Alfresco

Alfresco


Designer:
Kev

Project Category:
Portable Speakers

Project Level:
Intermediate

Project Time:
1-8 Hours

Project Cost:
$100 – $500

Project Description:
The Alfresco is a portable Bluetooth speaker.

Design Goals:
The goal was to design a portable Bluetooth speaker with a clean look, long battery life and be capable of playing at full volume with little distortion.

Driver Selection:
(2) Dayton Audio PS95-8 3-1/2″ Point Source Full Range Driver 8 Ohm

Enclosure Design:
The box is .18 Ft3 and has (1) 1.5” diameter, 4” long Port.

Enclosure Assembly:
Nothing fancy with the box. All pieces were glued and brad nailed. Threaded inserts were used on the back so it could be removed to swap parts out as needed.

The board is powered by a 12V 6800mah lithium Ion battery. They come is a small plastic box with an on/off switch. I removed the battery from the package to reduce the overall size and also repurposed the switch to turn the board on and off. The battery packs come with a wall charger so all that was needed was adding a 2.5mm panel mount jack on the back.

Crossover Design:
1 non-polarized electrolytic 330uF capacitor inline on each positive speaker terminal.

Conclusion:
Very pleased with the overall look and sound. Music is detailed with some warmth in the mid range. It does lack some low end but at full volume I can still listen to most songs without hitting the mechanical limits of these speakers.

About the Designer:
I have enjoyed wood working since I was a kid. Time to take it to the next level by integrating speakers and electronics.

Project Parts List:

Dayton Audio KAB-230 2x30W Class D Audio Amplifier Board with Bluetooth 4.0
Dayton Audio ND90-8 3-1/2″ Aluminum Cone Full-Range Driver 8 Ohm
330uF 100V Electrolytic Non-Polarized Crossover Capacitor
Speaker Cabinet Port Tube 1-1/2″ ID x 4″ L Flared
Penn-Elcom H1014K Extra Wide Strap Handle Black End Caps

7 Comments

Add yours
    • 2
      Kev

      I have bought about 4-5 Tallentcell batteries for portable speaker project. All with different mAh ratings. I personally have never had an issue with them. In fact, I made a portable speaker with (2) 4″ coaxial car speakers and a 4500mah battery for a friend about 5 years ago. He just told me the battery finally gave out. I am sure some of the reviews are legitimate but my expeirence has been good.

  1. 3
    JF

    Nice build! Would you mind sharing 2 tips?
    1. How did you calculate the right port size? I’m looking all over the net to try to figure out how to calculate this when you have 2 drivers (many good formulas with 1 driver but what about 2?).
    2. Why did you add capacitors?

  2. 4
    Kev

    1. Parts Express helped me with port size and length. Just gave them the drivers and box size. I have a Mac and haven’t found any software yet that I can run. My experience has been that if you can calculate 1 driver just double that. Example: single driver sealed box optimum volume .5ft3.. 2 drivers would be .10ft3.
    2. I initially used the capacitors as a high pass filter to help with when listening a high volumes. I have updated the original to run full range with -4db of baffle step compensation. Based on a 10″ baffle, that works out to be about a 1.5mh inductor (part# 257-052) and 4.7ohm resistor (part# 016-4.7). With these speakers and this size box the vocals / midrange was a little over powering. I like this setup much better, just wish I had purchased the functional cable package so I could run a 20-20K sweep with audio tools to get some real data..

    • 6
      JF

      Thanks again. If I use different formulas on the net I find an ideal enclosure around 0.5 ft3 (for 2 PS95 drivers). It’s almost twice your size. I am a newbie but maybe it’s the reason why the midrange was a little over powering?

  3. 7
    GKT

    I like the inner frame you did to hold the front and rear panel on. After two attempts having to back track to that conclusion I settled on that idea as well. Next box will have it in a cleaner way like yours. Good looking unit and color combo.

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