fine tuning sound

I have a set of door speakers that are run through a pair of fourth order crossovers I built for them. I also have speakers mounted in my headrests with no crossovers (factory, '96 Miata). I've read that fourth order crossovers have a 360 degree phase shift. Now, usually people just consider this no phase shift, but when running with another set of speakers, would the 360 degree phase shift affect the time delay on the door speakers? Would the door speakers be playing everything 360 degrees after the headrests that are not run through a crossover? If so, what kind of additional millisecond delay would that translate to adding into the headrests to bring everything back on the same phase? Also, there are a couple of settings I need help with on the amplifier. The amp (Eclipse 3122) has a subsonic filter adjustment on it. I was wondering what is a good setting for it in my case. The manufacturer's specs on the door speakers are a low frequency limit of 50hz. Should I set the subsonic to 50hz, or should I set it even lower because even though below 50hz may not be audible from the speakers, it still plays through the speaker and adds feeling and depth to the bass. I also am not sure on what a setting on the lowpass section of the amp crossover does. I'm fairly sure I have it set to just not do anything to the sound since I have the highpass/lowpass switch set to "through", but next to the lowpass adjustment there's a switch labeled x1 or x30. I don't think this does anything for me anyway since it's not set on lowpass, but what is this switch's function?

Sad, little man wrote: I've read that fourth order crossovers have a 360 degree phase shift. Now, usually people just consider this no phase shift, but when running with another set of speakers, would the 360 degree phase shift affect the time delay on the door speakers?

No. The high pass section has a +360 degree shift, and the low pass section has a -360 degree phase shift, so the speakers are in phase with one another AT THE CROSSOVER POINT. Due to the location of the headrest speakers, and how close to your ears they are, it will be quite difficult to adjust any time delay on the doors. Also, if you are running ALL of the speakers off two channels of amplification, you will not be ABLE to adjust the TD for the door speakers. To do this, discrete amplification channels (a dedicated channel to EACH driver compliment) are demanded.

Sad, little man wrote: Would the door speakers be playing everything 360 degrees after the headrests that are not run through a crossover? If so, what kind of additional millisecond delay would that translate to adding into the headrests to bring everything back on the same phase?

See above...

Sad, little man wrote: Also, there are a couple of settings I need help with on the amplifier. The amp (Eclipse 3122) has a subsonic filter adjustment on it. I was wondering what is a good setting for it in my case. The manufacturer's specs on the door speakers are a low frequency limit of 50hz. Should I set the subsonic to 50hz, or should I set it even lower because even though below 50hz may not be audible from the speakers, it still plays through the speaker and adds feeling and depth to the bass.

That will depend on your individual installation, and the capabilities of that speaker system WHILE INSTALLED IN YOUR DOOR. I'd start around 50Hz, and if they don't flap at all, even as loud as you might ever turn it up, go a little bit lower. Still no flap? A little lower still. That's the way I'd tune it in, other may have different ideas.

Sad, little man wrote: I also am not sure on what a setting on the lowpass section of the amp crossover does. I'm fairly sure I have it set to just not do anything to the sound since I have the highpass/lowpass switch set to "through", but next to the lowpass adjustment there's a switch labeled x1 or x30. I don't think this does anything for me anyway since it's not set on lowpass, but what is this switch's function?

You'll leave it in the setting you already have it in... That is for using the amplifier in a dedicated subwoofer installation, where you only want that woofer to play UP TO whatever frequency you have it set at.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

haemphyst wrote: No. The high pass section has a +360 degree shift, and the low pass section has a -360 degree phase shift, so the speakers are in phase with one another AT THE CROSSOVER POINT. Due to the location of the headrest speakers, and how close to your ears they are, it will be quite difficult to adjust any time delay on the doors. Also, if you are running ALL of the speakers off two channels of amplification, you will not be ABLE to adjust the TD for the door speakers. To do this, discrete amplification channels (a dedicated channel to EACH driver compliment) are demanded.

So, it's not a problem that the tweeter is 720deg ahead of the woofer? I guess ideally with the tweeter closer to your head you would want it to be delayed behind the woofer, but you're right, I can't delay that. I have the door components hooked up to the front two channels, and the left and right headrest speakers on the left and right rear channels respectively. Going off of the owner's manual for the Alpine, I don't see why it'd be so difficult to set it up so at least the headrest speakers and door components as a whole are delayed correctly with respect to each other. I took some measurements, and the headrest speakers are both about .127m away from my ears, so those are like the two rear speakers. I chose points on the door panels that were about equidistant from the woofers and tweeters, and on the left that's .889m from my head, and on the right it's 1.194m (I originally measured in inches, but the manual does the calculations in meters, so those are converted.) So if we take the right door speaker minus the left door it's .305m different. According to Alpine, .305/343x1000 (343 being speed of sound in m/sec) means the front left should have a .88 millisecond delay (.9 is the closest I can get). Then the headrest speakers get the same delay since there's one on each side of the headrests that are the same distance from my head. The 1.194m front right distance minus the .127m gives 1.067m. 1.067/343x1000 gives a 3.1 millisecond delay for those. Is all of this about right? So the FL should get .9ms delay and both rears should get 3.1ms? Thanks for the help on the subsonic filter too, but maybe I have a misconception about what it's supposed to do. It's my understanding that it's there so that the amplifier doesn't waste any of its power generating tones that the speakers its driving won't be able to play anyway, and it can use the power saved to drive the speakers to a higher volume without clipping, but does it really save the amp any work the higher it's turned up?