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      11-13-2014, 06:11 PM   #1
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Active Front Stage - Speaker Polarity

I'm sure it's no secret when I tell you that individual speaker polarities, especially in an all-active system, need to be "tweaked" in order to provide the foundation for a good sound stage.

"Polarity" refers the connection of the positive and negative speaker terminals to the respective amp outputs. "Normal Polarity" means + goes to + and - goes to -. "Reverse Polarity" means + goes to - and - goes to +.

It is an absolute myth that in the car you always have to hook speakers up in normal/correct polarity. This is only true at home, or whenever the listener is equidistant to both speakers, or speaker sets. In the car, there are a lot of crazy things happening that affect the way the signals are received by your ears, but the main problems are the distances between the speakers and the listener, and reflections.

So I just completed an all-active set-up in my car. All-active means that every speaker has its own amplifier channel, i.e. there are no passive crossovers used. I hooked all speakers (tweeters, mids, woofers, and sub) up in normal polarity and let the MS-8 do its thing. The result? - Pure ear poop. Terrible imaging, low impact, and just a "washed-out" sound. Some sounds, especially on the left side, sounded like they were an inch away from my ears, weird. I knew it was a phase issue right away. Phase is what allows you to locate sounds. If the location of the sounds are off, then it is probably a phase-related problem. Phase can be corrected/improved by switching polarities of individual speakers. Unfortunately, it often is a pure guessing game to know which speaker needs to have its polarity reversed in order to improve the phase response. So I picked the driver's side tweeter as a starting point, re-did the MS-8 calibration, and bam! Now the imaging was much improved, the singer was centered, and focused, and all sounds had their correct place on the sound stage.

Next the lack of mid-bass impact. I had never had this problem before, at least not due to phase. In the past, the midranges and the woofers were always hooked-up in the same (normal) polarity. Never had any problems. This time however, I have different midranges installed that can play a lot lower than the ones in the past. I chose a crossover point of 120Hz which makes a world of difference compared to 160Hz, where I had it before. These mids (old school JBL goodness), really put out a lot of mid-bass and this caused a phase issue with the left side underseat woofer. So to correct it, I proceeded to reverse the polarity of only the left side woofer. Re-did MS-8 calibration, and BAM!

It goes against logic but the impact of the mid-bass is a lot tighter and sounds more defined with this configuration. I would have never guessed it.

So in the end, I have the following speaker polarity configuration:

FL Tweeter: Reverse
FR Tweeter: Normal
FL Mid: Normal
FR mid: Normal
FL Woofer: Reverse
FR Woofer: Normal
Sub: Normal

I will have to do some more critical listening but this may be the way to go. Since the OEM cabin speaker locations never change from car to car, I would think that you can transpose these settings from car to car, as long as the crossover points are similar or identical. I am using 65Hz 12dB/oct from the sub to the woofers, 120Hz 24dB/oct from the woofers to the mids, and 3000Hz 24dB/oct from the mids to the tweeters.

I am hoping this will help someone out there who is planning to do the same thing (go all active). If I find any more polarity-related tweaks, I will post them.
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      11-13-2014, 06:20 PM   #2
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Forgot to mention. After my install I discovered TWO polarity mistakes in the wiring, even though I thought I had done everything 100% correctly. I used the JL Audio app which has a very cool polarity checker function. I definitely recommend doing this for every install, no matter how sure you think you are that all the polarities are correct.
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      11-13-2014, 06:39 PM   #3
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This likely works for the individual.

Granted, I have a completely different setup than yours, and my crossovers are probably widely different.

In my case, the best impact for me was swapping the phase of the passenger side 4" speaker.

I then proceeded to swap the driver side tweeter. This provided some impact, but much less of a noticeable one compared to swapping the passenger side mid.


edit:
Mind you, playing with all these phases still cooks my noodle.

There's a few things to keep in mind, and I still forget about it.
There's the theoretical stuff like;
6 dB/octave = 90 degrees
12 dB/octave = 180 degrees
18 dB/octave = 270 degrees
24 dB/octave = 360 degrees
But that is only for electrical phases.

HOWEVER, how/when the sound hits our ear is another thing entirely, which is sort of like a relative phase.

With active setups, we need to keep BOTH of those types of changes in mind when we sort through EQ, phasing, delay, etc.

Last edited by Wongway; 11-13-2014 at 06:46 PM.
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      11-13-2014, 06:48 PM   #4
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What improvement did that make? Mid-bass and/or imaging? You don't know your crossover points?
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      11-13-2014, 07:25 PM   #5
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Quote:
Originally Posted by kaigoss69 View Post
What improvement did that make? Mid-bass and/or imaging? You don't know your crossover points?
It's been a couple of weeks since I last made adjustments, so I honestly don't remember my crossover points at the moment.
If I had to make a guess, I think I'm using a
12db/octave slope for the Tweets to Mids.
24db/octave slope for the transition from mids to midbass

Prior to flipping the phase of my 4" mid, I thought I had the sound fairly well centered. But something sounded 'off' for lack of a better term. Once I flipped that passenger mid, I realized what was 'off' was that I was experiencing a lot of cancellation.

The best description I can come up with to illustrate the experience;
Prior to flipping the passenger mid, it was as if all my sound was a series of spotlights aimed towards the center of the dash. A beam from each tweeter, a beam from each mid, etc.

After flipping the passenger mid, it was as if I had floodlights emanating from all my speakers. Suddenly, I was hearing all sorts of things I missed out on. Huge wealth of audio information I either didn't realize was there, or forgot was there.

Now, instead of a more focused sound, it actually got hard to center the image. There was just so much more audio information to sort through. It was as if the speakers sort of disappeared and now the sound was emanating from outside the physical confines of the car. As if they were coming from beyond the side mirrors.

I pretty much was forced to listen to mono source sound (AM radio) to help me recenter my image up front. Once I recentered everything, the vocal presence and overall stage got lifted up just above my dash.
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      11-14-2014, 06:19 AM   #6
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Wondering if there is any positive results for going 180 out of phase with the door mids/tweets for those that don't have a fully active system?

One thing that I have found is that I can get the most spl out of each sides underseat/mid combo playing a 200 hz sine wave when the driver underseat is 67.5 deg out of phase and the passenger underseat is 22.5 out of phase. The helix dsp allows these incremental phase adjustments.
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      11-14-2014, 08:25 AM   #7
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I also wanted to mention that I tried using the guide I found on DIYMA, which makes you run only like speaker pairs, i.e. Tweeters only or mids only, and then flipping the polarity of one side and listening for a shift of the image. I tried this with both the tweeters and the mids, and each time the image was exactly at the position of the driver side respective speaker, no matter what the polarity...
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      11-14-2014, 11:55 AM   #8
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Quote:
Originally Posted by cdgatti View Post
Wondering if there is any positive results for going 180 out of phase with the door mids/tweets for those that don't have a fully active system?...
I'm going to go out on a limb here and say "no"

Because a passive crossover is automatically doing it's adjustments for you depending on what it's factory setting is. If it came from the factory at X db/octave slope, it will automatically reverse or not reverse the polarity of the respective speaker.
(at least, I'm like 85% positive that's how most good passive setups work)

So throwing a pair 180degrees out of phase would probably screw up what that crossover is doing for you more than help.
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      11-14-2014, 06:39 PM   #9
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I'll have to go through my setup files and see where mine ended up at. I think we're pretty close on crossover settings except I'm pretty sure my tweeter is lower. I do remember changing polarity many, many times through out my many tweaking sessions.
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      11-14-2014, 07:36 PM   #10
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I tried that exercise too but polarity wise, it didn't result in me having any pairs out of phase from each other. I think my midbasses are out of phase from the rest of the system but each pair is in phase. Crossover points and slopes play a lot into this as well. Each parameter affects the overall system differently.

For me, I've never been able to get my midbass and sub to play well together. Its always one is good and the other disappears. It seems like there is a cancellation somewhere in the lower midbass/upper bass region but I can't figure out how to tune it out. Been trying all kinds of things for years now. I pretty much gave up.
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      11-14-2014, 07:48 PM   #11
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Quote:
Originally Posted by 808MGuy
I tried that exercise too but polarity wise, it didn't result in me having any pairs out of phase from each other. I think my midbasses are out of phase from the rest of the system but each pair is in phase. Crossover points and slopes play a lot into this as well. Each parameter affects the overall system differently.

For me, I've never been able to get my midbass and sub to play well together. Its always one is good and the other disappears. It seems like there is a cancellation somewhere in the lower midbass/upper bass region but I can't figure out how to tune it out. Been trying all kinds of things for years now. I pretty much gave up.
I don't remember, do you have your sub installed in a corner enclosure? If yes, I used to have the same issues with that set up. Running the sub in reverse polarity definitely helped me, but it was never perfect. With the subwoofer firing through the ski pass, it is easier to integrate. Also, having variable phase control on my sub woofer amp definitely helps.
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      11-14-2014, 08:02 PM   #12
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Quote:
Originally Posted by 808MGuy View Post
I tried that exercise too but polarity wise, it didn't result in me having any pairs out of phase from each other. I think my midbasses are out of phase from the rest of the system but each pair is in phase. Crossover points and slopes play a lot into this as well. Each parameter affects the overall system differently.

For me, I've never been able to get my midbass and sub to play well together. Its always one is good and the other disappears. It seems like there is a cancellation somewhere in the lower midbass/upper bass region but I can't figure out how to tune it out. Been trying all kinds of things for years now. I pretty much gave up.
I think that unwittingly, my choice in not having a dedicated subwoofer might have saved me a ton of headaches in this regard. Kaigoss did bring up an interesting point however...

I know my particular amp can let a subwoofer's phase vary from 0-360 degrees. (and any number in between) Does your amp have a similar capability? If so, that could probably help tremendously.
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      11-14-2014, 09:51 PM   #13
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Quote:
Originally Posted by kaigoss69 View Post
I'm sure it's no secret when I tell you that individual speaker polarities, especially in an all-active system, need to be "tweaked" in order to provide the foundation for a good sound stage.

"Polarity" refers the connection of the positive and negative speaker terminals to the respective amp outputs. "Normal Polarity" means + goes to + and - goes to -. "Reverse Polarity" means + goes to - and - goes to +.

It is an absolute myth that in the car you always have to hook speakers up in normal/correct polarity. This is only true at home, or whenever the listener is equidistant to both speakers, or speaker sets. In the car, there are a lot of crazy things happening that affect the way the signals are received by your ears, but the main problems are the distances between the speakers and the listener, and reflections.

So I just completed an all-active set-up in my car. All-active means that every speaker has its own amplifier channel, i.e. there are no passive crossovers used. I hooked all speakers (tweeters, mids, woofers, and sub) up in normal polarity and let the MS-8 do its thing. The result? - Pure ear poop. Terrible imaging, low impact, and just a "washed-out" sound. Some sounds, especially on the left side, sounded like they were an inch away from my ears, weird. I knew it was a phase issue right away. Phase is what allows you to locate sounds. If the location of the sounds are off, then it is probably a phase-related problem. Phase can be corrected/improved by switching polarities of individual speakers. Unfortunately, it often is a pure guessing game to know which speaker needs to have its polarity reversed in order to improve the phase response. So I picked the driver's side tweeter as a starting point, re-did the MS-8 calibration, and bam! Now the imaging was much improved, the singer was centered, and focused, and all sounds had their correct place on the sound stage.

Next the lack of mid-bass impact. I had never had this problem before, at least not due to phase. In the past, the midranges and the woofers were always hooked-up in the same (normal) polarity. Never had any problems. This time however, I have different midranges installed that can play a lot lower than the ones in the past. I chose a crossover point of 120Hz which makes a world of difference compared to 160Hz, where I had it before. These mids (old school JBL goodness), really put out a lot of mid-bass and this caused a phase issue with the left side underseat woofer. So to correct it, I proceeded to reverse the polarity of only the left side woofer. Re-did MS-8 calibration, and BAM!

It goes against logic but the impact of the mid-bass is a lot tighter and sounds more defined with this configuration. I would have never guessed it.

So in the end, I have the following speaker polarity configuration:

FL Tweeter: Reverse
FR Tweeter: Normal
FL Mid: Normal
FR mid: Normal
FL Woofer: Reverse
FR Woofer: Normal
Sub: Normal

I will have to do some more critical listening but this may be the way to go. Since the OEM cabin speaker locations never change from car to car, I would think that you can transpose these settings from car to car, as long as the crossover points are similar or identical. I am using 65Hz 12dB/oct from the sub to the woofers, 120Hz 24dB/oct from the woofers to the mids, and 3000Hz 24dB/oct from the mids to the tweeters.

I am hoping this will help someone out there who is planning to do the same thing (go all active). If I find any more polarity-related tweaks, I will post them.
Funny how a while back I mentioned this and You discredited my statements....
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      11-14-2014, 10:08 PM   #14
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No, my measurements were without a subwoofer present, playing the underseats down to the highest audible frequency before the natural roll off (40hz). When you are crossing them at 65hz, and having a subwoofer present, it is a totally different ball of wax.
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      11-15-2014, 01:32 AM   #15
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Quote:
Originally Posted by Wongway View Post
I think that unwittingly, my choice in not having a dedicated subwoofer might have saved me a ton of headaches in this regard. Kaigoss did bring up an interesting point however...

I know my particular amp can let a subwoofer's phase vary from 0-360 degrees. (and any number in between) Does your amp have a similar capability? If so, that could probably help tremendously.
No I don't have continuously variable phase on my sub amp or my PS8 but I have fooled around with TA. It helps a little bit but I can never get it just right. I do have a corner loaded sub but I use the trunk space too often with the seats down to try an IB setup so I've just learned to live with it. I probably only have 1 more year with this car anyway so I'm not going to invest much more time and money into it.
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      11-18-2014, 03:09 PM   #16
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Update: Did some more testing today. By flipping polarity of the right side mid-bass, and the sub, I was able to get even better results (= least amount of cancellation).

So now this is what I have done:

FL Tweeter: Reverse
FR Tweeter: Normal
FL Mid: Normal
FR mid: Normal
FL Woofer: Reverse
FR Woofer: Reverse
Sub: Reverse
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      11-18-2014, 03:49 PM   #17
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so excluding one tweeter what we see is that your door mids work best when out of phase with the rest of the system. As I recall you have them angled in the door panel right?

Are you calibrating with the MS-8 after you do these phase swaps? I remember Andy saying the MS-8 does not check phase, it just assumes everything is in phase and then does time alignment and EQ and that pretty much corrects everything anyway.....but if something is out of phase it may have a lot of work to do do correct it, and even then it will only be possible to a point....

Also with regards to phase...Im wondering also if the phase of your mids is not inadvertently swapped somewhere (like in the amp or the speakers themselves), Im wondering if you checked phase to each channel individually if you would not find the mids were backwards... Or maybe its the angle, on axis vs. off axis....

Trying to get my head around how the MS-8 is working with what you are doing.


As a separate point....back in the old days (pre DSPs), the beginning of any high end system started with playing with speaker placement, angles, and phase, trying to get image and tonality "naturally" as close to perfect as we could, before we started playing with delays and EQ. Now days DSPs mask a lot of this as they auto correct for a lot, but makes me wonder if there isnt something being left on the table....
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Last edited by jeffb335; 11-18-2014 at 03:57 PM.
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      11-18-2014, 04:37 PM   #18
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Hi Jeff, I wish I would have checked polarities with the door panels off, that would've been a lot easier. For now I am stuck with using an app for that. The MS–8 can only correct minor phase problems, at least that has been my experience. Phase correction prior to calibrating is therefore very important. Anytime I make any such change, I recalibrate.
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      11-18-2014, 04:54 PM   #19
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Thinking back to when I set up my system I recall that I did some back and forth phase testing on my underseat woofers to get them correctly phased with my door mids. Between the MS-8, the amps, the crossovers and the wiring I figured there was no sure way to know if they were in or out of phase so I just did it by ear, confirmed with RTA...

And then I did the same between the underseat woofers and my trunk sub (but I ALWAYS do that)

So the moral of the story? Phase matters....A LOT....
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      11-18-2014, 05:13 PM   #20
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Oh, and the new mids are in straight!
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