Subjective evaluation of one of Don Barringer’s ASP mods

I’ve spent some time listening to Don Barringer’s change to the midrange low pass filter (3.3.1.SN). The effect is both very subtle and very worthwhile. I may try the other filters, but I reverted to 3.2.1 after trying 3.3.1 so this isn’t a high priority.

Since I can do immediate AB comparisons, I was able to discover if the differences are noticeable when switching back and forth. They are. And they can be heard simply by listening to the new filter after one learns what to listen for.

My impressions of the new filter’s effects while listening to rock and jazz are:

  • no artificial strain in vocals (opera is still pending…)
  • treble that seemed to be forward of the rest of the soundstage has moved back, especially at the side of the soundstage near the speakers
  • lower midrange warmth appears to have increased
  • FWIW, changes can be heard in tape and mic preamp noise

An odd thing is that no differences can be heard on Miles Davis’ Relaxin’. This recording can be kind of “in your face” at times, and so it remains.

There’s something slightly strange happening now that this strain is gone, a subtle new issue. Perhaps another of Don’s filter changes will fix it? I’ll post something about this when I can put my finger on it.

Local Orion fans are welcome to come by and hear the differences for themselves. I will probably make this permanent in the next month or so, so don’t wait too long.

For those interested in making Don’s changes but don’t want to invest in the necessary tools and/or build the resistor/trimpot gizmos, you could order custom resistors from Texas Components. They supply trimmed high precision Vishay resistors for $5-$10 last time I got a quote from them.

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Remote control for everything

Ever since building the LCDuino-1 remote controlled passive preamp, I’ve wanted to control some filter parameters in the Orion ASP via remote too. Specifically, I want to be able to change a capacitor (C7) on the fly to alter a bass shelving filter as benefits (or not) each particular recording, and I want to remotely switch the subwoofer circuitry in/out of the signal path. I also want to keep an equalizer in the system, but with it bypassed most of the time, controlled by the remote. (I use a noisy cheapo equalizer to doctor particularly bad recordings.)

After working with the LCDuino-1 code for a while, I concluded that I’d have to build my own device(s) to accomplish what I wanted. Progress has been slow over the last year, but a base control unit (aka “interchange”), a battery operated remote, and auxiliary boxes for AB switching and sound processor inserts now exist. I took some of this work to the Burning Amp festival in San Francisco last fall. This post commemorates installing the first relays into the Orion ASP and having them controlled by the interchange and remote.

The interchange runs off a wall wart, the remote has a 5V portable USB battery meant for extended cell phone power. The two units communicate via XBee radio tranceivers. Each has an Arduino microcontroller board running code I wrote and an LCD display. Ethernet cabling connects the relays, buttons, LEDs, and so forth in the auxiliary boxes and the Orion ASP to the interchange. The interchange basically just flips relays upon command from the remote or from buttons in each box.

With enough relays, the system could be used to compare amplifiers and/or different ASP builds by switching their inputs, outputs, or both, or to remotely change resistance and/or capacitance values in filters using relay-controlled decade-type boxes.

In addition to all this flexibility and convenience, the interchange and remote are programmed to support blind ABX testing so alternate circuits, components, or even cabling can be tested for audible differences.

Don Barringer wrote an epic post on the Orion forum last December explaining the changes he made to version 3.3.1 of the Orion ASP to achieve, as he puts it, “subjective neutrality”. Since I reverted back to 3.2.1 after implementing and not liking 3.3.1 last year, I’m only interested in trying a few of his changes.

I implemented Don’s change #4. It lowers the midrange driver low pass filter cutoff from 1440Hz to 1357Hz. I believe Don’s intent was to reduce the midrange response ever so slightly in the octave or so immediately below the crossover point, as well as through the crossover region to the tweeter. I installed four DPDT relays in the ASP to switch the eight resistors R44-R47 between the 3.2.1 values (2.37k) and Don’s new values, 2.51k.

The interchange works, and the new filter response seems to work for me too. Enjoy the photo mosaic that follows.

mosaic (hi rez)

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Tinkerer’s Rules

I saw this the other day and thought I should pass it on.

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Jim Hall – Concierto

One great jazz album is Concierto by Jim Hall. It was recorded in 1975 and released on CTI. Paul Desmond, Chet Baker, Rolland Hanna, Ron Carter, and Steve Gadd put in beautiful, driving performances. Side 2 is a single cut that may be familiar: Rodrigo’s Concierto de Aranjuez, arranged here by Don Sebesky. Everyone should have a copy. This is a decent review.

I have five copies. And all five sound like different mixes to me. Instrument placement, balance, spread, and reverb all differ. Here are the different characteristics of the mixes of the song Two’s Blues:

Without a doubt, the Legacy CD is a different mix than the rest: Chet Baker’s trumpet is totally isolated from the other instruments, way out to the right. It sounds real. It also sounds like there is a lot of reverb on it. The cymbals have extra high frequency shimmering unlike the other copies where the cymbals have a more bell-like tone. The snares on the snare drum are prominent and sound like they echo too. More reverb again? Jim Hall’s guitar amp has more tube overdrive-type distortion. I think this is my favorite version, even if these things are synthetic and engineered into the remix. The original LP is my second choice.

The Legacy CD is out of print, but Amazon has a 2008 CD from SBME Special Markets. If this is a budget-priced reissue of the Legacy, I’d grab it if I were you.

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Subwoofer EQ

A friend and I thoroughly and painstakingly auditioned various Emotiva multi-channel amps several years ago for our Orions. My reason for selecting the combination we ended up with was that the bass had a cleaner and more discrete character than with any other amp I’d had on the woofers. Textures and subtle amplitude envelopes are heard riding on the fundamentals of many bass instruments that otherwise weren’t heard before.

I’ve been speculating that this particular amp has lower harmonic distortion at the bottom end than other amps, leaving the harmonics on low bass notes relatively unmolested. This is unproven.

I read about Room EQ Wizard (REW) again yesterday, something I hadn’t looked at in several years. I have a Behringer DSP1124, the BFD “feedback destroyer”, which is a very cheap digital parametric stereo EQ with 12 bands that is popular with the home theater enthusiasts for equalizing subwoofers. I hooked up my modern laptop with a modern OS and a stable EMU 0404 USB soundcard to a cheap measurement mic and my Benchmark DAC. After installing REW, I was measuring away in just a few minutes. REW output signals went from the laptop to the Benchmark, through the system and out the speakers. The input from the mic went through the EMU and back into the laptop. This was really nice experience, unlike the old days of endless hassles with incompatible drivers and software and electronics.

After EQ’ing the sub conservatively, it sounds like there is a little less bass. There are four bands of equalization, a 1/2 octave band at 20Hz boosting about 4db, and three 1/6 octave bands cutting 3-4db at 35Hz and in the crossover region above 50Hz. The cut at 35Hz is probably responsible for the sense of less bass, as this is where “rumble” and “thump” is. (See the bottom right corner of this wonderful interactive chart.)

The subwoofer sounded fine with the EQ, but it lost a good degree of impact on good drum recordings and that discrete character that was so hard won by amp selection was gone. Maybe something good will come to light with further listening but for now it seems that the quality is better without EQ.

Perhaps the problem is group delay introduced by the equalizer, and not harmonic distortion after all. The BFD is not a very transparent unit, but one wouldn’t expect much grunge added to the deep bass from opamp noise and artifacts from the roundtrip A/D and D/A conversions it does.

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Ton Koopman and the San Francisco Symphony Orchestra at Flint Center

We attended a concert of the San Francisco Symphony Orchestra guest conducted by Ton Koopman at the Flint Center at De Anza college in Cupertino a few weeks ago. This was the first time we have been in this hall. The program included Bach, Haydn, CPE Bach, and Schubert.

The hall was much larger than expected. Seating 2,500 people, it is 25% larger than Davies Hall in San Francisco. During the pre-concert lecture, a distinct low frequency echo could be heard from the back of the hall. This wasn’t noticeable during the performance.

Each piece was performed with a different configuration of the orchestra, but in all cases, we heard a small chamber orchestra. Our seats were good, but the sound seemed muted. It was clear and balanced, but something elusive always seemed to be missing. I couldn’t get a handle on what this problem was. The SPL never got above 85dbC. The area behind and above the stage was filled in with white-painted plywood panels, and the proscenium arch seemed designed to project the orchestra’s sound back down to the orchestra instead of out towards the audience.

In spite of the sound, we enjoyed the performances and the music.

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Linkwitz on developing 3.0 and 3.2

Siegfried publicly announced the details of the change from Orion+ (2.0) to Revision 3.0 at the end of July. By mid September, he released the details for 3.2 and then posted a minor change affecting the bass response in October, leaving us at 3.2.1.

At the Burning Amp Festival in San Francisco on October 30, 2010, I was surprised and gratified to learn that I had had some effect on this step in the evolution of the Orions. During his presentation there, Siegfried said that several people had “approved” 3.0 before he made it public, and that “some people” weren’t happy with the results, causing him to continue development until 3.2 was done. He gave me a shout out as someone who thought 3.0 wasn’t quite right.

I mentioned my surprise about this to Siegfried’s wife Eike after the talk and she confirmed that I was the only holdout. The weeks between 3.0 and 3.2 were a time of great difficulty for me, since my Orions never sounded right as I struggled between tuning the levels to get the proper harmonic structure by balancing the levels of the drivers’ ranges, changing the filters many times based on Siegfried’s and Don Lancaster’s Barringer’s interim recommendations, and also throwing a few of my own experiments into the mix.

Eike made an audio recording of Siegfried’s talk which is available as an mp3 file from his website. The recording is an hour and a half long.

Here is a transcription of part of his talk starting at 41:39 in the recording:

So we played around with this, this turned out to be version 2 [referring to a label on a graph] and since all this stuff that I’m doing is DIY so people are out there, I said “Okay” and we came up with this equalization, and people built it and so we were pretty excited.

And then some people in here, I think some are in the audience here…yes, there’s someone [SL looks around for me, I wave, he waves back], Eric out there said, “This is not [laughs], this is not right!”  [laughs] He gave it one of these. [Siegfried pantomimes my disapproval]

As a matter of fact before we even published it on the web I asked several people, to say, “Try this out, to see what you think.” You know, there were reports came back positive. His didn’t come back positive [motions to me, laughs] but by that time I think we had it already on the web site, and so we said, we better do some more working on there.

And so we continue working, and then the next version was this one, the straight line. I thought it worked pretty good, but Don had problems here at the low end…

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Orions verified by live music once again

We attended a concert by Hélène Grimaud and the San Francisco Symphony Orchestra at Davies Hall this afternoon, Kirill Karabits conducting.

About the sound: 100dB peaks in the nose-bleed section on Rachmaninoff’s Symphonic Dances. The Schumann piano concerto barely hit 85db. The image and the timbre in the hall sounded like the Orions do on many recordings. Only the immersive quality of the reverberant sound is missing at home. Nothing else is. The Orions are simply it. QED. Once again.

About the performance: The Schumann piano concerto lacked fire, maybe because the orchestra was pared down to about 30 players. The Symphonic Dances, with full orchestra and six percussionists, was only a bit less cool. I think the guest conductor held the orchestra back. The short piece by Silvestrov that opened the concert was cool too. But that was as it should have been.

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Cool blog. Keep it up!

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Why a blog on the Orions? Is this about the Orions anyways?

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