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Small(er) efficient speakers?

Discussion in 'audio' started by Coda II, Aug 18, 2021.

  1. Coda II

    Coda II getting there slowly

    Is it one of those laws of physics things that high efficiency speakers have to be big?
    That they need to be horns or have large drivers and/or big cabinets or use room placement for reinforcement? Or are there eg. near field designs that aren’t trying to fill a room with sound that are unlikely to create issues with low power amplifiers?
    It regularly comes up on here that most of the time, in a domestic situation, we are only using a few watts anyway and then there is the parallel strand of eg. AS always saying that although Harbeths are not particularly efficient they are an easy load.
    So, are there successful pairings of bookshelf speakers with sub 10 watt amplifiers?
  2. Eyebroughty

    Eyebroughty JohnC

    My Quad II Classic valve monos (15 watts) drive both my Shahinian Super Elf's and Linn Akurate 212's just as well as my Naim or Linn amps do, just a different sound presentation.
    Last edited: Aug 18, 2021
  3. Darren L

    Darren L pfm Member

    I found the Diapason Adamantees 3 (90/91 db) to be a very successful pairing with a Sugden A21a , Unison Simply 4 and Arion 300b amp, the Arion was 8w, the other two a little more but as you point out we're normally only using the first few watts. I also found a couple of Totem speakers to work well with the Sugden even though they had sensitivity ratings of 84db and 86db, so clearly there's more to it than just speaker sensitivity.
  4. Tony L

    Tony L Administrator

    Load is key. A lot of very small speakers have really awkward reactive low impedances due to obnoxious porting etc and it is this that upsets low power amps, especially valve ones, not the efficiency.

    To be honest the efficiency is largely irrelevant as no one wants a mini-monitor to play loud, so even one rated at 83-84db or so is fine as even a ten Watt amp will take them far louder than needed in their typical usage context. I’m sure is a key reason for the enduring popularity of the 15 Ohm LS3/5A, it has a very easy valve-friendly load that barely drops below 8 Ohms and can be driven superbly with a good 10 Watt valve amp. Certainly my Leak Stereo 20 or TL 12 Plus (10/12 Watt) monos take the LS3/5A or JR149 as loud as I would ever expect a speaker with a little 5” bass-mid to be driven. These are just not high volume speakers, but in the nearfield with amps as good as these they sound truly stunning.
  5. JensenHealey

    JensenHealey pfm Member

    Physics is definitely involved. To get more db/w out of a speaker, you must make best use of all the motion. Losing all of the backwave in a small box loses about 1/2 the energy already. Getting the box to do something useful at lower frequencies is a skill of speaker design, but good low frequencies need a bigger box.

    For best maximum power transfer you put either the front or back energy into an acoustic transformer - known to all as a horn. But to get a low frequency working worn- physics requires you to make it big. And a horn has very severe bandwith limitations - it only works over a part of the band. So high frequency horns can be small and super efficient. But low frequency ones can be efficient, but are huge.

    Another route is to make the speaker driver huge - 15" say. But then you do not have a compact speaker!

    But... as you surmise and Tony says - in a real domestic situation - near field usage requires sod all watts in reality and many small speakers will work perfectly well as a result.
    Coda II likes this.
  6. Tony L

    Tony L Administrator

    Indeed. The key point to my mind is a small speaker is entirely unsuited to a high volume role due to the basic impossibility of trying to move large amounts of air cleanly with a tiny 5-6” bass-mid. As such efficiency just doesn’t matter as chances are even a low power amp has all that is needed as long as the speaker doesn’t present a really obnoxious reactive load. If you want high volume, real bass extension etc, then you need a much, much bigger speaker, and chances are it will be much more efficient! As such I really don’t see efficiency as an issue in small speakers. You are never going to want to play them loud.
    Coda II and RJohan like this.
  7. RJohan

    RJohan pfm Member

    It's in the laws of physics, and nothing we mere mortals can do anything about. There is a relationship between cut of frequency, efficiency and box volume that one can't get around. Low bass frequencies from a small box means very low efficiency, as an example. There is rather small subwoofers that can go very low in frequency, they do it with POWER. Lot's of it.

    Bass loading of the box has nothing to do with it. If we strive for straight response down to, let's say 20 Hz with a given box volume and efficiency, it doesn't help with reflex loading, transmission line or a horn. We just have to choose a driver (or more than one) with the right parameters (fs, Vas, Qts, etc) for the job and chosen loading.

    As Tony noted, there are some modern small speakers with very low impedance in the bass, this makes the amp deliver more power for a given volume, giving a decently high sensitivity (measured usually as dB from 2.83 Volts), while actually still having a low efficiency (dB from 1 watt).
    Coda II likes this.
  8. Steve 57

    Steve 57 pfm Member

    In the 90s I used ns1000m with a 4 watt amp for a while. Whilst not exactly bookshelf speakers I consider them small !!
    I have used many low efficiency loudspeakers on 3-5 watt amps successfully but there's really nothing in reserve, dynamics suffer depending on the amp (and its damping)
    The more efficient a driver is, the more curved or peaky its response is, that's why most 100 db speakers use 3/4/5 drivers to ensure a flat output.

    There are many advantages and also disadvantages to using higher efficiency drivers, but personally I would not go back to most low efficiency loudspeakers for my main system.
    Coda II likes this.
  9. Paul Burke

    Paul Burke pfm Member

    Hoffman’s iron law. Efficiency, bass or volume, pick one to sacrifice. Small speakers can be quite efficient, but be lacking in lower end output, can’t have all 3
  10. Darren L

    Darren L pfm Member

    Why do you say that?
  11. sideshowbob

    sideshowbob 47 Lab Rat

    Because that's not what any small monitor is good at.

    I run LS3/5as in nearfield with a 2 WPC tube amp on occasions. It works fine at the levels I listen at. I also run them with a NAP 140, but I doubt I'm using much more than a watt of power even then. The sensitivity figures suggest they need lots of power, but they have a very benign impedance, and that's the more important thing.
    Coda II likes this.
  12. Old Shatterhand

    Old Shatterhand pfm Member

    Unfortunately Diapason is lying in their specs. Stereo has measured the Adamantes 25th. and the sensitivity is around 82-88dB depending on the reference point so roughly around 86dB in reality.
  13. Darren L

    Darren L pfm Member

    The pair I owned was 15 + years ago so not the 25th Anniversary model, they had no crossover, just a resistor before the tweeter, I can't quite remember whether they stated that the sensitivity was rated at 90 or 91 db at the usual 1m/2.83 but they were noticeably easier to drive than the SF Concertos, (87db) which were not particularly difficult either.
  14. Old Shatterhand

    Old Shatterhand pfm Member

    I have a review of Hifi & Records of the Adamantes 3 and the frequency response is more ore less the same as the 25th.:)
  15. Darren L

    Darren L pfm Member

    I don't think I've ever seen or read a review on them, , I bought them because I liked how they sounded and looked.
  16. daytona600

    daytona600 Registered User

    Salamander and eastone like this.
  17. Martyn Miles

    Martyn Miles pfm Member

    I know someone who has a pair of Quad 10Ls for sale.
    Absolutely superb speakers for £250.
    Original box & Instructions.
    Buy with confidence.
    They can only appreciate in money terms.
    Coda II likes this.
  18. ampedup

    ampedup Lost in audio

    Tony, there are so many variables in play that your statement has to be qualified. Among the small speakers I have and do own, with 5-6" drivers, the spl of clean audio yielded varies a lot. My MAD 1920S go VERY loud and clean in my space and can rattle the windows with their bass. They are 4 ohm, 90dB. The LS3/5a can't get close to that kind of volume, but they can still go louder than I can possibly tolerate at 12 feet listening distance.
  19. Old Shatterhand

    Old Shatterhand pfm Member

    I didn't said anything negative about their sound. :) The intention of my post was to show that many companies are claiming BS in their specs and fool customers into thinking, that they get speakers with a higher efficiency, low bass, from a small cabinet with a small driver. That will never happen.You can't have it all and that is the answer to the starting post of this thread, because no one can't leaver out the laws of physic even if many manufactures claim they could. Again, nothing against you or your speakers!
  20. Darren L

    Darren L pfm Member

    I didn't think you had anything against me or my choice in speakers, lol. But I hear what your saying.
    I'm sure there's lots of hifi companies that exaggerate the truth and there's tons of BS talked about hifi in general.
    The Diapasons were beautiful speakers to look at, sounded excellent , went loud enough for me with little class A amps and had enough bass for me, granted it was a smallish room I used them in and this is all just my 'subjective' opinion, but yeah I really liked them. I would try using them with a couple of decent active subs as I've found recently I quite enjoy a bit of bass reinforcement.
    Old Shatterhand likes this.

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