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The new MiniDSP 2x4HD has made all my skills obsolete. How about yours?

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  • Sydney
    replied
    It's not about obsolescence, but rather additional tools to accomplish a goal - such as a Phased array sound system
    Click image for larger version

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  • emilime75
    replied
    I've got a small army of MiniDSPs. Started using them about 3-4 years ago. I use them in the car and the house. The revelation came to me from being in the commercial A/V industry, and working with various DSPs from Symetrix, BSS, QSC, BiAmp... Started looking for more affordable devices to play with, and found MiniDSP. MiniDSP certainly has its limitations, like closed architecture, somewhat low(but useable) output levels(much better on the balanced versions of their products). What it has going for it is affordability, easy to use GUI, good sound quality, convenience...

    I completely understand the art involved in getting a passive crossover designed and built right, and why some would be against the active route due to the need of more amplifier channels. One still needs to understand pretty much the same principals of passive when setting up an active system. The drivers and the enclosure stay the same, so driver roll-offs, response, distortion, impedance...they still matter, as does woofer enclosure size, alignment, tuning, baffle size... Having said that, the convenience of getting a system up and running with a baseline can't be beat. From there, the ability to tweak, tweak, tweak to your heart's content is a matter of a few mouse clicks. Admittedly, for the tweakers among us(me included) it can be a never ending game at times.

    Driver efficiency matching is no longer a part of the equation. Smaller wattage amplifiers can be used since there are no passive components in the circuit to suck up power. Depending on DSP, Butterworth, Linkwitz/Riley, Bessel...all of them can be tried with 1st to 8th order roll-offs. Parametric EQ to tame peaks. High/low shelf EQs, to tame a rising response of a driver(like using a waveguide to boost low end of a dome tweeter). Also, having the ability to switch between up to 4 filter presets on the fly, for comparison, is just so darn handy. Another example, in the car...preset 1 for that majority of the music I listen to, 2 for bass shy music, 3 for talk radio where too much bass is really annoying, and 4 is the jamout preset, for those times when I just want to turn it up and keep all crossover points in a very driver safe region, but still sound good.

    My home theater L/C/R and subs are all DIY DSPed speaker systems. My bedroom system is DSPed. My kitchen boom box consists of a DSP, a 4x100 amp board and BT/aux in, my cars have DSPed systems...yes, I am a fan.

    I haven't yet tried the HD/FIR filter MiniDSP, and likely won't, as I'm moving to commercial units with open architecture, better gain stages, and the ability of control via IP/serial and, of course, FIR.

    There's really a lot of good to DSP, especially with the affordability of devices like MiniDSP, and "cheap" watts available these days. Someone once made the argument that they don't want to have a rack full of amps and a slew of cables between them and the speaker...and they don't have to. Multi-channel amps that are the same size as a 2 channel(or much smaller if one goes the amp board route), multi-conductor speaker cable can be bought, or made, 4 or 8 pole Speakons for a single connection at the speaker...

    Edit: I haven't yet had an issue with DSP latency, not in the fixed install commercial field, or in my home use. The only instances where this could potentially arise, in my experience, is in large auditoriums where rear fills aren't aligned with the mains, but that's a long distance/room/acoustical issue, not an internal DSP processing latency issue. In these situations, the mains get delayed to sync with the rears, which works to various degrees, depending on the room itself, and the room/system integration. Even then, if video projection is part of the system, I haven't yet experienced any visible/audible sync issues. I imagine some of this latency talk comes from those with experience with home recording on a computer and using a hardware interface for inputs/outputs. In those situations, yes, latency is a much bigger contender, and needs to be kept minimal, but it's a different ball game with system playback.

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  • Sydney
    replied
    On Latency:
    http://www.yamahaproaudio.com/europe...olute_latency/
    Live Sound:
    " The total system latency must be considered and managed carefully to ensure the best sound. ‘In-ear monitor’ applications are the most demanding and least tolerant of latency of any kind; a latency between about 5 and 10 milliseconds becomes noticeable, above 10 milliseconds the delay becomes too obvious. For PA FOH and monitor speaker systems the problem is relatively small, a one millisecond increase in latency corresponds with placing a speaker just 30 centimeters further away. "
    from http://download.yamaha.com/api/asset...asset_id=47399

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  • Sydney
    replied
    Additional:
    http://download.yamaha.com/api/asset...asset_id=54114
    Another article in: Live Sound Nov 2013
    https://www.dirac.com/dirac-blog/equ...tandard-toolbo

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  • TN Allen
    replied
    This looks useful too, if I can understand it, it may be a way to do what I asked about above, shaping a response curve for 2 channels L&R.

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  • TN Allen
    replied
    Originally posted by Sydney View Post
    Thank you for this. It looks very informative, I scimed part of it on my phone, but need to read it in a larger format.

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  • Sydney
    replied
    Originally posted by vapor602 View Post
    ... no amount of DSP will fix that, correct?
    See this example

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  • Sydney
    replied
    Additional
    http://www.hxaudiolab.com/uploads/2/...ctitioners.pdf

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  • scottvalentin
    replied
    If I read the links on the IIR vs. FIR filters (FIR being what the MiniDSP HD version does) then it can adjust phase separately from frequency, which means that the HD version will fix any phase issues and produce a linear phase response for the whole range of frequency. Which is a good thing!

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  • vapor602
    replied
    Originally posted by TN Allen View Post
    I've used the 2X4 with a Sure 4X100 amp. for 2 way systems driving each channel with a separate MiniDSP channel, shaping the signal individually for each driver. However, just out of curiosity, has anyone tried using 2 channels with each driving a 2 way tweeter/woofer combination, with a protective capacitor on the tweeter. In other words shaping the outputs using only 2 MiniDSP outputs, one each for L&R. I know this is unconventional, but has anyone tried it?
    Maybe I'm not interpreting this correctly, but it seems acoustic phase would be a problem. One of the most important aspects of the crossover is the phase alignment, not just matching the output level. If the speakers are out of phase, no amount of DSP will fix that, correct?

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  • rpb
    replied
    Originally posted by TN Allen View Post
    I've used the 2X4 with a Sure 4X100 amp. for 2 way systems driving each channel with a separate MiniDSP channel, shaping the signal individually for each driver. However, just out of curiosity, has anyone tried using 2 channels with each driving a 2 way tweeter/woofer combination, with a protective capacitor on the tweeter. In other words shaping the outputs using only 2 MiniDSP outputs, one each for L&R. I know this is unconventional, but has anyone tried it?
    What you could do is make a crude filter for both the woofer, and tweeter that gets the blend from one to the other in the ballpark. Then use the DSP for BSC, and smoothing out any peaks. This might be a way to get a good x-over for a small box that doesn't have much room, or for use with a driver that has some issues that could be handled passively, but not cheaply. You should pick up some headroom above 400hz since the BSC would be accomplished by reducing the amps signal to the speaker.

    I just tried this in PCD. I used my current 2-way. The filter I ended up with for use with DSP was still 7 parts, which is about half as many as my passive, but I was forced to cross lower than my passive design. Attempts to do it with three or four parts did not work. Not even close. Two of the seven parts were resistors. They were important for getting a nice impedance.
    Last edited by rpb; 08-19-2017, 10:07 PM.

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  • johnnyrichards
    replied
    I own my skills, and I decide when they are obsolete ;-)

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  • TN Allen
    replied
    Thanks for the response, I was thinking active, and for the combined tweeter & woofer, but no passive crossover circuit. This would not be as versatile as one channel per driver, but if the drivers were chosen carefully, might work with a single stereo amp. with L&R speakers.

    I'm thinking of ways to use a Dynaco tube amp., as I mentioned in an earlier post in this thread. The 2X4HD looks like a simple, possibly elegant way to interface a digital source and tube power amp without a preamp and separate DAC. I realize there's probably no real advantage to this, however, it's something I've wanted to try. I could also add a second Dynaco, and use 4 channels, using 1 MiniDSP output per amp channel.

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  • ani_101
    replied
    Originally posted by TN Allen View Post
    I've used the 2X4 with a Sure 4X100 amp. for 2 way systems driving each channel with a separate MiniDSP channel, shaping the signal individually for each driver. However, just out of curiosity, has anyone tried using 2 channels with each driving a 2 way tweeter/woofer combination, with a protective capacitor on the tweeter. In other words shaping the outputs using only 2 MiniDSP outputs, one each for L&R. I know this is unconventional, but has anyone tried it?
    Not unconventional, three are quite a few 3 ways and 4 ways, where the DSP is used for crossover only for the bass or room response shaping, the TM or TMW are passive and the bass drivers or sub is active. But it is usually more than just a cap on the tweeter, usually a full fledged passive XO.

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  • Ron_E
    replied
    Originally posted by Millstonemike View Post

    Increasing taps (samples) increases delay. At what point does this start to interfere with the human perception of audio/video sync?
    I use Bodzio's Ultimate Equalizer and the manual says the tolerable limit of latency is 185ms.

    Ron

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