FAQs about the LX521 system

GENERAL

Q: Why do your speakers have the name LINKWITZ®?

Q: What is the purpose of a LX521® system?

Q: LX521® is an active speaker. What does that mean?

Q: Is the LX521® a “digital” loudspeaker? 

Q: Is the LX521® available as a complete system, including the amplifiers? 

Q: Is the LX521® available as plug-and-play product only?

Q: What wood choices are available for the cabinets?

Q: What is Panzerholz?

Q: What is a PowerBox?

Q: What is the output frequency range?

Q: What is the speaker’s efficiency?

Q: Are grills available to cover the woofers?

 

DIFFERENT FROM CONVENTIONAL BOX LOUDSPEAKERS

Q: What is the reason for not using a rectangular box for the drivers, as most manufacturers do?

Q: The drivers of LX521® are not mounted into a box, why? What is the advantage of open baffle speakers?

Q: What is the purpose of the “keystone” shape of the top section? 

Q: What is a dipole? 

Q: Are the drivers used different from those found in other loudspeakers? 

 

THE UN-BOOMY DIPOLE BASS

Q: Do I need bass traps?

Q: Why does the dipole bass excite less room nodes that conventional bass speakers?

Q: LX521® doesn´t use bass-reflex technique?

Q: Do I need to add a subwoofer to reproduce the lowest bass frequencies? 

 

LX521® ACTIVE CROSSOVER AND AMPLIFICATION

Q: What is the difference between active analog (ASP) and active digital (DSP) crossovers?

Q: Can I use my own amplifier with LX521®? 

Q: May I use tube amplifiers with LX521®?

Q: Do you use DSP crossover?

Q: Many loudspeaker companies advertise “high quality crossover components” in their speakers. Does the LX521®use such components?

 

LX521® SETUP IN THE ROOM

Q: How do I connect my turntable to a LX521® system?

Q: Should these speakers be positioned away from walls?

Q: Can the top be toed in?

Q: Do I need to sit in the “sweet spot”?

Q: Should I apply “room correction”? 

Q: What speaker cables are used?

Q: How long are the recommended speaker cables?

Q: How do I connect the PowerBoxes to my system – Balanced input cables and SpeakON connectors?

 

 

GENERAL

 

Q: Why do your speakers have the name LINKWITZ®? 

A: Linkwitz is the acoustic designer of these loudspeakers. Siegfried Linkwitz (1935-2018), Electronic Engineer at Hewlett-Packard in Santa Rosa/CA. His name is well known among loudspeaker designers for bringing ground-breaking achievements to the audio world:  The Linkwitz-Riley-Filter, the Linkwitz-Transform, etc.

Furthermore, he developed actively driven open baffle speakers (no box), radiating the sound in an advantageous dipole pattern.

 

Q: What is the purpose of a LX521® system?

A: Siegfried Linkwitz designed these speakers along strict form-follows-fuction rules.
It s purpose is to render a copy of the recorded live-event in your living room.
This means neither adding distortion or “flavour”, nor hiding/masking elements.

We did an audition with a professional guitar player in a domestic environment. This may give you an idea how well LX521® performs: It can play indistinguishably close to the live event.
Are they HERE or are you THERE #2 :   “…eyes closed, the listener in the chair was not able to discriminate between the recording and the live performance…” Scroll all the way down here

 

Q: LX521® is an active speaker. What does that mean?

A: Multiway loudspeakers need crossovers to send only selected frequency ranges to their respective drivers. Low frequencies are directed to the robust woofers, high frequencies are handled by the small tweeters.

Conventional loudspeakers are powered by a single amplifier channel and use built-in passive crossovers for the amplified signal. These are lossy resistor-capacitor-inductor networks with limited capabilities in design.
Due to the components used in the crossover, the amplifier sees a complex load that contains large electrical variations depending on the frequency of the signal. Each amplifier model deals differently with that complex load. This is a key reason for the “house-sound” of some amplifier brands/models.

Active loudspeakers use active electronic crossovers (analog=ASP or digital=DSP) to split up the music signal. Only after this active crossover, the signal is amplified:
Each signal path is amplified by his “own” power amplifier. Each amplifier sees an easy load. Each amplifier can then be tailored to the demand of “its” associated driver.

All LINKWITZ® systems follow the active loudspeaker concept. Siegfried Linkwitz on passive crossovers:

“The only excuse for passive crossovers is their low cost. Their behavior changes with the signal level dependent dynamics of the drivers. They block the power amplifier from taking maximum control over the voice coil motion. They are a waste of time if accuracy of reproduction is the goal.”

 

Q: Is the LX521® a “digital” loudspeaker? 

A: No. LX521® renders whatever you feed into it. It has no “sound signature” that would prefer analog or digital sources. The quality of the recording determines the quality of the reproduction in your living room.

 

Q: Is the LX521® available as a complete system, including the amplifiers? 

A: Yes. When selecting your LX521® system, mark the option in the dropdown menu “PowerBox Set”.

 

Q: Is the LX521® available as plug-and-play product only?

A: For the enthusiastic DIYer, we ship improved comfort kits with hidden cabling in dark anthracite HDF/MDF. This is quite easy to finish with clear dull lacquer.
We are shipping worldwide with UPS or DHL.

 

Q: What wood choices are available for the cabinets?

A: Standard wood type is American Walnut. All cabinets come with fully recessed cables. Our workshop may do your individual wood choice on request (e.g. Oak, IceBirch, Bubinga, Cherry, Wenge, Zebrano and many more). The wood is applied on black HDF or on Panzerholz. Finishes are either dull clear or high gloss piano finish.

 

Q: What is Panzerholz?

A: Panzerholz is used in bullet-proof doors and as bottom plate for race cars. Panzerholz comes with high inner damping properties for vibration. We use it for special editions in top-baffles and bridges., applying a dedicated technique to get beautiful American Walnut veneers attached to Panzerholz. Unfortunately, Panzerholz is more than 10x more expensive than plywood, very labor intensive and tools are worn quickly.

 

Q: What is a PowerBox?

A: PowerBoxes 6pro Ncore precision analog contains the analog active electronic crossover (ASP) and five amplifier channels. So, it contains everything you need between your analog music source and the LX521® speakers.

 

Q: What is the output frequency range?

A: 20-25.000Hz

 

Q: What is the speaker’s efficiency?

A: It is not possible to directly compare the efficiency of an active dipole speaker with that of a passive box type speaker. While the efficiency of the individual drivers in both types of speakers is very similar, the dedicated amplifier in an active speaker can more efficiently power the driver, because there are no passive components between the amplifier and the driver itself. All the power is passed on to the driver, instead of being partially lost in a crossover network.

In a dipole type speaker, the efficiency will drop below that of a bass reflex type speaker, especially at lower frequencies, but this drop is fully considered and compensated for in the ASP. All drivers in LX521® have been designed for high power handling capabilities and can play at very high volumes with low distortion, when driven at the appropriate power levels.

 

Q: Are grills available to cover the woofers?

A: These are generally feasible on request.

 

DIFFERENT FROM CONVENTIONAL BOX LOUDSPEAKERS

Q: What is the reason do not use a rectangular box for the drivers, as most manufacturers do?

A: Many identify box speakers with their “box-sound”. Box speakers have several shortcomings, that must be dealt with to various degrees. Leaving the traditional box speaker (and box-sound) behind, was one of the contributors to the success of LX521®.

 

Q: The drivers of LX521® are not mounted into a box, why? What is the advantage of open baffle speakers?

A: Indeed LX521® comes with minimum amount of structure around the drivers. Every structure has a resonant frequency.
-When a sound starts to be emitted, the structure is loaded with energy, that is taken away from the original signal.
-During the sound emission, cabinet structures emit a distorted version of the sound signal.
-When a sound emission ends, the structure continues to emit its stored energy.
So, the emitted sound does not follow the information in the electric music signal.

This is only one of the typical problems of box speakers.

Siegfried Linkwitz: “Except for omni-directional loudspeakers few are designed with a uniform off-axis response in mind. Electrostatic or magnetic panel loudspeakers meet the polar response requirement at low frequencies but become multi-directional at high frequencies and suffer from insufficient dynamic range. Loudspeakers that use electro-dynamic drivers on an open baffle overcome these shortcomings. Compared to omni-directional loudspeakers such dipolar loudspeakers cause fewer room modes and wall reflections, which helps them in hiding the room at greater listening distances. The absence of an enclosure to retain the rear radiation is a major advantage. It avoids frequency selective and resonant re-radiation of acoustical and mechanical energy that is transmitted into the enclosure walls and not converted into heat. Instead, the rear radiation is productively used to establish the sound field in the room.

The typical box loudspeakers with a vent for low frequency extension suffer from resonant bass, delayed panel radiation and non-uniform polar response to varying degrees, but they can be built to meet the acoustic output volume needs. They are not suited to realize the full imaging and illusion potential that is inherent in stereo, because they create sonic artifacts which are distracting. Many audiophiles listen for the presence or absence of such artifacts and use them as differentiators between loudspeakers.”

 

Q: What is the purpose of the “keystone” shape of the top section? 

A: The “keystone” or “vase” or “futurismo” shape of the top-baffle is the result of a strict form-follows-function design. The interaction of the drivers front and rear side radiation, as well as the interaction among the drive units play a role. The shape was the 21st iteration during the development for a perfect dipole behavior.

 

Q: What is a dipole? 

A: A dipole, in general, is an element with two opposing poles. The term is used for e.g. electromegnetic dipol-antennas or for loudspeakers. The dipole loudspeakers have their (+) pole on the front side of the baffle and their (-) pole on the open rear side of the baffle. A dipole loudspeaker has a charcteristic transmission pattern, that looks like a horizontal figure of eight. The so called dipole “nulls” are areas of minimal radiation,  the “waist” of the horizontal eight. This dipole radiation pattern has proven advantageous for taming early side reflections and for less excitation of room nodes in the lower frequencies (4.8dB advantage). These properties contribute substantially to the unrivaled soundstage presentation.

 

Q: Are the drivers used different from those found in other loudspeakers? 

A: Open baffle speakers, with their inherent sound qualities, require specifications for drivers, that are hard to meet with conventional drive units. Excursion capability, power handling, linearity and low production tolerances are essential. If you are furthermore looking for drivers with distortion levels below human detection threshold, there are very few choices available. The long-stroke woofers have been developed by SEAS with the special requirements of dipole bass in mind. The new LINKWITZ22MG is another dedicated driver for LX521®. Its 2nd and 3rd order harmonic distortion figures are well below human detection threshold. All the drivers are precision manufactured by SEAS of Norway. Other than the tweeters, all the drivers were custom designed for LX521®.

 

 

 

THE UN-BOOMY DIPOLE BASS

Q: Do I need bass traps?

A: No.

 

Q: Why does the dipole bass excite less room nodes that conventional bass speakers?

A: In short, due to its advantageous radiation pattern, loading the room with much less energy. Worst in this respect is the conventional box speaker, cardioid is in-between. Best is the compact dipole.

Siegfried Linkwitz: “The typical box speaker, whether vented, band-passed or closed, is omni-directional at low frequencies and becomes increasingly forward-directional towards higher frequencies. Even when flat on-axis, the total acoustic power radiated into the room drops typically 10 dB (10x) or more between low and high frequencies. The uneven power response and the associated strong excitation of low frequency room modes contributes to the familiar (and often desired) generic box loudspeaker sound. This cannot be the avenue to sound reproduction that is true to the original.

The directional response of the ideal dipole is obtained with open baffle speakers at low frequencies. Note, that to obtain the same on-axis sound pressure level as from a monopole, a dipole needs to radiate only 1/3rd of the monopole’s power into the room. This means 4.8 dB less contribution of the room’s acoustic signature to the perceived sound. It might also mean 4.8 dB less sound for your neighbor, or that much more sound to you…

If the open-baffle speaker is built with conventional cone type dynamic drivers of large excursion capability, then adequate bass output and uniform off-axis radiation are readily obtainable in a package that is more acceptable than a large panel, though not as small as a box speaker… This type of speaker has a much more uniform power response than the typical box speaker. Not only is its bass output in proportion to the music, because room resonance contribution is greatly reduced, but also the character of the bass now sounds more like that from real musical instruments. My hypothesis is that three effects combine to produce the greater bass clarity:
1 – An open baffle, dipole speaker has a figure-of-eight radiation pattern and therefore excites fewer room modes.
2 – Its total radiated power is 4.8 dB less than that of a monopole for the same on-axis SPL. Thus, the strength of the excited modes is less.
3 – A 4.8 dB difference in SPL at low frequencies is quite significant, due to the bunching of the equal loudness contours at low frequencies, and corresponds to a 10 dB difference in loudness at 1 kHz.
Thus, bass reproduced by a dipole would be less masked by the room, since a dipole excites fewer modes, and to a lesser degree, and since the perceived difference between direct sound and room contribution is magnified by a psychoacoustic effect.

The off-axis radiation behavior of a speaker determines the degree to which speaker placement and room acoustics degrade the accuracy of the perceived sound. Worst in this respect is the typical box speaker, followed by the large panel area dipole and the truly omni-directional designs. Least affected is the sound of the open-baffle speaker with piston drivers. “

 

Q: LX521® doesn´t use bass-reflex technique?

A: No. Rather the opposite. No vented/ported bass. Why?

Siegfried Linkwitz: “The typical box loudspeakers with a vent for low frequency extension suffer from resonant bass, delayed panel radiation and non-uniform polar response to varying degrees, but they can be built to meet the acoustic output volume needs.”

 

Q: Do I need to add a subwoofer to reproduce the lowest bass frequencies? 

A: No. If you listen to live recordings of real music. However, to experience synthetic 15Hz tones or other “effects” you might want to add a tactile transducer (floor-shaker).

 

Q: Does the “open baffle’ design provide bass performance comparable with conventional loudspeakers? 

A: No, it is much better!! Much more realistic. Very un-boomy.

 

 

LX521® ACTIVE CROSSOVER AND AMPLIFICATION

Q: What is the difference between active analog (ASP) and active digital (DSP) crossovers?

A: ASP=Analog Signal Processor, DSP=Digital Signal Processor.

The split up of frequencies (crossover duty) can be realized while the signal is
digital (from a hard drive or from a network stream) or
analog (from a turntable, a tape machine or a DAC’s output).

DSPs have a good inter-channel matching and are usually very precise in their calculations. DSP can be realized on (laptop) computers or on dedicated microchips. DSP s are flexible as they can load filters for several loudspeakers. However, after DSP, there are still digital signals, that need to be converted to analog via a multi-channel DAC.

ASPs work entirely in the analog domain. They are tailored to one loudspeaker. Selected components of tightest tolerance allow good inter-channel matching. These components are usually much more expensive, compared to DSP. After an ASP, the signal is still analog. No DAC needed. The entire signal path stays analog.

ASP and DSP, both can result in satisfying music experiences. But, the digital-to-analog conversions (DAC) can make a difference. When listening to a digital stream, the signal must be converted somewhere on the way to the loudspeaker chassis.
-ASP sees a stereo (2-ch) DAC upstream.
-DSP needs a multichannel (8-ch) DAC at its output.

While there are many excellent 2-channel stereo DACs on the market, excellent 8-ch DACs are rare.
If you consider the DAC as very relevant for sound-quality, you may distribute your effort/resources/budget either on 2-ch (by using ASP) or divide it to 8-ch (when using DSP).

Many turntable and tape-machine users are happy to avoid any digital-to-analog conversion in their signal chain. They strictly prefer ASP, as A-D / D-A conversions can only deteriorate signal integrity to varying degrees. Although top-notch DACs are good in preserving the signal, they tend to be expensive, and are usually confined to only 2-channels.

After extensive listening comparison tests with top-notch DACs involved, we found the solution using ASP superior. You´ll hear “through” what you feed into the ASP.

 

Q: Can I use my own amplifier with LX521? 

A: It depends:

-If you own a multichannel amplifier (e.g. ATI 528NC): yes.
Connect the LX521®precisionASP to ATI 528NC by using eight analog XLR cables (microphone cables). The ATI528NC output is connected to the LX521®by eight stereo cables. On amplifier side, use banana plugs. On LX521®side use Neutrik® SpeakOn connectors.

-If you own a powerful stereo amplifier (minimum 50W per channel, voltage gain between 20dB and 32dB), you´d need to add 4* more channels per speaker. Make sure all amplifiers come with identical voltage gain (+/-0,2 dB). This results in a stack of five* stereo amplifiers. Connect the LX521® precisionASP to your eight channels by using eight analog XLR cables (microphone cables). Total channel count 8 vs 10 channels:  If your amplifier cannot drive 2 Ohm loads (the paralleled woofer drivers) , then use one amplifier for each woofer driver (4 Ohms) and use a (splitter cable) betwen ASP woofer outputs and your amplifiers. This increases the total amplified channel count from  8 to 10 channels.

PowerBoxes 6pro Ncore precision analog allow an all-integrated high-end solution. They contain the ASP and 5-channels of tailored Ncore amplification in a slim case. All you need between your analog source and LX521® is one PowerBox per side.
PowerBoxes 6pro Ncore precision analog are part of our reference and demonstration systems on shows and auditions.

*If your 200W amplifier handles 2Ohm loads, only 4 amplifier channels per side needed.

 

Q: May I use tube amplifiers with LX521®?

A: Tube amplifiers are not recommended. They are not suited to drive the highly varying woofer impedance. They might be useable for upper midrange and tweeter, but ALL the different amplifiers must have the same VOLTAGE gain, within a +/-0.2 dB tolerance, for proper balance of acoustic outputs from woofer, midrange and tweeter drivers. This tolerance is difficult to achieve in tube amplifiers because their voltage gain tends to vary with the load impedance of the driver and the selected tap on the output transformer.

 

Q: Do you use DSP?

A: No.

 

Q: Many loudspeaker companies advertise “high quality crossover components” in their speakers. Does the LX521®use such components?

A: No. Since the crossover duties are more efficiently and more accurately handled by the ASP, there is no need for any crossover component between amplifier and driver.

 

 

LX521® SETUP IN THE ROOM

Q: How do I connect my turntable to a LX521® system?

A: Connect your (volume controlled) phono preamp to the PowerBoxes 6pro Ncore precision analog with two XLR cables. The right preamp output goes to the right PowerBox. The left preamp output feeds the left PowerBox. If your preamp output is RCA, use the RCA-to-XLR adaptor cables.

 

Q: Should these speakers be positioned away from walls?

If you position LX521® at the rear or side wall, you will hear good “conventional” speakers.
Once you keep 0,8-1m from the side wall and at least 1m from the rear wall, the “magic” starts to happen. Hear the musicians playing as far as 20ft behind the speakers. The speakers completely disappear from one’s attention.

 

Q: Can the top be toed in?

A: Yes, you may rotate the top section in/out

 

Q: Do I need to sit in the “sweet spot”?

A: LINKWITZ® speakers do have a wide “sweet area”, where the phantom illusion of musicians on stage remains intact, even when you walk around in your room.
Moreover, if the LX521® are positioned in an open passage e.g. between living room and dining room:
-If you are sitting in the living room, the band “plays” in the dining room.
-If you are dining, the band “plays” in the living room.  Here, you are listening to the backside of the speakers (remember their symmetrical radiation pattern).

 

Q: Should I apply “room correction”? 

A: Generally no. Except maybe for some nasty low-frequency room nodes, that are still present after various woofer toe-in/positioning trials. Or when the positioning is restricted due to other factors in your (smaller size) living room. Then you may consider addressing the issue below the rooms Schroeder frequency (e.g. below 200Hz) with a notch filter for the peak. The correction may include Interchannel Phase Alignment.

All other frequencies:  As the LX521® have a “sweet area”, not just a “sweet spot”, every “correction” for one recorded point in your room will affect the frequency response of all other points in the room, including reflected sounds.

Siegfried Linkwitz: “The room is usually considered to be the problem when a loudspeaker does not sound right. Actually, the loudspeaker is the problem, because it illuminates the room unevenly with sound at different frequencies. The room merely talks back and the listener’s brain cannot withdraw attention from it. Room correction will make the loudspeaker sound different, but it cannot fix its off-axis frequency response, which is heard via the room.

…. you will find a lot of theory that you can safely ignore, because your room is most likely not one of those ideal cases that can be described mathematically. No one can tell you the right room proportions, though many have and are trying. Listening rooms in the home are much more difficult to understand and describe than concert halls, because their acoustic size varies from being small compared to a 56 foot wavelength at 20 Hz, to being very large at 10 kHz with 1.3 inch wavelength. Concert halls are acoustically large even at the lowest frequencies and thus easier to analyze and they have been studied extensively. Even so, concert hall design is still a blend of art and science. For your listening/living room design and layout follow the simple guidelines above and forget what you read about 1/3rd rules, costly room treatment products, magic wood blocks, etc. and use appropriate loudspeakers.”

 

Q: What speaker cables are used?

A: We use multicore, professional stage quality cables with OFC copper.
Top-baffle drivers 2,5mm2, for woofers 4.0mm2. See here.

 

Q: How long are the recommended speaker cables?

A: You may keep them as short as 0,8m per side by placing the PowerBoxes just next to the LX521® cabinets. However, these multicore cables are available in 2,5m, 5m, 7,5m or 10m per side.

 

Q: How do I connect the PowerBoxes to my system – Balanced input cables and SpeakON connectors?

A: Connect the analog outputs of your music source (e.g. DAC, preamp) by routing

  • an XLR cable from your right output to the XLR input of the right PowerBox.
  • an XLR cable from your left output to the XLR input of the left PowerBox.

These XLR cables come at various price points. We use professional MOGAMI Gold microphone stage cables.
If your source only offers RCA outputs, you may consider a pair of RCA-to-XLR adaptor cables.

To connect the LX521® cabinet to its PowerBox, use our multicore  easy-1-click SpeakOn cables. The multicore cables are included in the LX521®system bundles.