ARC VT80SE with KT170 tubes: audio art without artifice

[godofwealth]

WBF readers might know my current obsession with Soundlab speakers, in particular the large 9-foot G9-7c model has become my reference loudspeaker. It’s usually paired in cooler weather with a pair of monster ARC 750SE’s, which are GOT fire-breathing dragons that use 18 KT150 tubes per channel. In summer months, this monster is not a viable solution and has been retired to its cave, so I was looking for a cooler solution. After much deliberation I got an ARC VT80SE, not expecting to like it much as it has1/10th the power. But to my surprise this is a really terrific amplifier that drives my SL’s extremely well. It has all the richness I want from a tube amplifier and while it doesn’t have the dynamics of the 750SE, it’s not too shabby in that department. Best news is that it allows tube rolling since it uses ARC’s auto-biasing circuitry. A huge drawback to the 750SE is that it ONLY works with ARC branded KT150s, an expensive lesson I learned the hard way.

So, after checking with ARC, I tried the VT80SE with KT170 tubes, and I like them a lot. A bit more power and quite a bit more refined in their sound. Amplifier sound is very dependent on the loudspeaker. My SL has an impedance of 30 ohms in the bass. A modern Wilson has a bass impedance of 2 ohms! The two loudspeakers are like cheese and chalk: entirely different. So, caveat emptor if you use a different loudspeaker.

The KT170s are still breaking in, but after a week or so of listening, I’m impressed. The VT80SE is still in ARC’s lineup. Another reason I like it: its simple and elegant design. I don’t want “ghost” meters or blue meters or flashing lights, thank you you very much. My 750SE’s have analog meters. By turning the amplifiers sideways, I ignore them. The VT80SE thankfully has none of this nonsense. It is auto biasing, so no need to have a dancing meter. Highly recommended for those looking for a slice of ARC magic at a relatively lower price. It’s art without artifice. An ARC classic.
‘

 

[Steve williams]

do you use subwoofers with your Soundlab speakers. IOW what do you use for your deep bass

 

[godofwealth]

I have a pair of REL G1 Mk2 Gibraltar subs, which REL refers to as a sub-bass system as they down to under 15 Hz. But I use it sparingly as the SL G9-7c goes down to mid 20s on its own. Of course, as an electrostatic, its bass sounds different as it’s a dipole transducer. The bass is not as strong with the VT80SE as it is with the 750SE. There’s no substitute for power ultimately.

SL makes its own bass units that are quite large. I can’t fit them even in my large listening room. This picture is from Chris’ house in Japan, who is an SL distributor who installed my G9’s. Keep in mind the scale. Each panel is 9’ in height and over 3’ in width. You need a lot of space to get deep dipole bass.

 

[Steve williams]

You don’t really believe your speakers go that low. They are panels and panels don’t move sir. There’s no way you’re getting bass that low. Deep bass is something you feel as well as hear as deep bass moves air That’s why I gave up on panels years ago. There is no deep bass You might hear something but I’d be hard pressed to believe they go that low. Simple physics I’m not knocking the speaker as they are indeed wonderful but imho you need subs to deliver that bottom octave. You should use the Rel. They are very good subs

 

[Kvali1]

I have the sound lab g7-5c , I have heard the sound lab g9-7c as well at Dr Vinyl, they are amongst the greatest speakers out there ; mine really came to life with proper amplification. I currently use the mosfet AGD solos , I never was a class D believer until I heard these agd , Alberto Geurra is a genius and these amps sound like tube amps . These electrostatic speakers in my opinion are in a world of their own, they do indeed articulate great bass, it’s fast and tight , I won’t argue with how low it goes albeit I do believe they go plenty low ; but what’s more important is that it feels and sounds real .
Challenges with SUBS is you will never get it to match the speed of the electrostatic speaker, even REls. You can do it sure , if you want that very low rumbling feeling but even in a good room and perfectly set up it’ll feel artificial compared to what the sound lab do.
The sound lab just need a lot of power , they sound ok with decent amps but once you give them power they truly shine. Dr Vinyl who has an excellent ear has them paired now with the AGD solos as well.
Congrats on your system and enjoy !! Share pics !

 

[godofwealth]

You don’t really believe your speakers go that low. They are panels and panels don’t move sir. There’s no way you’re getting bass that low. Deep bass is something you feel as well as hear as deep bass moves air That’s why I gave up on panels years ago. There is no deep bass You might hear something but I’d be hard pressed to believe they go that low. Simple physics I’m not knocking the speaker as they are indeed wonderful but imho you need subs to deliver that bottom octave. You should use the Rel. They are very good subs

Well, the SL G9-7c have over 3000 sq inches of radiating surface per speaker and they can play pretty loud — the maximum recommended amplifier output is 600 watts and the speaker is 90 dB efficient. I don’t play my system very loudly but believe me, these stats are not like my Quads. They go plenty loud and the bass is very deep. But I take your larger point that dipole bass is not the most effective way to generate deep bass.

A good sub can generate a lot of deep bass and be much smaller in size. But you are giving up bass quality in the bargain. Standard subs have very high distortion — 5-10% THD is not uncommon. With the large SL’s, you’ll perhaps get less bass but at far lower distortion levels. Now, that’s a tradeoff you’ll have to decide for yourself whether it’s worth making. As it turns out, from Fletcher Munson curves of human hearing, we are much less sensitive to distortion in the bass. Our hearing gets much worse at low frequencies. So, perhaps high distortion in the bass is not that noticeable.

 

[Steve williams]

whenI got into audio in a big way my very first speakers were panels. I loved them as the sound was so pure but as I grew in the hobby the shortcoming was that panels simply dont move air and the botttom end was glaringly deficient . I added subs with some degree of success but never perfect and I moved on. The Soundlabis indeed are an enormous speaker but I believe youre losing the realism of s dynsmic bottom end.

 

[Kvali1]

whenI got into audio in a big way my very first speakers were panels. I loved them ss the sound was so pure but as I grew in the hobby the shortcoming was that panels simply dont move air and the botttom end was glaringly deficient . I added subs with some degree of success but never perfect and I moved on. The Soundlab is indeed an enormous speaker but I believe you're losing the realism of s dynsmic bottom end.

And I do agree that for example an amazing speaker like Zellaton can bridge those gaps , but the newer sound labs with good amplifications are not like any other panel , I’ve heard asylvox and clarysis many times and your observations are correct the always are missing something but soundlab defy all logic and just sound great.

 

[Steve williams]

And I do agree that for example an amazing speaker like Zellaton can bridge those gaps , but the newer sound labs with good amplifications are not like any other panel , I’ve heard asylvox and clarysis many times and your observations are correct the always are missing something but soundlab defy all logic and just sound great.

Panels don't move air. The sound is wonderful but thin IMO

 

[Adam L]

WBF readers might know my current obsession with Soundlab speakers, in particular the large 9-foot G9-7c model has become my reference loudspeaker. It’s usually paired in cooler weather with a pair of monster ARC 750SE’s, which are GOT fire-breathing dragons that use 18 KT150 tubes per channel. In summer months, this monster is not a viable solution and has been retired to its cave, so I was looking for a cooler solution. After much deliberation I got an ARC VT80SE, not expecting to like it much as it has1/10th the power. But to my surprise this is a really terrific amplifier that drives my SL’s extremely well. It has all the richness I want from a tube amplifier and while it doesn’t have the dynamics of the 750SE, it’s not too shabby in that department. Best news is that it allows tube rolling since it uses ARC’s auto-biasing circuitry. A huge drawback to the 750SE is that it ONLY works with ARC branded KT150s, an expensive lesson I learned the hard way.

So, after checking with ARC, I tried the VT80SE with KT170 tubes, and I like them a lot. A bit more power and quite a bit more refined in their sound. Amplifier sound is very dependent on the loudspeaker. My SL has an impedance of 30 ohms in the bass. A modern Wilson has a bass impedance of 2 ohms! The two loudspeakers are like cheese and chalk: entirely different. So, caveat emptor if you use a different loudspeaker.

The KT170s are still breaking in, but after a week or so of listening, I’m impressed. The VT80SE is still in ARC’s lineup. Another reason I like it: its simple and elegant design. I don’t want “ghost” meters or blue meters or flashing lights, thank you you very much. My 750SE’s have analog meters. By turning the amplifiers sideways, I ignore them. The VT80SE thankfully has none of this nonsense. It is auto biasing, so no need to have a dancing meter. Highly recommended for those looking for a slice of ARC magic at a relatively lower price. It’s art without artifice. An ARC classic.
‘

Do I understand correctly that ARC blessed using KT170's with the VT80? Given that the power transformer gets pretty damn hot already with KT150's I was worried about the long term risk of the higher current draw of the KT170's.

 

[godofwealth]

Yes, ARC sanctions the use of the KT170s with the VT80SE. They’ve tested it in the factory. They personally prefer the sound with the KT150s. But that’s a decision influenced by what speakers you use. In my case the KT170s work well with the G9-7c’s. In any case, it’s a relatively inexpensive experiment since you only need four output tubes. They don’t need to be sourced from ARC. I also got the optional grill cover with mine. It makes for a nice clean look.

 

[godofwealth]

Panels don't move air. The sound is wonderful but thin IMO

This is a longstanding debate that goes back to the original Quad ESL released in 1957. You’re ignoring the huge mismatch in impedance between the physical mass of surrounding air and the physical mass of a woofer cone. A panel Mylar membrane is so light that it perfectly couples to the mass of the air. It doesn’t need to move much at all to generate deep bass. You just need a big panel.

A woofer cone has to move a lot in comparison because the impedance mismatch means it needs to move a lot and push the air like a pump. That movement is unfortunately a huge problem because the more a woofer cone has to move, the more nonlinear it gets, and the higher the distortion.

Panels move air but as a paddle, not a pump. Peter Walker himself wrote at length on this topic. With a dipole, you also get a figure of eight radiation pattern. That’s actually a good thing as standard dynamic speakers often overload a room with their bass output. If you measure a subwoofer, as I have done many times, you get pretty nasty peaks all over the place. Even loudspeakers with a big woofer cone can generate a lot of bass output that is hard to control. I have a pair of Harbeth Monitor 40.1’s that sounds way too bassy to my ears on many recordings.

On the other hand, my Klipsch La Scala horns use a large 15” woofer cone, but it’s designed for low distortion and high efficiency. It’s wrapped up in a folded horn-loaded chamber that has such a long effective mouth that the impedance mismatch coupling problem between woofer cone mass and mass of the surrounding air goes away. Paul Klipsch was a firm believer in low distortion. He argued that you don’t have to have the woofer cone move at all if you make it very efficient. The La Scala 15” woofer is 105 dB efficient, over 20 dB more efficient than the average dynamic loudspeaker. That means the cone doesn’t need to move much at all to produce bass and no surprise, the La Scalas have very low distortion in the bass. The tradeoff is that there is no low bass. You only get around 40 Hz or so, but it’s quality bass, not the subwoofer mushy bass. But the La Scalas are big and heavy. 200 pounds and 24” inches deep for a loudspeaker that doesn’t go below 40 Hz might strike many as a bit bizarre, but you’re getting very high dynamic range at low distortion.

To sum up: loudspeakers are a challenge to design as there is no free lunch. You have to optimize for some parameters, but you give up on others. Want small size? You have to settle for high distortion. That’s a tradeoff. All these cute small loudspeakers that claim to have low bass have very high distortion. There’s no way around that given the laws of physics.
,

 

[Steve williams]

I get it. I was into panels for years until I realized there is no bottom end. Explain how you might but deep bass is something you hear and feel. With panels this simply does not exist. Not knocking SoundLab which is a wonderful speaker but they cannot reproduce the lower register. It was this basic fact that ended my love affair with panels.

 

[godofwealth]

I think I understand what you mean, and at some point felt that way too, but over time I realized this is an audiophile urban legend you have to mentally work around. Deep bass of the type you want doesn’t exist in the concert hall. This Friday I’m off to hear the San Francisco Symphony play Stravinsky’s Firebird conducted by Esa Pekka-Salonen. I have a side box seat right adjacent to the orchestra. I’m sure I’ll hear plenty of bass and dynamics, but it’s not the boom-boom bass produced by box loudspeakers. That sort of bass to my ears sounds artificial. Even pipe organ music in a church, which has plenty of deep bass, bears no resemblance to the bass dynamic loudspeakers or subwoofers produce. It’s not one note bass. A double bass played on its own is musical. I heard a chamber concert in San Francisco in a couple of weeks ago in late April that featured a rare piece for four double basses by Bottesini. Lots of bass, but not the subwoofer chest thumping kind. That’s an artificial effect created for audiophiles. It doesn’t exist in a hall in an unamplified setting. Of course, in rock and roll with amplified concerts, you can put in crazy levels of bass.

I remember back in the day when Harry Pearson was running Absolute Sound, he’d work himself into a frenzy trying to figure out if the subway trains running under Kingsway Hall in London — where many famous Decca and EMI recordings were made — were audible with a particular loudspeaker or preamplifier or phono cartridge. Those select components that could reveal if the trains were running north-south or east-west got a special check mark. I find this sort of audiophile nonsense amusing, but it has no musical value to me. I hear a recording for its musical value. I’m listening now to a lovely Linn high res recording of Stamitz flute trios. 99% of music lives in the midrange. Not in the deep bass. I can do without that.

But I realize that I’m in a small minority. Most audiophiles crave the type of bass you desire. Hence the use of subwoofers in almost every audio system, cranked up to crazy levels. I rarely turn my REL’s on. I don’t find them to hold any musical value. I should get rid of them at some point.

 

[Steve williams]

There’s a saying that you get the bass right and the rest falls into place.
We’re going to have to disagree on this one as you can rationalize all you want but once again panels do not move air and without that your bass is thin I don’t use subs in my system. I’m not saying chest thumping but there is some thing palpable with realistic bass and panels do not have this. This is not an audiophile thing but reality.

 

[Kvali1]

Well said . I’m with you .

There’s a saying that you get the bass right and the rest falls into place.
We’re going to have to disagree on this one as you can rationalize all you want but once again panels do not move sir and without that your bass is thin I don’t use subs in my system. I’m not saying chest thumping but there is some thing palpable with realistic bass and panels do not have this. This is not an audiophile thing but reality.

When you are at the symphony , opera or a live jazz quartet .. what is this air movement you talk about?
There is only realism.
And nothing creates realism like sound lab.

Why does air need to be moved ?!

I do agree that we have to agree to disagree , and like so many things , this ultimately is a subjective matter. We are all saying the same thing just saying it slightly differently.

There is a reason we keep saying Zelles are closest to electrostats …. The holy grail ultimately is full range electrostats … how close we get to that is up for debate .

There is no right or wrong here , we are all blessed to be enjoying amazing systems!

 

[Steve williams]

As I said Soundlab is a remarkable speaker but the bass is thin. .

 

[Steve williams]

There doesn’t need to be chest thumping. Think of being at the orchestra listening to an organ play.
Tell me your skin doesn’t bristle when the organ plays. I submit panels dont do this. When I first got serious into audio I owned electrotstats and loved them. I still do. But at the end of the day the bottom line is panels dont move air and you need that for a realistic lower register. I’m not arguing. Merely stating fact

 

[Kvali1]

There doesn’t need to be chest thumping. Think of being at the orchestra listening to an organ play.
Tell me your skin doesn’t bristle when the organ plays. I submit panels dont do this. When I first got serious into audio I owned electrotstats and loved them. I still do. But at the end of the day the bottom line is panels dont move air and you need that for a realistic lower register. I’m not arguing. Merely stating fact

I agree! , goose bumps and that music washing over you effect so far in my life I’ve had with Wilson’s xvx , big sigma acoustic and the zellaton statements; very cool indeed.

 

[godofwealth]

There’s a saying that you get the bass right and the rest falls into place.
We’re going to have to disagree on this one as you can rationalize all you want but once again panels do not move air and without that your bass is thin I don’t use subs in my system. I’m not saying chest thumping but there is some thing palpable with realistic bass and panels do not have this. This is not an audiophile thing but reality.

It's funny to hear you say that. Alan Shaw, who designed the highly praised Harbeth line of speakers, said you get the voice right, and everything else falls into place. Legend has it that his breakthrough in cone design came about as he was trying to accurately reproduce his daughter's voice.
I think most loudspeaker designers feel that the midrange is where the music lives. Of course, bass is profoundly important. But, to me, bass quality is far more important than slam or physical presence. I tend to get a little sick if I hear too much bass. I don't like it personally.

I think different loudspeakers tend to have distinct radiation patterns. You react differently to them. Some folks love the sound staging you get from mini monitors. There's a reason the original Kef LS 3/5A's sell for 5-7 grand on eBay. This is a shoebox sized loudspeaker. Some folks swear by horns, which never had much bass to begin with, but they have crazy dynamics and you can drive them with 1 watt.

I used to own B&W 800 Diamonds, and drove them with a big Krell 700cx monster. Those do produce crazy slam and dynamics, but ultimately I felt the sacrifice to the midrange and coherence was too much. The tweeters on those stick out like a sore thumb.

Large-scale dynamic speakers can be fun to own and listen to, but unfortunately, as I said, there's no free lunch. You have the crossover coloration, the fact that different drivers are producing the sound that needs to be tailored into a whole, and the ear quickly latches on to the cabinet coloration, the crossover coloration and the energy storage in the cabinet. Once you hear that, you cannot unhear it. It's like an aftertaste that is on every recording.

So, I'm happy to trade all that away for the sheer coherence of the large SL, with one panel that produces all the frequency spectrum from deep bass to high treble. Here's a writeup of the SL G9-7c from CAF 2024. The reviewer uses the word "natural". That sums it all. There's no need to divvy up the sound into pieces. It simply sounds like no other loudspeaker does to me. There's a veil that is lifted. As to deep bass, well, as I said, I'm happy to trade that away for so much in return. I can always plug in my big REL G1 Mk2 subs, if I feel the need to rattle my walls.

Sound Lab G9-7C ESLs | CAF 2024

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