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 Post subject: For those that EQ...
PostPosted: Sat Apr 30, 2016 6:48 pm 
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I have borrowed a two-channel, 31-band graphic EQ and would like some insight into the methodology:

Are you supposed to measure each speaker on it's own and EQ it's response to be flat? Or, measure the stereo signal and EQ identically?


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The last couple days have been an interesting exercise. The comparison of EQ in vs out is eye-opening... even with room problems a reduction of the major peaks and a small boost here and there really opens things up and instrumentation and vocals have a silky harmonic richness. Things aren't perfect, as I'll go into below, but they are getting better.

Here you'll see the L and R measurements with and without EQ, 1/3 smoothing has been applied to make things a bit easier to visualize:

Attachment:
Rmeasurement.jpeg
Rmeasurement.jpeg [ 190.06 KiB | Viewed 2288 times ]

Attachment:
Lmeasurement.jpeg
Lmeasurement.jpeg [ 142.7 KiB | Viewed 2288 times ]


I have since re-EQ'd to bring down the bump between 3kHz and 7kHz on both sides and the mini-peak about 2.2kHz on the right, but I've not measured this outcome yet.

The most startling revelation is just how high the roll-off starts in the bass region. What I will try tomorrow is moving the speakers around while pinking with the RTA activated.

What's not surprising to me is the amount of comb-filtering going on in the high frequencies. Here's what the sweep looks like when no smoothing is applied. It's a capture of only the higher frequencies, with the 1/3 smoothing of the EQ's response put in just for reference:
Attachment:
combfiltering.jpeg
combfiltering.jpeg [ 286.93 KiB | Viewed 2288 times ]

I plan to tackle this problem with further treatments tomorrow. First will be a 4' by 4' "echo buster" I'll put on the wall behind the speakers; wood frame, fabric wrapped with a mild layer of batting in behind. Provisions for two more 4 by 2 busters are on to be placed on the same wall at the rear wave impact point. The 4 by 2 frames I'm thinking to mount over a QRD or Skyline type diffusor to aid in breaking up the comb effect over a wider band.

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 Post subject: Re: For those that EQ...
PostPosted: Sat Apr 30, 2016 7:25 pm 
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Location: Vernon, BC, CA
Measure together for a reference.
Then one side at a time, adjust the speaker slightly.
Measure both again.

Repeat.

High frequncies are very hard to measure acurately, so be less concerned with peaks and valleys anout 8kHz.

Can you measure the RTA?


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 Post subject: Re: For those that EQ...
PostPosted: Sat Apr 30, 2016 7:42 pm 
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Hi Jared, thanks for plugging in. Yes, RTA can be done. I was going to run pink while viewing the RTA to first determine the ideal listening spot, then tackle speaker placement.

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 Post subject: Re: For those that EQ...
PostPosted: Sat Apr 30, 2016 10:06 pm 
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Measure each speaker independently just to ensure there are no significant deviations between the two and adjust judiciously, then as a Left and Right sum with equal compensation.
If you like what your hearing now, you will love what a parametric EQ can do. I find the ISO fixed center frequencies on graphics to rarely coincide with problem areas.
Depending on your measurement software's RTA resolution or if it has FFT capabilities, you will really appreciate the flexibility that a parametric offers. And because less filters are eventually employed, less filter induced phase shifting will occur.


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 Post subject: Re: For those that EQ...
PostPosted: Sun May 01, 2016 1:46 am 
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Are you using band limited sweeps? No response below 170ish hz? I would check and see if the EQ module is filtering out bass frequencies. Is there a high pass filter engaged somewhere?


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 Post subject: Re: For those that EQ...
PostPosted: Sun May 01, 2016 2:34 am 
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Michael F wrote:
Measure each speaker independently just to ensure there are no significant deviations between the two and adjust judiciously, then as a Left and Right sum with equal compensation.
If you like what your hearing now, you will love what a parametric EQ can do. I find the ISO fixed center frequencies on graphics to rarely coincide with problem areas.
Depending on your measurement software's RTA resolution or if it has FFT capabilities, you will really appreciate the flexibility that a parametric offers. And because less filters are eventually employed, less filter induced phase shifting will occur.

Michael, the GEQ I have on loan in is the $1k range, which PEQ (preferably with Q control and more than 3-bands) are out there around this price?

-- 01 May 2016 05:46 --

Serenity_now wrote:
Are you using band limited sweeps? No response below 170ish hz? I would check and see if the EQ module is filtering out bass frequencies. Is there a high pass filter engaged somewhere?

20-20kHz sweeps were done, the bass roll-off is closer to 6db per octave but nulls make the smoothed curves look closer to 12db. The LPF and HPF are off.

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 Post subject: Re: For those that EQ...
PostPosted: Sun May 01, 2016 5:54 am 
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download the gold line dsp30 manual.....great instruction how to eq with RTA

start at page 26

happy reading :)

http://www.gold-line.com/pdf/manual/p_dsp30.pdf


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 Post subject: Re: For those that EQ...
PostPosted: Sun May 01, 2016 8:26 am 
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Which EQ are you currently using? $1000 will get you a fine equalizer and there are many choices in analog or digital. I`ve no experience with commercial grade units but there is lots out there from the likes of Klark-Teknik, Brooke Siren Systems, XTA, Yamaha to name a few which are all pro units but dont let that scare you off, they can just as easily be run unbalanced.

What software are you running, where are you taking these measurements from? Are the microphone and hardware calibrated and responses compensated for within the software?
Judging by your initial pre-EQ sweeps, your speakers appear to respond the same, always a good thing to know before applying any kind of EQ.


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 Post subject: Re: For those that EQ...
PostPosted: Sun May 01, 2016 8:52 am 
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Michael F wrote:
Which EQ are you currently using? $1000 will get you a fine equalizer and there are many choices in analog or digital. I`ve no experience with commercial grade units but there is lots out there from the likes of Klark-Teknik, Brooke Siren Systems, XTA, Yamaha to name a few which are all pro units but dont let that scare you off, they can just as easily be run unbalanced.

What software are you running, where are you taking these measurements from? Are the microphone and hardware calibrated and responses compensated for within the software?
Judging by your initial pre-EQ sweeps, your speakers appear to respond the same, always a good thing to know before applying any kind of EQ.


I'm using a KlarkTeknik 370 right now and have done the measurements with this in place. I also have a driverack260. Comparing the two, the KT is more transparent, though the 260 has more utility. I'm actually using either as a buffer: getting benefit of the low output impedance as my passive (transformer) pre doesn't drive the amp adequately. The amp has balanced ins.

I'm using REW software with ECM8000, XENYX502, UFO202 hardware. The mic has not been calibrated, but this older 8000 has been compared against a calibrated Dayton and it's very close - not the same as have the cal'n file, but it's doing a job in a pinch.

Mic is placed at my preferred listening spot. I'm about to start today with more mic'ing - using the RTA to determine a speaker placement that can improve the bass response.

Here are some more renderings from the initial measurements:


Attachments:
specto.jpeg
specto.jpeg [ 180.73 KiB | Viewed 2042 times ]
filtered ir.jpeg
filtered ir.jpeg [ 100.24 KiB | Viewed 2042 times ]
waterfall no eq.jpeg
waterfall no eq.jpeg [ 384.24 KiB | Viewed 2042 times ]

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 Post subject: Re: For those that EQ...
PostPosted: Sun May 01, 2016 9:26 am 
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370, nice. I can see it being more transparent than the DBX. The digital EQ`s and drive rack type processors offer much more flexibility but often at the expense of sonics. Manipulating the signal once in the digital domain has less sonic impact on the signal than the choices of AD,DA converters and their implementation.
Check out older units such as the DN-360 or Dn-410 which can be had for very little money.

A few very important things to keep in mind when equalizing is being aware that when taking measurements at the listening position, chances are good that you are likely well within the reverberant field that is to say, the direct-to-room ratio of sound diminishes with distance. You are trying to compensate electrically for physical problems created in the time domain, less EQ is more.
Room treatments and speaker placements are more effective at taming things.


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 Post subject: Re: For those that EQ...
PostPosted: Sun May 01, 2016 10:05 am 
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The KT DN370 is a very good eq if it is clean.

It also has two very narrow sweepable filters (per channel) that can be used more like a "scalpel" than the "butter knife" 1/3 octave filters. These can be very effective and transparent.

Jon


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 Post subject: Re: For those that EQ...
PostPosted: Sun May 01, 2016 10:34 am 
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Neal C wrote:
The KT DN370 is a very good eq if it is clean.

It also has two very narrow sweepable filters (per channel) that can be used more like a "scalpel" than the "butter knife" 1/3 octave filters. These can be very effective and transparent.

Jon

If by 'clean' you mean in good shape then yes, it is. It was unused until I plugged it in and turned it on. :D

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 Post subject: Re: For those that EQ...
PostPosted: Sun May 01, 2016 1:33 pm 
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I'm not sure what happened here, but today the roll-off at either end isn't as drastic. Maybe the rainy weather has some effect? lol

Attachment:
stereo open.jpeg
stereo open.jpeg [ 150.11 KiB | Viewed 1976 times ]
Attachment:
stereo waterfall.jpeg
stereo waterfall.jpeg [ 321.59 KiB | Viewed 1976 times ]
Attachment:
stereo specto.jpeg
stereo specto.jpeg [ 169.55 KiB | Viewed 1976 times ]


I've not completed the treatments yet, nor have I had time to muddle with the speaker placement, my wife is about the condo doing chores and the laundry is going. So much for tweaking for a couple hours...

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 Post subject: Re: For those that EQ...
PostPosted: Sun May 01, 2016 3:56 pm 
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There seems to be reasonable ringing at 50hz (2nd order length modal resonance?) and a problem present in your high treble There should not be that kind of ringing in your plots that high. Something seems faulty.

Try reducing your point sampling to 8000 or so to increase your sampling frequency. This will help you get a better feel for what is going on in the warerfall plot time domain. I woulnt trust those measurements till you find out where that nasty high freq vibration is coming from.


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 Post subject: Re: For those that EQ...
PostPosted: Sun May 01, 2016 5:21 pm 
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Serenity_now wrote:
There seems to be reasonable ringing at 50hz (2nd order length modal resonance?) and a problem present in your high treble There should not be that kind of ringing in your plots that high. Something seems faulty.

Try reducing your point sampling to 8000 or so to increase your sampling frequency. This will help you get a better feel for what is going on in the warerfall plot time domain. I woulnt trust those measurements till you find out where that nasty high freq vibration is coming from.

I thought that the >7kHz ringing was bizarre. Might it be the mic mounting? I'm using a camera tripod with the mic tied down with elastics; I'm out of duct tape lol. The tripod is lightweight, and as I just double-checked... some of the locking nuts (to the swivel, to the lift, and to the tilt) weren't that secure. Also, the mic has a fair amount of play to it.

I started with the speaker placement 50.5" from the front wall and about 60" apart (measurements taken earlier today). These are the latest plots:

Attachment:
may1 spl and phase.jpeg
may1 spl and phase.jpeg [ 218.41 KiB | Viewed 1905 times ]

Attachment:
may1 specto.jpeg
may1 specto.jpeg [ 189.13 KiB | Viewed 1905 times ]

Attachment:
may 1 waterfall.jpeg
may 1 waterfall.jpeg [ 313.49 KiB | Viewed 1905 times ]


Speakers are now 45" apart (from the inside edge of the baffle) and only 42" from the front wall. The sound is more coherent, but, with the speakers being closer together the stage is quite a bit smaller. The positions are marked with tape for reference; the smaller scale will take some getting used to - but this could also be a result of playing at a lower db level now that it's 9PM on a Sunday.

-- 01 May 2016 20:22 --

renehuot70 wrote:
download the gold line dsp30 manual.....great instruction how to eq with RTA

start at page 26

happy reading :)

http://www.gold-line.com/pdf/manual/p_dsp30.pdf

Thanks! This helped today.

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