Is polarity standardized across brands of speakers and amps?

[highfigh]

The terminals on the Onkyo cylinders are not labeled - they're not even banana jacks but spring-loaded for inserting a wire. These are old cheap "SKC-240F" HTIB units that I'm repurposing the front pair of as my overheads (with a second set bought on eBay for that purpose).

I'm assuming that if I treat their black terminals like the black terminals of the other speakers, it won't matter that their other terminals are white instead of red.

Alternatively, I could put one of them next to one of the Boston Acoustics, playing the same mono signal, I could determine which way they were in and out of phase.

Face the speakers toward each other- if the bass disappears, one of the amps is reverse phase. This can be verified by turning one of the speakers away from the other and hearing the bass return.

 

[Verdinut]

I was thinking more of the fire that could result- 120VAC across 8 Ohms works out to 1800W. Well, and people reaching their target heart rate when the sound starts.

No, the high current draw lasts only a fraction of a second, not long enough to cause a fire.

 

[Verdinut]

And cones that need to be re-speakered. Probably magnets that need to be re-magnetized, too.

The friend whose speakers had to be reconed did not have to get the magnets re-magnetized. The speakers were 8 inch Altec 408 Biflex units which had a very pleasing sound. They were reconed but genuine replacement cones were no longer available and their performance never came close to that of the originals.

 

[highfigh]

The friend whose speakers had to be reconed did not have to get the magnets re-magnetized. The speakers were 8 inch Altec 408 Biflex units which had a very pleasing sound. They were reconed but genuine replacement cones were no longer available and their performance never came close to that of the originals.

If they still have the speakers, some of the old Altec employees are now at a new company that has cones made to original spec. Re-magnetizing AlNiCo speakers was the common practice and it's included at Great Plains, for no added charge.

https://greatplainsaudio.com/services/

 

[Verdinut]

If they still have the speakers, some of the old Altec employees are now at a new company that has cones made to original spec. Re-magnetizing AlNiCo speakers was the common practice and it's included at Great Plains, for no added charge.

https://greatplainsaudio.com/services/

I know GPA have had recone kits but not for the 408's. Those speakers were most likely discontinued in the late 1950's. They had been designed for home use and then replaced by the 755 Pancake drivers which were developped by the affiliated Western Electric and far from being as good.

 

[Philnick]

Face the speakers toward each other- if the bass disappears, one of the amps is reverse phase. This can be verified by turning one of the speakers away from the other and hearing the bass return.

Great idea!

 

[highfigh]

No, the high current draw lasts only a fraction of a second, not long enough to cause a fire.

When I started working at a stereo store, one of the guys had a great answer for the question of "Will these handle 100Watts?"- he would say "Yeah, sure- 100W? They'll handle that. Once.".

 

[highfigh]

Great advice!

It's a matter of push-pull, netting little bass energy going into the room.

 

[Philnick]

Had a hard time re-locating this thread to post my ultimate findings.

My electronics engineer best friend brought over his oscilloscope and we compared the outputs of one channel of each of the two AVRs (a Yamaha and a Denon) playing a mono signal.

They were in phase, so everything is working fine. (If they were out of phase, I would have swapped the cables out of sight up on the ceiling so that a visiting friend wouldn't see the phase swap at the equipment and "help me out" by "correcting" it.)

Silly side note: in building the room, while the outer layer of all the walls was done but not the inner layer - including of the ceiling - I ran all the speaker cables along the ceiling and down the walls, and told the guys putting up the inner drywall to make a hole at each of the speaker locations and pull the end of the cables through, so I could mount the wiring plates.

They forgot at the location for the surround left speaker. My engineer friend found the lost wire behind the wall by connecting a square-wave generator (which puts out a lot of out-of-band energy) to the other end of that cable and sniffing its signal out with a "Hello Kitty" AM transistor radio! I'm going to print out a picture of that radio and put it on the wall there as a memento!

 

[highfigh]

Is it enough to do this test on the secondary AVR? It would be tricky to test the primary one, since it would be uncertain whether the stuff decoded from HDMI and the line input (which isn't what I would be using for Atmos) are treated the same.

Perhaps the simplest would be to play a mono source through all channels and compare the outputs of the 2 amps.

At the Yamaha, I could Y a signal into a stereo line input and set it to "all channel stereo." Then I'd X/Y into the scope the red terminals of one speaker output from each AVR to see if they are in phase.

PS Very informative graph, by the way. I remember putting a discarded scope I'd found on campus across the two channels of my stereo, nearly 50 years ago, and watching the patterns made by music. Fascinating, when in the right state of mind!

PPS I also have a SmugMug gallery, but it's of my landscape photography, at Photos.PhilOlenick.com. It's quite small so far - only two dozen shots.

You don't combine signal with a T cord, you split the output of one jack to two.

If you want to see the phase of the output, download a tone generator app and an oscilloscope app- you can't usually use two apps on one phone, so use a second for either app and start them. Set it to 50-100HZ and check the output of a source- if the signal starts in a negative direction, it has inverted the signal. Do the same for the AVRs.