gpd132

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.

Rob 02

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.

racebum

you can always use a battery, 1.5 or 9v. attach it to the speaker and see which way the cone moves. it will be in or out. do it on both speakers and you will know which is + and -

Rob 02

^The 9v battery test is tried and true.

The Bose and Polk have the same polarity. I can assure you!

gpd132

I'm not very technical. I would imagine out would mean positive?

racebum

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

02BlownZ06

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.....

Rob 02

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.

racebum

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

Rob 02

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.

02BlownZ06

That has always been my take on it. Once you get a good car audio system set up, it is always a good idea to try the subwoofer out of phase. Most signal processors include that option so you can do it right at the head unit or the DSP. Way back in the day, you had to do it the old fashioned way, but it sometimes provided a better overall sound. So try it back and forth and see what sounds better is a good way to go.

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.

Rob 02

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.

racebum

seems easy to me. a quality sub like a w6 is under 500 dollars. build a custom box, install. if it's sealed you eq somewhere around 5-10hz under open f3 with a wide q and let it rip. biggest problem people have here is using too small of a box and then having to try and tune it out. ported installs also can take multiple boxes to get right and they usually get large.

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.

Rob 02

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.

racebum

this is 98% , maybe 99% of the market

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

02BlownZ06

Put me in the 1 or 2%. In the late 80's we thought $250 was a kings ransom for a set of front components. 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.

Rob 02

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.

02BlownZ06

Exactly!! My main system back then had a punch 45 on the mids and tweets and punch 150 on the subs and it was in my 87 C4.

Sounds like we are from the same era.

Rob 02

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.

02BlownZ06

I couldn't either but I bought one anyway, LOL. It was a high miler and got a great price on it. You are exactly right. That was the big new thing, to have a second dedicated amplifier pushing subwoofers which we started out mounting infinite baffle in the rear deck or mount to wood panel that was mounted infinite baffle behind rear seat in trunk. Trucks were really cool, cause you could build a tapered box to fit behind the seat and the subs pounded you right in the back. I ran a system in my C4 with four 8's in a carpeted box that filled almost my whole rear hatch area and it sounded really good for the time. Later on in my truck I did the same four 8's behind the seat. Hardly anyone was running four subs at that time. I had 2 Alpine 3502 each bridged into mono to run the subs and a 3521 on the mids and tweets. Most didn't even have a CD player yet so if you had this setup with a CD player, it was impressive for the time. I remember the pull outs well, too, and yeah when cell phones first started to appear at audio shops they were SUPER expensive. Ahhhh....the good old days.