Hey there!
I discovered the Boominator thread and I was amazed by the idea and theperfection in design. Building a own boombox sounds like a lot of fun and I also need one for chilling at the lake in the summer because I hated when friends played music with their phones. The sound quality hasn't to be extraordinary good but it shouldn't be sloppy either. Building the whole Boominator though is a bit over my budged. Time is also kinda tight as I'm going to write "Abitur" (german A levels or smth) in the next months.
This project is my first regarding sound so I don't have any experience with building speakers yet.
My idea was to build the Boominator just in small with 4 Monacor SP-60s and some tweeters or piezos for the higher frequencies. I gonna use a lepai amp instead of the amp6b becaues I have one spare around. That shouln't be a problem as it uses the same chip, or am I wrong?
After reading the Boominator thread I could filter out the following advantages
of the bipolar configuration:
I already did a rough model in Sketchup, which is I think too small because
each chamber has only around 2 liters.
Having read some small things about volume calcultaion for the cabit here and there I still have not much of a clue how to do it properly. All those factors like bipolar design, outdoor don't make it less confusing. I could figure out that a closed design is better if I want to keep it small. Could you please give me some pointers on how to calculate it right or even give me an idea how many liters are recommended.
I'm also very uncertain what the sensivity of the whole box will be.
My simple calculation so far was:
1 Monacor - 90dB for one channel on one side
2 Moncaro - 93dB for stereo on one side
4 bipolar - 94dB because of bipolar gain
This calculation is more than borked but I don't know a better way to do it right now.
Another thing I'm not sure about is what I'm going to use for higher reqencies.
I have to admit that I didn't do much research yet, but maybe someone nice just tells me what is the best way to do it
.
Thank you all in advance!
nanonymous
I discovered the Boominator thread and I was amazed by the idea and theperfection in design. Building a own boombox sounds like a lot of fun and I also need one for chilling at the lake in the summer because I hated when friends played music with their phones. The sound quality hasn't to be extraordinary good but it shouldn't be sloppy either. Building the whole Boominator though is a bit over my budged. Time is also kinda tight as I'm going to write "Abitur" (german A levels or smth) in the next months.
This project is my first regarding sound so I don't have any experience with building speakers yet.
My idea was to build the Boominator just in small with 4 Monacor SP-60s and some tweeters or piezos for the higher frequencies. I gonna use a lepai amp instead of the amp6b becaues I have one spare around. That shouln't be a problem as it uses the same chip, or am I wrong?
After reading the Boominator thread I could filter out the following advantages
of the bipolar configuration:
- makes the construction solid
- augmented bass response of "front"-mounted speaker
- automatic magnetic shielding
- baffle step is gone
- 1dB sensitivity increase per speaker pair
I already did a rough model in Sketchup, which is I think too small because
each chamber has only around 2 liters.
Having read some small things about volume calcultaion for the cabit here and there I still have not much of a clue how to do it properly. All those factors like bipolar design, outdoor don't make it less confusing. I could figure out that a closed design is better if I want to keep it small. Could you please give me some pointers on how to calculate it right or even give me an idea how many liters are recommended.
I'm also very uncertain what the sensivity of the whole box will be.
My simple calculation so far was:
1 Monacor - 90dB for one channel on one side
2 Moncaro - 93dB for stereo on one side
4 bipolar - 94dB because of bipolar gain
This calculation is more than borked but I don't know a better way to do it right now.
Another thing I'm not sure about is what I'm going to use for higher reqencies.
I have to admit that I didn't do much research yet, but maybe someone nice just tells me what is the best way to do it
.Thank you all in advance!
nanonymous
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I have no knowledge on these things - but I'm wondering if the cheapest and fastest route to success might be to buy a used commercial boom-box and re-fit it with your own stuff. You would re-use the speakers and the box - fit your own amp and find a way to mount some solar cells on it.
When you have it up and running the time pressure is off and you can build the one of your dreams at a leisurely pace.
Just a thought.
When you have it up and running the time pressure is off and you can build the one of your dreams at a leisurely pace.
Just a thought.
I've found a thread at 41hz.com where a very similar design is discussed.
The answer to the most of my questions can be found in that thread. Especially this post by grandmaster Saturnus helped me a lot.
I'm still clueless with the calculation of the system sentivity. How do I calculate it properly?
Like suggested in the 41hz.com thread I'll settle with the Dayton ND16FA tweeters with an cap in series. From what I could gather they are cheap and have a good dispartion. I'm sketching a new model with the size of 15cm*15cm*54cm and I'll provide further update of my progress
The answer to the most of my questions can be found in that thread. Especially this post by grandmaster Saturnus helped me a lot.
I'm still clueless with the calculation of the system sentivity. How do I calculate it properly?
Like suggested in the 41hz.com thread I'll settle with the Dayton ND16FA tweeters with an cap in series. From what I could gather they are cheap and have a good dispartion. I'm sketching a new model with the size of 15cm*15cm*54cm and I'll provide further update of my progress
I have a suggestion: visit a few car audio dealers and see if they have any "pulls" from installs in recent model cars. I found a pair of 6x9 OEM speakers at a thrift store recently: they had tiny neodymium magnets and composite frames, which made them incredibly lightweight (made in Mexico, 4 ohms, 20W, no brand name, just various part numbers which don't come in Google searches). (I haven't ~listened~ to them yet, but they seemed ideal for a portable system, possibly mounted in the sides of a thrift-store picnic cooler.)
So do you now what enclosure size you need yet? Are you going ported or sealed? Can you get hold of any other drivers? How loud are you expecting it go? Do you want bass or is this just for casual listening? Does your amp use a single or dual supply (as in it has a positive and negative input or just positive?
Personally I would go with ported as you going to get more bass SPL that way which you'll already be lacking with those small drivers unless your box size is too small to tune it low enough which means you might as well go sealed.
As your question to loudspeaker impedance I assume you have a two channel amplifier you'll be connecting two drivers to one output. You need to match your speaker impedance to the supply voltage to get the best efficiency. So if you need 20W into the two speakers which are connected up to give you four ohm then your best off with a Vs of about 14V or a 12V battery might just scrap it if charged well.
Personally I would go with ported as you going to get more bass SPL that way which you'll already be lacking with those small drivers unless your box size is too small to tune it low enough which means you might as well go sealed.
As your question to loudspeaker impedance I assume you have a two channel amplifier you'll be connecting two drivers to one output. You need to match your speaker impedance to the supply voltage to get the best efficiency. So if you need 20W into the two speakers which are connected up to give you four ohm then your best off with a Vs of about 14V or a 12V battery might just scrap it if charged well.
The /4 and /8 speakers might have different TS parameters, make sure you take that into consideration with your box design.
Whatever one you go with really depends on how loud you want the stereo, and how long you want the batteries to last. Your options basically are:
- Least loudest / most efficient: Use a 2 channel amp, and wire 4 ohm speakers in series for 8 ohms.
- 3dB louder / less efficient: 2 channel amp, 8 ohm speakers wired in parallel for 4 ohms.
- 6dB louder / least efficient: 4 channel amp, 4 ohm speakers.
I'm eager to see how this turns out. I'm building a full-sized Boominator but also want to build a smaller one. I was considering Eminence Beta-8A's but if I can build even smaller with Monacors that'll be excellent.
Whatever one you go with really depends on how loud you want the stereo, and how long you want the batteries to last. Your options basically are:
- Least loudest / most efficient: Use a 2 channel amp, and wire 4 ohm speakers in series for 8 ohms.
- 3dB louder / less efficient: 2 channel amp, 8 ohm speakers wired in parallel for 4 ohms.
- 6dB louder / least efficient: 4 channel amp, 4 ohm speakers.
I'm eager to see how this turns out. I'm building a full-sized Boominator but also want to build a smaller one. I was considering Eminence Beta-8A's but if I can build even smaller with Monacors that'll be excellent.
Thanks for the advice. I heard that car speakers aren't suitable for outdoor Boomboxes because they are designed for small rooms like a car.
Sealed design. For a ported design I would need much more volume I want to keep it as small as possible.
I haven't ordered any drivers yet so yes but I don't want spend much more money than 25€ per driver.
As loud as possible
Yeah casual listening.
Single supply it runs from battery.
Thank you very much, exactly what I needed!
I think the 2nd one is the one I'll use. What about the tweeters what do I do with those? Are they gonna play louder than the monacors if I just parralel them?
Sorry for the late answer I've been on a holiday trip for easter.
All drivers arrived and I got everything I need to start. I'm using two MP-60/8 per channel in parallel configuration.
My problem now is that I don't know how to cut the holes for the 4inch speakers.
They didn't have 9mm or 12mm birch plywood at local diy-market so I bought cheap plywood. Cutting holes with a "circle cutter" for 9,5cm failed because the wood splintered.
Do you have suggestions how I can make nice 10cm wide holes for the speakers?
Do you have suggestions how I can make nice 10cm wide holes for the speakers?
It is possible to saw clean cutouts in plywood. There is always some splintering, but it can be minimized. First, tape up the outline of the area you plan to cut with masking tape before cutting or marking (both sides). Then mark your exact circle on top of the tape. Use a jigsaw with a fine-tooth plywood blade. Run the saw at a moderate speed and take your time. You should wear safety glasses as you need to get right on top of the line to see it clearly with all the sawdust flying around.
The masking tape, though it only has a weak bond with the wood surface, is usually enough to keep the plywood from splintering. (Duct tape can also be used.) This is a generally useful technique for all types of sawing as well as routing.
The fine plywood blade can turn on a very small radius and, with a steady hand, cut intricate patterns--certainly 5-inch circles.
To finish the holes, carefully hand sand with sandpaper. You will probably have a few chipped out areas that will require filler, but these should not be a big deal.
It is possible to saw clean cutouts in plywood. There is always some splintering, but it can be minimized. First, tape up the outline of the area you plan to cut with masking tape before cutting or marking (both sides). Then mark your exact circle on top of the tape. Use a jigsaw with a fine-tooth plywood blade. Run the saw at a moderate speed and take your time. You should wear safety glasses as you need to get right on top of the line to see it clearly with all the sawdust flying around.
The masking tape, though it only has a weak bond with the wood surface, is usually enough to keep the plywood from splintering. (Duct tape can also be used.) This is a generally useful technique for all types of sawing as well as routing.
The fine plywood blade can turn on a very small radius and, with a steady hand, cut intricate patterns--certainly 5-inch circles.
To finish the holes, carefully hand sand with sandpaper. You will probably have a few chipped out areas that will require filler, but these should not be a big deal.
Thank you very much! That was a nice explanation ... I'll try that method later.
Pretty much repeating what ChicagoJTW said - use a jigsaw with a fine toothed blade and take your time. Also make sure the side of the plywood you want on the outside is facing down when you're cutting, as that side will splinter a lot less - the blade will tend to draw splinters towards the wood, keeping them in place, instead of pushing them out.
Normally I'll use a 1/8" round router bit to clean up cuts when I'm done, especially if they'll be visible on the outside.
Normally I'll use a 1/8" round router bit to clean up cuts when I'm done, especially if they'll be visible on the outside.
Update!
This is a prototype made out of cheap cottonwood-plywood. Everything is just screwed toghether and it's already pretty stable and I think there won't be a problem with birch-plywood in the final build.
I wasn't very satisfied when got the lepai amp first, but after bypassing the tone control and op-amps it sounded ok.
I also like how loud those speakers can be. Loud enough for my use ... I would't sit near them longer than a few minutes if you turn them up. The sound though is still good imo. (I'm not an audiophile at all though)
Greets
nano
An externally hosted image should be here but it was not working when we last tested it.
This is a prototype made out of cheap cottonwood-plywood. Everything is just screwed toghether and it's already pretty stable and I think there won't be a problem with birch-plywood in the final build.
I wasn't very satisfied when got the lepai amp first, but after bypassing the tone control and op-amps it sounded ok.
I also like how loud those speakers can be. Loud enough for my use ... I would't sit near them longer than a few minutes if you turn them up. The sound though is still good imo. (I'm not an audiophile at all though)
Greets
nano
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