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Subwoofer frequency question

GUEST,Jon 15 Feb 11 - 05:29 AM
Richard Bridge 15 Feb 11 - 05:43 AM
treewind 15 Feb 11 - 06:15 AM
Mr Red 15 Feb 11 - 06:18 AM
GUEST,Jon 15 Feb 11 - 06:30 AM
Richard Bridge 15 Feb 11 - 07:07 AM
GUEST,Jon 15 Feb 11 - 07:32 AM
Bernard 15 Feb 11 - 07:48 AM
Leadfingers 15 Feb 11 - 08:04 AM
pdq 15 Feb 11 - 08:37 AM
Richard Bridge 15 Feb 11 - 01:21 PM
frogprince 15 Feb 11 - 01:36 PM
GUEST,punkfolkrocker 15 Feb 11 - 02:02 PM
Richard Bridge 15 Feb 11 - 05:01 PM
GUEST,Jon 15 Feb 11 - 05:50 PM
The Fooles Troupe 16 Feb 11 - 06:26 AM
GUEST,TIA 16 Feb 11 - 06:34 AM
Bernard 16 Feb 11 - 06:55 AM
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Subject: Subwoofer frequency question
From: GUEST,Jon
Date: 15 Feb 11 - 05:29 AM

PA amps seem to quote 20hz - 20Khz
Our Samson Rubicon 18s Active Sub goes down to 20hz +/-3db
The lowest note on a piano is 27.5hz

But if I look at passive sub woofers, typical lowest frequencies quoted are around 40hz - 50hz.

I'm sure the makers and users of professional audio equipment know what they are doing but I'm curious as to why the (I suppose) best range seems to stop at the low end at what in some cases is an octave above the lowest piano note.


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Subject: RE: Subwoofer frequency question
From: Richard Bridge
Date: 15 Feb 11 - 05:43 AM

When I build subs I aim to get an audible response down (by porting) to about 20Hz. Since this is often well below f0 (the fundamental resonant frequency) of the driver I do have a tendency to knock the endstops off.


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Subject: RE: Subwoofer frequency question
From: treewind
Date: 15 Feb 11 - 06:15 AM

I'd guess an active sub can tailor its frequency response in the electronics. It's quite possible that the power amplifier reaches full power in the 20-30Hz range at levels far lower than would result in full power at higher frequencies. In other words that spec. may only be valid at moderate sound levels.

Also consider whether you really need 20Hz. The fundamental of the lowest note of a piano may be 27Hz, but most of the sound is in the harmonics and overtones up to 500Hz and higher. If you reproduced that piano note though a system that cut off below 50Hz, you'd hardly notice any difference. Double basses, bass guitars and big pipe organs might produce significant energy below 50Hz, but for most real music the majority of sound amplified or recorded in that region is wind noise, air conditioning and floor rumble and best filtered out.

Most of the value of a sub is to provide clean power in the 50-150Hz region where there is significant musical sound energy, taking a huge load off your main speakers so they can deliver much higher power without distortion.


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Subject: RE: Subwoofer frequency question
From: Mr Red
Date: 15 Feb 11 - 06:18 AM

When I were at Uni the received wisdom was that human hearing is pretty poor at 20Hz. What you hear is the harmonics more than the fundamental, but the mind is pretty good at compensating. The lowest note on really swanky church organs is about 15 Hz.
At these frequencies you feel the vibrations more than hear them. Through the furniture and floor as much as the air.

My usual response to the attention to such detail is to ask how close the road and the neighbours are. Noise leaking from external sources make a mockery of the fine detail.

If you are over 21 then 20 kHz is impossible unless you chose your parents well and refrained from rock concerts and headphones playing same. If you are over 50 I would be amazed if you could hear anything above 10kHz - normal human chronological physiology before we consider your listening lifestyle precludes any avoidance of hearing deterioration. Loud passtimes, cars bikes, workplaces all insult the ear and it is cumulative and largely irreversable. But the good news is your 20Hz is unaffected.


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Subject: RE: Subwoofer frequency question
From: GUEST,Jon
Date: 15 Feb 11 - 06:30 AM

I never knew that about a piano!

And thanks for the explanation of how things work in practice.


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Subject: RE: Subwoofer frequency question
From: Richard Bridge
Date: 15 Feb 11 - 07:07 AM

I must go for a re-test. When my late wife was nagging me about my hearing (I seemed to have acquired a mental "filter" button) let's see, about 10 year ago so I was 52, the hospital said my hearing was normal, and I asked "do you mean "normal for my age" and they replied "no, normal".

I do however sometimes have a slight whistle in my right ear (usually presages an infection) and spent most of my life abusing my hearing.


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Subject: RE: Subwoofer frequency question
From: GUEST,Jon
Date: 15 Feb 11 - 07:32 AM

I'm 50. Just tried one here

I can hear 30hz-12Khz. I'm unsure about the 16Khz one. If I listen carefully at 0db, I seem to hear what I might call an odd sort of silence rather than a tone.

Of course these things are limited to the system playing the sound, as well as my hearing.


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Subject: RE: Subwoofer frequency question
From: Bernard
Date: 15 Feb 11 - 07:48 AM

It is commonly accepted that musicians are not as critical of hifi systems as their non-musician audiophile counterparts. This is because a musician tends to use audio more as a memory-jogger rather than actually listening to the sound being produced.

Perhaps that's a sweeping statement that only has a little truth in it, but our ears (and receptors in the brain) do have abilities that cannot be mimicked even by the best of microphones.

We can 'focus' (or as Richard put it, mentally filter!) on the sounds we want to hear, and to a greater or lesser extent, depending upon distractions, ignore the sounds we do not wish to hear.

That said, next door's dog barking at three in the morning is a different matter!

I suffer with quite serious tinnitus (Richard's 'slight whistle' in my case his a constant loud hiss, almost white noise), but have learned to deal with it by 'switching off' my ears. Unfortunately, it means people think I'm ignoring them as they know I'm not deaf...

As for bass frequencies, I can only echo what others have already said - what you think you hear isn't necessarily what you actually hear!


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Subject: RE: Subwoofer frequency question
From: Leadfingers
Date: 15 Feb 11 - 08:04 AM

When I was a Sprog Radio Fitter we tried the Frequency Test - At seventeen I coukd hear from about 20 Hz to well over 20 KHz
Bet I havent got that range now
Very few people over twenty can hear much below 30Hz , or above 18KHz , so its the Harmonics that make the sound good


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Subject: RE: Subwoofer frequency question
From: pdq
Date: 15 Feb 11 - 08:37 AM

Some of the finest records ever were done in the late 1950s on Ampex tube (valve) recorders with a sharp cutoff over 15,000 and under 30 cycles. They can have growling bass and sparkling highs. Most importantly, they get the "middle" right.

If FM radio sounds OK, remember that it has a low frequency cutoff of 50 cycles.

The points made by treewind are quite important. The lowest notes on a piano have very little fundamental and a great deal of harmonics. Any attempt to get the very lowest notes up in volume will increase non-musical artifacts and steal power from the amplifier, potentially damaging the speakers too.


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Subject: RE: Subwoofer frequency question
From: Richard Bridge
Date: 15 Feb 11 - 01:21 PM

Bigger speakers...


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Subject: RE: Subwoofer frequency question
From: frogprince
Date: 15 Feb 11 - 01:36 PM

If you all are concerned with acoustic folk, you must be gearing up to play Dave VanRonk records. : )


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Subject: RE: Subwoofer frequency question
From: GUEST,punkfolkrocker
Date: 15 Feb 11 - 02:02 PM

as an aside...

.. tricked out pimped car sound systems are wasted on boyracers
with their safe conformist taste in bass heavy shite dance music..

Just think of the anti-social fun blokes our age would have
cruising the roads with our choice of sounds blasting out the neighbourhood...


I'd probably start off near the local skateboard and BMX park
testing out the limits of the carboot sub-bass drivers
with early music massed battle drums and bagpipes..


errr.. if I could drive...

any good portable nuisance sound systems for cyclists ???


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Subject: RE: Subwoofer frequency question
From: Richard Bridge
Date: 15 Feb 11 - 05:01 PM

With piezo horn tweeters which are cheap you can give lots of bite to crumhorn recordings...


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Subject: RE: Subwoofer frequency question
From: GUEST,Jon
Date: 15 Feb 11 - 05:50 PM

What about Bombardes? Can they be made louder?


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Subject: RE: Subwoofer frequency question
From: The Fooles Troupe
Date: 16 Feb 11 - 06:26 AM

The energy involved in the low frequencies relative to the energy in the treble part would surprise you. You can actually calculate the energy, but I'll leave that to the maths majors here... Remember that music low frequencies can have a wavelength of a few meters, and start to overlap with earthquake frequencies, traveling very well ALONG (thru) the ground ...


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Subject: RE: Subwoofer frequency question
From: GUEST,TIA
Date: 16 Feb 11 - 06:34 AM

True that.
Earthquakes can be heard.


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Subject: RE: Subwoofer frequency question
From: Bernard
Date: 16 Feb 11 - 06:55 AM

Yes, bombardes can be made louder. Sorry, did someone speak?!


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