Need a little help on small festival boombox

[ThokN]

Hi there.

I'm building a Boombox for festival use with a budget of around $180, but I have some questions that I hope some of you can help me with

I use a Lepai Class T Tripath TA2020 Amp running on a 12V SLA battery.
The design will probably be something like an old-school ghettoblaster with speakers on each side of a center console with power and volume controls, preferably as small as possible when still maintaining good sound and bass. Possibly I will angle the woofers a bit away from each other to spread the sound some more.

It will be with 2 bass-midrange and 2 piezo-tweeters. I have found these 6½" woofers which have ok sensitivity, size and price, but my main problem with the whole build is that the woofers don't have the relevant data for calculating the correct box-volume. Is it possible to calculate or estimate this somehow?

I'm also a bit confused about whether I should make one large compartment that the speakers share, or if it is better with separated compartments. I would like to have stereo if possible, even though I know it may not make that much sense on such a small boombox.

I read that running in mono can give better bass, and then I could obviously make the speakers share one compartment, but I'm thinking that maybe it is possible to then run the tweeters in stereo and woofers in mono, or is that unwise/impossible?

Finally, do you recommend a ported or sealed enclosure in this particular setup?

Any help will be greatly appreciated!

[wakibaki]

Originally Posted by ThokN

Is it possible to calculate or estimate this somehow?

Yes. See here:- Measuring Loudspeaker Driver Parameters

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[ThokN]

Oh wow!

Well first of all thank you for your response! Unfortunately I don't have the equipment to measure the data as the page describes. Could I do with just an estimated volume? And are you or maybe someone else able to estimate this from the already given data?

It is perfectly fine for me if the estimate is f.x. 4-5 liters or 15-17 liters or something like that, my problem is that I have absolutely no idea of this estimate. I suspect that 1 liter too small or too big doesn't matter that much sonically when it is designed for outdoor festival use, and not careful listening?

Impedance (Z) 4Ω
Resonant frequency (fs) 62Hz
Max. frequency range f3-6,000Hz
Music power 70WMAX
Power rating (P) 35WRMS
SPL (1W/1m) 92dB
Magnet weight 570g
Mounting cutout Ø 149mm
Mounting depth 70mm
Dimensions Ø 169mm
Weight 1.15kg

[ThokN]

Anyone with an estimated box size with two of those speakers?

[picowallspeaker]

The woofer seems nice : it has a foam surround ,so careful as it must be protected with a grill ,but also makes it versatile to the air mass -load presented .
What about a Chinese Box ?? You can build two inner boxes ( with gum stripes on the perimeter ) that collapse into the box when not in use , and can be pulled out (also with the driver's aid !!!) to nearly double internal volume.

[ThokN]

Haha that is actually a very funny idea! Have you ever seen anyone do this? I would love to see that.

You don't have an approximate volume of such a thing in my case?

[picowallspeaker]

If you don't (or cannot) give a proper air mass load to the cone ,it will have a rising tendency but you may want to have a stunning bass and that is not going together with little cabinet volume . 'Foldable' is really not a bad idea ...don't underestimate it !

[ThokN]

but...how much is 'little cabinet volume'? Do I need 10liters at least do you think, or 20, or..?

[picowallspeaker]

You know your needs , and you ('ll) got the driver and you'll have to carry the weight !
Also the size ...It's all about compromises . You can take the mathematical approach and calculate every decimal of a Decibel to maximize the efficiency of the project to fit your needs , ie you can tailor it . Or you can choose the empirical way and start from rough boxes to let them show what are the forces involved ,and how the sound changes as you change the geometry and the volume (also internal stuffing )

[ThokN]

Okay thank you. I actually thought it was sort of mandatory to have the correct box-volume. Didn't know it does not make a crucial difference to have a wrong sized enclosure. Then I will try to make it in the size I think is suitable for practical purposes, and then fiddle around with stuffings.

Thank you very much!

If anyone else reading this has a good approximate volume for the speakers, I will still be happy to know