“Pre Filtering” or Frequency Balancing

[MF 1000]

On a whim whilst perusing eBay I acquired a Behringer 31 channel graphic equaliser …..loads of sliders with a red led in the centre of them. As this can boost or cut frequencies both above & below that if my two DSP units I was wondering if just using the 20 Hz (and maybe the 25Hz) sliders plus the 16 & 20Khz ones I could pre filter the signal exerting the DSP units.

A quick rig up this afternoon (now waiting for some longer balanced cables & splitters) had quite an effect.…..I left all other frequencies ‘flat’. The bass response was def flatter at the sub 25Hz level but I could only feed one DSP unit so the top end effect remains to be experience.

Quite a whacky approach I know ……but if you don’t try etc …

 

[awkwardbydesign]

I bought one too! The plan is to use it to get a level(ish) response using REW, and then modify the crossover to mimic that and remove the equaliser. A quick play with making a broad dip around 1kHz and cutting 32Hz (room mode) was promising. Of course it muddies the sound a bit, but when I have the energy I will do it properly.

 

[MF 1000]

Great minds think alike ….or at least I’m not the only unhinged one on here

 

[m7rso]

I aint got one, but I am unhinged.

 

[MF 1000]

Got home from my travel yesterday eve and my extra cables had arrived to rig up the equaliser in an accessible position.

had some time this afternoon and connected it in place between the DHT preamp and the two DSP units i operate. Initial impact was positive and I used REW to see how I could boost bass and top end frequencies prior to the DSP units.

After a while I decided to really go back to basics ….reducing all channels of the DSP units to zero gain and no filtration, then attempt get a basic ‘flat’ response curve and use the DSP units to carry out ‘fine’ corrections or band pass filtering etc.

After an hours tweaking I’ve seemed to get a curve ‘flat’ ie +/- 2.5 dB between 20Hz to 13Khz. Testing out the system with Marcus Millar Silver Rain and the theme tune to Taboo was the real thrill as bass was now trouser flapping but still with a clear and balanced midrange too.

More fine tweaking to do now and an order place for longer rack strip to mount the equaliser in the system.

 

[MF 1000]

Had a bit of time to do some further adjustments today and analyse with REW etc.
One thing I’ve noticed is that despite setting my sweep frequency on REW from 10Hz - 20KHz it seems to only actually sweep from about 35 Hz, which is a bit of a poor show - and I know my system has a good response down to 12 Hz

anyway after a few tweeks of the ‘pre filter‘ graphic and adjustments on the DCX units I’ve got the response curve below


quite a good flattish curve +/- 2.5 dB

 

[tuga]

Had a bit of time to do some further adjustments today and analyse with REW etc.
One thing I’ve noticed is that despite setting my sweep frequency on REW from 10Hz - 20KHz it seems to only actually sweep from about 35 Hz, which is a bit of a poor show - and I know my system has a good response down to 12 Hz

anyway after a few tweeks of the ‘pre filter‘ graphic and adjustments on the DCX units I’ve got the response curve below


quite a good flattish curve +/- 2.5 dB

How much smoothing did you apply, 1/6 octave?
I’d be much more worried about the trench between 50 and 150Hz than frequency extremes. You probably can’t hear anything above 16kHz and even the recordings with the most low end extension won’t have much information at 20Hz.

 

[MF 1000]

I always use psychoacoustic smoothing
The ‘trench’ in relatity is within the 5 dB spread of the rest of the response curve etc …..listening tests don’t reveal any issue to my ears

 

[tuga]

I always use psychoacoustic smoothing
The ‘trench’ in relatity is within the 5 dB spread of the rest of the response curve etc …..listening tests don’t reveal any issue to my ears

For EQing the speaker or crossover you should use no more than 1/24 and for room correction below 300Hz between 1/24 and 1/12.

+5dB is perceived as 50% louder.
It might be possible to reduce the range of the depression by moving the woofers and/or listening spot.

 

[MF 1000]

After an eBay debacle (apparently the trade seller not addressing the parcel correctly is somewhat my fault!!! ) ….my new rack strips arrived yesterday so today I’ve taken the rack apart, fitted the new strips, reassembled & tested etc


All back working ok and Yello …The Race sounding the best it’s ever done