Loudness experiences?

[Skorpio]

I have found out that for best performance, I have to correct bass level according to sound level on my system.

On the other hand, this is very unpractical an non-optimal. I could use an normal loudness control, but I don't find them working good!

Loking on the sensitivity curves for the ears tells that a level dependent bass eq is needed, but not eq in the rest of the spectrum. I think it is why I dont like ordanary loudness controls.

There are two basic things to look for:

1. Automatic bass correction with volume setting
2. Level control, to fit to system

The first could be a normal loudness potentiometer with only bass correction
The second could be a second volumecontrol

Anybody know about these problems and have some circuits?

[phase_accurate]

The easiest solution is to use a normal pot and simply listen at the intended SPL.
There is only one correct listening level for each recording !

Regards

Charles

[Upupa Epops]

Independent volume control with loudness and separate " gain " control had Yamaha amps - try to find some manual...

[jez]

B&O once made (early '70's, dont know about later on) amps which had "loudness" built in to vol control circuitry, IE as you turned down the volume it applied loudness compensation. It could not be defeated so was pretty objectionable!

[forr]

I urge you to read "Loudness compensation use and abuse" by Holman and Kampman, and to have a look on the Apt Holman preamp. It's of the greatest help on the subject I am aware.

[Skorpio]

Originally posted by phase_accurate
The easiest solution is to use a normal pot and simply listen at the intended SPL.
There is only one correct listening level for each recording !

Regards

Charles

I agree completely....there is only one correct level at reproduction of a recording.

But my idea was to be able to use more levels but adjusting the eq....

I think a major reason for not listening at lower levels, is the thin sound.

[bzfcocon]

Originally posted by forr
I urge you to read "Loudness compensation use and abuse" by Holman and Kampman, and to have a look on the Apt Holman preamp. It's of the greatest help on the subject I am aware.

Is there any related material available online ? Even schematics ? Because I'm not very sure if I can get that book. It's a book, right ?

I agree that there is only one correct level, but some of us are sometimes forced to listen at low level and I too find typical loudness circuits not satisfying.

[drago]

Here's the circuit for loudness control, all McIntosh's from the old days equipted with this variable loudness control. Please notice the connection of the pot.

[drago]

The complete circuit is here.

[CharleyW]

The Heathkit AP-1800 preamp (ca. 1979) was extremely full-featured - seperate bass and treble for left and right, variable turnover, bunch of filters, etc.

Although it didn't sound all that good, it did have a variable loudness circuit (separate pot) with an active circuit. The circuit description did include a reference to "newer" curves than the Fletcher-Munson equal loudness curves (the ones that made everyone believe that only bass compensation was required).