Speaker sensitivity vs SQ

My reply is intended to illustrate why & how some high performance speakers are purposely designed knowing that they will have to be low in efficiency because of the laws of physics and engineering. Mini-monitors, like the sealed BBC LS3/5a's and the rear vented KEF LS-50's which have fairly good bass, superb mids & highs but low overall efficiency (82db to 84db)  have obviously earned a prominent place in the market. While higher efficiency spkrs are the ideal it it's impossible to achieve both extended bass & high efficiency is small cabinets. Therefore, if you want a mini monitor to achieve bass the efficiency will have to be limited to about 82db to 85db. The smaller the speaker box, the lower the efficiency must be to avoid sounding thin. The laws of physics & engineering just can't be ignored.  But there are tricks to make it possible for small woofers to perform well in both the bass and midrange in small enclosures. The 1st is the use of small magnets which raises a woofer's Total Q factor(Qts) which partly determines the bass output consistent with Thiele-Small parameters. The 2nd trick is to increase the compliance of the woofer surround which lowers the woofer's resonance frequency. A 3rd way is to select high mass cones effectively raising the Qts and lowering the free air resonance frequency. A 4th method is to use crossovers that simultaneously tame the mid frequencies of the woofer so that they don't drown out the woofer's bass output and at the same time use woofer crossover inductors (coils) with a high enough measured DC resistance to raise the woofer's effective Qts. A 5th method in sealed boxes that accentuates bass but lowers efficiency is to judiciosly overstuff the cabinets with absorbent material eg fiberglas or polyester pillow stuffing which makes the woofer behave as if it's in a much larger box. The stuffing amount can be adjusted to change the Qtc (the box's Qt) ideally between .707 and 1.0. A final thought...complex crossovers can be very helpful in compensating for imperfect woofers, tweeters, & mids but they lower overall efficiency and often tamp down dynamics. Obviously there's lots to consider.

Hi @atmasphere ,

There are a lot of examples when amplifier has mixed SE and PP stages.
For example some SET amplifiers have first stage SRPP and PP amplifiers have SE first stage before phase spliter.
Another example - SE preamp and PP amplifiers.
Do all these amplithis have a prominent 5th harmonic in addition to a 2nd and a 3rd ?

Regards,
Alex.

Great conversation. I think some of you would really be interested in JTR speakers. They were mentioned earlier in the thread. JTR does pro audio as well as some high sensitivity home speakers and subwoofers. I am looking forward to hearing them because of the great reviews I have read.

There are a lot of examples when amplifier has mixed SE and PP stages.
For example some SET amplifiers have first stage SRPP and PP amplifiers have SE first stage before phase spliter.
Another example - SE preamp and PP amplifiers.
Do all these amplithis have a prominent 5th harmonic in addition to a 2nd and a 3rd ?

In P-P amps what is concerning is what circuits are in the feedback loop. They will affect which harmonics have more prominence. IOW the topology affects the distortion signature. IMO a single-ended preamp can work alright with a balanced amp, but I'm not sure that is what you are asking as P-P amps cover quite a range of circuits!

Large size costs more in all ways more to build, ship, store more materials used more finish applied. It's just the way it is. Size is one of the most costly parts of horns.