RIAA compensation in Xover network

kivitel

Member
2013-05-03 12:07 am
This is more of a thought experiment, but has anyone heard of a loudspeaker that has built in RIAA equalization?

The RIAA eq revolves around 50hz, 500hz and 2122hz, which are all common crossover points, so it seems like it might be possible to accomplish the eq by cutting your midrange 20db and cutting your tweeter 40db. I understand that this is sort of crazy, but there may be other ways of doing it.

The frequency response tilt we normally aim for with a loudspeaker is something like 2 or 3db more in the bass than in the treble, with a smooth response in between. This is a gentle slope so we can still use the nice (hopefully) flat bandwidth in the center of our drive units. However the RIAA eq is something like 6db/octave, so you might have to find drive units which roll off naturally at around that slope and combine them in such a way as to get the RIAA eq naturally, and make the roll off the bandwidth we use.

I understand, that this is a crazy idea, but I find it interesting nonetheless. It might be possible to accomplish this by attenuating the outputs of an active three way crossover - this is a better solution in some ways because it doesn't require us to burn off 40db of the acoustic output of our tweeter or something insane like this.

In an alternate universe where the only music was vinyl, could loudspeaker drive units evolved to have tilted responses and low efficiency at high frequencies in order to make such loudspeakers possible?
 
Your alternate universe does not include radio transmission of vinyl?
The DJ's voice would sound rather muddy with a 40 dB low to high tilt..

Obviously throwing away 40 dB of HF in a speaker is a waste, but doing a 40 dB boost actively in the crossover, which normally works at line level, would be a bad choice from a signal to noise ratio.

The RIAA curve is best implemented as close to the cartridge as possible.
 
try plugging a mic into the phono input on an amp. I did this as a young teenager, and it doesnt sound good at all.
Muffled is a kind understatement, imagine your own voice, as you speak whilst wearing earplugs, with a blocked nose.
The female voice, generally a purer fundamental sound, will sound heavy in the midbass, dare I say 'chesty'.
Dolly certainly doesnt need to be chestier.
 
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dumptruck

Member
2010-05-04 5:02 pm
MN
Here you go, 25mH in series with a HiVi B4N, and done. ;)
 

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jjrenman

Member
2013-03-01 6:23 pm
"In an alternate universe where the only music was vinyl, could loudspeaker drive units evolved to have tilted responses and low efficiency at high frequencies in order to make such loudspeakers possible?"

Certainly drive units could evolve to have a tilted responce but it is highly likely that the evoulution would be to decrease the efficiency from 50hz and up. Even if they did some how figure out how to make a driver to be 20db more efficient I would rather they use that tech across the whole freq spectrum as speaker efficiency is always a benefit in speaker design.

BL basically mirrors "weltersys". The RIAA inverse curve has to be applied somewhere in your system and the easiest place to do that is when the signal is the smallest.
 
re:"I understand that this is sort of crazy"- yep,
but looking at the curve here: riaa backgrounder 1 - Introduction he says " At 50 Hz, 6 dB per octave , between 500 and 2122 Hz a flat response and after 2122 Hz the curve falls again with 6 dB per Octave" should be easily do-able with simple xover elements. Might not even need a tweeter!!!
(the inductor for the 50Hz roll off might be a bit expensive though...)
 
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Along the lines and between the lines ...
Keeping in mind the (possible) gain structure
By making the whole thing extremely purist, by using just LCR in a high
gain preamp, some TVC volume and maybe balanced all the way till power .
Did I hit the top :dunno::hypno2:
Then, by making the speaker compliant to the semi-EQed signal.
 
Hi Kivitel,

It seems quite obvious to me that such a system would quickly run into some serious problems. Lets say for example all the drivers had the same nominal sensitivity and that 10Vrms is applied to the speaker at very low audio frequencies to achieve 100dBSPL, then 1000Vrms would be needed at 20KHz to achieve the same 100dBSPL. This is simply because the RIAA curve has 40dB (equals a ratio of 100:1) attenuation from low frequencies to 20KHz !!!

Peter