One such company that has changed names over several decades is Bob Carver LLC, known previously as Sunfire in 1994 and Carver Corporation in 1979. At the heart of the company was high end Carver Amplifiers that were reasonably priced at the time and challenged some of the best and most expensive competitors on the market. As a result, some of his vintage models have become collectors items as people have sought to add them to their collections. Lets take a look at some of the models created by Bob Carver.
1. The Magnetic Field Coil Power Amplifier
The Magnetic Field Coil Power Amplifier used vacuum tubes, coils of wire, and transformers to turn high voltage low currency to low voltage high currency output. This was perfect for amplifying the sound of something. In addition, Bob Carver incorporated a power supply that reacted to the demands of the amplifier, making it an ingenious design and among the best selling Carver Amplifiers. With its history and truly vintage look, it is no wonder the Magnetic Field Coil Power Amplifier is so sought after.
2. The Auto-Corrector
As its name might suggest, the Auto-Corrector was created to help correct audio sounds prior to amplification through limiting the amount of background noise. In addition, the Auto-Corrector split noise reduction into four distinct frequency bands, Carver audio was able to reduce tape hiss and other such sound problems of the day. This was done through the use of bandpass filters, making it unique among Auto-Correctors on the market. As a result, it has quickly become a vintage collectors item.
3. The Sonic Holography
The Sonic Holography was created by Bob Carver to make his Carver Amplifiers better for anyone listening. This was done by introducing a signal in each speaker which helped cancel out the interference experienced by the listener. The interference stopped the sounds from the left speaker hitting the right ear, and vise versa. With so much attention from Bob Carver to make his Carver Amplifiers better for the listener, it is no wonder that Carver audio lives on today, both in production and vintage design.
I’ve been reading the commentary on my new speaker and find the interest very exciting. Some of the comments I will address now.
One: It can’t be done
My answer: Of course it can. Not only that, but I am used to being accused of inventing things that can’t be done, beginning with the Phase Linear 700 watt amplifier of long ago, all the way to my current high-pressure subwoofer. So I’m used to that.
Two: The ribbon looks like it’s from Parts Express
Of course it is. I designed that ribbon over thirteen years ago for a loudspeaker I ended up developing and calling the Sunfire Cinema Ribbon. The ribbon was built in China by Hi-Vi for Homni, my Chinese supplier for drivers at the time. Shortly thereafter I sold the design to Hi-Vi as part of a joint cooperation agreement for manufacturing tooling, and subsequently it was delivered into the public domain by my intent. Hi-Vi, under the joint cooperation agreement, markets it worldwide and now sells it to Parts Express. Again, it was originally designed for my Cinema Ribbon and is still used in Cinema Ribbons today. It is truly an amazing ribbon, if I do say so myself.
Three: 121dB SPL
121dB SPL is an enormous sound pressure level but the numbers that teach us how it does that are comprised of simple arithmetic. I begin: A pair of the small woofers as utilized in the tried-and-true Cinema Ribbons produce a loudspeaker that has a sensitivity of 89dB SPL. The Cinema Ribbon was designed to absorb all the power that my 200 watt per channel amplifier could deliver. At 80 Hz it’s peak-to-peak excursion is 0.48". Now, my new Amazing Line Source speaker has 22 of these drivers per channel. Since each driver can take 100 watts (92 watts with crossover losses), how much can each Amazing Line Source speaker handle? Well, 92 x 22 is 2,024 watts. At those power levels and at 80 Hz, those woofers are moving back and forth 0.48". Or, from another point of view, 80Hz/4 (20 Hz) allows equalization and yields flat response down to 20 Hz with a 450 watt per channel amplifier, assuming a room gain of 8dB at 20 Hz (Theoretically it’s 3dB per boundary, and there are three boundaries in a room for each speaker).
Four: Low Frequency Response
A line source that goes from floor to ceiling is a weird, spooky, and interesting thing. Imagine that your floor and ceiling are mirrors, and the line source has 22 candles instead of woofers. If we look at it, we will see candles going up infinitely to the sky and down infinitely below. The amazing thing is that each reflection of each candle generates real light and so do the reflected sound sources of the line array. Spooky because it seems as if it’s something for nothing, and it almost is! The same holds true for the ribbons. Each ribbon, on speech and music, can easily absorb 200 watts rms and there are thirteen of them per channel. Finally, 200 watts x 13 = 2600 watts – a walk in the park for these ribbons!
Five: Sensitivity – 96dB
Each time the area or the displacement is doubled – all other things held constant – the sensitivity increases 6dB. Here is the arithmetic: One ribbon = 89dB. two ribbons = 95dB. Four ribbons = 101dB. Eight ribbons is 107dB, and 16 ribbons would be 113dB sensitivity IF the voltage across each were held constant. Since these ribbons are in a complex series/parallel configuration we must subtract 17dB because the voltage across each ribbon is substantially lower (approximately 20% of the original voltage) yielding 96dB SPL sensitivity. The precise calculation is as follows: There are thirteen ribbons, so 10 x log(13) is 11dB. 11 + 89 = 100dB, and the crossover throws away 4dB, for a net of 96dB sensitivity. That’s the science.
Strictly speaking, nothing is distortionless. However, in hi-fi, if the distortion is below our threshold of audibility we can color it gone. If it’s gone we can’t hear it and I consider it sufficiently distortionless to call it thus in my use of colloquial English.
Seven: "fast and loose with hyperbole"
I plead guilty for hyperbole, not guilty for fast and loose; my designs always deliver the performance and the numbers, for real, every time, as evidenced by independent reviewers over and over again through the years. Wait and see.
Thanks guys, your comments and passionate responses to this new loudspeaker have made me think.
Great comments, warmest and best,