Drew

iTrader: (1)

i'm wondering if there are any advanages or disadvantages in using fiberglass or mdf to build a box. What do you guys think of this box? http://cgi.ebay.ca/ws/eBayISAPI.dll?...722855534&rd=1
Thanks

Merlin

drew, our kelowna store has started selling these and from what i've heard they are pretty happy with those exact enclosures. they are all made by a shop in kelowna. we did one of those 2 12 boxes for a customer and the things hammered with a set of alpine type s 12's

Ricktc

Looks cool, I always though of doing stuff like that, but I don't really love doing fiberglass that much.

-Rick

geolemon

MDF has superior damping properties - in other wors, it absorbs sound energy.
On the other hand, fiberglass is hard and reflective... so MDF "wins" from that standpoint.

However, a funky baffle like that really wouldn't do any harm, in reality... because of the funky shape.
Sound waves would reflect and simultaniously be broken up, reflecting in different directions off the odd shape.
In fact, I've got a fiberglass spare tire well mold in my car, with no surface resembling anything flat - and I suffer no issues at all.

But it's not a good idea to do any enclosure 100% out of anything reflective, by general rule.
(I've heard of people building a box - and then lining the inside with fiberglass! )

With any "generic" enclosure -
Bear in mind, the enclosure determines how the sub will 'sound'. It's just an electromagnetic piston, after all.

As such, your best bet is always to build an enclosure around two things:
1) your personal expectations
2) your subwoofer's parameters

That being said, generally, the bigger the enclosure, the more "generic" compatible it is.. because even 'small box' subs will simply get more efficient and extend lower in a larger than optimal enclosure... the only trade-off being that your mechanical powerhandling limit can fall below your thermal powerhandling limit - but is that really a bad thing?

I mention this, because this enclosure seems to be pretty decently sized for probably most 10's out there... but possibly a bit squeezed on airspace (after factoring out the sub's own displacements) for a pair of 12's... and that'll lose you both efficiency and low frequency extension.

Ricktc

I wonder if I lined the inside of my box with fiberglass if it would be more efficient, because the way my box is designed all the air from inside the box is supposed to be directed straight out the port as efficiently as possible...

-Rick

Westec

iTrader: (1)

Bingo, the trick is to dampen the fibreglass, and take the the res. in it...

Haunz

iTrader: (3)

Hmm.. I don't think you want a material with good 'damping'... The lower the MOE the material has the better...

MDF has a relativly high MOE, making it a relativly poor choice...

I don't know the MOE #'s for fiberglass, But I have a feeling that a box of equal size/weight is going to be superior to MDF....

The advantage of MDF is that its cheap...

geolemon

Give this some more thought...

Even the highest of high end exotic home audio cabinets - even those that are multi-layer - most often use MDF as at least the inner layer.
And often these cabinets are lined with foam, or stuffed with stuffing - to improve the damping properties of the inside of the enclosure.

The benefit of MDF is that it is has both good rigidity, and good damping characteristics... tough to find in other materials.
Grade A birch plywood is often used as a high-end alternative to MDF, but you are looking in that case at a material that simply has slightly better rigidity than MDF, and at the expense of having slightly inferior damping characteristics than MDF.
...however, car guys might appreciate the lighter weight of birch compared to MDF.

However, that's a tad off the topic at hand...
Again, if highly reflective materials such as fiberglass did have even the slightest acoustical advantage over MDF, you'd see those materials used in high end applications.
There are no steel-lined cabinets in high-end audio. And for that matter, things like plastic enclosures only exist on the low-end of the market, safely away from audiophiles.

Haunz

iTrader: (3)

From what I can tell MDF isnt used very often for high end cabinates at all... ??

I almost always see plywood used in proaudio as well... you need the durability first of all... and its also lighter and quite a bit stronger then MDF. (as you mention)

As far as damping- you want that on the inside of the box, to reduce resonance, particularily resonances created by harmonic distortion.

The box itself should be as rigid and strong as possible.

MDF has less density/rigidity then ply or glass, ect.. and way more then foam or insulation.. so I can't see why youd want it on the inside or the outside of a box.. [img]graemlins/laugh.gif[/img]

The major benifit, like I say, is because its cheap...

I will also agree that in most cases, unless weight or durability is an issue... its just as good as using voidfree ply...