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About davewantsmoore

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    Log! It's big, it's heavy, it's wood.
  • Birthday October 16

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  1. In at the deep end - SB 15 inch for sensitive bass

    How low (and how steep) do you want to crossover? I like the D2608 9130 ....but in a horn is by far the way to go if it fits your application.
  2. The horn journey

    Generate minimum phase, calculates a phase curve based on the frequency response.... that won't show you the true phase of each driver (ie. it's position in time, relative to the other driver - which is what you're interested in). The "saw tooth" graph is caused (or at least partially caused) by the time of flight of the sound from speaker to mic. You can use the "Estimate IR delay" button to subtract the time of flight from the measurement (check to see the rew detects the correct time/distance though) ..... or you can use a "loopback timing reference". Check the rew documetation/tutorials for how to use these.
  3. Subwofer with Dayton SPA250 plate amplifier, doubt

    Build as large a box as you can fit in your space. If this means you can fit a horn, then build a horn. If this means you have room to fit multiple subwoofers, then use this. This will allow for the most LF efficiency.
  4. Speaker Measurements

    "Is, for example, the broad -5dB centred on 5kHz of the Sonus Faber Olympica 3a problem or is this good enough to be viewed as neutral? " It's really hard to answer this. Most speakers aren't even close to perfect ... and so things like this is what makes speakers sound different from each other. Will you like it? Maybe, perhaps .... in preference to some other error? Who knows. It's pretty certain the getting rid of this error will make the speaker sound better. In practise, it might be hard to "fix" this error, without introducing another one. The more a response error appears at all angles, to more you can fix it with EQ. If the error only appears on some axis, then you can't use EQ to fix it, as it will make the other axes worse.
  5. Speaker Measurements

    You have two types of distortion. 1. The amount of SPL vs frequency (ie. the flatness, as you put it) 2. Added components, which weren't in the original signal (eg. harmonic and intermodulation products) .. this is what people typically call "distortion". As long as 2. isn't grossly audible .... then 1. is the most important thing. Like you say, all axis are important .... but I would argue that "good, flat, on- and off-axis frequency response" is a sufficient condition. It is the thing which matters by far. "Flat" doesn't necessarily mean that SPL with frequency should be literally constant. Some type of falling response as the frequency increases will sound best for most situations. "Flat" really means that you should have no "unintended" wiggles in the frequency response.
  6. Damping Factor

    Sure, but so what?
  7. The horn journey

    Hi Dave, Either DSP or physical alignment of the sources. First, though, work out what you're up against. Put the lowpass+EQ (no delay) you want for the DQT into the minidsp, and then measure each source separately (from the same place), and look at two phase plots.
  8. The horn journey

    The horn and DTQ look like they were always meant to be together. Looks nice.
  9. Damping Factor

    The output Z and the speaker Z are in series.
  10. Damping Factor

    No. If I connect amplifiers with different output impedance to a cone ... and then press on the cone. I can't tell the difference (by pressing) between the different output Zs
  11. Damping Factor

    Quotes like this (it's not your fault AtM) are the source of the problem. When you read the above, you think.... When we unpack what it happening.... and what "overshoot" actually is. Then we see, that there's not necessarily a problem. The speaker designer obviously does his job, and sets it up so there is a certain amount of SPL produced over the range. He'll probably do this using an amplifier that has a relatively low output impedance (eg. > 1/10th of the speaker DCR). If you now use an amplifier which has a much higher output impedance - something changes. At areas where the speaker impedance rises (typically at the system/box resonance) ... the relative SPL also rises.... and so the most obvious change is that we have more bass. Here's a picture of a woofer in a box .... with the amplifier output impedance of 0.1ohm, vs 5 ohm. Is this good? Is this bad? Is this "overshoot"? Well that all depends on what you wanted to begin with. You will hear the difference between the blue line and the yellow line. If you switch back and fort between them (you can do this with EQ), the blue will sound thicker, softer, woolier, potentially more muddied .... and the yellow will in comparison sound "dry" and "tight" (er). If the system was designed around the expectation that you would get the yellow line .... then anything else is technically "linear distortion". If you room / speaker placement, or your subwoofer your integrating with .... or just your own preferences .... mean that the blue line gives you the right response - then blue might be an improvement. It all depends. If you set a system up (with a low output impedance amp) so the yellow line is the response you want .... if you swap in another amp with high output impedance you'll get the blue line - and you probably don't want that. However, if you apply some type of external EQ (a passive network/filter/crossover ... or electronic EQ .... or move the speaker to a different location) ..... then the sound can be put back to where it was correct (eg. yellow)... and all the difference is gone. Now that we see there is a) no universal correct answer, and b ) that we can restore the "correct" systems response other ways (Eg. crossover, or other EQ) .... THEN we can look at other ways to "fairly" compare high vs low output impedances. We find there are some potential advantages to high output impedances for non-linear distortion.... but that is a long and involved can-o-worms.
  12. Damping Factor

    Well, this IMHO is the big problem of modern times.... and how we ended up with the "damping factor" malarky in the first place. They stopped talking to each other .... and amplifier designers forgot (or never knew) how speakers actually worked.
  13. In at the deep end - SB 15 inch for sensitive bass

    Remember that 45deg = 25% out of step with each other .... 90deg = half out of step with each other ..... and, of course, 180 degree = completely cancel each other (zero SPL output) As a rough rule, for where drivers are both contributing significant output, 30 would be a absolute upper limit of what's OK. Makes a truckload(!) more difference than the quality of the driver for example (Just had to drop that comment in there, becuase those AT drivers are the bomb-diggity)
  14. In at the deep end - SB 15 inch for sensitive bass

    Depends on the definition of "large" of course. 3khz = 11cm
  15. The volume pot may have an imbalance when it it turned down low. As ZB said, the further information you provided (assuming the tests were done carefully/methodically like you say) indicates that your amplifier is very likely faulty.