How does internal pressure affect speaker performance?

February 1, 2019
 by Paul McGowan

11 comments on “How does internal pressure affect speaker performance?”

  1. Thank you so very much for today's article, and my NEW speakers!
    Because of your information I decided to plug my ports!
    Now my woofers are much more musical, distinct, controlled by signal input
    rather than 'flapping in the breeze'. I wish very much that you could hear the difference.
    Not a fan of ports? Today NEITHER am I.
    Thank you for your wonderful videos, I watch them every day.
    Craig

  2. Hi Paul, regardless DSP control forward (prediction), or correction by sensor feedback, any typology will have its advantages and disadvantages. The enemy of DSP prediction are production tolerance of the woofer and wear and tear during the woofers life time. Anything variation from assumed parameters in the DSP model, which you can not avoid, will cause deviations in your output from what you try to achieve. So you will need to calibrate every single woofer you put into each speaker, in order to accurately adjust the DSP parameters. You will need woofers that do not wear either, which is is utopian. So, you could use both typologies: First, the DSP to make up for the imperfections of the woofer, speaker and the room and second the feedback sensor to detect any abnormality due to wear and tear. The feedback system could also kick in as a fall back situation in case the DSP runs into a unpredicted mode. After all you showed us a couple weeks ago your prototype woofer that has the motion sensor included, so nothing stopping your team to play around with all of this. My worry however is, that so much effort and cost is invested to conserve the source signal. I mean, direct stream DSD, I2S, sinful expensive wiring, high frequency DACs, power supply regeneration hybrid tube amplifyers etc. but at the final stage a DSP is allowed to have a go at the pressures bass fundament signal. Quite a challenge to do it right and achieve an improvement compared to the overwhelming army of ported speakers. But, the PS Audio team will figure out a way to do it, I am sure.
    Are you still planning to offer a range of speakers, Signature, Stellar and Sprout level? I am curious to see how far you manage to sprinkle the technology down the ladder.

    1. I plan on keeping the motion sensors in the design. In the end, I think it will be a combination of DSP for room correction and servo for control of the two woofers. Work will begin sometime next week and we'll see.

      We do plan on taking the technology down to Stellar and even Sprout lines. One step at a time.

  3. Hi Paul ,

    You mention cancelation as a disadvantage of "open baffle" loudspeakers. But are not the IRS open baffle? I know they are in a league of their own, but still. How do they deal with cancelation? I would appreciate some explanetory remarks.

    Kind regards, Paul

    1. The woofers aren't, which is the biggest problem in open baffles. So, the IRS are a combination of sealed where it matters, and open where it's not too big of a problem.

      The midrange/tweeter panels go down to 100Hz and are open baffle design - or what we call a dipole. The wings you see are there as a sound barrier (like a box) to keep the front wave from the back wave.

  4. A properly designed transmission line loudspeaker..is without doubt.. the king of the hill. The very low distortion factor and the sheer beauty of the low frequencies.. that actually sound like live music.. and the spaciousness of that sound,along with negligible distorted sound levels .. is no less than pure magic. Call me a converted TL believer.....8)

  5. I was puzzled by Paul's comment about the air pressure producing an asymmetry between push and pull directions; as far as I can see, this occurs only because the enclosed volume is very slightly larger when the speaker cone is pushing away from the box, and very slightly smaller when the speaker cone is pushing into the box. If the box has a volume of (say) 20 liters, isn't the volume displacement of the speaker cone small in comparison?

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