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-   -   Question, about power, audio power into speakers... what happens? (http://www.diyaudio.com/forums/solid-state/124285-question-about-power-audio-power-into-speakers-what-happens.html)

destroyer X 4th June 2008 10:47 AM

Question, about power, audio power into speakers... what happens?
 

If you are able to explain, using theories or practice, i will thank you in advance by your kind contribution into the subject.

Now i will explain the problem Brazilian powerholics asked me and i was in troubles to answer, as i do not know exactly what the correct answer is:

If you have a speaker.... and the unit is 8 ohms... and you inject 4 volts of sinusoidal 60 hertz tone.... from a transformer for instance.... something around 2 watts.... and this special speaker (very common to find those ones) travell to the end of it's own limits.. almost reaching the top end and low end of the compliance..... so... the speaker is receiving it's maximum sinus voltage rigth?.....if you inject more, the speaker will not move more to the top limit or down limit of movement (diafragm pointing the sky).

SO, WHAT HAPPENS if you send 20 volts to the speaker?

Let's suppose the coils can hold this level (not very easy to find those ones)....for long time..... what happens?

I imagine not more sinus.... the audio propagated wave will be pulsating alike square wave.

But powerholic folks are using speakers that has sensitivity to maximum movement (air pumping) using 10 volts RMS... and they are sending 25 or 35 volts of sinus audio...RMS tones!

ARE THEY DEAF to distortions?

The back EMF is cancelling some of the power by phase cancelation?

Are you able to clarify that to me?....... i have found 200 watts amplifiers better WHEN you use them into low levels, distortion very low and class A operation... also i found too much distortions when i use more than 35 to 50 watts into any speaker (common, standard, normal ones).

Are those special speakers hard to move as i imagine?.... needing a lot of energy to move and reach the maximum compliance limit?

This makes me conclude, realise, that a 10 watt speaker, a 10 inch one, moving 10 milimeters when receiving 10 watts will produce the same sound level that a 100 watt speaker, a 10 inch one, moving 10 milimeters when receiveing 100 watts?

Can you contribute?

Please, let your opinion written in this thread... for sure will help and will be respected as a nice and important contribution to the reduction of ignorance under this subject, not only mine, for Brazilian folks and also for some forum people too.

regards,

Carlos

richie00boy 4th June 2008 11:23 AM

Re: Question, about power, audio power into speakers... what happens?
 
Quote:

Originally posted by destroyer X
This makes me conclude, realise, that a 10 watt speaker, a 10 inch one, moving 10 milimeters when receiving 10 watts will produce the same sound level that a 100 watt speaker, a 10 inch one, moving 10 milimeters when receiveing 100 watts?
Yes, that is correct.

The second speaker may need more power to travel the same because it has a heavier cone to achieve lower resonance frequency. Also it may have smaller box volume requirements.

Steerpike 4th June 2008 12:47 PM

The voltage impressed on the speaker does not directly translate into a distance moved.

The voice coil produces a FORCE proportional to the current,
The force ACCELERATES the coil and cone; it's a rate of change of velocity, not a displacement
At the same time, the springiness of the compliance conteracts this force, and this spring force gets larger as the distance travelled by the cone is increased, so the cone doesn't reach a brick-wall dead stop, it just encounters an ever greater retarding force.

The actual displacement is then the solution to the differential equation:

dx/dt + (k/m)x = BI

which I can't show solved in this text editor, but will come back to with a graphic.

Yes inded the distortion rises, but it's not as severe as you have suggested.

kevinkr 4th June 2008 01:32 PM

Re: Question, about power, audio power into speakers... what happens?
 
Quote:

Originally posted by destroyer X

If you are able to explain, using theories or practice, i will thank you in advance by your kind contribution into the subject.

Now i will explain the problem Brazilian powerholics asked me and i was in troubles to answer, as i do not know exactly what the correct answer is:

If you have a speaker.... and the unit is 8 ohms... and you inject 4 volts of sinusoidal 60 hertz tone.... from a transformer for instance.... something around 2 watts.... and this special speaker (very common to find those ones) travell to the end of it's own limits.. almost reaching the top end and low end of the compliance..... so... the speaker is receiving it's maximum sinus voltage rigth?.....if you inject more, the speaker will not move more to the top limit or down limit of movement (diafragm pointing the sky).

SO, WHAT HAPPENS if you send 20 volts to the speaker?

Let's suppose the coils can hold this level (not very easy to find those ones)....for long time..... what happens?

I imagine not more sinus.... the audio propagated wave will be pulsating alike square wave.

But powerholic folks are using speakers that has sensitivity to maximum movement (air pumping) using 10 volts RMS... and they are sending 25 or 35 volts of sinus audio...RMS tones!

ARE THEY DEAF to distortions?

The back EMF is cancelling some of the power by phase cancelation?

Are you able to clarify that to me?....... i have found 200 watts amplifiers better WHEN you use them into low levels, distortion very low and class A operation... also i found too much distortions when i use more than 35 to 50 watts into any speaker (common, standard, normal ones).

Are those special speakers hard to move as i imagine?.... needing a lot of energy to move and reach the maximum compliance limit?

This makes me conclude, realise, that a 10 watt speaker, a 10 inch one, moving 10 milimeters when receiving 10 watts will produce the same sound level that a 100 watt speaker, a 10 inch one, moving 10 milimeters when receiveing 100 watts?

Can you contribute?

Please, let your opinion written in this thread... for sure will help and will be respected as a nice and important contribution to the reduction of ignorance under this subject, not only mine, for Brazilian folks and also for some forum people too.

regards,

Carlos

In the case of a woofer whether or not it is installed in a properly sized box will play a large role in how much cone movement (excursion) you get at a given power level. (Steerpikes comments are correct and well explained.) Unbaffled in open air the cone is unloaded, (excluding the spider and suspension losses) in a sealed box the airspring increases that loading, and hence the amount of voice coil current required for a given excursion..

whoandcar 4th June 2008 04:58 PM

In practical terms, the displacement of the cone is lower and lower as the frequency increases (in open air) as the voltage translates into speed (velocity) of the cone and not distance.

In a well designed (tuned) cabinet, the air pressure tries to counteract the severe displacement that otherwise would occur at lower frequencies.

And yes, sometimes the cone "bottoms" and this is a very severe distortion, and can be heard as a "metallic" sound.

When the cone reaches its maximium desplacement, the energy translates only into heat in the moving coil, and no more into sound.

EWorkshop1708 5th June 2008 12:25 AM

The magnets field only goes so far

Ever play a speaker and push it in and out to see where it plays the loudest? ....usually when the speaker is pushed or pulled really far there's much less sound

The farther away the coil moves from the magnet, the less magnetic field, so pumping even more watts all goes into heat because the coil is getting out of range of the magnet. - that's usually when you hear the speaker distort with bass and it's not even maxing out the spider

east electronics 5th June 2008 07:06 AM

i can make my input
 
but you guys real experts will have to make the math .....

once i had to work for a bar that had installed a 2way system made by one JBL 15" woofer installed in a tuned bass reflex box
( the one with the long reflex curve very famous arround the 80's) and one high freq driver with a horn 6x15" JBL

powered by two amps and citronic electronic xover one EQ 2x16 and there also existed a greek made device which actually was a parametric equalizer with adjustable Q ,gain, and of course frequency

nobody knows how to operate that but it was connected and set to bypass ...

iwas only 18 at the time so what i did is actually set the gain of the parametric at bass to +12DB set the Q of the filter somewhere in the midle so it wasnt "splatering" over a wide range of frequency and then make a full turn from start till end to the frequency knob and then OOOOOPS !!!! at a certain frequency it sounded that the bass was like 10 times more at least !!!!

then reduced the gain to something like +3-4 db and then retune the all system ........for high freq and EQ curve

what i actually did is "TUNE" the woofer with the box and probably the space .....



club run for 8 years with this tuning ...problem free producing loads of club bass without even cliping ( everybody was wondering what made it so effective ) considering that this particular area was full of clubs and others had simular equipment that didnt produce this sound

so carlos what i mean is that there is a hell of alot more than electrical measures to understand how the all thing works in such power level like 300w rms .........

whoandcar 5th June 2008 11:45 AM

Re: i can make my input
 
Quote:

Originally posted by sakis
.....installed in a tuned bass reflex box
( the one with the long reflex curve very famous arround the 80's).........
[/B]
You mean the famous John Karlson ?

destroyer X 5th June 2008 03:56 PM

Thank you folks...good ideas, examples, opinions and analises posted here
 

Thank you very much.

regards,

Carlos

east electronics 6th June 2008 07:19 AM

the enclosure of jbl
 
since iwas 18 i had the plesure to work withy one of the most power full systems in my life ( disco club ) for 2000 people in athens
the system
4 cabinets 18" jbl subs
4 cabinets martin 12" sub V type
4 2x15" reversed tuned bass reflex ( another 4 on right side )
4 15" midrange jbl drivers ( another 4 on right side )
4 midrange compresion drivers ( another 4 on right side )
1 midrange driver ( cinema version 1mx1m) same on ridht side
and totaly 40pcs of 2405 tweeters as 20 per side .....!!!!!!!!

all of it JBL all units driven by individual amplifiers

the wonderfull 80's .....disco times

been running this system for almost 6 years ......what a school !!!!http://www.lansingheritage.org/image.../c34/page1.jpg


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