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Old 22nd August 2014, 01:49 AM   #1
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Location: Prague
Post DIY Portable loudspeakers

Hi,
iīm new here, but i would like to share my idea of building lightweight loudspeakers i could carry on bike trails where we often go riding or for some outdoor parties in parks for bunch of people. I have no expirience in building speakers, so after days spent going through hundreds of pages i am asking you for help, expirience and advices about building my little dream of quality loudspeakers, which i can carry everywhere and wonīt have rattling sound as most of the new "boomboxes" that flooded the market.

Most important parameters to consider are size,SPL and weight.

1. Construction:

I would like to strip some backpack to get only strips with lightweight frame to attach the speakers to or getting army duralumim frame, as those are already well done for heavy weights.
As i am 6ft 4" tall and not skinny, i think i could carry about 20kg for few miles while getting to the destination. Fortunately Prague has amazing public transport system

As i measured my proportions, maximum dimensions shouldnīt be much over 60cm x40cm x40cm (HxWxD) to keep it still comfortable while carrying.

For material i considered birch plywood or MDF (18mm/nearly 3/4"), as are those most used and have best qualities for cabinets as far as i know, but if you know something lighter let me know.
Of course saving size and wieght is always welcome


2. Speakers:

As my main concern is size, weight and SPL, i started to look around for decent drivers that doesnīt require huge volume of the cabinet, have as high sensitivity as possible to save power so rare and feed the crowd with desired decibells. I want to play mostly drum&bass, electronic, trance, but also some classic tunes from 60īs, so i tried to go for lowest frequencies as possible with flat response, becouse i am spoiled from my home Alesis M1 MK2 speakers. Their maximum SPL is 118dB, so that and more is my goal to achieve and reason why i started to look for drivers with sensitivity at least 95dB.

With that in my mind i learned what thiele parameters, used calculator to see what specific speaker requires and produces and got to these speakers i found best in volume,F3,F8 and SPL.

B&C Speakers 10CL51 8/ohm Spec
Monacor SPA-25PA
Monacor SPA-110PA

I will be glad for any other options which are cheaper/better for this idea, as i can compare the drivers only by numbers and graphs.

3. Cabinet

As i want to have full deep bass with high SPL, i was going at first straight for bass reflex with 2 tubes, but i was always amazed by sound of horn loaded cabinets, so i started to look for some horn cabinets and found many interesting projects, especially one bass-reflex/horn hybrid, that makes me wonder, if it would be possible to reduce the size of the cabinet to my dimensions with horn set for higher fequencies and having the bass reflex covering the low frequency cut from the horn and fitting all required electronics, power supply, amps and HF driver on the top of it.
I found some equations that were supposed to tell me dimensions, cut-off frequencies and other stuff, but after a while i got lost and wasnīt able to find some of the required parameters to continue.

Horn calculation datasheet with info
Equations

If i was completely wrong and you simply canīt make horn loaded system this way or with these parameters, let me know so i wonīt waste time trying.

4. Electronics

As i am interested in computers since i was kid, i donīt think soldering my own amplifiers and other components would be problem, i found some components on czech sites, but had troubles finding store with fitting power supply so i wouldnīt have to use some huge DC/DC converter, that would increase the weight. After long datamining i found best solution in ordering customized battery sets from Alibaba.com, where i found supplier who can make any dimensions, capacity, voltage and size i want, so it kind of solved my problem, becouse in Czech republic are small power supplies like batteries for RC ect. very expensive.
As this part is still in research and will strongly depend on selected driver, i will leave it open for discussion, but i was thinking about getting 48V with about 20A to be able to run the drivers at high volume for about 4-5 hours.
I am not sure, if i didnīt forget something, but i think that the main components i mentioned at the beginning should do the job.

a) Power supply - can be customized to fit the requirements
b) Preamp - with or w/o control of HF/LF depends on crossover
c) Crossover - Trouble begins
d) Amplifier - found DIY amp kits from 130 to 500W bridged/nonbridged, research needed to get consumption as low as possible

To be honest, i didnīt even look at crossovers, donīt have any idea how to set them up and how to do it, so ... if you can, enlighten me




I hope that someone will make the effort and read the whole thing. If you did, thank you and feel free to comment, criticize and share expirience about similar projects or anything related to my project

PS: I am working student (not poor,not rich), so my budget is around 300-500$/200-400€, but if there was something that would rapidly improve the quality of the build, i would consider investing more to make it perfect
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Old 22nd August 2014, 05:24 AM   #2
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Shrinking a horn affects frequency response, so just stick with reflex
have you seen the Boominator and Halfinator designs? If you're starting fresh, that's probably your best plan
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Old 22nd August 2014, 11:58 AM   #3
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Thanks for information.
I have briefly gone through the Boominator thread, unfortunately all pictures of the work doesnīt wonīt to load, so after all it was only text description, but sounds similar to my idea and also OP reminded me, that i wanted to add solar panel on top of the boxes I had it on my mind, but after looong evening i completely forgot about it.

Anyway, his build looks nice, so i will take some expirience from him, but i still insist on doing it my way I will rather spend hours and days on planning it on my own rather than copying it from someone else and than being lost when somethings go wrong, becouse iīm learning all the theory while planning

Do you have expirience with building the cabinets of other materials than MDF or Ply? I was thinking about epoxide, becouse my family works with metal wires, plates, stones and epoxides, so it wouldnīt be such a problem to get it and make some form to fit the panels in and do any shape i would like.
Guys were mentioning carbon and other epoxides as "hi-tech" or expensive, but if you know what to look for, it gets cheaper than the ply and i think it could be lighter, only thing that worries me are resonances,but with proper attaching it should be stiff, right?
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Old 22nd August 2014, 05:41 PM   #4
JMFahey is offline JMFahey  Argentina
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Quote:
gone through the Boominator thread, unfortunately all pictures of the work doesnīt wonīt to load
Then you have a gross computer problem, solve it first.

Donīt reinvent the wheel, anything you can "discover" is already on that long and excellent thread.

Tons of options and variations.

Post this there, and you can offer your very valuable epoxy glass lamination experience there

Win-win for all.
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Old 22nd August 2014, 10:10 PM   #5
phase is offline phase  United States
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Some of the car speakers are pretty decent in open baffle arrangement, that and a class d amp would be great I would think.
Don't know just what you had in mind, however, whether it's a mobile disco, or playing harpsichord music for the wild birds...
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Old 23rd August 2014, 08:45 AM   #6
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Quote:
Originally Posted by JMFahey View Post
Then you have a gross computer problem, solve it first.
The links are broken.

IMHO, use a pair of neo 12"s, ported, tuned around 80Hz. Forget deep bass from this box, just make the bass it can do hit hard.

Chris
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Old 23rd August 2014, 12:10 PM   #7
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Pictures of a ton of Boominatrs on the facebook fanpage

https://www.facebook.com/theboominator/photos_stream
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Old 24th August 2014, 02:50 AM   #8
JMFahey is offline JMFahey  Argentina
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The 2007 pictures do not open.
I would be stunned if they did

But modern ones do, definitely.

As a free sample, hereīs one, straight from page #540 showing a Boominator wall of sound, including smaller ones ane even a solar cell powered one.

Click the image to open in full size.

I guess you should search for the "mini boominator" or something like that and, of course, build it with your lightweight composite materials technology.

Please post that along the way, Iīm certain itīll be very interesting.
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Old 28th August 2014, 04:09 PM   #9
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The Boominator is a good design but too heavy for a backpack. I have used cardboard sonotube for my mobile PA rigs with great results. A efficient 10" DVC driver in as large of tube as your pack will carry will get you the most boom per lb. of speaker.
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Old 28th August 2014, 04:35 PM   #10
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Quote:
Originally Posted by mr. doom View Post
The Boominator is a good design but too heavy for a backpack.
Not if you build it with the alternative neo drivers and build the Halfinator version. Several people have done that with good result. For optimum comfort they typically use a divers harness. That ensures good mobility and you can distribute weight as it fits you.
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