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Multi-Way Conventional loudspeakers with crossovers

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Old 9th November 2012, 02:12 AM   #711
puppet is offline puppet  United States
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Quote:
Originally Posted by Pano View Post
Or only if seeking an idea of high fidelity?

In reality, when you sit down in front of a pair of speakers will well engineered, well implemented crossovers and listen to some tunes - can you really tell me which is "better"? Which sounds more like music? Passive or active?
This about sums it up. Sure, there will be people that can say "yeah, I can tell the difference" ... I say, put a blindfold on and one weeks paycheck on the table. Anybody with any sense would back away :P
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Old 9th November 2012, 02:24 AM   #712
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Analog active systems emulating capacitors and inductors, and DSP systems emulating capacitors and inductors typically outperform the passive component system for equivalent radiated power. Then you add capacity to add virtually as many filters of desired gain and Q to compensate for transfer function of speaker/room. This further opens the distance between active and passive systems. Finally you add in true power of information theory which ties math and physics together, allowing full control of the system's transfer function.

My results pictured in #347 are night and day different in superior performance to any possible attempt using passive crossover. Angular resolution and stability of elements in sound image are unmistakably better. Transient performance is unmistakably better.

Regards,

Andrew

Last edited by Barleywater; 9th November 2012 at 02:40 AM. Reason: typo
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Old 9th November 2012, 02:44 AM   #713
CLS is offline CLS  Taiwan
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Originally Posted by 5th element View Post
Yes, I get that, but you still haven't answered why it is an intrinsically bad idea to connect a compression driver directly to the output of an amplifier.

....
I didn't say it's a bad idea, did I?

I mean there're quite some efforts in detail to make it work well. And I'm afraid those details are overlooked in many cases.
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Old 9th November 2012, 02:50 AM   #714
Pano is offline Pano  United States
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Originally Posted by Barleywater View Post
Angular resolution and stability of elements in sound image are unmistakably better. Transient performance is unmistakably better.
Music to my ears!!

Actually, I do find that good active crossovers have a slight advantage in the sound-stage dept. And I like that. But it's just part of the whole picture.
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Old 9th November 2012, 05:54 AM   #715
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Looking at the typical passive 2nd order tweeter crossover with L-pad from the driver, the source impedance is usually low at driver resonance, due to the shunt inductor, so voltage drive. In the operating band the source is the L-Pad, typically of the same order as the driver, so roughly not voltage or current drive but impedance matched.

Presumably impedance matched will be between the voltage and current drive distortion behaviour.
This is a pretty good combination of modes, neatly avoiding the major weakness of current drive at low frequencies.
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Old 9th November 2012, 10:34 AM   #716
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Originally Posted by CLS View Post
Hi, that quote is for a talking about the passive components between amp and drivers...

Well, I should say there're different sets of problems. Passive components help in covering up some flaws because there's some loss anyway. OTOH, they produce other problems along the way. I guess the latter is what you mentioned.



To 5th element,

Compression driver and horn combinations have more or less 110dB/w sensitivity. The best a cone driver can get is around 100. (For real bass, you need multiple drivers to get this.)

So, in a passive system consists of CD+horn and cone drivers, the best you can get is around 100db/w for the entire system (set by the lower ones). In most cases it's lower. In other words, CD+horn has to be attenuated by 10dB or more.

In a real world system, efficiency around 90 is decent already. If CD+horn joint this, the attenuation has to be increased approaching 20dB.

10~20dB difference among drivers in a speaker system is a big deal. Period.

The problems in noise floor, low level linearity of active devices, the cascade effects of them (gain structure), or even bit depth (for those dsp-based oxver)... all become obvious or intrusive in an amp-CD direct-drive combination.

----

As to whether the equipment needs fixing or not, it's actually a big question to ask, in the level of philosophy, in my way of thinking.
I'm running my Tannoys analogue active so essentially I have a 12" midwoofer and a 2" compression driver.
Never encountered any problems due to 12dB difference in efficiency.
May be it has something to do with the amps I use which have a SN ratio of 105dB. They are classAB bipolars but I doubt the treble amp ever leaves class A operation. Indeed in a phone call the amps co-designer intimated to me that it is highly unlikely that the midwoofer amp would either in a domestic environment.
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Old 9th November 2012, 10:51 AM   #717
SY is offline SY  United States
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Quote:
Originally Posted by Pano View Post
In reality, when you sit down in front of a pair of speakers with well engineered, well implemented crossovers and listen to some tunes - can you really tell me which is "better"? Which sounds more like music? Passive or active?
Didn't I say that about 700 posts ago?
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Old 9th November 2012, 01:00 PM   #718
AndrewT is offline AndrewT  Scotland
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A few have picked up on the sensitivity disparity between Cone drivers and horn loaded compression drivers.
CLS explained it nicely and it's that I want to expand on. It is also relevant to the Charles' Tannoy posts.

CLS stated that the treble to bass/Mid disparity approaches 20dB.
A typical amplifier has a gain of 26dB, using that to drive the 90dB cone Bass/Mid would be equivalent to using a gain of +6dB to drive a 110dB driver.

The easy way to avoid excessive noise and excessive attenuation of previously amplified signals is to use a buffer to drive the compression driver. If the sensitivity of the Buffer + Compression driver is not quite sufficient to match the output of the Big amplifier & Bass/Mid combination/s then add a little very low noise, very low distortion +6dB gain stage in front of the treble buffer to restore that missing 6dB (26dB-20dB) in the amp & sensitivity chain.

Now to the Tannoy. the bass is about 92/3dB and the attenuated treble is just the same at 92/3dB. Tannoy have arranged in some of their crossovers to adjust the attenuation.
But remove the crossover attenuation and you find that the 2" VC driver (equivalent to ~7/8" compression driver) has a sensitivity of ~110dB to 125dB and needing a lot of EQ for a flattish response. Add in the EQ before the Buffer and use the signal levels sent to the Bass/Mid amplifiers to drive the EQed buffer feeding the 7/8" treble compression driver.

Noise in a Buffer is inherently low, very low in comparison to a +26dB Power Amplifier. There is the added advantage of not multiplying the Source noise by that 20times factor.

2Vac into a Buffer is equivalent to 1/2W for the treble. 4Vac, with the +6dB gain stage, is 2W into the typical 110 to 120dB compression drivers. That is a loud peak for a domestic system and plenty low enough noise for the quiet moments.
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Last edited by AndrewT; 9th November 2012 at 01:05 PM.
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Old 9th November 2012, 01:17 PM   #719
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Very low distortion and compression driver don't belong in the same sentance

Regards,

Andrew
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Old 9th November 2012, 01:38 PM   #720
AndrewT is offline AndrewT  Scotland
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Why?
a 110dB compression driver with a 10mW signal is comparable in output level to a 90dB cone driver with 1W. Both will give ~90dB SPL @ 1m
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