On the Importance of Speaker Phasing

[Josh]

Speaker phasing is important.

The optimus speaker attached to the scanner seemed to be having reduced/distorted output lately and I considered that the scanner perhaps needed not just display bulbs but an alignment or other repair to bring back the clear, loud audio as in the past.

So as a test I reconnected the speaker to the external speaker jack to make sure the spring connectors held the wire firmly, and no audio resulted, making me positive the speaker was at fault and finally gave up, perhaps a shorted cap?

I opened the speaker and noted things looked fine.... and then considered the cable as the scanner's internal speaker had no issues producing clean audio. I had missed the wire and had clamped on to the insulation, no wonder the speaker didn't work.

Ensuring that continuity was made resulted in a working speaker, but the audio was really odd like before, some sigs where more or less ok, some sigs sounded like a poop salesman with a mouth full of samples. This made me wonder if the audio chip was going bad, wasn't getting enough current due a faulty psu, or the scanner needed an alignment after almost daily use since oh around 1995.

Disconnecting the cable from scanner and speaker allowed ohming out the input jack, testing verified the speaker was out of phase, go figure. Rectifying the mistake resulted in clean and clear audio.

If your speaker sounds like mush, perhaps you're inverted?

https://www.uaudio.com/blog/understanding-audio-phase/

[ThaDood]

Look in the audio chain on your scanner. Both of my Uniden BC-175XL and BC-210XLT 1980's scanners had the same problem. In both cases, it was an electrolytic CAP in the near output of the scanners' audio chains. Once I'd swapped them, full audio restored. No doubt, Uniden custom made your scanner as well. If I remember right, the CAP was a DC blocker that was rated at 10VDC, instead of 16VDC, or higher, like it should be. Uniden did that also on an original RCI-2950 All-Mode 10M rig, which came to sounding very raspy to everyone in SSB. Sure enough, a whole bunch of under rated, low voltage, electrolytic CAP's in there needed replacing. I'm still using that rig as well. Amazing the corners companies cut to save $$$$$.

[Josh]

Thanks for the idea, will be checking caps shortly.

[NJQA]

Disconnecting the cable from scanner and speaker allowed ohming out the input jack, testing verified the speaker was out of phase, go figure. Rectifying the mistake resulted in clean and clear audio.

If your speaker sounds like mush, perhaps you're inverted?

You just had just one speaker connected to the scanner?  How can you have out of phase cancellation with just one speaker?

[Josh]

When the speaker is supposed to fire outwards rather than inwards?

[JimIO]

That's like the HAMs that say microphone phasing matters because they have an asymmetrical voice. Maybe if they are from MiSSiSSiPPi.   

[redhat]

Before aggressive AM processing became common in the 1970's, it was common practice to wire all studio mics so that positive pressure on the diaphram would cause positive carrier modulation.  Once newer processing techniques involving all-pass networks became common, this process became irrelevent.  Audio guys like Orban discovered that asymmetry causes problems in processing, namely limiting which caused greater distortion than symmetrical audio, and all modern processors include all-pass (Phase scrambler) networks to remedy this.

+-RH

[JimIO]

"... and all modern processors include all-pass (Phase scrambler) networks to remedy this."

Maybe all that modern dance mix k-pop crap sounds so bad to me because I don't have any radios with phase descramblers in them!