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40hz....subsonic or audible

MadcapLaughs

MadcapLaughs

Active Member
Here's a quick question for ya..

I am getting a Kenwood supreme 600 amp repaired right now. I noticed that the low filter on this amp is able to filter out at 40hz and below. What I would really like to have is a subsonic filter that filters out 20hz and below. In anyone's experience is there even audible bass to be heard below 40hz? Can I basically use the 40hz low filter as a subsonic filter without missing anything? I may request that the repair tech mod the phono stage or low filter if a 40hz is going to be chopping out some bass. Thanks.
 
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20 Hz is the commonly accepted lower limit of human hearing. There is definite sub-40Hz content in certain types of misic; I'm thinking organ or modern electronica. If you don't listen to those you won't miss anything.

I wouldn't ever engage a low filter on anything other than a turntable input; that is its intended use as a mechanical resonance at low frequencies can cause all sorts of havoc. But you won't have that with tape, CD or DAC...

Also, will your speakers even play below 40 Hz? That's another question. Many (most?) won't. If your speakers can't reproduce those low frequencies this is kind of irrelevant. At that point you might as well leave the low filter engaged all the time to save power.
 
MadcapLaughs said:
Here's a quick question for ya..

I am getting a Kenwood supreme 600 amp repaired right now. I noticed that the low filter on this amp is able to filter out at 40hz and below. What I would really like to have is a subsonic filter that filters out 20hz and below. In anyone's experience is there even audible bass to be heard below 40hz? Can I basically use the 40hz low filter as a subsonic filter without missing anything? I may request that the repair tech mod the phono stage or low filter if a 40hz is going to be chopping out some bass. Thanks.
Click to expand...
Yes bass is audible below 40hz and can easily interfere with the operation of a turntable and that is the primary reason for the cutoff point being set there. It's called a rumble filter.
 
40 Hz will cut off your audible bass...if you speakers go that low.

If you are not using a turntable, shut it off.

It's just for ultra-low rumble feedback. You might not need it even with a turntable, if your turntable is isolated.
 
Yeah there's audible bass below 40Hz. The human ear can hear down to 20Hz. Just go watch a movie with a nice low rumble and it'll be easily heard.

Whether your speakers can reproduce that low and whether the music has frequencies that low are two separate questions.
 
I've used a 30hz test tone CD when refoaming speakers and I can hear that.

EDIT: Just remembered that years ago (decades actually) some loudspeaker distributor's sales rep suggested the Genesis track Firth of Fifth to demo their speakers. I never heard that cut ever but somewhere there is supposed to be a 32hz organ pedal note.
 
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Well that seems settled. The reason I asked is that I almost exclusively listen to vinyl and my woofers on my altec speakers shake pretty bad when the phono is engaged without a subsonic filter. My turntable is isolated pretty well. My altec 890cs are rated down to 40hz so maybe I've answered my own questions at this point. I may just see if my repair tech can mod the low filter to only filter below 20hz.... Thanks for the quick responses
 
My Kenwood 700 C has a 36 hz filter which I leave on. Also has a subsonic filter which is not as effective at reducing rumble as the 36hz . I can't hear it much but have noticed a lot of woofer movement with my jbl l200's with it off when playing the tt.
 
MadcapLaughs said:
Well that seems settled. The reason I asked is that I almost exclusively listen to vinyl and my woofers on my altec speakers shake pretty bad when the phono is engaged without a subsonic filter. My turntable is isolated pretty well. My altec 890cs are rated down to 40hz so maybe I've answered my own questions at this point. I may just see if my repair tech can mod the low filter to only filter below 20hz.... Thanks for the quick responses
Click to expand...
Most subsonic filters cut off below 20Hz (maybe even lower than that), so that's an interesting design choice.
 
Here's some gratuitous visual confirmation, from the test tone above.

DSC00328.JPG

Or should I say superfluous ?

(as if I could say that) :naughty:
 
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more gratuitous...
yep, that starts at 3.75hz, with massive energy at 6hz, 10hz, 16hz, and 32hz
organ5hz.jpg.png
 
I'm probably going to ruffle some feathers, but... There are many speakers that claim to go lower than 40Hz, but they rarely tell you with how much distortion. Lots of folks like to boast about how low their speakers can go, but almost none can produce anywhere near 20Hz accurately. Your 40Hz cut-off is likely just fine unless you have a purpose-built bass monster system that moves huge volumes of air with tons and tons of power.
 
One thing i didn't see touched on.
Back in the day, consoles were a norm and all kinds of low filters were employed.
I'm not sure what you'd be gaining by employing a low filter.
I haven't noticed any interference. Even with TT as a source. I'm not sure what's to be gained
 
Sorry , must have joined our program in progress.:whip:
My turntable is on a shelf unit on s slab floor.
I know some have gone the extra yard to isolate their TTs, I think that mechanical isolation would be a better solution than filtering out low frequencies. That being said, not having an issue to overcome its easy to dismiss possible (viable ?) Solutions :D
(No after rereading, i somehow missed (forgot) the end of the opening post. I don't know, day dreaming, not paying attention.
Once more apologies :dunno:
 
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