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In the Forum: Horn-Loaded Speakers
In the Thread: Compression drivers and the “clean signal”.
Post Subject: Compression drivers and the “clean signal”.Posted by Romy the Cat on: 7/12/2007
We, the horn people, know what the compression drivers could do. The controlled dispersion, low distortions, low mechanical dependency, low magnetic anomalies, high efficiency, higher maximum dynamics and many-many more advance are well known. The term “compression driver” is kind of bogus as we do not rely from compression anymore but it is the only name that we have. The most remarkable part in the compression drivers is how they response to crescendos or to any increase in volume. Compression drivers have insultingly linear increase of intensity with constantly-present extra pool of dynamic headroom. It is very hard to make a good compression driver properly driven and properly used to hit a point where it stop gain volume and begin to compress. Well, where did you see a properly driven compression driver?
This is the subject that I would like to talk about: the compression drivers do not compress and do not dive into the typical “hardness” only if they driven by a “clean signal”. If the signal is “clean” then a compression driver is not stressed by anything – very seldom happen. Unfortunately the industry (and the compression drivers are unlucky, as their industry is pro audio industry) do not investigate or invest into “clean signal” but rather they make the compression drivers less sensitive to the “dirty signals”. All those JBL’s aquaplass cone treatments, increase the compression ratio to 10:1 or 20:1, making barbarian suspensions, use electromagnets (it might be controversial), employing of none-reactive cones and many other “solutions” do mask out the reactance of the drivers to the “dirty signal” but along with it they weaken the sonic characteristics of the drivers, “denobleize” the driver’s Absolute Tone ™ and reduce the driver’s transient capacity.
So, what make a signal “clean” and what would not stress the high vulnerability of a fragile, low power, good compression driver? I would not look at internal characteristics of the compression drivers: magnets, diaphragms, suspensions and many other and will look only at the external variables. Without pretending for the complicity of the answers here are my runners:
1) Bad electricity (bid subject!!!)
2) Presents in signal path of any direct or indirect phase constructors.
3) Presents, position within the chain and type of capacitors in signal path.
4) Quality of grounds
5) Having <18dB in signal’s dynamic headroom
When those 5 reasons are optimized then a compression driver has opportunity to demonstrate the max capacity of its design. So, in many cases: do not blame the compression drivers and if the fish begin to die in your pound then look up the river for the reasons that poison the pond’s water…Rgs, Romy the Cat
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