Well I would like to tell you about one of my old projects but I don't really know if it matters to you to put on the website. The project is an amplified speaker, good quality and very easy to do. The idea of my project goes to those music editors who need flat response speakers as monitors to their music edit. Since I'm one of those music editors composers and I need these speakers to monitor my work and do the tracks equalizing too so I thought about this project. I have submitted this from my DIY point of view since monitor speakers are very expensive and this only costs 100$ or maybe max up to 150$ depending on the amplifier used.
I bought a enclosure with ready assembled speakers in. It contains 15" full range and 1 quartz midrange and 2 quartz tweeters. I added one dynamic tweeter with a high midrange crossover. I added an amplifier to it on the back ( Car audio amplifier ). This amplifier delivers 75 + 75 watts so I bridged it to deliver 150 watts and for sure I installed a transformer inside it to power the amplifier.
The power supply is 4 X 12V 4 A transformers. The reason I kept the amplifiers switch mode power supply is to avoid the rumble hum from the power supply at high voltage and to assure regulated supply to the power amplifier stage. That's also easier since you don't need to open the amplifier and disconnect the switch mode power supply.
The transformers are so cheep and available in the market, they are made for 12 V Spot lights ( 55 Watts ) you can buy from any electrical supplier I got the 4 of them for 10$ then a 16 A diode and 10,000uF 25V capacitor, a total of 20$. The enclosure I got was only for 55$ with the speakers inside. I already had the amplifier in my car so I upgraded my car audio system and put this for this project.
I extended the tweeters main audio wire to be connected or disconnected to use this speaker as a guitar amplifier ( with a digital effect connected to the input ) as it delivers real guitar sound same sound professionals get on stage. Once I connect back the tweeters back it turns into a professional monitor speaker.
Unfortunately I don't have the equipment to measure the frequency response but practically I was able to hear sounds from the very low frequency up to the very high frequency too ! I used Sound Forge software with its wave form generator.