Another example, on the subject of compression, in this case "ringing" may rob the midrange of dynamic range Stereophile Review. Ringing also reduces the contrast or sharpness in transients which is why Quad 57's are cherished (with its nice waterfall) for being "fast" and beautifully detailed even if they are limited dynamically. |
Acoustat6, I'm unwilling to dive for the volume control once I have established the right volume level otherwise. With most systems, Das Reingold forces you to otherwise keep the volume at a level that is unrealistically low. Shadorne's comments about compression are right on. FWIW, Classic Audio Reproductions has been using and are developing field coil drivers (at the recent AudioKarma show they demo'd the speaker with FC woofers and midrange). Otherwise, one of the advantages of Alnico is that fact that the magnetic structure can be focused on the gap; saturation is easy enough and one of the measures of the designer's mettle is 'is it still saturated at 105 or 110db?' With heating and the like, that's a bit of a trick! BTW in an average room where you are 8-10 feet from the speaker, a speaker with 89 db 1watt/1meter efficiency could need 250 to 500 watts to make 110db (how dead the room is will play a role too so this power requirement could be a lot higher, OTOH a lively room may well prevent one from being able to hit lifelike peaks without discomfort). You really don't want the amp to be clipping at it highest volume, so its easy to see how hard it is to work with inefficient speakers. If you happen to prefer tubes, 200 watts is a practical upper limit before the term 'gold-plated decibels' really starts to hit home! Once you have heard how important this is, it gets hard to take inefficiency seriously. |
Atmasphere said: "BTW in an average room where you are 8-10 feet from the speaker, a speaker with 89 db 1watt/1meter efficiency could need 250 to 500 watts to make 110db (how dead the room is will play a role too so this power requirement could be a lot higher, OTOH a lively room may well prevent one from being able to hit lifelike peaks without discomfort). You really don't want the amp to be clipping at it highest volume, so its easy to see how hard it is to work with inefficient speakers. If you happen to prefer tubes, 200 watts is a practical upper limit before the term 'gold-plated decibels' really starts to hit home!" Perhaps this explains my gravitation to SS for speakrs. My Rowland Continuum 500 gives me 1000 watts into my speakers' 4 ohm load and I sit only about 8' to 10' away, with a 91dB sensitivity for the Vienna Acoustics. When listening seriously I generally run the volume at a level that results in 85 to 87dB averages, with peaks in the 90s on pop and jazz and in the 105-110dB range on classical. Those peaks seldom last very long in the music that I listen to. Dave |
Shadorne, that JBL paper where they compared the thermal compression of different woofers and the Alnico magnet TAD compressed by about 7 dB within a few seconds is grossly misleading. I hate to say this about the JBL guys, but they deliberately chose test conditions that made their competition look very very bad. Alnico has less loss of magnetic flux with heating than ceramic does, up until the point that you overheat it. Then, Alnico loses flux permanently; it becomes partially de-magnetized, whereas a ceramic magnet will regain its flux once it cools off. What JBL did was to overheat the Alnico magnet. They damaged it, and I doubt that was accidental. That test is not an accurate depiction of how an Alnico magnet performs when it is not abused. Duke |
Duke, Thanks - I figured that might be the case - the dirty rotten cheats ;-) (all is fair in marketing!) It was however hard to find links to solid examples that show that compression really is a big issue. Perhaps I chose the wrong example. It would be great if there were more examples about this poorly understood issue but I don't think speaker manufacturers like to raise these issues too often. I understand that if you sell several drivers - some pro and some lower cost then it might be at cross purposes to emphasize how your lower cost drivers might be compressing quite severely. (You just killed sales on your most popular mass produced item in order to try to sell a very few high priced items!!!) |
