To replace my ailing Yamaha YDP-2006 parametric EQ, I purchased an OpenDRC from MiniDSP.com. Largely purposed for home theatre enthusiasts doing “Digital Room Correction” this processor is a 2-in/2-out unit, 32-bit floating point SHARC DSP, running at 48k (although original specs promise a software update to 96k). It is essentially driverless, with control software running in platform-independent Adobe Air. I bought the unit to apply some EQ to my office speaker system (Blue Sky Sat 8s and Sub 212). My speakers are very well behaved but my environment calls for a small bit of EQing and the option to do FIR filtering also intrigued me.
The pictures make this metal box look sturdy but upon unboxing it, I found build quality to be less than I was expecting. It is metal, but it’s a little flimsy. Regardless, it seems well put together and features XLR inputs and outputs, DC power input, and USB connection, on the back, and a multi-function knob and preset indicator on the front. The knob serves to control the master volume of the unit (in 0.5db steps) along with being able to choose between the 4 presets you can program. While the ability to select the preset on the front panel is a plus, I was really hoping that this knob was analog. Turning the knob up and down in such small increments means many many many many (many) turns to ramp up and down.
The OpenDRC unit allows for MiniDSP plug-ins with specific functionality to be installed onto it, depending on the project. Right now, the only plug-in that exists is a 2x2 system featuring 6 bands of parametric EQ on the inputs, optional crossover slopes, a FIR filter section, and outputs with compressor/limiter and polarity inversion. Both input and output sections offer level control in 1db increments. This plug in runs at 48kHz.
I started by just measuring the device. It exhibits a polarity invert from input to output and after some conversations with Bennett, it would seem that the 24db and 48db Linkwitz crossover filters are actually the same slope just at different frequency points with the LR24 being under-damped.
I connected my speakers and Smaart and started to EQ. The EQ section works, but I can’t say it sounds any better than the Yamaha it was replacing. At this point, I spent less time worrying about things like whether their definitions of Q are worthwhile and more time just massaging the levels to get my desired outcome. I finished up hoping I could have one or two more filters available to me, but was decently happy with the outcome. Again, switching back to the Yamaha it was replacing, I really didn’t feel I gained or lost anything sonically, and this unit seems to really just be a replacement for the Yamaha which has been exhibiting typical aging Yamaha knob control issues. Strangely enough with no gain added or removed from EQ filters, I could hear small fluctuations in the pink noise I was running when I drug the frequency slider around. I haven’t investigated this fully, but just noted it.
The next round was to utilize the FIR section. Since I don’t possess the knowledge to create these filters myself, I looked to Python Open Room Connection (PORC), a solution developed by a guy who has remained active on the forums at MiniDSP.com. With his help, I sent him an impulse response of my system and he ran the information through his program which churned out a myriad of FIR filters.
The result was quite different than what I was hoping I’d get. In live sound, we implement FIR to remove frequency and time and thus be able to manipulate the phase response better. With these DRC solutions, it would seem that the FIR implementation is really just a system by which they can cram a ton of filters into one system. They seem to generate a multitude of useless filters that largely ignore everything we teach in live sound about how to EQ a system. Now I know that given a perfect environment, my speakers are very well behaved. They do not need the 25+ filters (well the ones I was able to visually count) that PORC generated for my system, and after applying those filters to my OpenDRC, my system sounded like poo. While I have no doubt that such “auto-eq” systems can help the hobbyist at home make their system sound better than they could do alone, for those of us who know how do to this on our own, it’s absolutely useless.
I decided that the FIR section of this plug-in was useless to me so I went about submitting a request to the development team at MiniDSP (who is quite responsive on their message boards) to create a plug in that increased the number of standard EQ filters by getting rid of the FIR section (and did so at 96kHz). I also wanted the option to either entering custom bi-quads for all-pass filtering or having a software interface for using those all-pass filters. They responded saying that it wasn’t the direction the community wanted the product to go in, hence why they created the unit to begin with, and I replied with my hope that they could make it more versatile by giving it such options.
In the end, I still have this OpenDRC in my system. I’m not unhappy with the money I spent, and given that, it lives up to my expectations. It’s not a Lake processor – I’m not expecting it to sound like one or EQ like one. I’m hoping for some software updates and in the meantime I’m still keeping my eyes open for nicer (used) EQ gear at a decent price. The OpenDRC is by no means a professional-grade speaker processor, but a hobbyist tool for home audio systems and if you’re looking for an inexpensive device to do some processing on your speakers at home, I recommend giving it a try.
The pictures make this metal box look sturdy but upon unboxing it, I found build quality to be less than I was expecting. It is metal, but it’s a little flimsy. Regardless, it seems well put together and features XLR inputs and outputs, DC power input, and USB connection, on the back, and a multi-function knob and preset indicator on the front. The knob serves to control the master volume of the unit (in 0.5db steps) along with being able to choose between the 4 presets you can program. While the ability to select the preset on the front panel is a plus, I was really hoping that this knob was analog. Turning the knob up and down in such small increments means many many many many (many) turns to ramp up and down.
The OpenDRC unit allows for MiniDSP plug-ins with specific functionality to be installed onto it, depending on the project. Right now, the only plug-in that exists is a 2x2 system featuring 6 bands of parametric EQ on the inputs, optional crossover slopes, a FIR filter section, and outputs with compressor/limiter and polarity inversion. Both input and output sections offer level control in 1db increments. This plug in runs at 48kHz.
I started by just measuring the device. It exhibits a polarity invert from input to output and after some conversations with Bennett, it would seem that the 24db and 48db Linkwitz crossover filters are actually the same slope just at different frequency points with the LR24 being under-damped.
I connected my speakers and Smaart and started to EQ. The EQ section works, but I can’t say it sounds any better than the Yamaha it was replacing. At this point, I spent less time worrying about things like whether their definitions of Q are worthwhile and more time just massaging the levels to get my desired outcome. I finished up hoping I could have one or two more filters available to me, but was decently happy with the outcome. Again, switching back to the Yamaha it was replacing, I really didn’t feel I gained or lost anything sonically, and this unit seems to really just be a replacement for the Yamaha which has been exhibiting typical aging Yamaha knob control issues. Strangely enough with no gain added or removed from EQ filters, I could hear small fluctuations in the pink noise I was running when I drug the frequency slider around. I haven’t investigated this fully, but just noted it.
The next round was to utilize the FIR section. Since I don’t possess the knowledge to create these filters myself, I looked to Python Open Room Connection (PORC), a solution developed by a guy who has remained active on the forums at MiniDSP.com. With his help, I sent him an impulse response of my system and he ran the information through his program which churned out a myriad of FIR filters.
The result was quite different than what I was hoping I’d get. In live sound, we implement FIR to remove frequency and time and thus be able to manipulate the phase response better. With these DRC solutions, it would seem that the FIR implementation is really just a system by which they can cram a ton of filters into one system. They seem to generate a multitude of useless filters that largely ignore everything we teach in live sound about how to EQ a system. Now I know that given a perfect environment, my speakers are very well behaved. They do not need the 25+ filters (well the ones I was able to visually count) that PORC generated for my system, and after applying those filters to my OpenDRC, my system sounded like poo. While I have no doubt that such “auto-eq” systems can help the hobbyist at home make their system sound better than they could do alone, for those of us who know how do to this on our own, it’s absolutely useless.
I decided that the FIR section of this plug-in was useless to me so I went about submitting a request to the development team at MiniDSP (who is quite responsive on their message boards) to create a plug in that increased the number of standard EQ filters by getting rid of the FIR section (and did so at 96kHz). I also wanted the option to either entering custom bi-quads for all-pass filtering or having a software interface for using those all-pass filters. They responded saying that it wasn’t the direction the community wanted the product to go in, hence why they created the unit to begin with, and I replied with my hope that they could make it more versatile by giving it such options.
In the end, I still have this OpenDRC in my system. I’m not unhappy with the money I spent, and given that, it lives up to my expectations. It’s not a Lake processor – I’m not expecting it to sound like one or EQ like one. I’m hoping for some software updates and in the meantime I’m still keeping my eyes open for nicer (used) EQ gear at a decent price. The OpenDRC is by no means a professional-grade speaker processor, but a hobbyist tool for home audio systems and if you’re looking for an inexpensive device to do some processing on your speakers at home, I recommend giving it a try.