Tony, that statement is factually incorrect. It's an open forum, not heavily moderated (like this one), and there for all AVI users and enquirers.
You might have your opinion, but other people will have theirs too.
You ask for facts, and Cav said this
" As to performance, that can either be on measurement or subjective preference. I doubt AVI would win on measurement."
I replied
"On the contrary, whist subjective assessments can result from often quirky personal preferences, I think that objective assessment based on measurements would show AVI to be a clear winner, if only on distortion alone."
Here are the true facts and specifications published by AVI, by Martin Grindrod, AVI's designer and Engineering Director.
Grindrod wrote:
There seem to be some posters that have real trouble accepting the claims made by Ashley I thought I would just post some facts since I actually made the measurements and did the analysis [AVI ADM9]:
Regarding distortion in crossovers:
I measured a typical 2 Way 2nd order LR crossover designed for a crossover frequency of 3.5kHz using a number of different inductors, using the drive units as loads at 10W the electrical harmonic distortion was typically 1% (-40db) for the iron cored inductor samples and 3% (-30dB)for the ferrite cored samples which was a suprise! Measurement frequencies were 1 octave either side of the crossover frequency. I did not use an aircored sample because it was highly resistive (0.8ohms) compared to the drive unit impedance which in itself introduces response anamolies of the order of 10% (-20db) which , since the drive unit signal is in error compared to the input in the passband of the filters,it can legitimately be called distortion. In practice response anomolies are measured with all the inductor types due to their resistance. (This is particularily noticable in 3 way designs where the lower crossover point requires large values of inductance)
By contrast the active filters used in the ADM9s have distortion typically -96dB at the frequencies used above, this means that the active filters in the ADM9s are very much more than 1000 better than the passive crossover.
The mid-band distortion of the ADM9 amplifiers is typically 96dB so even including the amplifier the distortion in the voltage received at the drive units will be better than 50dB lower than a perfect amplifier driving a passive crossover.
Regarding damping factor:
The amplifiers in the ADM9 are optimised for the loads that they see, the output impedance is typically 1mohm mid band, there are two short cables (9) direct to the drive units.
Now consider a typical passive system, firstly, in order to ensure the amplifier is stable into a wide range of loads it will have some form of output coupling, either a damped inductor or series resistor. Also the typical output imedance is much higher than the ADM9 amplifier since the ADM9 circuit produces an exceptionally low output impedance. Typically the amplifier alone may have an output impedance from 50mohms to 0.5ohms in some cases. Add to that the connector and cable losses, typically 50mohms for 3m of 2.5mm2 cable, and then the crossover losses which may typically be 0.3ohms at DC then the source impedance seen by the bass driver will typically be 0.4ohms to 0.9ohms compared to the couple of milliohms seen by the bass driver in the ADM9.
An important point to make is that in the passive system from a decade either side of the crossover (i.e., 350Hz for the bass driver in the example above) the source impedance rises significantly as the crossover frequency is approached. It is a common mistake to visualise things happening close in around the crossover frequency but in practice things start happening at least a decade away!
I hope this goes some way towards showing that the claims made, not just ADM9s but active speakers in general, are real and factual, correctly designed there are huge advantages in terms of drive unit control and distortion, all this is measurable and is not just an opinion
I hope this helps in putting this one to bed!
Martin
JC
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