Shouldn't amp reviews employ multiple speakers?

Yup!..In the same way that reviewers use different amps for a particular speaker..the same should be true of speakers under review employing a variety of amps..

The three responses above confront the issue well. Audio products are designed and voiced with a system of specific components. Assessing any piece of electronics or transducer without realizing the importance of system matching, I find not only unfair, but unproductive.

I have read threads from very knowledgeable 'philes making what they term "true comparisons" of items (from cartridges to amps to speakers), by vitrue of inserting component B into "identical system" of component A. Otherwise stated, amp A vs. amp B in a system which amp A performs well in. Findings may prove amp B lacks some refinement or musicality and susequently, is deemed an inferior product.

Paraphrasing Aball, any and all products may improve or worsen within the company of strangers. That is why I continue to extract the utmost from the system I own, tweaking until no more red can be squeezed from the turnip.

Well -- all the reviewers I know buy their own gear, plus many of them are married and their spouses may not like to see three pairs of different types of speakers in the listening room.

Personally, I have two 2-channel systems set up in two different rooms with different components and when I think there may be an equipment bias issue, I sometimes put the review component into each system to see how the results compare. Not all reviewers have that luxury, however.

As Aball notes, there are just too many combinations of components, wires, and speakers for any reviewer to try them all. We do the best we can with the gear that is available to us.

And I notice that Aball himself has done three amp reviews here, for Audiogon, and it appears that he used those amps with only one set of speakers. Whadayaknow!

I would agree somewhat. Using one set of speakers that you are familiar with will enable you to discern differences in amplifiers more readily. Especially if the speakers have a quality of being revealing - such as the Thiels - and are considered to be at the upper end of the spectrum.

A reviewer is trying to give a reading on only the amplifier; to attempt a comparison to other amplifiers (FWIW). Whether an amp is of lower or higher quality, it's characteristics will be evident thru a good pair of speakers - then you can assess the reviewer's comments and the amp's measurements as to how it may pertain to your system. After all, if you buy the amp, the final determination as to whether to keep it will be on the basis of how it sounds in your system and not the reviewer's comments (hopefully).

I would also say that if an amp "sounds terrible" with other speakers: is it the fault of the amp or the speakers?

That's part of the appeal of this forum. We can share our experiences with those who have similar gear. Furthermore we can get a consensus.