@tomthiel, While Benchmark’s class leading distortion specs are truly impressive, their use of non-standard standards is curious. One has wonder if the difference between the vanishing low distortion measurement standards of the Benchmark compared to the 1% standard measurements is more academic than of practical use to the consumer. I’d be more impressed if Benchmark would spec in writing their power delivery into load with a reduced distortion criterion, than to avoid addressing whether it can deliver the goods for my application. While I don’t doubt your reporting what you’ve been told, the cynic in me doesn’t buy what they aren’t willing to put in writing.
It has bee quite obvious that Stereophile doesn’t measure amps into 2 Ohms unless the manufacturer specs their amps into 2 Ohms. And even then they often only do the 2 Ohm measurements from one channel, even when a stereo amp shares power supplies between the 2 channels. One might question whether or not Stereophile is more concerned with avoiding embarrassment to potential advertisers than providing useful guidance to its subscribers? And if manufactures spec their gear in such a way as to avoid the exposure?
That the Benchmark uses what appears to be a rugged protection circuitry is nice in that it prevents an over stretched Benchmark from causing further damage down the line. Some manufacturers go out of their way by over building their gear to eschew protection circuitry because they believe the use of which has negative sonic characteristics. To be fair the Benchmark’s exemplary noise and distortion measurements might put that argument to rest. Still, I wouldn’t want my automobile or even my washing machine to shut down because it was overstressed, and given the choice after sitting down for a nice recreational listening session, I’d prefer to be able to avoid protection saving shutting down altogether if possible.
The Benchmark comes in at the minimum suggested 100 Watts per channel power rating at 8 Ohms for many Thiels, and struggles to keep up below that 8 Ohm rating, there is no extra power to start with to offer some wiggle room below. A Benchmark could be generously compared to an 80 Watt per channel amplifier that could truly double down. And as we know how the sensitivity decreases with impedance, I don’t think that’s an unfair comparison. The above is regard to it’s stereo performance. In bridged mono mode the Benchmark might be excellent for insensitive speakers with a high impedance load, but as spec’d doesn’t appear at all appropriate for low impedance speakers. The price for the Benchmark for it’s performance within it’s limitations is favorable, but for the similar money there are other options that might be better suited for some Thiels.
t
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I recognize that these claims run counter to everything we know about amp behavior.
Ha! Exactly.
What are we going to believe --spec abstractions or our lying ears?
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Here's the AudioScience Review
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usound - Thank you for your thoughts. I share your concern about the power ratings, especially into low impedance loads like the (maddening) Thiels. To learn more about the discrepancy between the AHB-2 non double-down performance vs. my intensive auditioning experience with it, I engaged John Siau in conversation. Among the lessons Iearned was Benchmark’s eccentric power measurement protocol which goes like this:
They rate the amp at 0.0003% THD+N into all loads. In other words if it doesn’t shut down, that running spec is met with no allowance for additional distortion. The amp exceeds that 3 zeros spec at the power limits you cite (which obviously decrease into decreasing impedances.) But, if the traditional 1% THD+N spec were used, it would double-down as we want and as I (among others) experience it doing. It sounds and acts like it is doing what John says it is, and BM is very conscientious about its claims. Their internal tests go to 1 ohm continuous and their customer service tells me they are viable to 1/2 ohm resistive loads. All Thiel models are extremely resistive via Zobel networks on all drivers - which push the amp limitation from distortion-limited toward heat-limited. I have shut down the AHB-2 via overheating, but it required louder levels than my comfort zone. Admittedly, my installation maximizes radiation and convection cooling. When John evaluated the load graphs of Thiel models considering phase and impedance, he recommended stereo-only except for the CS7/7.2 = stereo or mono. Due to the BM feed-forward distortion reduction the only advantage of bridged mono is 4dB greater headroom before shut-down, no increased distortion as in all other amps.
I recognize that these claims run counter to everything we know about amp behavior. Have you seen any second-party lab tests using the traditional 1% distortion limits? I would love to see those results. Note that I (among others) have requested a higher-output AHB-2, but John is firm that ’it isn’t necessary’. Perhaps from BM’s perspective of primarily pro market and inability to meet demand, he has a point.
Note I am not arguing that better and more suitable amps aren’t out there. I imagine they are. My personal situation is needing an amp that drives the loads while telling the truth. The AHB-2 does that for me, at a price I can afford.
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@tomthiel, the impedance limits of an amp depends on the speakers attached to it. Most later floor mounted Thiels from the 1.7's / 2.3's / 3.6's / 5's / 6's / 7's have a minimum power recommendation of 100 Watts per channel into 8 Ohms. The nominal impedance of all these speakers is at least 4 Ohms. We all know the actual minimum impedance can be less than that, and quite often for more than just a slight dip.
Models | The Coherent Source (wordpress.com)
The Benchmark amp in stereo mode is spec'd at 100 Watts per channel into 8 Ohms and is not able to keep up with doubling down even into 4 Ohms, just missing the minimum recommended 200 Watts into the nominal impedance. Things get a bit worse as we work down into actual minimum impedances, as rather than reaching the recommended 300 Watts into 3 Ohms the Benchmark comes up short at 240 Watts per channel. In Bridged mono mode the Benchmark isn't even spec'd below 6 Ohms.
Benchmark AHB2 Power Amplifier - Benchmark Media Systems
With the right speakers the Benchmark might well nigh be the most perfect amps available. They might work beautifully with some older legacy Thiels, or with the Thiels that are not floor standers, but I think there are more suitable options for the more recent Thiel floor standers.
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I think you're right to question where in the chain to try to fix or compensate for problems in music reproduction. It would seem to make sense to fix things as far upstream as possible, but that isn't always easy to do.
With regard to Nelson Pass, I watched a YouTube video of an interview he did with Steve Guttenberg that mentioned the distortion profile issues briefly. Nelson was careful to state that he didn't actually add second or third harmonic distortion to some of his amps. Instead, he simply chose not to suppress those lower order distortions as much as he could have in the circuit design.
For my own listening, I don't look at ultra-low distortion specs in an amp as a sign of sonic purity if those specs are associated with any harshness or brightness in the sound quality I hear at the downstream end of the chain. But adding in a lot of extra distortion doesn't seem like an ideal design strategy either.
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Funny side note
I was looking at HiFi equipment sales in Portland Oregon
and at Fred's sound of music they still have Thiel Audio
listed under New Components !
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sdl4 - distortion profiles are intriguing. More generally various forms of aural masking are intriguing. The aural cortex does somersaults to create the mental image we call ’hearing’. The entire chain from live event to listened experience is convoluted. I am committed to Jim’s approach that those factors are the business of those links in the chain. Unraveling and/or compensating for such problems downstream carries its own down-sides. Many products do just that: compensate for upstream deficiencies. One cost is that some sort of signal resolution or fidelity suffers. Philosophically, I would prefer Nelson to work on reducing upper-harmonic distortion rather than masking it with added lower harmonic distortion, which is more distortion, not less.
I should insert a life-long noticing that distortion is quite often a preference, in sound as in much of life.
I’ll also add that DMP’s founder Tom Jung used CS5s as mastering monitors because they helped him find and minimize those upstream artifacts which conversely would remain invisible via masking by downstream products in the service of ’sounding better’.
More later.
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jafant - No retail space in the cards. Open studio space still a couple of dim possibilities. Workspace is materializing a little at a time.
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tomthiel
Good to see you this Spring Saturday. Have you found a new retail space for Hot Rod Garage II ? Or a studio space? I hope that you are well and enjoying research and development (R&D).
Happy Listening!
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In small bites. Jim chose the big Krell FPB600. Other muscle amps no doubt 'outperform' the AHB-2. I like the 'grunt' of my bridged Classé DR9s (1100 watts / 2ohms.) Bill Thalmann is presently hot-rodding them. And Nelson Pass is a hero of mine. So then, what's my AHB problem?
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Thanks guys, IMO a single Coda#16 would easily outperform 2 AHB-2s driving CS 3.7s.
Anyway i will start by demoing the Gryphon Essence stereo pre-power combo and see how that goes against my Diablo 300.
Since i now have Cardas Clear Beyond IC and SC in my system this has brought my Diablo 300 Thiel CS 3.7 combo to another league, absolutely insane level of performance!
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@tomthiel Thanks for the detailed response to my questions. You may consider yourself an electronics layman, but you still know a lot more about this stuff than I do.
Given that the 2.2 appears to be easier to drive than the 3.7, it sounds like the AHB-2 should have enough power to handle my 2.2s if I decide to try one. (By the way, my room is about 3800 cubic feet, though with some large openings on two sides.)
I'm still trying to learn more about the distortion profiles of amps and their audible effects. The Benchmark website has a lot of interesting info on its products, and I even understand some of it. Jon Siau at Benchmark talks about providing electronic compensation to reduce second and third harmonic distortions (through their DAC, I think) as part of the attempt to reduce all types of distortion as much as possible. In contrast, Nelson Pass says that his listening tests at Pass Labs have shown a general preference by many listeners for the sound of amps that don't work too hard to suppress lower order distortions. Ralph Karsten at Atma-Sphere says that second and third harmonic distortion is not annoying to most listeners and actually helps mask the higher order distortions that give so many solid-state amps a harsh or overly bright sound. Siau, Pass, and Karsten are all highly regarded designers who use both measurements and listening tests to design their amps.
On the surface, it would seem best to reduce all distortions as much as possible, and this appears to be part of Siau's approach. On the other hand, there seems to be general agreement that the harmonics in recorded music reproduction are not identical to the natural harmonics in real-life musical instruments. This raises the question whether sound would seem most natural and real if all distortions are as low as possible or if the harmonics profile of the gear used to play back recorded music needs to come closer to matching the harmonics profile of real instruments. This sounds like a situation that will demand some actual listening!
Thanks again for your help in thinking some of this through.
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I tried and almost loved the AHB2 with my Thiel CS3,7’s. I tried a single AHB2 in stereo and also 2 in mono. My room is small so I thought the lack of power at 2 Ohm region with the AHB2 would be OK. On most music the sound is incredible. However, with some very powerful music I felt like it was missing some grunt.
I emailed John Siau at Benchmark about the low imeddance ability of the AHB2 with the CS3.7. He said it would be great. I think it can be bettered with a more powerful low impedance amp.
I am keeping my Benchmark stack downstairs with my KEF LS50’s, a LA4 preamp, a DAC3B, and AHB2 amp (need to re-buy a 2nd AHB2 later). This will be used with a KEF Blade META much later in the future. The Blades are not as hard to drive as the CS3.7.
On the Thiel system I tried many amps that were better at 2 Ohm. These included the following:
- LSA Voyager GAN 350 (modified by EVS)
- Parasound A21+
- CODA #8
- KRELL Duo 175XD
- D-Sonic M3a 800s.
All these amps had more ’grunt’ with the music I found the AHB2 lacking. I only have the CODA #8 and the KRELL 175XD left on the Thiel system. I rotate the 2 amps between my RAAL SR1a headphones and Thiel CS3.7 speakers. I am finding it difficult to take the KRELL out if the Thiels because it sounds so good, 175 watts in Class A. However, I will force myself tonight because I want to hear the RAAL again with the KRELL.
BTW - the modified LSA Voyager is very similar sonically to the AHB2 but with more overall power (better for Thiel). I kept the CODA #8 over the Voyager mainly because I already had the AHB2 and preferred it over the Voyager with the LS50s.
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Unsound - what do you consider the low impedance limit of the AHB-2?
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@unsound
I have no problem with massive orchestral works -- Bruckner, Mahler, Stravinsky, Carter et alia playing at concert level through my 3.7s in my 21x20x8' listening room. My two AHB-2 amps don't even blink.
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^The Benchmark amps are at the very top when it comes to a lack of distortion within their load tolerance. They are also somewhat special in that their input allows for a variability that is somewhat uniquely accommodating for system matching. Regrettably, many Thiels have impedance loads that is outside the window of ideal operation for them. The Benchmarks are not designed to work optimally with many Thiels. While I'm hardly the one to make such a supposition, I don't believe that Jim Thiel would have traded his Krell for the current (or lack thereof) Benchmarks. They could very well be the very best amps for different speakers.
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tomthiel wrote " your 03 woofers are Eminence and I would love to know the model numbers on those".
Yes, the "67" in the date code indicates the manufacturer is Eminence. Markings: 10KZHG8GX Date Code: 67-7920
I'll send you more info/photos soon. Thanks!
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tmsrdg - yes sir!
sdl4 - remember, I’m an electronics layman
1. Yes, an AHB-2 should drive your 2.2s. Medium-size and real-world are vague and subjective terms, but here’s why I say yes. The (clipping) protection circuitry is so fast and sophisticated that I can see the lights flickering without hearing any dropouts. That takes 100dB in my functionally rather large room. In case you don’t know, my room was weird. I built a resistive-wall (leaky) 4000 cubic foot room within an 11,500 cubic foot floor of a 38,500 building with various openings between the floors. Virtually no modal interactions, but hard to characterize its "size" since the direct space was moderately sized and the larger spaces were acoustically secondary. All that said, my preference and regular use mode was each speaker driven by a bridged AHB-2. But, a single stereo amp was adequate for moderate (85dB peaks) listening.
2. The AHB distortion profile is extremely clean, but I lack technical fluency regarding your specific question. I point you to the Stereophile and AudioScience reviews, among others, to see their qualitatively (stunningly) low distortion. It took me some time to realize that the bass balance was not thin or dry. Other amps (of my experience) add harmonics, especially noticeable in the bass. On a related note, the Benchmark DAC3 and Preamps-4 take additional measures to reduce second and third harmonic distortion. John Sieu’s essays on Benchmark’s site are quite informative.
I don’t know the Atma-Sphere amps, but I do know that the Benchmark class H topology acts differently than do ’normal’ amps, even full class A. JS sent me some distortion graphs illustrating that the 1 ohm profile is virtually identical to the 8 ohm profile. No, that’s not normal, and no, I can’t lay my hands on those graphs or explain the technicalities. But, yes, the amps do sound that way. With JS’s coaching, I rigged an experiment to account for my initial perception of ’better’ sound in stereo than bridged. The output impedance drops to half, lowering the damping factor. I shortened the speaker cables from 12’ (stereo) to 6’ (bridged) and the SQ difference seemed to vanish. This THX amp topology is amazing as tmsrdg said - all that weirdness goes away leaving only the music. Sorry to gush, it’s just hard for me to believe.
BM has a generous return policy in case their power doesn’t meet your needs. Or, if your budget can be stretched, two of them make for serious audio nirvana.
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Jeff - you may be in for a big treat! If your woofers are indeed mis-wired, that wreaks havoc with the phase coherency of the whole system. The most certain way to get it right is to get a 6 volt battery (lantern) or 9 volt is OK for woofer with a short-duration test. Connect + to + and the cone should move outward. If wrong, change the leads. I think your 03 woofers are Eminence and I would love to know the model numbers on those. Likewise for the mids and tweeters if you don't mind.
Regarding tweeters, I (seem to) recall the 03 was Polydax and the 03a was Audax which may have been an upgrade or a merger, etc. Rob at CSS may have a more definitive answer. Stay away from an old tweeter. They wear out via fatigue of the tinsel leads. Let us know what you learn.
The silliest question is the necessary one unasked.
TT
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@tomthiel I know you have a lot of experience using the Benchmark AHB-2 with Thiel CS-2.2 speakers, and I'm hoping you can answer two questions about the AHB-2:
1. Are you satisfied that the AHB-2 has sufficient power to drive the 2.2s with ease in stereo mode under any real-world listening conditions in a medium sized room?
2. Do you know what kind of distortion profile the AHB-2 has in relation to second and third harmonics compared to higher order harmonics?
Distortion profile is an issue that Nelson Pass has studied a lot in relation to Class A and A/B amps, and it is also being discussed in relation to Atma-Sphere's new Class D amp that uses GaN-FETs. The Atma-Sphere amp is supposed to have the sweetness of a tube amp with lower distortion, greater transparency, and better masking of higher order distortions. The Atma-Sphere amp has similar power ratings to the Benchmark amp at both 8 and 4 ohms.
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Gotta second Tom's Benchmark rec. That's all you need and the end of the story. I run all Benchmark with my 3.7s. It has completely reoriented my ideas about endlessly looking for the right tweak/cable, amp and etc. Of course, I used to do that. But it seems like such a weird waste of time now, not to mention money. All these people looking to color the sound in just the right way. There may be yet new caps and resistors for the speakers, but that's another story.
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Questions regarding tweeter replacement & driver polarity.
I recently discovered that one of the tweeters in my Thiel 03s is outputting at a diminished volume. In order to troubleshoot I swapped the tweeters between the 2 speakers and the problem persists with the same tweeter, so it’s not the crossover or something else. I looked online and found what appears to be an identical tweeter (Audax brand, the original is Polydax, see link at bottom of post). Has anyone had experience with these replacement drivers? I’ve also found vintage Polydax drivers on eBay but I’m concerned about their wear and tear/condition.
On another note (sorry if this is a silly question): All 3 drivers in my 03 should be wired with the same polarity, right? In my exploration I discovered that the woofers are wired out of phase with the mid and tweeter. The woofers where removed at one point for re-foaming so maybe they where reinstalled in error.
https://www.madisoundspeakerstore.com/audax-soft-dome-tweeters/audax-tw025a1-12x9-1-textile-dome-tweeter-with-ferrofluid/
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I recommend getting the Benchmark AHB-2 into your auditioning mix if you can. Once I latched on to its clean, quiet capability, all the way to 1/2 ohm load, I have gotten hooked. Just sayin'
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@unsound Just trying to compare my Diablo 300 to the newer Gryphon Essence Monos.
My dealer can lend me the Essence stereo and pre to try out in my system so i can make a shootout against my Diablo 300 but no one has the Mono versions for me to try.
My guess is that the Essence stereo might run out of steam compared to my Diablo 300 but i could be wrong.
My room is medium size.
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@Thieliste, it depends on the model Thiels, room, desired volume levels and the particular amplifiers in question. While Class A has advantages with regard to cross-over distortions over Class AB, there’s more to good sound than that alone. Furthermore, many so called "Class A" amps lose Class A output in proportion to increased power output into lower impedances. It's not uncommon for some Class A amps to halve Class A output with each doubling of power output into halving of impedance load. For example, one might have an amp rated as providing 55 Watts per channel of Class A power into 8 Ohms and be able to double down into 2 Ohms to provide 220 Watts of power. If we put such an amplifier on a speaker say with a sensitivity rating of 90 dB @ 2.87V with a minimum load of 2 Ohms, the Class A output of that amp into this speaker at 2 Ohms might be less than 14 Watts and that would be at a 2 Ohm sensitivity of about 84 dB. One can see that it might be quite easy to power out of Class A output and into Class AB power output. The advantages of low output Class A amp might be better appreciated with a speaker with a higher impedance load. On the other hand there are other considerations that might demonstrate that a lower impedance might be more beneficial, just perhaps not as much as with many low powered Class A amps.
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@duramax747
PM me at rsr no space 921 at live dot com about CS2.7
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I posted an image of my upgrade 2.7 woofer board , tag = Thiel scrolled down almost the last system .
I'd say that I am hearing a more forceful and/or quicker low end , one that doesn't weaken or roll off as it goes lower .
A lot of work and this was the easy board to work on !
Also the screws holding the boards contained iron , replaced with brass .
@pieper1973
Sorry to hear about your mishap , are you going to repair or replace ?
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Guys i have a question regarding amp power to max out Thiel speakers.
Is it better to have 300W A/B stereo doubling down to 2 ohms with 136 000 microfarads of capacitance or 55W pure class A Monoblocks doubling down to 2 ohms with 880 000 microfarads of capacitance ?
Thanks.
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thieliste
Good to read that the newer Cardas offerings are a sonic match for CS 3.7 loudspeakers. I am on-the-record reporting that Cables do make a difference.
Happy Listening!
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😭😭
I killed my amp yesterday😭😭
It is actually my own fault. I readjusted my room and put the amp underneath something else. This may have seriously impeded airflow, the unit was red hot when it failed..
So now I have to listen to music on my phone through a desktop speaker system.. at least it's something..
Happy listening y'all 😉
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Signal cables do make a huge difference from one brand to another with Thiel speakers at least in my experience with my 3.7s.
I have gone from Gryphon VIP IC and SC to Cardas Clear Beyond IC and SC.
The difference is night and day, Clear Beyond cables are in a league of it's own.
The synergy with my 3.7s is mind blowing, never heard such level of weight and clarity in the bass region before.
Musicality is second to none, same with depth, soundstage, air, texture and so on.
Best cables i've ever heard to date by a wide margin and i can even say best component upgrade i've ever done in my life.
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^I too have often (perhaps too often) gone on record record here on my strong preference for sealed boxes, not only for bass output, but for overall coherence as well.
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You are correct - I didn't cross-check my rusty memory. The CS3.5 bass in its enclosure is 'critically damped' Q.5 for no bass hump, which some critics consider 'dry' or over-damped.
Also my apologies for my final statement of 'excellent in every way'. I meant that the bass configuration was optimized for performance in the phase, time and frequency domains. In particular the EQ'd sealed bass keeps the fundamentals in time with the upper harmonics, whereas reflex bass places the (reflex-supported) fundamentals a full cycle behind the rest of the signal. Lots of controversy around whether such bass coherence can be heard or matters. I'm among those who say it does 'to me'.
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Thanks Unsound, your thinking makes sense to me.
Re bright Thiels, it was the one thing I didn't like when I first got my 2.3s, but it can be tamed. For me it meant that each and every upgrade/improvement had address this, and room treatment amd arrangement (rack to the side wall), careful speaker placement (including height), speaker cables (AZ Holograph, thanks Eric Squires!), and Isoacoustic GAIAs all helped in different ways, the clincher was upgrading the digital source (went with bel canto 3.7). All the while I was rolling tubes, and one thing I have learned to appreciate is being able to hear most (not all) of these little changes. One reason I went for Thiels in the first place as a newbie audiophile was bc of their reputation to be very revealing of the signal, as TT mentions above. I knew I'd be cycling through equipment cables etc and wanted good chances to be able to hear the differences. Thiels have delivered!
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Thanks for all the information you share here, Tom!
Just to get on the right side of Thiele & Small, the term "critically damped" refers to a total system Q of .5, and "maximally flat" refers to the more commonly used .707 Butterworth configuration, which is slightly underdamped and is tuned to use a 3db hump in the bass response to lower the -3db point.
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@petaluman - the 03a was a sealed box design which produces a 12dB/octave bass rolloff. I think the tuning was .707 Q which Jim considered critically (properly) damped and some call overdamped. I don’t remember the unequalized -3dB point, but a fit curve could be overlaid knowing that the EQ curve was 12db/octave with the peak centered at 30Hz and then reducing symmetrically to zero boost. I would guess the upper blend point would be around 100Hz. So, without the EQ, your bass will roll off at 12dB/octave below that blend frequency. With the EQ, you get critically damped flat response to 30Hz, then rolling off at around second order. Excellent bass. The EQ did not add cut, it merely ceased adding boost.
The Thiel eq was discrete circuitry and neither the EQ or any Crossover had op amps. However there was an aftermarket product called "Golden Flute" built in a brass tube and powered by a wall wart which used op amps to achieve the same goal. I have heard that they were well liked and successful; but I know nothing about their particulars.
I know of no hot-rodded versions of the 03a EQ. I do know that the CS3 EQ, which performs the identical function, was more sophisticated in its circuitry and execution. And that the subsequent CS3.5 was the first generation to be direct-coupled with no capacitors in the signal path. The 3.5 had variable cutoff points at 20Hz and 40Hz to side-step troublesome deep bass room modes if necessary. The 03a and CS3 families are conceptually the same product - with the addition of the Coherent Source nameplate. Even though the woofers are different, their Thiele/Small parameters and enclosure size are very similar. An EQ for the 03a, CS3 or CS3.5 would work for your 03a as would Golden Flutes for any of those same models. The 01/ 01a/ 01b also has the same 30Hz x 12dB boost and would work. Avoid the model 03 EQ, since that was both ported and boosted, so its parameters are different. I am working on a 3.5 EQ upgrade for significantly better performance than stock.
The EQ transforms the speaker from significantly bass shy to excellent in every way.
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@tomthiel Thank you for your recommendations. My ear level is about 36". My room has a lot of limitations, but has a fair amount of absorption and diffusion. There is an equipment rack between the speakers.
I really like the 3.6s, but I need to love them to keep them. Rob at Coherent Source Service gave me a couple of things to check out to make sure they are functioning properly.
If they are, they may just not be a good match for my system and room.
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I saw the recent references to the 03/03a Thiels, and had a question. I have a pair of 03a speakers, which came to me without the equalizer. My understanding is that they only provide a bass boost to lower the -3db point. Would anyone know what the unequalized vs equalized response curves looked like? Or at least the -3db points. Did the equalizer return to flat at still lower frequencies (relying on the natural 12db/octave rolloff), or did it add additional rolloff at 6 or 12db/octave?
Also, I've seen the crossover schematic with the op amps. Are there any hotrodded versions of the 03a equalizer?
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big_greg -I agree with Cascadesphil that Thiel’s can be more sensitive to input signal than most brands. In my opinion, that has more to do with their coherence allowing the ear-brain more scrutiny. But that discussion is beyond the scope of this response. Let’s assume that your signal is fine.
You stated your listening distance as 9’, which is fine. Design distance is 10’, and the closer you get, the more critical your ear height becomes. The propagation triangles have to resolve at your ear. Design ear height is 3’. If you sit high, you will get a treble-heavy and non-time-aligned wavefront. That’s a design constraint of phase coherence with multiple drivers and why Thiel gravitated toward coax treble sources in later models - with their own issues and challenges.
Another critical factor is early reflections, which likewise become more critical in a coherent design. The speakers are designed as point sources with very broad, even dispersion characteristics. As such they require at least 3’ between the tweeter and any reflective surface. Side-wall reflection is most often a culprit; absorption at the reflection point helps - a lot. Similarly, a low ceiling and/or hard floor can be problematic. In a small room, consider a long-wall layout.
Note that Thiel’s tonal balance is tuned for listening off-axis. At design setup the ear is 20° off-axis which is where the power (in-room) response matches the direct response. That straight-ahead position requires at least 3’ to a side wall, more is better, and absorption helps. In my experience most people aim them slightly inward to mitigate side-wall reflections. My experience is that straight-ahead with narrower speaker to speaker placement solves the issues better. Such particulars of setup are far more germane to performance than are particulars of equipment (unless grossly inappropriate.)
Thiels are articulate and precise, and for those who appreciate that, they can be very musically engaging. Many speakers are designed to be forgiving of problems - Thiels are not. Our goal is to faithfully reproduce their input signal - unvarnished. Much like a recording environment must be carefully optimized to capture a proper record of the recorded event, the playback environment must also be optimized. In the hi-fi hobby I believe we could create far more satisfying musical immersion by working on our environment and setup rather than looking to gear changes.
Keep the faith - the results can be wonderful.
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big_greg wrote" If there are other suggestions to tame them, I’d love to hear them."
A gentle amount of EQ will work wonders.
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I've owned a few Thiel models. The newer ones (e.g. 3.7s, 2,7s) don't seem as sensitive to cabling as the older ones (I've owned besides the 3.7s, the 2.3s and the 7.2s). In addition, when my friend worked at the high end shop in the early 2000s, for about a six year period, I did virtually all his set-ups and installs with him (and those where all pre 3.7s by a few years, 1.6s, 2.3s, 2.4s, 1.7s, 6s, 7.2a). The 3.6s do have a reputation for sounding bright as do some of the other earlier models (not owned or heard them personally), I almost went into the cable making difference and have had numerous secondary (non-Thiel) systems currently and in the past. Many times a cable would make a bigger difference on my old 2.3s for example and something I could barely tell if there was a difference on something like my B&W P6s. So from my experience (but nothing as old as the 3.6s - but yes to the 1.6s), some of the older models are the poster children for everything in the chain is important more so than some other brands.
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I read a lot of reviews about the Analysis Plus cables and chose them in large part because they are regarded as neutral to warm. I have other Analysis Plus cables farther down their line in use in other systems and those worked great. Analysis Plus cables are in use for speakers only. The rest of the cabling shouldn’t matter since all my other speakers don’t suffer from this malady.
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Speakers cables or interconnects or both? There's some threads here - e.g.
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What cabling are you using? Sometimes the cables can accentuate or increase brightness. I had a friend complain about that in a system a year or so ago. He ended up changing the preamp from what I recall. I did make him something that tends to be a bit more laid back vs. what he was using cable wise to try.
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I purchased a pair of used 3.6 speakers a few weeks ago and try as I might, they are just too bright to live in my system.
I first drove them with Herron M1 150 watt monoblocks. I bought a pair of Ampzilla 2000 Second Edition monoblocks to see if they would sound better with more power. The dynamics improved, but they still sound bright. The Ampzillas are rated at 300/540 into 8/4 ohms. Stereo Magazine measured them at 390/680 and they are supposed to be stable into 1 ohm.
I put my Harbeth Super HL5 Plus speakers back into the system and they sound sublime with the Ampzillas. They had a little bit of a hard edge at times with the Herron amps, but that is gone with the Ampzillas.
My room is less than perfect, and could be contributing to the issue. The right speaker is near a side wall, but the Harbeths as well as my KEF Ref 1 and Stirling LS3/6 speakers all work great there.
I really like everything about the 3.6s except the brightness. If I could tame that, they might knock out my newer and more expensive speakers.
My options for placement are limited and I'm not going to spend even more on amplification for 20ish year old speakers. I had them about 9 feet from my listening position and just slightly toed in.
If there are other suggestions to tame them, I'd love to hear them. I've also reached out to Rob at Coherent Source Service to see if he has any upgrade or mod options.
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"Do you recall the peak Amperes of the KWA 150SE ? This measurement or Slew Rate are strong indicators on the performance of a Power amp."
There are tons of reviews out there (e.g.
but need to translate it - explains the differences between the 150 and 150 SE)
I'm not aware of any (review) that has detailed measurements. I knew of people who upgraded the 150 to 150SE and there are reported large differences.
The problem with something like that (and remember I still own the LS36.5DM preamp) is of course system synergy. The other problem is that the design is not really new. As with anything, technology tends to improve with age. The 150SE currently lists for $11k. Probably due to its age and other advancing technologies, it doesn't have a particularly good resale value (e.g. just go to hifishark and do a search of sold ones). I'd guess the average sales price is around a third of its current retail. That's fairly low for an audio component that is a current model.
I think that much of the problem is due to the fact that audiophiles have owned it (like me) and tried some of the newer technologies (and my Thiel 3.7s are not an easy load) and realize it is no longer competitive, even at used value. The ultra high end (e.g. well above the current list price of the Modwright) may be a different story. Audiophiles, manufacturers, retail stores, etc., tend to live in the past in many cases. If, for example, they heard an amp of a particular brand and it had a reputation for a particular sound signature in the past (say a decade back, give or take), that tends to stick for a while (I had friends who used to work at retail and that's what they would convey to customers). All I can say in my system, there is no comparison between the modded Voyager I currently own as well as the modded dual mono IceEdge I had before it vs. the Modwright. I've had people over familiar with my system and they concurred.
I think audio wise, down the road, we will be dealing with many more speaker products that are active where one only plugs in the source.
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