Outdoors F.A.S.T. speakers... drivers?

[Candisa]

Hi Folks (I'm new here, check the introduction section)!

Me and my girlfriend will be moving to a bought house (after renting an apartment for a while) very soon.
This means we will finally be able to sit outside and have a BBQ when the weather allows it.

We are both people that cannot live a day without music, but it has to sound good to enjoy it, so a set of good sounding speakers would be a HUGE improvement for our garden and barbecue spot.
Now, since we don't want to drag a pair of speakers in and out all the time, we want a pair of great sounding speakers that can be left outside.

The most logical way would be to buy a pair of garden/marine speakers and be done with it, but since most outdoor speakers are built around a midwoofer+tweeter and we like to listen to reggae from time to time, especially when chilling outside, we prefer a Fullrange And Subwoofer Technology system.
This way, we have a pair of small subwoofers with good low-end extension combined with the nice pure sound of a full-range driver.

It seams something like this doesn't exist ready-made, so this means: DIY!

We don't want huge speakers, so 20cm (8") width x 20cm (8") depth x 35cm (14") height is the maximum size we want.

I was thinking about the Vifa TG9FD10/04 as the full-range drivers. Those aren't marine/outdoor drivers, but with their fiberglass cone, rubber surround and ABS basket, I guess they should do the trick and survive rain showers...

The problem is the subwoofer. Because of the limited size of the speakers, the subwoofer can't be bigger in diameter than 6.5". Something like the Peerless SLS6.5 or TangBand W6-1139 should be perfect for the job, but both these drivers have a paper-cone:
- Would it hurt the parameters and sound of the mini-subwoofers a lot if I coated them with something that protects the paper-cone from rain showers? I think about 200Hz would be a good crossoverpoint between a mini-sub and the Vifa TG9, so it doesn't matter if a coating has a negative influence on the sound of the mini-subs above that point.
- Are there any other mini-subs (6-6.5" diameter, minimum 8mm's of x-max) that are affordable and can play well in a small sealed enclosure that have a cone (ànd surround!) that is made out of materials that are more water-resistant?

Isabelle

[jwmbro]

Hi, Given your size constraint, it is going to be hard to get particularly much output out of a small sealed box.

My suggestion would be to use a T-TQWT or Tapped Horn, which allow you to get a lot of output, even using small drivers like 6.5"ers. You won't find one that entirely matches your size dimensions, but you could probably find something with a similar footprint - but taller.

Here's an image showing what I'm talking about:


There are other people on this forum who know alot more about the actual acoustic characteristics than me (bjorno for example), but one of the reasons why I suggest this design is because the driver is in the inside of the enclosure, and not on the outside, exposed to the elements. If you cover the opening with a fairly tightly spaced grill, that should keep any water from raining in, and leaves just condensation dew and the like to consider.

Just a thought.

[planet10]

You can coat the woofers... with the right stuff they usually get better. What is use is water soluable (PVA & Acrylic) so isn't the best solution for outdoors.

Also consider the Mark Audio CHR-70 (also available in Germany as an Omnes if you prefer black), metal cone, rubber surround, plastic basket.

One further comment, probably not a good idea to make the boxes out of MDF.

dave

[chrisb]

Originally Posted by planet10

You can coat the woofers... with the right stuff they usually get better. What is use is water soluable (PVA & Acrylic) so isn't the best solution for outdoors.

Also consider the Mark Audio CHR-70 (also available in Germany as an Omnes if you prefer black), metal cone, rubber surround, plastic basket.

One further comment, probably not a good idea to make the boxes out of MDF.

dave

i.e. regardless of the recursive debates that might easily be encountered as to why some folks (myself included) would avoid MDF for almost any speaker enclosure, the standard varieties are particularly ill-suited to moisture prone environs.

there are of course several grades of exterior rated sheet goods (medex / MDO) etc., that would be far more durable, but availability in your local area could be spotty

and it wouldn't hurt to treat any exposed edges and joints with liberal application of penetrating epoxy resin or exterior grade spar varnish.

[Xeentje]

Well hello there,

I'm Isabelle's girlfriend and thought I'd comment here.

She's gonna use a layer of poly resin on the inside and out of the enclosure to seal it off, which in our opinion should suffice... If not, we can always resort to coating it with a few layers of glassfiber.


Xenia

[Candisa]

I don't have any experience with transmission-line speakers, (well, our B&W DM2a are TL speakers, but we didn't build those ourselves) and since the size limitations, I'd rather not use this project to give it a try.
I'd rather try a TL design later and start with the basics for this outdoors project: sealed enclosures with simple passive crossovers.

About the Markaudio CHR70: Since we'll have a bunch of other things to spend money on (new couches, new freezer, new airconditioning and heating system...), we want to keep this project as low-budget as possible.
The fullrangers will be supported by mini-subs, so the extra linear excursion of the CHR70 compared to the Vifa TG9 isn't necessary. I also wanted to try the Vifa TG9's for quite a while and this project is the ideal excuse to do it, and they're cheaper than the MarkAudio's, so I'm 99% sure the Vifa TG9's will be the fullrangers for this project, unless somebody can give me a very good reason not to use them for this?

MDF isn't the best material to make something that will be put outside, exposed to water, but as Xenia already said, I'll be sealing the enclosures with polyester resin and probably add a layer of glassfiber + extra polyester resin on the outside, so the MDF won't "see" any water or humidity.

Coating the woofers with something that is solvable in water isn't a very good idea for this project indeed. I was thinking of coating them with some kind of resin or waterproofing stuff?

Isabelle

[planet10]

Originally Posted by Candisa

Coating the woofers with something that is solvable in water isn't a very good idea for this project indeed. I was thinking of coating them with some kind of resin or waterproofing stuff?

Isabelle,

I didn't offer any suggestions of something waterproof as i have no experience with anything. Whatever you use you want it to add little mass and to remain somewhat flexible after curing. The 1st things that come to mind, rubber cement or silicon, can not likely be applied thin enuff to be effective, it might be possible to thin the rubber cement, or to find a more usable silicon compound.

As to MDF, i've seen a lot of it "explode" under the assault of the local monsoons, sealed or not. If you are going to fiberglass anyway, why not just use foamcore as a base? (with a multiply or aluminum baffle). A fiberglass skin (both sides) does go a long way to dealing with MDF's sonic inadequacies.

dave

[chrisb]

Originally Posted by Candisa

Coating the woofers with something that is solvable in water isn't a very good idea for this project indeed. I was thinking of coating them with some kind of resin or waterproofing stuff?

Isabelle

I think you might have issues with non-flexible resins that would be suitable for treatment of the enclosures. Notwithstanding the effect of additional mass on sensitivity and Fs, they'd likely seriously affect both the compliance of surrounds and the sonic performance of the cone material (whether paper or plastic based)


It could well be easier to moisture proof the boxes than drivers not specifically intended for such an application, and you might well be advised to consider speakers designed for marine or rugged outdoor use. But if you want to use existing drivers, a quick google and forum search suggests that silicone based spray-on moisture guards (as for fabric / leathers) would be a simple solution (might need occasional re-application)

[sreten]

Hi,

Just some observations :

Clear acrylic should be good for protecting cones.

200Hz seems a little low for the c/o point. As its outdoors you'll want
full baffle step compensation. One way of doing this is make the bass
end 6dB more efficient than the mid/treble and then use a simple
(series?) crossover around the baffle step point to meld the drivers.
A cheap (Apex Jr Audax $1) supertweeter cannot do much harm.

To get this sort of efficiency in the bass your not really looking at
subwoofers IMO, unless you will actually go around 200Hz and EQ
back the Vifa at the the top end to balance the BSC issues.

A couple of 6.5 bass/ mid drivers 8ohm in parallel, with each one
on its own the same senstivity as the Vifa should do the job.
Putting them on opposite faces will give some force cancelling.

Car drivers are essentially moistureproof and many hifi drivers are built
the same way. As the Vifa is $30 or so a two high value poly drivers
are IMO the way to go, but I'm not sure where you can buy from,
so suggesting cheap drivers is difficult.

Two 6.5's with good efficiency in a small box are not going to do low
bass, but you will have the power handling and cone area for some
low bass boost if required, but all domestic speakers struggle outside
a room with low bass, outside a serious subwoofer is needed and
you need to be close to it.

6.5"x6.5"x12.5" internal is not a lot, 1/3 cuft, 8.5L, perhaps a floorstander ?
If you keep it small two 5" bass drivers are as large as you can go IMO.
1/2" stock gives you 10L or so to play with.

For your application the sealed Q should be around 0.8/0.9 IMO.

Where can you source drivers ?
There some cheap Peerless stuff around at the moment.

rgds, sreten.

[Candisa]

The clothing-waterproofing-stuff is something that's been suggested on another forum where I asked this question too, so I guess I'll go with that stuff.
I don't mind re-applying it once in a while. We'll probably get the speakers inside in the winter (water is one thing, but I think ice is a lot worse for any material), so it's not too much of trouble to re-coat the woofers when bringing them back outside at spring-time...

Isabelle