Fritz Carrera 7 Be and 300B power amp?

Some thoughts from my experiences with 300b.

I was curious about 300b tube sound. But they were never going to power my main system. So, instead I chose to have them power my headphone system. Turned out to be a great choice for me. This gave me a great opportunity to experience their fantastic sound. This lead to me completing upgrading my main system to all tubes.

This may be out of your price range but my 300b headphone amp can also be used as an integrated amp and drive speakers. Woo WA5-LE. 
 

To get great tube sound out of speakers like you are considering, a used Audio Research I-50 would be a good choice. Not 300b, but warm and detailed with more power.

I haven't seen the phase or impedance graphs for the BEs ... I'd call Fritz but it seems to cover the lower end:

          Recommended Power: 5 - 200 Watts RMS, without clipping

Fritz will tell you straight up.

Call him.

I’d say most likely but talk to Fritz. 

I also suggest you talk to John, owner of Fritz. 

What is your room size?  I own Fritz Carbon 7s and use them in a 15x12x8' room driven by a PP tube amp with 20wpc. That is more power than is needed for my room.  With this amp the Carbons could fill a much larger room.  That said, my thinking is a 300B SET would be on the border regarding power.   

At 87db I'm going to say no. In my experience with 300b amps you need at a min 95db to have enough for dynamic swings. also to consider SET 300b's amps really only work properly in the first half of the power delivery they tend to distort fast at the upper levels of their power range.  if your listening at background levels sure but if you want dynamics and a good range of volume for the normal listener then no.  I ran 94db 8ohm speakers on a 300B amp and if I was honest it wasn't enough. only 8wpc but really only 4-5wpc usable IMO. 

Fritz Carrera 7 Be:

There are at least two links on his website that are articles/reviews of his speakers being used with 8-watt 300B amps .

I have successfully run my 88db Carbon 7 SE mkII’s with a 3.3 watt 2a3 SET amp and never was it close to running out of gas.

Remember, it’s that lack of a traditional power hungry crossover that allows the Fritz speakers to sing on just a few watts. The sensitivity isn’t everything. His speakers are a very benign load wrt impedance and phase shifts.

Give John a call and let us know what he says

With Fritz It’s the true 8ohm nominal impedance spec that makes it possible.  I suspect it will mostly have to do with room size and how loud to be able to go more so than the amp can’t drive the speakers well.  

Thanks for your help folks. My room is 13 x 11 with the speakers lined up along the long wall. One of the short sides is open to the rest of the house. So small room basically.

Speaker are 5ft apart and I'm sitting 6 ft away

I used to do audio shows with Fritz where we used the Carreras and Carbon 7s with a 10 watt 300B SET amplifier. The combination worked just fine in a room that was 12' x 19', and we got it pretty loud, even trying to intentionally clip the amp. The smooth impedance curve and the benign phase angles of Fritz speakers makes use with low powered amps, including SET, possible. A lot will depend on the how well the amp is designed, the size of your room, and how hard you are going to push the amp.

My one bit of advice, having heard Fritz in hotels and owning similar sized 2-way speakers is that they really bloom in well treated rooms.  Excess reflections will really make these speakers sound a lot smaller and less powerful.

Also, I would think that having the speakers pointed towards the non-wall would help with tuning / treatments.

I owned the Carrera Be's for over three years and used them with a number of different amps both SS and tubes.  The best sound I ever got from them was with a Supratek Chardonnay preamp and a Music Reference RM-10 tube amplifier. 

Going by specs alone a (apparently fairly easy load) 87dB sensitive speaker paired with a no more than ~8W 300B-based SET wouldn’t wring out the most of such a combo. You could no doubt attain great sound in moderately sized spacings, also at fairly loud SPL’s, but from my chair the real treat of low powered SET’s is using them with very high efficiency, preferably all-horn speakers (i.e.: +100dB sensitivity) where you’re taking advantage of the low distortion and ease of SET’s at fraction of wattages (ideally though I wouldn’t pair SET’s with high efficiency, high power capacity speakers with large diameter, heavy voice coils; these are better off with higher powered SS or tube amps). Driving speakers 15-20dB’s less sensitive - all things being more or less equal load-wise - will require up 100x the amount of power of a given amp, and with only so many wattages from an SET you won’t be using them at their best here. That’s not to say it couldn’t great to your ears regardless, certainly at no more than moderate SPL’s, but you’d be wanting for headroom.

With series crossovers which use much smaller and far fewer parts than regular speaker crossovers, my loudspeakers are very easy to drive with tube amps.  I have 8 push-pull integrated tube amps with EL84, EL34, 6L6, 6550, KT88 & KT90 power tubes with 12 to 80 watts per channel and a 300B amp @ 8 watts, a EL34 single power tube amp @ 5 watts and a Decware EL84 amp with 2.3 watts per channel that drives all of my speakers great in my 14 x 22 ft living room. 

Happy listening...   Fritz