What would 20hz at full volume do to a set of speakers?

Tubenoob

I brought some test tone cd's to a big box store and asked if I could try them out on some polk m20. The young man took his time hooking up the speakers(I don't know why they wasn't hooked up to begin with). When he was done I made sure to have the volume down on the receiver and popped in the cd. No sound,I didn't say anything and the salesman just cranked a denon bose system hooked up to the same player all the way to max! Very faint 20hz. I quickly turned down the unit,he then cranked the denon+denon unit up too!

knownalien

if a driver can't reproduce the frequency the crossover should prevent that frequency from playing.

but to answer your questions, that frequency (and of course a loud volume) would cause the driver to have deep excursions. In some drivers, it would be enough to blow them.

Lsi9

yah you wont hear it.

VR3

Some wont do anything, some will just move about 1-1.5" violently, yet still do nothing...

Some will crackle pop, make a wooofffing sound..

disneyjoe7

Lsi9 wrote:

yah you wont hear it.

You're Right but below that you may Feel it

Serendipity

I think the driver would be stressed greatly - would make some kind of sound or move abnormally.

knownalien

Lsi9 wrote:

yah you wont hear it.

in theory, you should be able to hear it. It is the floor frequency for humans. But, the speaker may not physically be able to reproduce it and in the end it really depends on the driver itself. Is it a 5" dirver or a 12" driver?

as for being able to "feel" it, if the driver moves at all it still depends on the size of the driver since at that point it comes down to displacement of air. Sound being rarifractions and compressions, a smaller driver just cannot move as much as a larger one . . . even if it tries.

disneyjoe7

IMO no speaker is designed for a stead tone of anything frequency. So any tone over a 1 second or so is bad for a speaker, the speaker can overheat burning its voice coil damaging speaker. Just my $.02

michael_w

Just ask the person that fried their LSi15 tweeters playing the mosquito ring tone . Just because you can't hear it doesn't mean nothing is happening... M20's, however, don't go nearly that low and trying to force them to play that low can't be good. I've run test tones to graph my sub and hearing / feeling a 20hz tone is pretty weird. Just remember to not push it hard when you're using sine waves. As joe... (Steve) pointed out it's one of the harder things for a speaker to handle and should be done with great care especially when you're dealing with frequencies you might not be able to hear.

disneyjoe7

Thanks Michael, I'm not sure a speaker can't produce that Mosquito ring tone it's just that must people can't hear it. But I can't stand it, drives me nuts.

michael_w

It should have produced the sound but the listener couldn't hear it so he kept turning it up. I guess with low frequencies you'll at least feel it, but nevertheless it's a harsh thing to put your speakers through.

disneyjoe7

michael_w wrote:

It should have produced the sound but the listener couldn't hear it so he kept turning it up. I guess with low frequencies you'll at least feel it, but nevertheless it's a harsh thing to put your speakers through.

Agreed

Deadof_knight

Did you ever see back to the future when he strummed the guitar hmmmm damn thing just blew right up !!!! 20 hz is a very long wave in audio terms. You have to have a drive made to handle it if you want it to survive !! hmmm lets see what my 4 jrs have to say about it #$$%#^^ No they said ! tweeter to driver are you ready ? ( driver) ready for what ? (tweeter) I hope you got protection !!! (driver) what? ...........POOOOOOF !!!!


Yes yes I hear something now it sounds like bacon sizzling ! yea I hear that too turn it up some more!!!!

steveinaz

Be careful with test tones, especially high frequency--your tweeters will get smoked. You don't "hear" 20Hz, you feel it.

dudeinaroom

When I was I high I was in high school a friend and I did a demo for a science teacher all 4 years we were there. We would bring in my friends Cerwin Vegas(he had dx9's 3-way 15" floor standers 4 ohm) and I grab the P.A. amp from the band room a peavy 350w/ch @ 4 ohm and would then go down to the lab and grab a frequency generator, and an oscilloscope and hook the whole deal up. The point was to let them see what the signal looked like on the scope and how the speaker reacted, and to hear the wonderful sound. We would start with a sine wave at 1hz(It's kinda cool to see a speaker move that slow) all the way up to 24khz. We would not feel anything till around 10 hz and around 12 hz you would get one guy saying he could hear it, and to turn it down, I didn't hear anything until around 15 hz and 20 hz the ceiling tiles would levitate. any how you can do it, not all speakers are going to give you sound, and not all are going to make things shake. Just make sure the signal is not clipping, the drivers are not bottoming out(you will hear a knocking noise), and don't over power the speaker.

disneyjoe7

Nice, levitate the ceiling tiles Love it. I also love when my Paradigm Servo 15 sub begins to shake the recessed lights in my family room

dudeinaroom

2 cerwins with 104 db@1 watt at 1 meter cna really make alot of sound(we used to dj school dances with them, and a set of jbl's was lots of fun(oh yeah, and I got paid to go to the dances)

Gaara

Wait what? I always thought human hearing was actually 16hz-18khz and the 20-20 was used roughly because it is easier to remember, am I missing something here?

Lsi9

How would one know if the tweeters are burnt?

Gaara

Smell, look, or test tones. If you see smoke somethings burning, if you put your nose to it and it smells funk it could have fried, or play a test tone like 16khz and see if you can hear it.

lanion

I did a computer science project using a lot of test tones and signal generation, and the college student age bracket can hear up to about 15khz with certainty and anything above that depended on the student (or turning the volume up a bit). The professors dropped off at around 13.5 or so (this was at low volume). Not that it really matters -- keep in mind 10khz to 20khz is only one octave. And you can hear 20hz a little -- my headphones can reproduce down to 3hz and I've played with them using test tones.

And speaking of seeing speakers move, it is very fun to watch a speaker going at 60hz or so if you have strobe lamp with variable frequency. I actually plugged a speaker directly into the wall (through a large transfomer, I have some sense!) If you set the strobe light to about 59hz or 61hz you see it move at 1 cycle per second.

knownalien

steveinaz wrote:

Be careful with test tones, especially high frequency--your tweeters will get smoked. You don't "hear" 20Hz, you feel it.

actually no. 20 is within human audible range and I can produce a 20 hz sin wave on my computer and play it. my system (below, really just the SVS) can play this wave for 10 seconds and you DO hear it.

Gaara

Try plugging them directly into wall, its a blast for sure.

On a related note polks fare pretty well with this type of toruture, but nothing beats bose. Those little cubes would not blow, they just keep bouncing around...pretty funny to watch though.

disneyjoe7

Gaara wrote:

Try plugging them directly into wall, its a blast for sure.

Funny but not 20hz. 60hz yes but not 20hz.

Gaara

The crazy thing was the bose sounded better after. It should be a new tweak, "Extreme Break-In".

rt7s

depends on the design and if full volume the amp is putting out clean signal. the result varies from blowing it to handling it just fine.