Monday, September 8, 2014

My recent adventure down Phase Lane: In Phase or Out of Phase?

Over the last month or so I have been listening to a few different set up and trying to pin point what set I wanted to build my home theater around. One set is from a well known manufacturer that that people tend to love or hate and the other from a lesser known manufacturer who has had some significant online sales of the past year or so. However, this entry isn't about a comparison between the two. This is about my experience in messing around with the phase of one of these two sets of speakers.

I found one of the pairs of speakers to be VERY muddy sounding, which when reading other professional reviews, was never a criticism of the speakers. So I wanted to start some technical tests and investigate what was going on. All of the following graphs and experience comes from an real world, untreated room. So there will be reflections and some natural room issues.

Below (graph #1) is the in room frequency response of a single of the speaker @ 1 meter. Right away the results seem to correspond to what I was hearing, a big ugly wide hump @ 150hz with everything else being acceptably flat.

Next up (in graph #2 below) was the 2.0 set up at the listening position. This is where it got really ugly, like WTF kinda ugly. This graph was unlike any that I have seen with other speakers in the same room, under essentially the same testing condition. I huge sharp dip @ 90hz; with a peak at 250hz that gradually trails off at we reach 20khz. This is were I realized I was seeing and hearing something not right. But it better explained why these speakers sounded muddy and without an detail; and absolutely not harsh or bright like they sometimes are criticized for being. I didn't know what was going on, so for nothing more than shits and giggles I switched phase on just one speaker. I remember my time in car audio and people expounding on the virtues of switching the phase on a tweeter in a component set, so I thought, maybe just maybe it will makes a difference.

This (below in graph #3) was the result. With one speaker out of phase the graph changed yet again, and this time for the better. Still a little more wavy than I would like, but finally they didn't sound so muddy and the detail and brightness came back. They sounded much more like they should have.

My first worries were it either a speaker was internally wired out of phase or that my amp was crossed some how. I triple and quadruple checked that I hadn't crossed my wires when I put on the terminal ends and that were good. Having 3 of these speakers already (used as the front 3 in a 5.1 system) I round robin tested them all. Both rotating them into position and rotating them in and out of phase and amp output A or B, the graphs always returned something very near identical. If both speakers were in the same phase, it looked and sounded like graph #2, if either speaker was out of phase with the other it looks like graph #3. 

That being the case, to the best that I can gather, this is just very weird situation that seems to be isolated to this set of speakers as they are set up in my room. At some point later I will continue my complete technical and listening review of these speakers.

Anyone got any ideas? I tried to do a little googling about phase issues, and I didn't really see anything about switching the phase on just one speaker.

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