R
ruleworld
- Jan 1, 1970
- 0
i want to use stk439 amplifer which has 42 watt output with 7 watts
speaker. how can i do it without blowing up the speaker.
speaker. how can i do it without blowing up the speaker.
how to use low watt speaker with high watt amplifer
B
BobG
- Jan 1, 1970
- 0
Dont let the rms volts over several seconds get up above whatever
volts causes the voice coil to smoke. Have a several second time
constant RC averaging filter connected to a meter. Set the red line
3db below the danger level. Dont run the meter past that level.
volts causes the voice coil to smoke. Have a several second time
constant RC averaging filter connected to a meter. Set the red line
3db below the danger level. Dont run the meter past that level.
D
D from BC
- Jan 1, 1970
- 0
Huhhh....
Maybe try lowering the power supply voltage to the amp module.
Don't go too low..see amp specs for Vmin supply.
D from BC
J
Jan Panteltje
- Jan 1, 1970
- 0
Perhaps a resistor attenuator.
E
Eeyore
- Jan 1, 1970
- 0
ruleworld said:
Realistically you can't (easily).
You could add an average power measurement coupled to a VCA to reduce gain if
the power goes above the 7W average but it's way easier to find a more suitable
speaker.
Graham
E
Eeyore
- Jan 1, 1970
- 0
Jan said:
I thought he meant he still wanted the original peak output.
Just shows, the question was poorly worded.
Graham
B
BobG
- Jan 1, 1970
- 0
42 watts on the loud parts and 7 watts the rest of the time sounds
about right... any peaks higher than that 7 dB ratio will clip the amp
and sound crappy. There is always the 12V light bulb in the speaker
trick. (JBL does this. I thought I was seeing flames coming out of the
speaker... I could see the light turning on in the speaker thru the
port.)
about right... any peaks higher than that 7 dB ratio will clip the amp
and sound crappy. There is always the 12V light bulb in the speaker
trick. (JBL does this. I thought I was seeing flames coming out of the
speaker... I could see the light turning on in the speaker thru the
port.)
J
John Fields
- Jan 1, 1970
- 0
E
Eeyore
- Jan 1, 1970
- 0
Clearly you didn't.
Graham
Graham
D
D from BC
- Jan 1, 1970
- 0
Maybe the OP will be safe by only playing 7Watt songs.
Songs that have little base... Muzak otta do..
D from BC
R
Rich Grise
- Jan 1, 1970
- 0
Don't turn the volume up over about 16%. ;-)
Cheers!
Rich
R
ruleworld
- Jan 1, 1970
- 0
can i limit the volume somehow. maybe placing a resistor in series
with the volume control variable resistor?
C
Chris Jones
- Jan 1, 1970
- 0
ruleworld said:
Just don't turn it up too loud - ever - and it should be OK.
The power ratings on many consumer audio products are complete lies anyway,
so depending on whether the speaker manufacturer or the amplifier
manufacturer was the bigger liar, the real power capabilities of the two
devices could be very different from what they are rated at.
If you will not be in control of the volume knob yourself at all times, but
rather someone else like a child or a careless person will be using the
setup, then you might need a way of limiting the output of the amplifier.
One way to do this would be to connect a "Polyswitch" in series with each
speaker. The size of the polyswitch will need to be chosen appropriately
for the speaker. The polyswitch might get hot under fault conditions and
so it should ideally be installed in a metal enclosure (perhaps inside the
amplifier box) to prevent the risk of fire.
https://secure4.vivid-design.com.au/jaycar2005/images_uploaded/polyswit.pdf
Chris
D
D from BC
- Jan 1, 1970
- 0
How about glue a peg on the volume knob and glue another peg on the
face. That way when the knob is turned, it'll stop at the pegs.
D from BC
R
ruleworld
- Jan 1, 1970
- 0
thx. from your comments i found an idea. i will try put a resistor in
series and add a switch parallel to it to disable it so when i need
more volume i can get it by turning the switch on.
C
Chris Jones
- Jan 1, 1970
- 0
ruleworld said:
Possibly, but if you have different signal sources like CD player, MP3, etc.
that put out different sized signals, then it might be hard to find a limit
that is always appropriate. It also depends on what circuit is used for
the volume control of your amplifier, in some cases just a resistor in
series might not work well.
You could just not turn it up too loud, as I said before.
Chris
D
D from BC
- Jan 1, 1970
- 0
Maybe it's lack of sleep...
I didn't know how (globally) speaker power rating is tested..
(It's probably a cheapo 7W speaker from China..)
but I do know that whatever the test...it's probably a test of how hot
the voice coil can get.
That or when there's too much distortion...
I suspect DC can be roughly used to test voice coil power dissipation.
It's really about how much heat the voice coil can tolerate.
Of course, the voice coil seems to handle more power with increasing
frequency due to series inductance (for awhile). But... Isn't that
called apparent power?
I think of DC on speakers because I think of real power (heat) from
the resistive portion (~Rdc) of the impedance...
D from BC
E
Eeyore
- Jan 1, 1970
- 0
D said:
It's usually determined by some form of thermally related for sure.
Well NO.
Because a lot of the cooling effect comes from voice coil motion in air that removes the
heat. DC means no (long term) motion.
Graham
D
D from BC
- Jan 1, 1970
- 0
I just have a hard time believing the motion cooling is significant...
It looks like the voice coil is just buzzing around in it's own hot
air. The circulation is not like a fan.
It's probably why somebody made ferrofluid speakers..
D from BC
R
Rich Grise
- Jan 1, 1970
- 0
Heavens, yes! There's nothing to it! Find out the resistance of the pot,
and make a voltage divider.
The arithmetic, as usual, is left as an exercise for the student. ;-)
Cheers!
Rich
