Thiel Owners

tomthiel

Excellent! Thank you for the link.

Happy Listening!

Adcom power amp comparisons

The two Adcom GFA555s arrived yesterday and I compared them to each other, to the GFA555 II, to Sennheiser HD800S headphones, and to the Benchmark AHB2. Brief report to follow.

A fair prior question is ’why’. My present odyssey includes long-standing riddles among which is why some users experience classic Jim Thiel products as some combination of hard or harsh, up-front, analytical, etc. while others hear little of these issues and love them. Among myriad interacting potential causes are:

• Room, listener position

• Inferior signal chain and/or recordings

• Cable/wire with time-domain problems exposed by phase coherent presentation

• Crossover location behind the woofer. Later progressed to behind passive radiator, cabinet bottom

• Less than best diffraction and wavelaunch control

• Other including high-frequency balance, driver and floor coupling, etc.

Today we’re examining Amplification. These Adcom amps were well-regarded and popular in Thiel’s mid-cycle product development. If some amps don’t like some cables or speakers (such as low impedance). Let’s say those issues are settled with the amps presently under consideration. Historically, Thiel graduated to top-tier amps because we got excellent dealers who used those amps. We never tested our speakers with anything less than the Krell-Levinson league. Even Audio Research and Classe washed out due to Jim’s assessment of off-neutral (AR) or less-than-best (Classé.) Bryston was our 'entry level' recommendation.

My present rack: Reference: All Benchmark stack with AHB2 power amp driven by HPA4 by DAC3B from Philips CD80. Benchmark interconnects. StraightWire Octave II speaker cables.

Known amp: Adcom GFA555 II

New amps: Adcom GFA555 (original) (2) All amps bridged mono

Speakers: Thiel CS1.5 stock

MO: Patty Griffin – Impossible Dream skipped through full album for 10-15 minutes total per amp under test. Album is pop vocal with simple to orchestrated instrumentation, and various pop production effects. Without apology, the Benchmark has become my reference. Adcom 555A is early production. Somewhat up-front, simple, direct, ’no mic windscreen’ sound Adcom 555B is late production. Slightly more ’refined’, ’mic windscreen’ sound. Adcom 555 II. More controlled, safe, less ultimate detail and dynamics. Differences are fairly subtle. Family resemblance is the over-riding quality. Family sound is very similar to HD800S headphones.

Benchmark AHB2. Solid, quiet, clean. Studio reference quality both technically and aurally. Note, the original 555 sounded closer to the AHB2 in their shared direct liveliness, than the MkII. I am sending 555B to Jim Williams for upgrade. Another comparison will ensue on its return. I support with Harry Lavo’s recommendation. The 555 II is the safer bet for unknown upstream components and source material, and within its power capabilities, should drive any Thiel speaker well.

tomthiel

Thank You for sharing this initial data. No doubt you will learn and progress more after JW's Adcom amp returns. Have fun!

Happy Listening!

Happy Friday! All

CS3.5 update

As you know, I've been investigating internal hookup wire this spring and summer. It's been quite a long and winding ride. Among the twists and turns has been learning how some wire configurations interface with other wire configurations - for better or worse. Backing up, I wasn't convinced I was sending a neutral signal to the 3.5s, especially with the equalizer in between the pre and power amp. I took a detour with Dick Hardesty's 'series-bypass' method where a wire (in this case) is added then removed from the feed stream. The result was that some 'upstream' cables just don't like driving a particular 'downstream' cable. I propose that just such a condition occurs when a speaker cable feeds an internal wiring harness. Mismatches abound. The bright side is that this test shone light on which cables are more tolerant of their downstream load, and those cables move higher on my interest list. I'll have some final results to report within a short while. Let's just say what many other commentators have said: excellence doesn't necessarily track price. Today I received a second batch of cable from Iconoclast, which interests me greatly.

I will reiterate what I reported recently. Belden's 4694A is a surprisingly good cable for short money ($30s) . It is sold as a 75 ohm digital coax for ultra high definition video with a 12GigaHertz rating. Indeed it shines in that digital role. But, it also shines very brightly as an analog interconnect. I invite anyone to compare it with whatever you're using, and please report your findings here.

Now, back to the 3.5. I settled on driving the 3.5s with that 4694A Belden digital S/P-DIF, plus StraightWire Rhapsody 3 analog interconnects and StraightWire Octave II speaker cables – single wired. The StraightWire cables hold up very well to competition and I have known them intimately for decades.

Now another tangent. A couple years ago, my first crossover experiments were on the CS2.2. Again, I know it very well, using it for listening and musician / mix / master evaluations for decades. I had reported that removing the crossover from the cabinet, optimizing the layout without the EMF of the woofer, and upgrading many critical components – all combined to produce substantial qualitative upgrade in performance. That 2.2 workhorse is back-burnered via for greater ease and lower expense of using the model 1 with its two-way configuration and shorter wire runs.

My report today regards the unexpectedly large improvement in the 3.5 by simply moving the crossover. No new parts, no new layout, still inside the cabinet. The move is from behind the woofer (very bad environment) to shock-mounted on the bottom of the cabinet.

Over the years, the consensus about the 3.5 (among other Jim Thiel designs) is that it gets 'confused' or 'compressed' when the volume gets high or the score complex. Fair enough. There also are reports of an over-analytic, electronic presentation. Fair enough. The equalizer contributes some of those attributes. But I am using a Jim Williams / Audio Upgrade replacement which rivals most amps that would be used with the 3.5.

The test uses signal from the Philips CD80 through the Benchmark stack with a vetted cable chain (with or without the EQ). That stock 3.5 and its mate with the XO on the bottom are side-by-side, both fed the same mono signal. The modified 3.5 takes on a more lively, vivid, sweeter musicality. Surprisingly so.

The differences got real in the measurements; there have been persistent anomalies in the frequency and phase measurements of the 3.5. Specifically there is a suck-out (15dB @ 80 to 100Hz) and the top octave droops nearly 10dB. The FuzzMeasure sweeps are taken near full scale – just under clipping. Nearfield single driver measurements are taken at far lower levels. They showed no such anomalies. I assumed the 'problems' were in the room. But no. The 'problems' vanish when the XO is moved to the bottom of the cabinet.

Flash back to the 1982 development of the CS3. This very issue was discussed in the hypothetical. We had noted how much purer the sound was before consolidating the XO into the cabinet. But the XO bottom mount was dismissed due to slightly higher labor cost. Hindsight sadly shows that decision to be significant. That 'behind the woofer' mounting persisted until the removable passive radiator in 1995s CS1.5. (The earlier passive in the CS2.2 was built into the baffle.) That particular 'electronic crunch' follows models with the XO close behind the woofer.

Short of all the labor and expense of a full-blown redesigned outboard crossover, there is a lot to gain by simply moving the XO. Very soon, I anticipate having some firm recommendations for hookup wire upgrade. Those wire and XO position modifications provide significant improvement that is accessible to the DIY owner.