I've seen some interesting threads around here on removing the dust cap on full range drivers and replacing with a 'phase plug' (or at least, a post filling the void in the middle of the voice coil that might or might not fit the strict definition of the term).
A couple of reasons cited for doing this are reduced power compression and increased efficiency. I haven't been able to find any citations or measured experiments on that though. Any out there you can point me to?
A couple of reasons cited for doing this are reduced power compression and increased efficiency. I haven't been able to find any citations or measured experiments on that though. Any out there you can point me to?
In theory taking the dustcap off reduces the Sd? so efficiency should decrease.
Looking thru my measures of FE206E/206En/207 with measures before & then immediately after with caps removed that the efficiency was as likely to increase as decrease. Differences were really small and, i suspect, within the error bars of measurements.
dave
Looking thru my measures of FE206E/206En/207 with measures before & then immediately after with caps removed that the efficiency was as likely to increase as decrease. Differences were really small and, i suspect, within the error bars of measurements.
dave
That right, though moving mass decreases, which would increase efficiency. Probably neither is significant anyway.
Thanks for the tip. Doesn't look like a huge change.
http://www.eton-gmbh.com/fileadmin/...-Hifi/Arcosia/Datenblaetter/Arcosia_7-308.pdf
http://www.eton-gmbh.com/fileadmin/...-Hifi/Arcosia/Datenblaetter/Arcosia_7-208.pdf
http://www.eton-gmbh.com/fileadmin/...-Hifi/Arcosia/Datenblaetter/Arcosia_7-308.pdf
http://www.eton-gmbh.com/fileadmin/...-Hifi/Arcosia/Datenblaetter/Arcosia_7-208.pdf
I just found a paper indicating that the drop in output due to power compression from voice coil and magnet heating could be on the order of 4-6dB in PA speakers under heavy load, with some details about what happens on the way there.
Button, D. J. (1992). Heat dissipation and power compression in loudspeakers. Journal of the Audio Engineering Society, 40(1/2), 32-41.
I still don't know how much more effective a phase plug would be at cooling than a vented pole piece, but maybe it's a moot point anyway since I'm not running my speakers at these levels.
Button, D. J. (1992). Heat dissipation and power compression in loudspeakers. Journal of the Audio Engineering Society, 40(1/2), 32-41.
I still don't know how much more effective a phase plug would be at cooling than a vented pole piece, but maybe it's a moot point anyway since I'm not running my speakers at these levels.
Maybe there is also some benefit in the high frequency behaviour when, for example, you want to run one full range. I wouldn't say that pulling dust caps off at random is a good thing as I have made some mistakes doing that, but some people such as Planet10 seem to have looked in to this much deeper than that.
That's typical when you're dumping 1KW+ into a single driver.
Shouldn't be happening in HiFi.
Chris
Removal of the dustcap and filling the space squashes the oil can resonance of the air trapped in the VC cavity below the dustcap. We have been, at least mostly, been able to eliminate this with the extra coatings we put on the cones & dustcap when enabling them. The extra benefit of disturbing standing waves across a whizzer cone still have us putting phase plugs in the larger whizzer cone drivers. This also tends to improve dispersion. With the B200, which has no whizzer cone, adding phase plugs transforms the driver, before having a laser like HF and a painful rising response on axiz. Phase plugs dramatically increase dispersion and do alot to flatten the FR.
dave
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.