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 6Ω, 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 6Ω each and plug them into
the log and high terminals, you will only have a combined impedance of 3Ω"
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 are:
1. What would be the safest way to plug these speakers?
2. Any other thing I should check?
Thanks in advance!
On Monday, December 29, 2014 1:38:51 PM UTC-5, Alvaro Martinez wrote:
The stereo you apparently had came with speakers and has the crossover
network in the unit and it sends separate wires to the speaker elements.
Better and more typical stereo gear relies on the crossover being in the sp
eakers. You could probably hook one of your other speakers to the
high side on the left, the other to the low side on the left. Run the
stereo that way, then repeat on the right side.
The comment about 6 ohms becoming 3 ohms isn't clear, but I would expect
that they probably mean if you took your one 6 ohm speaker and connected
it to both high and low outputs in parallel. I would think they would
have just said not to use regular speakers.
Even with the existing speakers, can't you turn the balance one way or the
other, see if the problem persists? If it does, it's most likely not that
both speakers have failed with the same problem. The stereo failures I've
had, when it was intermittent like that, it was never the speakers. More
likely a loose cable connection or something shot in the unit.
don't sweat the impedance. It's just a test. Don't turn the volume
all the way up and you'll be fine.
I don't know anything about how your speakers are connected, but I'll
tell you a story.
Back in the day, I had a speaker that cut out.
The voice coil is wound with very fine, but rather stiff wire that can't
the flexing. The wires from the terminals are a much bigger extremely
braid. There are two holes in the cone where the flexible
wires enter from the back. The voice coil wires come out the front and
distance across the cone where they're soldered to the flexible
braid. The whole thing is covered with a glob of insulation.
What happened to me was that the connection broke right where
the two wires soldered together. It worked until it got hot and the
connection broke, then it cooled and started working again.
Can also be a function of the cone distention, not heat.
Anyhoo, I used an exacto blade to VERY CAREFULLY scrape the
insulation gunk off the very thin voice coil wire and resoldered
it to the braid.
I've also seen the braid break on the back side right where it
enters the cone.
You can test the theory by setting the volume to a very low level
and poking gently on the cone to flex the place where the wires join
to see if you can make it cut out.
Of course you can get the same symptom from a bad connection on the
circuit board or internal to an output IC.
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
Thanks for all your replies, I will read them carefully and try what you
Just wanted to add two comments: First, the problem occurs even when the
volume is low (maybe at 20% of the maximum).
Second, these are old systems, I don't know exactly because I got them
both from relatives, but they are probably 15 years old or so, and
mid-tier at best. I don't want to get them working as if they were new,
just want to avoid having to throw it away, or spending $200+ in a new one.
If you have a left and right speaker connected to two different sides of the amplifier...
And both sides are cutting out at the same time
Then the problem is probably NOT the speakers.
If only one side is cutting out, SWAP the left and right side
See if the problem"follows" the amp or the speakers.
Having two of wverything helps a lot when troubleshooting.
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
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.
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.
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.
Which is still the AC equivalent of resistance. DC doesn't have
reactance. So yes, nit-picking
Todays consumer amps are generally rated "peak power" or "peak music
power" which really doesn't mean a lot. The better ones also have
their RMS output listed - which is REAL power. Good amps also give you
percentage total harmonic distortion at rated power.
American consumers (and generally Canadian as well) buy numbers and
price, not performance and value. The marketing people know this and
take advantage of it,
For the purpose of troubleshooting, just plug one AIWA speaker into the
low frequency connection of each side. That should work well enough to
determine if the speakers are your problem.
You did not say, but if it affects both left and right channels at the
same time, replacing the speakers would not help that. You may have
dirty volume and/or balance controls. Rotate the controls in both
directions several times and see if that helps. If it gets worse or
results in scratchy sound, it may be necessary to spray some contact
cleaner inside the controls.
On Mon, 29 Dec 2014 23:19:22 -0500, email@example.com wrote:
This thread brings up something I've wondered for a long time. Back
around the 1950s and 60s, they used 70 volt (primary) transformers at
EACH speaker in a large building, such as an auditorium, or when
speakers sent a signal to rooms all over a school or factory. These
smallish transformers had a 70volt primary and the secondary usually had
a ground, with 4, 8, and 16 ohms, which went to usually just one
speaker. All those 70volt lines went back to the source amplifier,
which had a 70 volt output, coming from the amplifier's outpit
transformer, (and there was usually also at least an 8 ohm output as
well on the amp.
Anyhow, these amplifiers were high power vacuum tube amps, and had some
massive output transformers.
Back then, I played around with a lot of electronics, and got my hands
on several of those old tube amps, and a coffee can full of those (at
the speaker) 70v transformers. I learned at that time, that the reason
they did the system that way, was because there would be too much loss
running an 8 ohm line for hundreds of feet, as well as serious impedence
problems, if there were 10 or 20 speakers around the building (which
What I never did fully understand is whether the number of transformers
placed onto the amplifier's output could overload the amp, if too many
My other question is whether they still use those 70volt transformers on
modern semi-conductor amplifiers, and if so, how would they derive 70v
from a bank of output power transistors, since they dont have audio
output transformers anymore?
One further comment. Someone mentioned the ridiculous output ratings on
modern equipment. I was at Walmart a few years ago, and noticed a
On Wednesday, December 31, 2014 7:09:55 AM UTC-5, firstname.lastname@example.org wrote:
Sure, there is no free lunch. The amp that's driving it has to be
sized to the total load and if the load exceeds that, then it's overloaded.
The concept here appears to be the same as with power distribution. Instead
of sending 120V from the plant to your house, they step up the voltage,
the step it back down. You can send the same amount of power long distances
A - higher voltage and lower current
B - lower voltage and higher current
Choice A gives you less loss due to resistance in the lines, ability to use
smaller conductors, etc.
IDK, Pico says yes and provided a link, but the link appears broken.
I don't see why they can't still be using audio output transformers for
special applications like you're talking about. They are just a transformer,
still available, etc.
It's an interesting question. That's as extreme an example as I've ever
heard. Most of the consumer audio companies have been playing spec games
for a long time. Too many customers thing that 1000W automatically means
that the system is way better than one with 50W, that they really could use
all that power with their speakers, even if it were available, etc.
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