digital signal processor

Hello Friends,
I have recently picked up a Koren product called Visualamp Digital crossover. I have a some doubts on the same. Please Help
here is the specifications of it.
Main Functions
1. DSP ( 24bit ) for Hi-Fi audio reproduction 2. Convenient GUI(graphical user interface) operations 3. 8 main channels:
*10-band graphic EQ curve adjustable(20Hz - 20kHz,-15 db ~ +15 db); * LPF adjustable(20Hz - 20kHz, ButterWorth/Bessel/BW:0.5~10 ) * HPF adjustable(20Hz - 20kHz, ButterWorth/Bessel/BW:0.5~10)
4. Precise digital adjustment of crossover point ( 20Hz - 20kHz,Slop:12db,24db,36db,48db)
5. 2-channel analog input / 4-channel analog input/supports optical inputs 6. 8-channel analog output :     ~2.5V 7. Adjustable sensitivity : 200mV ~ 9V
8. Adjustable delay 9. Input Voltage
: 168.2ms(1/2CH, 2/3CH) : 9v ~ 16v

In this they use Parametric/HPF/LPF with 10bands where in which i can choose the frequency, gain between +15db to -15db and also the Q between Butterworth and Bessel and BW. Also the unit has a crossover.
I am a little confused to use this Equalizer, Please explain how to set this up? Also do I need to use the crossover over and above the equaliser? I understand Parametric, but what does HPF and LPF got to do with eualizer? when I adjust the crossover the equipment says EQ modes of your existing data is erased, do you really want to continue. As far as i understand I guess user Equalizer is different than the crossover.. Please correct me if i am wrong and whats the use of HPF and LPF on all 10bands of EQ setting? also which is a better filter Bessel or butterworth? Please explain

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K. Venugopal Rao

Equalisers are a pre-amp function, not a speaker driver.

A crossover is usually a part of the speakers - eg, when multiple speakers are driven by a single channel (amp output).   

(I'm not into audio - others may explain better.)

I'd suggest referring to Wiki eg wiki Equalization_audio & wiki Audio_crossover.

You can wiki the other expressions too.

The functions and specs of that DSP (digital signal processor ) are very good. The HPF (high pass filter) allows you to keep lower frequencies (what ever frequency you set it to and below) from reaching the speaker. The LPF does the opposite and only allows frequencies lower than the frequency you set it to to reach the speaker (usually a midbass or subwoofer). The different slopes (12,24,36,48db) dictate how rapidly the frequencies above or below the set frequency drop in strength.

Im on my phone at work right now. Ill continue later.

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Dodge Magnum in progress:
Pioneer DEH-80PRS - PPI Amps - Dayton Subwoofer(s) - Exodus Anarchy's - Vifa Tweeters - Kinetik Battery

I guess my question I posted is wrong, Please check this link for details. https://blog.naver.com/spy516/40102045642. I this image u can see a 10band graphic EQ, Totally u will see 11bands, the first one is the preset I guess (Now whats this preset for?) and now here in this frequency we have a drop down box where in which we can select between (OFF or LPF or HPF or Parametric) now my question is why do i need HPF/LPF/PARAmetric for all 10bands and whats is the preset for? over and above this I also find a crossover to adjust, if Crossover is present why is the HPF/LPF provided on all 10 bands? and what do we mean by Biquad of each channel?

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K. Venugopal Rao

That is parametric, not graphic.

I reckon if you don't know why you need a parametric, then stick with a graphic.
Parametrics allow YOU so select the center frequencies whereas these are present in graphics - eh, ever 1/3rd Octave.

If yo want LPF or HPF etc for any channel, you can have that. Remember - this unit has 8 output channels - not (2 in &) 2 out like "normal" graphic equalisers.


How many amps with how many channels are you running - 2 plus a sub?

I am using 7channels Channel1 and 2 for the tweeters channel 3and 4 for mid range woofers for the front doors. and channel 5 and 6 for full range rear door speakers and channel 7 for the Sub. I am used to set the crossover now the EQ has HPF and LPF and parametric how do i set them?

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K. Venugopal Rao

So you have 7 amplifiers?

3amplifiers one 4 channel amplifier for tweeters and front mid speakers. One 2channel for the rear full range speakers. One mono amplifier for the 2 sub's.


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K. Venugopal Rao

Cool. So then you can connect each channel to whichever amp is applicable.

That assumes you can get the eq that you want from JUST one channel on the parametric - eg, LPF for the sub, HPF for the tweeters, and tunable notch or pass for the mids.
If you need more than one mixing channel on the parametric, then something will have to miss out and go straight thru, or via another eq.

I still doubt that it is what you want, I think a graphic eq is more suited. But I can see the parametric being useful for an already tuned system that needs some simple eq if the enclosure changes - maybe remove some resonant pole, or boost low frequencies etc.


I'll leave it to others to suggest how to set....

kureti wrote:

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I this image u can see a 10band graphic EQ, Totally u will see 11bands, the first one is the preset I guess (Now whats this preset for?)

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"Wrong approach for audiophiles
Authored by: tc_nyc on Sep 02, '04 02:40:55PM
As an audio engineer and producer with 18 years of experience in the field working in some of the 'finest studios in the world', I'm confident in saying that this approach is backwards.

Equalizers in both the analog and digital realm do subtractive filtering far better than additive filtering. When pulling the EQ down you are not creating the additive comb-filtering necessary to boost frequencies that do not already exist, so using this kind of approach is leaves more of the original audio intact and does not add as many artifacts to the signal.

What would be more appropriate, and also avoid unnecessary distortion, is to do all of those adjustments subtractively, then making up the gain difference with the slider at the left. This is why the slider on the left exists, in case you were wondering."

This is were I found that.

kureti wrote:

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now here in this frequency we have a drop down box where in which we can select between (OFF or LPF or HPF or Parametric) now my question is why do i need HPF/LPF/PARAmetric for all 10bands

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Studying the one screenshot I believe you can set a different EQ and crossover for each channel by clicking the boxes labeled 1/2, 3/4, 5/6, 7, and 8 at the top of the screen(notice the color codednesss and that CH1/2 is red and the graph being shown is red). Therefore it would make sense that the hpf and lpf functions of the DSP are integrated into the EQ and you can have separate EQ's for each channel.

By clicking one of the channels and typing in say 80Hz in the far left EQ band and then selecting HPF you have set the crossover for those channels and then you can set the 9 other EQ bands to the right of that to Parametric and set them to different frequencies you want to EQ.

If I am correct then I might also assume that you could band pass one of the channels by setting the far left EQ band to HPF and the far right EQ band to LPF with the bands in between set to parametric.

If you don't need to EQ 8 or 9 other frequencies then select off.

kureti wrote:

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over and above this I also find a crossover to adjust, if Crossover is present why is the HPF/LPF provided on all 10 bands?

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The crossover adjust is probably to set the slope (12,24,36,48db) and model (butterworth etc.) of the crossover for that channel.

At this point I guess I should check to make sure you are running all of your speakers active (as apposed to using the passive crossovers that most likely came with your speakers unless you got them somewhere like parts express or madisound) because that is what this device is made for.

I hope some of that will answer your questions and if it didn't let us know.


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Dodge Magnum in progress:
Pioneer DEH-80PRS - PPI Amps - Dayton Subwoofer(s) - Exodus Anarchy's - Vifa Tweeters - Kinetik Battery

excellent. Thanks a ton that kind of sorts out my worry. I will try them on now.
I am running all the speakers active _ i am not using any passive crossover networks.
What does a biquad mean? and when i adjust the crossover seperately and apply these settings it will override my equalizer.

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K. Venugopal Rao

I don't know what a biquad is or where you see that in the specs so I can't make an educated guess like I did for your other questions lol.

Could you clarify what you are doing/changing in the program when you adjust the crossover and it resets the EQ?

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Dodge Magnum in progress:
Pioneer DEH-80PRS - PPI Amps - Dayton Subwoofer(s) - Exodus Anarchy's - Vifa Tweeters - Kinetik Battery

thank you for a detailed explanation. I am yet to understand the presets. I have tried the explanation you gave me and its excellent. I am using 2 Sub's at the rear boot, I find the bass to come from the rear and the imaging is poor with the sub base being right at the back. rest all the speakers have an excellent front staging. I tried varied parametric eq but still not able to understand how I can push the sub base to the front. I also like to clarify, how do i test the signals using pink noise and RTA.

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K. Venugopal Rao

What are your crossover points for your sub's, front's and rear's?




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Dodge Magnum in progress:
Pioneer DEH-80PRS - PPI Amps - Dayton Subwoofer(s) - Exodus Anarchy's - Vifa Tweeters - Kinetik Battery