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Old 18th February 2008, 03:45 PM   #1
Chooban is offline Chooban  United Kingdom
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Default My 1st Project - Need your expert help!

Hello.
theres a lot of writing to follow, please bear with me!

I'm currently a Design and Technology student in the UK and for the final years project i decided to enter the world of DIY audio and design and manufacture an iPod speaker dock with the following qualifications under my belt:

* I have NO experience WHATSOEVER in the field
* I have VERY LITTLE knowledge about electronics

dont let that put you off this thread yet though, I am a very qualified and dedicated technology student! My work has been on exhibition in London due to me being one of the top technology students in the UK.
I knew this project would be quite a challenge.

i'll save you my experiences of the first 4 months of development into the project but it did require a LOT of research. most of which came from lurking a lot in these very forums

Here's the final design:
Click the image to open in full size.

2 x Fostex FE127E Full range drivers
2 x Fostex FT17H Tweeters
SI T-Amp - i gutted out the innards and wanged it in mine
30W power supply
2 x Crossover 2-Way 8 Ohm 5,000 Hz 100W
Alps potentiometer
custom made aluminium volume knob
iPod connectivity - charges ipod even when amplifier is turned off (there will also be an attachment for any device with a stereo jack)
LED lighting strip

the thing was designed to be a living room center piece. The alien-like styling was inspired by the Ghost from video game Halo

the inside looks a bit like this:


Click the image to open in full size.

current stage:


Click the image to open in full size.

manufacturing had to done using a laser cutter - 6mm at a time.
you can probably see all the layers stuck together.

theres also a video here http://youtube.com/watch?v=hzNUQpcgEn4&feature=related
and here http://youtube.com/watch?v=nncLSPcbH3g&feature=related

Im not sure what else I can tell you.
This is my first project - i was wondering if you could give some feedback to the design.
any sort of views would be appreciated, this thing will be marked along with the coursework and development and so any comments i will take a note of.
if theres any questions, ill try and answer them the best i can as well
thank you for your time

Chooban
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Old 18th February 2008, 03:57 PM   #2
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Hi Chooban,

Nice looking project you have there. I am curious about your box design and how you are making use of a dual chamber set up. I don't mean the separate box for either channel, I mean the compression chamber dumping into the other, (is that a bandpass?) How did you design the ports that lead into the secondary chamber? I was also wondering about the lack of an extension to the port at the exit from the second chamber. Is that correct? A true bass reflex?

You may be able to reduce your XO to a small cap on the tweeter and letting the 127's run full.

Having the tweeters out front of the FR's will throw off the time alligment a bit.
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Old 18th February 2008, 04:03 PM   #3
badman is offline badman  United States
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Default A VERY small cap

Given the high efficiency of the tweeter, and the lack of bafflestep already, make sure you roll them in, say, at 40k. A smaller, less efficient tweeter would have probably been my choice, something like the Dayton 5/8" dome would have been well-suited in terms of efficiency, necessary bandwidth, and price.

But I do like that FT17H, and this being a design project, they do look awfully cool

Nice work mate! For the utmost sound quality, you'd want to do some things different, but too late now, you've spent the scratch on the boxes, and I'm sure they'll work out fine for you.
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Old 18th February 2008, 04:03 PM   #4
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OK, so I should have watched the videos first. I see the ports now. Are they the same length?

Have you had to pad the tweeter much?
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Old 18th February 2008, 08:33 PM   #5
Chooban is offline Chooban  United Kingdom
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Default Re: A VERY small cap

Quote:
Originally posted by Cal Weldon
Hi Chooban,

I am curious about your box design and how you are making use of a dual chamber set up. I don't mean the separate box for either channel, I mean the compression chamber dumping into the other, (is that a bandpass?) How did you design the ports that lead into the secondary chamber? I was also wondering about the lack of an extension to the port at the exit from the second chamber. Is that correct? A true bass reflex?

You may be able to reduce your XO to a small cap on the tweeter and letting the 127's run full.

Having the tweeters out front of the FR's will throw off the time alligment a bit.
I wasnt entirely sure if the dual chamber set up would be effective or not.
the first chamber is quite small and having a port on it would destroy the look.

air from the first chamber goes into the second chamber which feeds to the port.
there is a tube there but it was too long, so i had to saw it in half! i think this ruins the tuning of the tube.

Quote:
Originally posted by badman
Given the high efficiency of the tweeter, and the lack of bafflestep already, make sure you roll them in, say, at 40k. A smaller, less efficient tweeter would have probably been my choice, something like the Dayton 5/8" dome would have been well-suited in terms of efficiency, necessary bandwidth, and price.

But I do like that FT17H, and this being a design project, they do look awfully cool

Nice work mate! For the utmost sound quality, you'd want to do some things different, but too late now, you've spent the scratch on the boxes, and I'm sure they'll work out fine for you.
im terribly sorry, but i dont know what 40k is
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Old 18th February 2008, 11:48 PM   #6
adason is offline adason  United States
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Hi Chooban,

I have not read all the posts, plus it may be too late now, but looking at the first picture you have tweeters in the middle right next to each other. That is not the proper way to place them if the speakers are together. It will have virtualy no stereo separation. You should place tweeters, which cary the stereo information, as far from each other as possible, not next to each other in the middle.
Kind of like old fashioned boomboxes had. Remember?

adason
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Old 18th February 2008, 11:59 PM   #7
ronc is offline ronc  United States
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I never want to hear that my designs are weird looking again.

ron
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Old 22nd February 2008, 02:47 PM   #8
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40K = 40,000 Hz.

The suggestion was made as the tweeter is quite strong and may overpower the woofer hence my question about padding (reduction in tweeter volume to match the woofer)
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Old 23rd February 2008, 08:56 PM   #9
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Quote:
Originally posted by ronc
I never want to hear that my designs are weird looking again.

ron

I think the Dallas III is the coolest BLH I've seen yet!
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Old 24th April 2008, 07:19 PM   #10
Chooban is offline Chooban  United Kingdom
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thought i'd post the final thing :-)
please let me know what you guys think


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