Polk DB 351 Polarity C5
Thread Starter
Advanced
Joined: Mar 2017
Posts: 88
Likes: 2
From: Gulfport MS
Polk DB 351 Polarity C5
Is there a consensus on the correct connection of the Polk DB 351 in the door of a C5? Some say just drop them in and use the plugs you get from Crutchfield. Some say you need to cut them and reverse the polarity.
Safety Car
Joined: Mar 2016
Posts: 3,534
Likes: 432
From: Atlantic Beach FL.
It's not the polarity that gets reversed it is the connectors. The Bose speaker has the small spade connector on the positive terminal and aftermarket speakers have it on the negative terminal. The actual polarity stays the same. There has been a lot of misinformation posted regarding this.
The Polk db 351 is on the left and the Bose is on the right. See the size of the connectors. I know that there is a adaptor harness for the rear speakers (made by Metra) but I haven't seen one for the fronts on a C5. I think Crutchfield may be confused about this.
The Polk db 351 is on the left and the Bose is on the right. See the size of the connectors. I know that there is a adaptor harness for the rear speakers (made by Metra) but I haven't seen one for the fronts on a C5. I think Crutchfield may be confused about this.
Last edited by Rob 02; May 20, 2017 at 01:39 AM.
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
look at the polk. it's marked + -
see which way the cone moves + to + and - to - battery to speaker
when the other speaker moves the same way you know what's what
if the cone goes the other direction you're backwards
see which way the cone moves + to + and - to - battery to speaker
when the other speaker moves the same way you know what's what
if the cone goes the other direction you're backwards
Drifting
Joined: Nov 2016
Posts: 1,820
Likes: 411
From: Somewhere in the middle of Kansas
Never used a 9volt but an old salty installer showed me that trick about 30 years ago with a 1.5V D battery. It's how you can either find or ensure polarity of your speakers. Positive lead on positive lead of battery, negative lead on negative lead of battery and your speaker cone will move forward and make a slight thump and the cone will hold in the outward position until you break connection. I always double check my polarity before firing everything up cause if you have ever heard a system out of phase on one side it is all sorts of FUBAR.
There is sometimes merit to putting a subwoofer out of phase though.....
Last edited by 02BlownZ06; May 22, 2017 at 09:28 AM.
Safety Car
Joined: Mar 2016
Posts: 3,534
Likes: 432
From: Atlantic Beach FL.
Crossovers can change the phase and the distance from the sub-woofer can cause a perceived phase shift where the polarity needs to be reversed to compensate.
A bass blocker/ capacitor will cause a 90 deg phase shift and a passive low pass filter will have a 90 deg shift requiring reverse polarity to compensate. There are exceptions and entire books are written just on crossovers.
A bass blocker/ capacitor will cause a 90 deg phase shift and a passive low pass filter will have a 90 deg shift requiring reverse polarity to compensate. There are exceptions and entire books are written just on crossovers.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
phase sweeps across a drivers range. in fact, here's a picture of a 10w6v3 phasing. green is ported, yellow is sealed. crossovers and enclosures can affect phase
with car audio and the subwoofer phase you literally just listen to it both ways and see what sounds better to you.
all is not lost however. most good speaker makers realize this and tune their speakers for expected phase shifts. better home audio speakers can do this with the crossover and enclosure. car audio is much harder since most mids are infinite baffle and they produce the lions share of the octaves of sound. . a sub is best case 20 to 80hz that's 2 octaves. that mid however. it does at 5 or more in most cases and only the really high end gear comes in slightly under that with a tweeter taking over before 2.4khz, the tweeter is we will say for arguments sake 2.4, so 2.4 to 4.8 is one, 4.8 to 9.6 is two and 9.6 to 19.2 is 3 making 8 octaves of sound for the mids and tweets but the sub that only plays 2 often gets the most attention in car audio....it's been this way for decades too..just a quirk i lol at sometimes
with car audio and the subwoofer phase you literally just listen to it both ways and see what sounds better to you.
all is not lost however. most good speaker makers realize this and tune their speakers for expected phase shifts. better home audio speakers can do this with the crossover and enclosure. car audio is much harder since most mids are infinite baffle and they produce the lions share of the octaves of sound. . a sub is best case 20 to 80hz that's 2 octaves. that mid however. it does at 5 or more in most cases and only the really high end gear comes in slightly under that with a tweeter taking over before 2.4khz, the tweeter is we will say for arguments sake 2.4, so 2.4 to 4.8 is one, 4.8 to 9.6 is two and 9.6 to 19.2 is 3 making 8 octaves of sound for the mids and tweets but the sub that only plays 2 often gets the most attention in car audio....it's been this way for decades too..just a quirk i lol at sometimes
Last edited by racebum; May 22, 2017 at 09:51 PM.
Safety Car
Joined: Mar 2016
Posts: 3,534
Likes: 432
From: Atlantic Beach FL.
The sub bass requires attention. Those two octaves are expensive to reproduce and have their own set of challenges.
On the two above sweeps, the phase is fairly close at crossover point.
On the two above sweeps, the phase is fairly close at crossover point.
Drifting
Joined: Nov 2016
Posts: 1,820
Likes: 411
From: Somewhere in the middle of Kansas
phase sweeps across a drivers range. in fact, here's a picture of a 10w6v3 phasing. green is ported, yellow is sealed. crossovers and enclosures can affect phase
with car audio and the subwoofer phase you literally just listen to it both ways and see what sounds better to you.
all is not lost however. most good speaker makers realize this and tune their speakers for expected phase shifts. better home audio speakers can do this with the crossover and enclosure. car audio is much harder since most mids are infinite baffle and they produce the lions share of the octaves of sound. . a sub is best case 20 to 80hz that's 2 octaves. that mid however. it does at 5 or more in most cases and only the really high end gear comes in slightly under that with a tweeter taking over before 2.4khz, the tweeter is we will say for arguments sake 2.4, so 2.4 to 4.8 is one, 4.8 to 9.6 is two and 9.6 to 19.2 is 3 making 8 octaves of sound for the mids and tweets but the sub that only plays 2 often gets the most attention in car audio....it's been this way for decades too..just a quirk i lol at sometimes
with car audio and the subwoofer phase you literally just listen to it both ways and see what sounds better to you.
all is not lost however. most good speaker makers realize this and tune their speakers for expected phase shifts. better home audio speakers can do this with the crossover and enclosure. car audio is much harder since most mids are infinite baffle and they produce the lions share of the octaves of sound. . a sub is best case 20 to 80hz that's 2 octaves. that mid however. it does at 5 or more in most cases and only the really high end gear comes in slightly under that with a tweeter taking over before 2.4khz, the tweeter is we will say for arguments sake 2.4, so 2.4 to 4.8 is one, 4.8 to 9.6 is two and 9.6 to 19.2 is 3 making 8 octaves of sound for the mids and tweets but the sub that only plays 2 often gets the most attention in car audio....it's been this way for decades too..just a quirk i lol at sometimes
I don't think you would have had to tell me which color was ported and which color was sealed, LOL. Also, great point on range of frequencies/octaves that the mids and tweets cover and how they are often neglected in a system. I spent over $800 just on front and rear speakers and it will be more on the next set.
As far as low end, yes, many spend an inordinate amount on low end in those two octaves, but I would also argue it is WAAAAAAYYYYY easier today to get solid, deep, pounding low end in a vehicle than it was 25 years ago. The quality and design of subwoofers are suited much better for the car audio environment. It wasn't that you couldn't back then, you just had to really know your stuff to get it done. Now you can slap a plethora of different subs in a relatively small sealed box and they will sound pretty good.
Safety Car
Joined: Mar 2016
Posts: 3,534
Likes: 432
From: Atlantic Beach FL.
Because of the relatively long wave length of sub bass and the distance the woofer may be from the listener, there is another phasing issue.
If your speakers are crossed over at 100Hz with a wavelength of around 11 ft and your sub is 7 ft away from you and the mid is 3 ft away from you then it kind of has to be done by ear.
The reason I recommended what I did in the above post for the Polk db 351 is because it has been done so many times here, including my car. It should work in a similar manner that the Bose tiddler did, playing nicely with the Bose woofer. There have been a few members here that have reported that the mids didn't sound good and that the highs hurt their ears and it was due to reverse polarity.
If your speakers are crossed over at 100Hz with a wavelength of around 11 ft and your sub is 7 ft away from you and the mid is 3 ft away from you then it kind of has to be done by ear.
The reason I recommended what I did in the above post for the Polk db 351 is because it has been done so many times here, including my car. It should work in a similar manner that the Bose tiddler did, playing nicely with the Bose woofer. There have been a few members here that have reported that the mids didn't sound good and that the highs hurt their ears and it was due to reverse polarity.
Last edited by Rob 02; May 23, 2017 at 10:59 AM.
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
mids and tweets are going to be 500 or more just for the front set, you may build pods in the door. you will have to deaden a lot, you have to play with positioning and you have to tear your door panels off repeatedly making small adjustments until you get it right. it takes me FAR longer to get the front stage right than it does a sub. subs are easy.
Safety Car
Joined: Mar 2016
Posts: 3,534
Likes: 432
From: Atlantic Beach FL.
When It comes to the C5 I will admit that I don't think like an audiophile. I built my car as a project car with some performance things going on. Like some others on the forum I am not so sure my car would lend itself well to high end audio. Needless to say, the stock stereo can be downright annoying to anyone who appreciates music.
I have some good audio equipment at home but here on the Corvette forum I tend to talk to the folks that are looking to improve sound on the cheep.
I do have an appreciation for you folks that have high end gear in the Vette. I may get more into that in the future. I have done some higher end audio in the past and have worked in the field. Sound stage is not something I have thought about a lot when driving this performance car.
I do have a JL stealth box and some sound deadening but nothing over the top.
I have some good audio equipment at home but here on the Corvette forum I tend to talk to the folks that are looking to improve sound on the cheep.
I do have an appreciation for you folks that have high end gear in the Vette. I may get more into that in the future. I have done some higher end audio in the past and have worked in the field. Sound stage is not something I have thought about a lot when driving this performance car.
I do have a JL stealth box and some sound deadening but nothing over the top.
Last edited by Rob 02; May 23, 2017 at 04:38 PM.
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
there are still some good choices here. that morel tempo ultra can be had as low as 259 for 6.5 components and a jl w3 sub is maybe 160-170
i know i'm a rare duck and high end car audio is extremely niche
Drifting
Joined: Nov 2016
Posts: 1,820
Likes: 411
From: Somewhere in the middle of Kansas
Now, you can drop obscene amounts of money on them. There is also the flip side. I had the first Alpine CD player, the 5900, that was a din size or under dash mount and an accessory to add to your cassette deck head unit, LOL. It was $600 retail. 
Now you can buy cheap car audio gear, less than $100 for a CD receiver or a set of components. You get what you pay for though. I have just as much fun building a high end car audio system as I do my home system. I guess maybe we are a rare breed as I don't know anyone locally that drops the coin I do on home and car audio and I consider myself an enthusiast, not super hard core.
Safety Car
Joined: Mar 2016
Posts: 3,534
Likes: 432
From: Atlantic Beach FL.
I worked in a shop in 1989. It seemed more expensive then to me. A Rockford Fosgate punch 45 costed around $275. That was a lot of money in the 80's. I think the Alpine components were a little over $150. In today's dollars that would be a substantial amount of cash.
Drifting
Joined: Nov 2016
Posts: 1,820
Likes: 411
From: Somewhere in the middle of Kansas
Sounds like we are from the same era.
Safety Car
Joined: Mar 2016
Posts: 3,534
Likes: 432
From: Atlantic Beach FL.
I couldn't afford a C4 back then working at a stereo shop. I had a 3rd gen Camaro. There was a cubby hole in the back that you could drop a woofer box in. Having subs back then was a big deal. The entire head unit pulled out. I remember toting it around in a bag. My shop started selling car phones and we got a discount on them. There was a hand held phone but it was $800.
Drifting
Joined: Nov 2016
Posts: 1,820
Likes: 411
From: Somewhere in the middle of Kansas
I couldn't afford a C4 back then working at a stereo shop. I had a 3rd gen Camaro. There was a cubby hole in the back that you could drop a woofer box in. Having subs back then was a big deal. The entire head unit pulled out. I remember toting it around in a bag. My shop started selling car phones and we got a discount on them. There was a hand held phone but it was $800.
Last edited by 02BlownZ06; May 24, 2017 at 05:23 PM.