Mike P

I've replaced the stock speakers in my scooby with infinities front and back. (front:605cs, rear:652)

Whilst fiddling around during fitting, I reversed the phase of the rear pair with respect to the front pair. For some reason I seem to get more bass response this way round, as compared to the "correct" wiring. I've got a multimeter, and I've checked the pairs are definitely out of phase.

I'm intrigued by this, 'cos it flys in the face of what I've been told about audio. Has anyone else tried it, and is the effect due to the shape of the cabin and the way the sound reflects around it?

chiark

It doesn't fly in the face of what you know; the time difference between sounds arriving from the front speakers and the back speakers is such that the bass is being augmented. Think about the speaker wave being out of phase, so the positive peak of the front speakers is aligning with the delayed out of phase positive from the rears which followed the negative.

If you see what I mean.

I'd draw a picture, but I'm no use at ascii art

Mike P

No need for the ascii art, chiark, I understand what you mean.

Do you know if Subaru wire out of phase as standard? I wonder if people are missing out on performance if they just do a speaker swap

twinny

I was thinking the same thing. Would you actually recommend changing the phase on the rear speakers?

Mike P

Twinny, I reckon it's worth giving it a go.

If I remember rightly you've got component speakers at the front so you could swap the polarity of wires at the crossover input on the front pair. Haven't seen photos of your complete setup, so maybe you'll have an easier place to reverse the phase on the front or rear pair.

It doesn't take long to, and I noticed a definite improvement in the amount and punchiness of the bass, plus the sound image seemed to surround me better, although that was more subtle.

twinny

Yeah, I do got component speakers up front (I've said to to many times now as people is starting to remember it ;-).. But the crossovers are in the doors, so the easiest for me would be to switch the cables at the amp I think. Thanks for the tip! I'll try it out!

chiark

Phasing is a mystery art. In an astra, having one tweeter out of phase with the rest of the system improved things no end. Having a mid out of phase can help too.

Just try and see what's best. There's no rule unfortunately, but DON'T believe that in-phase will necessarily give you the best always. It's a good starting reference point.

kryten

The only way to get the phasing spot on is by using some sort of time alignment.

The cheaper way involves you spending several hours changing the polarity for each of the components in turn and making notes while listening to music you know/like.

Then you can find a couple of 'best' settings and compare them.

chiark

<plug for Kryten>Kryten, you don't know anyone selling a really good time alignment unit do you? </plug>

nom

The bit I've found to look out for with phasing it that it might sound very nice for you... but awful for eveyone else
I tried the rear ones out of phase, and it worked very well if I put my head right back against the seat, but the bass completely disappeared if I moved forwards a bit. Very odd sounds everywhere except in one precise place.

For checking phasing, I'm one of those who thinks that the best testing mechanism is the listening mechanism, i.e. the ears , try and pick up a cheap electronic crossover - well, I suppose this only works if you have an entirely active system, with lots of amp inputs, but works with passive stuff to a point as long as you have the seperate amp inputs. Anyway, with a bit of extra cabling, you can (temporarily) have the active crossover thingy sitting next to you in the front of the car and fiddle with the phase, levels, crossover points etc. which you can then dial back to the original system.
Well, I enjoy fiddling with it anyway Got very good results fairly cheaply (the x-over was £70 and has lasted me 4 cars so far).

kryten

Well, nick, now you mention it http://www.scoobynet.co.uk/bbs/threa...hreadID=104411

If you want the system to sound good for all occupents then TA isn't the way to go. You set it up for a specific point (you!) and everywhere else sounds kak.

It is possible to get a system that sounds good from both seats, with excellent imaging using phasing, EQ and a lot of hard listening. BUT I paid for the bloody system, so why should I care what anyone else thinks!

The listen/tweak/listen thing is still applicable to TA based systems as the right theoretical settings (ie measured) don't always sound best.

What I would suggest is people try by ripping a few of their favourite tracks onto their PC. Then calculate the delay to add to the RIGHT channel to perfectly TA it (0.1ms for every 3.54cm difference in path length, if memory serves me correctly). Run a sound morphing prog that will let you apply this delay and burn a CD with the original track and settings of perfect and then 0.1 and 0.2ms either side of perfect.

Then take the CD and a mate to the car, get them to randomly select tracks, noting the number and make your notes on the sound.

Straight after doing this, I bought the TA system!!