Expert help on phase issue with Sony Car CD?

[shovel99]

Hi Folks,

I have been wrestling with getting decent midrange from the front door speakers in my Toyota Highlander.... from the day I installed a Sony CD player about 2 years ago. I have been blaming the speakers, and have been through at least 20 sets of all the major brands, as well as some home audio drivers from some of the best makers.

Several times I have suspected that I inadvertently reversed one of the front door speaker polarity.... and did the switch and listen for bass response test (one should almost completely cancel if out of phase/polarity) I was surprized that there wasn't a whole lot of difference in bass response either way (to my ear either at the driver position or placing my head over the console. )

Yesterday, after at least the 200th time of yanking the fronts out and replacing them with another set.... screaming and throwing large objects... I brought up a bookshelf speaker for the phase test. I connected the bookshelf speaker to the left front door leads and set the speaker 1/2 inch from the right front car door speaker. With the balance centered, the difference in bass was INDISTINGUISHABLE!

If I did this with a home theater amp/receiver, there would be almost 100% cancellation with leads out of phase. If car receivers are just like home receivers, this test should be proving that the head unit is faulty and I have wasted...oh... 1,000 hours and at least $1500 on car speakers instead of replacing it.

This seems pretty conclusive that the unit is somehow faulty. There is a fabulous sale on an upgraded unit with 7 band EQ and time phasing... both of which can help solve phasing issues in car audio... and I am inclined to swap it out just for the upgrades, bu don't want to blow another $250 it this isnt the problem.

Can anyone shed light on this?

Thanks, shovel99

shovel99

[Wolf]

If you were in the driver's seat when listening this makes perfect sense. It has to do with the time-domain of the speakers physical position and where you were seated. If the distance from the left apeaker to your left ear equals the distance of the right speaker to your right ear, in-phase or normal polarity is 'correct'. Changing these to be different distances means that a flip of one of the polarities MAY make the time domain more in-phase than it was prior for the listener.

It depends on the listener, the distances, and the preferences. I preferred the polrity the same on my doors in the last car I had.

I hope that clears things up,
Wolf

[shovel99]

If you were in the driver's seat when listening this makes perfect sense. It has to do with the time-domain of the speakers physical position and where you were seated. If the distance from the left apeaker to your left ear equals the distance of the right speaker to your right ear, in-phase or normal polarity is 'correct'. Changing these to be different distances means that a flip of one of the polarities MAY make the time domain more in-phase than it was prior for the listener.

It depends on the listener, the distances, and the preferences. I preferred the polrity the same on my doors in the last car I had.

I hope that clears things up,
Wolf

Thanks wolf, for the added thoughts. I am aware of the cancellation due to the difference in sound path from the two drivers, and have actually tested this phenomenon with soundeasy.

The curious issue reported here, today, is the test that I conducted not producing a pure 180 degree null. I will say it again. There is almost as much bass coming out with either hookup + - and - +. Very curious.

In the 70's I "created" a rear center channel on a stereo amp by connecting a speaker from + left to + right, so ambience was the difference between the two.

I am wondering if the installer somehow criss crossed front left and right to do that. I can't quite picture that. The volume control shifts completely and accurately from L to R.

I may just have to buy the unit with 7 band EQ to fix the 400hz hole... and with the time delay for position.

Thanks again.

shovel99

[shovel99]

Hi Wolf and others who may be listening in.

As I was tweaking the XO values on the front speakers... now thinking they are in phase.... it occurred to me that the bass cancellation may not have been complete with the bookshelf system facing the other driver still door mounted... because some bass was escaping into the door and finding alternate paths around the car... as would be the case with any bass from and car door that does not have the gap between the door mounting scosche mounting brackets and the inner trim panel. The bracket has been fattened with a 1/2 inch spacer I made, but still some gap, and waves are rolling behind the trim panel.
Both the front of the inner door panel and the door side have been dynamatted.. so behind the woofer is reasonably sealed. But a wave from the front of the speaker is making the rounds. I probably need to cut out the plastic "grille" in the trim panel, extend the mounting bracket enough to bring the woofer forward flush with the panel, and mount a nice transparent grille, but have wanted to retain factory stock for resale.

Just thinking....

shovel99

[cliffburge]

That is very curious.... you should be able to hear a real difference if you put left and right speakers near each other and play with the polarity, I have never had a time that I could not tell a definite difference flipping the polarity back and fourth, one way would always have a LOT more bass. I worked in car stereo for a number of years, and when I could not remember wire colors for say the rear speakers that is how I would determine how to hook it up (polarity wise).

You do not have a crossover turned on do you??

By the way, an outboard amplifier ALWAYS sounds better than the deck power, even if it is the same power as the deck onboard amp.....

Maybee you could hook up some other source of signal (home reciever, small stereo with speaker outputs...) to your car speakers and give a listen and see if you get some of the mid range sound that you wanted...that would help you decide if you need a new deck or not....


There is my 2 cents....


Cliff

[shovel99]

Cliff, that is an excellent idea... hooking another amp up to the car speakers. I have a couple of theater previous units I could drag up to the garage, except that they weigh a ton, of course. It would prove that another amp... at least without any eq... sounds better. I could also repeat the bookshelf to door installed unit experiment... and see if I get the same bizarre results. I could also conduct the same test with the door panel off.. . so I can get the bookshelf speaker closer to the door driver. But as you may imagine.. several years, thousand+ dollars and 20 sets... over a hundred,maybe more times with the doors panels off and speakers out... I am really tiring of this process. It used to be so easy to improve car sounds with a deck which you could install yourself ... open dash underneath, and rear deck speakers. It is all so incredibly maddening now.

Thanks, Paul

That is very curious.... you should be able to hear a real difference if you put left and right speakers near each other and play with the polarity, I have never had a time that I could not tell a definite difference flipping the polarity back and fourth, one way would always have a LOT more bass. I worked in car stereo for a number of years, and when I could not remember wire colors for say the rear speakers that is how I would determine how to hook it up (polarity wise).

You do not have a crossover turned on do you??

By the way, an outboard amplifier ALWAYS sounds better than the deck power, even if it is the same power as the deck onboard amp.....

Maybee you could hook up some other source of signal (home reciever, small stereo with speaker outputs...) to your car speakers and give a listen and see if you get some of the mid range sound that you wanted...that would help you decide if you need a new deck or not....


There is my 2 cents....


Cliff