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davewantsmoore last won the day on April 22 2017

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About davewantsmoore

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  1. In general. Yes. ... that being said, you usually need to run relatively high SPL to get a high SNR. Testing should typically be just loud enough that being in the room is uncomfortable. Yes - although due to the extreme measurement errors possible.... it is better to simulate these things. Or at least simulate AND measure (to ensure your measurement isn't too far different from what is expected). You can still test in room .... the modes just may make it more difficult to observe what is happening.
  2. I'm a little sceptical of Troels result. http://www.troelsgravesen.dk/OBL-15/BMT_c.gif This chart is a near field measurement of the woofer in green. Near field means that the true bass response will only be lower than the chart here .... and get lower and lower as the frequency decreases. (ie. there is an extra "high pass" response which is not being shown) The problem with that is that the chart already shows bass response which is decreasing below 50Hz.... it is already decreasing too much, and a truer measurement (not near field) would only show it decreasing more. This is a nice driver.... but it's not really designed for the very high excursions you will need from an open baffle subwoofer... although that does dramatically depend on the SPL (and bass extension) you really want. I chose -6dB@20Hz and 105dB earlier ... which are pretty good defaults, but you might want something else.
  3. The power rating of this chip is for THD=10%. Really it can only output half that power (ie. 50w) before reaching >> 1% distortion. The power is not likely to be sufficient to get low and loud. The driver is IEC rated to 150w .... so I'd be wanting to be able to put 300w through each driver. Also, depending on how the cabinets are wired (series or parallel) the impedance might be a factor. Eg. If they are the 4ohm driver wired in parallel this is 2ohm - which is fine, but needs an amplifier that's happy with that load. Eg. If they are either the 4ohm or the 8ohm wired in series, this is 8ohm or 16ohm ..... and so the amp will deliver even less power than mentioned above - because the 100w rating (at 10% distortion) is for 4ohm load. (so it's really 50w in 4ohm) Meaning 25w to 8 ohm, or 12.5w to 16 ohm. This is what I use FWIW. https://djcity.com.au/product/crown-xls1002-power-amplifier/ It has an auto-speed fan, so no modding needed.
  4. Yes. 50Hz waves are 6.8m long. Moving the subwoofer by 1m is 14% of a WL.... ie. quite insignificant. If you moves the subwoofer by 2m, then you would start to enter the territory where you might notice something small (but still fairly in significant). It is a much better approach to put the woofer where ever the room response works best .... and then if you need to adjust the timing, to do that by delaying a channel.
  5. The wave is so so so long that the extra distance it travels to bounce around inside the box, is a tiny fraction of a wavelength. If you take a wave.... and then a copy of it delayed by a small fraction of a WL .... and combine them, they add almost perfectly (ie. there is no effect). No. Not a coincidence at all. It corresponds to about an 80cm delay .... so very roughly ~40cm deep box. This is why I said previously "assuming that your have an appropriate low pass filter on your subwoofer". If you don't have a lowpass that is strong enough .... then yes, what happens at higher frequencies is relevant - which makes the internal (and maybe even external) shape of the box, important. A typical subwoofer would be cut out by 80Hz. So a -6dB point = 80Hz, with a 24dB/octave slope. This puts the driver at least 36dB down by 220Hz. ... but the slope of your rolloff is only 6dB/octave, which is insufficient. The solution here is to set an appropriate frequency response for the driver. (Recalling that the frequency response of the driver is the only thing that matters). The 6dB octave loss pass of the subwoofer .... also won't match the high pass response of the midwoofer, which will be 12dB.octave if sealed, and 24dB/octave if vented..... ergo, your subwoofer needs a steeper filter. If, on the other hand - if you really want to have this very low slope. Then you'll have to redesign the box like a midwoofer. Reduce the depth to move the error, and/or stuff the box to absorb the error. That's really not a good choice though ..... as even forgetting about this path-length error, I would not want a driver which is under high power and high excursion (eg. while it's playing 20Hz) .... so also be contributing to playing 200Hz. It seems like you are using a method which kinda goes "I've decided I'm going to do X Y and Z .... and I'll try to deal with whatever result I get as best I can". A much much better approach is to define the result you want.... and then figure out you need to do to get it. Success depends on "getting the desired result" ..... not on whether you used (or not) method X Y and Z to achieve it.
  6. But.... there may be things you can do at your end to improve things. Try connecting your modem to the first socket after the copper enters your property from the street. If you have more sockets wired after that first socket .... get them removed. So the copper wire comes in from the street, to one socket (where the modem is connected) ... and only one socket.
  7. Yep. It's what the nation voted for.... Look to your countrymen. The actual copper in the ground, doesn't necessarily take the most direct/easy path. You are likely connected to the big node (850m), with some snaking around which adds the extra distance. Your neighbours are likely connected to their own mini-node because their line was not able to meet the minimum spec of 25/5. There is nothing wrong.
  8. Of course.... I just didn't want a casual passer by to take home: "XLS12 is an underwhelming driver"
  9. In your other thread .... I said "this is all that matters" .... that should be a very big hint. The parameters of this driver conspire to make it rolloff substantially below ~100Hz ..... ie. it does not have a flat frequency response. A typical q=0.5 box, makes it -6dB @ ~45Hz, and -16dB @ ~20Hz ..... This will sound terrible without some form of EQ to transform the drivers response to be flat.
  10. Output power is very low Input sensitivity is very high Distortion is high Does not have "all the controls" (only has a low pass filter)
  11. Because it's between $450 and $850, depending on how much power you want. Granted they top out at ~1kw .... so might not be enough for some subs. Yep, and also it depends dramatically on how low and loud you want the subwoofer to be able to play. The whole "10" is not enough" idea, relies on assumptions of "too low and/or too loud".... which I don't think we know. Truly superb driver. You were doing "something wrong"
  12. The enclosure is too small to affect the sound in the frequency band where the woofers operates. Just like your subwoofer enclosures. The boxes are small compared to the sound waves. The boxes have no effect. It's too small to be doing anything below about ~400Hz.
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