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In Reply to: Re: Euphonic Compression posted by Art J. on November 11, 2002 at 20:02:03:
Hi, Art:Thanks for the link, interesting article. The euphonic compression I'm thinking of would prevent only the top 1-2% of the loudest peaks and transients from being too loud when the volume is turned up to comfortably loud levels for all but these loudest peaks.
An example: 95dB sensitivity speakers being driven by a single-ended tube amplifier with lots of headroom, no clipping, turned up to realistic SPL's, but the loudest transients peaks are too loud for comfortable listening. Is it ever permissible to limit these peaks to reduce discomfort so that the rest of the program material can be played at a higher volume setting than would be possible if the peaks were not limited / compressed?
Reverting back to the magnetic tape example, where the recording engineer in pre-digital days would set the gain to +3dB so that the highest peaks would be compressed due to tape saturation, I was wondering if there are any amplifiers or loudspeakers that have this characteristic, whereby only the very highest 1-2% SPL levels of transient peaks are compressed to permit a higher volume setting for the 98-99% of the rest of the program material.
Does anyone know if there known coefficients of compression for coil, capacitor, and resistor materials and configurations for various frequencies and SPL levels? If there are any treatises on this topic, links would be greatly appreciated.
This is a phenomenon I have observed on some high-efficiency loudspeaker prototypes, 95-97dB sensitivity, some of the peaks are too loud when the volume is turned up to realistic levels, the rest of the SPL range below these highest peaks is fine. I'm trying to "tame" the sensitivity of the speakers on the 1-2% of the loudest peak levels, I guess, so that these peaks are not too loud.
Thanks, rdb :-)
Thanks, rdb :-)
Follow Ups:
Doesn't this seem totally backwards?Consider a brass marching band. It is loud and it has transient peaks like no tomorrow. Is it painful, unpleasant? No.
I suggest that "unpleasantness" and "too loud" as perceived by listeners to stereo systems are the result of overloads -- and the resulting distortion -- somewhere in the reproduction chain. And that compression, no matter how accomplished, is at best a band-aid solution to these problems.
Regarding tape recording. IIRC, the principal consequence of recording at "+" VU meter settings is an increase in harmonic distortion. That produces the "fat sound," just as has been demonstrated with amps that produce a lot of harmonic distortion when driven hard but not to the point of clipping the waveform.
Hi, Bruce:The woofers in my prototypes are working fine without compression, it is the tweeters that are exhibiting some harshness on the loudest peaks. I don't want to change the crossover re slope or crossover point, as the current setup is fairly flat with a nice blend throughout the overlap frequency band. I would just like to limit the tweeter on the loudest 1-2% of transient peaks, I guess they are too efficient at the loudest levels relative to the woofer, and when the volume is turned up to realistic SPL's, there are occasional peaks which sound a little too loud in coming from the tweeter . . . this is what I am trying to tame. I'm looking into zener diodes per Art J's post, I'll experiment with them to see how they change the sound, if this is an acceptable solution or not . . .
I was just using the analog example to see how "deliberate" compression is being implemented these days . . . maybe there are some recording engineers out there who made the transition and figured out how to achieve the "fat" sound in a better, less distorted way . . . ??
Hey Randy, I understand more of your goals now and I may
have something to look in to. I found an old x-over circuit
that has a peak limiter. It uses 2, 16v, 1w zener diodes
connected back to back, in parrellel with the tweeter. I never
tested such a thing but its purpose is to limit high peaks, mainly
to protect the tweeter. It would make an interesting experiment.
Hi, Art:Thanks very much, this sounds like an elegant solution! I'll research these devices and try some out.
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