• 11-20-2004, 06:54 PM
    theaudiohobby
    Speakers and time decay behaviour
    I was reading an old copy of the Stereophile (Oct 04) and a news report by Paul Messenger jumped out at me (hope my english is correct :) ), i.e. That in a paper presented in the UK Institute of Acoustics by Philip Newell, Keith Holland and Peter Mapp they came to the following conclusion, ie. that it is insufficient to define the a speaker's true bass accuracy by the amplitude response and harmonic distortion. That the time decay behaviour is necessary to accurately define bass accuracy. Not only that they concluded that amplitude response issues are easy to correct, but compensating for poor time alignment is much difficult to correct. Interestingly, the paper also pours cold water on the steep bass filters in reflex loaded boxes due to time smearing issues. This is interesting because if this view becomes widely accepted, we will be seeing a very different kind of speaker in years to come. It may also a long way to explain why speakers like the Quad 57 were so successful in spite of their well? substandard amplitude response behaviour.
  • 11-21-2004, 03:55 AM
    Geoffcin
    I agree
    Quote:

    Originally Posted by theaudiohobby
    I was reading an old copy of the Stereophile (Oct 04) and a news report by Paul Messenger jumped out at me (hope my english is correct :) ), i.e. That in a paper presented in the UK Institute of Acoustics by Philip Newell, Keith Holland and Peter Mapp they came to the following conclusion, ie. that it is insufficient to define the a speaker's true bass accuracy by the amplitude response and harmonic distortion. That the time decay behaviour is necessary to accurately define bass accuracy. Not only that they concluded that amplitude response issues are easy to correct, but compensating for poor time alignment is much difficult to correct. Interestingly, the paper also pours cold water on the steep bass filters in reflex loaded boxes due to time smearing issues. This is interesting because if this view becomes widely accepted, we will be seeing a very different kind of speaker in years to come. It may also a long way to explain why speakers like the Quad 57 were so successful in spite of their well? substandard amplitude response behaviour.

    There's a whole bunch of parameters that are not taken into consideration when testing speakers. Time alignment is an old issue that many speaker manufacturers spend a great deal of R&D on, but is still rarely covered in spec sheet reports. Companies like Thiel have gone to great lengths designing sophisticated crossovers to address this. Extended decay is another problem that all speakers have. The simple fact is that a driver has mass, and when accelerated it stores energy. When asked to stop abruptly it continues on via it's own inertia causing a small amount of distortion, but in reality it's smearing the transient response, and that is much more audible. To alleviate this tendency some manufacturers have gone to using very powerful magnets to control the driver, but there is a limit to what you can do with this, and it's the structural integrity of the driver. Hence manufacturers have gone to stronger exotic materials like Kevlar and carbon fiber. Planar drivers on the other hand, having very little mass, store very little energy, and as such do not "ring" with much intensity as traditional cones. There's also the "box" problem, and this is one that speaker companies are always working on. Boxes ring, there's no getting around it. They store energy just like drivers, and release it in an uncontrolled manner. Some companies have gone to great lengths to design enclosures that have as little a sonic signature as possible. There's no one "best" answer to all of these problems, and not likely to be in the future. This is also a major reason there's so much more difference in speakers, as opposed to other components.
  • 11-23-2004, 02:59 PM
    Richard Greene
    More Stereophile nonsense with no objective listening data as proof
    Quote:

    Originally Posted by theaudiohobby
    I was reading an old copy of the Stereophile (Oct 04) and a news report by Paul Messenger jumped out at me (hope my english is correct :) ), i.e. That in a paper presented in the UK Institute of Acoustics by Philip Newell, Keith Holland and Peter Mapp they came to the following conclusion, ie. that it is insufficient to define the a speaker's true bass accuracy by the amplitude response and harmonic distortion. That the time decay behaviour is necessary to accurately define bass accuracy. Not only that they concluded that amplitude response issues are easy to correct, but compensating for poor time alignment is much difficult to correct. Interestingly, the paper also pours cold water on the steep bass filters in reflex loaded boxes due to time smearing issues. This is interesting because if this view becomes widely accepted, we will be seeing a very different kind of speaker in years to come. It may also a long way to explain why speakers like the Quad 57 were so successful in spite of their well? substandard amplitude response behaviour.

    RG
    Bass accuracy at the listening position is mainly defined by the listening room.

    Amplitude response is rarely better than +/-10dB under 100Hz. w/o equalization.

    Time alignment (phase issues) are reflected in the bass frequency response measured
    at the listening position, and once again the room is the main problem.

    There's a lot more to worry about before you get to fine points such as the best damped bass driver (sealed 0.5Qtc enclosure).

    In most rooms dipole bass will sound better than monopole bass even when the monopole bass is from a critically damped sealed enclosure.

    In addition, the attack of most bass notes, such as the pluck of a bass guitar string and slap of a pedal on a bass drum, is from the mid-range or mid-bass driver in the satellite speakers, not from the subwoofer, so the integration of the subwoofer and satellite speakers is important too.
  • 11-24-2004, 01:38 PM
    Horns
    Now aren't some of these issues addressed by horn-loded drivers not installed in a speaker enclosure? I forgot which company makes these, but I see their adds all the time in my magazines (I'm at work, so I don't have access to them).

    According to the ad, by being horn-loaded, they can generate much greater detail w/o requiring higher volumes. And since they are free-standing, or rather hanging, horns that are not enclosed in a cabinet, they are not affected by cabinet noise.

    I'm just paraphrasing here....
  • 11-30-2004, 01:57 AM
    cpq1c1mo
    Quote:

    Originally Posted by nightflier
    Now aren't some of these issues addressed by horn-loded drivers not installed in a speaker enclosure? I forgot which company makes these, but I see their adds all the time in my magazines (I'm at work, so I don't have access to them).

    According to the ad, by being horn-loaded, they can generate much greater detail w/o requiring higher volumes. And since they are free-standing, or rather hanging, horns that are not enclosed in a cabinet, they are not affected by cabinet noise.

    I'm just paraphrasing here....

    I think you may be referring to the new technology that JBL has claimed - if you have a very thick wallet