Bottlehead Forum

Bottlehead Kits => Kaiju Stereo 300B amp => Topic started by: dave-tx on November 30, 2015, 03:30:03 AM

Title: Kaiju with lower-efficiency speakers
Post by: dave-tx on November 30, 2015, 03:30:03 AM

I'm pretty sure I know the answer from reading the specs, but thought I'd ask anyway...How practical is the Kaiju strapped for driving something like a 86-87dB Magneplanar speaker? 

Title: Re: Kaiju with lower-efficiency speakers
Post by: Paul Joppa on November 30, 2015, 07:37:31 AM

My usual estimate is the ability to generate 102dB peaks. At 16 watts (12dBW) that means speakers of 90dB efficiency.

This approximation comes from a compilation of Stereophile speaker reviews over a few years, in the late 90s; it is the minimum of their recommended power range. So I say this is good for "most audiophiles, most of the time."

For the median audiophile, you might get away with 6dB less efficiency, so 84dB minimum. This is mostly a combination of not needing exceptional loudness, and the fact that SETs overload really gracefully, so minor clipping is not objectionable. (High feedback and/or solid state amps have very hard clipping, so even minor amounts are quite objectionable.) Room size and absorptive treatments also play a role.

Sorry, that puts you in unclear territory - it's a judgement call.

Title: Re: Kaiju with lower-efficiency speakers
Post by: dave-tx on November 30, 2015, 10:42:45 AM

Thanks, Paul - You're right, it's a little unclear territory, but I'm inclined to give it a try.  I'm really itching to do a build and this is the excuse I'm looking for.  I can always work on more efficient speakers later, if needed.

I'm assuming the DC filament supply would likely be unnecessary with low-efficiency speakers, so I'll skip that for now.

Thanks!

Title: Re: Kaiju with lower-efficiency speakers
Post by: Paul Birkeland on November 30, 2015, 12:02:48 PM

We have many customers running 88dB efficient FE83 based speakers on their 3.5W Stereomour amplifiers without complaints (though in some cases the 0.3V signal available from a cell phone or DVD player necessitates a preamplifier). 

The Magnepans are just a hair less efficient, but are also a mostly resistive load, so the extra power should put you in a similar territory.

We would be very surprised if the DC filament upgrade was audible in your setup.

-PB

Title: Re: Kaiju with lower-efficiency speakers
Post by: 2wo on December 01, 2015, 10:28:55 AM

FWIW, with my ~95db speakers. My SR-45 Amp 45's or 2A3 with 2.5V filaments. The hum is virtually inaudible, unless I put my ear to the speaker. When I switch to 300B, with 5V, I can hear a little hum at the listening position when no music is playing...John     

Title: Re: Kaiju with lower-efficiency speakers
Post by: drewh1 on March 20, 2016, 11:26:02 AM

FYI. I have a barely audible hum on mids, Tweeters r silent.  My speakers are 92db. I am going to install the DC filament supply because I  will be using Eml's.

Title: Re: Kaiju with lower-efficiency speakers
Post by: dave-tx on July 17, 2016, 09:30:27 AM

For the record...The Kaiju as a monoblock sounds amazing with Magneplanar 2.7QR speakers.  If anyone has the same doubts that I did when I started this thread, you can lose them now.  Your milage may vary, but I'm nothing less than thrilled.

Title: Re: Kaiju with lower-efficiency speakers
Post by: quad on July 15, 2018, 07:31:46 AM

I know this post was ages ago... but what did you configure the kaiju output impedance selector for the magneplanars?