ampers - I’ll chime in here. The Benchmark AHB-2 has been my go-to amp for about 2 years now. It is unique in my experience for simple authenticity. Regarding their feed-forward, John Siau has written a white paper available on the BM website. In practice, the correction mechanisms are nearly invisible and inaudible. Under overload / clipping conditions (evidenced by the indicator lights), I can hear no artifacts of any kind. The error-correction compares the input signal with the projected output signal and introduces correction before the final power stage. When pushed ’too hard’ the output interrupts momentarily as though the offending peaks are erased, but with no audible distortion, mute indicators light up momentarily - and the music continues. I have purposely pushed the bridged amp into sub 2 ohm loads (two paralleled CS2.2s.) The over-current lights flicker on peaks and eventually the amp shuts down via overheating. No damage, no audible distortion, just safety shut-down waiting for manual restart in a few minutes.
Don’t try this at home. But my experience is that the AHB-2 is bulletproof for itself and its driven load.
In my large room, I run out of power in stereo mode and therefore use 1 bridged amp on each channel. Unlike class AB amps, the bridged distortion graphs match the stereo graphs. But output impedance is double (damping factor is half). Half-length cables makes up for much of the difference.
Considering the relative bargain price of the AHB-2, my dream configuration (seconded by John Siau) is 4 bridged AHB-2s -each channel getting a bridged amp for the woofer and another bridged amp for the combined midrange - tweeter. Power requirement is about equal, since the headroom required for clean midrange peaks about equals the current draw of the bass.
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My Lucian also doesn’t arrive till December 11 |
I’m picking up my AudioQuest 9 cables this weekend other than that nothing yet. May get more interconnects but as far as speaker cables go I have one for each speaker. The AudioQuest was terminated for the thiels. I chose the 9 for the natural warm timbre without detail smothering. |
thoft
Thank You for the update. Keep me posted as you massage the Luxman into your room/system. Any cabling updates?
Happy Listening! |
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@thoft, sounds like a nice piece for a different application. |
@yyzsantabarbara,
There are different types of distortions. Clipping is the consequence of some distortions.
The Benchmark is somewhat unique, I was wondering just how it’s feedforward mechanism works when confronted with low impedances? Does it reduce power when sensing overload, does it shut down, does it provide some sort of dynamic headroom, does it self correct the distortion ala DSP, or something else?
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@jon_5912, Before I forget, let's remember that those calculations were for a 1 meter distance, not the 3 meter recommended distance. Even allowing for the greater efficiency of doubling the channels, and the typical room gain, in practice we can expect much greater power demands in typical use. |
@yyzsantabarbara,@yyzsantabarbara, “A shame these things cost money.”
Haha😄 |
@unsound Your comment ties in the what John Siau emailed me today. When ss amps clip, it’s sudden and ugly. With ss amps t’s best to keep far distance from the clipping point. John’s last comment in the conversation. Yes, it will work well in your application. The feed-forward error correction keeps the amplifier distortion-free when driving low impedances. Or maybe distortion and clipping are not the same thing? Regarding searching for new speakers. I am very happy with the CS3.7’s I am enjoying the heck out of them now. I am just trying to squeeze every bit of performance, especially in a challenging room. What I have now is great, let me try for excellent which the CS3.7 is capable of. I do want the 2 COAX’s to measure the same though. Need to fix that. I am going to one day build out a living room system. That will be using different gear and the speakers will likely will be the KEF Blade or Yamaha NS5000. Along with the CS3.7 the other 2 are my fav speakers. A shame these things cost money. |
@jon_5912, I think you mean 64 Watts for 102 dB. And one would need 256 Watts for 108dB. Now one would not ordinarily play Thiel’s that loud, but should it happen you wouldn’t have to worry. Ultimate volume levels are a Thiel weakness. For me the Thiel virtues outweighs the compromises, and the speakers that can play that loud are too compromised elsewhere for me. Though not the last word in accuracy, I’ve used a phone app to track my listening volumes in my roughly >3800’cubed room for a few weeks. The average sound pressure was about 85 dB, but there were peaks a few times each day of well over 100 dB.
It’s not the ultimate power of the Krell’s that impresses me the most, but rather the ease in which it handles low impedance loads. There’s nary a strain, and it’s reflected in the sound. BTW, with my >4 Ohm Thiel’s I use a less powerful amp that’s not a Krell. |
@yyzsantabarbara, I’m a firm believer in working backwards: budget, room, speakers, amplification, etc.. But I offer this with sincerity: perhaps your affection (which might be well deserved) for the Benchmark might lead you to more compatible speakers? |
The simple reason I like the Benchmark gear is because with this gear I experience the illusion that I am in the studio or audience during the performance. I think it is their SNR that makes this magic happen for me.
That is also the reason I like the KEF Blades so much. Those speakers bring the performance into my room better than anything I have ever heard. The Thiel CS3.7 are also pretty good in that regard too.
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Let me add that theses impedance loads are typically best served by ss amps. Unlike tube amps, ss amps don’t clip gracefully. When ss amps clip, it’s sudden and ugly. With ss amps t’s best to keep far distance from the clipping point. Fortunately ss Watts are typically much less expensive than tube Watts. Making it much more affordable to avoid it altogether and have the safety of that extra power margin. |
The luxman is fully restored and completely rebuilt with a new transformer boards and etc. it is basically new. I have confidence that “failure prone parts” and “potential noise introductions” are well resolved and don’t even exist. |
Even so, it's 32 watts for 102 db. I appreciate the benefits of extra power but the Krell FPB300 puts 600w/ch into 4 ohms.
64/105, 128/108, 256/111, 512/114. I'm skeptical, do you buy Thiels because you like it loud? They're magnificent with unamplified music at reasonable volumes. I tend to doubt you can have the best of everything in one package. Wouldn't drivers that can play crazy loud need to be built differently than ones that are optimized for detail? |
@jon_5912, That’s not quite correct. They’re spec’d at:
90 dB at 2.83 V 1/m
not
90 dB at 1Watt 1/m
You need to drop the sensitivity by 3dB for each halving of impedance below 8 Ohms.
I don’t know what amp you are using to drive which speakers, but it’s not uncommon for an amp to halve it’s Class A output as it doubles it’s output with each halving of impedance. |
I think focusing on doubling is somewhat misguided. If an amp is stable and low distortion into 2 ohms it should be fine. How much power can it put into 2 ohms? An amp that can put 300w/ch into 2 ohms can put 150 into 4 ohms and 75 into 8. Whatever it can put into 2 ohms is what matters rather than doubling.
With the 3.7s it's hard for me to imagine they need a huge amp. They're 90db sensitive. (Stereophile measured 90.7.) 2 watts for 93db, 4 for 96, 8 for 99, 16 for 102, 32 for 105, 64 for 108, 128 for 111, 256 for 114. I'd be shocked if these can get anywhere close to 114db before exceeding their physical limits. The fairly inexpensive amps I have do the first 30 watts in class A. I'd bet that pretty much all of my listening is in class A. I worry about bottoming out the drivers a lot more than the amps. |
@thoft, the original Krell FPB's ("Full Power Balanced") are designed to work best through their balanced inputs, though if you wanted to direct connect to a high bit, high output DAC the RCA inputs might have an advantage to avoid bit stripping. The latter FPBC's and FPBCX's don't even have RCA inputs; only XLR and CAST.
As far as using an intergraded as a pre, well I suggest using the KISS approach. Your just introducing more potential noise and failure prone parts. |
@yyzsantabarbara , If an amp can't double down into lower impedances, at higher volume levels it can lead to frequency linearity issues. The Thiel's tend to have fairly steady impedance loads, so it might be less of an issue. FWIW, considering everything I'm not sure why you have such loyalty for the Benchmark. Something like the above mentioned Krell FPB 300 would be ideal. The FPB 300 has perhaps a bit of overkill power for your current room, but that's not a bad thing, especially if your considering moving your speakers to a larger room in the future. The FPB 300 is something of a sweet spot model in the line up, a nice step up from the smaller models, due to improved parts such as a bigger tranny. It's sensitivity also makes it a suitable model for direct connection for some of the newer high bit, high output DACS without having to worry about bit stripping, negating the need and expense of a line stage if you don't have analog sources to contend with. The issue with the Krells, perhaps due to their, though modulated, Class A output is that they seem to need recapping more frequently than some of the competition. That's not an inexpensive proposition unto itself and then there's the expense of shipping such heavy gear. Though I think you can conservatively expect 20 years between such servicing. |
Yea it is integrated and only has rca. I’m not too concerned about xlr connections. It’s a beefy unit. I’m getting it to replace the luxman l-450 that i was using as a pre amp even though it’s not meant to be used as one (doesn’t have pre out) |
In a previous post, I described the 2008 COAX terminal connection backwards (not important).
I just got off 2 email threads.
1) The Audio Engineer in Canada, Mitch Barnett, looked at the new graph I sent him and said we know for sure it is now the COAX drivers that have a problem.
2) John Siau from Benchmark looked over the specs of the Thiel CS3.7 and said the amp will work in mono. That is the mono amp will not damage the speaker. I should take the 30 day home trial and see if it actually improves the sound.
3) I will get in touch with Rob and pick his mind on what could be the cause of the COAX issue. |
@thoft Is that an intergated amp? Does it only have RCA outputs? |
I have decided I’m getting a luxman l-510x to be the pre amp for the krell fpb-300. One step closer... |
^i’m happy that you found the source of the problem so quickly. Perhaps sending both drivers to Rob so that they can be properly calibrated and matched might be prudent. |
@unsound Thanks for the feedback.
I was thinking that could be the case. What I did first was put my KEF LS50's back into my room and measure exactly as before. This measurement setup was done with the goal of removing the room as much as possible. The microphone was placed 3 feet directly in front of each speaker and my LEFT and RIGHT test tones were run from ROON. One tone per speaker and the analysis was done on my Windows laptop running REW
With the CS3.7 the Sound Pressure Level (SPL) graph on the REW software shows a lower level on the replaced COAX driver at 1K to 20K.
On my KEF LS50's the same test results in an almost 100% perfect match in the graph lines for each speaker. Beautiful to see that.
So the issue is not with my gear or the testing process. It is now isolated with the 2 COAX's.
The COAX that was originally wired out-of-phase was built in 2012 (there is a date sticker). The COAX on the other speaker also has a data sticker of 2008. It also has some electronic piece that is soldered onto the uncolored terminal (non-RED). A tiny label on the piece says something about 5% adjustment. I took some photos of this and got confirmation from the previous owner that Rob Gillum told him the 2012 COAX does not need this extra soldered piece.
I was not able to reach Rob today but I have a feeling I will have to get a second 2012 driver to make the SPL identical. As I said in my prior post, the sound is really good now. There is nothing I hear that tells me there is a problem. However, I am curious about going forward with DRC so I will replace the COAX if that will fix this issue. This has to be resolved before DRC can be done (at least with the Audio Engineer I am working with). |
@yyzsantabarbara, There are a multiple number of causes that might be responsible for this anomaly (including room). I’d suggest reversing components (speakers and cables) and channels from one channel to the other starting from the end (speakers) to the front of the chain.Then replacing components in the same manner. This might help you find the culprit. |
yyzsantabarbara
any journey worth taking will experience a rough patch or two. Enjoy the music!
Happy Listening! |
This journey I am talking with the CS3.7 is hitting rough patch after rough patch. It is not really bugging me though, a little interesting actually. Learning a ton of stuff about audio. My background is as an expert listener of music. :)
Today I did the REW software measurements of the 2 speakers. The new issue is that the Sound Pressure Level graph of my LEFT and RIGHT speaker are not identical. There is sufficient divergence between the L and R to indicate that something is wrong. This divergence occurs at 1K level. I got this feedback from the Audio Engineer who analyzed the data.
So I am going to learn how to interpret the REW software correctly and measure my KEF LS50s myself to eliminate the very new Benchmark gear as the culprit. I am almost 100% certain this less than 6 month old brand new Benchmark gear is flawless.
I have an idea what the issue is but will not speculate here until I speak with Rob Gillum tomorrow morning. If my hypothesis is correct it will cost me some funds to fix it.
I should note that both COAX drivers are in phase now and to my ears the system sounds great. However, I cannot move forward with the DRC until the SPL graphs are almost identical.
BTW - I was just playing The Boy’s Doin’ It - Hugh Masekela. That sounds so good on the CS3.7 |
@yyzsantabarbara Ok well if you are not considering integrated forget about Gryphon, the separates are too expensive for Thiel owners IMO.Only Diablo 120 or 300 is worth considering for CS 3.7s owners.
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@thieliste I appreciate your feedback. I will give it a try since it is so easy for me being local. I do not want an integrated since my system positioning is setup for separates. I wanted a cleared path from my speakers to my ears. I am very happy with what I have done to facilitate this in a small room. I will check out their dedicated amps instead.
I just did some quick looking at the Gryphon amps and they seem like competitors to the USA made CODA #16.
I am currently listening to Santana’s - The Woodstock Experience and while it sounds very good and I am bopping along. I would like more power to really feel that percussion.
@unsound you are correct about the 25% reduction at 2 Ohms. I asked them since you mentioned it before. I am not a big Class A guy. Whatever gets me to great sound will work, Class A, AB, D, etc.. |
@yyzsantabarbara I completely agree about Luxman being kind of too warmish and meaty.I 've heard the the M900-C900 combo several times and was never blowned away.Gryphon integrated are much more fun, it's very dynamic, transparent, fast, huge slam and still organic and never muddy.It will not cost you anything to just go for an audition and see if you like the house sound and compare to the gear you already know.
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@yyzsantabarbara, The latest Krell’s unlike most of the earlier Dan D’Agostino era separates models are no longer spec’d into 2 Ohms. The newest Krell’s like the original models have returned to forced fan cooling. Something I personally don’t care for. I’ll hazard an assumption that at 2 Ohms those Coda Class A specs can be reduced to 25% of their 8 Ohm Class A rating. |
Great feedback. Some updates. 1)
Rory at Benchmark forwarded my email to John Siau, the amp designer. He has the Thiel CS3.7 specs from Stereophile measurements linked in the email. He is out now but I hope to hear from him once he gets back. 2) I am trying to get my speaker measured again today to send to the Audio Engineer in Canada for the DRC. A lot of crazy stuff happening in the home front (like flooding, no babysitter, etc..) so I need to sneak in some time. I will work with a dealer if I get the CODA as an alternative second amp. This dealer also has Krell. He said the new Krell XD is somewhat like the CODA but even warmer. Though for the cost differential it is a no brainer to get the CODA. As I mentioned before the power specs on the specific model I am referencing #8 is perfect for the CS3.7. There are 3 versions to choose from. This is set at the factory. - 150 watt @ 8 Ohm (first 18 in Class A) | 300 @ 4 | 600 @ 2
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250 watt @ 8 Ohm (first 12 in Class A) | 500 @ 4 | 1000 @ 2
- 350 watt @ 8 Ohm (first 8 in Class A) | 700 @ 4 | 1400 @ 2
The cost is under $6K with 10 year warranty. Another great American company like Benchmark and Thiel. CODA can also customize the speaker outputs for me, to use SpeakON so that flipping my SpeakON ended speaker cables would be a breeze. I would never need to unplug from the speaker end. @tmsrdg Thanks for the follow-up. I thought of your earlier posts on the AHB2 with the CS3.7 and did decided not sell to fund a new CODA #8 because how much you liked it. I figured something was not right on my side and wanted to wait until at least the DRC work. Now it is really a great sound even without DRC. It is shocking actually the difference since the wring was fixed. I now know I have 1 of the 2 best speakers I have ever heard. @thieliste There is the meat to the sound of the all Benchmark stack. It is not the warmish meaty+ Luxman sound but a great sound nevertheless. Not saying one is better than the other. I love both. I have been in the demo rooms of many show with Philip Hanlon of Luxman and now Gryphon fame. I do not think I need to spend at his cost of gear to get the best out of the CS3.7 but until I demo the Gryphon this is an assumption. I must say that I am not a fan of "fat on the meat" sound, just "lean meat on the bone" is fine. Luxman was one of the few that I liked that was tubey and warm sounding, but I did not want to cross that limit of meaty sound. Different strokes for different folks. BTW - In December The Absolute Sound will do a review of the gear I have, maybe minus the AHB2. Which will be good for me to read how other amps work with my stack. |
@yyz,Glad to hear you are enjoying the 3.7s with the all Benchmark setup -- same as I have. Yes, the sound is wide open and glorious. I've never had the AHB2 clip light go on in my 18 x 18 room, even with full-on orchestral music. It's just not an issue running a single amp in stereo mode.
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@thieliste, Depending on the specific models of course, I think the Krells are closer to the Gryphons than the Brystons. On the used market here in the US one could can get Krell separates that perform closer to the Gryphon separates for less than the price of a Gryphon integrated. Too often in this hobby brands become victims of their own previous success's. They lose the mystique of their elusive exclusivity, and undeservingly become shunned upon by the snobs. |
@Jafant, sure an amp that doubles down from 8 to 4 Ohms is satisfactory enough for a speaker that operates within that load. For a speaker that operates below that, it’s a matter of physics and the necessary electrical engineering to navigate it. After that it’s a matter or taste. I’m not out to burst your bubble, after all the point of all of this is to seek joy. You believe what you want, spend your money as you see fit, but it’s hard to argue with the facts. |
@yyzsantabarbara By musicality i mean organic, meat on the bone , engaging, the opposite of cold, thin and sibilant.This is the type of amp you need for 3.7s to sing.I would rather get the smallest Gryphon amp as opposed to Krell or Bryston for instance.If you live near the US Gryphon distributor he would probably glad to invite you for an audition of the Diablo 120 at his place. https://onahighernote.com/about-us/ |
yyzsantabarbara
I have found that the best approach to a Thiel loudspeaker, allow your ears to guide you. Specs are helpful to a degree. Specs are not the only aural factor up for consideration, IMO. I believe that we can all agree on an amp that doubles down in power rating from 8 to 4 ohms. The rest is a matter of taste. 2020 has been a banner year for Integrated amp(s).
Until last year, I would have never given the notion, a second thought.
My AYRE integrated is a killer and musical as separates for more money.
Happy Listening! |
Thanks for the feedback. I am not sure what musicality means but I do know that gear like the Luxman m900u have a softer presentation of the sound. Likely like the Gryphon but with the Gryphon having more slam. The USA distributer of Gryphon is local to me. I am sure I will hear their gear next time there is a big show in my area.
I am participating in a HPA4 preamp/headphone amp thread on another forum and someone there is saying the same thing about the HPA4 which sounds exactly like the AHB2. Too neutral no magic, etc... It is just a matter of taste.
Now I loved the sound of the Luxman m900u. I also love the totally different sound of the AHB2. Both are amazing at what they do. The CODA #8 or #16 is described as being similar to the Luxman but with more slam. The CODA is a ton cheaper in the USA with a 10 year warranty. So that is why I have mentioned the CODA so often. I can also get it customized with some SpeakON speaker connector to make my amp switching task with an AHB2 a breeze.
The AHB2 will always be part of my collection. It is a brilliant amp. Some may not appreciate its naked sound but I love it. It sounded the very best today after the out of phase fix I mentioned previously. I wonder if I would have even noticed that problem with another amp? |
@yyzsantabarbara IMO in your small room even a used Gryphon Diablo 120 would be a significant upgrade over your AHB2.In terms of musicality Gryphon is in another league IMO.Just my 2 cents.I myself am waiting until a used Diablo 300 pops out to jump on it and will therefore get 3.7s.Best to you.
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@unsound Yes, I am paraphrasing his comments in my email with Benchmark. I am just crossing my T's and dotting my I's before I close the door on the mono AHB2.
I have been looking around the net for alternative amps, if 2 x AHB2 is a non-starter, I keep coming back to the CODA #8.
I am trying to figure out why people have recommended me to get more Class A first watts instead of more Class AB watts at 2 Ohms with regards to the CODA #8. I guess I can always circle back and discuss again with these folks.
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@yyzsantabarbara , see tomthiel's recent comments on this very subject. |
Great info thanks.
I will likely hear back from Benchmark that mono is not doable with the CS3.7. Your comments give even better reason to look at other options.
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I was not specifically pointing at the Benchmark. The Benchmark's are a somewhat unique, but perhaps not enough to be a clear exception. Most amps when bridged into mono don't like working into lower impedances. Benchmark does sort of dance around a 4 Ohm nominal recommendation when used in mono configuration. The 3.7's despite claims to the contrary are really below a 4 Ohm nominal load. When taking the reduced sensitivity of 2 Ohms into consideration, it's 259 Watts 2 Ohm rating would comparable to about 65 Watts of power into 8 Ohms. That might be enough in a small room, but if you push it, it might lead to driver damaging clipping. Those 2 Ohm power ratings can often misleadingly appear to be providing tremendous power, but when one considers the reduced sensitivity it's really not all that much to work with. |
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@unsound I hear you. I have very good sound now, I cannot stop listening. However, I think there is still another level I can get with more power. I sent Rory Rail at Benchmark an email asking about a second AHB2. I know 2 AHB2 and the CS3.7 has been discounted on this thread but I wanted to get confirmation from Benchmark before I close the door on that.
I forgot how fast the C3.7 sounds. Just an incredible speaker. I am incredibly happy I went with the CS3.7 over the newer speakers I had demoed and liked a lot. I love the CS3.7 sound, it just feels correct. |
@xyzsantabarbara, Yes, for a small room you can get away with less power. But, it’s at 2 Ohms where you need it. The 3.7’s don’t just visit that impedance, that’s where they live. What you don’t need is massive amounts of power at 8 Ohms; they don’t go there. Keep in mind that 2 Ohms loads are about 1/4 as sensitive as 8 Ohm loads. It’s all about what the amp can do in the actual working conditions at hand, all else is moot. |
yyzsantabarbara
Thank You for the update. After a few listens to the MoFi- let me know how the 2 discs compare in sound quality.
Happy Listening! |
@jafant I ordered the Mofi version of Santana’s Caravanserai. My current SME version now sounds better on the CS3.7 than on my Meze Empy headphones. It sounded better on the headphones prior to my speaker repair today.
Looking forward to the MoFi version since you say it is the better version. |
