Ok guys, thanks for your suggestions. I guess I'll start humbly and leave the more advanced builds for future projects 
So I did Dave's homework and think that I found a suitable driver that is available to me: DSA90-8 has Fs of 66.62Hz and Qts of 0.37
Now I thinking about amps and have a question about Yatsushiro's suggestion. Is it even possible to use such a small amp with a speaker that has a maximum power of 50W?
So I did Dave's homework and think that I found a suitable driver that is available to me: DSA90-8 has Fs of 66.62Hz and Qts of 0.37
Now I thinking about amps and have a question about Yatsushiro's suggestion. Is it even possible to use such a small amp with a speaker that has a maximum power of 50W?
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The minimum volume for bass of the DSA90-8 1,5l, which makes your speaker outer volume around ~2l. f3= ~70Hz. You have to use a passive radiator (=BR) because the port won't fit in the enclosure, a sealed use does not work if you want bass (f3=130Hz).
An alternative could be the TB W3-1401SD with approximately similar results, I'd probably use the DA though.
An alternative could be the TB W3-1401SD with approximately similar results, I'd probably use the DA though.
Don't forget to increase the enclosure volume by 135cm³, that's roughly what the port takes up, it does not count towards the enclosure. For a mobile speaker I don't like ports very much because moisture/water can get into it and the port air-cannons mold spores through the room two weeks later back home.
Oops, check the math.
The volume for a .75" dia x 4" long (20 mm x 100 mm) cylinder is ~ 32 cm^3 (~ .032 liters). The actual displacement volume will have a slightly reduced length, due to the enclosure thickness, but probably offset by the port wall thickness. Either way, .032 liters is somewhat insignificant compared to 1.3 or 1.5 liters, so you'll still be in the ballpark. That being said, it's a good idea to account for it, as well as the magnet/basket structure of the driver.
You are right, I cannot fathom how I came to that number. 
E: I totally messed up with in/cm conversion
The volume taken up is the outer dimensions, not the inner ones but that doesn't change it's insiginificant and of course, you were right there too.
@fabster: The length of an L- (or other form) shaped port is always calculated by the center/middle line. Usually a cm more or less doesn't change much, if anything but at very small or extreme ports it's a good idea to check it. To verify the tuning frequency you can either measure the impedance, the lowest point between the two impedance peaks is the tuning frequency, or you can judge it visually. To do that, use a sine frequency generator (or app etc) and watch the excursion. The tuning frequency is at the f the excursion is the lowest in the bass range. For fullrange drivers or very small drivers that's often hard to see, the Dayton DSA90-8 got a very high xmax of 4mm (especially at that size!) so it should be visible (watch from the side).
E: I totally messed up with in/cm conversion
The volume taken up is the outer dimensions, not the inner ones but that doesn't change it's insiginificant and of course, you were right there too.
@fabster: The length of an L- (or other form) shaped port is always calculated by the center/middle line. Usually a cm more or less doesn't change much, if anything but at very small or extreme ports it's a good idea to check it. To verify the tuning frequency you can either measure the impedance, the lowest point between the two impedance peaks is the tuning frequency, or you can judge it visually. To do that, use a sine frequency generator (or app etc) and watch the excursion. The tuning frequency is at the f the excursion is the lowest in the bass range. For fullrange drivers or very small drivers that's often hard to see, the Dayton DSA90-8 got a very high xmax of 4mm (especially at that size!) so it should be visible (watch from the side).
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Haha classicE: I totally messed up with in/cm conversion
Thanks so much both of you, especially for the tip how to check the Fb.
I'm still not sure about the amplifier.
is this true for this driver as well? Even though it says 20W? If yes I might get the amp and the Bluetooth receiver that Yatsushiro suggested. In case I want to build a second speaker to make it stereo
I'm still not sure about the amplifier.
is this true for this driver as well? Even though it says 20W? If yes I might get the amp and the Bluetooth receiver that Yatsushiro suggested. In case I want to build a second speaker to make it stereo
The amp isn't bad but I would not recommend it for this box. The issue is it only delivers 5W at 2 Ohm. Since your driver isn't 2 Ohm but 8, it only gives you 1,8W (mathematical 1,25 but whatever) - and that's not enough for outdoors. It doesn't say if you could use a higher voltage power supply, that might get you more power. If you look at the power, always check at which impedance it's specified, you might get a lot less on your setup.
For 5V there are very few satisfying amplifiers for 8 Ohm. What runtime do you need?
Lojzeks suggested Wondom amp would deliver ~8-10W, it starts at 10,8V, (none of the Wondom amps are specified below 10V). You should expect a lot shorter runtime because of the DSP, they say the board draws 80mA idle (TDA8932: 40mA) but I've got their DSP module which needs 125mA idle alone. If it's not about the money, they got a convenient set with BT, battery holder/controller but with the heatsink and size it's not exactly light, though the battery will always be the heaviest of it. I don't know if they got a similar amp with less power.
If you go with 12V, the TDA8932 is a good choice on 8 Ohm, it gets you ~10W max at 8 Ohm (~8W@1%THD) and the sanwu boards are still dirt cheap. The board starts working from 10V up according to the data sheet, mine still runs with 8V but I would not rely on that it's always and with all boards the case though. It's really tiny, with 45x31mm it's smaller than a matchbox.
