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   What's new? 


  • 6 October
    Rocky Mountain Audio Fest, Denver, CO, October 2-4
    Time to pack up! - A big THANK YOU to Adam and Brian from Madisound, to John, Olav, Claus and Grete from SEAS for their help in making Room 514 such an attraction. Thank you to Don from TheOrionSpeakers.com for taking over the demo's to give me lunch breaks and to Brian L and Jeff B from the OPLUG for running a Q&A session about DIY construction of speakers. Thank you to my wife Eike who paid attention, support and loving help in many situations, accommodated our visitors and circulated about 600 Show Times Tickets. She also took pictures, more of which are on this page.

  • 29 September 2015
    Rocky Mountain Audio Fest, Denver, CO, October 2-4
    Download the Show Times for LXmini & LX521.4 and a List of demo equipment with prices 
    used in Room 514 by LINKWITZ LAB with Madisound and SEAS.

  • 28 September 2015
    Rocky Mountain Audio Fest, Denver, CO, October 2-4
    If this weekend's demo has you interested in building your own pair of LX521s or LXminis but want to know:
    - how to integrate this into your existing system
    - what is involved in building / what skills are needed
    - how to get started
    - where to get the components you need
    - how to get answers when you run into problems
    - what NOT to do...
    Join us for an informal question-and-answer with several members of the oplug-support.org forum. 
    Learn from those who have "been there - done that".  BrianL
    Saturday, 5 pm to 6 pm, Room 514, LINKWITZ LAB

  • 8 September 2015  
    NOTE - The mailbox at sl@linkwitzlab.com is 100% full. I am trying to resolve that problem. 
    But since all mail has been and is automatically forwarded to slinkwitz@gmail.com, no mail is being lost.

  • 8 September 2015
    www.magicLX521.com - LXmini prototype with 3D-printed woofer basket and top section 


  • 8 September 2015 
    Advertisement by www.magicLX521.com  in: Das Musikmagazin für Ärzte, tonart  3 | 2015 , an insert of the Gerrman Ärzteblatt.

  • 24 August 2015
    Links - Nelson Pass talks about power amplifiers

  • 21 July 2015
    It is not too soon to think about attending an interesting audio event later this year

    - October 2-4, Rocky Mountain Audio Fest, Denver, CO. 
      With support from Madisound and SEAS I plan to demo the LXmini and LX521.4 in Room 514
    using two Emotiva XPA5 amps and a miniDSP 4x10 Hd.

    - October 17th, Burning Amp 2015, Redwood City, CA, diyAudio
      I plan to demo the LXmini and LXstudio with the PowerBox from magicLX521.com
      Dr. Frank Brenner is scheduled to pilot a Lufthansa A380 from Frankfurt to SFO the day before 
      and will be present on his layover day.  

    - November 10-12, Institute of Acoustics - REPRODUCED SOUND 2015, Moreton-In-Marsh, UK.
      I plan to talk about "The Magic in 2-Channel Sound Reproduction - Why is it so rarely heard?"

    - After that, November 23rd, my 80th Birthday, and Thanksgiving with family

  • 8 July 2015
    Links - 24/196 Music Downloads  ... and why they make no sense

  • 5 July 2015
    Links - "The Audio Critic" and Peter Aczel's "Audio Legacy"

  • 9 June 2015

    I just spent several hours listening to the LXmini when driven by the first production sample of the PowerBox from magicLX521. Together with Dr. Frank Brenner, and an Academy Awards nominated audio producer, we three compared the Hypex DSP and UcD amplifier based PowerBox in my listening room to my typical LXmini setup with miniDSP 4x10 Hd and AT1806 amplifiers. I am just astounded how much more is in the LXmini system in terms of low end definition and overall refinement of sound when connected to the PowerBox. We all heard the remarkable ease, openness and neutrality. And I had thought all along that I had a pretty decent setup and that it would be difficult to get even more out of the LXmini! While I can still proudly demo and listen to my LXmini system even with the miniDSP 2x4 and Emotiva amps, it is difficult to forget this comparison session.


  • 8 June 2015
    The Sea Ranch - Here are photos that will bring back memories to some of you from a time when we rented our two cottages, 
    1990 to 2011, and you could audition ORION in one and PLUTO in the other. 

  • 3 June 2015
    LXmini - Wood Artistry builds LXmini

  • 3 June 2015
    Please note that I will be out of email reach from June 12 to July 1 and cannot respond to documentation requests

  • 3 June 2015
    Links - Floyd Toole lectures about Sound Reproduction

  • 1 June 2015
    LX521.4 - The LX521.4 Construction Documentation is now accessible to owners and buyers of LX521 documentation

  • 29 May 2015
    Other designs - Kii Audio THREE cardioid loudspeaker 

  • 21 May 2015
    Links - Do you know your PSA? - Singing the Prostate Cancer Blues - 

  • 20 May 2015
    Other designs - JBL M2 Master Reference Monitor

  • 13 May 2015
    LX521 - Examples of power amplifier IM distortion at 1 W and below

  • 10 May 2015
    Links - DIY power amplifiers with extremely low distortion

  • 6 May 2015
    LXstudio - The LXstudio Construction Plans are now available

  • 28 April 2015
    Links - Mono to Stereo Upmixing

  • 23 April 2015
    Madisound will exhibit the LXmini at AXPONA in Chicago, April 24-26, Room 302

  • 24 February 2015
    Links - WIZARDS OF SOUND - THE NEW YORKER writes about the Meyer Sound Constellation Acoustic System and the San Francisco Symphony SOUND BOX.

  • 23 February 2015
    Other designs - Commercial designs: Fullrange cardioid speaker by Dutch & Dutch

  • 17 February 2015
    Other designs - DIY Designs: Cardioid as sum of monopole and dipole speakers

  • 13 February 2015
    Links - The High Resolution Audibility Test

  • 1 February 2015
    Links - Ken C. Pohlmann, Principles of Digital Audio

  • 1 February 2015
    Links - J. Blauert, Communication Acoustics

  • 15 January 2015
    Links - Experts ask the Experts about Sound Recording and Sound Reproduction
    To me one of the most significant events at the Rocky Mountain Audio Fest 2014 was the "Experts ask the Experts" exchange of viewpoints regarding sound recording and sound reproduction. 

    The discussion was honest and enlightening to both experts and audience. The explanations could help audiophiles to understand some of the limitations involved in recording and reproduction, and to appreciate the work done and to make educated choices. 


  • 8 January 2015
    Stereo Recording & Rendering 101 - Definition of processes

Happy New Year 2015 
to all LINKWITZ LAB speaker builders, past, present and future!

In 2015 I plan to extend the LX speaker family from the analog LX521 and the digital LXmini by adding three new members: LXstudio, LX521.3 and LX521.4. This will provide an upgrade path for LXmini builders to LX521 levels and be a revisit of the LX521 using DSP for equalization and crossovers. 

For the LXstudio I add to the LXmini pair the two open-baffle woofers of the LX521 and use the miniDSP 4x10Hd for xo/eq. A prototype is already running and impresses me with its fast dynamics, 3D rendering and expected extension of bass. The 4-piece system provides greater flexibility in room placement than the LX521.

For the LX521.3 and LX521.4 systems I plan to start out from acoustic measurements again, expecting more options in driver equalization from a DSP unit than was practical with the ASP. The LX521.3 will be a 3-way active system including the existing passive crossover, while the LX521.4 will be a 4-way active system and require an additional pair of power amplifiers.

Those are my plans. Let's hear what materializes. 

Spread the word to your friends: 
Highly realistic 3D sound reproduction from stereo is also possible in their rooms and is within their reach!  
Spread the fun!


  • 14 December 2014
    Links - ECMA-407: A New 3D audio codec implementation up to NHK 22.2 with RVC-CAL

  • 13 December 2014
    Links - SOUND BOX with Meyer Sound Constellation Acoustic System

  • 10 December 2014
    Pluto Ultimate Stereo - All-in-One Reference Quality Omni Speaker System & Wireless 24/96 HD Audio Player
    (Website under construction)

  • 26 November 2014
    A Retrospective - 15 Years of www.linkwitzlab.com

  • 21 November 2014
    Issues in speaker design - Woofer equalization in LXmini

  • 7 November 2014
       Links - Spatial Audio: Reconstructing Reality or Creating Illusion?


  • 27 October 2014 - Rocky Mountain Audio Fest 2014
    Sound demonstrations of the LX521 and LXmini at the ROCKY MOUNTAIN AUDIO FEST in Room 418 alternated between speakers every hour and drew great acclaim for the naturalness of presentations. The speakers generated much interest for the LX521 and LXmini DIY materials and driver kits, which were shown in adjacent Room 417 by Madisound and SEAS.

    The AudioTraveler - RMAF 2014: Madisound and the paradise that awaits

    Enjoy the Music.com - RMAF 2014: Madisound Speaker Components

    We had many visitors come back repeatedly for listening to more music or to bring their friends to share the experience. The LXmini created lots of astonishment and excitement. It put a smile on many a face. The LX521 impressed with resolution and dynamic range from delicate to raw power.

    stereophile - RMAF 2014: Reichert on Sunday

    OPLUG - RMAF 2014 Linkwitz Lab Show Report?

    One of the most significant events at the show was the "Experts ask the Experts" exchange of viewpoints regarding sound recording and sound reproduction. The discussion was honest and enlightening to both experts and audience. It was recorded and I hope it will be published soon and without edits, helping audiophiles to understand the issues, to appreciate the work and to make educated choices. 

    stereophile report: RMAF 2014: Music & Seminars

    - Tsunoda Naotaka, Sony Headphones - Siegfried Linkwitz - Peter Mcgrath, Wilson Audio - Richard Schram, Parasound - Cookie Marenco, Blue Coast Records - Jack Vad, San Francisco Symphony Recordings producer/engineer -


  • 16 October 2014
    HIFI ZINE reports on California Audio Show 2014

    PMCs fight it out with LXminis

  • 14 October 2014
    Links - "A call for an open source loudspeaker project"

  • 2 October 2014
    LX521 - Stereo sound system configuration

  • 30 September 2014
    ROCKY MOUNTAIN AUDIO FEST - "Experts ask the Experts" - This should be an interesting exchange of viewpoints regarding sound recording and sound reproduction

  • 22 September 2014
    LXmini - A reference quality stereo sound system

  • 17 September 2014
    Links - Ecma publishes the world’s first 3D audio standard

  • 3 September 2014
    LXmini - Digital Stereo Sound System

  • 24 August 2014
    ROCKY MOUNTAIN AUDIO FEST - October 10-12, 2014 - Madisound-SEAS-Linkwitz Lab - Room 417 & 418
     Rocky Mountain Audio Fest I will be there with the amazing LX521 and the new LXmini Reference Loudspeakers and demonstrate them in Room 418 each day of the show.
LX521 at 9 am, 11 am, 1 pm, 3 pm, 5 pm
LXmini at 10 am, 12 am, 2 pm, 4 pm

It is time to make your travel arrangements to the Denver Tech Center, if you have not done so already.

The sound you hear in Room 418 should be your reference for the show.

  • 20 August 2014
    Links - ECMA-407, the world’s first 3D audio standard is coming

  • 15 August 2014
    LXmini - Amplifier and Gallery pages added

  • 8 August 2014
    Sound recordings - West Side Story, San Francisco Symphony

  • 26 July 2014
    Links - The Distortion of Sound

  • 14 July 2014
    LXmini - Construction Plans released

  • 9 July 2014
    Links - SOUND AND RECORDING - Applications and Theory, written by Francis Rumsey and Tim McCormick

  • 7 July 2014
    Links - We need to talk about SPEAKERS ...

  • 5 July 2014
    Links - Floyd Toole is "Reflecting on Reflections" in the June 2014 issue of the JAES

  • 3 July 2014
    Links - Berliner Philharmoniker in the Digital Concert Hall - A great musical and visual treasure! 

  • 24 June 2014
    LXmini - A new, small speaker with the promise of producing Reference Quality Sound in any size room

  • 21 May 2014
    Loudspeaker & Room - Test and measurement of loudspeaker and room interaction

  • 21 May 2014
    Sound recordings - Discover Internet Radio broadcasts

  • 28 April 2014
    LX521 - Sound as close to Live - as the Recording provides!
    www.magicLX521 offers the fully assembled and finished LX521 at promotional prices during their Titanium Driver Award campaign. 

  • 8 April 2014
    The Audio Critic - Peter Aczel reviews the LX521 Reference Loudspeaker

  • 1 April 2014
    Ping Tests - WATSON loudspeakers outdoors of SPC

  • 28 March 2014
    Links - Line array dipole for a Concert Hall sound system

  • 26 March 2014
    Links - Fundamentals of sampled signals, DAC's and the reconstruction into analog signals are illustrated in an Agilent Application Note

  • 24 March 2014
    Dipole prototypes - Public Address column loudspeaker 

  • 19 March 2014
    Ping Tests - Experiments to understand what matters to the creation of a 3D auditory phantom scene from two loudspeakers and in different rooms

  • 8 March 2014
    diyAudio - "Extreme Open Baffle Active Speaker inspired by Linkwitz LX521"

  • 23 February 2014
    www.6moons.com - Review of Chinese-built Pluto Ultimate, which is now available from www.plutospeakers.co.uk in the UK 

  • 23 February 2014
    www.hifiwigwam.com - Review of Chinese-built Pluto Ultimate, which is now available from www.plutospeakers.co.uk in the UK

  • 2 February 2014
    LX521 Photos & Comments - Ein Hör-Erlebnis in Stuttgart

  • 16 January 2014
    Links - "SAVE THE STEREO" and "Pure Audio to Health" 

  • 12 January 2014
    About me - "The Titanium Driver Award" from ALMA International

  • 8 January 2014
    Loudspeakers - "Whatever happened to the quality of reproduced sound in the home?"

  • 29 December 2013
    My current setup - Audio/Video in our home on the Pacific Coast

  • 6 December 2013
    NUTSHELL HIGH FIDELITY - A most interesting website

  • 3 December 2013
    Pluto Ultimate - Reviewed by "Hifi Pig"

  • 27 November 2013
    LX521 - Listening room with rear wall reflections

  • 20 November 2013
    ALMA International - 2014 Winter Symposium - I will talk about: "Whatever happened to the quality of reproduced sound in the home?"

  • 17 November 2013
    PLUTO - Photos of Chinese market PLUTO System 

  • 27 October 2013
    Construction Plans for LX521, ORION and PLUTO can be sent as PDF 

  • 23 October 2013
    stereophile completed its report on RMAF-2013. The LX521 was not mentioned, though the reporter assigned to the floor was in our room, listened to his CDs, took notes and visibly enjoyed what he heard. I must assume that stereophile did not consider the LX521 to be of interest or educational value to their readership. Frequency independent directivity for minimum perceptual interaction with the room is found in hardly any commercial loudspeaker design, as can be seen in the photos from the show. Our demo gave immediately recognizable proof of its benefits. The LX521 sends a message to the loudspeaker industry, a message that would be inconvenient to stereophile's top advertisers.  
    If there were fewer visitors to RMAF, we would not have known. Our room was packed almost all the time and many music lovers returned for more, enjoying the clarity, timbre, dynamics and spatial rendering, and thus the believability of the auditory illusion.

    ULTRA HIGH-END surprisingly includes the LX521 in its coverage of RMAF. The reviewer apparently failed to recognize the significance of the design in comparison to every other loudspeaker at the show. Our emptied out hotel bedroom had no acoustic treatment. But what is "ultra high-end" all about? In this category of audio the price of the equipment usually far exceeds any realistic gain in performance. Who is the audience? I want to satisfy individuals who are still familiar with live (unamplified) sounds in a performance space, or who play an instrument, or make recordings. It ought to and can be done in such a way, that many can afford the pleasure of hearing great recordings convincingly rendered in a normal living room. 

    Confessions of a Part-Time AUDIOPHILE gives an informative report. But the quoted prices are per pair, not per side, and so the total for a Madisound supplied LX521 Kit plus the prerequisite Linkwitz Lab Construction Plans comes to around $3200. Handout
  • 20 October 2013
    Assemblies - A listing of sources for full assemblies and subassemblies of LX521, ORION and PLUTO loudspeakers

  • 16 October 2013
    Links - International Conference on Spatial Audio

  • 15 October 2013
    Rocky Mountain Audio Fest - 2013, Oct. 11-13  -------  Handout 
    I gave 10 minute talks about  *** Stereo is a Magic Trick ***  in room 418 
    Friday: 2 pm, 5 pm and Saturday: 11 am, 2 pm, 5 pm and Sunday: 11 am, 2 pm
RMAF brought over 400 visitors to our room giving them an auditory experience and appreciation of stereo they never could have had before the advent of the LX521. I surprised myself several times about the speaker's bass output capabilities when hearing new material that visitors brought. We shocked more than one well known loudspeaker designer by the transparency, clarity and dynamics of close to live-like sounds produced by these speakers, and by the believability of an auditory scene devoid of loudspeakers. It was a most enjoyable magic trick, people got lost in the music and many listeners came back to our room for more. As one person wrote to me afterwards: "Your room at the show was 'Hotel California' - the room where people kept entering but never left."

The speakers were assembled from a Madisound flat-pack of wood parts. We used the Madisound assembled and tested ASP. The 12 drivers are all SEAS designs and Olav Arntzen, R&D manager at the time, was more than pleased to hear what his products allowed me to develop. John Stone, US representative of SEAS, played an important role by leaning on R&D for accomplishing certain driver modifications that were needed in open baffle applications.

We used a BelCanto (CD2) CD player with built-in preamp and volume control to drive the ASP. Connected to it were two Emotiva (XPA-5) 5-channel amps with 200W/channel output, driving bottom and top woofers separately, midranges and tweeters with 4 channels per side.

  • 15 October 2013
    Videos taken by Linear Integrated Systems at the Burning Amp Festival - 2013 (The audio is severely clipped in my talk) 
    stereophile reports a slow burn at 12 noon, but attendance was merely 10% down by the end of the day compared to last year.


        From left, Juha Backmann (Nokia) thanks the invited speakers: 
        Axel Grell (Sennheiser), Siegfried Linkwitz, and Ilpo Martikainen (Genelec)

  • 1 August 2013
    AES 51st Conference - "Loudspeakers and Headphones", Helsinki, Finland, 21-24 August, 2013

  • 27 July 2013
    LX521 Supplies - What do you need?

  • 27 July 2013
    PLUTO-2.1 System - It will be announced to Chinese audiophiles on 28 July 2013 by HIFIDIY.NET 
    with Pluto advertisement at http://bbs.hifidiy.net/forum.php and home page www.linkwitzworks.com

  • 23 July 2013
    LX521 Supplies - Assembled DSP and LX521 Configuration File

  • 3 July 2013
    Home - From where and in what numbers do visitors come to this website? 

  • 1 July 2013
    LX521 Description - An updated spreadsheet to find the optimum toe-in angle and an analysis of reflection delay and attenuation for dipole and monopole sources in different size rooms

  • 1 July 2013
    Stereo Recording and Rendering - Sound Field Control for Rendering Stereo - 1

  • 29 June 2013
    Audio production - An interview with Keith O. Johnson of Reference Recordings

  • 29 June 2013
    LX521 DSP challenge - A complete DSP solution with digital and analog interfaces

  • 26 June 2013
    LX521 Description - A spreadsheet to find the optimum toe-in angle and an analysis of reflection delay

  • 25 June 2013
    LX521 DSP challenge - Digital Crossover/EQ with Open-Source Software: HOWTO

  • 25 June 2013
    Links - Introduction to Sound Recording

  • 22 June 2013
    LX521 Photos - Different implementations of the speakers

  • 16 June 2013
    Recording and Rendering - Sound Field Control for Rendering Stereo - 2

  • 14 June 2013
    LX521 Supplies - Madisound now offers the assembled and tested Analog Signal Processor

  • 7 June 2013
    LX521 Description - The Listening Room

  • 5 June 2013
    Other designs - Dipole polar response. Synergy Horn from a distance 

  • 29 May 2013
    Links - Bruno Putzeys on Amplifiers and Class D

  • 26 May 2013
    Links - Boyk on Piano

  • 26 May 2013
    ORION-5 - A source in the UK to hear and buy the complete loudspeaker system 

  • 22 May 2013
    Publications - Papers to be presented at the AES 51st and AES 52nd International Conference

  • 6 May 2013
    LX521 monitor - Madisound now ships Flat Pack Cabinets

  • 4 May 2013
    Issues in speaker design - Further thoughts about "Group delay and transient response"

  • 19 April 2013
    DSP challenge - We have an efficient solution for LX521 stereo setups

  • 13 April 2013
    Audio production - San Francisco Symphony - Channel Classics - McGill University - Pentatone Classics - DGG

  • 8 April 2013
    DSP challenge - updated

  • 7 April 2013
    Links - Linear Audio publications and Jan Didden's personal website

  • 4 April 2013
    DSP challenge - One possible alternative to the LX521 ASP

  • 29 March 2013
    Links - Evaluation of Time-Frequency Analysis Methods and their Practical Application

  • 28 March 2013
    Links - KLIPPEL - Online Training

  • 24 March 2013
    Publications - Updated links

  • 23 March 2013
    LX521 - Assembling Top baffle, Woofer baffle and Bridge

  • 23 March 2013
    LX-521 - Designing a DSP based equalizer/crossover

  • 21 March 2013
    ORION-4 - Reports from AXPONA 2013 in Chicago

  • 10 March 2010
    Design Models - Point dipole and point monopole in a circular baffle

  • 4 March 2013
    Stereo Recording and Rendering - Recording in a virtual acoustic space

  • 25 February 2013
    LX521 supplies - Promotional offer for cabinets from MagicLX521 opening its store

  • 30 January 2013
    Links - MUSIC TO YOUR EARS, a most interesting article in the current issue of THE NEW YORKER

  • 21 January 2013
    LX521 supplies - Cabinet Kit from Germany

  • 15 January 2013
    LX521 monitor - Photos & Comments about the LX521

  • 10 January 2013
    Digital Photo Processes - Five years later

  • 9 January 2013
    ORION challenge - Peter Aczel of The Audio Critic describes 'The Final Mod: Orion 3.3.1SN'

  • 8 January 2013
    LX521 monitor - The first pairs are playing in Germany and USA 

  • 8 January 2013
    Links - Dynamic Space Stereophony

  • 5 January 2013
    Sound Recordings - I added some of my favorite music videos to the list

  • 2 January 2013
    Stereo Recording and Rendering - Subjective evaluation of phantom acoustic scenes

    2012 to 2007


What you hear is not the air pressure variation in itself 
but what has drawn your attention
in the two streams of superimposed air pressure variations at your eardrums

An acoustic event has dimensions of Time, Tone, Loudness and Space
Have they been recorded and rendered sensibly?

Last revised: 10/09/2015   -  © 1999-2014 LINKWITZ LAB, All Rights Reserved