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Old 21st December 2001, 11:00 PM   #1
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Join Date: Oct 2001
Location: Sydney, Australia
Default RIAA Equalisation?!

Good day, Gentlemen

I had a very interesting experience last night, when listening to my new full range speakers. I have just brought my full-range speakers online and was have a listening, tweaking session and I was very disappointed with the bass response. There just was none. I knew from previous testing that I should have a good response down to at least 70 - 60Hz, and should be able to get another half octave after more tweaking of the transmission line. compensating for diffraction loss and etc. But there was nothing much below 150Hz, but above that the music was clean and unbelievable, actually very scary listening. In one quiet piano passage, I actually could hear the fingers of the pianist hit the ivory!! Unreal!

I normally listen to vinyl, but for this particular listening session I had grabbed some CDís. My LP to CD ratio is about 10:1. Well, I do have several albums that are on both CD and LP, so I grabbed my LP's and Eureka! I had good clean response to 55Hz. The bottom end of the keyboard was strong right done to the bottom. I picked several other LP's(I actually had about a 4 hour listening session) and the result was the same. Switched back to CD's and again the bass was anaemic. Mystery?!

I then remembered reading an article some months ago that made mention of RIAA Equalisation. As we all know, LP's were all cut with a bass slope to reduce rumble and etc, and then the phono stage inverts this attenuation in its equalisation section to restore the bass to its proper level. The article then stated that the RIAA method has never been dropped and CD's were burned with the same bass roll off, but since the signal is run directly to the gain stage, there is no inverting of this roll-off. I am not a sound tech, but after last nights listening, I must admit that there was a obvious difference between the same cut on CD and LP.

I know that these speakers love vinyl and spit CD's right out at you. Unbelievable, recordings that I had thought good, are now almost unlistenable. But I can tell you that I have never heard piano solos, jazz, James Galway, and vocals like these speakers produce.

So maybe those of you who are a bit more in the know about sound engineering can clear up this anomaly a bit.

Surf, Sun & Sound
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Old 22nd December 2001, 01:58 AM   #2
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Join Date: Sep 2001
Location: Fairbanks, Alaska
Default No Bass Blues

Surf, Sun & Sound,

No bass from a CD. This is a strange problem since CD's can have a response down to DC. I assume that you have tried a number of CD's of various brands and they all have no bass. And that all the CD's were recorded by a major studios and not copies of analog recordings re-recorded to CD's by an individual.

If all your CD's are lacking on the low end then I would suspect a problem with the CD unit or perhaps its signal routing. The RIAA curve does not enter into the picture when using CD's.

Prehaps you can list your CD numbers to see if others have noticed the same problem with those particular CD's.

John Fassotte
Alaskan Audio
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Old 22nd December 2001, 03:14 AM   #3
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Default Bass Blue

John,

I suppose after rereading my post, I made it sound as though there was a brick wall at 150Hz and nothing below with CD's. Well, after listening again this morning for several hours, let me clarify, there is definitely less bass on the CD's but the diference is about 3- 4db at the most.

I used those dreaded tone controls to equalise the difference and what it amounted to is that I had to boost the bass from 150hz+- and below between 2-4db to bring it back to the same level as it is with the LP's. So it is not a significant difference, but enough to annoy me.

Here is a thought, is it possible that because the LP does not have the bandwidth of a CD, that in fact what I am hearing is slightly deeper bass extension(which is rolled off due the characteritics of the speakers) and thus my brain is telling me that the bass is rolled off a bit. I do know that an LP has a tendency to compress the audible bandwidth slightly, ever so, so you think you are hearing more music. I am getting a bit out of my field here, but I can tell a slight difference for whatever reason between the CD and LP. I thought maybe there was some validity to the RIAA theory.

Surf, Sun & Sound
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Old 22nd December 2001, 04:05 AM   #4
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Sx3,
We are to assume that your phono stage and CD are the same ones you've been using all along, correct?

Grey
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Old 22nd December 2001, 07:46 AM   #5
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Default Bass Blues

Grey,

Yes, I have changed nothing except the speakers. Interesting, that this is the third set of speakers in this system, but I have never heard this difference before. Although the previous set were both sealed speakers and this set is a transmission line.

Not a big deal, just curious if anyone else has had this happen to them.

Surf, Sun & Sound
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Old 22nd December 2001, 04:44 PM   #6
jam is offline jam  United States
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Maybe the low frequency resonance of your arm cartridge combiation is exciting some resonance in your speakers?

jam
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