[casique09]

Hello,

I am fairly new to the "tube" world, but would like to start learning its ins and outs with the hopes of being able to soon setup my very first own rig. I have the following mid-entry model on mind "Nobsound 6P1 6.8W x 2 Vacuum Tube Power Amplifier; Stereo Class A Single-Ended Audio Amp," and I am convinced that I want to go the DIY way for speakers. The amp only has 6.8w thus I need a set of high sensitivity speakers and I was thinking about "GR Research's X-LS Encore Kit." Has anyone tried this particular or a very similar setup? Or, do you know off hand if these type speakers will work or not with the Nobosound amp? As you can see, I am trying to keep it simple and withing a novice budget, because I am sure I will change my initial setup once I get deeper into the craft thus I do not want to start spending lots of money during the learning stages.

Hope anyone can help... have a good one.

Luis

[FullRangeMan]

According the GR Reseach site the X-SLS Floor standing version of this model cost only $11.50 more, this bigger cabinet may be useful or more bass.
Version
X-LS Bookshelf
X-SLS Floor standing version ($11.50)
The X-SLS version of the kit includes additional wire. The X-SLS option adds $11.50 to the kit cost.

[planet10]

The biggest matching issue with a typical Single Ended tube amplifier is not the low power, it is the highish R_out. This means that the FR of the system will be affected by the interaction of the highish R_out and the speaker’s impedance.

More important than the sensitivity is the impedance. An 88 dB loudspeaker with a flattish impedance will work better than a 95 dB sensitive ludspeaker with a roller-coaster impedance curve.

Like that un the kit you are looking at:



This loudspeaker is very unsuitable for a highish R_out loudspeaker system.

This is often why you see SEs matched with single FR loudspeakers (particualrily those with low VC inductance (usually they have a copper polepiece cap).

If you are going to DIY a speaker, it will likely not be your last. Start simple, abd learn.

What kind of budget do you have?

dave

[FullRangeMan]

Great post Dave.
This year I realize the way to go with small tube amps are the oldfashioned vintage recipe used since 1920/30s til the 1950(when transistors amps arrive) which are 16Ω Full Range drivers not 8Ω as usual today, 8Ω speakers are suited to Solid State amps.

[Docere]

The biggest matching issue with a typical Single Ended tube amplifier is not the low power, it is the highish R_out. This means that the FR of the system will be affected by the interaction of the highish R_out and the speaker’s impedance.

More important than the sensitivity is the impedance. An 88 dB loudspeaker with a flattish impedance will work better than a 95 dB sensitive ludspeaker with a roller-coaster impedance curve.

Have you seen measured the output of a SET amp into that type of load? I haven't; however, I have seen the measured FR of a SET amp driving a woofer with a damping factor of circa 3.6. I don't know the exact details of the woofer, sadly. At woofer FS, the amp had a mild 1/2 octave wide hump with a peak at 1dB (not a typo) and a gradual climb from 500Hz peaking again at 20kHz (where the test jig stops measuring), at roughly 1dB up from where the climb started. That is pretty mild and would probably be swamped by the speaker's own FR aberrations and certainly swamped by room effects. Even with a damping factor of 1.8, the hump was broader and more apparent at FS, with a sharp peak at 4dB: not great, but still not as severe as room effects. I'm moderately confident that with a well designed, zero feedback SET amp, the impact of impedance swings on frequency response is not as great as some people suggest. That said, yes: ideally, I'd prefer a more benign impedance than shown, because those impedance swings might just have other effects I'd prefer to avoid (distortion?).

This year I realize the way to go with small tube amps are the oldfashioned vintage recipe used since 1920/30s til the 1950(when transistors amps arrive) which are 16Ω Full Range drivers not 8Ω as usual today, 8Ω speakers are suited to Solid State amps.

Can you explain your rationale, FRM?

[Tyson]

This is why I prefer SET amps to drive only the midrange and tweeters on speakers, and leave the bass duties to a dedicated SS amp.  Like the GR Research Super 7's I have, or their NX-Otica and NX-Treme, or from another company, the X3 and X5 from Spatial Audio (I bought the X3 for my 2nd system).  If you remove the bass load, and then give them high efficiency mid/tweeter drivers with a benign impedance, the SET amps can REALLY shine. 

[FullRangeMan]

Can you explain your rationale, FRM?

As SolidState amps dont work well with 16Ω speakers they introduced the 8Ω speakers as the new standard in audio at that time, also tube amps work better with 16Ω Full Range drivers but after all these years 16Ω speakers are somewhat rare, however I could connect two FR drivers in serie to 16Ω if they are 8'' or smaller.

[Docere]

As SolidState amps dont work well with 16Ω speakers they introduced the 8Ω speakers as the new standard in audio at that time, also tube amps work better with 16Ω Full Range drivers but after all these years 16Ω speakers are somewhat rare, however I could connect two FR drivers in serie to 16Ω if they are 8'' or smaller.

Why does a (zero NFB) tube amp work better with 16 Ohm speakers? If using an amp with a transformer and 8 Ohm taps, you will increase the reflected load on the tube, increase damping factor, and reduce distortion and power - on balance, possibly a good thing with amplifiers seeking to maximise "power" (an issue exacerbated in amplifiers compromising their output transformers). The situation changes if the amplifier and speaker are designed as a system: the operating points and load of the amplifier output stage are well-considered, the output transformer well designed, and the speaker designed for use with a specific amplifier output impedance. When using SET amps, unless the system is well-considered, performance it is a bit of a crapshoot... which brings us back to the OP's questions.

Hello,

I am fairly new to the "tube" world, but would like to start learning its ins and outs with the hopes of being able to soon setup my very first own rig. I have the following mid-entry model on mind "Nobsound 6P1 6.8W x 2 Vacuum Tube Power Amplifier; Stereo Class A Single-Ended Audio Amp," and I am convinced that I want to go the DIY way for speakers. The amp only has 6.8w thus I need a set of high sensitivity speakers and I was thinking about "GR Research's X-LS Encore Kit." Has anyone tried this particular or a very similar setup? Or, do you know off hand if these type speakers will work or not with the Nobosound amp? As you can see, I am trying to keep it simple and withing a novice budget, because I am sure I will change my initial setup once I get deeper into the craft thus I do not want to start spending lots of money during the learning stages.

Hope anyone can help... have a good one.

Luis

Sorry Luis, I got a bit off track in this thread. I agree with Dave's earlier advice (if for slightly different reasons) to suggest a speaker with a more even impedance impedance... and something generally well accepted as working well with SE amplifiers. I'm not sure what is out there at present; Pi Speakers 2-ways could be a good starting point, or a decent (but not expensive), simple wide-range/full-range build (Dave can help with that). There will be many other options, I'm sure.

I think your plan to start conservatively and learn is a good one - it can be more fun that way.

Good luck!

[FullRangeMan]

Why does a (zero NFB) tube amp work better with 16 Ohm speakers? If using an amp with a transformer and 8 Ohm taps, you will increase the reflected load on the tube, increase damping factor, and reduce distortion and power - on balance, possibly a good thing with amplifiers seeking to maximise "power" (an issue exacerbated in amplifiers compromising their output transformers). The situation changes if the amplifier and speaker are designed as a system: the operating points and load of the amplifier output stage are well-considered, the output transformer well designed, and the speaker designed for use with a specific amplifier output impedance. When using SET amps, unless the system is well-considered, performance it is a bit of a crapshoot... which brings us back to the OP's questions.

The output transformer is fed by the output valves and the power supply.

[planet10]

SS amps typically do not have issue with 16Ω. Just less power.

A tube amp will typically have to have a matching transformer which woul dneed a 16Ω tap.

dave

[Docere]

The output transformer is fed by the output valves and the power supply.

I don't understand your point, sorry. Can you please explain what you mean and how that relates to my post?

[FullRangeMan]

I don't understand your point, sorry. Can you please explain what you mean and how that relates to my post?

By the little I know my two cents are>
Valves like to work in an infinite impedance environment, a suitable environment for an OPT would be 16 ohms as the hey days engineers had chosen a century ago, IMO an OPT with 8 ohms output already is a compromise, it causes a certain strain on the output tubes, mainly when we consider a glorious sound 2A3 tube delivery only 1.5 Watt and 4 ohms even more, not to mention the darling 1626 at 0,75 Watt of pure bliss.

You are right in not trust me, my personal opinion is that at this item in question we should trust the engineers of the early days of audio, those guys really knew what they were doing, if they chose 16 ohms and not 8 ohms there are excellent reasons for it.

As the tubes we are using today yet are the same their decision still fully valid mainly with OTL amps, as always IMO.
Hope this help.

[Docere]

By the little I know my two cents are>
Valves like to work in an infinite impedance environment, a suitable environment for an OPT would be 16 ohms as the hey days engineers had chosen a century ago, IMO an OPT with 8 ohms output already is a compromise, it causes a certain strain on the output tubes, mainly when we consider a glorious sound 2A3 tube delivery only 1.5 Watt and 4 ohms even more, not to mention the darling 1626 at 0,75 Watt of pure bliss.

You are right in not trust me, my personal opinion is that at this item in question we should trust the engineers of the early days of audio, those guys really knew what they were doing, if they chose 16 ohms and not 8 ohms there are excellent reasons for it.

As the tubes we are using today yet are the same their decision still fully valid mainly with OTL amps, as always IMO.
Hope this help.

It is not about trust - I honestly did not understand your point.

So, you are saying that because it was done that way a century ago, that is the best way now? The chosen reasons for using 16 Ohm speakers a century ago could be due to any number of things.

I like a moderately high load on my output tubes for lower distortion and better damping factor, but a really high or "infinite" load would impractical (even if possible) for an output stage. With the right transformer, I can reflect onto the tube same load with either a 4, 8 or 16 Ohm speaker - the tube sees the same load. How is the tube being more "strained"? If a transformer engineer can make a really good 5k:16 Ohms transformer, but fail to achieve similar performance at 5K:8 Ohms, they should probably look for another career.

The nice thing about a 16 Ohm speaker is that it will generally it will require less current to drive; but, I don't think that makes or breaks a system by a long shot. And, if used on an 8 Ohm tap, the load reflected to the tube will be double that of an 8 Ohm speaker, which for inexpensive amps designed to maximise power, is probably a good thing (lower distortion, better damping factor).

[FullRangeMan]

It is not about trust - I honestly did not understand your point.

So, you are saying that because it was done that way a century ago, that is the best way now? The chosen reasons for using 16 Ohm speakers a century ago could be due to any number of things.

I like a moderately high load on my output tubes for lower distortion and better damping factor, but a really high or "infinite" load would impractical (even if possible) for an output stage. With the right transformer, I can reflect onto the tube same load with either a 4, 8 or 16 Ohm speaker - the tube sees the same load. How is the tube being more "strained"? If a transformer engineer can make a really good 5k:16 Ohms transformer, but fail to achieve similar performance at 5K:8 Ohms, they should probably look for another career.

The nice thing about a 16 Ohm speaker is that it will generally it will require less current to drive; but, I don't think that makes or breaks a system by a long shot. And, if used on an 8 Ohm tap, the load reflected to the tube will be double that of an 8 Ohm speaker, which for inexpensive amps designed to maximise power, is probably a good thing (lower distortion, better damping factor).

So basically you are saying the engineers of the past were dumb.
As the laws of physics have changed since the old days of the last century 16 ohms are now obsolete, also Iam not aware the latest vacuum state advances.and not able to answer your questions.
But I would like let my suggestion that 16 ohms speaker still worth a listen for small tube amps and OTL.

[Docere]

So basically you are saying the engineers of the past were dumb.
As the laws of physics have changed since the old days of the last century I am not aware of the latest vacuum state advances.and not able to answer your questions.
But I would like to let my suggestion that 16 ohms speaker still worth a listen for small tube amps.

I’m not at all saying engineers of the past were dumb - how do you get that from what I posted?

And I never doubted that 16 Ohm speakers are worth a listen - they most definitely are. I don’t think they are the only option though.