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! 🙂
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! 🙂
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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
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
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.
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.
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? 😉
You don't have an approximate volume of such a thing in my case? 😉
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 !
but...how much is 'little cabinet volume'? Do I need 10liters at least do you think, or 20, or..?
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 )
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 )
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 🙂
Thank you very much!
If anyone else reading this has a good approximate volume for the speakers, I will still be happy to know 🙂
Looks good and easy to build. And I could just make it double as wide to make room for an extra speaker. I still have no idea of meassurements, so don't know if it's feasable yet 😉
I don't think it can handle the pressure of a single woofer ,and you're pointing toward two ...🙂
It can be made with a PVC pipe.. with lead foil on the inside : it may seem counterproductive for the weight ...but it's not ...well ,a cylinder is not even good for the space available ,but it's more...PISTONIC !!!
Peace , Tony . 🙂
It can be made with a PVC pipe.. with lead foil on the inside : it may seem counterproductive for the weight ...but it's not ...well ,a cylinder is not even good for the space available ,but it's more...PISTONIC !!!
Peace , Tony . 🙂
It is, especially if you want a bass reflex cab. It's also impossible to estimate a cab without knowing it's general parameters.
Might I suggest these woofers instead SP-60/4. They're the same price. They're smaller but by reputable source have excellent bass, and are pretty much full range on their own. You only need a sort of super tweeter. I might suggest a good cheap regular, not piezo, tweeter for this combination, and just cross it with a single capacitor. And leave the woofer filterless.
I might add that they actually have pretty identical real world sensitivity figures. The 6½" is only higher because of bad cone break ups that you'll want to remove anyways.
This tweeter http://www.parts-express.com/pe/showdetl.cfm?Partnumber=275-025 is a pretty good low cost match for the above woofers. Cross them in at about 5-6KHz and you have a fully functional low cost wide angle speaker system that will good pretty darn good.
Oh, and don't ever run woofers in mono unless you have a phase compensating summation circuit. Many modern recordings use phase shifts in the bass range to achieve a punchier sound that would otherwise be possible. This effect will completely disappear with running them in mono, and because of the phase shifts you'll actually end up with less bass overall.
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For a Q 1.2 tuning (for outdoors use) a 3.6 liter cabinet (excluding what the drivers themselves take up) is all that is needed. Tuned to 75 Hz it will give effective response (again in outdoors enviroments) to about 90 Hz.
Get one of these ports Port Tube 1" ID x 4" L Flared for each and trim the length to 50mm (essentially halve the length).
Get one of these ports Port Tube 1" ID x 4" L Flared for each and trim the length to 50mm (essentially halve the length).
Thanks for the reply Saturnus! I've already ordered the woofers I mentioned first, but through a friend which I will see tonight. Maybe he hasn't bought them yet, so I'll see. Atually I think I will try to send them back anyway and change them to those you suggest. I like that they are only 4" and need such a small box. I looked at them before but read several places that small speakers will have less bass, so that's why I chose the 6½" in the first place.
I will not try the fold-out option then, especially when the boxes needed are so small anyway.
Might I ask which capacitor you think I should use?
And what exactly is a super-tweeter? Do you mean I should only have one in total, or just a very good tweeter? And is there some specific parameter I should look for for such a tweeter, like SPL?
I think this will turn out good with all your very specific suggestions 🙂 Thank you very much!
I'll post some pictures along the way.
I will not try the fold-out option then, especially when the boxes needed are so small anyway.
Might I ask which capacitor you think I should use?
And what exactly is a super-tweeter? Do you mean I should only have one in total, or just a very good tweeter? And is there some specific parameter I should look for for such a tweeter, like SPL?
I think this will turn out good with all your very specific suggestions 🙂 Thank you very much!
I'll post some pictures along the way.
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They look good those tweeters, but I see that they are only 10W RMS. Is there a risk of burning them then, since the amp is 2x20W? I'm sure a lot of the watts goes to the woofers, but I also read that high-frequencies uses a lot of watts, so if there is f.x. a lot of cymbals playing on max volume, will this be safe within the 10W margin?
Yes. Actually high frequencies draw very little power. Remember 10W RMS is equal to an 80W+ amp playing music signals.
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