Oh, I get it. You don't have a separate Subwoofer, but your system as a whole can produce subwoofer frequencies?
FOURTEEN AMP CHANNELS?
Are we talking about bi-amping/tri-amping here?
So Comb filtering is nonexistent below 80 Hz?
I think this system has caught your curiosity.
Now this system is rooted in developments over 70 years. It is not something that I dreamed up out of nowhere. The system actually has a long pedigree.
I will try and hit the high lights. I will also put this information on my system site.
The idea of using a Gedackt, or closed organ pipe, to load a loudspeaker was conceived by the "father" of high fidelity reproduction, Paul Voight back in the 1930s.
Gilbert Briggs, founder of Wharfedale loudspeakers, in his classic book, Sound reproduction, describes his experiments with the Voight Quarter wave pipe. He also has constructional details of a folded quarter wave pipe by Ralph West of Decca. This was designed for the GE metal cone speaker. It was sold by Decca as the Decca, Corner Horn. It is not a horn though, it is a folded Voight quarter wave pipe. It is the first folded pipe loading of a speaker I'm aware of. Paul Voight's major interest was the horn loading of speaker. He founded Lowther, who are still in business and flourishing
The first addition of Gilbert Briggs Book was 1949, I have the third edition of 1953. My copy has been in my possession for 54 years, and is well worn. Some things never change. Gilbert starts his book lamenting the standards, of the average consumer, and the poor quality of much commercial sound!
Anyhow I built a Voight quarter wave pipe. The first driver was a WB 8 inch given to me by a friend of my father. When the Goodmans Axiette, designed by Ted Jordan, appeared I installed one of those and results were much better.
When the Jordan Watts drivers appeared I built a pair of Ralph West's quarter wave pipes for them. These were full range drivers, which I supplemented with a tweeter made for the BBC by Standard Telephones and cables, which later became known as the famous Coles tweeter. I had those speakers a long time and they were excellent.
During the sixties Decca asked one of their team, Dr A.R. Bailey to further develop the TL. He was seconded to Radford, the famous amplifier people who wanted to develop the TL. The team included Irvin Budd M. Fried and John Wright.
A lot of money was spent, and the world's first reverse tapered folded TL appeared.
http://www.t-linespeakers.org/classics/radford.html
Dr A.R Bailey also published a classic design in Hi-Fi news.
Radford lost interest, and Irvin Budd M. Fried formed IMF speakers. John Wright was a part of IMF. The classic IMF TL appeared.
http://imf-electronics.com/
These speakers were produced during the 70s
The BBC had a huge interest in improving monitor loudspeakers, and started a big research project. Jim Rogers, one of the great pioneers of audio, whose company produced a full line of audio equipment was heavily involved. Later Raymond Cooke founder and MOD of KEF was also involved. Many of those BBC in house designers went on to found fine loudspeaker companies. Harbeth, Chartwell and Mordant Short come to mind.
Many famous speakers came out of these developments, with the BBC granting licenses to a number of manufacturers.
Now none other, than the great Peter Walker OBE, founder and MOD of Quad Electro Acoustics was heavily involved in designing and supplying amplifiers to the BBC.
One of the most famous and legendary of the BBC monitors was the Rogers/IMF TL with amplifiers and active crossovers designed and supplied by Peter Walker. These speakers were later modified by KEF I believe. These speakers had a reputation for creating a sound field that floated in space. They were considered the most accurate speakers of the day.
In 1980 John Wight founded TDL. He was a great speaker designer, who I don't think ever deigned a bad speaker. All his offerings were superior. He produced the largest range of commercial TLs the world has seen. He died in 1999.
http://www.stereophile.com/news/10468/
The last speaker John Wright produced before he died was, as far as I know, the world's only commercial dual TL speaker. It was superb, and back then retailed over here at somewhere over 20K per pair. I think it could lay a strong claim to finest speaker using moving coil drivers ever offered to the public.
http://digilander.libero.it/piani/cataloghi_tdl/generale-2.jpg
After I moved to Canada in 1970 I produced a number of TL designs for the Jordan Watts driver.
After coming to the US in 1976, I built the lines which are basically my center backs. They are built around the famous KEF B139, two to each line. Originally they were biamped using the KEF units and four Jordan Watts drivers as a line source. I modified, and built these drivers for the purpose. The problem, was comb filtering! So in 1984 I modified them to dual lines using in addition to the KEF units, three Dynaudio units, a low mid cone driver, an upper mid dome, and an HF dome. The 180 Hz crossover is active, so the speakers are still biamped. The other three units have a first order passive crossover, that took 10 ears to reach their final form. These were my fixed studio monitors until two years ago. When I moved my equipment to Benedict and built my new space, I rebuilt the bass lines to take advantage of the mathematical model of G.L. Ausperger published in 2000. This has made the bass a little tighter. No other changes were made.
At the request of SEAS of Norway, Joe d'Appolito developed the THOR transmission line for their Exel line of drivers. This is a superb speaker. He used Aupurger's TL model.
Now to my current system.
http://mdcarter.smugmug.com/gallery/2424008_RKGvb#127077128
The main left and rights are folded dual TLs with the tuning 1/2 octave apart. The speakers are in fact triamped.
The line containing the 7 inch drivers, uses, and develops Joe's work extensively, although it is a different line. The crossover to the tweeter is passive. These lines are driven by two Quad 909 amps providing 250 watts per channel so there are two amp channels accounted for.
The drivers in the large lines are the 10 inch SEAS Exel drivers. Fs 20 Hz. The upper two in addition to carrying the bass also provide step/diffraction compensation for the smaller drivers above. These speakers are driven by a Quad 405 II providing 100 watts per channel via an active crossover. Another two amp channels, we are now at four.
The lower 10 inch drivers are fed by active crossover at 80 Hz and reinforce the bass from the upper driver. Each is fed by a Quad 405 II. Now we are up to six amp channels. The driver spacing is much less than the wavelengths involved, so comb filtering is not an issue.
The center speaker is a TL using the SEAS coaxial drivers. The tweeter is not connected in the upper driver. The crossover of the lower coaxial driver is passive. The upper driver provides step/diffraction compensation via an active crossover. This center speaker is powered by both channels of another Quad 909. So now we are up to 8 amp channels.
The surrounds are two and a half way sealed speakers using Dynaudio drivers. Crossovers are passive. These speakers are driven by a Quad 405 II. Now we are up to 10 amp channels.
The Center backs as previously stated are biamped at 180 Hz, via active crossover. These speakers are driven by two Quad 405 IIs. So now we are up to the 14 amp channels.
The rear backs are overkill, but these speakers were far too good to part out. So I revised them. On SACD of antiphonal organs they still show there mettle, and have a deep bass reach.
I hope I have satisfied your curiosity, and shown you the speakers pedigree so to speak.
