Tube amps and speaker ohms

Hi Divad. I tried to post before, but I cannot see the post so here goes again.

First off, I am a very pro tube guy, but I would advise you very strongly against going tubes with your speakers. Your speakers are not suited for a tube amplifier.

You may get them to “work” by using a big tube amp, but it is never going to be a good match and neither your speakers nor the tube amp will be sounding their best. You’ll be much better off with a solid state amp.

If you really want to try tubes, you need to ditch the B&Ws.

Regards
Paul

Bartokfan, you seem to be asking the same, albeit worded differently, question over and over. If you are doing so because you are cautious, then it is a good thing. If you do so because you don’t like the responses you have been getting, it a bad thing.

I am going to disagree with Ralph on both speaker impendence and the power that is required to drive them.

A speaker with a nominal load of 4 ohm should not be a problem for a tube amp. The vast majority of tube amps will have 4 AND 8 ohm output taps, so 8 or 4 ohm rated speakers is not an issue. You simply use the appropriate tap off the back of the amp. Of course, all bets are of if your amp does not have this feature.

Secondly, 40wpc is plenty for an 89db rated speaker. I use a 12wpc SE amp on 88db speaker and the bass is tight and it can pound the walls down. I also use a 22wpc 6C33 based SET amp now and again, and if I had to turn that up my ears would bleed.

My speakers (Meadowlarks) happen to be well suited to tube amps, so much so that I get the best out of my amps. I am sure I get way higher distortion free SPL levels from my speaker than I could, had I been using speakers that are not tube friendly.

Your speakers are going to make or break your tube system, and the choice should not be made based on looking at rated sensitivity and nominal impedance only. I would suggest you talk to the manufacturers of your speakers and get their opinions regarding the use of tube equipment on their products. I doubt any manufacturer will advise you on an amp that will make their product sound bad.

Regards
Paul

+++ Pauly "4 ohms should not be any problem for a tube amp". But in my experience tube amps do not like 4 ohms, especially when the music gets complex, as in orch, even large jazz ensemble is rather thin sounding. +++

All things equal I'd go for a higher impedance speaker, yes, but you are quite mistaken by making an across the board statement that tube amps do not like 4 ohm speakers. Decware has some speaker models rated at 4 ohms that are more suited to tube amps than 99% of all 8ohm rated speakers on the market today, and that no exaggeration.

+++ Push pull's , like SET amps can be picky on what speakers they prefer, for best potential.
I'll stay with 8 ohms. +++

A SET amp by definition is single ended and as such not push pull. I do agree that any tube amp, be they single ended or push pull are picky on what speaker they prefer. Where I disagree with you is that nominal impedance has little bearing whether a speaker is suited for use on tube amps. The actual impedance curve and crossover design are way bigger factors you need to consider.

Regards
Paul

Bartokfan I think you are confusing impedance with sensitivity. Nevertheless, both are factors that influence how well (or not well) your amp will do.

Rule of thumb is to have a speaker with simple cross over design (or better, no cross over), benign impedance curve, high(ish) impedance and high(is) sensitivity.

I will probably get flack from a couple of SET guys for saying this, but I do not believe any single tube is better per se than another at orchestra (or opera, jazz, rock or anything else.). However, not all amps are equal, and some will perform way over what their rated output would suggest they can.

Don’t get bamboozled into buying a huge tube amp to drive tube unfriendly speakers. Get the right speakers and every tube amp will work well (or work as well as it can).

If somebody tells me his speakers worked fine with his 100 wpc plus tube amp but not with his 50wpc tube amp, I run away. That is the speaker I will never want own, even if I get paid to take them. Proper tube friendly speakers will work well with 2 to 3 wpc tube amps.

As far as orchestra/opera goes, I have had good results with all my tube amps on my speakers. These amps were 300B SET (x 2), 6C33 SET, 6550/KT88 SEP, EL34 PP (x 3), 6550 PP, EL84 PP. I’m probably missing one or two, but the point is they all worked great for orchestra because I mated them with the right speakers.

Once you have tube friendly speakers, you can try any tube type and amp configuration and always end with a smile on your face.

Regards
Paul

+++ I googled impedance. Its a load issue +++

If you googled it then it must be true? Okay

Have a look at Decware speakers – they’re all designed to work with 2wpc plus tube amps. Most of them are rated 4 ohms nominal. http://www.decware.com/newsite/mainmenu.htm.

Ultimately it your money and your choice how to spend it. I personally don’t have any issues with orchestral music on my system. And no, I do not have a hearing problem ;-)

Duke, sure there are exceptions (and I did state it as a “rule of thumb”), but the most tube friendly speakers are single driver non-crossover designs. If I may ask, what speakers do you build and are they designed to be used with vacuum tube amps?

Regards
Paul

Ok, here goes.

+++ Paul then you have a SET amp correct? +++

Currently I have only one SET, and that is a 6C33 based one.

+++ Would that be similiar to the 300 tube? +++

No, a tube has little to do with whether an amp is single ended or push pull. The 6C33 is very different to the 300B tube, although both are triodes.

+++ Yes. I heard the 300 tube with orch, the load/complexity was overwhelming. Total shut down of the tube. +++

Nothing to do with the tube. You made a bad choice with speakers. In other words, not the tube doing anything wrong, just you not knowing how to use the the tube amp.

+++A CJ mono block as well shut down on a ML panel with orch. So obviously orch overload is not limited to SET but can affect just about any tube amp, +++

Yes orch can overload any amp. In the same way I can drive any car into any tree, whether the car is a SUV, truck or coupe. No car made in the US today can drive through trees, so when you try to do that, the car will break. However, it is not the vehicles fault for driving into a tree, it is the driver that cannot operate the vehicle correctly.

If you drive the vehicle on the road, it will operate as designed.

+++ which in Push/pull config may have to do with the weakness in the trans. +++

No

+++ In SET's the weakness in "pulling off" orch may have to do with the characteristic of the 300/845/805 tube family +++

No. I have never ever heard this weakness you talk about. My 300B SET amps aced orchestra. I can induce any of my amps to fail in the manner you describe by seeking out speakers that will cause that.

I could also seek out trees to drive into when I drive, but as I rule I prefer not to.

Regards
Paul

David, the best advice I can give you is to talk to a few speaker builders/manufacturers. They will be able to give you very good advice. There a couple on the BB like Audiokinesis who I am sure will be happy to talk to you. A few others are omega, decware, coincident etc.

I have speakers rated at 88db/1watt/1mtr sensitivity that I drive to very loud levels with a 12wpc tube amp. The bass really pounds and I can measure it down to the mid 20’s (albeit at –10db). I can do that only because my speakers are very tube friendly. Some other poster mentioned his 200wpc amp is barely capable with 96db rated speakers – somewhat ridiculous no? If I hook up my 22wpc SET I can blast the doors down.

Regards
Paul

+++ the only way to achieve constant voltage drive with a changing load impedance is by having very low amplifier impedance+++

This statement is not totally accurate.

Constant voltage can be achieved when the amplifier has a relatively low output impedance compared to the speaker impedance AND when the speaker has a benign impedance curve across the frequency range.

In the same manner that some carts require very careful matching with a specific tonearm to perform their best, vacuum tube amplifiers require the same careful attention in matching them to the appropriate speakers.

But then I am not telling you something you do not know already Raul? ;-)

Regards
Paul

+++ We are more interested in which labs are actually producing a tube amp to meet demanding power hungry speakers. +++

The best amp for meeting the demand of power hungry speaker is called a transistor amp. A person attempting to use a tube amp on said speakers is called ignorant (I am being kind)

+++ I am only interested in the end result. +++

No, I suspect you are interested in your own opinion ...

Regards
Paul

David, tubes do sound magic, but not to be a party pooper, you are probably enjoying some of the harmonic colorations. Many folks do find this pleasant to the ear and since you paid for it, there is no reason for you not to enjoy it.

Better suited speakers will give you a much more accurate and natural sound, with less of the colorations. You may at first not enjoy it quite as much, and it may actually sound more like a transistor amp.

A good tube amp setup sound remarkably the same as a good transistor setup. I personally prefer tubes, as to my ear, they achieve the most accurate and natural reproduction of the recorded material. That you will only experience once you get components that work well together.

I think many will agree with me that the process of acquiring the correct components can take many years but is very enjoyable every step of the way.

Enjoy.

Regards
Paul

+++ but since I do not care for ss amps +++

That is sad. The failure you mention your experienced with your tube equipment would not occur had you been using solid state.

I own (and have owned) solid-state amplifiers that are extremely musical and will work on most speakers.

++ I look for certain tube amps that can carry a relatively heavy load +++

These tube amps are not the best sounding tube amps and more often than not, cannot compete musically with good transistor amplifiers.

+++ though even 8 ohm speakers can dip to 4 ohms on huge orchestral challenges+++

Musical genre does not influence speaker impedance. If speakers dip to 4 ohm on Orchestra, they will dip to 4 ohm on every genre of music known to man.

Speakers rated at 8 ohm that dip as low as 4ohm are not suited to for tube amplification if quality reproduction is a requirement.

+++ TRhe point of the topic was to ask the GENERALIZED question that tube amps prefer 8 ohm speakers +++

No it wasn’t. You asked a myriad of questions but not what you state here.

+++ Which is fine. I'm staying with 8 ohms, and thats that.+++

I don’t believe anybody told you not to purchase an 8ohm speaker. Most posters indicated that there are other factors you need to consider also.

Fact is, most of the posters here have system that can do orchestra. By your own admission, your system cannot – and you do have 8ohm speakers already.

Regards
Paul

Raul, I am not going to argue with you, mainly because I do not quite understand your comment. I think this is mostly due to the fact that neither you nor I have English as our mother tongue.

Transistor amplifier have lower output impedances and are therefore much more suitable for the majority (99%) of modern speakers. They can easily maintain a constant voltage against a speaker load where a tube amp will struggle. In the perfect world, vacuum tube amplifier should have speakers rated at 64ohm/128ohm and higher to do so. Hopefully one day I can get somebody to build me speakers like that to fully optimize my tube amplifiers.

I also believe almost all vacuum tube amplifiers are used against speakers where they do not perform well – Bartokfan is a good example of this.

However, you are incorrect if you say vacuum tube amplifiers cannot maintain a constant voltage against a loudspeaker. It is simply a more difficult to achieve.

You are welcome to disagree and I know and respect your view on transistor vs. vacuum tube.

Regards
Paul

+++ Please could you explain how the tube technology can be " accurate " to the recording +++

Sure Raul. Perception of music and the accuracy thereof is 100% subjective. To my ear no amplification device on the planet can come as close to a real piano recital as a SET amplifier.

+++ Normally the tube is a self harmonic generator +++

That is not true. Always the tube and the transistor are self harmonic generators. Transistor generally being much worse, up 70% THD. Amplifiers by design compensate to correct these flaws. My ear prefer vacuum tube solution – for now.

Yes, tube amplifier require much more careful speaker matching as they have much higher output impedance than a transistor amplifier. People who do not understand this better stick with transistor amplification.

Regards
Paul