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:
|
Part # |
Description |
Qty |
|
325-102 |
Dayton Audio KAB-230 2x30W Class D Audio Amplifier Board with Bluetooth 4.0 |
1 |
|
290-210 |
Dayton Audio ND90-8 3-1/2″ Aluminum Cone Full-Range Driver 8 Ohm |
2 |
|
027-374 |
330uF 100V Electrolytic Non-Polarized Crossover Capacitor |
1 |
|
260-402 |
Speaker Cabinet Port Tube 1-1/2″ ID x 4″ L Flared |
1 |
|
262-314 |
Penn-Elcom H1014K Extra Wide Strap Handle Black End Caps |
1 |
Do you mind sharing which battery you used? I am finding few with enough positive reviews to be confidence inspiring.
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.
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?
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..
Many thanks! Really appreciated!
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?
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.
Nice! any problem powering that with the 12V LiOn? I would like to use the 2x15W version of this amp for a similar build, but was concerned with power from the 12V battery.
I have not had an issue with any of the batteries in the 6000 – 70000 mah range. Specifically with this unit under normal conditions I charge it maybe once every 3-4 weeks. I used it for an outdoor party at high volume as well for 12 plus hours. My opinion is for a 2×15 watt amplifier 6000-6500 mah is more than enough. They do offer larger capacity batteries though..