Obviously the BBC-standard monitors, as you mention. ProAc monitors are great, too; I hear raves about the new D2s, $3400 or something. You should also check out Bluenote A3.

Quote:
I recently returned to using a 1978 pair of Rogers LS3/5a speakers. They still have a great sound - an openness and warmth that is very enticing. They really can just disappear like few other speakers I have heard. Are there any more modern speakers that capture the "style" of the Rogers? I know that Stirling and Harbeth make direct replacements, I am wondering more about speakers that might extend the bass or offer other refinements, while still capturing the style of the LS3/5a's.

If reading stereophile mag concerning speaker reviews, look to the quasi-anechoic response pattern.

The bass-midbass should be a HAIR higher in output than the treble. Meaning about 1 to 1.5db. There should be gentle shelf that cascades down to about 3.5 to 4.75-5khz, but must include this region. This dip should be about 2 to 2.5db, MAX. Then it slowly lifts back up to being about .75 to 1 db (but no more) lower than the midbass area...out to about 15-18k. then a gentle roll-off. This shape to the output is generally known as the classic 'BBC dip'. This will make a speaker sound quite open and invitingly warm, all at the same time. Now, getting a speaker to do this, at the same time it gives depth and soundstaging and delivers just the right amount of energy into the the room...that's the trick.

If the speaker also shows a good step response and a good waterfall plot (phase agreeance between the drivers) then you've got a real contender for being a great speaker.

From the Harbeth Website:

"There is much myth, folklore and misunderstanding about this subject.

The 'BBC dip' is (was) a shallow shelf-down in the acoustic output of some BBC-designed speaker system of the 1960s-1980s in the 1kHz to 4kHz region. The LS3/5a does not have this effect, neither in the 15 ohm nor 11 ohm, both of which are in fact slightly lifted in that region.

According to Harbeth's founder, who worked at the BBC during the time that this psychoacoustic effect was being explored, the primary benefit this little dip gave was in masking of defects in the early plastic cone drive units available in the 1960's. A spin-off benefit was that it appeared to move the sound stage backwards away from the studio manager who was sitting rather closer to the speakers in the cramped control room than he would ideally wish for. (See also Designer's Notebook Chapter 7). The depth of this depression was set by 'over-equalisation' in the crossover by about 3dB or so, which is an extreme amount for general home listening. We have never applied this selective dip but have taken care to carefully contour the response right across the frequency spectrum for a correctly balanced sound. Although as numbers, 1kHz and 4kHz sound almost adjacent in an audio spectrum of 20Hz to 20kHz, the way we perceive energy changes at 1kHz or 4kHz has a very different psychoacoustic effect: lifting the 1kHz region adds presence (this is used to good effect in the LS3/5a) to the sound, but the 4kHz region adds 'bite' - a cutting incisiveness which if over-done is very unpleasant and irritating.

You can explore this effect for yourselves by routing your audio signal through a graphic equalizer and applying a mild cut in the approx. 1kHz to 4kHz region and a gradual return to flat either side of that."

http://www.harbeth.co.uk/faq/index.php#13