TOPIC:

This pic is similar to one I took earlier, but here the system is up and sounding good! The minidsp is wonderful to work with. I set it up with a WAG crossover to listen. I then took some measurements, and was puzzled for awhile. I hadn't checked the stock settings in the first stage PEQ, and of course, that filter was causing some unexpected results! With that figured out, I was able to try several different slopes and crossover points.

Right now, I've settled on a Butterworth at 100hz. In combination with some natural rise due to the woofer placement, I'm getting a pretty smooth transition somewhere between 100 and 200hz. I can still do considerable tweaking, and certainly I'll add a couple of EQ notches for room modes. The OB woofers need less of that than a box speaker, as they interact with the room so much less.

This project really benefited from the flexibility of the miniDSP. If I were using a passive crossover, I would have started with something completely different. It would have taken hours (days) of time to get to where I am now after mere minutes. Of course, computer measurements also greatly speed the process. I am using room EQ, but I also plan to double check with HOLM impulse.

Paul

Here you can see the minidsp in action. Obviously this is not the final component layout! To recap, the gray Akai chassis contains a preamp and amp. That amp has a passive crossover (165hz line level, I may add caps at speaker level too) and drives the fullrangers (Wild Burro Audio Betsys). The preamp also drives a chip buffer, which in turn drives the miniDSP. The miniDSP is connected to the big (7 watts, 40 lbs) push pull amp that drives the woofers (nice surplus 15" Fosters from Jack Hidley).

I've already extolled the ease of setting this system up with the miniDSP. But, it also sounds great! I don't have much experience with dipole woofers, but the quality of bass is incredible. Open, well defined, and much deeper than I expected. Finally: the miniDSP is inexpensive! There are a few really cheap options (car audio active crossovers? surplus plate amps?), but they are neither flexible nor transparent. Nice PA crossovers are expensive and large. And passive components would not only be horribly time consuming to dial in, but cost an arm and a leg!

So, the miniDSP is winning on all counts. If only my tube amps would come in under budget and set up in minutes. . .

Paul
www.wildburroaudio.com

This is real DIY, and I love it You seem to get the most out of what you have on hand.

My next project will also be OB, and it will be my first experiment with this concept.

I also use HOLM impulse. To you who don't now this software. It's free, userfriendly and developed by pro's.

I honestly had a great time reading how your project got together and the creativity that went through it Paul... Great stuff! Makes me envious of that Akai enclosure for our kit at the office.. A real "old school" look that is worth a 1000 shiny/Mac looking boxes!

Once again, thanks for your time on explaining your project. It's always valuable to us and all other miniDSP community members to see how these kits are being used... Neat!

Tony

Kjeldsen wrote:

This is real DIY, and I love it You seem to get the most out of what you have on hand.

My next project will also be OB, and it will be my first experiment with this concept.

I enjoy DIY in large part for the intellectual challenge. My first build were with brand new expensive parts. But that was easy. I think scrounging for parts and making due with what you have provides a much greater design workout. I also enjoy building unique things. If you have weird parts, it is tough for anyone to do something similar. (Though difficult to duplicate projects don't sell speakers!) Finally, I have reservations about our consumerist culture. I hate seeing good stuff thrown away. But, I also don't like the idea of using something just because it is old. I like to take the best of the old and combine it with the best new ideas. Tubes (in my case a combination of used tubes and the best of new production) with solid state loads and/or LED bias exemplify this. Old iron, yes. Old circuits, no.

There is something about OB's. I'm listening to mine and soon I'll be putting together my thoughts. Let me say this: they are worth the hassle. They have their downsides, but getting the box out of the way does something special. OB bass is always a challenge. Often it takes careful thought and simulation. The miniDSP's flexibility is perfectly suited to the challenge!

Paul

admin wrote:

IMakes me envious of that Akai enclosure for our kit at the office.. A real "old school" look that is worth a 1000 shiny/Mac looking boxes!

Once again, thanks for your time on explaining your project. It's always valuable to us and all other miniDSP community members to see how these kits are being used... Neat!

Tony

Tony,

To my surprise, my wife actually likes the old Akai chassis! I think they are neat too. I don't do good chassis work, and it frustrates me when my projects don't have some aesthetic appeal (though my sense of appeal is different from others). This was my first attempt at reusing a chassis (I've certainly scavenged parts and tossed many in the recycle pile). I thought it would save tons of time. Granted, I don't have a big desoldering station, but it took me four hours to strip the chassis. I probably could have built something that quickly!

These old Akais (aka Roberts) units are great platforms. The choke filtered dual mono supplies are a big plus. If I didn't need the preamp (if I could change one thing about the miniDSP, I'd want a much higher output impedance), I would have put in a phono stage. Or, with a wimpier preamp than the 12B4, I could have kept the tube rectification. These units are pretty cheap. I frequently see them for $50-100. Do watch the current draw on the PT, and don't expect subterranean bass from the OPT's. For those less adventurous, they also sound alright stock. I recapped mine and listened to it before I tore it down. Plenty of folks love them as is, but I'm a little pickier.

In any case, this system seems like a keeper. As such, I hope to put together some concise, clear documentation of the project. I have many irons in the fire, but it is certainly on my list.

thanks for your kind words,

Paul
www.wildburroaudio.com

Very interesting Wataagrilia, but what exactly are you trying to tell us? Please try it in english.

best regards ctm57555

Hi,

I have a message for the webmaster/admin here at wildburroaudio.com.

Can I use part of the information from this blog post above if I give a backlink back to your website?

Thanks,
Peter

Absolutely!

Paul
www.wildburroaudio.com