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QuoteDSP loudspeaker crossovers done right
From the above we've learned that:-
• Heavy-handed correction exacerbates acoustical problems
• Sharp, linear-phase filters cause pre-ringing
• Targeting an exact linear-phase sum can cause pre-echos.
In short, brute-force correction sounds grainy and smudgy. When you hear cymbals go "splash" instead of
"crash", it's naive DSP at work. So:-
• Do not shave off the hair, a nasty stubble will grow back.
• Do not correct beyond the very beginning of the impulse response.
• The gentler you correct, the wider the angle over which the correction still improves things.
• Target a minimum phase sum.
For the time being I would strongly recommend designing the correction manually. This rules out FIR as the
main workhorse. For each bump or dip one corrects, one should know exactly where it comes from, and make
sure that it isn't better corrected for acoustically. Unfortunately, designing DSP filters does not relieve one from having to know one's acoustics.
QuoteAlso shown in Figure 8 is the impulse responses for a complementary high-pass brick-wall FIR. If we construct a crossover filter bank with such a complementary pair of filters, the Gibbs ripples are also complementary (since we will expect the filters to sum to a flat response with linear phase, producing a perfect impulse). The summed result will thus be free of any Gibbs ripple, so what's the problem? The problem is off-axis. The complementary ripples will only cancel if the delay suffered by the signal from each driver is identical. Off-axis, where the path lengths differ, the ripples will not cancel, leading to the possibility that Gibbs ripple might become audible (just like a high-Q ringing filter).
Such summing errors will be more pronounced at higher crossover frequencies because the ripples are more closely spaced. Lower frequency
crossovers will have wider ripples which will more easily cancel in the presence of off-axis induced delays.
It is evident that steeper cut-off slopes give rise to Gibbs ripples of greater duration. It makes sense therefore to restrict the cut-off slope to be no more than is necessary for the application.
QuoteI - Digital crossovers
Some people think that digital crossovers will replace analog ones, because digital filters can be designed with desirable characteristics that are impossible to realize with analog circuitry. In particular, lowpass and highpass filters with extremely steep slopes and linear phase shift are possible. Steep slopes reduce the overlap region between drivers. Linear phase shift eliminates waveform distortion and merely causes a delay of the signal. Such characteristics can be obtained from the digital equivalent of tapped delay line filters, which have a finite impulse response (FIR) duration that depends upon the number of taps used. Digital FIR filters can have almost any desired frequency response, if the number of weighted taps is made sufficiently high. [1]
The linear phase shift comes at a price. The impulse response rings. The more so, the steeper the filter slopes. Both lowpass and highpass sections of the crossover ring, but when the outputs are combined, as for a crossover, then the two impulse responses add to a non-ringing, delayed pulse.
All would be fine, if we listened only in anechoic spaces or to speakers with coincident drivers. In reality we use speakers in rooms with reflections and reverberation and the the drivers are separated from each other due to their sizes. As a consequence the off-axis response of the speaker matters and contributes to what we hear. With the drivers non-coincident, the lowpass and highpass outputs are delayed different amounts at points off-axis, and the ringing is no longer canceled in the addition. In the best case the drivers might be coaxial, but this has another set of problems. Very steep crossovers can also cause a very abrupt change in the polar pattern of the speaker, when transitioning from a large diameter driver to a small one. Under reverberant conditions and/or listening off-axis this may have audible consequences.
QuoteAfter many months of research I went with these speakers for the following reasons.
Extreme tonal accuracy, +/- 1dB from 20Hz to 20KHz.
Non-ported enclosure for clean bass.
Fabric dome tweeter for smooth treble.
Phase/time aligned for accurate transient reproduction.
Non-parallel cabinet walls to minimize internal standing waves.
Quick signal drop off in waterfall plots.
Clean pulse and step response.
Auditioned them and enjoyed the best sound I have ever heard!
It is hard to describe these speakers for I believe they are pretty much fully accurate and transparent. They totally disappear when playing despite their 76 inch height and 300 lbs. each weight. When you slip in a SACD/CD the wall dissapears and becomes a music stage for the musicians. Others have noticed this too and are quite dissapointed when they get home only to find their speakers don't do the disappering act, you can hear where each speaker is. Dunlavy's are matched to withen 0.5dB of each other to ensure this.
These speakers have a certain cleanness and accuracy that is very hard to describe. When I was at the factory in Colorado springs and did A/B comparisons with other Dunalvy speakers these just sounded more open. It was like the band was in the open, on a hill outside or something. With the other speakers, though they sounded great, the music was slightly veiled. I believe this is born out by the waterfall plots of the Millenniums, very clean and quick decay.
The soundstage of these is excellent. With some source material you can hear sounds coming from beyond the left and right of the speakers. Instruments are accurately placed across the area between, and beyond, the speakers. The speakers totally disappear, when the singer and drums are between the speakers, that is where the sound is, you don't hear any sound from the speakers themselves. The sweet spot is only wide enough for one though. However, anywhere in the room the sound is tonally balanced and enjoyable, you just don't get that nice balanced imaging you do in the middle. This is what totally turned me off of planer speakers, their horrible off axis tonal balance, and their laughable bass for that matter.
Perhaps the most noteable aspect of the Millenniums is there stupendous bass. It is so clean you sometimes think its lacking. There is absolutely no boom, overhang, thump, or distortion, even at high levels. I must admit I am used to hearing the 100Hz hump on most cheaper speakers that simulate a good bass response. I notice songs sound different. The bass is very clean and deep too. You can feel deep bass that you couldn't with lesser speakers. Lest you think these speakers are lacking in bass, if you play a song that truely has bass, these will reproduce it in spades. It is just amazing to listen to songs and for the first time hear and feel the bass/drum line of the song very cleanly. There is lots more detail and nuances to be found in the deeper few octives of music than I was aware of before.
The mids are flawless too. Voices are clean and undistorted. Dianna Krall sounds fabulous. Here music with the bass and piano sounds simply stunning. Celine Dion sounds excellent too. The harshness and forwardness of her voice is subdued to some extent, more enjoyable. Though with some of her songs, let's face it, she's really hollering. Men's voices also are nice, never nasally or boomy, always clean.
The treble is so clean and accurate, it captures the metalic sheen of cymbols and other metalic instruments but you need SACD to really enjoy this. There is no brightness, exageration, or harshness to be found, unless it is in the recording. When I compare the treble of these to that of my Paradigm Studio 100's in the home theater room, there is no comparison. Fabric dome tweeters are some much cleaner than metal domes, more natural and enjoyable.
The speakers themselves are a joy to look at. Their looks really grow on you. You start to appreciate their unique hourglass shape. It is so gracefull. My wife, who about flipped when she first say them, way too big and ugly as sin. Now she likes their looks. When we have visitors the women are usually amazed my wife allows me to have them. All the guys drool. You can tell there is some prime sound able to be produced by these massive transducers. The speakers are actually larger than I am, I'm 6-3 and 250 lbs. The speakers have an inch and 50 lbs on me. My son calls them the speaker gods.
About the only thing I can say bad about them is how they reveal poor recordings. Imagine my dismay when two of favorite groups as a teenager have some bad recordings, Fleetwood Mac and Abba. I love listening to SACD music with these. Horns and violins are richer and not strident as they can be with normal CD's. Cymbols are more metalic. The soundstage is enhanced.
Is this the perfect speaker? Probably not, but I am very happy with it. To me it sounded even better than Dunlavy's top of the line SC-V and SC-VI's. For someone with some money to burn, fly out to Colorado and listen to them for yourself. I don't think any dealer carries these for demos.
Read up on the manufacturer's website for the theory behind these speakers. The time alignment of the drivers, the hourglass shape etc. It is www.dunlavyaudio.com. Good reading.
| Electrical: | |
| Impedance: | 186 Ohms nominal |
| Resistance per foot (D.C.): | Less than 180 milli-Ohms for center conductor and less than 4 milli-Ohms for shield |
| Total loss for 3m length: | Immeasurable over the 20 Hz to 20 kHz range |
| Capacitance per foot: | 8 pico-Farads nominal |
| Inductance per foot: | 290 nano-Henrys nominal |
| Amplitude and Phase response: | Into an 10 K Ohm load, an 8 foot length of DAL ULC cable exhibits a drop of only 0.5 dB and a phase lag of only 30 degrees at 5 MHz (immeasurably flat from D.C. to 250 kHz) |
| Pulse-coherence factor: | Terminated in 10 K Ohms, an 3 meter length of DAL ULC interconnect will reproduce 1 MHz square waves and 1 micro-second wide pulses with an accuracy indistinguishable from the output of the signal generator |
| Velocity of Propagation: | Greater than 90%, relative to light in free space |
| Physical: | |
| Size: | 0.265 inches in diameter |
| Color: | Neutral tan |
| Lengths: | Standard: 1 meter; 2 meter; 3 meter; 7 meter |
| Optional Lengths: | Lengths from .5 meter to 30 meters + |
| Terminations: | ULC Standard: RCA ULC Reference: Neutrik RCA ULC Balanced Reference: Neutrik XLR |
| - All terminations are heavily gold plated. | |
| Inner and Outer Conductors: | Patented multi-strand ultra pure silver plated copper wiring |
| Electrical: | |
| Impedance: | 6 Ohms, nominal. |
| Resistance per foot (D.C.): | Less than 2.5 milli-Ohms |
| Total loss for 8ft. length: | Immeasurable over the 20 Hz to 20 kHz range into an 8 Ohm resistive load |
| Capacitance per foot: | 340 pico-Farads |
| Inductance per foot: | 21.8 nano-Henrys |
| Amplitude and Phase response: | Into an 8 Ohm load, an 8 foot length of Z6 cable exhibits a drop of only 0.5 dB and a phase lag of only 30 degrees at 5 MHz (immeasurably flat from D.C. to 250 kHz) |
| Pulse-coherence factor: | Terminated in 8 Ohms, an 8 foot length of DAL Z6 cable will reproduce square waves up to 1 MHz with an accuracy indistinguishable from the output of the signal generator |
| Physical: | |
| Size: | 0.5 inches in diameter |
| Color: | Neutral tan |
| Lengths: | Standard: 8 foot; 12 foot; 16 foot; 24 foot singles and pairs |
| Optional Lengths: | Lengths from 6 inches to 100 feet |
| Terminations: | BN4: Banana pin GS4: 1/4 inch spade GGS4: 3/8 inch spade |
| - All terminations are heavily gold plated in six inch lengths. Terminations employ unique threaded bolt application system for easy end user installation. | |
| Internal Wiring: | Patented multi-strand high purity silver plated copper wiring. (US Patent # - 5,510,578; 4/23/96) |
 The DUNTECH PCL25 Loudspeaker has been designed for the discerning listener who demands very accurate sound reproduction from a small package. And at an affordable price. The PCL25 is faithful to the design philosophies that encompass all DUNTECH loudspeakers, and for which Duntech Audio has received international acclaim. The technology is further enhanced by hand-crafted cabinets, which are finished in authentic timber veneer with acoustically transparent black grille cloth. What makes the PCL25 better? The DUNTECH PCL25 Loudspeaker is a two way, three driver design in which the drivers are arranged in a symmetrical fashion along a vertical axis. This creates a simulated point-source radiation pattern. To achieve proper stereo-imaging and depth, loudspeakers must possess point-source radiation patterns when reproducing music recorded by microphones, which are themselves point-source devices. Music as is should be heard The sound from the PCL25 will arrive at your ears simultaneously. It will be low in distortion and sound extremely well-focussed, giving an almost transparent quality. So, the music you hear will create the feeling of "being there", as if your were hearing it played "live". This is the ultimate benefit of DUNTECH pulse coherent technology... excellent stereo-imaging, depth and clarity. And, when you consider the price of the PCL25 and the inclusion of a 5 year warranty, it all adds up to a remarkable loudspeaker package.   Time-aligned for greater music accuracy The three drivers in the PCL25 are accurately time-aligned. This means the radiating centres of the drivers are exactly equidistant at the normal listening distance of 3.5 metres. Accurate time-alignment of the drivers is one of a number of design features that Duntech has collectively labelled "pulse-coherent". Pulse coherency determines the ability of a loudspeaker to reproduce complex musical sounds without blurring or smearing. It allows a loudspeaker to faithfully reproduce sound as it is heard naturally by the human ear. |
| Electrical | |
| Frequency Response Measured at 3.5M (11.5ft) on the tweeter axis | 55Hz-20KHz ±3dB |
| Efficiency Referenced at 1M (3.3 ft) on tweeter axis with an input of 2.83 volts RMS (1 watt at 8 ohms) | 89dB SPL |
| Nominal Impedance | 4 ohms Variance 3.5-6.5 |
| Power Rating Peak power for 10 µS | 500 watts |
| Recommended Amplifier Power Minimum RMS per channel | 30 watts |
| Pulse Coherency Factor Propagation time error at 3.5M (11.5 ft) on the tweeter axis | Less than 10µS |
| Harmonic Distortion Referenced at 1M (3.3 ft) on the tweeter axis with an input of 2.83 volts RMS (1 watt at 8 ohms) | Less than 0.5% THD above 100Hz |
| Phase Variation versus Frequency Varies less that ±35 deg | 150Hz to 15Khz |
| Crossover | First order type |
| Drivers Bass Tweeter | 2x160mm (6.3") 1x25mm (1") |
| Input Terminals | Gold plated, accepts bonana, spade or cable connections |
| Bi-Wiring | Yes |
| Passive Bi-Amplification | Yes |
| Footnote: All measurements taken at ambient temperature of 23°C (72°F) | |
| Mechanical | |
| Finish | Available in Jarrah, Brazilian Rosewood and Black Oak. |
| Size Height Width Depth | 606mm (24") 268mm (11") 350mm (14") |
| Weight Per cabinet unpacked | 20Kg (44lbs) |
| Warranty | Five (5) years, subject to Duntech Audio Warranty Policy |
| Stand | Optional |
