MiniDSP + 3-way Paper Cone RS Speakers = Awesome

[Squidspeak]

Yes I have decided on exact design and size. It will have a solid Corian baffle top and bottom with veneered sides. Not sure which veneer but something exotic
like Rosewood or Koa with solid wood banding as an accent. X-over will be passive and done with a little help from my friends.

[danmarx]

Thanks Sydney for the link. I hadn't considered the idea of adjusting phase response in the same manner as adjusting frequency response. Pretty wild stuff. While I haven't had a chance to try it out, I was able to get some regular FR and phase plots of my most current miniDSP settings. I am going to leave these settings for now while I just listen and see how they sound. This is a pretty vanilla crossover with just some mild PEQ settings for each driver just to achieve maximum flatness. I used the target crossover option in REW and let it do the rest. I loaded the calculated filter settings and retested and voila, measured response matches the predicted! All plots are shown with 1/6 smoothing on. Measurements were taken at 12" from the center of the upper cabinet approximately 36" from the floor in the listening room.

miniDSP settings are as follows:

• RS225P Lowpass at 200 Hz, 24 dB LR, 0.0 dB gain
• RS180P Bandpass at 200 and 2,000 Hz, 24 dB LR, -6.0 dB gain
• RS28F Highpass at 2,000 Hz, 24 dB LR, - 6.0 dB gain, and 0.08 msec delay

The plots are titled what each measurement is. Basically I did the tweeter, the mid, the mid+tweeter, the woofers, the woofers + mid and then the entire speaker. Phase and FR shown for each one. So I didn't do any tuning for phase, just FR. The phase plots don't look completely out of wack, everything in-band looks normal I think. I also did a bunch of measurements with Bessel filters and the only real difference in the measurements that I could see was the slope of the phase was shallower, especially near the crossover point. Instead of wrapping 360 two times it didn't even wrap once. If I were looking at phase alone, the Bessel looked better, if flatter phase is the goal. FR plots between the two filters looked nearly the same though, and I couldn't hear a definitive different between the different filters either, all other things being equal. But like I mentioned early, the miniDSP plug-in is not A/B friendly. By the time I had set and reset all 3 channels, low pass and high pass for both sets of speakers, my brain had already forgot what the previous settings sounded like. I didn't play around too much though with it. I liked the Bessel filter's overall response, it sounded fine. And the phase linearity/flatness was clearly better. But I went back to the tried and true LR instead.

Let me know if there are any other plots you'd like to see. I've got the distortion plots, impulse plots, decay, whatever REW can do. There was a time when I never even measured the speakers I finished, it was all by ear and when it sounded good enough, well that was good enough! Now I hardly know what to do with all the data I can get out of a new pair of speakers. It boggles the mind...

[Sydney]

Thanks Sydney for the link. I hadn't considered the idea of adjusting phase response in the same manner as adjusting frequency response. Pretty wild stuff. While I haven't had a chance to try it out, ...

Hope you have an opportunity to do so; addressing such issues is one of the large advantages of DSP.

[rickcraig]

Nice work on your design. As far as 24dB versus 48dB slopes your problems may have been with the off-axis response. I've used both FIR and IIR filters and either one will sound excellent when the calibration / design is optimized. I know some listeners prefer FIR based on the phase issue; however, I'm not sure there is a definite audible advantage. If possible it would be nice to do instant comparisons between the two.

It looks like you have the original 2x4 so you cannot implement FIR filters. The 2x4HD supports FIR and also has four presets that you can switch between on the fly. FIR does allow tighter response tolerances in the upper frequencies but I'm not sure to what extent the HD unit can do that versus the standard 2x4 as it depends on the number of filter taps available.

[AlexRivera]

Great Project, Congratulations, I love the level of detail you have in your personal Blog.

I've been thinking about building something like this but with curved CNC'd cabinets and your project has me thinking about these Drivers and the whole miniDSP setting, now the challenge I have is finding a good (on a budget) multi-channel amp, I have googled Emotiva UPA-700 and it looks like they have turned into the holy grail and they are in the loose, any options currently in the market you could recommend? Again not very crazy expensive in order to keep your initial premise of "building low-cost, high-performance DIY speakers".

Will this guy do it?


https://www.parts-express.com/dayton...0wpc--300-8150


OR, does anybody know a receiver that will really and SIMPLY send the same power level to all channels without treating the non-front channels as surround or alike?

I have Pioneer ELITE SC-85 and Yamaha TSR-5790 and I haven't been able to accomplish that, if there's a "modern" networking receiver that you know about that will do this in an easy way I'd also appreciate your suggestions.

Dan, How did you do that in your setup?

Thanks in Advance!

[danmarx]

You're right, I only have the base 2x4 which after further reading like you said, it doesn't support FIR filters. Bummer, so I'll just have to use that as an excuse to one day upgrade both my 2x4s for 2x4 HDs (not to mention the higher sample rate, better dynamic range and other features). For now I am really happy with just the regular 2x4s, they provide plenty of control for crossovers/EQ and to my ears sound just as transparent as they can be.

Thanks Alex! And yes, for anyone else interested in more details on this project or some of my other projects, you can check the link to my blog/website in my bio. The UPA-700 was a perfect fit for a stereo 3-way active setup, it's too bad that they discontinued that model. If I were to do this again today, I would probably stick with Emotiva and would check out the A-700 amp. It's a couple hundred dollars more than than the the older UPA series but nearly identical specifications. I would think it would be a good contender for an active setup such as this and is still well worth the asking price. I would pick up the A-700 before I dropped the same cash on that Dayton 12-channel multizone/whole house audio class D amp.

I can't answer your question about using a 7-channel receiver in an active setup such as this. I'd be worried about the same things you mention, unnecessary surround sound processing or just discontinuous amplifier behavior across the 7 (or 6) channels which are driving woofers/mids/tweeters in a simple stereo setup. I would think it could be done, just as long as the receiver has discrete inputs and is rated for equal power to all channels. You just have to find a receiver with separate analog inputs for 6 channels (to be pre-processed externally) at which point I would think they would leave the channels alone and just provide simple amplification. I've got a Pioneer VSX-1021 which does not have discrete inputs but my older (15-years) Sony ES receiver had discrete analog inputs. Just the same, I prefer an amp-only solution for tri-amplification of active speakers.

[ontariomaximus]

I bought a NAD 906 for less than $200. 6 channels. There are quite a few options out there.

[Michael P]

Those are beautiful speakers. Can you explain what stain or dye you used on the plywood to get that silver look?

Good luck tuning the crossovers; for me, the challenge with a MiniDSP would be to just listen for a few days and let the changes sink in, rather than getting up and tweaking constantly.

[danmarx]

Thanks Michael for the kind words! The birch ply was first treated with Minwax Pre-Stain Wood Conditioner and then stained with Minwax Classic Gray 271 oil-based stain. I think I did 4 coats and sanded with 320-grit sandpaper between coats. The wood sides looked fine enough like just this but I finished off the speakers with a Minwax Polycrilic satin clear coat. I only did 2 coats on the sides because that was all it needed but ended up doing more on the front and top (mainly because I kept botching that final coat). Lastly, I buffed everything out with Howard's Feed-N-Wax and some microfiber cloths. I swear this is not an endorsement for Minwax, it's just convenient, it's what Home Depot sells, is inexpensive and it works. I claim zero professional experience in finishing wood however and I made my fair share of mistakes on these speakers and speakers in the past. Using the pre-stain is the result of one of those experiences attempting to get a consistent stain across a large surface, the pre-stain treatment seriously works awesome. And I can't use any kind of stain and varnish-in-one type stuff, I may just be stupid however, but I tried it once and it was a disaster. Minwax only fooled me once with that one! So it's a 4-step approach that works best for me - pre-stain, stain, clear coat, wax and buff! Or is that 5 steps? In the end it feels more like 100 steps, but who's really counting?

[Michael P]

Thanks for the explanation. I once had a bad experience with wood not absorbing my stain properly, and the lesson I took from it was to use a dye stain on "difficult" woods. But if you want a color that can only be obtained with pigment (and I'm guessing that silver is one of them), it's good to know there is still hope with pre-stain conditioner. I'm impressed by how "light" (reflective) the finish appears in your indoor photo, without having obscured the grain.

I have no idea how combined stain and varnish is supposed to work, either. Once I did find a can of tinted polyurethane that looked pretty good, though the color it added was so slight that you'd only notice in a side by side comparison. I guess the lesson is to not try solving too many problems at the same time.

[Ray Tremblay]

Fantastic job. They look great and I know that combination of drivers has the potential to sound downright amazing. Keep tweaking the MiniDSP set up. That's the key to unlocking their full potential.

[Squidspeak]

Got my Rosewood veneer NBL for my similar design $400 a sheet (2) Holy sheet!

[danmarx]

I was super surprised to open this month's sales flyer and see the DM-4 speakers showcased in PE's Project Picks! Thanks Parts Express! That was totally unexpected. Seeing this project in actual print form was such a treat and to have it be part of an actual Parts Express flyer is even more exciting. 15-year-old Dan would be so proud. Here's a link to it if anybody wants to read it - https://www.parts-express.com/pdf/salesflyer18A.pdf pages 18-19. And thanks again to PE for the mention!

[davidsanchez]

Finally circling back to this project. I was curious about what you used as a power supply for your mini-dsp boards and what your thoughts were about the performace of the boards as relates to sound quality and reliability. Also, in the intervening years, have you made any changes or updates to the project? Have you upgraded to the HD boards? Cheers!

[danmarx]

Bringing this thread back from the dead...can't believe it's been almost 4 years since I completed these speakers. So the power supply is just a cheap wallwart, 15Vdc, 1A, non-switching, old-school type with just a big transformer that feeds a pair of LM317 linear regulator boards (from Amazon) set to 10Vdc and 5Vdc each. I don't know if this is a great solution, there's still some 60Hz mains hum present in the speakers (albeit at a very low level) you can hear it if you put your ear to the woofers. Not sure if I've just got a ground loop or if I just need more filtering. It's not audible enough to cause me enough concern to try and fix it.

I haven't changed anything with this setup, I haven't even changed the crossover settings, I got to a point that it was as good as I could get it, and what I deemed good enough and left it alone and have just enjoyed it ever since. I did buy an Emotiva PT-100 pre-amp though to match the UPA-700 this past year. It's been a nice addition, since I didn't really have a good pre-amp before. I have never had a desire to swap out the Mini DSPs for anything else either. Honestly, they sound fantastic, are about as transparent as anything I can hear and do the job perfectly for crossover and EQ duty. I have never had any issues with them either. I think they've been powered on for 4 years straight now probably. Well I might have unplugged them a handful of times just to move around the stereo gear or whatever, but they work flawlessly. Sure the HDs have better specs and all that, but the MiniDSPs aren't the weakest link in this setup in my opinion. I'm still a big of enjoying this hobby while maintaining a reasonable level of affordability. but if I were to do it from scratch again, I would probably do the 2x4 HDs. Probably have a better upgrade path, potential for better sources, better pre, better amp, etc. But I still can easily recommend the originals for the budget-minded.