Newbie - Advice on material selection

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Newbie - Advice on material selection - Speaker enclosure

Author	Message
ta_sjo	ta_sjo posted 11 Years Ago HOT Topic Details
Group: Forum Members Posts: 4, Visits: 8	Hi there I'm a complete composites noob. I've never glassed anything in my life, but have some experience watching! I need to create an irregular-shaped speaker enclosure to go in my car, a sub-woofer box. Most car audio guys just tape up the area, wax it up, and start to lay the chopped stranded mat into place.. sometimes strips of normal glass and layer it up.. usually these end up about 10mm thick.. Problem is, for a sub-woofer enclosure, you need it very rigid so that it doesn't flex as this loses you efficiency and sound quality. I have a fairly lightweight car so want to add as little weight as possible. I would be keen to hear some recommendations on the best type of composite to use to keep the weight down whilst creating a very rigid enclosure... I have noticed the bi-axial glass cloth.. Here's a photo of the boot... the top of the enclosure will be routed MDF.. and possibly a frame around the edge so probably just the bottom/irregular section composite.. Thanks in advance for any responses
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coleio	coleio posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 68, Visits: 285	ive alot of experience with sound system enclosures, id advise using as little composite materials as possible. i have heard that materials like fibreglass dont resonate the sound well. never actually seen the data to back it up what i heard from countless reputable sources in the industry
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ta_sjo	ta_sjo posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 4, Visits: 8	coleio (23/03/2014) ive alot of experience with sound system enclosures, id advise using as little composite materials as possible. i have heard that materials like fibreglass dont resonate the sound well. never actually seen the data to back it up what i heard from countless reputable sources in the industry Thanks for your reply. I can confirm that the majority of speaker enclosures used in the top level of sound quality competitions are typically using fibreglass.
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Hanaldo	Hanaldo posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 2.5K, Visits: 28K	If rigidity is a requirement, why not make it a sandwich structure? Do you have access to a vacuum pump at all? If so, you could do a sandwich structure using 1 or 2 layers of woven glass, a 2mm Soric core, and then another 1 or 2 layers of glass. Could do it with csm as well, but woven is stronger so you can get away with less layers. Alternatively if you don't have the materials to vacuum bag, you could use Coremat instead of the Soric. Vacuum bagging is always going to be better, especially with the shape you are working with there, but it would be doable via wet lay. Just be aware that if you are planning on using polyester resin, you'll either want to be sure that your cars boot was painted with 2k paint, or you'll want to use PVA release agent in addition to the wax. Wax on its own won't stop the styrene in the polyester from attacking the solvents in 1k paints. Edited 11 Years Ago by Hanaldo
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ta_sjo	ta_sjo posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 4, Visits: 8	Unfortunately no, I don't have access to a pump (that I know of!). In fact i'll be buying all tools/materials from scratch to do this job, it's also unlikely i'll be doing many more jobs like this in the future I did look at a sandwich approach but was unsure how it'd work with all the contours. I'll have a search around to see if I can find any examples. With regards to the resin; yes polyester is typically used. The surface is usually prepared with either plastic lining or masking tape before the resin/mat is applied.
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coleio	coleio posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 68, Visits: 285	ta_sjo (23/03/2014) coleio (23/03/2014) ive alot of experience with sound system enclosures, id advise using as little composite materials as possible. i have heard that materials like fibreglass dont resonate the sound well. never actually seen the data to back it up what i heard from countless reputable sources in the industry Thanks for your reply. I can confirm that the majority of speaker enclosures used in the top level of sound quality competitions are typically using fibreglass. your right they do, but they are going for high db, not sound quality. i presume your going for quality considering its a boot job and not a full interior job. chopped strand fiberglass doesnt resonate sound well, simply down to the random composition of the fibers.
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ta_sjo	ta_sjo posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 4, Visits: 8	coleio- Actually, I am talking specifically SQ. The majority of competition-winning SQ cars tend to have their sub mounted up-front, usually replaceing the glove box. In this scenario, due to the constraints of space, custom fibreglass enclosures are the only practical option. Everything's a compromise... Regarding this thread/question, I've done some sums and it seems I may be able to get away with a simple 'cake tin' shape box out of curved MDF. Might give that a shot first and venture into composites if and when I need the additional irregular space below the intended box. Thanks for the discussion folks.
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Fasta	Fasta posted 11 Years Ago HOT Post Details
Group: Forum Members Posts: 468, Visits: 3.5K	This shape you have will be stiff. Do as others have done with packing tape and wax but don't make it 10mm thick. Maybe 3 layers of 450gm chop strand mat. If you wanted to take it to the next level then consider using a thin 2mm coremat (not soric) with a 450gm chop strand each side. That shape will be strong due to all the curvature. Fastacraft Facebook page
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