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In Reply to: RE: A stupid question... posted by KanedaK on June 02, 2017 at 18:03:13
Analog or digital EQ?
I used to do just that with an analog EQ that sounded a bit noisy and opaque in full-range use.
Digital will have some latency issues (delay) to deal with.
I'm using an analog active crossover on the low pass only.
The high pass is fed from the full range signal straight from the preamp to the power amp: I've created a first order high pass filter inside the power amp by changing the value of the input capacitors. The -3dB corner frequency is 100Hz. It's only purpose is to avoid amplifying unnecessary low frequencies. The power amp feeds the mid-high section of my preamp trough the original 3 way crossover. Passive high-pass at speaker level is 400Hz. Therés a 6 ohms resistor connected to the woofer outputs on the 3 way crossover.
The preamps second output goes trough an analog crossover and feeds the bass amplifier driving the bass horns.
That's where i wanna insert an analog equalizer.
Reason I use this "half passive / half active" bi-amp setup is that I really can't stand the sound of my active crossover in the midrange and high frequencies. Doing like I do gives me maximum transparency and with the low bass filtered from the mid-high amp I don't have any headroom problem.
Problem I'm trying to fix is a peak centered around 125Hz (150?) that's due to the bass horns and most likely worsened by the room acoustics.
That Audio Control Richter scale looks like a great product: I could have crossover and equalizer in the same box, would be ideal!
Huh? And what speakers are these?
"The power amp feeds the mid-high section of my preamp trough the original 3 way crossover..."
I think this is a typo? I presumed your preamp was feeding two power amps:
- 1st with active lowpass (what frequency/slope/etc?) feeding the woofer horn.
- 2nd running quasi-fullrange (actually with 1st order highpass @ 100 Hz) feeding the original speaker passive crossover which then highpasses the mid at 400 Hz and whatever for the tweeter.
Or did you actually pull out the crossover and put it in series with the...preamp??
As for "Therés a 6 ohms resistor connected to the woofer outputs on the 3 way crossover"
- Is that to not have the crossover leg "open"?
That resistor is just wasting power and reducing headroom, if you could specify/sketch the crossover we could help you disconnect the woofer lowpass section entirely.
As a loudspeaker design engineer, yes, I agree sometimes it can be hard or not really possible to replicate a passive crossover actively, whether via analog or digital.
Howver, I wonder what your 400 Hz highpass network looks like-and if you couldn't simply change your capacitor to 400 Hz and adjust the lowpass for blending. If the mid really needs 12 dB/octave, you could additionally put a capacitor across the input and get a shallow 12 dB (unless the internal capacitor is essentially at the input, unbuffered)
Yup of course it's a typo. I'm writing from my phone, sometimes while I'm in the public transports :) sorry about that. Of course I meant that my preamp has two outputs, one that feeds the mid/high amp full range, the second feeds the bass amp trough an active crossover.
I appreciate your concern, however I believe I have found a very decent compromise here. The only thing I might wanna do is play with a steeper crossover on the low pass, to hear the difference, but driver integration isn't really an issue so far (probably due to the lowish 400Hz xover frequency.
At some point I might wanna try the HD version of the miniDSP but somehow going digital freaks me out.
I chose a 100hz corner frequency on the high pass (capacitor) to not mess with the passive crossover slope + natural horn/driver roll-off.
I put the 6ohm resistor on the woofer crossover leg as recommended by the designer of the network I'm using (ALK engineering "universal", original version)
Apparently doing so allows the crossover to keep presenting a flat 8ohm load to the amplifier. I'm no crossover specialist so cannot comment on that, however those were expensive networks and I don't wanna take them apart or mess with them.
If there is a loss of headroom I really can't hear it (especially since I filtered the < <100Hz frequencies out). I would have the police at my door before my 8watts driving the mids-high starts clipping!
Now I understand, it's all compromise and a work in progress. But it sounds great. Just have a 150Hz bump that is due to the bass horns used (peavey FH1) and that I would like to tame down - subject of this post.
One day I will go for fully active - "the right way" when funds allow me to get something that sounds as good as my preamp does. Anything that makes the sound grainy, hazy, grey - like a lot of cheaper opamp based designs- is a big no-no to my ears. :)
I'm not sure how you are measuring the 150 Hz bump, but I wonder if it is the horn (as someone else said) or the room. Is there still a bump if you measure right in the horn throat? Well, it can be hard to separate horn vs. room since the room loads the horn and walls can act like an extension. I guess I'd be curious if there is a bump at 150 Hz out in a free field. But maybe that is so much trouble to move everything that EQ is easier!
KanedaK wrote: "At some point I might wanna try the HD version of the miniDSP but somehow going digital freaks me out. "
I went digital with a DSP from DEQX. I have never regretted it. Some folks such as Jonathan Valin of the Absolute Sound claim to hear distortions introduced by digital circuits. I don't. My speaker rig is an all horn loaded triamplified system capable of very high resolution. Everything digital DSP does right far outweighs any possible problems.
I agree with you Don.
Modern digital processing from Microphone input to DACs is in 32 bit/96 Khz. MINIMUM these days.
135 db dynamic range with 24 bit resolution is a million time better than any analog device at both ends of the chain.
Those that proclaim otherwise are afraid of the ABX box that would prove them so totally misguided.
The problem you are trying to fix is inherent in the FH-1 and LaScala SHORT HORN bins. It's at about 140 Hz. with a 7 db peak.
You can get a 2 channel mini DSP at a little over $100 to take care of that problem, which we all have had.
I'm assuming you are using a subwoofer below 100 Hz. Which is the best way to go, especially if it's a horn.
How I got rid of that 140 Hz. peak, is I designed a Quarter Pie bass horn and uploaded it on the Klipsch forum to help others do the same. But I still ended up with subs below 50 Hz. (twin Danley DTS-10's)
You get an extra octave of bass for free (flat to 50 Hz. with K-33)and a much flatter response and it only sticks out an extra foot from the corner.
DJK is correct about latency issues of digital crossovers. However it happens to both the bass and treble sections equally, so the net effect is inconsequential.
If the operating frequency is 96 Khz vs. only 48 Khz., then the latency will be half as much with the 96 Khz. filter.
Matters nothing what latency the crossover has, he is talking about adding an EQ into the low-pass output, and if it's digital it will have its own latency issue.
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