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Old 10-18-2017, 07:26 AM
david45 david45 is offline
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Join Date: Sep 2016
Location: Montreal Canada
Posts: 33
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Analog Addict,

Thanks for posting pictures of these OB speakers. Considering the extra woofer and the 3db boost in terms of sensitivity, just how efficient are they and how low can they play?

Not that I'm in the market for new speakers, but I have been using a pair of open-baffle speakers designed by Danny Ritchie of GR Research for a few months now along with dual servo subwoofers (also OB) and I am now considering getting a new amplifier and pre. They mesure at 93.5 db all the way down to about 80 hertz and provided they are being used with the OB subwoofers, they can be high-passed anywhere from 80 to 200hz ideally with a cap in between the pre and the amplifier.

For the last few days, I have been using a Line Magnetic 210ia integrated with 300b tubes that I have here on loan and I really like how it sounds. It excels at mid-range and transparency along with very good tri-dimensionality so that is just about perfect for the kind of music I like listening late at night (small ensemble, girl and a guitar, anything with piano or close mic vocals, etc). The speakers are getting a full-range signal and yet the big meter on the front of the amplifier pretty much never indicates over 0.5 watt and maybe 1 watt if I'm really pushing it during the day (ambiance music while doing random stuff and not critical listening). My room isn't the smallest at roughly 3000ft3 but everything is set up in a near field arrangement and the listening position is at about 6 feet from the speakers only.

I am really surprised that a 300b amplifier with only 8 watts per channel can work so well in my system and it makes me wonder if a 45 PSE and its glorious 3.5 watts could be an even better fit especially if it is being hi-passed (?). Could it also benefit from the IIPS mod?
I realize that Dennis still isn't offering his own version of your amplifier and that you recommend speakers that are 100db efficient or even higher, but I am intrigued nevertheless.

It's been a few months since your first listening session of the kt77 PSE prototype in triode and I also wonder how things are evolving as this is also right up my alley especially if it can be dialed-in to provide a maximum of mid-range magic similar to a 2a3-300b-45 amplifier but at affordable output tube prices.

I am also considering a triode strapped amp built on the 45 chassis with 20 watts transformers and IIPS along with a pre just like Florida Boy and Musica Amantem.

Also in the cards would be to fly to North Carolina and stop by Cary for a listening session if that is a possibility that could help me make up my mind.

Cheers,

David


Quote:
Originally Posted by Analog Addict View Post
A dual woofer OB design would never work with Inspire amps....

Untitled by Analog Addict, on Flickr

Untitled by Analog Addict, on Flickr

Untitled by Analog Addict, on Flickr

Dennis actually set these up as a true dual woofer design with the woofers running in parallel. The extra driver adds approx 3db spl. The quality of the Altec woofers is ahem...better than the drivers we were using, and they still sounded fantastic with any Inspire amp. Given that the sensitivity of the Altec woofers is probably 6-8 db better than the ones we used, I think even a 45 SET amp should work extremely well in this application

Last edited by david45; 10-18-2017 at 11:10 PM.
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