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http://www.diyaudio.com/forums/multi-way/276019-active-analog-xo-vs-passive.html#post4364126
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How's that? Can you explain further what you mean?
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Audio amplifiers are secretly (well not such a secret) voltage amplifiers, not "power" amplifiers.
by splitting the spectrum into, lets say notionally "bass", Mid" and "high" the voltage swing required of each power amplifier is defined by the voltage in that spectral band.
The normal mode of clipping seen in music is midrange and high frequency peaks being clipped as a consequence of the large voltage swings required to deliver the low frequency component. Look around, there are some good articles on this.
This allows:
- The bass to be handled by a big amp, which is not also trying to drive a number of volts into mid / twt. Those extra volts make a huge difference
- The amplifier driving the mid / twt output is not also swinging large voltages to drive bass / subs.
Additionally, if you do clip the bass, it is actually a lot less obvious than mid / treble clipping.
If you haven't tried an active XO and like your music loud / with large dynamic range, give one a swing.
by splitting the spectrum into, lets say notionally "bass", Mid" and "high" the voltage swing required of each power amplifier is defined by the voltage in that spectral band.
The normal mode of clipping seen in music is midrange and high frequency peaks being clipped as a consequence of the large voltage swings required to deliver the low frequency component. Look around, there are some good articles on this.
This allows:
- The bass to be handled by a big amp, which is not also trying to drive a number of volts into mid / twt. Those extra volts make a huge difference
- The amplifier driving the mid / twt output is not also swinging large voltages to drive bass / subs.
Additionally, if you do clip the bass, it is actually a lot less obvious than mid / treble clipping.
If you haven't tried an active XO and like your music loud / with large dynamic range, give one a swing.
No worries, I've been using active crossovers for decades. 
However, the only real dynamic gain you've described is achieved by using a bigger amp - your bass amp. If you used an amp with the same headroom for the whole speaker, wouldn't dynamic range be the same?
There are some ways to cheat it a bit with active, but I don't think you gain that much.
However, the only real dynamic gain you've described is achieved by using a bigger amp - your bass amp. If you used an amp with the same headroom for the whole speaker, wouldn't dynamic range be the same?
There are some ways to cheat it a bit with active, but I don't think you gain that much.
This articleexplains quite nicely the advantages of going active:
BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 1
BiAmp (Bi-Amplification - Not Quite Magic, But Close) - Part 1
Hi,
Take a 100W amplifier and any 3 way speaker.
Now sensibly tri-amp with 100W in the bass and enough
power for the mid and treble, usually about 50W and 25W.
The active system will easily play wideband levels requiring
200W to 400W unclipped into the original speaker, but of
course not be capable of playing bass only any louder.
Which only goes to show that for wideband 100W unclipped
programme into a speaker the bass power never approaches
100W nearly all of the time, its reduced by the midband
clipping headroom required, to average say about 10W.
When you go active the bass can clearly go louder, if
the actual bass driver can handle the extra SPL well.
rgds, sreten.
Active bi-amping at around 300Hz will give a system
that plays 6dB peak louder than a single amplifier,
e.g. 50W+50W biamping is equivalent to 200W,
regarding maximum peak program levels.
Take a 100W amplifier and any 3 way speaker.
Now sensibly tri-amp with 100W in the bass and enough
power for the mid and treble, usually about 50W and 25W.
The active system will easily play wideband levels requiring
200W to 400W unclipped into the original speaker, but of
course not be capable of playing bass only any louder.
Which only goes to show that for wideband 100W unclipped
programme into a speaker the bass power never approaches
100W nearly all of the time, its reduced by the midband
clipping headroom required, to average say about 10W.
When you go active the bass can clearly go louder, if
the actual bass driver can handle the extra SPL well.
rgds, sreten.
Active bi-amping at around 300Hz will give a system
that plays 6dB peak louder than a single amplifier,
e.g. 50W+50W biamping is equivalent to 200W,
regarding maximum peak program levels.
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Please don't mix "gain" and "max power".
Yes, when you active cover the same amp can handle more input level and output louder as the input range is nerrower.
But at the same input level as before, it will output same loudness or a little bit louder as the load from speaker is smaller ,but not much. That's the amplifier gain. It is same as before.
Yes, when you active cover the same amp can handle more input level and output louder as the input range is nerrower.
But at the same input level as before, it will output same loudness or a little bit louder as the load from speaker is smaller ,but not much. That's the amplifier gain. It is same as before.
Hi,
And your point is ? Other than confusing the issue.
E.g. active biamping @ 300Hz and a mixed signal of 100Hz and
1KHz at the same level, with 50W output at clipping level for both.
The added voltage swing across both drivers would need 200W.
If you go 3 way and 300Hz and 3KHz, with 100Hz,1KHz and 10KHz,
the added voltage swing would need 450W, versus 3 50W amplifiers.
Real life active doesn't reflect such gains, for lots of practical reasons,
but there is a lot to be said for active biamping, especially with very
expensive watts, like valve stuff, coupled with solid state bass.
rgds, sreten.
I totally agree your point and we are on the same page.but lots of people think if they change from a 50W amp to a 200w amp the loudness will be 4 times higher, that is not always the case, maybe the loudness is same. The 200w one just have more space to go before clip.
To active bi amp a two way system, two of 50W amps will do the same job or better than a single 200W. The preamp signal before active cross over maybe less or more depends on the amp gain.
To active bi amp a two way system, two of 50W amps will do the same job or better than a single 200W. The preamp signal before active cross over maybe less or more depends on the amp gain.
The theory of breaking up the spectrum to gain headroom or dynamics is all well and good, but in practical situations, I can't see how it gains you anything.
Take an active system that is crossed at 120Hz & 3KHz 4th order, for example. How much headroom do we gain from splitting up the spectrum into these three parts?
If we look at pink noise, the situation seems rosy. We gain about 4dB headroom in the lows, 3dB in the mids, 7dB in the highs. That helps.
But what about noise shaped more like music - brownian noise? What do we gain there?
Maybe 1/2dB in the low end, 6dB in the mids, 21dB up top. That's great for the mids and highs, but not enough to worry about in the lows.
When we look at real music signals, the story is the same or worse. For Example.
That's just the way it is. And you have to be careful of filter peaking, which can actually drive the levels UP above where the original peaks were. Do the analysis yourselves, show me where I'm wrong. I'd love to see it. Presently I just don't see the gains, except in the top end of the spectrum.
Take an active system that is crossed at 120Hz & 3KHz 4th order, for example. How much headroom do we gain from splitting up the spectrum into these three parts?
If we look at pink noise, the situation seems rosy. We gain about 4dB headroom in the lows, 3dB in the mids, 7dB in the highs. That helps.
But what about noise shaped more like music - brownian noise? What do we gain there?
Maybe 1/2dB in the low end, 6dB in the mids, 21dB up top. That's great for the mids and highs, but not enough to worry about in the lows.
When we look at real music signals, the story is the same or worse. For Example.
- Led Zeppelin Dazed and Confused: 6dB more headroom in the bass, none in the mids, 5dB in the highs.
- Beyonce - Crazy in Love: No extra room in the bass, none in the mids, 2dB in the highs.
- 1812 Overture Finale, 2dB more headroom in the bass, none in the mids, 6dB at the top.
- Donald Fagen - Morph the Cat. No extra headroom in the bass, small gains in the mids and highs.
That's just the way it is. And you have to be careful of filter peaking, which can actually drive the levels UP above where the original peaks were. Do the analysis yourselves, show me where I'm wrong. I'd love to see it. Presently I just don't see the gains, except in the top end of the spectrum.
In fact (four times the volume) is never the case!! In reality to get twice the perceived volume of a 50W amp you need a 500W amp. To get 4 times the perceived volume of a 50W amp you need a 5000W amp!!
The comment on additional headroom (for transients) before clipping is spot on.
Tony.
No, at least not in this thread. Although having used both extensively, I just say that active is easier. Therefore people tend to get better results and declare "active is better!"
But this thread is about splitting up the signal among 2 or more amplifiers via active crossovers - and what that may gain us in headroom or dynamic range.
But this thread is about splitting up the signal among 2 or more amplifiers via active crossovers - and what that may gain us in headroom or dynamic range.
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