Jaycar CW2196 8" woofer box size

[Nightlamp]

Hello.

I'm new to this forum thing, so sorry for hijacking a thread before.

I have 2 Jaycar CW2196 8" woofers
These:
8" Paper Cone Woofer - Jaycar Electronics

After trying them in an air-free setup and IB setup, I've concluded they need to be boxed. However I have very limited space in my car!

So.....
What would be the smallest enclosure they can fit in and work properly?

Currently I'm thinking of putting two in 18.5L internal volume box (23.1L external volume).
I'm thinking of not using dividers between them, because 9.25L per woofer might be way too small. Yes I've read that having them in one box effectivly means the volume is halfed if they are both working, but I'm hoping that it's to my advantage and that it's not just 'halved'.


Anyway, 18.5L internal volume...
Is this okay??? What could happen??? Would I be better of having a very small port hole to relieve some pressure???

Box measurements:
30cm wide, 70cm long, 11cm deep (all outside measurements, with 19mm softwood thickness)
Also, I've noticed it's magnet vented and this would leaves me about 4/5cm of space between the magnet and the backboard, is this enough???



PS, these woofers sound pretty bad in a air free setup or an IB setup.

[AllenB]

I have a pair of these in 17l (each) enclosures. I feel they could go down to half that but that is just a guess.

You asked whether you should use a divider, this is optional. A port to relieve the pressure? No, but you might look at a ported enclosure for other reasons (I haven't and can't answer that).

Are you using these as subwoofers? Two reasons for asking, firstly I would want to look at other enclosure types unless you have a compact car. Secondly, they don't sound all that great in the upper midrange.

[Nightlamp]

What makes you feel that they could go down? I'm going to attempt to put them in a smaller 17L (or so) box tomorrow.
But... how would I know that it's not right? Would it just distort as if it where not box?


I don't know, I was applying common sense thinking that too much pressure will buildup inside, so I thought a hole was needed...

I'm using them up to 250Hz, so kind of as a subwoofers. Run off an amp.
I'm fairly limited in space. So I can't look at another position in the boot. However, I can look at another 'shape', but I don't know if this will produce result in odd sounding.

The kind of shape I was thinking is a bit hard to describe, so here's a drawing.
The red area is the shape I was intending to do, with the above dimensions.
This new shape will add about 60-70% more volume, but it's an add shape.
And yes in pic two, that's how the magnet will come...

http://www.imgjoe.com/x/screenshvxv.png

[AllenB]

Originally Posted by Nightlamp

What makes you feel that they could go down?

It's a hunch, but I looked at the specs and you'd see a Q of around 1 with a resonance at around 100Hz. This isn't ideal but it isn't unreasonable either. Furthermore, mine sound happy enough in the 17L boxes making me think they could go down (I haven't tried to do anything with the boxes except contain the woofers)

Two woofers in a closed box halves the effective volume for each, divider or not. There is no need to relieve the pressure, that's what closed boxes do. The smaller box would mean more upper bass, less lower bass and greater power handling but don't go any further than half of 17L per woofer.

Do you know what you expect out of these woofers? Are they your main subs or just woofers?

[Nightlamp]

I'm not using the main sub anymore. It was a 12" and I've decide I need my boot back. But I just wanted a bit more kick then the 6.5" before hand, so I got these. Then I descovered They can't be used airfree... Now the drama to fit them in the smallest box yet sound good.
Note: they sound crap without a box.

Can I just confirm, your saying it could posibly sound better in a smaller box? I would think if with 17L it sounded bad, that it need more, not less?

So a small box would not distort the sound? I was told by a JB specialist this is how it would work. But by the sound of it, your saying it should be able to handle more, and it just changes the sound quality?
Speaking of that, so your saying there will be lack of sub 50Hz notes, in contrast to it being in a bigger box?

Did you have a look at the 'odd' box I'm thinking of making. Should I do that just for the addition volume or just stick to a normal shape?

[AllenB]

Originally Posted by Nightlamp

I just wanted a bit more kick then the 6.5" before hand, so I got these. Then I descovered They can't be used airfree... Now the drama to fit them in the smallest box yet sound good.

I bought these so that I could use a small box. If I remember correctly I was thinking of putting them in 20L total bandpass enclosures. This might be one option.

Can I just confirm, your saying it could posibly sound better in a smaller box? I would think if with 17L it sounded bad, that it need more, not less?

It sounds OK in 17L. No doubt it isn't optimised but it works well for what I need from it. Have you looked at isobaric mounting? If you put the drivers back to back, you can put them in a much smaller box. I suspect the bandpass box might be a good choice for a sub, as long as it is designed properly.

So a small box would not distort the sound? I was told by a JB specialist this is how it would work. But by the sound of it, your saying it should be able to handle more, and it just changes the sound quality?

Traditional thinking is that small boxes cause quality issues. This is true, but I think overrated.

Speaking of that, so your saying there will be lack of sub 50Hz notes, in contrast to it being in a bigger box?

Yes, but subs for a car don't always require the same kind of extension as for a domestic listening room.

Did you have a look at the 'odd' box I'm thinking of making. Should I do that just for the addition volume or just stick to a normal shape?

I think you should decide the following things. How low do you want to take these considering your cabin, how loud, and how high do you need them to go. Decide on a cabinet style then try to fit it in the space you have.

[PeteMcK]

If you do a search, you'll find I've used pairs of these in 50L boxes, measured parameters in that thread.
A quick Unibox sim shows that with 18.5 L tuned to 48Hz will give an F3 of 47Hz
17L tuned to 47Hz gives an F3 of 49Hz

2 drivers in 18.5 L tuned to 55Hz will give an F3 of 64Hz, you can't fight the laws of physics....

re:"Secondly, they don't sound all that great in the upper midrange" I'll second that....

[Nightlamp]

PeteMcK
Yeah I saw your thread. I didn't want to hog it...
I can't tune it because it's a sealed box. Or can I?
I'm trying to get my head around by what you mean with your post?
Are you saying it will not sound good with such a small box? Sorry...


AllenB
I don't think I'll be able to acually do a isobaric setup. It seams more impossible then others.
Not really sure what you mean by "how low", "how loud", "how high" desisions.
I want them to go as low as possible (we are talking about Hz right?) and go up to as high as possible till it starts to distort. And obviously be as loud as possible
I think between 40 to 150/200Hz is where I want it, because it want them acting more as woofers then subs. They don't need to win loudness comps, so that's why I thought a small box would be okay. Right?

Main aim of this is for fairly good sound that adds a little bit more bass to the front split system.

I've made a box, I'll hock it up tomorrow and let you all know what it sounds like.

[AllenB]

The reason I asked those questions was to find out the enclosure type you needed. For example..

An isobaric setup could be as simple as putting the drivers front to front before screwing them in a normal sized hole in a baffle. This would limit the upper crossover frequency because the sound coming out the back of the drivers is only good for the bass.

If you want low frequencies and high power, you might look at a bandpass enclosure.

If you want the midrange to come through and you want low frequencies then you may need to go vented (ported). These enclosures use carefully selected box sizes and port sizes, by the way.

The closed box is less critical, usually sounds good, but isn't especially good at any of the extremes in performance.

[Nightlamp]

So I just tired making an isobaric. It didn't sound too good... tried switching the negative and positive, but that didn't work. Basically it wasn't loud and sounded the same as a closed setup I tired earlier. Does this sound right? So on the same box I made another hole to fit the other sub and made a type of bandpass but fitting an equally sized chamber after the speakers.

Maybe I didn't make it right, but to me it just seamed like that setup was for low frequencies only. In the cabin I could only hear the type sub frequencies. Sounded much like my 'proper' sub setup before. Being after a mid range kick, with a little bottom, I decide to move on and make another setup.

I took off the 'extension' and played it like that. I had a boost in mid range with a little loss in bottom frequencies. However I did notice the woofers got distorted quicker (with more volume). Does this sound correct?

Then I started on a new box, bigger (knowing it will not fit how I wanted it too, but I wanted to test it). This was just a normal setup, but ported. As I was told ported needs to be bigger. This was now about 35L for the pair. The sound was fairly smiler to the sealed smaller box. However I did notice it didn't distort so quick. Now I don't know if this is because it's ported or because the box is 35L (over 20L). I didn't notice any extra mid range. Actually I think I had more mid range with the smaller non ported!

And this is where I am at. Should I try porting the smaller box?
In theory, what was meant to be the sound difference between the bigger ported and non ported normal setups?

I have now accumulated 4 boxes.