Loudspeaker polarity

That seems to be the general rule, tho some loudspeaker manufacturers - notably JBL - have in the past been known to wire their cabinets the opposite way so that + on the input socket produces - at the bass driver. Also some cabinets are wired with the horn driver in opposite polarity to the bass driver.

Ron

I've always used this convention.

It would probably be safer to say, away from the magnet, just in case the driver is reverse mounted in an enclosure or used in a isobarik design. Knowing the DC movement may have little bearing on the AC movement at any paticular time.

greg

Also some cabinets are wired with the horn driver in opposite

That is because some crossover topologies require this to be the case. Connecting the horn with the same polarity of the bass driver would result in a Null at the crossover frequency.

Gareth.

There were many speakers that had inverted polarities on the tweeter. You would not get a total null. Often there was a choice of -3 db or + 3 dB. Neither were a good choice.

You have to know the phase at whatever frequency its at, plus the crossover effects. Some speakers make use of this and use the falling or rising phase of the driver along with the crossover characteristic. And, your usually assuming your on axis, but not always.

greg

I was told--way back when--that reversing the polarity of the middle driver in a three-way system 'could' smooth out the response. As you say, it's a tossup; but in many cases I found it to be true. In my understanding (without doing actual measurements) it was always to reduce the level in the area where the drivers in the system overlapped in response. IOW, instead of reinforcing each other in that area and producing a hump in response, the anti-phase component would negate it.

jak

If I recall correctly, this is due to the phase-shift/delay characteristics of certain types of crossover.

I'm working from hazy memory here, but here's how I recall it: in theory, a second-order crossover circuit (low-pass or high-pass) introduces a 90-degree phase shift in the signal delivered to the load, at the point at which the output to the load is 3 dB down from full scale (the nominal crossover point). The phase shifts are in opposite directions for low-pass and high-pass crossover elements. Hence, if you use second-order crossover, and wire the drivers "in phase", the signals to the drivers will actually be 180 degrees out of phase at the -3 dB crossover point. Instead of summing to deliver full power, they'll exactly cancel, resulting in a deep notch in the frequency response.

By inverting the wiring to one driver or the other, you ensure that the driver outputs are actually in-phase at the crossover frequency and sum correctly rather than adding.

This theoretical analysis is, of course, muddied up in practice by the nasty details of physical reality. It assumes that the drivers are presenting purely resistive loads to their crossovers (uncommon unless you've added a Zobel), that the drivers themselves aren't adding any phase shift to the signal, and that their acoustic centers are aligned so that their waveforms aren't being phase-shifted due to physical offset (and this, again, is not the common case).

So, in practice, whether a two- or three-way system using second-order crossovers will have a flatter frequency response or a better over-all sound with "in-phase" or "out-of-phase" wiring of the drivers will depend very much on the specifics of that speaker system... the drivers, crossover, and physical mounting of the drivers (and probably a dozen other factors as well).

You NEVER want a peak in the 1-3 kHz area. Makes for a harsh speaker. Polarities usually make a big difference in the sit down stand up test.

greg

Indeed

Ron

One thing not mentioned, time delay. A long horn is going to shift the center line. So will the vertical axis.

greg

Also if you reverse polarity to the speakers you will have less dust accumulate on the grille. Be sure to reverse both channels to preserve proper phasing.

And protect your cat from being sucked into the boxes.

Regards, H.

Hi Dave, in this case your memory is still good.

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