"This is a real world problem and DIYers go to a lot of effort in their self built active systems to reduce the levels of hum and hiss to negligible levels. Also the potential for increasing the levels of hum/hiss goes up when you add an active crossover to the system. To some people this is enough reason to stay passive!"
Ok, so I'll include a passive "hiss filter" in my next active build. XD
Ok, so I'll include a passive "hiss filter" in my next active build. XD
I have never experienced a "hiss" or noise issue with the active xovers I have built. The OPA 134 has something like 8nV/sqrt(Hz), which is about the equivalent thermal noise of a 3KOhm resistor at room temperature. And some newer opamps have noise even below that.
vac
Hi Tony
Thanks for the link. I did test out Rod's BSC circuit but I was not satisfied with the performance. I find electronics extremely invasive. If I detect a compromise in the sound quality, I cannot accept it. My approach is to preserve the integrity of the sound as much as possible.
Actually, I don't really apply textbook BSC. If it is for recording use, I aim for a flat response. For music, I contour the response to suite my ears. Doing this passively is less invasive.
Hiss hasn't be a problem for me, but it can be with some active filter stages, unless properly optimised. The trick in that situation is to place any low pass filters at the end of the signal chain. It also depends on how sensitive your loudspeakers are. I never had any real problems with small amounts of hum and buzz until I changed to the 95dB+ mid driver and wave-guide loaded tweeter, which places it's sensitivity in the mid nineties for a large portion of its pass band. That and I like to sit at <1 meter a lot of the time, you really have to have things sorted well in that kind of situation to keep everything really quiet.
Thanks Michael, That's interesting to hear! I've been tossing up whether to put it into my circuit, it definitely increases the distortion in sims with it in, and my latest revision to the passive crossover (my active is for sub to main) has BSC built in so I can probably do away with it entirely.
Tony.
As a counterbalance to Michael's experience, I used it in modding my active speakers and found it didn't compromise sound quality. Its all in the implementation
I did find that it only needs to be a modest boost, even with speakers free standing a smidgen less than 2dB was appropriate. On another pair of speakers which sit on small stands on my desk which is against a wall, even that amount gives overbearing bass.
Tinitus, I would regard Rod Elliots circuit as passive line level Baffle Step Compensation . If you put it before the active crossover then it will achieve the goal, that's what I was originally intending to do. However it needs at least a 100K impedance load to drive so will work best if driving a buffer before the active xo.
abrax, I will probably bread board it and make a decision if I need it or not thanks for the alternate view.
Tony.
abrax, I will probably bread board it and make a decision if I need it or not
thanks for the alternate view. Tony.
Running into any stage whose Zin is resistive in the passband, you can get 4dB of compensation (with an additional loss of 4dB), by using a series RC in parallel with the stage's input with the resistor being 0.6 x Zin. For this you would use a source resistance of the same value. ie: Rs = (0.6 x Zin of next stage) - Zout of the previous stage.
Hi - Can you specify the impedance of your speaker as is in this frequency range, and is it adjacent to an xover point? Also, any details in general you can provide would help frame a possible solution. Intentionally boosting voltage, or otherwise doing frequency selective impedance/voltage transformation with a passive network is anything but a conventional 'cookbook' approach and generally requires a good deal of specific information regarding the particular application such as speaker parameters, xover schematic and sometimes enclosure info.
Last edited:
Tony - is your nasty dip in the simulation or measured? I ask because I haven't yet come across a simulation that correctly handles proximity effect losses in multiple-layer inductors and your dip might be as a result of this. My B&W CM1s had exactly this kind of dip around that frequency region when I bought them, they use a single air-cored series choke wound with 2mm thick wire which has impressively low DCR but gets lossy before the XO frequency is reached. Not that any of this solves the dip of course...
Except for subwoofer use where I've gone the full active route, I usually have tried to keep line level EQ very simple, such as a first order passive and handle everything else with passive xover elements at the speaker itself. My experience is that a polypropylene capacitor in a passive speaker xover would sound 'better', (e.g., closer to the source) than, say, an signal coupling electrolytic or barium titanate ceramic capacitor in an active xover.
Of course, I should note the partial exception to the above that I use MultEQ for my HT system & speakers and find it mostly quite satisfactory for that. I have far fewer issues with high quality DSP of a signal that has already been digitized in the media than performing A/D/A conversion on top of active EQ, plus MultEQ gives time and frequency domain optimization which I don't believe most standalone active EQ's attempt.
Of course, I should note the partial exception to the above that I use MultEQ for my HT system & speakers and find it mostly quite satisfactory for that. I have far fewer issues with high quality DSP of a signal that has already been digitized in the media than performing A/D/A conversion on top of active EQ, plus MultEQ gives time and frequency domain optimization which I don't believe most standalone active EQ's attempt.
Last edited:
What leads you to select a piezoelectric material for your dielectric? Is it that you need a very large value in a small space? Myself I find NP0 caps sound better than (non-boutique) small signal polyprops but they are limited in regard to maximum value. At opamp kinds of impedances this hasn't so far turned out to be a practical limitation.
People who value the sound given by their expensive turntable would find a digital active crossover to be as unwanted as a pair of balls on their forehead.
Likewise a person who has a highly tweaked DAC or CD player. You just don't go spending thousands on your digital or analog front end (or tweaking it to the limits) , to go running the audio through a cheap behringer or miniDSP. You just don't! (Or just shouldn't)
Even if you stay in the digital domain, and run your digital XO into your prized DAC, there will be a change in sound. Of course some people hear no differences when they do this, and some people hear no difference between DACs. But for those who do, active crossovers are not for you.
Basically I've heard active systems many times (in fact on a weekly basis at work)
I really find no overwhelmingly strong argument in favour of electronic vs passive crossovers, except in high powered PA systems where the active XO gives a better damping factor of the subs and less power losses for the top boxes, and better flexibility when EQing the system for the room.
I find that digital crossovers very easily give a person the ability to give the system a flat frequency response, and if equipped, a flat(ish) phase response, but this does not necessarily result in a sound that is more enjoyable or grain-free as a passive crossover being driven by a nice HI fidelity front end. With most off the shelf affordable active crossovers using cheap op-amps and SMPS they often sound wrong to my ears.
Just giving an alternate viewpoint on this mostly one sided thread.
Otherwise I think digital crossovers are really impressive with what they can do.
Just not my cup of tea in a home system.
Likewise a person who has a highly tweaked DAC or CD player. You just don't go spending thousands on your digital or analog front end (or tweaking it to the limits) , to go running the audio through a cheap behringer or miniDSP. You just don't! (Or just shouldn't)
Even if you stay in the digital domain, and run your digital XO into your prized DAC, there will be a change in sound. Of course some people hear no differences when they do this, and some people hear no difference between DACs. But for those who do, active crossovers are not for you.
Basically I've heard active systems many times (in fact on a weekly basis at work)
I really find no overwhelmingly strong argument in favour of electronic vs passive crossovers, except in high powered PA systems where the active XO gives a better damping factor of the subs and less power losses for the top boxes, and better flexibility when EQing the system for the room.
I find that digital crossovers very easily give a person the ability to give the system a flat frequency response, and if equipped, a flat(ish) phase response, but this does not necessarily result in a sound that is more enjoyable or grain-free as a passive crossover being driven by a nice HI fidelity front end. With most off the shelf affordable active crossovers using cheap op-amps and SMPS they often sound wrong to my ears.
Just giving an alternate viewpoint on this mostly one sided thread.
Otherwise I think digital crossovers are really impressive with what they can do.
Just not my cup of tea in a home system.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.