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Old 15th March 2011, 01:08 AM   #1
polop1 is offline polop1  United Kingdom
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Join Date: Apr 2010
Default lightest possible tripath type system.

Hello there,
I have had a recent success with some tripath amped ikea bowls, and with some past boombox projects. But the inevitable next step is to combine the pros into a light HiFi(ish) portable speaker system.

the inspiration for this next system comes from the power source
HobbyKing Online R/C Hobby Store : B-Grade 5000mAh 3S 20C Lipoly Battery

along with the high efficiency tripath amp, i think a total weight of around 1kg is possible with 20 hours battery life.

The purpose of this system is to chill to some music in tents at this summers festivals so weight and portability is important.

as for the speakers I am looking at some fold-able designs incorporating a 4inch full-range, bass reflex would be good as in a field I will not have EQ to help the sound thicken like I do with my ikea bowls.

so what I propose to the community is:
How should I go about folding designs?
-open baffle (enough bass?)
-telescoping bass reflex or sealed. (construction with pvc perhaps)

which drivers should I consider ?
-price should be low (as likelyhood of damage is high)
-should deliver some bass in the 50-100hz range to thicken the sound.
-weight should also b a consideration.
-I live in the UK therefore I am buggered if any components are needed from the US

any response is appreciated - even if it just to express frustration at the unoriginality of the questions(I have searched).
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Old 15th March 2011, 07:18 PM   #2
SAC is offline SAC  United Kingdom
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Join Date: Feb 2007
Location: London
Like this perhaps;
41Hz Audio - My new gem

You are after a "boombox" of sorts I think. Try searching this forum for advice such as that in this thread below;
First Boombox project, need advices!!
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Old 18th March 2011, 01:38 AM   #3
polop1 is offline polop1  United Kingdom
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Join Date: Apr 2010
hello there thanks for the reply - the links where very informative. I was wondering what the community would think of a folding open baffle design - is there any advantages to having a longer section behind the cone (using open baffle as a normal box but without a back). or would the added length and hence "enclosed" volume not make a noticeable difference in the outdoors. after all I am looking for a very compact design - whilst keeping all the sound quality I can.
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Old 18th March 2011, 04:10 AM   #4
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I would just suggest that if you decide to take the plunge to some kind of folding open baffle, take a look at a much larger diameter (main) driver, like a 12", since you really don't have the usually entailed enclosure penalty. The dimensions for decent bass in an open baffle are driver diameter independent, meaning you'd need the same baffle for your 4" even if it had the bass capacity of a 12, which it wouldn't. Also in your favor is the diminished magnet requirement for OB. You might want something like an Eminence Alpha 12LTA with a neodymium magnet, which is a non-existent driver, but that would be the plan as I'd figure it.
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Old 19th March 2011, 03:16 PM   #5
polop1 is offline polop1  United Kingdom
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hello there thank you for your reply, but i think 12" is too big, im looking for a more "ipod" speaker dock size, but ot optimise the bass rather than have masses of it - i know true bass wont be there, but i have heard incredibly small speakers sound good - and i would like to emulate.
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Old 19th March 2011, 03:57 PM   #6
SAC is offline SAC  United Kingdom
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Location: London
4" driver + necessarily large unfolding baffle + decent bass. Will the whole thing folded up not be bigger than a 12" in a dedicated box anyway?

Make a good size speaker box, put a lid and carrying strap on it, store your festival sun hat and umbrella in it
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Old 19th March 2011, 08:00 PM   #7
polop1 is offline polop1  United Kingdom
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Join Date: Apr 2010
I think that a 12" in a box wont even fit in my bag lol. 12" cone plus MDF box and the power system isn't going to be light. I get the train to festivals in the summer carrying all of the food for the weekend (i am a cheap skate lol) and a tent and things on my bac/ dragging it behind me. Last year I took some knocked together 4inch car speakers in an MDF box with 2 reasonable sized SLA batteries and they did the job. Though this year I am going for a sleeker method. same drivers (they are half decent car drivers) with amp6 (rather than cheap china ebay amp) and LiPo battery.

The size when stowed hopefully can be around 30*20*15 cm, with "internal" battery, amp etc. This is the target.
when unfolded each cab will be about 15*20*25cm and would not have a back side.

I am looking for suggestions to optimise this design and things I should consider when designing them, for example:
-is it completely necessary to separate the 2 cabs from each other or can i have one large void behind the speaker?
-would it be better to have a larger and thinner box (or even a flat baffle) or a longer thinner one?
-will I need to have restricted input caps to my amplifier to remove the lower frequencies?
-will the design be an improvement on a skin tight MDF box around the same drivers? (I have read that car drivers do well open baffle as they have stiff suspension and reasonable power handling)?

I know the answer to these questions from a HiFi perspective, but that is not what I am aiming for, outside does not do HiFi in the same way that this site does.

I am not interested in doing a large driver design, I have a set of portable enough 6 1/2 " component based speakers - but being heavy and power hungry does not suit my needs.

I would really appreciate your help, but we need to consider the drivers as a made decision (as I own them already) though I could be convinced to buy other small drivers.

edit: also I may have mislead you when I said 50-100hz bass, I meant around 100hz (50hz is very low lol) I would be satisfied with a hump in the response giving an impression or thickness. But I want it to sound considerably and very noticeably better than the normal cheap iPod docks you see around festivals and the like.

Last edited by polop1; 19th March 2011 at 08:11 PM.
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Old 21st March 2011, 09:21 AM   #8
polop1 is offline polop1  United Kingdom
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Join Date: Apr 2010
I have been looking around and saw the Monacor SP-60 s on another thread. cab volume of 4 litres they look good - though i would need a back for the enclosure, what would the recommendation be for the helper tweeter ? the Monacor SP-60 seems to be available in both 4 ohms and 8 ohms. total impedance for the amp should be 4 ohms yes, so 4 ohms with piezo in parallel with series capacitor. with this the impedance should be 4 ohms at the majority of frequencies?
This may be more appropriate in the multi way forum, but we'll see
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Old 21st March 2011, 03:22 PM   #9
Tom V is offline Tom V  United States
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Since your design goal is "light" I wouldn't go with MDF but rather high quality plywood (9mm?). In the U.S. the home supply stores sell "handy panels", 2' x 4' sheets of plywood (61mm x 122mm). Maybe something similar is available in Europe.

The 61mm can set the width of the unit, and then four slices for the top, bottom, front and back, so maybe 25mm tall and 20mm deep. Enough would be left for ends and internal bracing.

>is it completely necessary to separate the 2 cabs from each other or can i have one large void behind the speaker?

I asked this question a year ago, and the answer is separate. And bipole speakers require twice the volume of the single driver version to get the same bass performance, so no help there anyway.

-Tom-
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Old 21st March 2011, 11:25 PM   #10
polop1 is offline polop1  United Kingdom
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If i were to do the sealed 4 inch cone, what type of tweeter would be needed, as far as i am aware the sp60s go pretty high and willl only need a helper tweeter of sorts in the 6-18k range. will just using very cheap ebay tweeters suffice ?
such as 2.25inch 20W Square Dome Hi Fi Tweeter on eBay (end time 03-Apr-11 22:44:25 BST)
this is just an idea of the type, an example of a nothing fancy thing.
any reccomendations on some very cheap tweeters to match the manacor woofers?
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