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DSM variable volume on digital out?
2017-09-24, 18:46
Post: #11
RE: DSM variable volume on digital out?
(2017-09-24 13:49)Briain Wrote:  
(2017-09-24 13:09)Bosco Birdswood Wrote:  I wonder if I could replicate the SO EQs with the miniDSP convincingly? I don't believe SPACE processes anything in the time domain?

Finalyy, one thing I will say is that the DSM amp is much better than the amp I'm currently using. Definitely justifies looking into the 4100.

Hi

I haven't paid much attention to the FIR versions, but I did briefly look (shortly after they first appeared) and I seem to remember that folks were designing compilers to enable them to be set up as linear phase crossovers (and perhaps even facilitate corrections to be applied for unit and cabinet anomalies, as Linn do in Exakt; of course, you'd need to build your own anechoic chamber to measure such things; that could be the tricky part). As SO is done in the DS, it will be using IIR and thus there will be small phase wiggles (but likely they are quite small due to the nature of the dips it applies) so I guess it might be possible to do SO in the miniDSP, and as you'd be using FIR, the wiggles would be a lot less.

Apologies if any of the above is incorrect; my field is in matters of radio and my knowledge of FIR technology is very limited (one day, I must rectify that).

Bri

PS Are you aware of anyone (with ears like our ones) having compared the traditional miniDSP to the new SHARK based ones (in terms of sound quality when both are used in IIR mode) and commented on same?
I hadn't really thought of that re SO being IIR although Linn are pretty fastidious with these things. I actually started off with the miniDSP 2x4 and then upgraded to the 2x4HD pretty much just for the FIR capability and I can honestly say the difference is night and day. Having implemented both IIR and FIR with the HD I'd say that much of the difference is due to the SHARC processor. That being said I do use FIR filters created with rePhase and they sound amazing. No need for an anechoic chamber though! As the crossover is at 400hz you can actually get pretty good readings outside if you elevate the speaker enough to make the ground reflection delay long enough. After that you window the response to exclude the reflections to get a pretty good idea of what is going on. In all honesty all I have baked in to the FIR filters is a 2nd order Linkwitz Riley crossover and a low shelf boost on the ESL panels to counteract the effects of dipole cancellation. I have a shelf boost on the woofers as well but had to use the standard IIR EQ as there wasn't enough "taps" available to create this boost without some serious phase issues for some reason.

I might try implementing the SO settings to see if it works though as per your suggestion!
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2017-09-24, 19:48
Post: #12
RE: DSM variable volume on digital out?
I am getting very tempted to get one and use it's IIR filter option for my 345 sub. Even if it is better (in terms of applications where you are using the full audio spectrum) in my case, it's only feeding a sub, so I have my doubts as to whether it''ll make much of an audible difference, but hey, they only way to find that out is to get one and whack it into the sub feed, so I think I'll maybe give it a shot.

I'm actually planning to get a sub for my bedroom system, so I'll also need a miniDSP for that and thus at least I can re-deploy my existing 2x8 (rather than just adding it to the creaking and dusty - and rather alarmingly extensive - shelves of past HiFi equipments)!

Big Grin

KDS/1 (music) + ADSM (AV) -> KK/1 -> 350A + miniDSP time & phase aligned 345 rear sub
KDS Renew -> Homebrew fixed attenuator -> 2250/D -> 212 and Sizmik front sub (bedroom)
MDSI -> 104C (awaiting installation in my kitchen)
MDSI -> Shahinian Arc (installed at my mum's house)
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2017-09-24, 19:59 (This post was last modified: 2017-09-24 21:05 by Briain.)
Post: #13
RE: DSM variable volume on digital out?
Oops, I was just pondering the merits of the 2x4 HD and I seem to have accidentally bought one (the danger of using the Internet after drinking lots of nice wine) so it will be interesting to see how it compares to my current one (given it's just a sub feed, I expect to not hear any difference, but I do love playing with technology and no matter what happens, I'll soon be needing another miniDSP for a future bedroom sub, so nothing will be going to waste). Wink

KDS/1 (music) + ADSM (AV) -> KK/1 -> 350A + miniDSP time & phase aligned 345 rear sub
KDS Renew -> Homebrew fixed attenuator -> 2250/D -> 212 and Sizmik front sub (bedroom)
MDSI -> 104C (awaiting installation in my kitchen)
MDSI -> Shahinian Arc (installed at my mum's house)
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2017-09-24, 23:35
Post: #14
RE: DSM variable volume on digital out?
(2017-09-24 19:59)Briain Wrote:  Oops, I was just pondering the merits of the 2x4 HD and I seem to have accidentally bought one (the danger of using the Internet after drinking lots of nice wine) so it will be interesting to see how it compares to my current one (given it's just a sub feed, I expect to not hear any difference, but I do love playing with technology and no matter what happens, I'll soon be needing another miniDSP for a future bedroom sub, so nothing will be going to waste). Wink

Brilliant, you'll love it! The good thing is you can distribute the taps sold you're only using two channels you can use 2048 taps per channel rather than the 1024 in using on all 4. This will make more sense when you get it!
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2017-09-25, 00:15 (This post was last modified: 2017-09-25 00:28 by Briain.)
Post: #15
RE: DSM variable volume on digital out?
(2017-09-24 23:35)Bosco Birdswood Wrote:  
(2017-09-24 19:59)Briain Wrote:  Oops, I was just pondering the merits of the 2x4 HD and I seem to have accidentally bought one (the danger of using the Internet after drinking lots of nice wine) so it will be interesting to see how it compares to my current one (given it's just a sub feed, I expect to not hear any difference, but I do love playing with technology and no matter what happens, I'll soon be needing another miniDSP for a future bedroom sub, so nothing will be going to waste). Wink

Brilliant, you'll love it! The good thing is you can distribute the taps sold you're only using two channels you can use 2048 taps per channel rather than the 1024 in using on all 4. This will make more sense when you get it!

It will be interesting to play with the HD box (I do have some old Linn Kan units and Kan baffles to experiment with; all I need do is build some boxes and I can then even experiment with 2-way active speakers to see how it sounds in that roll) but at the end of the day, its final role will be using it in IIR mode to drive the sub (as I need to best match it to track the phase shift of my 350s active crossovers; that's the key to best integrating the sub). Sonically, I'd be surprised if it makes a detectable difference (over the current unit) considering that it's only dealing with <100 Hz (or so), but one never knows - far stranger things have happened - so I will keep an open mind, a pair of open ears, and some open wine bottles, too.

Once done, I'll have to dredge up my old thread about setting up the 2x8 unit and write another mega-boring post about measuring the HD unit's native latency (with th two filters set) and then another about phase marching it to my 350s (no doubt accompanied by screen dumps showing suspiciously squiggly lines on a PC screen, well shaky photographs of fuzzy oscilloscope screens - with wine glasses in the background - and likely much other nefariousness); all darned good fun to look forward to (though not for anybody who reads it) and best of all, I'll have to generate lots of low bass to see how it sounds; what a bummer, eh?

Bri Tongue

KDS/1 (music) + ADSM (AV) -> KK/1 -> 350A + miniDSP time & phase aligned 345 rear sub
KDS Renew -> Homebrew fixed attenuator -> 2250/D -> 212 and Sizmik front sub (bedroom)
MDSI -> 104C (awaiting installation in my kitchen)
MDSI -> Shahinian Arc (installed at my mum's house)
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2017-09-25, 00:30
Post: #16
RE: DSM variable volume on digital out?
(2017-09-25 00:15)Briain Wrote:  
(2017-09-24 23:35)Bosco Birdswood Wrote:  
(2017-09-24 19:59)Briain Wrote:  Oops, I was just pondering the merits of the 2x4 HD and I seem to have accidentally bought one (the danger of using the Internet after drinking lots of nice wine) so it will be interesting to see how it compares to my current one (given it's just a sub feed, I expect to not hear any difference, but I do love playing with technology and no matter what happens, I'll soon be needing another miniDSP for a future bedroom sub, so nothing will be going to waste). Wink

Brilliant, you'll love it! The good thing is you can distribute the taps sold you're only using two channels you can use 2048 taps per channel rather than the 1024 in using on all 4. This will make more sense when you get it!

It will be interesting to play with the HD box (I do have some old Linn Kan units and Kan baffles to experiment with; all I need do is build some boxes and I can then even experiment with 2-way active speakers to see how it sounds in that roll) but at the end of the day, its final role will be using it in IIR mode to drive the lounge sub (as I need to beat match the phase shift of my 350s lower bass units; that is the key aspect). Sonically, I'd be surprised if it makes a detectable difference (over the current unit) considering that it's only dealing with <100 Hz (or so), but one never knows - stranger things have happened - so I will keep an open mind, and open ears (and open wine bottles, too).

Once done, I'll have to find my old thread about setting up the 2x8 and write another mega-boring post about measuring its native latency (with two filters set) and then another about phase marching it to my 350s (no doubt accompanied by screen dumps showing suspiciously squiggly lines, shaky photographs of fuzzy oscilloscope screens - with wine glasses in the background - and likely much other nefariousness); all darned good fun (and you then get to play loud music to see if it actually works).

Bri Tongue
Hi Bri,

I look forward to it!! I just tried to create an FIR using rePhase and it didn't come even close to being able to recreate the SPACE EQs. I'll try with the standard IIR PEQs on the miniDSP and see how it sounds.

I'm sure there are many who would turn their nose up at having such cheap little devices in their signal chain but the miniDSPs punch way above their weight and the difference they make is profound in the right application. Plus, I like to think Siegfried Linkwitz knows more than us all and he swears by them!

Cheers, Tom
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2017-09-25, 01:01 (This post was last modified: 2017-09-25 10:55 by Briain.)
Post: #17
RE: DSM variable volume on digital out?
I only relatively recently found out that Russ Riley and Siegfried Linkwitz worked in R&D at HP (and I see that Linkwitz designed RF test equipment). Despite me having a rather extensive collection of HP microwave test equipment (and a very stout floor to support the weight of it all) I don't actually have any of the ones that he was involved with, but it was very cool to find out that he was from that background.

Regarding the miniDSP, yes, I think they are fantastic devices and folks should not be put off by the low prices. Before I installed that, the rear sub was unusable (many folks heard it and agreed that it totally wrecked the sound). Not only did it kill the tunes, but I didn't understand why even at low levels, it 'caused' mid and high frequency distortion, then Phil Budd (Linn Design) explained the precedence effect and it all made sense. That was when I bought the miniDSP to add some delay and the difference is absolutely astonishing. Now, you really cannot tell that there is a sub sitting behind you (even when it is pumping out a lot of bass), but when you mute it, it sounds like you have swapped the main speakers (which do go low) for bookshelf ones, so just as you say, the miniDSP made an absolutely profound difference to the sub.

I am still pondering what to do for the bedroom system; I might buy a sub and use a miniDSP, but I am getting quite tempted to build an Isobarik type sub and use half of an old Linn 2250 board as the amp (one channel is totally fried - vaporised tracks - but I could just whip out the active bits from the fried channel and use the other channel) and of course, I'll use a miniDSP to set the filters and time align it; could end up sounding not too bad.

Fortunately, I have a reasonable amount of space between myself and my nearest neighbours, so nefarious bass experiments have not [yet] earned me an ASBO! Big Grin

KDS/1 (music) + ADSM (AV) -> KK/1 -> 350A + miniDSP time & phase aligned 345 rear sub
KDS Renew -> Homebrew fixed attenuator -> 2250/D -> 212 and Sizmik front sub (bedroom)
MDSI -> 104C (awaiting installation in my kitchen)
MDSI -> Shahinian Arc (installed at my mum's house)
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2017-09-26, 11:31 (This post was last modified: 2017-09-26 12:10 by Briain.)
Post: #18
RE: DSM variable volume on digital out?
Hi

It should arrive by the end of the week; cool! Smile

I have just found out (from miniDSP support) that the 2x4 HD has a basic latency of about 3 ms, whereas the 2x8 that I currently use measured at 1.19 ms (with two filters set up in it) so it's basic latency must be just over 1 ms. The HD will be fine for me as my sub is just over 4 ms closer than my main speakers, so it will only require a setting of about 1 ms (1 ms setting + 3 ms latency = 4 ms total) to achieve that. Obviously, anyone who has a smaller sub to main speakers distance error (than about 1 m) would be better off with the non-HD version, as they would require less than 3 ms minimum resulting from it's basic latency. For my bedroom system, the sub would have to be almost in line with the speakers, so if I do get a sub for that room, I can use the 2x8 in there.

So my plan (thus far) for setting up the 2x4 is as follows:

1. Set it up roughly as required (channels combined, 1 ms delay and roll on and roll off filters) with the output set to one channel (which feeds the sub)
2. Internally route to also provide an unfiltered output channel (such that I can use higher frequencies to measure basic latency on an oscilloscope).

Once I've done that, I'll have a listen and play with the roll on / roll off filters to set them by ear, then eventually (when time permits) I'll do the phase tracking thing:

3. Temporarily set it such that one channel does sub (do not combine input) then feed a 350 on an unfiltered channel, but with overall delay set same as filtered sub channel, then adjust DSP filters such that the phase response (vs frequency) of the DSP tracks that of the 350A's lower bass crossover (in other words, measuring output of bass amp and sub amp).
4. Put 350s back to normal (connected direct to preamp) and repeat step 2 to check latency hasn't changed after any tweaks from step 3, and if all is okay, set it up as per step 1 and play some music.

All a bit of a fiddle, but it should be well worth the effort. If I find step 3 results in roll-off being too high, I'll then have to look at its FIR features (turn the 'taps' on Tongue ) to see if I can change it's roll off without impacting the phase response that I've just optimised vla tweaking the IIR filters (i.e. to keep the results from step 3 true) and likely that will require another check of step 2.

Bri Smile

KDS/1 (music) + ADSM (AV) -> KK/1 -> 350A + miniDSP time & phase aligned 345 rear sub
KDS Renew -> Homebrew fixed attenuator -> 2250/D -> 212 and Sizmik front sub (bedroom)
MDSI -> 104C (awaiting installation in my kitchen)
MDSI -> Shahinian Arc (installed at my mum's house)
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2017-09-26, 12:48
Post: #19
RE: DSM variable volume on digital out?
Hi Bri,

I think you'll be impressed by it! The latency isn't an issue for me because I run all channels through it, resulting in them all encountering the same delay. Two channels go to small ESL panels (http://www.eraudio.com.au mini panels), and the other two go to a pair of sexy Morel Titanium 10" woofers with huge voice coils!

I implemented the SPACE settings on the miniDSP yesterday using just IIR filters and it sounds brilliant.

That being said I also bought a Majik 4100 yesterday so will eventually be back to using SO again in a few months (I'm in Melbourne, amp is in the UK so I have to wait for my dear mother to come over at Christmas with an amp stuffed in her suitcase!)
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2017-09-26, 13:15 (This post was last modified: 2017-09-26 13:19 by Briain.)
Post: #20
RE: DSM variable volume on digital out?
(2017-09-26 12:48)Bosco Birdswood Wrote:  Hi Bri,

I think you'll be impressed by it! The latency isn't an issue for me because I run all channels through it, resulting in them all encountering the same delay. Two channels go to small ESL panels (http://www.eraudio.com.au mini panels), and the other two go to a pair of sexy Morel Titanium 10" woofers with huge voice coils!

I implemented the SPACE settings on the miniDSP yesterday using just IIR filters and it sounds brilliant.

That being said I also bought a Majik 4100 yesterday so will eventually be back to using SO again in a few months (I'm in Melbourne, amp is in the UK so I have to wait for my dear mother to come over at Christmas with an amp stuffed in her suitcase!)

Hi

The latency is quite easy to measure on a 2 channel 'scope (start of at low frequency, then x 10, then x10, etc, to zoom in) and in addition, I just bought one of these to use as a sig gen: http://www.ebay.co.uk/itm/252384893692 (the lowest frequency my existing sig gen can put out is 2 GHz, so not much use for audio work)! Wink

I also bought their USB microphone to see what REW claims the delay to be when measured acoustically. I intend measuring the phase tracking directly (at the amp output; easy as I run my sub with the amp module outside it and the 350's module can be swung open to access the amp output connections) but it will also be good fun to also see what an acoustical measurement claims is going on.

Great to hear the IIR SO worked and yes, when SO is set up it does sound amazing. I have often let folks hear my system with SO set, then switched it off and watched their jaw almost hit the floor (with comments such as 'wow, the music has stopped and it now sounds more like a faulty old motorcar engine').

Shame about the wait for the 4100, but Xmas is not too far away. Many years ago, I bought a 18.5 kg (about 41 lbs) short wave transceiver when visiting the Dayton amateur radio convention in the USA and I managed (just) to cart it home to Scotland, disguised as hand luggage (trudging through various interconnecting airports, the weight of the bag felt like it was just about to dislocate my shoulder) and I nonchalantly strolled past UK customs as though the bag was empty; at least with it being a SMPS powered unit, the 4100 is significantly lighter than that transmitter (with it's big iron transformer inside it).

Bri Smile

KDS/1 (music) + ADSM (AV) -> KK/1 -> 350A + miniDSP time & phase aligned 345 rear sub
KDS Renew -> Homebrew fixed attenuator -> 2250/D -> 212 and Sizmik front sub (bedroom)
MDSI -> 104C (awaiting installation in my kitchen)
MDSI -> Shahinian Arc (installed at my mum's house)
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