Effects on sound from fiberglassing an enclosure?

[j-roadtatts 1,129]

I can draw another picture with all the shapes broke down for volume if you need. I didn't draw a blue print just knew the numbers to build to.

All wood is 3/4 MDF with double baffle.

Outside dimentions:

Back box is 13.5 Deep x 19.5 Tall x 41 Wide

front box is 7.75 Deep x 16 Tall x 30 Wide

I might as well go over my goals and music type. My biggest goal is to have a TON of headroom in the system for differant recordings. My next goal is MAX efficiency. This is the biggest reason I bought a BTL other than motor force. Another very Important goal is good imaging.

You might as well call me an sq guy because I like the music to sound like I'm at the concert. I like live music.

I listen with the EQ as flat as possible. I use the crossovers on my deck. I Do like a bloated low end from time to time.

I have always had a decent stereo since as long as I can remember. Nothing I would brag about but they sounded ok. Now that I am older and can afford a nice system I am building one. I LOVE to BUILD anything so the work is very enjoyable to me. I am not in a hurry, just want to be happy when I'm done. I am only building this for myself and am only trying to impress MYSELF. I don't show my system off or "bump in town" and Only listen at full tilt on the highway by myself. When my wife and kid are in the car we listen pretty low, why I like efficient speakers.

The music: Tool, Alice in Chains, The Beach Boys, Black Crows, John Melloncamp, Everlast, Twisted sister, Metallica, Slayer, Motley Crue, Lamb of God, Too Short, Easy-E, Beastie Boys, Tim McGraw, The Judds, Garth Brooks, Johnny Cash, Pink Floyd, Acoustic and live albums. Basicly EVERYTHING. THis is why I want alot of headroom.

Alrighty then.....Let me know what else you need to know?

[///M5 2,833]

What was the target shape for the port (ie L, W, H)?

[j-roadtatts 1,129]

What was the target shape for the port (ie L, W, H)?

26" long x 4.25" wide" 14.5" tall

[///M5 2,833]

Seems reasonable for a 15"...not sure that the dimensions you posted in your picture match your target shape though.

[j-roadtatts 1,129]

Seems reasonable for a 15"...not sure that the dimensions you posted in your picture match your target shape though.

What would be my target shape?

As I said I DID NOT count any of kerf opening as port lenght? No one seemed to know where to start measuring from. Mouth, throat, 1/4 way, 1/2 way, 3/4 way Nobody seemed to have an answer? I figured I'm tuned a tad low if anything because of extra lenght? Let me know what you think?

Edited February 8, 2010 by j-roadtatts

[///M5 2,833]

The crossmember cutting the port in half is what has me confused. Not sure from a top view what that is doing. Otherwise your measurements are fine and you are indeed tuned low, but only by a Hz or so.

[j-roadtatts 1,129]

The crossmember cutting the port in half is what has me confused. Not sure from a top view what that is doing. Otherwise your measurements are fine and you are indeed tuned low, but only by a Hz or so.

The cross piece IS ABOVE THE PORT. ITS the front wall to the back box. Front roof piece goes under this cross piece. The false ceiling in the back half keeps the port the right height and keeps end corection right. PLEASE go look at my build again and you will see a picture without this cross piece.

Whats your words of wisdom about tuning the Kerfed opening? Throat, mouth, 1/4, 1/2, 3/4?

As far as tuning I am after 32hz. I went a little low instead of high because I don't want to miss that MEMORABLE experiance.

ALSO was planing on the two oak dowels front to back to brace the back wall so If iirc the extra displacment will bring me back up?

I can take the last 1 3/8" off the port wall real easy if WE decide I should?

I know Its a number battle back and forth which I have already done just want a second opionion before fineshing. What did you come up with?

I know the box looks complicated but simple volume is all I am going off of.

Thanks again M5 for taking the time to make sure My shits right. I wanted to pay Shizzzon to help but I think he's busy So if you want PM me and I'll send you MONEY, probly more than you think!!!

[///M5 2,833]

No money necessary. Your math is within a Hz. Sorry I didn't see the pic without the cross member before, just wanted to make sure

In the case of designing boxes I don't believe in PM's, keeping things public is always a better option as others can pop in and say something.

[j-roadtatts 1,129]

Well I can't say thanks enough brother. I am on this forum because you guys are real level headed and keep me GROUNDED THANK GOD. I am trying to buy my first house this month SO I definetly don't need to WASTE money doing things I don't need to. Up until now everything I bought was from selling things on ebaY. Ya I didn't think I would make that much either!!! Well now I am on the credit card and the SAF (spouse approval factor) is pretty low.

So Thanks again M5.

In the case of designing boxes I don't believe in PM's, keeping things public is always a better option as others can pop in and say something.

I hear you about the PM's, I think we all can learn from Our's and Other's mistakes.(hopefully others )Now that I know the proper way to start a topic and ask for help you guys will be answering ALOT more questions.

I think ALOT of the trunk crowd guys are interrested in my design So maybe a Writeup and Review about the BOX Design are in order. Let me know if you guys want one?

WOW!!! Nobody ever wants to touch the whole kerfed opening tuning thing. Some day Somebody will test I'm sure Until then.......Good enough for the Girls I know.

Edited February 8, 2010 by j-roadtatts

[///M5 2,833]

I don't understand your kerfed question otherwise I'd answer it.

[j-roadtatts 1,129]

I don't understand your kerfed question otherwise I'd answer it.

Where to start measuring port lenght.

[///M5 2,833]

The kerf really just changes the velocity and does very little to the overall length. As a general rule of thumb if you subtract half the flare radius from the length of the port (ie it shortens it), but again in your case this won't really affect things in particular since it isn't fully kerfed. (ie you only kerfed one side not all 4). Measurable, actual, and enough to worry about are all in play here and none of them will be big enough to change your result. You'll be close to your target tuning

[j-roadtatts 1,129]

M5 is the MAN.

Yeah, YOU know I will never see a meter and am only worried about audible differances.

Looks like time to finesh the BOX!!!

Now I know what defines a kerf opening. Thanks again.

[j-roadtatts 1,129]

After going over the math again I am going to take the last short section off the port. This brings my port length down to 24 5/8" instead of 26". The two Oak dowels only displace 0.03cf. so nothing that helped. This also brings my net volume back up to 5cf.

This should get me within a 1/4hz of 32hz. definetly good enough for the Girls I know.

[j-roadtatts 1,129]

The conclusion to this topic is Fiberglass will NOT make an audible difference when used in an enclosure.

Fiberglass MAY have benefits if you are chasing tenths on the meter But could also hurt you. You will NOT know without testing.

All materials have a purpose, But are USELESS when used in the wrong application.

If you want to make an enclosure stronger you should use bracing instead.

The ONLY use for fiberglass in a regular enclosure would be for the corners, even then the benefit is probly marginal.

For the average person like me wondering if Fiberglass is for you, DON'T WASTE YOUR TIME OR MONEY. (learn from my mistakes)

That is ALL.

J-Road