Fiberglassing the Inside

[DiabolicCustoms 4]

So I have searched a little and really haven't found out much info. I read somewhere that fiberglassing the inside of your enclosure makes it weak. why is this, is it because of the heat and chemicals released during drying and curing? Is it really necessary for a box that will only see a occasional romp on a lane? Please discuss.

[antonmiller 8]

Effects on sound from fiberglassing an enclosure? - SSA Car Audio Forum

heres some info

[DiabolicCustoms 4]

appreciate that, but about halfway down page 2 it starts to ramble on about his port area and shape choices. it just barely touched on the making it weaker and didn't give a reason why. and if the noise difference is inaudible there wouldn't be a half reason why not to do it right? so if it becomes a mirror to sound waves that is what affects the quality of the sound right?

[deernet 6]

If its inaudible, there wouldn't be much of a reason to do it either, IMO. I don't think it would significantly increase SQ, but I'm no expert. I'd say putting 45s in the corners would give you more of a difference in SQ if your going ported.

[DiabolicCustoms 4]

already got the 45s in place. I was just wondering if putting resin in the box would help smooth the transitions out and make the box stronger, but i had read it makes it weaker. just wondering, i appreciate the input.

[dem beats 1,223]

already got the 45s in place. I was just wondering if putting resin in the box would help smooth the transitions out and make the box stronger, but i had read it makes it weaker. just wondering, i appreciate the input.

J-road made a summation at the end of that thread.

Basically, there is no good reason to resin/glass your box unless you're going to compete. And then it may help or it may hurt. You would have to try both and measure what happens.

Even if it does help with strength, and that's not a sure thing either as it could hurt strength, it's not worth it.

You could do so many other things to make it stronger or louder than cost and effort make is a bad choice to glas/resin your box.

[DiabolicCustoms 4]

yeah i did read that part. i guess my curiosity is on the fact that the statement made was it could make the enclousure weaker. was this a generalized statement encompassing the sound quality or was there some sort of scientific reasoning to this strength issue, I probally won't do it now but i am curious as to why it is so.

[j-roadtatts 1,129]

The way that fiberglass weakens MDF is , The fiberglass resin soaks into the top 1/8 inch of MDF and that 1/8 is brittle while the rest of the MDF is still soft. NOW what occurs next is the MDF no longer has ANY give between ITS OWN layers and WILL start to seperate. MDF by its self is NOT brittle, Fiberglass in thin layers is VERY BRITTLE, The two materials have different attributes. Both have a use in this world, BUT you will gain absolutely NOTHING from using the fiberglass in an enclosure.

The correct way to make an enclosure SOLID is to use internal bracing.

AS stated before, you should read my summary at the end of my "rambling" thread.

[DiabolicCustoms 4]

j-roadtatts, no harm no foul brother. i probaly will not glass the inside of the box if there is no gain to it in strength or sound.

[j-roadtatts 1,129]

no gain in strenght, And as far as audible differences, I personally think that fiberglass resonates at a higher freq than MDF.

[DiabolicCustoms 4]

Cool, thanks man. there will be no fiberglass going in this box.

[j-roadtatts 1,129]

Cool, thanks man. there will be no fiberglass going in this box.

GOOD CALL.

I saved the fiberglass I had bought for my enclosure and built my speaker pods with it. Best of luck.

[DiabolicCustoms 4]

Thanks again

[antonmiller 8]

IIRC I gained .2 db from resining my box.... lol, not much but hey who knows it could be instlal to install based.

[ibanender 2]

I didn' t bother reading any posts but 1, and I had a request from somebody to post, so:

FIberglass resin can't weaken layers of MDF. Why? MDF isn't layered, it's compressed saw dust. If it was layered, it would be called PLYWOOD, because the WOOD has PLYS. If you've ever actually fiberglassed MDF, you'd know that it doesn't absorb into it, certainly not 1/8". It sticks to the surface and that's it. If the MDF was sanded with 400 grit or higher sand paper, its possible you can actually pop off resin from the wood.

If it "weakens" wood, wouldn't you ALWAYS lose performance? I've never lost from fiberglass. I've either stayed the same or gained as much as 2 dB, after doing it in probably 50 boxes. The only adverse effect is often a slightly higher impedance rise as a result of the box being sealed better, however, your efficiency also increases so it levels out. In terms of audibility, if somebody says they can hear it, you should punch them in the balls and then have them get their ears checked. That's as bad as saying they can hear <1% distortion in their sub amp.

[j-roadtatts 1,129]

I didn' t bother reading any posts but 1, and I had a request from somebody to post, so:

FIberglass resin can't weaken layers of MDF. Why? MDF isn't layered, it's compressed saw dust. If it was layered, it would be called PLYWOOD, because the WOOD has PLYS. If you've ever actually fiberglassed MDF, you'd know that it doesn't absorb into it, certainly not 1/8". It sticks to the surface and that's it. If the MDF was sanded with 400 grit or higher sand paper, its possible you can actually pop off resin from the wood.

If it "weakens" wood, wouldn't you ALWAYS lose performance? I've never lost from fiberglass. I've either stayed the same or gained as much as 2 dB, after doing it in probably 50 boxes. The only adverse effect is often a slightly higher impedance rise as a result of the box being sealed better, however, your efficiency also increases so it levels out. In terms of audibility, if somebody says they can hear it, you should punch them in the balls and then have them get their ears checked. That's as bad as saying they can hear <1% distortion in their sub amp.

I agree that MDF is not layerd like plywood, but the resin created a top layer that seperated VERY easy. IN my case, When I routered my sub opening , drilled holes for my t-nuts, or added any screws through the MDF, the to top 1/8-1/16 of MDF was VERY brittle and DID INFACT seperate. The resin did soak in to the MDF 1/8-1/16 inch in my case.

I DON"T compete SO I can't vouch for the DB gain but, I CAN agree that the fiberglass made the box peakier sounding SO i believe that would make higher DBs.

I am no expert, and can only assume that alot of different factors go into each exsample. for exsample I store the MDF and resin near a heat source up to the minute I use it, maybe opening the MDF pores up some, plus the resin is VERY runny when warm.

I will dis-agree that resin can be poped back off, The resin will take the top layer it created with it.

If you are rating perforance by a meter, than maybe i could agree that nothing is lost. In everyday use I think nothing is gained from fiberglassing the inside of the enclosure, only money lost from using it.

I think if the resin is whats sealing a box you should make better cuts or use wood glue.

Like I said before if you are not competing than don't waste your time. IF YOU ARE COMPETING that all reasoning is out the window because you guys are INSANE with the things you will do to gain a little on the meter.

SO I will admit that I have only done the one enclosure with resin, and am no expert on the subject, but will give my thoughts and ALSO want to hear about other peoples experiences on the matter.

Please don't think I am arguing with you or acting like a know-it-all, As I am here to learn like everybody else.

[j-roadtatts 1,129]

And where were you and the guy that requested you when I was posting the first topic?

All jokes aside, What benifits do you, ibaneder, see from using fiberglass inside an enclosure for daily use?????

I know your reason for a comp box, but want to hear if you personally think its worth it for a Daily Driver that not pushed to it limits every time its used?

SO MAYBE who ever requested your presents could request it again.

[j-roadtatts 1,129]

BTW I can think of good and bad reasons to use fiberglass in a sub enclosure, Is why I am asking your thoughts.

AS far as me saying that it makes the MDF weaker is because thats what I was told to believe SO I thought of reasons why BUT like I said I can think of reasons both ways.

YOU sound like YOU have more experience than others SO PLEASE give us more info from your experiences, SO WE ALL CAN LEARN.

[The enD 467]

And where were you and the guy that requested you when I was posting the first topic?

I summoned him, the all mighty Sean.

jk

Actually I didn't. I chat him him often and I asked him about fiberglass and boxes and he says it is cool. Then after some time I see this thread and saying all this things about fiberglass so I wanted him to comment, but rather in the chat program not here... Then I saw he wrote and got my "comment on this thread" wrong

But he hates misinformation so...

[DiabolicCustoms 4]

Hi, I have just decided to not go with glass as its not going to be a solely competing box. NOT that i wouldn't do it for a everyday thing. Its one of those discussions where everyone agrees to disagree i think. My box is nice and sealed up with wood glue and caulking and i have some nice transitional 45's in there. I think that'll do. But if we can get some serious examples or scientific reasoning than by all means lets continue to explore this topic.

[j-roadtatts 1,129]

I would love to hear more real life experiences with the glass, as thats about as scientific as its gonna get.

I on the other hand do NOT want to be reposible for mis-information, SO i will admit I have VERY LITTLE experience on the subject.

I can think of pro's and con's BUT have no real knowledge, SO I will STFU now.

[ibanender 2]

I didn' t bother reading any posts but 1, and I had a request from somebody to post, so:

FIberglass resin can't weaken layers of MDF. Why? MDF isn't layered, it's compressed saw dust. If it was layered, it would be called PLYWOOD, because the WOOD has PLYS. If you've ever actually fiberglassed MDF, you'd know that it doesn't absorb into it, certainly not 1/8". It sticks to the surface and that's it. If the MDF was sanded with 400 grit or higher sand paper, its possible you can actually pop off resin from the wood.

If it "weakens" wood, wouldn't you ALWAYS lose performance? I've never lost from fiberglass. I've either stayed the same or gained as much as 2 dB, after doing it in probably 50 boxes. The only adverse effect is often a slightly higher impedance rise as a result of the box being sealed better, however, your efficiency also increases so it levels out. In terms of audibility, if somebody says they can hear it, you should punch them in the balls and then have them get their ears checked. That's as bad as saying they can hear <1% distortion in their sub amp.

I agree that MDF is not layerd like plywood, but the resin created a top layer that seperated VERY easy. IN my case, When I routered my sub opening , drilled holes for my t-nuts, or added any screws through the MDF, the to top 1/8-1/16 of MDF was VERY brittle and DID INFACT seperate. The resin did soak in to the MDF 1/8-1/16 inch in my case.

I DON"T compete SO I can't vouch for the DB gain but, I CAN agree that the fiberglass made the box peakier sounding SO i believe that would make higher DBs.

I am no expert, and can only assume that alot of different factors go into each exsample. for exsample I store the MDF and resin near a heat source up to the minute I use it, maybe opening the MDF pores up some, plus the resin is VERY runny when warm.

I will dis-agree that resin can be poped back off, The resin will take the top layer it created with it.

If you are rating perforance by a meter, than maybe i could agree that nothing is lost. In everyday use I think nothing is gained from fiberglassing the inside of the enclosure, only money lost from using it.

I think if the resin is whats sealing a box you should make better cuts or use wood glue.

Like I said before if you are not competing than don't waste your time. IF YOU ARE COMPETING that all reasoning is out the window because you guys are INSANE with the things you will do to gain a little on the meter.

SO I will admit that I have only done the one enclosure with resin, and am no expert on the subject, but will give my thoughts and ALSO want to hear about other peoples experiences on the matter.

Please don't think I am arguing with you or acting like a know-it-all, As I am here to learn like everybody else.

If resin absorbed in your MDF, you're using the crappy MDF. Yes, there are 2 grades of MDF, which is why I dont use it anymore. Every store stocks the MDF that sucks, is very flexible, and is typically 1-2 dB quieter. It breaks apart very easily too. I highly doubt resin is like Noxema, I don't see it opening pores. I didn't say you wouldn't take wood off with the fiberglass, but you also missed the part about it being super smooth. With any adhesion, a roughed up surface will adhere better.

Wood glue does not fill gaps, so using glue will not fix a rough cut problem. Not everybody has a table saw (including myself) and they may not be able to make perfect cuts with a circular saw. Even so, people often use silicone or caulk to fill gaps. If you think fiberglass sounds more "peaky", you should judge SQ, because your psycho acoustics are taking over and everybody with expensive equipment will win. You would have to gain at least 1 dB at a given frequency to hear it AND what if your linearity isn't perfect and you gain that dB where you needed it. Wouldn't that make it sound better?

Does it have its place in a daily application? Maybe, depends on the application and the builder. Does it have its place in SPL? It sure does.

[shizzzon 461]

i guess the mdf that is sold in my area is the good stuff because i've had it rained on before and i dried it off and still never had problems with it.

I've never had any problems with mdf around here... and we build lots of boxes around this area.

I am planning on going with 2x4s and Oak with my next build just because it's thicker and heavier.

[j-roadtatts 1,129]

The MDF I used came from Lowes, for what its worth.

I do NOT have a table saw either, so I hear you about the cuts.(just joking on that one,hehe)

The peaky I refer to is not from listening to the box, but knocking on it, I guess peaky is the wrong word maybe, When knocking on the box, the resonate freq. of the MDF sounded higher. My bad for wrong use of words.

I don't want to agrue with you guys, I want to learn what your thoughts are on the subject. I started fiberglassing my enclosure and was told not to waste my time. My box is in a DD and is more geared toward SQ. I was using the fiberglass to strenghten the box and also to seal air leaks. WELL when PPL with more experience than me, tell me its a waste of time, I listen BECAUSE If I don't its like telling them to "F" off, and was pointless to ask thier advice in the first place if I am NOT going to use it.

SO here we are today dicussing the subject, Like I said I personally can think of pro's and con's to using it.

In competition I "guess" that it could be dependent from one car to the next and should be tested.

For an everyday box used for normal music listening and an occasional burp, what benifits do YOU GUYS (ibanender, shizzzon, anyone that has actually had a fiberglassed box) think the benifits could be. i.e. material strenght gains, maybe less flex, help or hurt SQ, What changes in sound where achived, any change in box tuning, possibbly peakier/flater response curve, db gain/loss, more mechanical noise, warmer sound, slow down/speed up sound waves/air flow, destructive destortion/canellation from reflections inside the box, affects from rapid wheather changes, tranfer of car borne noises through material???????? I would LOVE to hear from people that have REAL EXPERIENCES and not just opinions.

The last one was put on the list BC my box seems to transfer trunk noise in to the cabin more. (sealed trunk, forward facing)

[kirill007 52]

A box will sound worse with Fiberglass, but you will not hear it.(the stronger a box is the peakier it will sound.)

If u don't want to spend the few dollars for fiberglass, then don't do it.

But if you use fiberglass, you can make it louder.(not only because it's stronger, but also because you can sand it really smooth which will increase db's)

Don't use only resin, like some people do, resin doesn't helps.

It's the fiberglass that makes it strong.

There will be less flex, hurt SQ(inaudible) ,peakier response curve, db gain(in all the cases i've seen), no change in mechanical noise, no audible difference in sound, air flow get's better(cause you can sand it smooth, and maybe even polish it), no difference in distortion,or cancellation , Really don't know about the last one.

Edited April 28, 2010 by kirill007