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Old 29th-October-2012, 11:40 AM   #16
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I too have seen seperation on some plywoods and the last few years I got away from the less expensive plywoods that were maybe 5-7 plys and gone to a higher dollar 12+ ply plywood for things. The better grades of plywood also have less voids in between the layers. Like anything else you get what you pay for sometimes.

When I'm using 3/4" or 1" thick material for things I will either use a better grade plywood or an MDF. When I'm making thinner things like trim panels and it only needs to be 1/4" thick I will maybe use tempered masonite. I've also found out that if you paint or seal the wood before you cover it the part lasts longer should it become wet at some point. We had a couple of the old projection TV's at work the other day to throw away and it rained and the next day the particle board swelled up and became more brittle.

I have chased a lot of rattles through the years and that's one of the reasons I suggested turning the sub around to fire into the interior of the car. I did a test many, many years ago with an audio control RTA and with the sub firing rearward in a trunk there were frequencies that were 3 to 6dB less than having the sub firing forward and having it properly sealed with a wider and taller front baffle board against the back of the rear seat. I look at subs firing rearward into a trunk cavity like having a home subwoofer in another room of the house. Yes you will hear it but at a reduced volume and if it's in a closet with a door I've had the closet door rattle. To me it's better if you put the sub in the same listening room or have the sub working into the main listening enviroment. It's nice to open a trunk to show off things but when you do so with subs making sound into the trunk it also affects how it then sounds inside the car.

Thanks for the compliments on the video guys. Sometimes you can try and describe things until you are blue in the face but then sometimes a picture brings it all together or make it more meaningful.

Jim
Hey Jim,

Great Vid. I have a few questions......

You posted that you felt it best to fire the sub into the cabin rather than fire it into the trunk. In your findings through experimentation does this mean that you feel mounting the sub in an infinite baffle configuration will yield you better sub volumes along with clarity within those frequencies or are you talking about firing the sub into the cabin but have it in it's own sub box?

Also, have you ever used lexan or plexiglass to mount amps or whatever other stereo equipment? I have a sign company down the street from me and they sell plexi and lexan at wholesale prices so I can get it pretty cheap. My only fear is heat from components affecting the plastic. I was thinking of going with a quarter inch piece for better wall rigidity so that I don't get the resonant frequencies bouncing the plastic around although I also think that 1/4 inch may be overkill and 1/8 may be a better balance since weight reduction is one of the things I'd like to achieve. I also like the fact that, if you like the clean plastic look, you don't have to upholster the plastic and it cleans easily.

Your thoughts?

John
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Old 29th-October-2012, 12:03 PM   #17
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While I do agree with mounting the sub in a forward firing condition to lessen rattles even in your own testing using an RTA certain frequencies were down 3 to 6 db? As you know 3 db is barely able to be heard by the human ear but adding 3 db takes twice the power and 6db 4 times the power... This can be huge in the overall range of audio in the vehicle. I know most people don't have a trained ear to hear the missing audio. But at the same time most enclosures aren't built for the particular sub either. Consequently mounting the sub in a forward firing position and having an enclosure not built to the spec of the sub or of proper design to take advantage of the end listeners music tastes could leave a lot on the table. I would be upset if I shelled out cash for a 600 watt amp and installed the equipment then only had the equivalent of 200 watts output at 60Hz just where I wanted to ift that bass kick.... Just saying its all a tradeoff in the end. Usually big power creates big rattles... You can get the best of both worlds but I don't recommend turning the box around when it was made to work the other way. I would also recommend some sound deadening materials to quell those vibrations. Nice work on the mounting and custom panels in the trunk.
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Old 29th-October-2012, 01:06 PM   #18
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Last edited by Rich74custom; 29th-October-2012 at 01:07 PM. Reason: added pic
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Old 29th-October-2012, 09:20 PM   #19
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Hey Jim,

Great Vid. I have a few questions......

You posted that you felt it best to fire the sub into the cabin rather than fire it into the trunk. In your findings through experimentation does this mean that you feel mounting the sub in an infinite baffle configuration will yield you better sub volumes along with clarity within those frequencies or are you talking about firing the sub into the cabin but have it in it's own sub box?

Also, have you ever used lexan or plexiglass to mount amps or whatever other stereo equipment? I have a sign company down the street from me and they sell plexi and lexan at wholesale prices so I can get it pretty cheap. My only fear is heat from components affecting the plastic. I was thinking of going with a quarter inch piece for better wall rigidity so that I don't get the resonant frequencies bouncing the plastic around although I also think that 1/4 inch may be overkill and 1/8 may be a better balance since weight reduction is one of the things I'd like to achieve. I also like the fact that, if you like the clean plastic look, you don't have to upholster the plastic and it cleans easily.

Your thoughts?

John
I guess I wasn't real clear in my other reply but the sub needs be in a controlled enviroment (enclosure). When I said baffle what I've done on a lot of cars is the area behind the seat is to make it a solid baffle attaching to the existing metal behind the seat. Since you can't really put the material on the frontside as this would inhibit the rear seat from going back in, I put it on the backside with screws going from the interior side of the metal behind the rear seat going rearward into a baffle board behind the metal. I then caulk in any gaps and edges to basically seal off the interior behind the rear seat to the trunk. Before I put this board in for the last time is I figure out where I want an opening on the middle of it that is larger than the cone area of the subs. With this board now in the vehicle I have a hard edge that an enclosure can be attached to later either with screws coming backwards from the interior side or I've also used angle steel and have all of the attachment points in the trunk.
One thing I sometimes do is this baffle board seals off most of the trunk to the interior and sometimes if I don't have speakers on the topside of the deck is to put a solid baffle on the underside of the deck.

My basic concern of having a sub firing into the trunk is look how or where home subwoofers are located. They are located in the room/listening enviroment or if they are in a neighboring room if they are properly installed they have subwoofer enclosure sealed off against this wall (or basement floor) and then through a hole cut in the wall or floor allows the sub sounds to easily get into the main room. Yes, bass will go through drywall, go through concrete, go through thick upholstery but anything that is non acoustically transparent will reduce it's volume from one area to another.

If a way to direct the sound directly into the interior of the car and not into the trunk and interior has to reduce the chances of rattles and should give more volume. How much I don't know or have any figures on but think about a subwoofer as it pressurizes an area and then rarifys it and how sheetmetal on a car flexes. If the sub pressurises a trunk AND an interior the resulting pressure will be less than if it just pressurises the interior. If you were to build a flimsy, flexing enclosure for a sub then it will have less output than a sturdy, non flexing enclosure. Sub enclosurea are not made out of aluminum foil but out of a thicker more rigid material.

Another thing to look at is look at the people doing the SPL contests. They are not running the subs in the very back of a limo but are running them to where the subs are compressing alot smaller interior like from the back of the front seats to the dash. Smaller area's to compress the air results in more SPL.

As far as using plexiglass or lexan for things, go for it. Be aware though that some plastics are brittle but polish up nicely on edges while others may have some flex in them but present problems trying to polish the cut edges. Some plastics I've even drilled and tapped threads into them to attach things to them. I built a custom notched windshield for a buddy of mine with a Henry J and so far after 6 years or possibly longer, it's holding up just fine. On this one I had some scrap 1/2" thick clear plastic and to make right angles on the notch I drilled holes into the edges of the one part, came back with a tap and threaded the holes. I was then able to run bolts through one section of it into the other section.

Years ago I had a buddy of mine make a clear cowl induction hood for his first generation Camaro and I had a heck of a time finding out he made it but he finally told me and the light in my head also went on. With carefully controlled heat you can heat up platic to where it becomes rubbery and formable. When I was trying to make 1/2" circular rings for some isobaric 15's I took some 6" strips and stuck what I could into an oven to heat the material up. Once I got to the ideal temperature I was able to pull it out of the oven and begin wrapping it around a wood circle. Since the oven was only so deep after this J shaped piece cooled I stuck the other half into the oven and when it was right pulled it out and wrapped it again round the dood circle. I was then getting close to having a circlular tube but then had to let it cool to where I could cut the edges that would butt together closer to the final dimension I needed. After a few trips in and out of the oven I finally got a round 1/2" thick clear spacer tube BUT then found out I had to resquare the edges as they had become changed. Once I got further along I took the right sized drill bit for the threads I wanted to cut and then drilled the plastic and tapped thread into it.
I went through a learning curve with plastics and you will too so I would get some scraps to try things on. If it screws up, then try again.
There are also some ways to take colored LED's and by drilling into the edge of the plexi you can make an inside polished edge glow. Plenty of idea's and ways to do things out there.

Attached is a buddy of mines Altered Wheel base Studabaker (Suicide King) and either Bill the owner or one of his guys might have seen what I did on his Henry J and made this notched windshield attached below. I have pictures of the Henry J I did but they are blurry and it's hard to see how things are threaded into the plastic.

Years ago too I played around with mirror backed plexiglass and had that in my motor bay.

Jim

Last edited by Custom Jim; 17th-January-2013 at 08:47 PM.
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Old 29th-October-2012, 09:23 PM   #20
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That's how you do it !!!!!. Yes sir. Very Nice.

Jim
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Old 29th-October-2012, 10:57 PM   #21
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That's how you do it !!!!!. Yes sir. Very Nice.

Jim
thank you Jim! were finishing the last panel this week, ill post pics here soon.
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Old 30th-October-2012, 08:34 AM   #22
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I really really really really like this set up!

I want to see the end result!

Last edited by on a bugdet; 30th-October-2012 at 08:37 AM.
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Old 30th-October-2012, 09:16 AM   #23
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I want to do the same thing to my '72 when I get the body work straightened out. Subscribed.
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Old 11th-November-2012, 04:25 AM   #24
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I want to see the end result! Have you finished the trunk???? yet!
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Old 11th-November-2012, 11:27 AM   #25
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Soon! I know I hate that i left it unfinished, I have the panel cut out already, just need to cut the sub hole and then cover it in vinyl. Should be soon!

Work is taking over my life at the moment! ahhh
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Old 12th-November-2012, 01:39 AM   #26
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Soon! I know I hate that i left it unfinished, I have the panel cut out already, just need to cut the sub hole and then cover it in vinyl. Should be soon!

Work is taking over my life at the moment! ahhh
I hear you about work! I been really busy at work too!
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Old 26th-November-2012, 06:42 AM   #27
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anytime for that trunk?
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Old 26th-November-2012, 08:05 AM   #28
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Good information here!

Thanks for the input!

I'm along for the ride also!

Mark
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Old 26th-November-2012, 12:24 PM   #29
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Probably here in a couple weeks. It's killing me too! Kids, wide and holidays don't help for car/shop time. Haha
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Old 4th-December-2012, 08:20 PM   #30
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The start of my son's trunk
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