Swapping factory sealed enclosure for a ported unit.

[aZ`]

Hi guys,
After some inspiration from some other threads on this topic, I would like some info from those who have made this change. The response given from those who have done it has been very positive indeed.

However most who have gone the ported route do not retain the factory cooler (if they had it in the first place), something that is non negotiable for me.

I have taken some measurements and made a cardboard model to fit the factory space in a 210 and plan on making this shape from fibreglass with MDF for added strength.



This design has a total volume of 46L (1.6CuF) and minus driver volume and wall thickness we'll call it 42L (1.5CuF) and i will use an external port. Obviously I will measure the volume exactly once it's made and then tune the port to suit, but this is a start.

My question is this, for those of you who have been so impressed by the switch to a ported enclosure from sealed using the Polk MM2104, do you know the box volume and tuning frequency?

I know Earmark has done this numerous times so any input from you if you are around would be great!

The other thing is, I've always built sealed boxes from my cars (i like the sound) however in the boat output seems to become more of a priority than SQ so any advice on what sort of response curve i should be looking for would be great.

Here is a screenshot of 3 scenarios.
Yellow: sealed enclosure, No doubt similar to what I am experiencing now with the factory enclosure.
Blue: What winISD believes to be the ideal setup, however uses a 57L (2CuF) box which I cannot squeeze in.
White: What I believe could be a good compromise trying to get some output from this little 10.



I read a number of people have tuned their box to 40hz because not much below this is audible in an open environment like a boat, however seems to create a very sharp peak.
I figured 35hz might be a good compromise?

Any thoughts?
Also any thoughts in port direction etc welcome.
cheers
Arron

[aZ`]

Sorry, here's a comprehensible version of that graph.

[David Analog]

Tune the bass-reflex just above the driver's natural resonance. This will give you more bandwidth and protection from content below the tuning frequency where the woofer essentially becomes unloaded and unprotected. Btw, a subsonic filter is always a good thing for a bass-reflex sub. All that wasted movement is counter-productive.
You can tune most any size enclosure to most any frequency in most any size chamber by adjusting the port. However, there is an ideal enclosure size that balances efficiency and linearity. Too small and you undermine the efficiency advantage of bass-reflex. Too large and the enclosure tends to focus on one frequency.
Bass enclosure software programs are typically a little simple and don't reveal everything that is going on. They are also usually predicated on 'small signal' rather than on the higher power & output levels applied to everyday usage. For these reasons, a pro usually goes through a little trail and error beyond the software to find the ideal woofer/enclosure match. Once they find it, they run that same proven scenario again and again, resisting alternative woofers.

[aZ`]

Thanks David. So would you suggest that if I could make a 1.5cuf enclosure that if I played around with the port enough I could get a successful result?


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[aZ`]

OK, I have chosen to give the old masking tape and al foil trick a go to fibreglass the exact contour of the side of the boat and have managed to get a volume of 56L (1.98CuF).
Now this is almost right on what winISD suggests to be the perfect box volume for this driver. Now am i right to go ahead and finish this box or is there something else I should consider? i really only want to make the box once, but am happy to play around with port size and length until I get a satisfactory result.