Eico HF-81 8ohm with Philips 800 ohm speakers

[Landon]

Hello everyone

I got a pair of Philips 9710AM/01 800ohm speakers and when was about to connect it to my Eico Hf-81 I realized there is inconsistent impedance, since the Eico is 8 ohm

Does anyone knows if need a matching transformer, or if I could just connect the Philips to the 8 ohm terminal of the amp?

I already have a pair of those matching transformers but I’m not sure if it’s a safe idea to connect them

I’m attaching picture of the speakers and transformers, they are quite beefy

Thanks !

 

[as_audio]

The output will be very low using "standard" amplifiers.

 

[rayma]

That's what those transformers are for. And they look like good ones.

 

[Landon]

So the matching impedance transformer (8ohm in, 800 ohm out) is the only way to fully use the speakers right?

 

[as_audio]

Or use the dedicated Philips amp.

 

[rayma]

The Eico does have a 32 ohm tap, but that will not properly match the 800 ohm speaker.
There is no safety issue with the matching transformer.

 

[Landon]

Thank you everyone !

Getting a dedicated Philips amp is not possible for availability in Buenos Aires (I’m from Argentina) and because I really love the sound of my Eico.

The transformers were built to spec for this particular use and are really heavy and big. So that you get a reference in this picture they are positioned within the cabinet

I will try it in the following weeks hopefully, and get back to you with the results

Thanks for your help !

 

[rayma]

Good luck, just follow the wiring diagram carefully.

 

[as_audio]

Is your Eico wired for 220 volts ? Thanks

 

[Landon]

No, it’s 110v with original transformers

 

[OldHector]

A pair of Philips 9710/01AM are quite valuable, and are also quite frail because the voice coil is wrapped with very fine wire to get the high impedance. I would be surprised if they were not valuable, since there are people who would like to emulate the Sonab OA6 Type 1 loudspeakers (that used EL86 in a totem pole arrangement to drive that type of loudspeaker without an output transformer), or who may have an old Philips amplifier like the AG9014 that only works with that impedance.

 

[Landon]

Hello Hector. I agree this piece of equipment is valuable and deserves great care !

I will try the matching transformer and get back with the results !

 

[JoeAlders]

But...... where those 800 Ohm speakers not designed to be used in OTL amplifiers?

 

[as_audio]

See post 7

 

[Landon]

But...... where those 800 Ohm speakers not designed to be used in OTL amplifiers?

Yes they were, but I don't have one and honestly wouldn't sell my Eico to get one so I had to find another way 🙂

 

[jhstewart9]

The original of the Series PP Amp by Sinclair & Peterson at General Radio (GenRad).