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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: Tried something similar posted by BobM on August 1, 2002 at 07:50:07:
Interesting scenario. I've experienced the exact same. One set of speakers that I own use a 19mm silk dome tweeter. Now, I am not generally a big fan of fabric domes, because they have a tendency to sound too "restrained." I am not totally sure why. I have studied and compared the response graphs for silk and metal domes. I don't see big differences EXCEPT in the high treble, where most silk domes appear to cut out early. They begin rolling off at 10 kHz and don't produce much extension above 16 kHz. This does not explain their "restrained" sound though. The graphs must not be showing what my ears detect, which is a difference in sensitivity and loudness (between silk and metal domes). Metal domes (generally) sound more sensitive and are capable of a louder treble.In my experimentation with felting, I have noticed that felt lowers the reflectivity of the baffle. Most speaker designers use the baffle like the reflective material behind a flashlight bulb, to increase the amplitude (brightness) of the tweeter's response and to focus that response in a forward direction. Therefore, the designers will often choose a highly reflective baffle (that functions as a wave-guide).
Felting lowers the reflectivity of the baffle and therefore also lowers the sensitivity of the tweeter. Very sensitive metal domes will not suffer too much of a loss, but less sensitive fabric domes (without a reflective baffle to amplify their output) will experience a significant drop in the amplitude of the tweeter's output.
So, the effects of felting depend on how the tweeter has been voiced vis a vis the baffle, but it stands to reason that a restrained sounding fabric-dome tweeter will sound even more restrained when it no longer has "boundary boost" from the baffle to assist its sensitivity. Felting may not be an option in such circumstances (unless the dome's sensitivity can be adjusted in some other way - perhaps by adjusting the crossover), which is unfortunate, because preventing diffraction effects using felt has other benefits (besides allowing consumers control over tweeter sensitivity) such as more stable imaging and a cleaner, less hashy treble sound.
It's worth spending some time experimenting with different amounts of felt and different baffle placement because each tweeter/baffle system has been uniquely voiced. Each system will have a slighty different sensitivity (to any other). Felting will alter the tweeter's sensitivity to one degree or another. Experimentation will provide just the right amount of fine-tuning to improve the quality of the tweeter's performance without losing too much sensitivity.
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Follow Ups
- Tweeter sensitivity - layman 13:37:19 08/01/02 (2)
- Here is how I solved the problem - layman 14:11:03 08/01/02 (1)
- Excellent posts again! - Sean H 21:03:49 08/01/02 (0)
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