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Old 20th August 2006, 04:53 PM   #1
2litre is offline 2litre  United States
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Default The Loudness button

Slowly but surely I'm becoming more familiar with parts of the sound system and what they do for me.

One of the things I just noticed while looking at the spec's page in the owners manual for my Sharp SM-1122 integrated amplifier is that +10 (full right) on the bass knob adds +8db to the 100hz band. +10 on the treble knob (full right) adds +8db to the 10k band. It doesn't tell me the numerical effect of the loudness button but I bet it is similar to other receivers I've looked at where, iirc, it's just like setting bass and treble to full with the flick of a switch.

I once saw the spec's on my old Pioneer and I think it's treble was farther up the range, like around 16K. Plus the better brands give attenuation slopes and loudness contour figures but, not in this manual.

Now a buddy of mine runs his systems with full bass and loudness on, giving him in effect +20db at 100hz with ported speakers. Muddy sounding AFAIC.

I tend to dink around with OB speakers and really need more attenuation in the 60hz and 30Hz bands over the 100hz band.

Can one change the frequency bands that the bass knob and loudness button affect?

R/

Jim

PS- I'm working with solid state gear for this question.
I think the logical answer would be to go active EQ but I still want to know about changing the bands where attenuation occures.
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Old 20th August 2006, 06:57 PM   #2
preiter is offline preiter  United States
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Loudness just boosts bass and treble.

It's intended for listening and low volume levels where our ears are less sensitive to bass and treble.
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Old 20th August 2006, 08:40 PM   #3
2litre is offline 2litre  United States
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Sure, I understand that.

But as I said before, if you turn both the treble and bass knobs to 100% or if you hit the loudness button it does the same thing.

I was just wondering if one could change the frequency points that the knobs or button affect.

The amps designers chose 100hz and 10Khz for thier bass and treble points. Could they just as easily choosen 50hz and 15Khz?

R/

Jim
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Old 20th August 2006, 08:49 PM   #4
poobah is offline poobah  United States
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I believe that most forms of loudness compensation affect the bass only. It's purpose is to boost the bass when listening at low volume and thus restore the balance of the music. Google Fletcher-Munson for a greater understanding of how our ears perceive sound and why loudness buttons came into being.

That being said, the choice of where to put the corner frequencies for bass boost was not arbitrary. It would have been based on the Fletcher Munson curves. That's not to say that everyones ears are the same... you may very well wish to change the frequency or the magnitude of the bass boost.

And yes... this is highly doable... post a schem.



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Old 20th August 2006, 09:54 PM   #5
AKN is online now AKN  Sweden
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A good simple explanation of loudness:
http://www.extron.com/technology/arc...nesscontrol_ts
Loudness funktion is normally dependant on volume pot position. Low volume max bass-treble boost and then gradually less boost untill max volume when we have no boost at all from loudness circuit.
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Old 20th August 2006, 09:56 PM   #6
Thunau is offline Thunau  United States
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Loudness button on decent receivers and preamps follows the Fletcher Munson curve- it scoops out the midrange centered at 3.5kHz.
A few pieces of gear have a continous loudness control where you can dial in the just right amount of compensation.
Also, in some designs turning the volume past a certain point effectively bypasses the loudness circuit.
IMO using loudness button for open baffle compensation is asking for bad results.
Just get a parametric EQ or build a simple 2 opamp circuit that is designed with the correct turnover frequency and gain for your speaker.
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Old 20th August 2006, 11:01 PM   #7
2litre is offline 2litre  United States
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Thanks all so far.

I agree, using loudness in OB is a poor way of doing what's really needed. But it is in experimenting with using the bass knob and the loudness button that started me to wondering what frequencies I was enhancing.

poobah - I have an HP PSC 1610, I'll see about getting a readable copy of the scematic posted.

Please bear in mind, I don't want to mod this amp!
I'm using it as an example because I have the schematic and the spec's available in hand. If I can get them posted then you and I will be looking at the same thing.

Every once and a while on e-Bay someone will post a copy of the owners manual for some super vintage item in thier listing.
Ilove looking at the spec pages now.
I've already noticed differences in the 'corner points' of my Sharp and the old Sansui's and, I assume, my Pioneer SX-450 and SX-780.

R/

Jim
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Old 24th August 2006, 06:43 PM   #8
2litre is offline 2litre  United States
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poobah,
I scanned the schematic, now lets see if I can post them.


[IMG]Click the image to open in full size.[/IMG]




[IMG]Click the image to open in full size.[/IMG]


R/

Jim
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Old 24th August 2006, 06:44 PM   #9
2litre is offline 2litre  United States
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OK, not readable.

Can I send you the original image file? It's a super clear and readable BMP.

R/

Jim
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Old 24th August 2006, 07:37 PM   #10
poobah is offline poobah  United States
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sure...send a PM... I'll reply... and then send the .bmp
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