merlin said:OK, I admit my original post may have been badly worded
I'm man enough to confess! Whilst we are on the subject of speaker design GTM, what are your thought on 2 way vs 3 way or 4 way. you appear to be saying that it's relatively easy to match drive units with OK quality crossovers. Would it not therefore make sense to use multiple drive units well within their capabilities to prevent any THD caused by cone breakup? I sometimes wonder why this approach seems so unpopular with audiophiles but is the mainstay of many monitors and professional products.
How complicated the cross-over has to be is dependant on the way in which the drive unit behaves near/at/past the chosen cross over point. This is one area in which cone material becomes significant. The advantage of doped paper cones is that they have relatively high self damping properties and so tend to roll off quite smoothly at the top end of their usable frequency range. Generally this makes for easier integration with simpler cross-overs. The disadvantage is that you generally have to put up with higher THD/intermodulation components, (relatively speaking - as good ones are still pretty good in this area). Alternatively you can use metal cones as they are more linear and have lower distortion figures in general. However, they ring like ba(*&%(ds and have very poor cone break up characteristics leading to a very jagged and spikey response at the top end of the band. To prevent this part of the output to be audiable much higher order cross overs need to be used with all the potential phase problems which they incur. Hence the arrival of carbon/kevlar/composite (including paper composites) material use, which tread the middle ground between paper and most widely used metals.
With respect to the amount of drive units, well using more makes for a more complicated speaker with more potential to mess up the sound. Integration of the drive units is harder electrically as well as the physical constraints and acoustic implications of using multiple drive units has on the way the final speaker behaves. For example there is the issue of acoustic centre positioning for each drive unit and the potential smearing in the time domain due to physical distance between individual units and seating position etc. On the flip side, using less has the drawback of finding wide enough bandwidth units to conver the whole frequency range. Most drive units start to loose phase coherence at the extremes of their bandwidth, particularly off axis. Of axis response is more important than just the actual level involved, there are phase issues to contend with. All of these factors affect the way the speaker sounds when you move around. I'm sure we've all heard speakers that sound great in one spot only to start sounding "off" as you stand up, move from side to side, and im not talking about their ability to image here I mean from a basic frequency response/phase standpoint.
GTM
