On 2011-08-12, Dick Pierce wrote:
| -- make it more efficient -- use less power for the same volume
| (the power limited is limited, so this is a concern.)
|
| Porting an enclosure WILL NOT make the system any more
| efficient. Not in the least. Ported systems CAN be more efficient,
| not because they have ports, but because they have drivers suited
| for the enclosure that result in electromechanical parameters that
| mke the DRIVERS more efficient to begin with. ...
So I have even more to learn about this than I thought -- and I
thought I had a lot to learn before.
I'll go ahead and not add a port then.
| You simply cannot just take a pair of speakers, jam them
| in a box, stick a port in it, and expect 1) for it to work
| reasonably well, 2) for it to have "better low frequency
| response and 3) more efficiency. It simply does not work
| that way.
Sorry I used the wrong terminology. I was under the mistaken
impression that adding a port could help alleviate the limitations
imposed by the overly small case to some degree -- especially for
lower frequencies -- but at the cost of some sound quality.
(Obviously it's not so simple.)
And then I went looking for instructions on how speakers are typically
designed and got lost in all the calculators available and such.
| A speaker is a SYSTEM composed of drivers, enclosures and
| amplifiers.
Everything is a trade-off ... that much I understand. And I know that
keeping it small is a serious limitation, but going much bigger
becomes difficult.
| If I were hired to do such a job, the first thing I'd do is sit down
| and try to come to an agreement about what constitutes "efficient"
| and "good low frequency response".
My goal is five hours run time, with the volume being as loud as it'll
go and still achieve that goal with the energy available. At least I
assume that the battery capacity is the limitation -- it may not be.
The batteries should be able to provide 20 watts for 8 hours if the
rated capacity can be trusted, though in my experience it rarely can.
(It's hard to quantify just how "loud" I want it to be -- after all,
this thing is going to only be a few feet behind me.)
"Good low frequency response" was just me using the wrong terms. I
figured that the small case size would hurt low frequencies more than
higher frequencies, though I guess what I really meant was "sounds
good".
| Things like XMax play no role at this stage: it's on;y relevant in
| determining the MAXIMUM output.
It didn't seem terribly relevant to me either, but (some of) the
calculators were asking for it.
| Then again, just sticking what you have in the box may well be good
| enough for a bike. That's for you to decide.
It does work pretty well so far. I just figured I could make it work
a little better by going a little beyond "jamming some speakers in a
box".
--
Doug McLaren,