TOPIC:

Can the DDRC-24 be set to mono so all of the tags are used on a single stereo channel and use one DDRC-24 for the right channel and one for the left channel and provide (4) filtered outputs for each of the right and left stereo speakers sets?

Do you have a pair of 4-way speakers, or something else?

I have a 3 way speaker and the 24 has only 2 outputs for the right channel and 2 outputs for the left channel. 

johnnetzel wrote:

I have a 3 way speaker and the 24 has only 2 outputs for the right channel and 2 outputs for the left channel. 

OK, I'm sure you don't want two DDRC-24s then. Are you looking for miniDSPs to act as crossovers for your speakers? Full details of your setup would be helpful here  .

What I don't want to do is provide a signal DDRC-24 for DIRAC live and go in with left and right digital stream, then come out with 4 analog streams when I need 6 streams.  If I use 2 DDRC-24s I have 8 streams which I can reduce to 6 streams.  For full details a have a DIY 6 channel 100w/ch amplifier with 0.003% THD, bias for class A operation to 3w/ch, balanced,  and a band width of 7hz to 700khz, and yes you can see the 1mhz, 0.3Volt digital noise from the minidsp digit filter on the output of the amplifier with a scope.  The amplifier inputs have an input impedance of 3k ohms and full power at 1Volt.  For input I use a minidsp USB to SPDIF converter to the minidsp digit filter to analog outputs on the minidsp digit filter that are connect by RCA phono cables the power amplifier.  The phono cable plugs are isolated from the cabinet frame so they are only grounded at the minidsp digit filter and the IC board of the amplifier.  I use RCA phono cables inside the RCA phono cables to the amplifier board to reduce hum and noise.  End result is the output of the 600w amplifier is dead quite,  no sign of any noise on the scope or audible 1 inch from the speakers and very fast.  A lot of wasted detail here for just a simple power amp with 6 separate amplifiers and minidps digital electronics between the PC and the amplifiers.

Per the instructions for the DDRC-24 DIRAC live the tuning is done by blocking the left channel and using DIRAC live auto tune to tune the right channel.  Then tune by blocking the right channel and using DIRAC live to tune the left channel.  By tune I mean to set the FIR filters in the DDRC-24 to provide the best compromise between impulse response and flat spectrum response.  I would use the IIR filters provide a woofer stream, and FIR filters to provide a mid stream, and a tweeter stream for the right channel and the left channel.  This is easy to do and the 2 DDRC-24 allow me to do this.  But it looks like the DDRC-24 splits the tags for the FIR and IIR filters to 2k tags per outputs per stereo channel so at best I can only use 6k of the available 8k tags.  The other question is does DIRAC live tune for each channel separately and then and tune for the combination of both channels.  If DIRAC live tunes for both channels combined how do I do this with 2 DDRC-24s?  The other solution is to put a passive filter for each of the mid-tweeter speaker left-right pair and then use a single DDRC-24 with 4 outputs for 4 power amps.

At this point I'm looking at miniDSP Flex to provide a DDRC-24 analog stereo output stream to a set of active analog filters. Then split the left right streams into left woofer, left mid, and left tweeter and right woofer, right mid and right tweeter.  And add a passive 200khz low pass filter between the miniDSP and the active filters to clean up the high frequency digital noise and attenuate the miniDSP signal by about 10db with simple resistors to attenuate the audible part of the white digital buss noise.  You know adjust the gain structure.   

FYI the DDRC-24 doesn't have FIR filters (that you can set up yourself). 

Have you read the following white paper on Dirac Live?

diracdocs.com/on_room_correction.pdf

I'm asking as it somewhat sounds like you have ideas to do manually things that Dirac is doing anway. I think you need to decide whether you want to use Dirac Live to do its thing, or to do things manually. Not both.

johnnetzel wrote:

The other question is does DIRAC live tune for each channel separately and then and tune for the combination of both channels.  If DIRAC live tunes for both channels combined how do I do this with 2 DDRC-24s?  The other solution is to put a passive filter for each of the mid-tweeter speaker left-right pair and then use a single DDRC-24 with 4 outputs for 4 power amps.

 

Just on this point I'll say again tht you definitely don't want two DDRC-24s. What Dirac Live does is run an automated sequence of three measurements of one speaker, then the other, and then the first one again. I believe the algorithm then factors in both the individual speaker measurements and the sum.

The way some have used Dirac Live with 3-way active designs is to use one DDCR-24 daisy-chained with another non-Dirac 2 input / 4 output miniDSP. This isn't something I have any personal experience of but here is one example:

www.minidsp.com/forum/diy-hifi-projects/...tannoy-drivers#46761

I'm trying to avoid the daisy chain of digital to analog to digital to analog.  Say a PC plays an analog signal that it converted from a digital signal and sends it to the analog inputs on a DDRC-24 that converts it to a digital signal then filters it and adds some noise and converts it back to an analog signal.  This is sent to another digital filter where it converts the analog input to a digital signal and filters it and adds some noise converts it back to an analog output signal.  This is different from going digital filter to another digital filter but even this will add some noise to the final analog signal. 

Yes I know DIRAC says they do not use filters they just use a digital signal processor, that is typically used for FIR and IIR digital filters, to process the signal.  I also read where EVs are zero emission vehicles because they use electrical power but I don't buy that either.  The emission just come out a different smoke stack in a different state.

Very simple logic says that if you use 2 digital signal processors, (not digital filters), one in each DDRC-24 you would have twice the processing power, kind of like using a PC with a 2 core processor.  I don't know what the final step is when the DIRAC program processes, (not filter or delay) a common signal on both channels.  It maybe nothing more then synchronizing the two signals over the audio band to avoid comb filtering at the higher frequencies.

May be miniDSP will combine 2 DDRC-24 processors into a single box with 4 channels per processor and a DIRAC program to auto tune both processors.  By using more processing power and more tags the noise from the digital filters could be pushed down another 10db and provide 4 outputs per channel to drive 3-way speakers. 

 

I understand the desire to minimise A-D-A conversions.

Why aren't the DDRC-88A or 88D better options for you?
What are your sources?

A better work-around for 2x DDRC-24s may be to run them stereo high and stereo low rather than full range left and full range right. DIRAC wants to listen to both speakers in the room for its correction. I know you can tell DIRAC to ingore frequencies of a particular range. (some audio reviewers tell DIRAC to leave the upper frequencies alone). 
So set one DDRC-24 to handle both channels of low (and subs down the track), the other DDRC-24 to handle both channels of mid & high.

 

daveing wrote:

A better work-around for 2x DDRC-24s may be to run them stereo high and stereo low rather than full range left and full range right. DIRAC wants to listen to both speakers in the room for its correction. I know you can tell DIRAC to ingore frequencies of a particular range. (some audio reviewers tell DIRAC to leave the upper frequencies alone). 
So set one DDRC-24 to handle both channels of low (and subs down the track), the other DDRC-24 to handle both channels of mid & high.
 

That won't work. Dirac Live needs a full-range signal. 

Two DDRC-24s is definitely not a good idea for anyone.

johnnetzel wrote:

Yes I know DIRAC says they do not use filters they just use a digital signal processor, that is typically used for FIR and IIR digital filters, to process the signal.
 

I have no idea what you mean here and don't recognise this a relating to anything that Dirac Live say that they do.

I fully understand you're desire to avoid unecessary A/D and D/A steps and this is something I do myself. Sadly miniDSP don't make a single product that does all you want. We could get into discussing other optoins but first I think we need to establish whether you really want Dirac Live or not.