Living Room System

Thursday, August 21, 2014

Review of Acourate

Here's a great review of the Acourate room and speaker correction system.

The review also shows many other things, such as the calibrated mic kit from iSEMCON, calibrated microphones from Cross-Spectrum, and more.

My collection of calibrated microphones is in bad shape.  I have a calibrated mike for LAUD V3, which works only with that program running on a Win 98 PC with Fiji card.  But I'm unsure that the calibration file is properly loaded.  I haven't run the program in years.

I have two Tact RCS 2.0 preamps which both came with calibrated microphones.  I can't remember which microphone went with which preamp, and the Win7 laptop I run the old 2software on makes it unclear whether mic calibration file is loaded or not (the window is blacked out), or which one is loaded (if I could even remember which was which).  Many Tact users decided that the factory calibration wasn't any good anyway, you'd be better off simply using an "average" calibration file for these microphones (similar to ECM8000) to avoid false correction, especially in the highs.

Somewhere I have a Mighty Mike which was never removed from the box the ebay seller shipped it in.

I have an IVIE IE-30 which I haven't used in a long time and needs battery replacement.  It came with an ACO mike in preamp holder.

I have several Bruel and Kjaer microphone capsules with paper curves made in the 1960's.  They must be use with appropriate microphone holder such as the one on the now non-functional IE-30.  B&K also use very unintuitive way of describing the frequency response/polar characteristics of these microphones.

I have several General Radio microphones which came with my GR1933 SPL meter.  These have even more specialized mounting requirements than the B&K's.  I also have some barely working B&K SPL meters.

I have a pile of Behringer ECM8000 microphones which I got in various ways, and I can't remember which is which.

I have Galaxy meter which was tested by Home Theatre Shack and said to be within parameters of their standard Galaxy correction file.

I can never decide whether the time has come to buy M30 or similar serious measurement microphone, though it could be argued I should have done that a decade ago and avoided some of the other things (especially the Ivie, B&K and GR meters).

At this time, I'm not much adjusting anything but bass anyway, so why do I need microphone with 30kHz response?  Though I would like to measure super tweeters anyway.





HDMI De-Embedder

Here is a great discussion on HDMI De-Embedders to extract high resolution audio from DVD-Audio's and SACD's.

As for now, I get full resolution from the SPDIF output of my BDP-95, and I think SPDIF is likely better than HDMI for transmission anyway.*  I am lucky to have BDP-95, one of the few players to do this.  AND my current matrix switch seems to be blocking high resolution audio through the EDID--I could probably change that somehow, and when I next come across the manual for my matrix switch I will try.  Meanwhile I have the recommended Kanex Pro de-embedder installed, and it works for standard resolution audio.  If I could get HDMI to work for high resolution audio, I could use the SPDIF line exclusively for the Mac connection, and then use a superior F connector cable (see previous post).  But my current thinking is that full resolution through SPDIF is likely better than that though HDMI, so I would be disinclined to use the de-embedder for any other reason than convenience.

(*The HDMI is a 100 foot connection using HDMI to CAT6a conversion.  So it's hardly a "simple" connection either.)

RCA? BNC?

For a while I debated about whether to change the connector of my SPDIF line from kitchen to living room that now carries high rez audio from my Mac/Amarra and BDP-95 to the main system.  This line uses all RCA connectors on the cables now.

This line is particularly complicated for other reasons, when connecting to the Mac.   It works, but I now go through two levels of optical/coax conversion.  First, a very fine Inday Toslink splitter splits the Toslink output from the Mac into 4 Toslink outputs.  This Inday active splitter has always worked perfectly, whereas passive splitters never work.  From the split outputs, one goes to kitchen receiver, another goes to a DAC to provide analog to my hard drive recorder.  The third gets converted from Toslink to Coax via another very fine M-Audio CO2 converter.  As I explained previously, this combination of splitting and subsequent conversion to coax requires two levels of optical conversion (or 4 levels if you count both the optical emitters and the receivers).  It also goes through at least one transformer for the coax (in the CO2).

With all that conversion going on, it's a wonder that it works at all, but in fact it has always worked perfectly, as far as I can tell, though I worry about jitter.  What did not work very long was a different converter I got to split one Toslink to two Toslinks and one Coax.  I had lots of problems with that converter, then after I did get it working, it stopped working after one day.  So back to the Inday Toslink splitter, and the two levels of optical conversion, which bother me but always work perfectly.

Well I figured I could optimize this a bit by trying to make the coax connection better.  Currently that is very complicated.  From the CO2 I run a 12 foot budget video cable from spare box (vinyl cable with stranded wire--about the same as Radio Shack's lowest grade AV cable from 2006) to the kitchen connection panel.  There it runs through an RCA to F adapter, into the panel, where it then runs through 50ft of Belden Precision Video cable.  In the panel in the living room, there is a second RCA to F adapter, followed by two short lengths of Monster Video 3 cable joined with an old RCA barrel adapter.  This is what stuff in the real world looks like.

One way to make the connection better would be to eliminate as many RCA connections as possible, particularly the ones that must go through those questionable impedance RCA-to-F adapters.

The original plan for this SPDIF line was that it would only provide data from the Mac.  Then I would simply get a cable with RCA connector on one side (to connect to the CO2 converter coax output) and F connector on the other side (to connect to the F connector on the kitchen patch panel).  In one fell swoop I would be replacing the low grade 12ft video cable, remove one RCA connector, and remove one RCA-to-F adapter which might be even worse than just one RCA connector.

But once I started feeding the SPDIF line from both Mac and Oppo, I needed a connection which would be easy to change.  Screwing and unscrewing F connectors is a big pain.  For awhile, I looked for SPDIF switches, but there's hardly anything like that available and often it is way overcomplicated with re-clockers and the like.  So back to just using the patch panel as a patch panel, and changing the cables to switch the playing device.  So then back to finding a good connection for patching.

On a lark, I looked for a push-on BNC connector.  Sure enough, Neutrik makes a special push-on BNC connector that was intended for patch panels.  It appears that I could special order a cable with this connector on one end through Markertek, as they are a Neutrik dealer.  The I could get (and already did) a BNC to F adapter for my existing patch panel.

That might be an optimal solution, but I wondered if even a push-on BNC might get a bit bothersome after awhile also.  One thing about RCA connectors is that they ARE easy to plug and unplug.

I also realized I was not seeing the big picture.  I could get just as much benefit by replacing the cable in the living room with one having F connector on one end and RCA on the other.  That would also eliminate the need for the F-to-RCA adapter in the living room, as well as the barrel adapter.  And all this business about impedance matching in the coax line is probably insignificant compared with the two levels of Toslink conversion.

So, for now, I've decided to stick with RCA connectors in the kitchen, where I must change the cables often.  I ordered and have now received from Blue Jeans Cable a 10 foot Belden 1505 with RCA on both ends for the Mac-to-Panel connection.  I used that cable to verify that a 10 foot cable would also be correct for the living room, and I will order that second cable with F connector on one end.

I've got a new plan for the Toslink splitting.  I'll use two (now out of production) M-Audio CO2 converters in series connected together with coax.  It's hard to know if that would actually be better than the current setup though.

Friday, August 15, 2014

Multipoint Room Correction

One of the features I want in my next low frequency room correction system is multipoint correction.  That means that a correction will flatten a primary listing position while at the same time not letting secondary listening positions get too far out of whack.  I need that because the quasi-central listening position gets cancellation but much of the room around the boundary gets huge boom from room modes.

DSPeaker Dual Core has this feature.  One thing I don't like about the DSPeaker, however, is that it only has Toslink digital IO.  The Toslink output of my Tact preamp doesn't seem to work (didn't work with Behringer DEQ 2496 when I tried that a few months ago).  So I will need to convert the Coax SPDIF output to Toslink with an adapter.  Then I will need to convert the Toslink output of the DSPeaker into AES for input to the Behringer DCX 2496 which I may still need for crossover and time delay functions.  I might be able to use the analog output of the DSPeaker if I can program in correct inter channel delay and crossover, and it looks like I might be able to do.

Here is the manual for the DSPeaker Dual Core.

On the other hand, AcourateDRC does not seem to have multipoint room correction.  I was looking at that alternative, as it can run on the MiniDSP OpenDRC-DI, which has AES, SPDIF, and Toslink inputs and outputs (for only $299 w/o software).  MiniDSP claims you can get a license to extract filters from Acourate for only $99 but I have not confirmed that.  It looks like the full version of Acourate is more expensive than that.

Another possibility for the MiniDSP OpenDRC-DI is Dirac.  I haven't yet determined whether it is possible to set an upper frequency limit for the correction by Dirac.

A third possibility for OpenDRC-DI is REW (Room EQ Wizard).



Thursday, August 14, 2014

Switching from Tact to something Else

What's Best Forum addresses the switch from Tact room correction to something else.

A consensus seems to be that room correction is best kept below 250 Hz.  Unfortunately, my earlier Tact 2.0 RCS can only do full range correction.  Later versions of Tact, in a late late update, got a top correction frequency setting.  For the longest time, the designer of Tact maintained that full range correction was essential, so a top frequency setting was not allowed.  That probably doomed the company, which appears to have vaporized (it had a good run for about 10 years).   You could (and I've never bothered to do this) set a correction curve that matched the upper frequency curves of both speakers well enough that there would be little or no correction.  I've never really mastered drawing target curves that well.

That's why I've been using manual room mode correction, for my subwoofer only (except I just last week added a minor notch to the panels).  I'm planning to try the DSPeaker Dual Core correction soon. It apparently has a low top frequency…though it's not clear you can set the correction top frequency.

But even without top frequency for correction, I can fake it by applying correction only to the subwoofer channels (after measurement).  Then whatever correction it might have applied to upper frequencies won't matter much anyway.

Since I upped the bass slightly (reducing the steep notch at 45 Hz) in the last time alignment I have been noticing excess bass boom around the room (but not at listening position).  My plan is to correct both at listening position and at a wall position, so the wall position (with maximum nodes) won't get exaggerated.

Wednesday, August 13, 2014

HDCD described

Here's a good (partial) description of HDCD.

It explains the amplitude processing features:

Peak Extension (up to 6dB of compression, matched by identical expansion during HDCD decoding, as with all other amplitude processing features.)

DSP Gain (+12 to -31.9dB)  If Peak Extension is also used, DSP gain is limited to a maximum of +6dB.

Low Level Extension, in normal and special modes.  Special mode does much more low end compression (raising the lowest amplitudes up to 7.5dB) compared to normal (which raises the lowest levels 4dB).

The post doesn't explain the variable filters, however.

Basically these features let you squeeze about 20bits of resolution/amplitude into 16 bits.

I like HDCD, and HDCD's are some of my best sounding recordings.  It is a bit problematic, however, that without HDCD decoding, what you actually get might have been better without the HDCD (contrary to claims HDCD proponents are always making) because, obviously, you are losing dynamic range if the amplitude processing features are used.

However, the producer might well have chosen to limit dynamic range the same way.  And therein, HDCD offers a quasi dual disc solution.  Non-audiophiles can listen to HDCD undecoded, and get the flatter dynamic range that may be more suitable for casual listening.  Audiophiles can enjoy the full dynamic range with HDCD decoding.

Now that I can play back high resolution files from my hard drive, I'd like to convert HDCD to 20 bits. There are playback software programs (including the standard Windows playback) that will decode, but I'm not aware of any way of saving the decoded data to a new file.



Hi Rez on Oppo BDP-95

I'm very happy I can get 96kHz digital from the SPDIF output of my Oppo BDP-95 playing commercial DVD-Audio discs, like Hotel California and Rumours.  But is it the full 24 bits?  I was thinking I might do some kind of test to figure it out.  Not easy to do for various reasons, especially in the case the output might have 24 bit dither even if not 24 bit information.

Anyway, famous audio reviewer John Gatski has already done the tests.  Not only does the Oppo put out 96kHz, but it's also 24 bit, from the SPDIF output.  He used ATI ASDAC which has bit depth indicator to confirm.  The Oppo BDP-105 does not do this, it dumbs down the SPDIF output to 16/48 like most DVD-Audio players.  So what's with the BDP-95?  I think possibly the DVD-Audio consortium wasn't answering their phone when the BDP-95 was being designed.  But afterwards the RIAA got to them and told them never to do that again.  However even on BDP-105 you can get the full resolution stream from HDMI as well (which doesn't seem to be working in my system, possibly because I have programmed my matrix switch to only allow 2ch audio).

Now even if he used a bit rate meter, it wouldn't prove that the BDP-95 wasn't just dithering to 24 bits. However, if that were true, why didn't Oppo do that in the BDP-105?

So the best information that I have is that I'm getting the highest resolution my system can handle, 24/96, from the SPDIF output on my BDP-95 when I'm playing DVD-Audio.  The best of everything!