Absolutely not for 3 and 4!
I feel sad you write that and you must have no experience with OTL components?
Vintage audio, which can sound pretty good as I experience every day.
My experience with A LOT OF fifties and sixties vintage audio systems is that the OTL
versions sounds a bit better, more bright so to say and a tough bass without distortion.
F.e. the AG9018 on which both systems are possible.
The experience of all people who have this amp is that the OTL version gives more
satisfaction to listen to.
It is also possible to find two AG9007 mono power amps. and use those as mono blocks.
These amps were high end in their days and now hardly to find but nothing is impossible.
They were actually build for professional purpose in mono systems with very good
three-system speakers: a very large bass cabinet and two high tone satellites. All with
9710A or B speakers.
BTW this amp is OTL Circlotron.
http://www.grammofoon.com/HiQGN/Fotos/players38.htm
The set here is of course the mono set. But the AG9007 is also a good mono block.
Phillips Phonogram themself used them in the sixties in their listening studios. They even started a new small
production for that purpose.
The speaker set was available in 800 and 1200 ohm.
The AG9007 'eats' both and even TWO of these speaker sets.
I used this complete set for several years about ten years ago.
This was my set:
http://www.grammofoon.com/HiQGN/Fotos/players35.htmActually, my AG9007 was of the 1963 production. So, for professional purposes.
A whole set did cost about 3000 Dutch Guilders in the late fifties.
John Average did earn about 200-250 Guilders a month... talkin' about high-end in mono.
I discussed with my friend who has repaired several otl radios and I have heard them as otl ,with old Philips transformers and new transformers made by my friend . OTL sounds a bit better than old Philips trafos but my friends trafos in the same system have the best SQ. Nowadays am listening to his built amp with his trafos driving AD5200 speakers. The amp on bench testing easily crosses 60k in FR without any feedback.
I own and have refurbished dozens of valve amps . American , British , German and off course ,Indian . You probably have no experience with them.
Most of these , have better opts than Philips . The American ones are like the engines of their muscle cars of that era. And
please note that my suggestion of impedance matching transformers is for connecting the op's American amp to the 80Ohms drivers . These are external devices that go between the amp and speakers. No internal modifications are required and more important, they shall prevent the historical devices from turning into historical junk.
About my ignorance:-I am also a Philips fan but not a blind fan. Philips came to India in1958 and soon established several factories making everything from light bulbs to components and complete gear. India was most likely their largest manufacturing base outside Holland. The components were also sent to their European devisions for use in their production, off course for obvious reasons , this was never advertised
Philips made 8" and 12" FR drivers in India. The 8" were a somewhat cheaper variation of the 9710 to suit the Indian market and are still famous here as the Hi-Q driver. Boston continued their production after purchasing the Philips business. They retained most of the 9710 characteristics including the (in)famous shout. When Philips sold the complete system here , it included a 7" platter manual record player with a ceramic cart and a small built in amp. One 8" driver per side in sealed enclosures as the speaker system. Even this was a big luxurious item in those days. That system had a built in zobel network in the pre amp to tame the speaker shout , so while the speakers sounded very good with the Philips player , they were too bright with many other amps.
Because of my infatuation with these drivers , I developed a small batch of custom drivers with more powerful magnets and modified cones. These were installed in TL cabs the system was demoed in Lencoheaven meets in Belgium. I spent about €4000 on that project.
Just for study and to acquire first hand knowledge I have purchased a lot of gear and now require 200 sq mtr enclosed space to store all that. I do own a few pieces of Philips Holland equipment, including a pair of the rare MFB active speakers.
About suggestion #4What is wrong with replacing 800 Ohms 9710 with 8Ohms versions? 8 Ohms shall match correctly with the OP's amp that has 8 Ohms output taps.
In fact, I wrote the short edition of this suggestion as I thought the long one shall upset you, but as you are upset despite that I share the long version here ,
Long version of suggestion #4Sell these and get the 8 Ohms versions or better still , get the AD5200 or the AD 3600 . These 12" and 10" drivers are far better sounding than the 9710 , especially when paired with an amp other than Philips. There is a recent discussion about them here.
https://www.lencoheaven.net/forum/index.php?topic=43480.0Off course, I expect that Rene shall be upset at my suggestion and say that 9710 were and are more popular. This is because they were cheaper (and not better) than the bigger drivers so they had more buyers then and are more easily available today. Phillips introduced the large size drivers first and then came up with the 8" 9710 when they wanted to increase the sales.
Concluding remarksI have said whatever I want to so I am signing off from this topic and won't be replying.
Regards
Anwesh
