I knew you will ask about that. I just complemented it to point out that for example, series crossover is not possible with active.
Yes, as you are aware, there are many things where it is not possible with passive. This is the advantage of active. The best design using active cannot be copied into passive. It is not apple to apple.
But where the active lost over passive is the extra electronics. This can be serious if you have low thresholds on total distortion and noise, and importantly, if you have ears for that matter.
I'm curious about others point of views than mine even if i don't agree.Spot on about series filters. I though about some possible interactions between drivers/passive filter too but i'm really not an expert and this is only assumptions.
For the extra electronics yes it can be real disaster if not properly implemented. I must admit that once you lived with 'big' analog desk and whole studio environment it is something much less of a concern as this is very complex systems and some of them do sound extremely goods. Not all of them but it's doable.
Even more when you have less to concern about big multiple psu, poor ground issues and less crosstalk to happen.
Spot on about series filters. I though about some possible interactions between drivers/passive filter too but i'm really not an expert and this is only assumptions.
For the extra electronics yes it can be real disaster if not properly implemented. I must admit that once you lived with 'big' analog desk and whole studio environment it is something much less of a concern as this is very complex systems and some of them do sound extremely goods. Not all of them but it's doable.
Even more when you have less to concern about big multiple psu, poor ground issues and less crosstalk to happen.
What is it that you achieve with series passive filters?
Thanks,
Chris
Series vs. Parallel Crossover Networks
But be aware Rod Elliott is biased... toward active multi amp.
But be aware Rod Elliott is biased... toward active multi amp.
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Personally, I think it would be helpful to those trying to learn if we could be a little more specific when discussing "active". When I read about the benefits of active, there seems to a very blurred line between what can be done with analog active compared to digital with a DSP.
It's very possible that I'm misinformed here as I know much less about what can be done with analog active than I do about what's possible with digital. But it seems that several of the things that can be done with active but not passive require DSP. Linear phase filters with FIR seems to me like the most obvious example. Can analog active filters do precise time delay for individual channels?
And the issue with loss of resolution when attenuating digitally is a pretty darn big disadvantage to what I'm trying to do with JRiver Media Center as the heart of my stereo system. It actually has me back to considering the efficiency of different drivers I may use together, to avoid too much attenuation of an individual channel in the DSP. Hopefully that's something I can partially deal with by tweaking gain settings at the amplifier but that's not really what amp gain settings are for.
Then there's the whole issue of some recordings having very different average and peak levels. JRiver has a volume leveling capability but I read that it works by digitally attenuating the higher DB level recordings. I've been paying attention to how I use the volume control on my stereo lately and I change it quite a lot as songs play back at different levels.
I still haven't done any critical listening with my headphones to see if I can actually hear a difference between digital or analog volume control. From what I've read in this thread, it might be most likely to be audible with my in ear monitors since they block environmental noise really well.
But I'm starting to ramble now.
-Chris
It's very possible that I'm misinformed here as I know much less about what can be done with analog active than I do about what's possible with digital. But it seems that several of the things that can be done with active but not passive require DSP. Linear phase filters with FIR seems to me like the most obvious example. Can analog active filters do precise time delay for individual channels?
And the issue with loss of resolution when attenuating digitally is a pretty darn big disadvantage to what I'm trying to do with JRiver Media Center as the heart of my stereo system. It actually has me back to considering the efficiency of different drivers I may use together, to avoid too much attenuation of an individual channel in the DSP. Hopefully that's something I can partially deal with by tweaking gain settings at the amplifier but that's not really what amp gain settings are for.
Then there's the whole issue of some recordings having very different average and peak levels. JRiver has a volume leveling capability but I read that it works by digitally attenuating the higher DB level recordings. I've been paying attention to how I use the volume control on my stereo lately and I change it quite a lot as songs play back at different levels.
I still haven't done any critical listening with my headphones to see if I can actually hear a difference between digital or analog volume control. From what I've read in this thread, it might be most likely to be audible with my in ear monitors since they block environmental noise really well.
But I'm starting to ramble now.
-Chris
Please Chris don't.
I'll try to summarize about active filtering ( active used alone means powered: loudspeaker with amplifier inside the box, filtering done either by passive or active...
).Active filtering analog line level can do anything a passive filter can do (except series filter): classic slope and classification (Butterworth, Linkwitz-Riley,etc,etc) all this is called IIR (infinite impulse response). It can do equalization being shelf or notch or parametric even 1/3 octave graphic eq. It can do some phase tweaks if it uses all pass filters.
It cant' do FIR (Finite impulse response) also known as 'linear phase filter'. It can't do DELAY duties with enough quality to be usable so we'll say it can't be done.
DSP active can do everything an analog unit can do plus FIR (but it'll depend on budget as not all hardware units can do them, nor every software) and delay (feature in every unit dsp based).
For the volume control: as long as you have your gain structure right don't freak out to use digital volume control! As you have read i have very specific needs and favor analog control but i could live with only a digital level control in my living room. I don't think you'll bother anytime soon to hear the artefact i have concern about.
Your experience about different volume between song is normal. This is why you'll use a digital volume control. The example given about gain structure is all but an exercice as you asked about how to determine it. It use 'worst case scenario' and this is the maximum level you'll probably ever need. Most of the case you'll use your level control to attenuate between lp, songs,...
Don't freak out, you've just entered the field and had a lot of information given... This is a lot to digest! For some of us it takes years to gain this knowledge ( well in my case if for others).
But at the end TAKE YOUR TIME about your project: envisage every possible scenario and make wise choice.
Disagree. The only difference between active analogue and passive is gain. Krivium sums it up.
Series crossovers have a sort of self compensating thing. Eg impedance variations are reduced and drivers with complementary errors can lead to a better crossover for a given number of components. If components are not a limitation then any benefits would be superficial.
Yes. Gain versus insertion loss. But even GAIN can mean a LOT of things... With gain, for example, you can modify Fc like in Linkwitz Transform circuit. There are many tricks utilizing this capability, but like Linkwitz' Orion, you will end up with a lot of electronic parts in the signal path. For some people ears this is okay, for some others this is not.
I disagree to disagree. In active analog you have some other things to your disposal than just copies of analog passive filters and gain.
Addition and subtraction for instance (while theoretically feasible) do not really make sense in passive.
There are some analog filter options with very low group delay distortion for instance that are very hard to do passively.
But these are things that you don't find in books generally.
Regards
Charles
Mixing or multiplexing? I wasn't really thinking beyond all ordinary crossovers and similar networks.
Are these in common use with the above qualification?
About what Tromperie?
I'm not trying to convince anyone that one is better than the other. I've heard great implementation of both and done the choice of dsp multiamp for myself, but the finest loudspeaker i've heard where the passive version i talked about.
I'm not an electronic genius, nor have the patience or budget to do a passive equivalent of my dsp multiamp, i'm using a fully digital chain so it was the obvious choice.
Let's say i have a illimited budget my choice could have been different!
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I think you just jinxed it Allen
I was quite surprised it had run as long as it has without degenerating, but may unfortunately have started the downward spiral. edit: lets see if we can buck the trend and keep a useful dialogue
It would be a VERY refreshing change! It's been good so far, lets keep it up!!Tony.
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You can do the classic subtractive networks, you can do subtractive-phase, subtractive delay and some mixed forms. You can do mixed forms between subtractive filters and ordinary ones. You can do compensation and filtering at once by the use of weighted summing of the outputs of state-variable filters.
And then there are in-phase filters with Q values different that 0.71 (theoretically any value possible within reason, LR4 is just a special case of a 4th order in-phase x-over BTW). But these will be asymmetrical 2nd/4th or 4th/2nd and one definitely needs summing or subtracting to do these.
My next project will use a mixed form of analog active xover topology with crossover frequencies of 1300 Hz and 200Hz. Its total x-over induced group-delay distortion will be +- 110 microseconds approximately (the same as a 2nd order LR @ 1.4 kHz) but it will be steeper than a 2nd order LR and the group delay will be flat up to around 2.5 kHz.
One important part of it will be subtraction. For the development I will use a DSP board with AD's Sigma Studio and the final one will be analog.
Regards
Charles
And then there are in-phase filters with Q values different that 0.71 (theoretically any value possible within reason, LR4 is just a special case of a 4th order in-phase x-over BTW). But these will be asymmetrical 2nd/4th or 4th/2nd and one definitely needs summing or subtracting to do these.
My next project will use a mixed form of analog active xover topology with crossover frequencies of 1300 Hz and 200Hz. Its total x-over induced group-delay distortion will be +- 110 microseconds approximately (the same as a 2nd order LR @ 1.4 kHz) but it will be steeper than a 2nd order LR and the group delay will be flat up to around 2.5 kHz.
One important part of it will be subtraction. For the development I will use a DSP board with AD's Sigma Studio and the final one will be analog.
Regards
Charles
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