in to say thank you for mentioning your minimal EQ article, As a total EQ noob I found it quite the eye-opener, because I’ve had the feeling that my overzealous EQ attempts fixed the graphs but killed the sound.

Another thing I’ve been wondering, should the overall gain of the EQ generally be dropped by the height of the highest gain filter, to preserve the headroom in the signal processing chain? I found that with certain high-gain filters (+12dB and more) I’m occasionally getting distortions.

 

[John Mulcahy]

with certain high-gain filters (+12dB and more) I’m occasionally getting distortions.

The maximum gain for the TwK-88 parametric filters is 6 dB, where are you applying 12 dB?

 

[flyboyusa]

Response shown in TuN matches the response in REW when I try it, using the TwK-88 setting and TwK emulation in TuN. Perhaps post a screenshot of your TuN settings and response display and the REW filter settings window.

Thanks John....I thought I had originally posted the TuN screenshot, but apparently not. I've updated the original post.
The cuts in some cases are maxing out at -18dB because of the stacking or additive effect....or maybe the Q bandwiths aren't the same as predicted on cuts....I tried last night to double any of the Q values for all of the cuts and that seemed to improve the fit quite a bit, but still not perfect.

 

[flyboyusa]

There are several problems here.

For starters, a big issue probably is that REW doesn’t have a specific setting for JL Tune.

Different equalizers calculate filter bandwidths differently. This is why REW has settings for specific equalizers.

What’s likely happening is that the program’s bandwidth calculations are wider than what the REW setting is doing.

Another part of the problem is that you’re over-equalizing. Look at Filters 2-3 and 9-10 for instance – they are so close together they can’t help but overlap. Most subs don’t need more than 3-4 filters tops. All you need to do is eliminate the worst peaks and depressions. Look up my article at Home Theater Shack on minimal EQ.

Lastly, the Target should be roughly half-way between the worst peaks and depressions. Putting it as low as you did requires deeper filters. Filters “spread” wider the deeper they are boosted or cut, which makes them more prone to overlap adjacent filters.

Regards,
Wayne

Thanks for the feedback. I'm using a JL Vxi amplifier/DSP that uses JL TuN software interface, it's the same TuN interface for the Twk, which does have a preset in REW, so I was using that, as I figured they must be the same since they are the same TuN software.
I totally agree...it seems as if the Twk preset in REW is suggesting Q values that are about twice as large of bandwitch as they need to be. I took all of the Q values and doubled them for the cuts only and that seemed to improved quite a bit.
As far as centering my target, I was aiming to have minimal or zero boosts, hence my target of 72 dB. But, I'll take a look at your article and try re-running the auto EQ with a more centered target.
Thanks for the input.

 

[John Mulcahy]

VXi and TwK-88 do not use the same Q definition for cuts, the TwK preset is for use with the TwK.

 

[flyboyusa]

VXi and TwK-88 do not use the same Q definition for cuts, the TwK preset is for use with the TwK.

Ahhh....that makes more sense then....thanks for the heads up.
Do you have any guidance for possibly using the TwK cuts or Generic cuts and modifying them manually to better ling up with VXi?

 

[dotnet]

The maximum gain for the TwK-88 parametric filters is 6 dB, where are you applying 12 dB?

No, sorry, I was speaking generally. I don’t even know the gain limits of the EQ I’m using (AU N-Band EQ).

 

[Wayne A. Pflughaupt]

I’ve had the feeling that my overzealous EQ attempts fixed the graphs but killed the sound.

That one deserves an award for "Quote of the Year!"

As far as centering my target, I was aiming to have minimal or zero boosts, hence my target of 72 dB.

But then your volume was so low you had to "boost" it 10-15 dab, didn't you? So it really didn't save you anything.

Regards,
Wayne

 

[flyboyusa]

Thanks for everyone's help and thanks especially to John Mulcahy for this amazing software and super complete documentation.
Based on the bandwidth functions listed in the help file, I deteremined that the rePhase EQ was a match to how the VXi Q values work.

Here's the initial sweep before any EQ and the suggested corrections....

After applying the suggested EQ filters and re-running the sweep....pretty dang impressive!

After EQing the whole system, here's the result (sub is muted here)....

Wow! I'm still in awe with how good this system sounds now! This has been a long project but well worth the efforts.
It's my 2015 Mercedes C400....I added:
JL Audio Fix 82 (to grab the speaker levels coming from the stock Burmester amp)
JL Audio VX 600/6i - driving 4"+tweeters in all 4 doors and also driving a pair of stock 6" midbass in the footwells
JL Audio ACP208LG-W3v3 - pair of 8" subs in a shallow box with an integrated 500W amp

After tuning, the system blows me away!

 

[Wayne A. Pflughaupt]

My apologies, I overlooked this previously:

Another thing I’ve been wondering, should the overall gain of the EQ generally be dropped by the height of the highest gain filter, to preserve the headroom in the signal processing chain? I found that with certain high-gain filters (+12dB and more) I’m occasionally getting distortions.

Certainly, any boosted filters means the equalizer itself has its headroom decreased by that amount. This would certainly be an issue with analog EQs. The same holds true with digital equalizers, but good-quality models with 24 bit processors should have headroom to spare. But if you’re getting audible distortion, then reducing the overall gain by the amount of the filter with the biggest boost should be sufficient.

Regards,
Wayne