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Old 4th April 2013, 07:26 AM   #811
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There is no pinconfiguration marked for the ir remote, just "1".

The one I have has markings, Dat1, vcc and gnd.
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Old 4th April 2013, 08:43 AM   #812
chaparK is offline chaparK  Luxembourg
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Quote:
Originally Posted by dahlberg View Post
There is no pinconfiguration marked for the ir remote, just "1".

The one I have has markings, Dat1, vcc and gnd.
Hi Bengt,

See section I.5 in the manual.

Nick
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Old 4th April 2013, 08:47 AM   #813
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Originally Posted by chaparK View Post
Hi Bengt,

See section I.5 in the manual.

Nick
Thanks
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Old 5th April 2013, 03:00 AM   #814
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Quote:
Originally Posted by chaparK View Post
Quote:
Originally Posted by DSP_Geek View Post
Re a limited number of taps, one can do complementary highpass and lowpass FIRs by running a unity-gain odd-order lowpass linear-phase filter with N taps, then subtracting the full range input signal delayed by (N-1)/2 samples. For example, use a 401 tap LPF as the generator function, subtract the input delayed by 200 samples to obtain the HPF, and you're good to go. That more or less halves the computational load.
I remember you already posted this idea earlier. Please accept my apologies for not answering earlier.
There's however a problem I can see with your approach, it's that indeed the filters are complementary. Most of the time, FIR specifications include driver EQing (see Paal's examples) so complementarity is actually not desired. Please correct me if I misunderstood.

Quote:
I'd recommend against FIRs for low frequency room correction. Room gain is minimum-phase, as with other physical processes, so a parametric EQ does the job beautifully while consuming far fewer clocks.

@Chapark: would you be interested in a minimum-phase resampler?
Can you please develop?
CROSSOVER:
First let's look at complementary filters. Let's start by assuming no correction (we'll get to that later) and a 3 way system. The bass output is set up with a standard LPF FIR, the mid is driven by the HPF complementary to the bass filter, followed by a standard LPF for the upper rolloff, and the tweeter is driven by a standard HPF. This looks like a typical 3 way crossover, with the exception of using complementary FIRs between the bass and mid outputs. Why would we do such a thing? Let's take an example, with crossovers at 200 Hz and 3000 Hz. The 200 Hz FIRs might be 750 taps long while the 3000 Hz FIRs would be 50 taps long (in keeping with the observation that FIR lengths are more or less proportional to the inverse of their cutoff frequencies). Running separate FIRs for all sections yields 750 taps for the bass, 750 + 50 taps for the mids, and 50 taps for the highs, for a total of 1600 taps. Using complementary filters gives 750 taps for the bass, 50 taps for the mids (assuming trivial computation for the complement), and 50 taps for the highs, for a total of 850 taps. You save almost half the clocks.

Now, of course, people want to correct response aberrations in their speakers, and the crossover with its FIRs is a logical place to look. However, one must consider exactly what is being corrected. Speakers below their breakup frequency have few high-Q resonances, so one doesn't need high resolution in the frequency domain to fix whatever problems may occur. In that case an IIR solution is quite sufficient. Extending the response of a mid down an octave or two with a Linkwitz transform, for example, is entirely doable. Now consider that cone breakup for a 12 inch woofer is a few hundred hertz and about a kilohertz or two for an organic cone midrange, and one can see extreme frequency resolution is not overly critical. However, it'd still be nice to flatten the midrange with a FIR; that's where the separate lowpass FIR on the mid section comes in, since the correction can come in on the shorter FIR without disturbing the complementary filters between the bass and mid. Even if you triple the length of the LPF on the mid, so frequency resolution is 44100 / 150 = ~300 Hz, you're still running 950 taps for the corrected system as opposed to 1600 taps for the naive implementation.


RESAMPLER:
Apparently, under critical listening, people seem to prefer minimum-phase FIRs for reconstruction filters. I haven't tested them extensively in that use, but it might be an amusing option for DIYers to try. The impulse response looks like a sharp cutoff IIR (which makes sense since it's a minimum phase filter just like an IIR) with about the same total amount of ringing as the equivalent linear phase filter, but all pushed to the right. However, one doesn't get away with the linear-phase half-band resampler trick of having every even sample merely be the copy of the input while the odd samples are processed through the FIR, because a minimum-phase filter has no zeroes in the impulse response as half-band linear-phase filters do. On the other hand, you must zero-stuff the input so only half the computation is needed for each 88200 Hz sample. I'm already using a minimum-phase FIR in another application (day job, can't talk about it) and it works quite nicely. I could fire off a set of coefficients for you to build a resampler on if you want to give it a go.
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Old 5th April 2013, 03:06 AM   #815
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Originally Posted by chaparK View Post
In short: 2 more outputs, we could make this happen shortly.
6 more outputs would take much (much much actually) longer.
ESAI limitations, eh?

BTW, have you considered daisychaining multiple DSPs? After the first extra one it's pretty well plug & play from what I understand.
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Old 5th April 2013, 11:37 AM   #816
chaparK is offline chaparK  Luxembourg
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Originally Posted by DSP_Geek View Post
CROSSOVER:
[...]

RESAMPLER:
[...]
Hi DSP_Geek,

Thanks for this interesting reading. Right now we have defined other priorities but these are good ideas for future developments.

Quote:
Originally Posted by DSP_Geek View Post
ESAI limitations, eh?
No. 2 extra processing channels are already available in the system, and a 2-channel analogue expansion could easily take profit of it.
More channels would require a new software+firmware. That is actually the limitation in time and cost.

Quote:
BTW, have you considered daisychaining multiple DSPs? After the first extra one it's pretty well plug & play from what I understand.
Hmm not really. What would you daisy-chain DSPs for?
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Old 5th April 2013, 12:13 PM   #817
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Quote:
Originally Posted by chaparK View Post
No. 2 extra processing channels are already available in the system, and a 2-channel analogue expansion could easily take profit of it.
More channels would require a new software+firmware. That is actually the limitation in time and cost.

Hmm not really. What would you daisy-chain DSPs for?
Yeah - I see the blanked out sections in the menus for these two

Daisy-chaining you would have to control the vols of each unit separately I think? - Not a solution for me - could work nicely for multiple room setups though.
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Old 5th April 2013, 06:08 PM   #818
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Default It works

Proof positive anybody can assemble one. Finding my eye glasses was the hardest part. All systems nominal. The green LED on the left is power on light so I know to shut it down when I quit. I searched Ebay for a Hitachi hd44780 compatible LCD, it works perfect. Case is from DIYAUDIO.com Working on filters now.
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Old 5th April 2013, 06:48 PM   #819
chaparK is offline chaparK  Luxembourg
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Hi Mark,

Thanks for posting the pics and congratulations for the build, looks good!! That's actually the first real build we've seen here, that made my day

Are you using a IR receiver?

Best,

Nick
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Old 5th April 2013, 07:19 PM   #820
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Default It works

I got the little cheapie key chain remote off Ebay shown earlier in this thread. It does not have all the function buttons, but otherwise works fine, ie: (no numbered buttons for channels).
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