New Sound System for the 944

guardsred944s · 07-22-2009, 09:49 PM

Ok so I'm done with the first step of doing a new sound system. The goal is, good sound, invisible system. The next step is selling my miata, then pressing the "checkout" button on my crutchfield shopping cart.

So today I mocked up a sub woofer cabinet for a Polk Audio db840 8", to fit in the right rear cubbie. I went through a couple of designs, calculating volumes, etc. I considered have a sub cabinet behind each passenger but the only way I could have done it (while still being super classy "invisible") would be to face the subs towards the back of the seat. I finally settled on a trapezoidal box which fits in the cubbie and has a volume of approx 533 in^3, the sub calls for 600ish in^3. Not bad I think!

dillon410021 · 07-22-2009, 11:10 PM

pretty nifty

Andy1212 · 07-22-2009, 11:30 PM

Nice build, but you should have used mdf. That ply is nowhere near strong enough, you will have some severe flex problems.

supes6 · 07-22-2009, 11:40 PM

Quote:

Originally Posted by Andy1212

Nice build, but you should have used mdf. That ply is nowhere near strong enough, you will have some severe flex problems.

Sounds like it's just a mock-up.. I hope.

JohnKoaWood · 07-22-2009, 11:42 PM

Quote:

Originally Posted by supes6

Sounds like it's just a mock-up.. I hope.

You don't sound mat a moc-up... but it does look nice...

guardsred944s · 07-22-2009, 11:53 PM

Well I used 3/8 inch ply, i know this isnt the "proper" way to do it, but ill explain why I did it. Firstly, all the material used were from stuff "just lying around". So basically "from scratch".

The second is that I seriously doubt that sub enclosures are subject to to failure because of the material used... instead I assume that it is from improperly joined joints. From my research, the only thing I found as a reason for using MDF is that it is less susceptible to cracking when screwing joints together. All joints have been glued as well as predrilled and screwed using wood screws.

I too am critical of using this material as I know it is not the norm, but I will provide updates when I install the sub as to, whether or not this works...

Thanks for the thoughts!

75ohm · 07-23-2009, 12:24 AM

Trial and error for improvements... do it until your satisfied with how it sounds!

You may consider using some backing pieces with glue and air driven staples if you have it to get a tight seal. The tighter the box the better off you'll be regarding rattles...

pontifex4 · 07-23-2009, 12:27 AM

One of the main reasons to use MDF is that it is about as acoustically-dead as any cheap material which you can cut and shape. Its shear strength is terrible, though, and it LOVES to soak up moisture.

Your plywood may have been a fair choice, considering the environment (my storage bins are always a little damp from the rain which leaks down my hatch). If you're finding that it doesn't seal well, though, it may be worth pulling the box out and epoxying the seams with some fiberglass cloth for a bit of added strength.

guardsred944s · 07-23-2009, 12:42 AM

Quote:

Originally Posted by pontifex4

One of the main reasons to use MDF is that it is about as acoustically-dead as any cheap material which you can cut and shape. Its shear strength is terrible, though, and it LOVES to soak up moisture.

Your plywood may have been a fair choice, considering the environment (my storage bins are always a little damp from the rain which leaks down my hatch). If you're finding that it doesn't seal well, though, it may be worth pulling the box out and epoxying the seams with some fiberglass cloth for a bit of added strength.

Yea, another thing I was thinking about when I was taking measurements... TG Porsche dipped all their cars at this point, because there is always a moist spot at the bottom of that little cubbie. (Gentlemen: start your euphemisms...)

V2Rocket_aka944 · 07-23-2009, 01:18 AM

Quote:

Originally Posted by guardsred944s

The second is that I seriously doubt that sub enclosures are subject to to failure because of the material used... instead I assume that it is from improperly joined joints. From my research, the only thing I found as a reason for using MDF is that it is less susceptible to cracking when screwing joints together. All joints have been glued as well as predrilled and screwed using wood screws.

MDF is better for sound boxes as it is so heavy with all the glue and moisture that it will vibrate less due to the speakers.

dillon410021 · 07-23-2009, 09:44 AM

Quote:

Originally Posted by Andy1212

Nice build, but you should have used mdf. That ply is nowhere near strong enough, you will have some severe flex problems.

lol, Just wrap it up in some duct tape.

carlege · 07-23-2009, 09:49 AM

Quote:

Originally Posted by V2Rocket_aka944

MDF is better for sound boxes as it is so heavy with all the glue and moisture that it will vibrate less due to the speakers.

also its more sound proof= a better sound quality for subwoofers. and its really not all that expensvie. But good luck

Dougs951 · 07-23-2009, 12:04 PM

What are you planning to put in the rear quarters? If you wouldn't mind could I take a look at your shopping list?

guardsred944s · 07-23-2009, 01:59 PM

http://www.crutchfield.com/p_107DB84...dio-db840.html

and

http://www.crutchfield.com/p_236TN25...r-TN250-1.html

but i plan on getting a another 8" when I have the money.

Also a new head unit and some infinity references for the rear side panels eventually.

Dougs951 · 07-23-2009, 04:32 PM

The speakers in the doors and quarters of my car were blown so I replaced those first. Are your speakers the original paper ones?

07-22-2009, 11:10 PM	#2
dillon410021 Addict Rennlist Member Join Date: Dec 2007 Location: Valparaiso, Indiana (46385) Posts: 1,711	pretty nifty __________________ Dillon 1987 944 parts car- sold 1987 944S- 68K miles 1986 944 Turbo- rolling shell, soon to be 944S powered 1987 944 Turbo- daily driver-- stage II MAF, stage II chips, 1988 dme, 3 bar FPR., LR SS fuel lines, Billet bov, LR vacuum line kit/ venturi delete, LR MBC, SFR true 3"SS exhaust, Prosport gauges, 996 wheels, 125K miles

07-23-2009, 12:24 AM	#7
75ohm Resistance is Futile Lifetime Rennlist Member Join Date: Apr 2005 Location: Tampa, FL Posts: 5,464	Trial and error for improvements... do it until your satisfied with how it sounds! You may consider using some backing pieces with glue and air driven staples if you have it to get a tight seal. The tighter the box the better off you'll be regarding rattles... __________________ www.rennwish.org '88 944 NA - Red/Black. The mistress. '00 S80 - Green/Tan. Wife unit's. '03 Explorer - White/Graphite. The daily driver. Click here.

07-23-2009, 12:27 AM	#8
pontifex4 Addict Rennlist Member Join Date: Mar 2009 Location: Kingston, Ontario, Canada Posts: 425	One of the main reasons to use MDF is that it is about as acoustically-dead as any cheap material which you can cut and shape. Its shear strength is terrible, though, and it LOVES to soak up moisture. Your plywood may have been a fair choice, considering the environment (my storage bins are always a little damp from the rain which leaks down my hatch). If you're finding that it doesn't seal well, though, it may be worth pulling the box out and epoxying the seams with some fiberglass cloth for a bit of added strength. __________________ *Charlie* '88 944S - Alpine White / 951-look / Turbo Brakes / Konis / 968 M030 Sways / Weltmeister springs / Euro rear bumper '88 951 - Zermatt Silver / Konis / LSD / A/C Delete / '86 shell B6 A4 1.8T - Quattro / RNS-E / APR software / Hotchkis suspension / Thule rack

07-23-2009, 12:04 PM	#13
Dougs951 Addict Rennlist Member Join Date: Jul 2008 Location: Southern MD/College Park, MD Posts: 1,398	What are you planning to put in the rear quarters? If you wouldn't mind could I take a look at your shopping list? __________________ -Doug D. Come out to the UMD car show! May 2 http://forums.rennlist.com/rennforum...nd-2010-a.html Project Back in Black. 1987 951 Coming Soon- 18" Rims, Tinted front turns, and F+R signal lenses, and tinted windows... Looking for a red 1968 GT6 with an aftermarket sunroof, And a hood bump to clear triple Weber Carbs.

07-23-2009, 04:32 PM	#15
Dougs951 Addict Rennlist Member Join Date: Jul 2008 Location: Southern MD/College Park, MD Posts: 1,398	The speakers in the doors and quarters of my car were blown so I replaced those first. Are your speakers the original paper ones? __________________ -Doug D. Come out to the UMD car show! May 2 http://forums.rennlist.com/rennforum...nd-2010-a.html Project Back in Black. 1987 951 Coming Soon- 18" Rims, Tinted front turns, and F+R signal lenses, and tinted windows... Looking for a red 1968 GT6 with an aftermarket sunroof, And a hood bump to clear triple Weber Carbs.

07-22-2009, 11:53 PM	#6
guardsred944s User Join Date: Apr 2009 Location: Jacksonville, FL Posts: 47	Well I used 3/8 inch ply, i know this isnt the "proper" way to do it, but ill explain why I did it. Firstly, all the material used were from stuff "just lying around". So basically "from scratch". The second is that I seriously doubt that sub enclosures are subject to to failure because of the material used... instead I assume that it is from improperly joined joints. From my research, the only thing I found as a reason for using MDF is that it is less susceptible to cracking when screwing joints together. All joints have been glued as well as predrilled and screwed using wood screws. I too am critical of using this material as I know it is not the norm, but I will provide updates when I install the sub as to, whether or not this works... Thanks for the thoughts!

07-23-2009, 01:59 PM	#14
guardsred944s User Join Date: Apr 2009 Location: Jacksonville, FL Posts: 47	http://www.crutchfield.com/p_107DB84...dio-db840.html and http://www.crutchfield.com/p_236TN25...r-TN250-1.html but i plan on getting a another 8" when I have the money. Also a new head unit and some infinity references for the rear side panels eventually.