I wanted to ask

[kubeek]

Because those cancel at wider part of the "center" than higher frequencies?

 

[SouthSIDE Glen]

Because those cancel at wider part of the "center" than higher frequencies?

I can see what your saying, but here's a couple of sample numbers:

1kHz equals ~13 inches full wavelength
2kHz = ~7 inches wavelength
5kHz - ~3 inches wavelength

Even if we assume that at least a 75% phase shift were required to have audible levels of attenuation, we're talking a "center" that's 3.25" wide at 1kHz, 1.75" wide at 2kHz, and .75" wide at 5kHz. All quite large enough to notice, though perhaps only on one ear at a time. Perhaps more important and evident would be that there will be just the opposite - coincident peak modes - just a half wavelength away for very definite apparent comb filtering at those frequencies.

I'm not saying that it wasn't a polarity issue, it apparently was. I'm just saying (I guess?) that we must have been given a incomplete description of the symptoms, because just a loss of bass wouldn't seem to indicate a polarity problem.

G.

 

[aviv]

I can see what your saying, but here's a couple of sample numbers:

1kHz equals ~13 inches full wavelength
2kHz = ~7 inches wavelength
5kHz - ~3 inches wavelength

Even if we assume that at least a 75% phase shift were required to have audible levels of attenuation, we're talking a "center" that's 3.25" wide at 1kHz, 1.75" wide at 2kHz, and .75" wide at 5kHz. All quite large enough to notice, though perhaps only on one ear at a time. Perhaps more important and evident would be that there will be just the opposite - coincident peak modes - just a half wavelength away for very definite apparent comb filtering at those frequencies.

I'm not saying that it wasn't a polarity issue, it apparently was. I'm just saying (I guess?) that we must have been given a incomplete description of the symptoms, because just a loss of bass wouldn't seem to indicate a polarity problem.

G.

Maybe i wasnt being as specific as possible, the speakers where outputing bass but where i sat and because of the phase of the polarity they just seemed to have cancelled each other out.
I cant do the scientific calculations but I could tell it didnt sound right then
P.S good speakers, sounding ace now!

 

[dementedchord]

60 volts peak into 4 ohm speakers is 450W (225W into 8ohm). Definitely not a home stereo.

The 9v battery, when you leave it connected for any longer than just sratching the terminals can produce cca 25W into 4ohm. That is more than enough to burn some voicecoils, because speakers are not designed for DC.

go look at some schemos of generic amps and get back to me... +/-60V is low for most amps...

 

[kubeek]

go look at some schemos of generic amps and get back to me... +/-60V is low for most amps...

There is a big difference between rail voltage and possible swing of output.
You need to add some voltage drop over c-e due to high currents, rails sagging (a lot with small power supply caps and undersized transformers in cheap amps, and it is most obvious at very low frequencies), and balancing resistors and you end up at about 10 maybe 15 volts less under full load.

So a loaded "cheap ass stereo" will swing to cca +/- 45V. That is a lot more realistic, because you end up with 125W@8ohm and usually 1.5 times more at 4ohm and instead of theoretical double power, because of transformer current limitations.

I made a few amplifiers, including my 500W amp for bass guitar so I can say I know what they are capable of.

 

[dementedchord]

yet it seems our experiences differ... granted i mostly worked on pro amps over my +10yrs as a tech crown/qsc/mackie/crest/audiopro ....

 

[aitikin]

The question I have is if it were a polarity reversal, why were only the bass frequencies affected?

G.

Couldn't it simply be that the bass is the most prominent thing that's center panned? There's probably more that was wrong, but it probably wasn't nearly as noticeable as the bass. Just my $.02