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Interviewing Bill Dudleston of Legacy Audio on Legacy Audio Valor speaker system and Wavelet DAC/Preamp/Crossover

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The appearance of the Valor Speaker System as a new flagship product for Legacy was especially exciting for me as it incorporated some new design elements that Bill Dudleston had been working on for some time. This was the first time a multi-driver concentric design had been released by Legacy Audio. As Bill is widely recognized as an authority on speaker design, room equalization, recording and active speaker systems, I thought this afforded the perfect opportunity to have him discuss the principles behind the design of the Valor.

Bill is both thorough and understandable; he is able to discuss theory and design in such a way that end users can grasp the principles he employs. The shift from a quasi-line source array for the primary driver to the concentric driver is not subtle, and it deserves introduction. I am happy to present to the Dagogo readership the discussion that Bill and I had ahead of the review.
Question: The Valor is a stunning achievement. I am shocked at the disparity in performance between it and the previous flagship, the V Speaker System. What drives you to continue the upward march to ever greater flagship speakers?

Answer: The end game is restoring the elements of stereo playback sequentially back to the vectors that were originally present at the recording event. Better directivity control for the early signal, cancel reflections from near room boundaries and present the ambient information at appropriate time and levels.

Q: How was the name Valor chosen for this speaker? What do you wish to emphasize about the speaker and Legacy Audio by naming the flagship speaker Valor?

A: For me, it’s about remaining undaunted in a sincere quest for restoring naturalness.  As a pioneering company, we don’t wait for what we know to be correct to become accepted generally by mainstream audio.

Q: Let’s begin with the Wavelet. Have there been any significant changes to the operation of the Wavelet since the release of the V Speaker System two years ago? If so, what changes have occurred?

A: No hardware changes yet. Our assembly methods have certainly improved as has the internal harness connections. The remote software is continually refined and, being web based, it requires no updates by the user. We have added features for Home Theater inputs and the punch setting and brilliance were latter additions.

Q: What frequencies are being controlled by the “Punch” setting? Are these frequencies also being adjusted in level, and if so, by how many dB?

A: The punch adjustment is centered at 50Hz and can be increased a maximum of 6dB, or trimmed down 10dB.

Q: The description of the internal DAC for the Wavelet states, “Wavelet processes at 56 bits of depth in a domain more than one  trillion times finer in resolution than that of a standard CD.” When the phrase “finer in resolution” is used, what does that mean? How does that impact the sound quality the listener perceives? An Analog Devices chipset was chosen for the Wavelet. I see practically no other DACs processing at 56 bits for stereo reproduction.

A: Finer bit resolution refers to the dynamics. More bits allow more dynamic range representation. In practice you will not achieve a significantly greater bit depth than the input recording itself but the additional bits instead allow more precise level resolution in the processing steps to prevent rounding errors, and significantly greater dynamic processing above the noise floor. Lower bit systems are limited in gain adjustment within the digital domain. Let’s say we need a -12dB correction at 63Hz, along with a + 6dB correction at 30Hz, each occurring at difference time coordinates with an overall gain of 4 dB on the channel. This very simple example just required 22 dB of adjustment in overall levels over time.

Q: On the other hand, the frequency of 96 kHz does not seem nearly as radical as some DACs that now are rated by megahertz. Does this indicate that you feel the most critical aspect of digital processing is the bit rate and not the frequency? Please explain.

A: Bit depth is far more audibly dominant. Based on hearing range and Nyquist theory it is audibly beneficial and reasonable to sample up to 48 kHz. However, to assure both the anti-aliasing filter of the A-D converter and the D-A aliasing filter do not adversely affect the audible bandwidth it is useful to have 96kHz of processing. This is certainly higher than necessary, but not wastefully so. Sampling higher will not provide improved transients or extend the audible bandwidth in a useful way.

Let’s look at the filters that are present on playback. First the aliasing filter. If a recording is sampled at 96kHz in the studio, then any frequency above 48kHz is subject to aliasing error. Thus any aliasing filter must be introduced. Second, even great speakers usually roll-off beyond 25 kHz. Third, our hearing mechanism’s qualitative discerning ability fades at 12kHz. Fourth, individual neurons can only fire at a maximum of about 500 Hz. The brain literally reconstructs the band above 1kHz from staggered volleys from multiple neural transmitters. (See Place Theory, Frequency Theory and Volley Theory.) Groups of neurons in the cochlea individually fire at subharmonic frequencies of a sound being heard and collectively phase-lock to match the total frequencies of the sound. This of course leads to sharply reduced phase accuracy in perception above 1kHz. The frequency range process is quite finite.

Neurons, like any transducer, have their version of impulse response called action potential as shown below. Their trip threshold is quite digital in behavior. How the brain sums these tens of thousands of electrical transmissions is miraculous to say the least.

 

Q: The specifications of the Wavelet discuss the following in regard to the Analog attenuation: Analog attenuation available in three steps of -3 dB, -6 dB and -12 dB for an input sensitivity of respectively 0 dBFS = 4 dBV, 7 dBV or 12dBV.  When Brice was setting up the Benchmark AHB2 Amplifier with the Wavelet initially the Sensitivity of the AHB2 was set to VRMS 4 and dBu 14.2, but in order to obtain proper calibration and setup for the Wavelet the Sensitivity setting on the Benchmark amp needed to be changed to VRMS 2 and dBu 8.2. Is this indicating that the output of the amp was too low and needed to be raised?

A: Gain is the amp’s fixed voltage multiplier. Sensitivity is the voltage input required to achieve rated output. It is possible for one amp to have a high sensitivity of 0.5V and another amp (or input of the same amp) a low sensitivity of 6V yet both have the same maximum output. Thus, the sensitivity term is well chosen. Preamps with low output or passive preamps (misnomer) work best with high sensitivity (low V) amplifier inputs. Amps for professional studios are usually less sensitive so they can be driven by the console. The Benchmark amp is adaptable for it can be driven by consumer single ended, balanced, or console levels. Wavelet’s balanced outputs will drive any amplifier. Legacy can match gains for any combination of amps in the house-programmed system configuration file at the factory. There is also 18 dB of adjustment in the manual channel controls. The trimming resistors on the rear panel are primarily for attenuating inputs of high output DACS.

Q: Looking at the cabinet construction of the Valor there are several smallish compartments that seem to separate every driver. Is every driver in the entire speaker isolated? Is the extreme amount of isolation of drivers necessary for the acoustic steering?

A: Yes, that is correct.

Q: There are some tubes running vertically inside the cabinet and they appear to run from the region where the downward firing bass driver is on up into the location of the 14” midrange and post convergent array. What is the purpose of the tubing?

A: The tubing is tuning the enclosure below.

Q: Is the concentric Midrange driver operative? Is it at a lower level than the ones flanking it? I ask because it seems the small horn driver seems to occupy the space where the midrange magnet structure would normally be. Are the internal tubes supplying the mid/bass that seems to come from the concentric 14” cone that is behind the post convergent array?

A: Yes the concentric mid is active. It does not reach as low in frequency as the other 14” drivers. It has a passive filter on board. The magnets are concentric with the rearmost motor belonging to the tweeter. The compression driver’s waveguide sets inside the cone’s voice-coil.

Q: Legacy’s use of internal amplification has been consistent over the past several years. I detect a significant improvement in the results when hearing the class D amplifiers integral to the Valor. Frankly, this is the first speaker I have heard where I have no complaints at all about the class D amps. Please share about the Legacy Audio PowerBloc amps used internally. Why are these ideal for the application? I sense a level of confidence of the sound quality of the speaker and the amps to have precluded use of outboard amps, except for frequencies above about 1,040 Hz. What parameters of sound are improved by the use of active drivers?

A: Matching is assured and voicing is complete this way. Direct coupling a driver to an amplifier eliminates lossy passive components, improves damping. Transients are better realized, and articulation is notably improved. There are 2750 watts of state of the art class D ICEPower amplifiers on board for the drivers to avoid clipping of peaks and provide authoritative weight.

Q: I noticed that the minimum amplification requirements for the Valor are 60wpc versus the V’s recommended minimum of 30wpc. I was surprised to see this. Is this a function of the driver set change? I wonder if the Valor could operate as well with 30wpc, but perhaps you have made a decision that more wattage is preferable? Please explain.

A: While more sensitive, the Valor has extraordinary dynamics to be exploited on 24-bit recordings. Even at modest listening levels the dynamic crests are higher with the Valor. 30 watts will however drive the treble section.

Q: The Valor is a four-way speaker. Please delineate the driver groupings and which channels are feeding them.

A: Wavelet channels

L, R

1,5   Dual 12 subwoofers with dynamic breaking

2,6   Three 14” drivers

3,7    Treble section (titanium coax and AMT PC array)

4,8    SUT array (three 8” full range)

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