View Full Version : Typical fiberglass box cost?

02-17-2009, 07:08 PM
In attempting to get the maximum amount of enclosure volume and preserve the most legroom in my Miata, I'm considering having my subwoofer box made out of fiberglass. What would be a fair quote for a good box? I can carpet it and even install the sub into the enclosure, but I'm not looking into glassing it myself. The design would be similar to this box (http://forum.miata.net/vb/showthread.php?t=257908) and this box (http://www.cardomain.com/ride/666699/6). The sub is a Soundsplinter RL-i8 S4.

If you're local to the DC area and you do good work, feel free to send a PM.

02-17-2009, 07:22 PM
looks fairly simple....but for glass id charge 150-200 for somthing that small

maybe less

02-17-2009, 07:24 PM
in my area, it would cost an arm and a leg (no real good shops around here).

From what i have seen, a rule of thumb is anywhere from 150%-200% of whatever the cost of making the box is.

02-17-2009, 07:36 PM
if i wasn't getting rid of my Miata i might would try something like that

03-07-2009, 02:17 PM
I was having my wife's window's tinted yesterday and the shop was next to a stereo shop so I popped into talk to the owner. I asked about a rough estimate on fiberglass work and he said that the job would be about $750 + materials! :eek::crazy: He said it's a lot of hours of work and the materials can be expensive since you buy large quantities but then don't use all of it since there's not much of a market for that type of work. I inquired how much he thought materials were just for a DIY job and he estimated $150 if I don't have anything. I thought that was a little steep, but I've never done the work myself. Regardless, at those prices I'll probably look to ol' MDF again.

Any locals feel like moonlighting in the DC area? :)

03-07-2009, 02:37 PM
you don't want to use fiberglass for a box like that. fiberglass' strength lies in areas with curves and it tends to be weaker over flat areas. whenever i build a fg box i always use as much mdf as possible during construction, and ALWAYS in the flat areas.

on average a gallon of good quality resin is about $35 alone and 1 1/2oz chop mat costs about $2.50-3.00 per yard (plus shipping on each and hazmat charges on the resin). then you have to buy a mounting ring, painters tape, aluminum foil, wax, paint brushes, gloves, and a respirator just to start. keep in mind for most subwoofer applications the rule of thumb is to build it up until you can stand on it with no flexing, which usually requires 6-8 layers of mat if not more, per side. then the countless hours of sanding / filling / sanding / filling etc etc.

most people really have no idea how much time, effort and materials are needed to build a quality fiberglass enclosure and just balk at the price. BUT, building a fg enclosure is not rocket science and can be done by the average user but don't expect quality results your first time out. check out www.fiberglassforums.com and you will learn everything you ever want to know and more.

SPL Blazer
03-07-2009, 04:38 PM
The price you got quoted is nuts. I've built a few fiberglass enclosures for my ride and the price depends on how big you want it, but for a small enclosure like your looking for there's no reason it should be more than $500 including materials. Buy the resin at Home Depot or lowes for $35-40 a gallon plus any fiberglass mat. For the baffle you want to go with MDF.

03-07-2009, 05:42 PM
Buy the resin at Home Depot or lowes for $35-40 a gallon plus any fiberglass mat. For the baffle you want to go with MDF.

If you are going to take the time to make something why not do it right? Particle board will do the same thing as mdf but people do not use it, right?

The resin sold at home depot (bondo brand) contains wax and you must sand between each layer of mat to get proper adhesion, not to mention the quality and work time is not the same as something from say US Composites (B440 is the **** - many swear by it).

SPL Blazer
03-07-2009, 11:25 PM
MDF is a stronger material than particle board, another reason why it's used in box building. Hence the name, "Medium Density Fiberboard", and particle board would be considered a "Light Density Board".

I've built a few fiberglass enclosures with what was probably Bondo brand and never had to sand in between layers, and never had any issues with adhesion. As long as you make sure there are no air pockets or bubbles in between layers you shouldn't have any problems.

03-08-2009, 01:20 AM
so you will pay for the better material for one application but not another? a pair of craptastic subs will reproduce sound in the same manner as a pair of Fi bl's, so why pay the extra money for them? it's all about the quality of the product.

03-08-2009, 10:27 AM
I have never had any problems with Bondo brand Resin.I hae recoated when it was still tacky to hours later with no sanding between.
That said a project like this wouldn't be to expensive but can be time consuming with all the prep and finishing required to get it looking nice.I would make th base out of MDF if the area is flat.But if its going in a well or non conforming area then glass will work.You will need at least 6-8 layers of mat for a strong durable box.Cut a speaker ring out of MDF the size of the woofer and use dowels to set it to the height and direction you want the woofer facing.Stretch a layer of fleece over the skeleton and secure it to the base.Soak it with resin and continue to build layers of FG mat till you get about a 1/2" thickness.
Finish it however you want.

SPL Blazer
03-08-2009, 12:06 PM
so you will pay for the better material for one application but not another? a pair of craptastic subs will reproduce sound in the same manner as a pair of Fi bl's, so why pay the extra money for them? it's all about the quality of the product.

If I was going to build a fiberglass enclosure for my BL's then I'd use the same stuff that I used for my old RF P2's or my Orion HCCA Sub. Since I never had any problems with the Bondo brand fiberglass resin there's no reason to waste money on more expensive resin. Sometimes your only paying more for a name. There can be a difference in resin quality, but it's never been proved with the work I've done or by anyone credible that I've heard of.

03-08-2009, 02:12 PM
have you ever used anything other than bondo brand? the b440 from us composites is about the same cost as the bondo **** but 10x the quality. try it some time and you will see a huge difference.

SPL Blazer
03-08-2009, 02:33 PM
The bondo brand is the only one available around here, unless I go to a marine supply or Auto Body supply place, in which case it will cost more than the Bondo brand, and seeing as I haven't had any issues with the Bondo brand why would I want to try something better? It might be 10x better like you say, but if I haven't had any issues with the Bondo brand what difference is it really going to make?

03-08-2009, 02:34 PM
hey beatle, I am in Vienna, if still looking PM me, or IM me on aim.. s/n is same as here

03-08-2009, 04:50 PM
you get what you pay for. enjoy your bondo.

03-08-2009, 04:51 PM

SPL Blazer
03-08-2009, 05:00 PM
you get what you pay for.

Thats true, and since you said the Bondo brand and whatever brand your claiming is better are around the same price I'm sure I've gotten what I paid for. The boxes I've built were pretty tough when I was done with them. Hell, I used a 10 lb sledgehammer to bash them apart when I was done and they didn't break up easily. The Bondo Brand must have done the job right.

03-08-2009, 06:50 PM
enjoy your bondo.

03-09-2009, 10:25 PM
marineeagle28, YGPM.

Based on IDSkoT's pic I may end up just selling the Miata and buying a Cavalier, however.