2 Way active powered loudspeaker inspired from studio monitors

[zeus_threat]

Hi everyone i'd like to detail a project that i've built here. It took me some great deal of time to put it all together, tune measure and get it to work since i have built it from scratch. Call it the zeus speaker if you want lol. It was inspired from studio monitors though my drivers are not studio grade but the performance is really good and sounds really musical for my taste

This is what it was built from:

1 X 1" Dome tweeter 8R

1X Audax 6" speaker 8R

1X LM3886 for the tweeter amp

1X Discrete amp tuned in simulation based on "Blameless Amp" for the woofer

1X PSU board with soft start + regulated +-15V output and +-35V output filtered by 4X4700uF for the amps

1X DC + relay based remote start up board

1X Speaker protection board for DC offset

1X speaker delay start based on an LM741 comparator

1X Crossover board containing: HP + LP linkwitz riley 4th 24dB/Octave, tweeter delay eq, woofer baffle step eq, LR Riley Eq to eq the woofer to ~45Hz and a Q of 0.8

All housed in a sealed + damped with cotton woll enclosure with bracing measuring h: 32.5 cm X W 20.5 cm X 32.5cm depth based on 1/4" MDF

All electronics housed in back of enclosure.

Drivers flush mounted to minimize diffaction.

I will post pictures of it i need to lift it off its stand and it weighs a ton.

Its controlled from a small buffer pre-amp \volume unit based on TL072CN Ic's with regulated LM337-317 supply with a small headphone amp and the DC to switch on the relay to power the speakers.

All pcb's were home designed and home made and all measurements (freq, woofer T/S, tuning e.t.c) wre made with speakerworkshop:http://www.audua.com/


Am planning to rebuild the pre-amp based on PGA2310 ic controlled by pic and LCD display + relay based input switching plus removed the huge EI transformer + the huge psu board and replace it with an SMPS that am trying to build here: http://www.diysmps.com/forums/showthread.php?158-Drive-signal-issues-with-half-bridge with the immense help of the great Microsim and others

 

[zeus_threat]

Here are some pics. It sounds better than it looks lol

The only things that would need improvement is the front face look and i know how to work around that and a better pot in the pre-amp than the one am using Alps are hard to find here.

I've got a sealed sub waiting electronics final assembly to accompany those units. It was a great and tedious experience learning active speakers and all the concepts but i would not change it for its performance and the channel seperation and soundstage is really great.

For future plan am planning to build an active floor stnading version with 4 speakers 2 mids and 1 tweeter in d'apollito arrangement each driver with its own amp with active cross overs and eq's e.t.c and if i get to build one well i'll replicate the same for others channels for a home theatre setup. Very very audacious project we'll see how it goes but right now these two speakers are more than enough to fill my room with music

 

[Speakers]

Very impressive, thanks for the post. I plan to undertake a similar project in the future.

 

[zeus_threat]

Hi thanks for the reply it needs good planning before you attempt. It took me a long time to experiment and fine tune. Am planning of making a d'apollito version using two woofers and a PGA2311 based pre-amp

 

[zeus_threat]

While being busy with my logic analyzer, I took a look around for a digital approach for signal processing for the active loudspeaker I wanted to rebuild. I have dismantled the unit above and have slowly started thinking of how to rebuild it but much cleaner and closer to a commercial form. I noticed the mini dsp which seemed very popular and ended up finding it was using an ADAU1701 codec DSP (2 analog in and 4 analog out) and a pic 18FK4X series for usb communication. There is also a recent article in elektor magazine about an ADAU1701 dsp board. the good thing about the ADAU1701 is that its available on ebay plus the software to build the FIR and biquads is free from Analog devices http://www.analog.com/en/dsp-software/ss_sigst_02/sw.html . I am waiting for the DSP ic to arrive and decide what to do next. It will need a prototype board build up, test , e.t.c. I also came across another interesting possibility which was that of using an STM32F4X series that has a floating point DSP unit, but the issue is that it has only 2 I2S ports. That would mean one per speaker. The STM32F10X series is also available and does DSP processing on CPU using the CMSIS math library. there are a lot of possibilities some heavy testing will be needed to decide on what to do next

 

[Speakers]

Funny you should say that! I've actually completed my project using that very DSP. The ADAU1701 is on a custom board with 2 stereo class-D amplifier ICs, total of 4 channels at 20-25 Wrms. The system is 2-way stereo; each driver powered by dedicated amplifier channel. The bass and midbass is handled by a 3-inch driver with modest excursion, and the mids and highs are crossed to a 2 inch driver.

This is the prototype. I built a second with added functionality and a nice finish but it's back at home and I don't have any pics.

 

[MicrosiM]

Funny you should say that! I've actually completed my project using that very DSP. The ADAU1701 is on a custom board with 2 stereo class-D amplifier ICs, total of 4 channels at 20-25 Wrms. The system is 2-way stereo; each driver powered by dedicated amplifier channel. The bass and midbass is handled by a 3-inch driver with modest excursion, and the mids and highs are crossed to a 2 inch driver.

This is the prototype. I built a second with added functionality and a nice finish but it's back at home and I don't have any pics.

View attachment 4519View attachment 4520View attachment 4521

Very nice built, I like it

 

[zeus_threat]

Hi great job. I got my ADAU1701 ic last week. Can you tell me if you purchased the board or you built it yourself? I am still thinking whether I have to decide on how I will drive the ADUA1701 with a microcontroller or through an eeprom. I see you have used an EEPROM in your circuit which is great since once the speaker is setup and calibrated there is no more need to touch it.

did you use sigma studio and a programmer for the EEPROM? thanks

 

[Speakers]

Thanks guys.

I built the boards myself. The layout was done using EAGLE and the PCBs were fabricated using Fusion PCB. I bought an evaluation board and programmer from Analog Devices which was used to program the eeprom directly from sigma studio.

The self-boot works flawlessly but on future revisions I intend to boot and control the DSP from a microcontroller for added functionality and cool-factor. Volume control is handled by the ADAU's auxiliary ADC and a potentiometer, and the second set I built has a button to adjust the amount of compression on the bass driver.

The board shown is missing a few components; most notably the DC-DC converter to power the logic. A single 65W, 24V brick-type power supply powers the whole system. The 2-inch drivers were about $9/piece and the 3-inch were about $12/piece when I bought them, but the supplier has since stopped carrying them. The amplifiers are TI TPA3123.

 

[zeus_threat]

Hi thanks for your reply. I am searching a little bit around to find the USBi device to purchase so that I can program the ADAU1701. As for the board I will build it myself based on the datasheet schematics. I am also looking for information on how mini DSP uses the pic18Fxx series to program the device through USB which is really scarce. If you are looking for an online supplier for the drives you can try parts express. Otherwise if you want to go with even higher quality speakers there is madisound. both ship worldwide.