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From: Phil Allison on 25 Dec 2009 19:29

"Peter Dope"

>
>>I have a Cerwin Vega HT-S12A subwoofer that has begun making an
>>electronic distortion. The speaker itself seems fine when I do a push
>>pull and tap --
>
> Wow, that's a really good scientific test...


** It's a valid test procedure and perfectly "scientific".

Like the majority of test procedures, it is not *absolute* - but if the
device fails the test you have your culprit.

However, it passes the test, there are other tests that may need doing.

It is possible to perform a very large number of tests on a loudspeaker,
not one of which conclusively proves it has no faults.

But if the OPs test is failed, then none of them need doing.


...... Phil




From: Phil Allison on 25 Dec 2009 19:33

"Lovguitar"
>I have a Cerwin Vega HT-S12A subwoofer that has begun making an
> electronic distortion. The speaker itself seems fine when I do a push
> pull and tap -- no voice coil rub. Just putting my hand near the
> speaker causes a slight humming, however. The gain of the unit seems
> OK, it gets pretty loud, but the louder you turn it the louder the
> distortion gets. I've taken to turning the unit off because even when
> it's getting no signal it will start to hum and buzz sometimes. Not a
> 60 cycle sounding hum, a buzzy distortion.
>
> Any troubleshooting ideas?


**Yep - remove the woofer and connect the leads from the amp to another
( known good) speaker.

Also try the woofer with another amplifier - even a guitar amp will do.

Leads with alligator clips at each end are very handy for this.



..... Phil


From: PeterD on 26 Dec 2009 09:11
On Sat, 26 Dec 2009 00:02:22 -0000, "Arfa Daily"
<arfa.daily(a)ntlworld.com> wrote:

>
>"PeterD" <peter2(a)hipson.net> wrote in message
>news:507aj5194dq54eqj6pleu0khetgrq1sr3p(a)4ax.com...
>> On Fri, 25 Dec 2009 11:03:24 -0800 (PST), Lovguitar
>> <lovguitar(a)aol.com> wrote:
>>
>>>I have a Cerwin Vega HT-S12A subwoofer that has begun making an
>>>electronic distortion. The speaker itself seems fine when I do a push
>>>pull and tap --
>>
>> Wow, that's a really good scientific test...
>>
>
>Just goes to show what you know about service work then ...
>
>Arfa
>

Clearly more than some people (I'll exclude you, since you do know
what you are doing.) bottom line is that that test is very limited,
and won't show the problem that he's experiencing which is distortion
at higher volume levels...

From: PeterD on 26 Dec 2009 09:11
On Sat, 26 Dec 2009 11:29:01 +1100, "Phil Allison" <phil_a(a)tpg.com.au>
wrote:

>
>"Peter Dope"
>
>>
>>>I have a Cerwin Vega HT-S12A subwoofer that has begun making an
>>>electronic distortion. The speaker itself seems fine when I do a push
>>>pull and tap --
>>
>> Wow, that's a really good scientific test...
>
>
>** It's a valid test procedure and perfectly "scientific".
>
>Like the majority of test procedures, it is not *absolute* - but if the
>device fails the test you have your culprit.
>
>However, it passes the test, there are other tests that may need doing.
>
>It is possible to perform a very large number of tests on a loudspeaker,
>not one of which conclusively proves it has no faults.
>
>But if the OPs test is failed, then none of them need doing.
>
>
>..... Phil
>
>

Agreed.

>
From: Arfa Daily on 26 Dec 2009 19:33

"PeterD" <peter2(a)hipson.net> wrote in message
news:0a6cj5129ra7gr6sj2mr22aopebge83j7j(a)4ax.com...
> On Sat, 26 Dec 2009 00:02:22 -0000, "Arfa Daily"
> <arfa.daily(a)ntlworld.com> wrote:
>
>>
>>"PeterD" <peter2(a)hipson.net> wrote in message
>>news:507aj5194dq54eqj6pleu0khetgrq1sr3p(a)4ax.com...
>>> On Fri, 25 Dec 2009 11:03:24 -0800 (PST), Lovguitar
>>> <lovguitar(a)aol.com> wrote:
>>>
>>>>I have a Cerwin Vega HT-S12A subwoofer that has begun making an
>>>>electronic distortion. The speaker itself seems fine when I do a push
>>>>pull and tap --
>>>
>>> Wow, that's a really good scientific test...
>>>
>>
>>Just goes to show what you know about service work then ...
>>
>>Arfa
>>
>
> Clearly more than some people (I'll exclude you, since you do know
> what you are doing.) bottom line is that that test is very limited,
> and won't show the problem that he's experiencing which is distortion
> at higher volume levels...
>

OK, I'll give you that, but the test will pick up most raspy distortion
problems that are to do with the speaker itself. Sometimes, however, the
problem can be due to mechanical resonances which only show up at high drive
levels, in which case the push - pull test will, as you rightly say, reveal
absolutely nuffink ... :-)

Arfa


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