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Unnamed Design by Lutkeveld (Development Thread)

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lutkeveld View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lutkeveld Quote  Post ReplyReply Direct Link To This Post Topic: Unnamed Design by Lutkeveld (Development Thread)
    Posted: 29 May 2016 at 9:55pm
Welcome

This will be the thread where I dump my progress on my, yet unnamed, project. It is somewhat similar to the Boominator MICRO, but different in a lot of ways. The main point of this thread is to give people some insight in the design workflow, as well as giving input and asking questions. The goal is to make the design fully open-source. 

Every step will have instructions with pictures and explanation. Along the way I will post some YouTube videos and Instructables on certain steps to provide a little more knowledge than just the information needed. It’s great to see more people get into DIY audio, so I hope this design will help many people get started.

Most of the design is already complete, so this thread is partly a backlog of updates. However, the devil is in details, and there’s still a lot of choices to be made. Feel free to suggest/correct/add things.

First step will be driver selection

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Post Options Post Options   Thanks (0) Thanks(0)   Quote lutkeveld Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2016 at 10:07pm
Driver choice

Selecting the woofer is the most difficult task, so that’s the first choice. Tweeter choice will depend on which woofer is selected. Parts Express has a great selection and can thus be used as a tool for driver selection.

Since I am aiming for a small enclosure (<10 liters) I’d rather go sealed. Decent bass extension is wanted and the driver needs to preferably be light weight and low cost. This leaves me with the following requirements:

- Medium Vas (3-10L)

- Medium Fs (<65Hz)

- High Qts (>0,45)

- Low weight magnet, preferably neodymium (<500gr)

- Low price (<50$)

- 4 ohm impedance 

A quick search returns the Dayton ND140-4.

Great fit, especially considering the low price of 31 dollars. Sensitivity isn’t too high at 88.4dB @2.83V/1M. I have chosen to exchange some loudness for bass extension, with the reasonably powerful amplifier it will get loud enough either way.


 


As you can see in the frequency response graph the response starts to get nasty around 4kHz, probably due to the aluminum cone breaking up. This means filtering has to take place at 3kHz or below. This will be an important parameter when selecting the tweeter.




The tweeter should be:

-     - Low cost (<20$)

-     - High dispersion

-     - Easy to mount

The last requirement already disqualifies anything that has to be flush-mounted since I will be laser cutting the enclosure.

The Dayton ND20FB seems to offer what I’m looking for. It flush-mounts from the back in a 12mm baffle. My baffle will be double 6mm, so that would work.




The resonance frequency is a bit on the high side, but the tweeter won’t see more than a couple of watts and will be actively filtered with a >2nd order filter. I don’t foresee much trouble there.

DaytonAudio is really great in providing the files needed for simulation (FRD, ZMA, TSP). Here are the links to the ZIP folders for both drivers:

ND140

ND20FB

It’s always best to measure them yourself, which I’ll be doing in another post, but this is a great starting point.

Next stop will probably be the amplifier :) 



Edited by lutkeveld - 29 May 2016 at 10:09pm
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Ganon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ganon Quote  Post ReplyReply Direct Link To This Post Posted: 03 June 2016 at 10:46am
Remember when you calgulate your spl with 2.83v at 4 ohm, it's the same as 2Watt/1meter, not 1 watt.
So the spl is more like 85,4db 1W/1M :)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cookie-dj Quote  Post ReplyReply Direct Link To This Post Posted: 03 June 2016 at 4:44pm
Have you simmed any mainstream drivers for this project? (e.g eminence, p audio, rcf etc).....
You can't polish a turd!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote chemacky Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2016 at 3:07am
Subscribed. Can't wait to see it unfold, keep up the good work.

Some teaser pics of what you're brewing up would be great!

Cheers, and good luck!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote lutkeveld Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2016 at 4:30pm
I know, thanks for the headsup Ganon :) 

Cookie-dj, I have looked at a lot of drivers but the ND140 is the only driver that has the T/S parameters I want and doesn't cost that much. There were some more expensive woofers that would work, but the ND140 is the best fit for my project.

Chemacky, a small teaser:


Oh, and I just posted an Instructable on my amplifier design:





Next step will probably be on the rendering and lasercutting (fusion360). 



Edited by lutkeveld - 06 June 2016 at 7:38pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DJ-Dulux Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2016 at 7:06pm
This could be interesting, subscribed. Looks smart and commercial....

Dupe...
Dupe...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cookie-dj Quote  Post ReplyReply Direct Link To This Post Posted: 07 June 2016 at 6:38am
What were the more expensive drivers? Looks really promising Thumbs Up
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Post Options Post Options   Thanks (0) Thanks(0)   Quote chemacky Quote  Post ReplyReply Direct Link To This Post Posted: 03 November 2016 at 10:46pm
Just a little nudge to see how this is shaping up. Haven't heard anything in quite a while. :)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote davey t Quote  Post ReplyReply Direct Link To This Post Posted: 05 December 2016 at 4:17pm
Your output filter looks a bit suspect. If you are just making this for your own use and cables are short then just get rid of all the output filtering - it will extend your battery life a lot. 

You'll need to add an electronic bass boost to extend the low end of that sealed enclosure. What is your signal source, power supply, crossover etc? 

David
Minirig portable soundsystem movement
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 05 December 2016 at 9:12pm
Is htis gonna be battery powered ? Aimed at indoor or outdoor use ?

If battery power, I'd suggest removable battery compartment (a la soundboks) - opens options for the user to get extra battery life (by buying extra packs) and also possibly to choose mebbe 6S LiPo for full beans volume (would need good heatsink I guess - mebbe even forced cooling) or similar physical size 4S pack for ~double the runtime .... any auxiliary circuitry would need to tolerate ~15-30V supply I suppose.

Also, personally I favour the "ghettoblaster" form factor with a carry handle  ..... just the job for this size/weight - and lends itself quite nicely to carrying (and playing) on the back of a bike, for example.
REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
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Post Options Post Options   Thanks (0) Thanks(0)   Quote barrymossel Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2017 at 10:38am
Any news on this lutkeveld?
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