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almikel

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About almikel

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  1. At the wavelengths/frequencies being discussed, I don't think "reflections" off internal speaker boundaries come into it - if you equate the speaker enclosure to a "very small room", you're way below the modal zone, and into the pressure zone. There are no "reflections" inside the speaker enclosure, just pressure changes. ^this - is all that matters But to achieve this requires a crossover that matches the sub and mains acoustically. Not too hard to achieve with measurements and DSP - much harder to achieve it passively... ...if your main woofers are sealed that will provide a high pass 12dB/octave response - adding a 2nd order passive high pass at the appropriate frequency would make it 24dB/octave - a reasonable/achievable crossover between mains/sub . You would need a 24dB/octave low pass on the subs at the appropriate frequency to match it - keep in mind you want the acoustic responses to match at crossover (irrespective of passive/active electrical circuits)... ...The acoustic summing of the speakers is all that matters. Add to that - all filters create delay - delay increases the steeper the filter and the lower in frequency the filter - this applies regardless of the type of filter (passive, analog active, DSP). At sub/mains crossover freq these delays should be considered in the solution design - but symmetrical hi pass/low pass crossovers will usually have the same delay. ...Achieving the best "in room" sound - especially in the low end - requires the ability to "muck" with crossovers and speaker/room EQ and delay based on measurements - IMO not achievable with a passive design. As the frequency drops active/DSP becomes the sensible solution. cheers Mike
  2. Serious question - I don't understand why a class A design would consume more power from the power supply/240V outlet for no input signal/no output vs full input signal/full output - I thought the consumption with class A was constant regardless of input? Mike
  3. perhaps a bit OT... Both above are correct - you measure the gain by calculating the ratio of Vout/Vin - but the units are the same top and bottom (volts), so they cancel, and the gain has no units - if Vout was 10V and Vin was 1V, the gain would be 10 (ie output is 10 x the input) - but this is not dB gain... ...it gets a bit more complicated - to express this ratio in dB is Gain (dB) = 20 x log (Vout/Vin) (log base is 10) Gain = 20dB So a voltage gain of 10 (ie Vout = 10 x Vin) when expressed as dB is 20dB Which is different to comparing power instead of voltage Power Gain (dB) = 10 x log (Pout/Pin), or say comparing 2 different amplifiers, one with 200W output vs another with 100W output Power Gain = 10 x log (200/100) (same log base of 10) Power Gain = 3dB the 200W amplifier has 3dB more power than the 100W amp (double the power) I remember which is "10x" vs "20x" by knowing Power = V^2/R, and in log maths Log (V1/V2)^2 becomes 2 x Log (V1/V2) - the ^2 comes down the front changing 10x into 2 x 10=20x...or I Google again... Anything expressed in dB is always a ratio between 2 things (eg power difference between 2 amps, or Voltage out vs Voltage in for an amp), and sometimes the ratio between the thing being measured, and a known reference (eg dB SPL). cheers Mike
  4. You’re always using sine wave sweeps with both rew and Deqx The impulse response is calculated from that
  5. In a DEQX context I still think the first major peak of the impulse of sub and woofer is the guide. If your sub lags your woofer, then treat the difference in the peaks as the maximum time delay for the woofer. Start at 0 sub (edit) mains delay and looking at FR and phase in REW, slowly increase delay on the woofer in DEQX to get a smooth FR and phase in REW. If the sub leads the woofer in the impulse response (likely sub is much closer to the LP than the mains), same process, but add delay slowly to the sub and monitor FR and phase in REW You could probably do it all in REW (but adjusting delay in DEQX) - I'm just more used to using the DEQX for finding the impulse response peaks. REW is better to see how drivers are combining and looking at phase. Mike
  6. mic was moved but as Dave said, @50Hz the wavelength is long - and too late in the evening to pull out the calculator to work out % of wavelength for differing delays in the DEQX... ...the FR and phase was pretty good without adding delay to mains or sub for the crossover at 50Hz - I'll leave it as is.
  7. single sub is about 1m closer to LP than left main speaker I would expect to see some ripples in the FR and phase response, but maybe room modes are too dominant...I can try it tonight...with a bit of luck the mic may even be in the same spot still Mike
  8. just ran some measurements - you're right - sub and mains are separate measurements... Turns out not correct - I'm running zero delay between mains and sub currently...tricky to remember settings made months ago ...did some REW measurements also - crossover between mains and sub is 50Hz and nothing funky is happening FR or phase wise at crossover (50Hz). Below is left mains + sub 70Hz dip moves in freq when adding right mains - likely SBIR. cheers, Mike
  9. it's been a while since I fiddled...just starting a measurement session now...I thought you could run a room measurement with everything...I may be wrong... ...I've lost my TSA doco for the jumper settings - you don't have it handy by any chance? cheers Mike
  10. Good call on REW if looking at phase - I've never gleaned anything useful from the DEQX phase graphs...I've gotten motivated to do some measurements /reconfig... Mike
  11. yes The first major peak is the way it's aligned now - I haven't mucked with anything for ages, and I didn't change the settings after the discussion that lining up the first major impulse is not the best approach... agreed or DEQX using the "room measurement" process... ...I haven't done any measurements or tweaks to config for a long time - last time there were no significant "suck outs" between sub and mains - with time alignment based on aligning the first major peak...and the room response was OK...and the system is sounding great. ...I've been planning to move the DEQX output gain jumpers a notch, so it's about time I did a full calibration. cheers Mike
  12. I would have thought so - you've got a HDP Express II right? It should support it... ...I have the older model HDP3, which doesn't have USB audio in - I use a USB to SPDIF converter Mike
  13. time alignment, phase alignment and smooth frequency response at crossover are all the same thing (in this context). Lining up the impulse response peaks between woofer and sub will result in too much delay of the mains (assuming distance to LP is the same etc etc). It's a reasonable place to start, but then 0 delay is also a reasonable place to start. Somewhere between the 2 is where optimal summing between sub and mains will occur. Mike
  14. @Satanica, basically because they're not perfect impulse responses resulting from a linear phase system. https://bobmccarthy.com/phase-alignment-of-subs-why-i-dont-use-the-impulse-response/ and another SNA thread where it was discussed cheers Mike
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