Why are we now talking about computers?!
I know I went off a bit tangentially as well from the OP but my point was not regarding the accuracy of DSP or analogue active crossovers or the computer analysis of performance although this does raise interesting issues.
My work with ATC drivers for my own speakers was in the late 80's. I had the pleasure of visiting the ATC factory and meeting the designer of the ATC drivers back in the late 70's when they were fledglings. I understand the dome has been under continuous development probably ever since!!
Because it is not about how flat you can get it by measurement and eq or prediction in software or RTA or gated RTA or anything else you care to mention. Mechanics plays an important role. You can flatten a response all you like but if the dome resonance is actually causing problems in terms of an amplifier's ability to damp oscillation or instability, it doesn't matter how flat it looks with response correction.
Removing the dome resonance with a passive RCL ensures that you can drive the dome pretty much to it's free air resonance. Traditionally it was always considered that you should cross a driver over at least two octaves from it's resonance..this of course would make the dome pretty useless! An RCL should or was often employed with dome tweeters, but fluid coil damping generally got around the problem to a large extent.
Listening tests with the RCL revealed a more natural midrange that now blended to create a cohesive three dimensional sound stage no longer showing up a colouration and slight honk in the lower mid particulary effecting male vocal. Listening with ears and not a computer prediction!!
I was even able to create a full blown 4th order passive (final response) 3 way network!! OK, the component cost was astronomical and it just fitted a 4u high rack case!
But it was the 80's and the ATC outboard active crossover was 'orrible as it sat there and hissed at you..plus of course without the RCL on the dome it did nothing to combat the resonance/damping issue and nor of course did it have EQ, because as pointed out some shelving was necessary and fixed active crossover points don't do that!
For the active set up they considered their market to be pro who would expect to have to EQ the system anyway?
And I only had one £4000 Threshold Stasis (still do!). It was clearly obvious to all that listened that the Threshold/Passive combination sounded like music and the analogue active + three ok stereo power amps (Yamaha P series) sounded artificial and entirely less rewarding. The current owner of the passive set still has a smile on his face some 15 years after buying them from me. Such is the load and correct tuning that he is able to drive the system with one Quad 405 and I can concur that the sound is just open, detailed relaxed and accurate.
It's what it is all about, isn't it?
Further proof of the low efficiency dome issue was was that the high efficiency dome reduced this problem substantially by having a much more powerful magnet assembly. Looking at their original plots the dome rolled off smoothly in response through resonance, a sign of optimised components used in the manufacture and very much one of the black arts of actual driver design. Coil weight, flux, amount of damping fluid on the fabric dome, the cross section of the dome material, dome weight are just a few of the criteria.
These days it is true to some extent that managing a loudspeaker in DSP is a good method but you must take into account you are still relying on an A/D unless you have digital in, and a D/A on the way out thus not enabling you to use a "boutique" quality D/A should you choose. You are stuck with the D/A converters in the unit.
Most loudspeaker management systems are designed to be implemented in live or location set up for which they are superb, but it negates your ability to go "high end" and select a separate D/A converter for each section driven...Benchmark, Sonifex, Apogee, RME, Mutec and the humble but superb Cambridge DAC Magic to name a few.
Only the top drawer DBX loudspeaker managers have the ability to go digital out per channel..there may be others but I am not aware of them?
Incidentally, whilst we are on the subject I have to confess to being one of the first to introduce a studio monitor loudspeaker which was managed digitally. It was the Omen Ra 1812 and those wishing to read about it may like to find the Hugh RobJohns review in "Line Up", Aug/Sep 2004..there is a whole lot more to loudspeaker design then what a computer can tell you!! Suffice it to say, with enormous pride, my design was very favourably compared to ATC, PMC and Genelec, Good company to keep I think.
Sadly the company I designed for did nothing to actually sell product so it has disappeared into history! But time has not stood still and I have continued to research and create product for my own operation..this time with a difference. We have moved on from just stand alone designs and now re-appraised some of the problems of the "hot seat" and how to create even response throughout different listening areas..those interested in cardioid, asymmetric dipoles, run times and predicted..(yes, even me!) polar response may wish to "watch this space...."!
As a final aside..our review pair of 1812s submitted to Hugh RobJohns was delivered with two DSP loudspeaker management systems..the BSS366T Omnidrive and the Behringer Ultracurve at 1/10th of the cost. The two units were set up identically. It would be churlish to suggest you go and read the review to find out his comments regarding the subjective quality of the two units, so I will put you out of your misery. With this set up, the Behringer won!!
All is not what it should be in the world of sound reproduction..whatever the computer may tell you!
