[andyr]

I have found that tweakers modify everything to the final output stage but rarely check the xovers for system synergy.

Laurie

Hi Laurie,

Can you elecidate as to what you mean by this statement?  What exactly do you mean by "system synergy" wrt Xovers? 

Thanks,

Andy

[Tliner]

Hi Andy,

I use the word synergy to mean that the "total" system is working in harmony from the power point to the listeners ears. That is the nirvana we are all chasing.

I have built speakers that sound absolutely marvellous on one amp and so-so on another of similar specs.

The timing of the signal output of some amps appears not to be constant. That is the phasing of a sound may be distorted by the amp. For instance the impact of a midrange note which is say both sides of the speakers xo point can be slightly out of phase at the listeners ears, perceived to be as a note with little slam and impact even lifeless. The high hZ part of the note can be emitted from the tweeter sooner (up to 10 milli seconds in front of the lower driver) than the lower part of the note to the mid/woofer. I have found that the Lifeforce amps and the Soraya amps to be particularly good in the "synergy" of the signals. That is why the slam of percussion instruments and detail stands out with these amps. So much so, that it took a long time to "time/tune" the new VSonic speakers to the Aksa amps so that the group delay and the related phasing are as closet to optimum as component tolerances allow. Now that balancing the speakers to an excellent amp allows the speakers to sound good on almost any reasonable amp.

I hope that makes one realize that if we are to strive for the ultimate audio system the system has to be treated as a whole. Each part of the system that is modified in isolation can adversely affect the system some where else. Or one might be lucky and crack it!

Cheers,

Laurie 

[AKSA]

Andy,

This bears out the fact, exactly as Laurie explains it, that the speakers are an extension of the output stage, and the output stage is in fact crucial to the operation of the voltage amplifier stage on a feedback amplifier.  They must all work together, and if phase shifts are abrupt, or too large, first imaging and ultimately resolution will be affected.

One of the most sensitive areas is the crossover point, around 2600 Hz on the VSonics.  There should be virtually no difference in phase shift between the drivers, otherwise there will be a lack of image accuracy and resolution at this frequency.  You will hear the crossover frequency, IOW.

I have already mentioned the importance of making the speaker/crossover as unreactive as possible, so as not to present reactive, out of phase reflections back to the amplifier, thus upsetting the feedback loop.  This too is critical and comes back largely to the Zobels which null the voice coil inductance.

Cheers,

Hugh

[andyr]

Hi Laurie & Hugh,

Thanks for taking the time to post ... I can see where you're coming from but I'm afraid there are a coupla issues which haven't sorted themselves out in my grey matter 

Laurie, you said "The high hZ part of the note can be emitted from the tweeter sooner (up to 10 milliseconds in front of the lower driver) than the lower part of the note to the mid/woofer."  What causes this?

Would the amp, itself, have some strange phase shift around the particular frequency of the XO which causes this delay ... no matter what drivers are connected to it?  (You did say there are "good-sounding amps" and "not so good sounding" amps!  )

Or is it the intrinsic inductance shift of the (cone) drivers which is imposing this phase shift on the amp (so if you neutralise this with Zobels, the amp won't exhibit the "forward" tweeter signal)? 

Or are the LP/HP filters doing this to the amp?

Regards,

Andy