Help in building tiny inexpensive full range computer speaker please?

I’m new to speaker building and wish to make a pair of very inexpensive and very small computer speakers. I’d like to keep it simple with a single full range driver, probably 2 – 3 inches diameter. Cabinet size: as small as possible, preferably no bigger than 6 x 5 x 7 inches or 2 liters volume. Cost: something like $75 max. None of that is carved in stone, of course, except that I don’t want a subwoofer.

I realize that it won’t be true audiophile but, as a first build, maybe a good place to start. As I look at articles and read specs and blogs I’m getting more confused rather than less. Can someone help me sort this out?

After looking at many speaker specs, especially wanting smooth frequency response with some low frequency extension, I was thinking about the 3 inch Aurasound NS3-193. I was also thinking about the Tang Band W2-1803S 2 inch and the Fountek FE85 3 inch. The Aurasound NS3 with a Peerless 3.5 inch passive radiator looks promising in a 2 liter enclosure.

This is where the endless questions start to pop up. I’m using Jeff Bagby’s woofer box calculator and I’m not sure if how to optimize it.
The calculator shows a big “hump” in SPL in the low frequencies – do I need to address that?
Do I need a high pass filter?
Are there similar tiny cabinet dimensions that would be better?
How do I decide on the target Fb?
Would a larger passive radiator work better?

I was hoping to put the amplifier board inside of the cabinet, too. I have a TPA3116D2 board with 50 watts/channel. That may be one wish too many.

Any help would be much appreciated! :lickface:
 
Around here there are a lot of uFonkenWK. They are 2 litres and the plans can be found here: Frugal-phile | Box Library / Fostex. It will (slightly) exceed your budget but they are really quite good. Their are also some slightly larger ones (all part of the paid plan-set).

Here a set of the earlier uFonken for the FF85k (differs only in the width of the vent spacer)

239019d1315420505-minionken-fonken-picture-gallery-ufonken-macassarebony.jpg


For a 3" the little Aura is one of the most extended on the bottom… 2 litres is really too small to get a decent 2 litre reflex. Sealed they have a slight, but acceptable, bump and an F10 below 60 Hz. This is how we used ours. It is more coloured and isn't capable of the same level of detail as the FF85wk but costs about half.

FE83 also doesn't at all like a reflex that small, sealed F10 just over 80 Hz. Here are 5 enclosures we did for the FR88ex which work OK for the FE83. http://www.diyaudio.com/forums/full-range/210106-fountek-five-fr88ex.html

Plenty of options, i'm sure others will chime in.

dave
 
For a compact speaker circa 2L you need a driver with certain TS parameters that will allow a lower tuning in a smaller box. Forget about large Vas high Qts drivers unless you want to go sealed and have bass starting to falloff starting 200Hz.

Look at Faital Pro 3FE22 8ohms. It is 91dB sensitive and has ability to produce some bass in a very tiny bass reflex. Here is a quick and dirty prototype I made out of foam core at 1.5liters. With a small 25mm vent and a 1mH and 6.8R BSC the sound is quite nice and balanced with about 80Hz F3.

Here it is being powered by a 1.6w class A headphone amp. It is plenty loud for a desktop speaker.

540170d1459087868-jlh-class-headphone-amp-ebay-setting-bias-output-help-needed-jlh-headamp-01.png
 
Dayton ND65-4?

Could try a BR or a TL to get decent response to 60hz or so. I've run a sim in the TL software based on the Woden Redeye. With 40-20-10cm2 in a 3x27cm length gets response to 60hz or so.

Simpler than that, a WinISD sim predicts tuning of 60hz in a 1.75L box.

If it wasn't for computer speakers you wouldn't do it though. Power handling is "low" before risking overexcursion. Though with a computer, you can play with DSP to implement a subsonic filter.
 
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Thanks for the advice. May i have more? lol

Thanks guys for the great info! I’ve been poring through it all day.

I see myself building 2 sets (or more) of computer speakers in the near future. A less expensive (and smaller) pair for at work and a better (probably larger and more expensive) pair for home.

Planet10, can you describe the coloring of sound in the Aura NS3 sealed? 2 liters? Tolerable?

I really like the look of the Martello (with the Fountek FR88EX) and the uFonken (with the Fostex FF85K).
I take it from your comments that a less expensive driver like the Fountek FE85 likely wouldn’t compare to the more expensive drivers?
Is it possible to scale down the size slightly?
Would substituting the Fountek FE85 be worth considering?

Sayrum, I love the look of the Vildeapel but my german sucks. Can you give me any more info on it?

XRK971, thanks for doing a mock up. I hate to be dumb but when you say “a small 25mm vent and a 1mH and 6.8R BSC the sound is quite nice and balanced with about 80Hz F3” what do you mean? I don’t understand the terminology mH and R BSC.

Jerms, sorry but I’m a newb: what do you mean by “40-20-10cm2 in a 3x27cm length gets response to 60hz or so”?

Do all of these require high pass filters? Can any of these go without electronics?

Current prices in US:
Fostex FF85WK $ 43.55
Fountek FR88EX $ 37.80
FaitalPRO 3FE22 $ 32.00
Aurasound NS3-193 $ 19.90
Dayton ND-65-4 $ 19.30
Fountek FE85 $ 11.20
 
Baffle step correction circuit. Take a 1milliHenry inductor and parallel it with a 6.8ohm or 5ohm resistor (adjust to taste) and take that unit (called a BSC circuit) and put it between the amp and the +terminal of the driver. It basically provides a slight attenuation of the high frequencies above 900Hz that will level match the bass and the treble for a balanced sound. Without it, the speaker will sound shrill. The term baffle step refers to the loss of bass below the frequency dictated by the baffle width. An infinite baffle (a wall) had no baffle step loss. You should read up on BSC.
 
What about the Monacor SPX-31M?

You can get a pair of these for less than $40. I was recently mucking around with them in WINisd for a project similar to yours :) .

Attached, along with the datasheet, is an LF plot for a 3.2l enclosure tuned to 93Hz. Group delay is less than 10ms peak at about 80Hz.

I'm thinking about writing this up as an article, it would make a good first speaker project for someone.
 

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Redeye = last one - Size is a bit bigger than you specified. I reckon somewhere 4.5-5.5 litres, 12"x5"x9".
http://wodendesign.com/downloads/Woden-BabyLabs-081015.pdf

The cross section of the speaker reduces as it approaches the end/exit/port. On the Redeye, the depth reduces from 4" to 2" to 1" or 10->5->2.5cm. The length of each section is around 30cm (12").

On my (imagined) speaker with the ND65-4, the area reduces from 40->20->10 cm2.... Exact dimensions to be determined.... Length of each section is 27cm.

The easier box to build would be the ported or bass reflex enclosure. WinISD modelsthe ND65in a 1.75L box and tunes the port to 59-60hz. Some freedom of design in the BR. Angle the face up off the desk? Which face to exit the port? Might suggest bottom port plus desk stand-offs if there's no back wall.... Or front port.
 
Can we go even smaller?

Xrk971: It sounds like I definitely need a baffle step correction circuit. I do want to have the correction within the speaker because I want the flexibility of moving to a different system without having to adjust the source.

S4M: Which mini Frugal are you referring to that works well with the Aura NS3?

Monty78pig: I don’t see any suppliers for the Monacor selling to the US.

Jerms: Any idea how the ND65-4 would sound in a 1.75 liter box tuned to 60Hz?

Planet10: Can you describe the coloring of sound in your sealed Aura NS3? What size cabinet? Was it tolerable for listening?

I lean toward the smaller uFonken (Fostex FF85K).
Is it possible to scale down the size slightly? (are we at the limits of physics? Lol)
Does anyone know if other drivers have been tried in this cabinet?
Is it even worth considering a less expensive driver like the Fountek FE85?

Is the baffle step correction circuit the only electronics needed within the cabinet?

Has anyone done tiny speakers with passive radiators? I can’t seem to be able to do the calculations to see if it's a viable alternative.

Would I ruin the sound if I put the amplifier board inside?

What would you guys recommend for sound damping? ½ inch wool felt only?
 
Planet10: Can you describe the coloring of sound in your sealed Aura NS3?

Not without listening to them again.

What size cabinet? Was it tolerable for listening?

A little less than 1.5 litre sealed. They are fine.

I lean toward the smaller uFonken (Fostex FF85WK).
Is it possible to scale down the size slightly?

I have a drawing for an experimental 1.5 litre box with 9mm multiply, done expressly for smallness. 133x212x107mm. If you want to try, email me.

dave
 
I bought a pair of these https://www.madisoundspeakerstore.com/approx-4-fullrange/markaudio-chn-70-paper-cone-full-range/ and put them in a box suggested on the same page: a ported box of 0.2 cubic feet with a 1.5" diameter vent by 4" long (or 1" Ø x 1.5" long), your f3 is about 70Hz.
I haven't run any measurements, but to my ears, they are great computer speakers. A small Lepai 2020 or similar will do very well with them.
These are an inexpensive and fairly simple build. Mark Audio drivers are designed to need no BSC or any other filter. All the Mark Audio drivers are great as well.
There are tons of designs from which to choose, so you just need to pick one that's a proven design and go with it. I'd start with simple and relatively inexpensive. You can still get some great speakers, in spite of low price and simplicity.
If you get overwhelmed with all the advice and suggestions, I'd recommend messaging one of the members or member-designers and pick his brain. You've come to the right place for some great DIY speakers.
Mike