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Tony Hwang

gregz wrote:
Tony Hwang wrote:
wrote:
On Mon, 29 Dec 2014 20:48:01 -0700, Tony Hwang
wrote:

Alvaro Martinez wrote:
Hi All,
This is the first time I post here, I apologize if this has been
discussed before. I like to tinker with equipment but my knowledge is
basic at best, and it advances along with the problems I get to solve

To get straight to the point of the problem I need to solve:

I have a Panasonic SC-AK45 system, which is having some issues with
random "cuts" in its sound (sub-second interruptions, no distortion,
just lack of sound), and I am not experienced enough to figure out if it
is because bad cables, speakers, or the system itself.

I have the speakers for an old AIWA stereo system, their tags say their
impedance is 6?, which is the same I can read in the Panasonic speakers.
However, the Panasonic speakers have two pairs of cables, one for high
and another for low frequency, and the manual says the following:

"if you connect speakers with an impedance of 6? each and plug them into
the log and high terminals, you will only have a combined impedance of 3?"

I want to connect the AIWA speakers to the Panasonic system, to find out
if the speakers are the problem. So the questions for the group a

1. What would be the safest way to plug these speakers?
2. Any other thing I should check?

Thanks in advance!
Hi,
Sounds like to me sound is cutting out because Panasonic is over driven
(playing too loud) or impedance is too low for the unit. Most often
nominal impedance for those kinda device is 4 or higher Ohms. Good high
quality amps can take as low as 2 Ohms but I don't think that Panasonic
is really high end device. Lower the playing volume and see what happens
or use higher impedance speakers. If it keeps happening the amp may burn
up. Impedance is one thing but you have to watch Wattage rating too ie.
how much power it can take. Low impedance can draw more
current from the device destroying the speaker when amp is not designed
for that.
OK, lets get something straight. Impedence is NOT just a test or a
number. Impedence is the AC version of resistance. It is a measure of
the load placed on a circuit.
Say an amplifier outputs 20 volts and can handle a maximum of 5 amps
output. That is 100 watts PP output. If the speaker has a 4 ohm
impedence, at 20 volts it will draw 5 amps for 100 watts pp power
output
If you have an 8 ohm speaker, it will only draw 2.5 amps, which will
only ouput 50 watts.
If on the other hand you connect a 2 ohm speaker to that amplifier it
will draw 10 amps - which will overload the amplifier, and if the
amplifier is capable of pumping out the required 10 amps, it will
produce 200 watts, and fry the speaker.

Always err on the side of too much impedence rather than too little.

Connecting speakers in series, you add the two impedences together. If
you connect them in parallel you reduce the impedence.Rt= 1(1/R2)=
1(1/R2) - so 2 8 ohm speakers in series is 16 ohms, and in parallel
is 4 ohms. A 4 ohm and a 8 ohm in series is 12 ohms and in parallel =
2.66 ohms.

So the OP with a speaker with 2 6 ohm drivers would connect the 2 in
series to get 12 ohms of impedence to connect to the amplifier
designed for 6 ohm speakers and will get reduced output but will not
damage either the speakers or the amp.

Hi,
Nit picking? Impedance Z is combination of resistance plus reactance,
root of (R+jX)which varies with frequency. So Impedance on speaker is
nominal rating at 1000Hz audio frequency. Speaker engineering is quite
complex. My old Quad DC amp can load a piece of wire without burning out.
Today'S most consumer amps are way over rated. If it is rated at 100W,
maybe good for true rms 20W or less. Power is one thing, dirty
signal(distortion) can destroy amps more easily than over powering.

It was explained recently on Rec.audio.tech. You might specify 1000 hz, but
you must consider the minimum Z and it can't be less than 50% of specified
Z. Most common modern amplifiers can't drive low Z. The lowest Z of a
speaker is usually on the low end.

Greg

Hi,
Most 12V car amps can load 2 Ohm speakers. They are not AB1 or AB2 class
amps. D or G class with MOSFETs. Like I said my old Quad PA can
take piece of wire without suffering damage. Frequency response is
almost flat from DC to ~20KHz.