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Author Topic: Advice On Eq for TFM122M Wedges  (Read 1168 times)

John Schalk

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Advice On Eq for TFM122M Wedges
« on: May 24, 2021, 05:41:15 PM »

One of my goals for this year is to learn how to use some of the audio analysis software that is out there.  I decided to start with Room Eq Wizard.  Even though its primary user base is the home theater market I've found some helpful YouTube videos that allowed me to take my first series of measurements.  I took my measurements outside in my driveway as far from any boundaries as I could get.  I decide to post the As Is measurements first and get some input before moving from the science of measuring speakers to the art of applying Eq or other filters to them.

In the screen shot, I've moved the average response up by 6dB to make it easier to compare to actual measurements.  I reduced the ground plane measurement by 3dB to match it to the three mic stand measurements, before averaging.  I used 1/24th octave smoothing.  The only processing I applied was the manufacturer's recommend HPF which is a 24 dB Butterworth @ 58Hz.

My first question is about the dip from ~200Hz to ~400Hz.  It's not present in the ground plane response, but shows up in all 3 mic stand measurements.  I believe that this is a cancellation from the ground and therefore cannot be corrected with Eq, is that right?

As far as any other changes to make, I feel like I should try to tame the low end a bit from 100Hz - 200Hz, the peak at 1.2kHz, the dip at 2.4kHz, and the peak around 6.5kHz.  Does that seem right? 
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Luke Geis

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Re: Advice On Eq for TFM122M Wedges
« Reply #1 on: May 25, 2021, 12:02:04 AM »

That actually looks pretty decent really as far as responses go. The dip at 250hz is likely from floor bounce and while you could EQ it out, it won't be right. I say leave that alone. It gets the mud out anyway. I prefer to high-pass my monitors pretty high, usually between 100 and 200hz depending on the instrument, the singer, and the size of the woofer. 15" usually has more low-end oomph, so I tend to roll more lows out with them. The ultimate goal is to reduce the amount of low end until the sound is natural and just full enough. I roll the HP up until the vocals sound thin and then bring it back down until it sounds right again. Usually around 140hz to 160hz.

As for the other dips, I would leave them alone. The one at 15khz is probably also another anomaly, a reflection from the horn into the grill and back of the horn or something. Or they did that on purpose to make the box have a sweeter-sounding high end? The only way to know for sure is to have a phase coherence trace. If the coherence dips at 250hz and 15khz, it is very likely reflections at the measurement mic causing the dips.

Objectively, you want to have the monitor be as linear as possible. This makes it less likely to be the cause of any issues making it easier to fix the problems at the mic channel as opposed to hacking your insert EQ to high hell. The old way of doing monitors was to turn things up until it rings, cut the offending channel on the insert EQ and repeat until you got three tones at one time. With a nice wedge, this could usually be done within 6 filters being engaged and not having much more than -6db of cut. Beyond that, you were spinning your wheels and you wouldn't get any further. With the advent of digital mixers, the game changed a little. I do not use graphic EQs inserted into my aux sends!!! If I/you can't get the monitor loud enough, stable, and sounding decent with the 6 parametric EQs most digital mixers provide, I/you am/are doing it wrong.

In your case, I would only worry about the two spikes you have at 1.2khz ( likely where the crossover starts to come into play ) and at 6khz where the dip is. There is some reason why there is a dip at 6khz with a small peak on either side of it, but what is causing that can only be determined with a coherence trace. If the trace is good and there is no other logical reason for it to be there, then it just is and all you can do is try to get the peaks to come down more linearly with the rest of the trace. Rolling the HP filter up will also get rid of the low-end build-up. I suspect by the time you roll it up to around 100hz, it will flatten out nicely.

The trace you have though looks pretty darn good though as it is. You shouldn't have too many issues getting a loud, clean, and effective monitor mix. I was looking at getting the TFM122 but was turned off by the seeming lack of availability, references, and reviews of them. I instead ponied up a little more cash and went with the RCF NX12SMA's. Very happy with that decision. They are board flat from 100hz to 16khz!!!
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Luke Geis

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Re: Advice On Eq for TFM122M Wedges
« Reply #2 on: May 25, 2021, 12:15:43 AM »

I took a quick peek at their online specs and the results you have are on par with what they present. The dip at 6khz is in their plot. It looks like they may have used a little more smoothing though. They do show a small dip at 15khz, but not like yours. The only thing in yours that doesn't align with theirs is the thing you have going on around 1.2khz. Which can either be because of the smoothing, their test conditions ( they say 1w/1m ), and environmental impacts. So to sum it up again, what you have looks good, you just need to get Smaart or something to really know more about what's going on.

https://mediadl.musictribe.com/media/sys_master/hc9/h38/8848079224862.pdf
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John Schalk

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Re: Advice On Eq for TFM122M Wedges
« Reply #3 on: May 25, 2021, 09:28:32 AM »

I took a quick peek at their online specs and the results you have are on par with what they present. The dip at 6khz is in their plot. It looks like they may have used a little more smoothing though. They do show a small dip at 15khz, but not like yours. The only thing in yours that doesn't align with theirs is the thing you have going on around 1.2khz. Which can either be because of the smoothing, their test conditions ( they say 1w/1m ), and environmental impacts. So to sum it up again, what you have looks good, you just need to get Smaart or something to really know more about what's going on.
Thanks Luke. I have a spreadsheet that lists Turbo's Eq recommendations for the TFM series, and their PEQ settings line up pretty well to my results too.  They suggest a bump at 300Hz, another at 780Hz, a cut at 1.15Hz, a boost at 2.4kHz, and a final cut at 4kHz.  The only one that doesn't jive with what I got is the cut at 4kHz.  I've added a screen shot of the SPL & Phase for the ground plane measurement.

I looked pretty hard at the RCF wedges myself, but ended up going with the TFM series in part because I already owned the amps.  Also, our forum friend, Mr. Pyle, and some in stock that he sold me for a very nice price, so the cost per monitor "channel" was much less than if I had started over with the powered RCFs.  My amps are PSoft M50qs with DSP, so my plan is to tune them to "flat" or something close based on this forum's help, and store those settings in the amps.  That's why I'm thinking of sticking with Turbo's recommended HP settings for the amp's DSP.  That way, if I need to use these for something other than vocal monitoring, I can. 

I have a Performer 2 which has 4 bands of PEQ on the bus outputs, but it also has a 1/3 octave Eq on every aux bus, so I plan to use those for feedback suppression and voicing.
« Last Edit: May 25, 2021, 09:36:00 AM by John Schalk »
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John Schalk

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Re: Advice On Eq for TFM122M Wedges
« Reply #4 on: May 25, 2021, 09:54:54 AM »

Here is an SPL & Phase plot for the ground plane measurement using REW's Variable Smoothing option which is defined as follows:

Variable smoothing applies 1/48 octave below 100 Hz, 1/3 octave above 10 kHz and varies between 1/48 and 1/3 octave from 100 Hz to 10 kHz, reaching 1/6 octave at 1 kHz. Variable smoothing is recommended for responses that are to be equalised.

With variable smoothing applied, the big dip around 15kHz disappears.  I wasn't planning to apply any Eq above 10kHz anyway.

Note: I just learned how to save an image of the plot area directly in REW and it makes tiny files which is certainly handy for use on this forum!
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Russell Ault

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Re: Advice On Eq for TFM122M Wedges
« Reply #5 on: May 25, 2021, 10:51:27 AM »

One of my goals for this year is to learn how to use some of the audio analysis software that is out there.  I decided to start with Room Eq Wizard.  {...}

Your timing for this goal is great: there's literally never been a better time to learn about this stuff. Rational Acoustics very generously posted their entire Level 1 training course as a series of YouTube videos (although I'd still recommend the in-person training if and when you get the chance), and the Smaart demo is fully-featured. If you wanted to stay with free software, Open Sound Meter uses many of the same principles as Smaart (and so a good portion of the Smaart training will apply to it, too).

Since your goal is to learn how to use analysis software (and not just EQ some speakers in the relative comfort of your driveway) I'd encourage you to start transitioning from REW to a real-time dual-channel analyzer as soon as possible (they are much more useful in the live audio world).

Here is an SPL & Phase plot for the ground plane measurement using REW's Variable Smoothing option which is defined as follows:

Variable smoothing applies 1/48 octave below 100 Hz, 1/3 octave above 10 kHz and varies between 1/48 and 1/3 octave from 100 Hz to 10 kHz, reaching 1/6 octave at 1 kHz. Variable smoothing is recommended for responses that are to be equalised.

With variable smoothing applied, the big dip around 15kHz disappears.  I wasn't planning to apply any Eq above 10kHz anyway.

Note: I just learned how to save an image of the plot area directly in REW and it makes tiny files which is certainly handy for use on this forum!

Also, I'd really encourage you to keep smoothing to a minimum, especially on the mag trace. Merlijn van Veen gives a great explanation here why, but you've already given yourself an excellent example: smoothing away the null around 15 kHz doesn't actually mean it's not there, it just means that the computer is telling you what is and isn't actionable data, rather than the other way around (and the computer just isn't that smart).

-Russ
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John Schalk

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Re: Advice On Eq for TFM122M Wedges
« Reply #6 on: May 25, 2021, 11:21:59 AM »

Your timing for this goal is great: there's literally never been a better time to learn about this stuff. Rational Acoustics very generously posted their entire Level 1 training course as a series of YouTube videos (although I'd still recommend the in-person training if and when you get the chance), and the Smaart demo is fully-featured. If you wanted to stay with free software, Open Sound Meter uses many of the same principles as Smaart (and so a good portion of the Smaart training will apply to it, too).
I was not aware that Rational had posted YouTube videos of their Smaart Operator Fundamentals class.  I noticed that the first couple of videos are 90 minutes long.  I guess that makes sense knowing that they're based on a multi-day, in person training program.  But it does mean that I'll really have to set some time aside to work my way through the class.  The good news is that I've put together a little sound analysis rig so I can set it up in the house and leave things hooked up while I go through their videos.  FWIW I chose REW over Open Sound Meter to get started precisely because there's almost no help available for OSM unlike REW which has tons of documentation, videos, and a very active user forum, even if it is mainly used by home theater enthusiasts.
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Russell Ault

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Re: Advice On Eq for TFM122M Wedges
« Reply #7 on: May 25, 2021, 12:03:58 PM »

I was not aware that Rational had posted YouTube videos of their Smaart Operator Fundamentals class.  I noticed that the first couple of videos are 90 minutes long.  I guess that makes sense knowing that they're based on a multi-day, in person training program.  But it does mean that I'll really have to set some time aside to work my way through the class.  The good news is that I've put together a little sound analysis rig so I can set it up in the house and leave things hooked up while I go through their videos.  FWIW I chose REW over Open Sound Meter to get started precisely because there's almost no help available for OSM unlike REW which has tons of documentation, videos, and a very active user forum, even if it is mainly used by home theater enthusiasts.

That's fair, and to be clear, there's nothing inherently wrong with REW (the math all works, etc.); it's just that its reliance on sine sweeps means it's not a particularly useful tool in live sound.

The videos are a titch on the long side, but the information they contain is vital. Make sure to grab the Smaart demo before you start watching so you can play along (but also know that at least 80% of the course content is just as applicable to other dual-channel analyzers, so if you ultimately decide to splash out for a SIM rig your time hasn't been wasted). :)

-Russ
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Art Welter

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Re: Advice On Eq for TFM122M Wedges
« Reply #8 on: May 26, 2021, 03:09:34 PM »

I have a spreadsheet that lists Turbo's Eq recommendations for the TFM series, and their PEQ settings line up pretty well to my results too.  They suggest a bump at 300Hz, another at 780Hz, a cut at 1.15Hz, a boost at 2.4kHz, and a final cut at 4kHz. 
I have a Performer 2 which has 4 bands of PEQ on the bus outputs, but it also has a 1/3 octave Eq on every aux bus, so I plan to use those for feedback suppression and voicing.
John,

Noticed you had applied a 58Hz HPF, the TFM122M box appears to be tuned to around 75Hz, a 70Hz BW24 will keep the cone from flapping  (making vocals gargle..) if you put kick or bass in it.

Almost all the peaks in the TFM122M correspond to it's narrowing pattern at those frequencies, cutting them to "flat" will improve gain before feedback stability, though those frequencies will also become relatively "dead" off axis.
A bump at 780Hz is in a range where the beamwidth is very wide, it makes sense.
Rather than "bumping" 300 Hz, loosing about 5dB from 90 Hz to 200Hz would loose the "mud" typical on stage from mains wrap, and the LF proximity boost from vocal mics, especially if you are running them pre-eq in the monitors.

The missing 16kHz "spike" in your 2M GP measurement is probably due to being off axis, beamwidth narrows to just 30 degrees above 10kHz.

For coax floor wedge voicing, I'd suggest putting the measurement mic as near to a typical (for your use) vocal height above deck (open air, away from any walls or large objects), directly on axis, and shoot for flat response, with a slight rolloff below 200 Hz tapering down to Fb.

Art
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Riley Casey

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Re: Advice On Eq for TFM122M Wedges
« Reply #9 on: May 26, 2021, 04:11:46 PM »

This goes to the heart of my experience retuning four different monitor rigs over the years, some with factory specs and some 'classic' designs.

- Avoid boosting frequencies in monitor tunings. Added gain makes them slightly more unstable
- High pass should be higher than the same box would be for full range / stick use - 60 to 80 hz
- turn down the high frequency driver - flat to 16k is not beneficial for a wedge monitor in fact anything above 10k is just a problem - in your last curve taking the HF driver down 2db would fix the bump just above crossover and and a shallow cut from 3k to 8k would yield a very stable wedge tuning for loud vocal monitors


...
Rather than "bumping" 300 Hz, loosing about 5dB from 90 Hz to 200Hz would loose the "mud" typical on stage from mains wrap, and the LF proximity boost from vocal mics, especially if you are running them pre-eq in the monitors.

...

Art

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Re: Advice On Eq for TFM122M Wedges
« Reply #9 on: May 26, 2021, 04:11:46 PM »


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