Tube Amps, Magnapans and Impedance


I have tubed monoblocks running in class A with the output transformers rated at 8 ohms. They are driving Magnapan 3.7s which are rated at 4 ohms. Before I bought them I called Magnapan to get the frequency curve for their speakers. The engineer advised me that they are nominally rated at 4 ohms, the lowest load they present at their lowest frequency, but the frequency curve was essentially flat at 6-8 ohms throughout the audible range. The curve he faxed was satisfactory and I have been running them this way since new.

The reason for this thread is: A friend brought over his friend for a visit and listen. When the subject of tubes and planars arose and the impedance ’mismatch’ was discussed, he stated I was missing out by not having a 4 ohm amp. I tried to alleviate his concern with the above to no avail. I stipulated that it is good electrical practice to match the load to the amp but in my case a 6-8 ohm load across the band with tubed monoblock running in class A at 8 ohms was not significantly audible if at all to justify altering the transformers. I just didn’t bother after listening.

My question to my fellow audiophiles, particularly those who have tubed amps running at 8 ohms into loads between 6-8 ohms - Magnapans being the best - what are your thoughts on the subject?

In my experience it would take a speaker with a 4 ohm rating in the midrange where the music lives to really affect the performance with an anemic amp. Anemic bass and washed out mids are sure signs of an amp struggling with its load - which I do not have. My Magnapans sing from the very bottom of their range to the top. The human voice is especially seductive.

I think he had a case of ’wish I had a system like this’ blues. I think there is a term for that. Thoughts are appreciated.
128x128keesue
you let him park inside ?
just kidding
iF it sounds great move on, don’t worry be happy..

IF you have doubts borrow a high current amp, or tubes w more taps. My Music Reference has 2 ohm taps.
Thanks, guys.  I don't listen at super loud levels and don't expect thundering bass. (I did have a sub, but it died, and frankly I don't miss it).  The Maggies sing with music on their own.  Double bass sounds like double bass, brass cymbals sound like brass cymbals and instruments and voices have timbre for days.  That is Magnapan's calling card and precisely why I bought them.  They are in a small office/study and the acoustics preclude me from blasting (although I have on occasion).  It is like listening in an intimate night club right in front of the musicians.  Magical, especially when I invoke the SS-X for live recordings which I acquired for just that purpose.  That thing is incredible.  I wrote about it which was the only other post I think I ever started in all these years.

I just thought you'd get a kick out of this.  There is an ongoing thread posing the question 'why topics get contentious' when this is just a hobby for fellow audiophiles wishing to share.  For everyman's passion, there is always a cold wet blanket in the wings.  I refer to it as 'the messianic compulsion'.  "Corvette parked next to a Ferrari".  HA!  Well put, indeed!  My friend did call me later to apologize, noting I never expressed interest in what his friend had for comparison.  I cared less.  

I will concede a high current amp with stable power into 2 ohms would drive the Maggies into nirvana.  Maybe I'll break down one day and score if I move my system into a larger room.  I have a friend who has a Krell driving Martin Logans which would be ideal. He has a large room and he can turn up the heat!  He also heard my system at full tilt and gave it the thumbs up. He is an audio technician and it was gratifying to get his approval.  

I am actually considering some speakers I could drive with a SS amp for full-tilt boogying where timbre is not the first priority. Perhaps some Klipsch Horns would do the trick, eh?  :-).  Actually, I rekindled my rememberance of some Walsh Ohms that knocked my socks off.  Hmmmm...

Good fun sharing this hobby.  I've learned over the years to tune the nay-sayin' know-it-alls out. When good suggestions are put forward for consideration, it is an entirely different matter.  Knowing the difference saves one's sanity in this passionate hobby.

Thank you for the positive responses and indulging me.  I have been on Audiogon for a bit and have always enjoyed seeing the sharing and camaraderie.  My hope is new comers to our community on Audiogon get a chance to read this for its true intent. Our younger brethren don't care to participate due to the contentious berating and that is a tragic shame.  

Best to all...
Oh, they are Cary Audio SLA70s in monoblock configuration, which Dennis Had custom built for me just after he opened his company in Cary, NC. I was one of his first customers. He is a fellow Ham and I bought the amps and a SLP-70 which he heavily modified also with his RPC circuit, right down to the Peter Dahl. Spooky transparency. I was running the amps with 8 ohm Celestions before I bought the Magnapans. If Magnapan said I needed to alter them, I would have sent them back to Dennis. He wasn’t a fan of planars but respected my passion for them. Good guy, that Dennis.
I don't know whom at Magnepan you talked to, but the 3.7 "6-8 ohms throughout the audible range"? Nope, it is 4 ohms over most that range, dropping to 3 ohms at some frequencies.

The original version of the Tympani T-I (which I owned in the 70's) was a nominal 8 ohm load, but Magnepan re-engineered later Tympanis to 4 ohms (my Tympani T-IVa are), and all subsequent Maggies have been as well.

Fortunately the load is---unlike ESL's---almost purely resistive. It's not a difficult load, but Maggie lack of sensitivity coupled with it's modulus of impedance (the fancy term ;-) makes it a power sponge. While tube amps do work with Maggies, high-power tube amps are costly to buy and own. Low sensitivity/impedance loudspeakers eat power tubes for breakfast, lunch, and dinner. Lovers of Maggies and tube amps solved that dilemma in .6 and earlier models (which have parallel cross-overs) by bi-amping---using a high power amp on the bass driver, a medium on the midrange drivers and tweeters. In the .7 models Magnepan switched to series cross-overs, which cannot be bi-amped without surgery on the speaker.