Speaker placement pre-78
For a long while I had been trying to find a good place to put rear speakers, but after lurking in quite a few audiophile forums it appears that I don't want them at all. From what I understand rear speakers would move the sound stage to the middle of the car or behind the seats, not good. Especially since the only thing behind someone sitting in a pre-78 vette is the rear window. Since the top of the rear storage area is about mid shoulder you wouldn't get very good sound from behind the seats anyway.
Here is a diagram of what I'm thinking:

Mid-Base drivers in the kicks 6" or 5.25", is bigger better or just overkill?
Mid-range and tweeters in or above the dash
Sub in Storage compartment firing down
I have some questions about the placement of the mids and tweeters
here is a drawing of the front:

I have a set of 2-way 4x6 speakers that I got for the dash. However, I had some tears in the vinyl where the small holes above the speakers were. I repaired the tears but it involved reinforcing the vinyl with plastic sheet and re-drilling the holes. All 1,146 of them.


If I go with the dash speakers I'm not sure I would get good sound out of them. Would it be better to cut the vinyl out of this section and mount them on the top of the dash?
I found a thread at mp3car.com that showed how to construct pillar pods for the mid-range and tweeters.
There were more pictures here is the link if you are interested:
http://www.mp3car.com/vbulletin/work...-tuning-6.html
Would this be a better alternative than the dash speakers which would be reflecting the sound off of the windshield. With the placement of the dash speakers and the slope of the windshield I think the direct path would be somewhere around your stomach. I think the pillar pods would raise the sound stage a bit, would that be correct.
A third alternative would be to have both.
Sub:
As you know there isnt much space behind the seats and I still want to be able to stow the T-tops there so my alternatives for sub placement are few.
Here is what I'm thinking about doing:

Forgive the drawing it is a quicky.
I think the best alternative is to hang the sub box from the rear deck and fire it down.
Here is a section through the box:

The section shows it being built in place with MDF but after much lurking in the mp3car.com fabrication section I think I'm going to make it out of fiberglass. My plan is to tape off the underside of the deck and the back wall and build the top and back in place. Then remove it and finish the front sides and bottom. I think it would be much better to be able to remove it. The down side would be fiberglassing upside down on a horizontal surface. Hard but not impossible. I would fasten it in place with brackets on the back wall and the flange under the rear window behind the trim.
I'm limited to a 10" driver because of clearance issues. Are there any thoughts on this. Would 2-8's be better?
I am also planning on putting the amps in a custom ventilated box in the spare tire carrier but that is a whole nuther story.
I know this is alot at one time but I wanted you to see the whole picture.
To summarize my Questions
Mid-range/tweeters
Dash speakers, pillar pods or both?
If Dash speakers, under or on top?
Mid-bass
5.25' or 6" is bigger better or just overkill
Sub
Will firing it down be OK
One 10" or two 8"
Thanks in advance for any insights.
David
Last edited by GATOR454; Jun 6, 2007 at 09:49 PM. Reason: I wouldn't win no spellin bee's
With the primary front speakers in the kick panels, this works:
Tweeters in kicks w/ dash grilles open.
While one would normally want the tweeters near the primary front speakers, nevertheless many separate them & this can work: Tweeters in dash location or in corners of dash.
Did not work good: Tweeters in doors or pillars.
5.25 is ideal for natural sound, expect better of axis response & can be angled some behind the factory kick panels. There is not enough air space volume in a C3 kick panel to optimize a 6 1/2 which should go in doors. If you try the plate speakers in the kicks, you might prefer them there- otherwise the dash location.
PS Rear speakers are a matter of preference. An advantage of front & rear speakers is full sound at low volume. At high volume only 1 set is needed.
It is possible to do excellent high SQ rear speakers. Equivalent to
2 8s facing forward & works great. http://forums.corvetteforum.com/showthread.php?t=634468
The Best of Corvette for Corvette Enthusiasts
http://forums.corvetteforum.com/show....php?t=1049772
Tweeters in dash firing up.
Sub in back firing at any surface rather than open air.
By the way, the half way point between rear speakers and front speakers, as in divided when using two sets...would put the stage right in front of our heads. That's pretty much perfect and that's why my system has two sets of speakers.
Now, in most cases just fronts will sound amazing and won't require as much tuning as a four speaker setup.


Seriously, I keep reading about people wanting highs in the dash and mids by their feet. It makes me go
every time.I had a setup like that installed in my truck once. I thought it was fantastic. Then I saved up the coin and had a custom set of kicks made to hold my high end. HOLY SCHNIKEYS. Night and day difference in every single song I could listen to. Don't waste your time with the dash. I promise the difference between the two setups is remarkable.
Seriously, I keep reading about people wanting highs in the dash and mids by their feet. It makes me go
every time.I had a setup like that installed in my truck once. I thought it was fantastic. Then I saved up the coin and had a custom set of kicks made to hold my high end. HOLY SCHNIKEYS. Night and day difference in every single song I could listen to. Don't waste your time with the dash. I promise the difference between the two setups is remarkable.
I was going to do b/w 5.5 - 6.5" mids in the kicks, tweets in the gauge cluster and two 6.5" in the rear compartment and an 8" tube sube in the back with an AMP under the dash since i don't have a heater core anymore. Setup still in the air as I haven't bought anything although I'm pretty sure I'm close to biting the bullet.
BTW, awsome "quick" drawings
Question, why do all the newer cars have the bose mids in the doors and the tweets on the pillars if it would sound better together? even the high end cars have this setup.


Because manufacturers have to cater to everyone, not just the audiophiles. Besides, anyone serious about car audio won't use anything that came stock anyways.
Most people wouldn't understand kick panel setups and the life of the speakers would be shortened by people thinking they are footrests.
Here are a couple replies I got on a couple Car Audio forums.
As far as midbass there really is no such thing as overkill IMO. The midbass frequencies are generally where most vehicle systems lack most..so I would say to use the largest speaker possible.
The sub firing down as per your diagram should work excellent..I highly reccomend doing it that way..and correct, you should not require any rear fill in that vehicle..the interior does not really warrant it, and it would pull the soundstage back..ok for loudness..not ok for sound quality. As far as using one 10 vs. two 8's...you will most likely get various opinions on that one.
Some people firmly believe that bigger is better,,some firmly believe multiple smaller drivers will have better sound quality and play "tighter" then single larger drivers. In actuality it really depends on the particular sub, as well as it's installation and enclosure design. In other words any size or number of speakers can sound better or worse then any size or number of speakers if all I mentioned is not taken into account.
Now all else being equal..and in my opinion, I would use the single 10'' if you are looking for more low end response..and use the two 8'' if you tend to listen to music that does not have alot of low end..such as older rock music. This is not to say one will sound extremely better then the other..just a vantage point to help with your final decision..I honestly believe either setup will sound great and produce plenty of low end in that car if it's installed properly and utilizing quality gear.
Under no circumstances use both. You never want two drivers of the same frequency that close together. Trust me it won’t sound good.
Whether or not you use dash speakers or pillar pod speakers will depend on personal preference. They both have their pro’s and con’s. You should install the Subs then experiment with the placement of the mid/tweeters and kicks.
If you go with the dash speakers then under the dash placement would be the least desirable. The overall sound would suffer from reflections from the windshield. I would recommend angling the speaker away from the windshield as much as possible. Directing the speaker at various angles may take some trial and error to achieve the optimum position. Start by aiming them towards the center of the car about head height, and go from there.
If you go with Pillar speakers aim them anywhere from directly towards each other to directly at the head of the opposite passenger. This is called off axis staging. Again, you want to minimize windshield reflection. Start with about 10 degrees off axis, and tilt them towards the opposite passenger until you get the sound stage you are looking for.
You could always put in both with an A-B switch and change them depending on the music or how you feel that day.
Kicks:
Bigger is not always better. I’m not sure what it looks like behind the kicks of an old Corvette but I bet there isn’t much room. Mid-basses like subs depend on the airspace around the driver to produce good sound. If you put in the 6” but don’t have adequate room behind the speaker it will sound flat. Pick the two drivers you are considering and determine their space requirements and see if it would be doable.
Also the same aiming of the kicks is the same as the dash mounted speakers. Just make sure you re-create the same airspace during testing that you anticipate in the finished kick enclosure.
Subs:
I think the placement of the sub that you show in your drawing would be ideal for your situation.
As for one 8” versus two 10” subs.:
I think the two 8” subs would be better than one 10” sub for SQ, if for no other reason than that you could invert one of them to greatly lower 2nd order harmonic distortion. As for SPL, by having 2 isolated voice coils you’re less likely to get power compression because the coils can better radiate heat, not to mention the fact that you only need half as much amplifier power to obtain the same loudness as with one sub.
Obviously there are exceptions. Also, with any given amount of power, the system with the most cone area is going to be more efficient, and so louder as well. You have to look at the twin sub setup as a single speaker with a larger cone area.
I would suggest getting a box analyzer like WINisd (do a search here there are several free ones) and plug various single 10” drivers double, 8” drivers, and maybe ever double 10’s if you can fit them and make your decision base on your desired frequency response curve.
If you go with two subs make sure you put them in separate air chambers. It's not that a single airspace will sound bad, it's the fact that if 1 woofer dies then the remaining one will be playing into a chamber that is way to big. This could damage the driver. Build each sub its own chamber so if one fails then you can still play the other. I've always built them that way.
Finally I think for your car rear fill speakers would do more harm than good for both SQ and staging. However if you just want loud and don’t care about Quality then the more the better.
Car 1: mid speakers in the kick panels and tweets in the pillars or dash mounted.
Car 2: mid Speakers in the kick panels and tweets down near the kick panels.
Car 3: Whatever combination above with additional rear mounted speakers.
You'd have to use the same microphone and listening point...say head height on a 6ft male driver in the driver seat.
Same song....that song from Overhaulin hasn't been played out yet, just use that one.
love the show, so tired of that darn song.Even after the replies above I'm still leaning towards the mids in the kick panels as they are not directional and the tweets mounted at opposing passengers, whether mounted on the dash or pillars.


Your ears can hear from approximately 20Hz to 20,000Hz. The bottom of the scale is non directional, now as you move up in frequency, the sound becomes more directional. If you have seen a frequency response graph it is non-linear because of the definition of an octave. One octave is defined as the doubling of a frequency. So, 40Hz is one octave higher than 20Hz. 80Hz is two octaves higher etc... What I'm saying is, just because your mids are only playing 90-250hz, they are playing directional frequencies. More noticeably as they increase in value.
about your system, I like the sub idea, upside down... COOL..
I will tell you that I just disconnected my speakers I had in the dash(4x6 2 way pioneers running off the hu), it makes my system sound much cleaner...especially when the tops are on and the windows are up... I think the reflection of the highs off the glass echos too much or something and sounds like distortion...or just general crap.
If you want good midbass, use the 6.5s.
I have the 5.25s componets and 70w rms going to them, they still do not offer any real bass. I mean yeah they try to thump a little but... they sound much better crossed over running at 100hz and just used for mids(vocals) and highs..
A 10" sub will make more bass then you need anyway.
I have the 5.25s in the kicks and tweets on the outside of the kicks facing upwards. There is plenty of highs and no funny distortion or echos from the windshield.
You have some great ideas!


I know the placement of the tweets does not look safe but I have had no problems with people kicking them. They are a lot more solid then you think... I didn't want the 5.25s visible so we hid them behind the panels.












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