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RE: Which Pass Labs power amp for Quad ESLs?

Posted by AbeCollins (A) on May 8, 2025 at 08:17:22

In Reply to: Which Pass Labs power amp for Quad ESLs? posted by George S. Roland on May 8, 2025 at 07:59:08:

"Do you think the XA 25 would give me better sound or is this just a sideways change??"

It could even be a backwards move but someone with Quad experience will hopefully chime in. Can you audition the XA 25 and return it if not satisfied?

I have no experience with Quads but I do have some experience with speakers that are more sensitive than yours yet sounded much better with more power.

- I ran the Class-AB Pass Labs X150.5 on my 91dB sens 6 Ohm nom Tannoy tower speakers. It was a good match and the sound quality was outstanding. I then ran the same speakers on a Pass Labs Aleph 3 which is 30-Watts of pure Class A audio. The sound was smooth and a little warm but compressed or restricted. It was lacking dynamics and it was a little rolled off in the bass and treble. The higher power Class-AB X150.5 brought my Tannoys to life with clarity while the 30-Watt Aleph 3 sounded almost muffled in comparison. Was this a power issue or just the Aleph 3 sound? I don't know but other amp swaps suggested that my Tannoys came to life with a little more power. (For example, the 200-WPC Classe CA-200 vs the 100-WPC Classe CA-100.)

Tannoy Definition D500 : Mfg recommended 30 to 175w RMS. 6 Ohm nom, 4 Ohm min, 91db/m/w sensitivity, 8" dual concentric mid driver (brass tweeter in center), 8" bass driver. Crossover type: 1st order LF, 1st order HF. These speakers sound better with more than the recommended minimum of 30-Watts.

- I wouldn't even consider running 30-Watts of Class-A power on my Thiel CS2.4 speakers. I -believe- the Quads have similar low sensitivity. In the case of my Thiels, they really need more than 100-Watts to come alive.

Thiel CS2.4 : Three-way, floorstanding loudspeaker. Drive-units (all anodized aluminum): 1" (25mm) dome tweeter coincident with 3.5" (114mm) cone midrange; 8" (204mm) cone woofer; 8.5" by 11" (230mm) passive radiator. Crossover frequencies: 800Hz, 2.5kHz. Crossover slopes: acoustic first-order, 6dB/octave. Frequency response: 36Hz-25kHz, +/- 2dB. Phase response: minimum phase, +/-5 deg. Impedance: 4 ohms nominal, 3 ohms minimum. Sensitivity: 87dB/2.83V/m. Recommended power: 100-400W. The Thiels sound better with much more than the recommended minimum of 100-Watts.

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