Archive for March, 2010

Review of Audyssey system within the Marantz AV8003

Saturday, March 27th, 2010

Now it is well known I have been highly skeptical of automated room correction and Eq systems.  I did have a demonstration of Audyssey from Kris Kyriakakis of USC.  He was using  SVS MTS-01 speakers to demonstrate Audyssey at SOTU.  In all honesty I was underwhelmed by the demonstration.  I thought the bass was improved, but that overall the sound was worse.  Kris canceled all except low frequency correction and then things were improved.

So after doing a careful manual set up and calibration of my updated rig, and living with it for a few days, I unleashed Audyssey on my very unusual system not expecting it would make any sense of this highly unconventional system.

The most unconventional are the front three, especially the main front left and right speakers.  So it is necessary to give a description of operation.

As many know I’m a full ranger at heart, and regard all crossovers as a necessary evil.  So the concept is to keep the system as close to a full range driver as possible.  In fact there is only one complete electronic crossover in each three fronts.   These are between bass/mids and tweeters. The mains contain independent aperiodic transmission lines.  The center is a single line.

The 7″ drivers in the mid line are allowed to roll off in the bass acoustically.  F3 is 42 Hz, 44Hz for the center.  The bass line has an F3 in the room of 23 Hz.

An active crossover sends the bass and step response correction to the upper of the two 10″ drivers.

The LFE signal is low pass 60 Hz and fourth order roll off.  This signal is sent to the amps powering the lower of the 10″ drivers.  The LFE signal is also sent to mono sum buffer amp and then sent to the amps powering the upper 10″ drivers along with the diffraction compensation signal.  This is to keep the diffraction compensation stereo.  Diffraction compensation is performed by the 10″ driver and not through the 7″ drivers, to off load them and prevent large cone excursions.

There is a low pass crossover that provides diffraction compensation to an amp supplying the upper of the two drivers in the center speaker.  One of the biggest reasons for an active crossover is to have precise control of diffraction compensation which varies greatly with speaker boundaries and room placement.  This is in no way possible with passive crossovers and is a big advance in accurate reproduction.  The design concept minimizes phase shifts and time aberrations due to crossover artifact.

The surrounds are sealed  speakers with Dynaudio drivers with a Fs of around 50 Hz second order roll off.

The rear surrounds are biamped dual transmission lines.

The system is optimally configured with all speakers set to large, and the speaker bass management set to both with the LFE crossover at 60 Hz.

A careful level calibration was done prior to utilizing Audyssey.

So I set up the rather cheap feeling calibration mic in the first position on a tripod.  I plugged the miserable small gauge mic cable into the jack on the front of the AV 8003.  With not much optimism I started the calibration, of the staccato tones played via each speaker in turn and at the end all three fronts.  There were two false attempts from problems such as a noisy fly that got in the room.  However third time lucky.  I measured in six positions.

So then I checked results expecting to see nonsense.  Well I was dumbfounded that it had done the speaker set up as designed.  It did not change any speaker levels from my calibration, and imagine my surprise when I saw it had figured out all speakers should be set to large and the LFE crossover at 60 Hz!  All just as intended.

The only confusion concerned the woofer distance.  It placed the woofer 5 ft behind the mains, and yet they are the same driver.  I thought about this and realized the program has averaged the driver and port arrival times.  This I had to reverse and manually put woofer and main speakers in the same place as there would have been phasing trouble with the upper diver as it is receiving a mix of signals.  It also altered the distances of the other speakers from measured.  However I think this has had a highly beneficial effect on getting a more even result though out the room.

Here are the results of the Audyssey frequency response correction.   In the main except for the surrounds between 1 and 2 kHz the mid band correction was insignificant.

However for all speakers except the rear surrounds there was a first order lift put in place above 8 kHz.  I think this was because in three of the testing positions the microphone was close to the rear surrounds.  There is a fall off of HF with distance and this in my view should not be corrected.  Listening test confirmed this.

The system sounded better with the frequency response correction canceled.

However I was intrigued by this, so I did and experiment purposely introducing a frequency response error.  I boosted the level of the bass amps to the rear backs below 150 Hz by 7db.  I did a run of Audysey and it caught the problem and corrected it.

So in summary I think this program is useful and may well take the edge off loudspeaker errors.  I suspect this is much more a loudspeaker correction program than room correction in a lot of cases.  For instance I know my surrounds have a slight null between 1 and 2 kHz that was identified by Audyssey.

I feel the most useful aspect in my studio was the re timing of the speakers.  I think this made a difference in two areas.  The sound is more uniform over the seating area.

However I think the greatest benefit was the improved sense of space achieved in 7.1 reproduction, especially.  I was definitely hearing different spaces captured.  In essence the reproduction was to a very large extent freed from the boundaries and constraints of the room.

I will make more comments about this when I report on some of the discrete multichannel discs I have listened to.

My biggest issue with the system is what I feel to be inappropriate last top octave equalization.  I would encourage adopters to be alert to this.

My preference would be for Audyssey to only make cuts in the top octave and leave alone any high frequency loss above a first order roll off.

I have to say I was fascinated evaluating this system and regard it as a work in progress.  I think we are early in total system/room Eq and suspect there is still a lot to learn.

Review of the Oppo BD-83 Universal disc player

Friday, March 26th, 2010

Now there are increasing numbers of operas on Blue Ray.  It was time to upgrade the studio to take advantage of the audio and video improvements possible with Blue Ray.

Since the Oppo BD-83 seems to be good enough for Lexicon, I thought it should be good enough for me.

I was not disappointed.  The unit arrived superbly packed and presented.  The unit was in it own carrying case.  Cables were is a nice cardboard box.  A very high quality HDMI cable was included.

The instruction book is published on high grade paper.  English is excellent and idiomatic.  The instructions clear and informative.  In the play list, the illustration is a compilation of Bach preludes, which I thought added a touch of class.

Since I was not planning to use the analog circuits, I selected the standard version, not the SE.

I mounted the unit in my rack

Connections  were straight forward.  One two pin power plug, one Ethernet cable, and one HDMI cable.

Audio and video set up using their wizard could not have been simpler or more straight forward.

No problem was encountered watching high def audio and video program right away.  DVD performance was good also.  I have a had a couple of CDs the unit does not like and the other players will.  I don’t know what it is about CDs, but they seem more fussy than other digital disc mediums.  I know if you have a large collection you need more than one player and probably three!  I have a choice of four drives in the system!

The unit seems to make no appreciable heat.  There is a fan on the back, but I don’t think it has started.

This unit is phenomenal value for money and highly recommended.

The unit was purchased from the Audioholics store. The staff was professional and courteous throughout the transaction.

Review of the Marantz AV 8003 tuner pre/pro

Friday, March 26th, 2010

It was time to change my Rotel 1098 for something more up to date.  The Rotel unit, now four years old, had no HDMI facilities, and of course did not contain the new loss less codecs.  Also even after to going to a lot of trouble, it was impossible to make the unit totally impervious to RF interference from SCR light dimmers.  So on deciding to add Blue Ray, as there are increasing number of opera BD disc it was time for a change.

I decided on the Marantz AV8003, because it had the corps functions I wanted, especially a Neural 6 decoder, as MPR are now broadcasting the live Friday night Minnesota Orchestra broadcasts in 5-2-5 neural six.  Also the signal to noise ratio was excellent at 105 db.

I did do some measurements on the unit.

In pure direct mode, at 1 Volt output I measured the signal to noise at 106.2 db A unweighted.  I should stress this is at the limit or beyond of my older test gear.  However I think it shows that his unit is superior in the regard.

The unit has a clipping indicator for the analog inputs.  I had to use the 6 Volt out terminals of my Quad 44 preamp and crank it to get the indicator to light!

So I measured the head room.  This is a really important aspect of audio gear, and not enough attention paid to it.  The specs for the line inputs are 400 mv for I volt out at the unbalanced outputs and 2 volts out at the balanced outputs.

It took 15 volts in the clip the line in preamp and 14 volts out from the unbalanced connector before distortion was evidentb on the scope.  This is a very superior performance.

The order of the low pass LFE crossover is not stated.  The low pass crossover is fourth order.  I did not measure the high pass crossovers since I don’t use them.  My system requires the low pass crossover to be set to 60 Hz.  At 60 Hz the LFE output is 6 db down compared to a reference signal at 30 Hz.  At 120 Hz it is 30 db down.  I have not idea why manufacturers choose to hide such vital information from the prospective user.  That is irritating to say the least.

The unit is impervious to SCR noise, and is exceptionally quiet in use.

The unit is well constructed.  I did not remove the case, so as not to void the three year warranty.  However a large toroidal power transformer is visible.  The boards are stacked in logical fashion close to the inputs and outputs.  There appears to be no crowding, and I would think service would not be a nightmare.

Installation: –

I purchased the optional rack mounting brackets, which gave me one of those “what do I do now moments,” at the start of installation.

The standard practice for 19″ rack mounted equipment is to mount from the front.  The front mounting is 19″, but the space through which the equipment goes is 17.5″.  Now the main body of the case will fit the 17.5″ width.  However the case bells out at the front because of the fascia, and the brackets bell out as well, so it will not go all the way in.  So the unit has to be mounted from the back instead of the front.  Now the mounting brackets were slightly too wide to go into my rack from the back.  I think it would have gone if the rack had been fabricated of steel.  However because if humidity/rust issues I fabricated the racks from aluminum, which requires a greater thickness of metal.  So I had to take off exactly 3/32″ from each bracket with a JET band saw in my shop.

Fortunately the inside width of the mounting brackets when mounted is 17.5″, and the inside rack spacing of my racks is precisely 17.5″.  So I was able to make a cosmetically acceptable job of the installation.  As you can see, because of the need for rear mounting the inside metal edge of the rack is exposed, which it would not be with the usual front mounting.

Here is a frontal view of the mounting.

Set up: –

I took the opportunity to fully revise the some aspects of the installation as the LFE crossover is different.  I revised the active crossovers that send the the low pass output to the upper 10″ driver in the large bass lines, to improve the diffraction compensation to the 7″ drivers in the bass mid line.  The SEAS ecal drivers are a challenge to say the least.  I modified the crossovers to better compensate for the rising response of those drivers above 200 Hz.

The unbalanced LFE output goes to the lower 10″ driver.  I added an ATI L200 buffer amp, replacing my buffer amp to send the LFE signal to the upper 10″ driver also.  This requires a mono sum buffer amp, as the diffraction signal has to be stereo and the LFE is mono.  Without buffering the diffraction compensation would be mono.  The ATI L200 was connected to the balanced LFE output of the AV 8003.

Other connections were quick and straightforward, as I can get behind my equipment in the studio mechanical chase.

Doing Audio, speaker, input and video set up was quick and straight forward.

I should add that the instruction manual is poorly written, sufficiently poor that it would give the novice a lot of difficulty.  There is a lot of “Pigeon English” in the manual which is unacceptable in a unit of this quality and price.

Functionality is good.  You can can use digital and analog inputs of the same label.   If a digital signal is resented it will use that.  If an analog one is presented it will use that.  No need to go back to the menu.  That is a nice touch.

As far as recording, only an analog input selected is presented at the analog tape out.  So you can not record from the analog outs and listen and or watch something else.  That is inconvenient.  The Rotel had this covered.

I did a vet careful manual set up, before experimenting with Audyssey.  My review of Audyssey is a separate review.

The unit is easy to use.  There is a left control knob for changing inputs.  I use this the most, as you need to be at the equipment to switch units.  It is faster than using the remote.  The right knob is for volume.  The knobs are on plastic shafts and have a little wobble.  I think this was done to stop static on the fingers transmitting to the electronics and cause failure and damage.  With the Rotel, it would lock up if you touched a knob without discharging yourself first.  This unit does not require you discharge yourself.  The rack mounting by the way securely bonds the unit to the robust studio star cluster ground plane.  The power cord is two pin with no grounding prong.

There is a pull down panel to get to the other front panel controls.  The most frequently used front panel controls are the button to select the7.1 channel analog inputs, and the selector for direct and pure direct modes.  The Direct mode, by passes everything except volume, and the pure direct in addition switches off the video circuits.

Audio modes such as Dolby Plx stereo etc are best switched from the remote.  They can be changed quickly on the fly.

I have not got into file sharing yet, but I might.  I have no difficulty sending any audio file from a file my audio workstation via its RME Fireface 800, in SPDIF digital or analog.

Performance in use: –

So far the unit has performed flawlessly.  Both sound and video are beyond reproach.  In pure direct it is literally a wire with gain.

I did not have much expectation that the FM tuner would be of high caliber.  However I was wrong.  It is a first class FM tuner.  It is every bit the equal of my quad FM 4 which I hold in high regard, as do numerous others.  The unit also comes with the iBuquity HD radio system.  This unit did not endear me to that system any more than the little Sony unit I bought to evaluate that system.  An analog FM is significantly better in all aspects except dynamic range.

The only issue I have is this.   I have found is that it decodes SACD discs incorrectly from PCM via HDMI.  The rear channels in SACD should go to the center backs.  The Marantz sends them to the surrounds, which is not what should happen at all.  So I’m glad I kept my Marantz player in the rack, as I have to still use the external analog inputs for five channel SACD.

I have reviewed this recently and find that the speaker and monitoring arrangements for SACD in the US and Europe are different.  Since all my SACDS are from Europe, I have to use the 7.1 analog inputs for SACD playback.

The unit has a power draw of 60 watts and makes significant heat.  This further reinforces my view that complex processors like this should not be in the same case as power amplifiers.

So I have to say that I would recommend this unit who has need of a pre/pro for AV.

I purchased the unit from my local dealer Hi-Fi sound of Minneapolis.  I have had good relationship with them for over a quarter century.  They gave me a discount.  I purchased the unit with mounting brackets for a little over $2300.  I could not be more pleased.

Review of ATI L200 Buffer Amp

Friday, March 26th, 2010

Review of ATI Stereo line buffer amp

Pros : Compact, Versatile, Excellent Sound, Accurate Controls
Cons : Turn off thump a problem, Low output impedance
Best Uses : Blending buffer amp, Mono summing amp, Variable gain voltage amp

The ATI L200 is a useful device.

Its main uses will be to buffer blended signals.

To place a mono signal in two independent outputs.

For use as a positive or negative gain stereo or mono voltage amplifier.

The L200 has two xlr balanced inputs and two balanced outputs.

It can provide up to 28 db of gain down to zero output.

Input impedance is 40 Kohm and output impedance 40 ohms which presented a problem that I had to solve.

The unit comes with a 24 volt DC power supply. There is a 24 volt DC output that can power another unit.  Be careful if you do, the outside of the DC plug is hot!

I used my unit as part of my triamped dual aperiodically damped transmission line monitor speakers.  These are a novel design of mine and are truly full range.

However the LFE signal which is mono needs blending with the signal from the low pass active filters which are stereo.

So I took the balanced LFE out from my Marantz AV 8003 pre/pro, to the left balanced input of the L200.  I opened the unit up and moved the link to the mono sum position.  Then I could blend the LFE output with the low pass outputs of the active crossovers from the two L200 outputs

However the low 40 ohm Zs output impedance drastically dropped the output from the low pass crossovers.  So I had to modify the unit to increase the output impedance.

One other problem, when power is cut to the unit a large spike appears at input and output.  The unit sent my Marantz into reset.  So I have left the unit permanently on.  The unit contains no on/off switch.

All in all the unit is nicely made, has excellent signal to noise in all modes except maximal gain where it is noisy.  It would be better if it did not have a huge turn off thump, and had provision for a higher impedance output when used as a combining buffer amp.

However when all is said and done this is a useful unit, but for the price could be improved.