Hey folks.
After hooking up my old 80's Amp to 2 pairs of speakers (A+B outputs) a
while back for my son's party/disco we seem to have over-driven them a
tad....
In theory the MAX output of the amp is 120W RMS (Technics SEM1000 class
AA? Amp)
The speakers should both have been good for 75W + 80W but now the
"decent" speakers (Kef Coda 7SE) seem to have lost all treble response.

What is the most likely point of failure? Tweeter or something on the
crossover?

What would be a starting point for testing?

TIA
Pete@
--
Http://www.GymRatZ.co.uk
Commercial Gym Flooring and Equipment etc

On 19/08/2013 16:26, www.GymRatZ.co.uk wrote:
Hey folks.
After hooking up my old 80's Amp to 2 pairs of speakers (A+B outputs) a
while back for my son's party/disco we seem to have over-driven them a
tad....
In theory the MAX output of the amp is 120W RMS (Technics SEM1000 class
AA? Amp)
The speakers should both have been good for 75W + 80W but now the
"decent" speakers (Kef Coda 7SE) seem to have lost all treble response.

What is the most likely point of failure? Tweeter or something on the
crossover?

What would be a starting point for testing?

TIA
Pete@



Not often the tweeter goes as most of power is through bass unit.
Get a 1.5V battery attach some leads and flick it across terminals of
tweeter .. if it clicks OK .. probably fine.

Could be capacitor in the crossover

No its the square waves from the clipping that ruin the tweeters.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Rick Hughes" wrote in message
...
On 19/08/2013 16:26, www.GymRatZ.co.uk wrote:
Hey folks.
After hooking up my old 80's Amp to 2 pairs of speakers (A+B outputs) a
while back for my son's party/disco we seem to have over-driven them a
tad....
In theory the MAX output of the amp is 120W RMS (Technics SEM1000 class
AA? Amp)
The speakers should both have been good for 75W + 80W but now the
"decent" speakers (Kef Coda 7SE) seem to have lost all treble response.

What is the most likely point of failure? Tweeter or something on the
crossover?

What would be a starting point for testing?

TIA
Pete@



Not often the tweeter goes as most of power is through bass unit.
Get a 1.5V battery attach some leads and flick it across terminals of
tweeter .. if it clicks OK .. probably fine.

Could be capacitor in the crossover

On Mon, 19 Aug 2013 16:26:21 +0100, "www.GymRatZ.co.uk"
wrote:

Hey folks.
After hooking up my old 80's Amp to 2 pairs of speakers (A+B outputs) a
while back for my son's party/disco we seem to have over-driven them a
tad....
In theory the MAX output of the amp is 120W RMS (Technics SEM1000 class
AA? Amp)
The speakers should both have been good for 75W + 80W but now the
"decent" speakers (Kef Coda 7SE) seem to have lost all treble response.

What is the most likely point of failure? Tweeter or something on the
crossover?

What would be a starting point for testing?

TIA
Pete@

Tweeter voice coil is more likley than the X-over.

--
Graham.

%Profound_observation%

On 19/08/2013 16:26, www.GymRatZ.co.uk wrote:
Hey folks.
After hooking up my old 80's Amp to 2 pairs of speakers (A+B outputs) a
while back for my son's party/disco we seem to have over-driven them a
tad....
In theory the MAX output of the amp is 120W RMS (Technics SEM1000 class
AA? Amp)
The speakers should both have been good for 75W + 80W but now the
"decent" speakers (Kef Coda 7SE) seem to have lost all treble response.

What is the most likely point of failure? Tweeter or something on the
crossover?

What would be a starting point for testing?

Tweeter voice coil or a fuse in the circuit to it. Any voltmeter with a
continuity tester should be good enough. Crossovers are usually plenty
robust against anything an amplifier can do to them. The lightweight
coils on the tweeter are generally the weakest link.

If the amplifier was over driven to the point of clipping then you get a
lot of nasty harmonics in the clipped waveform and this will potentially
destroy loudspeaker tweeters as will sweeping a pure sine wave at
80-100W when you hit one of the enclosure resonances.

--
Regards,
Martin Brown

On Monday, August 19, 2013 4:56:15 PM UTC+1, Martin Brown wrote:
On 19/08/2013 16:26, www.GymRatZ.co.uk wrote:

Hey folks.
After hooking up my old 80's Amp to 2 pairs of speakers (A+B outputs) a
while back for my son's party/disco we seem to have over-driven them a
tad....
In theory the MAX output of the amp is 120W RMS (Technics SEM1000 class
AA? Amp)
The speakers should both have been good for 75W + 80W but now the
"decent" speakers (Kef Coda 7SE) seem to have lost all treble response.

What is the most likely point of failure? Tweeter or something on the
crossover?

What would be a starting point for testing?

Tweeter voice coil or a fuse in the circuit to it. Any voltmeter with a
continuity tester should be good enough. Crossovers are usually plenty
robust against anything an amplifier can do to them. The lightweight
coils on the tweeter are generally the weakest link.
If the amplifier was over driven to the point of clipping then you get a
lot of nasty harmonics in the clipped waveform and this will potentially
destroy loudspeaker tweeters as will sweeping a pure sine wave at
80-100W when you hit one of the enclosure resonances.

+1. If the tweets are oc, theyre normally rewindable, if you have a few hours. Or you can take tweets from some free speakers for a free option - this generally works out fairly well, though not to original spec. Do get the phasing right.


NT

In article ,
www.GymRatZ.co.uk wrote:
Hey folks.
After hooking up my old 80's Amp to 2 pairs of speakers (A+B outputs) a
while back for my son's party/disco we seem to have over-driven them a
tad....
In theory the MAX output of the amp is 120W RMS (Technics SEM1000 class
AA? Amp)
The speakers should both have been good for 75W + 80W but now the
"decent" speakers (Kef Coda 7SE) seem to have lost all treble response.

Their quoted max is 70w.

What is the most likely point of failure? Tweeter or something on the
crossover?

What would be a starting point for testing?

Disconnect one of the wires to the tweeter and measure the resistance of
the tweeter. Should be something like 4-16 ohms. If it's open circuit you
have your answer.

TIA
Pete@

--
*If a pig loses its voice, is it disgruntled?

Dave Plowman London SW
To e-mail, change noise into sound.

On 19/08/2013 16:26, www.GymRatZ.co.uk wrote:
Hey folks.
After hooking up my old 80's Amp to 2 pairs of speakers (A+B outputs) a
while back for my son's party/disco we seem to have over-driven them a
tad....
In theory the MAX output of the amp is 120W RMS (Technics SEM1000 class
AA? Amp)
The speakers should both have been good for 75W + 80W but now the
"decent" speakers (Kef Coda 7SE) seem to have lost all treble response.

What is the most likely point of failure? Tweeter or something on the
crossover?

When up near the top of the audio spectrum, you probably aught to
suspect the tweeter itself - especially if the output of the amp itself
was clipping. That will spew lots of HF energy energy out that will end
up being fed to the tweeters where it comes out as heat.

What would be a starting point for testing?

Check the tweeter coil is not open circuit.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 19/08/2013 16:26, www.GymRatZ.co.uk wrote:

What would be a starting point for testing?

Brilliant.
Thanks folks I'll attempt to get into them and see what goes.
FWIW the amp is a big old beast.
http://audio-database.com/TechnicsPa...se-m100-e.html
Only discrepancy on the above tech. is power consumption stated at 235W
whereas the unit is stamped up at 930W and it was getting pretty warm.
Someone might have cranked it up to 0 as the volume is marked off in -db
with the last half of the scale making having very little effect on output.


Thanks again for all advice.

Cheers
Pete@

Tweeters die when presented with clipped audio, so if it was overloading
the amp bang go your tweeters I'm afraid.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"www.GymRatZ.co.uk" wrote in message
...
Hey folks.
After hooking up my old 80's Amp to 2 pairs of speakers (A+B outputs) a
while back for my son's party/disco we seem to have over-driven them a
tad....
In theory the MAX output of the amp is 120W RMS (Technics SEM1000 class
AA? Amp)
The speakers should both have been good for 75W + 80W but now the
"decent" speakers (Kef Coda 7SE) seem to have lost all treble response.

What is the most likely point of failure? Tweeter or something on the
crossover?

What would be a starting point for testing?

TIA
Pete@
--
Http://www.GymRatZ.co.uk
Commercial Gym Flooring and Equipment etc

On 19/08/2013 16:26, www.GymRatZ.co.uk wrote:

Just to update this one - Thanks for the suggestions.
Last night I removed said tweeter units to find that whereas Bass
drivers were connected to crossover by soldered joints the tweeters were
wobbly spade connectors.

Still stuck 1.5v across unit and got scratchy noise and each unit
measured around 10 ohms so quick tightening to the connector,
re-assembly and job's a good-un.

Thanks again for giving me an armoury of simple tests get the job done.

Cheers - Pete

Hey folks.
After hooking up my old 80's Amp to 2 pairs of speakers (A+B outputs) a
while back for my son's party/disco we seem to have over-driven them a
tad....
In theory the MAX output of the amp is 120W RMS (Technics SEM1000 class
AA? Amp)
The speakers should both have been good for 75W + 80W but now the
"decent" speakers (Kef Coda 7SE) seem to have lost all treble response.

What is the most likely point of failure? Tweeter or something on the
crossover?

What would be a starting point for testing?