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kipman725 last won the day on August 5 2019

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  1. Based on innovative M-Force® transducer from Powersoft®, THOR employs transmission line acoustic design, called in to maximize the performance and deliver otherwise unachievable SPL and frequency response. TH then, Stuffing?
  2. Thanks for the tip on directivity I'm quite satisfied now that's what I'm seeing in the outdoor measurements: The gain (~6dB @50Hz) of the 'inbox' and compensated in room measurements over the bass reflex sim in horn resp I have also managed to reproduce by modeling the box as a stepped tapped horn, trying to keep volumes the same and include acoustic path lengths to the front and back of the driver. This sim is not totally faithfully to the actual geometry but is showing the same mid bass boost. Also interesting was the power compression tests I did they mainly show the amp running out of steam rather than the sub >70Hz in the long duration sweeps. So probably better test methodology would be to monitor actual drive voltage during the sweep for the higher level sweeps.
  3. The drivers are wired in series for 16ohms. I reach xmax around 60V according to hornresp, within the output voltage limitations of an inuke6000dsp. By doing this I can run 8 subs off one amp. The above tests are renomalised to 4V (1W into 16ohm) and 1m. Actual drive voltage was 5.46V and distance 2m. microphone was umik-1 which is usb and calibrated, I don't have a calibrator to check but have always got plausible results when using it to develop full range speakers using time gated measurements. Voltages where measured using a true RMS voltmeter and a constant sine at 50hz at the same drive level as the sweep. I will have a look at the baffles directivity characteristics.
  4. Here is the impedance compared with simulation:
  5. So finally managed to find a place I can do outdoor testing! its a yard so not reflection free but a lot better than testing indoors. You can see that the results are matching the in box measurements to around 100Hz. What I don't get is why this sub is so efficient in the upper bass, the numbers seem impossible? >110dB/1W? In the Hornresp sim I used a semi inductance model generated from impedance measurements of the driver and simulated as a bass reflex. The box is a bit different in that the port goes into a cavity with the (isobaric) driver and that there is obviously quite a long acoustic path from one side the of the driver to the other.
  6. Seems to work when the port is linear. InBox is the compensated SPL inside a bass reflex cabinet which has dimensions that should result in valid data <80Hz. HornResp is the simulation of this sub. Room compensated was generated by measuring a known subwoofer in the same physical location as the DUT. This known subwoofer is a sealed box and has previously been measured using close mic spliced with time gated measurements. You can see that the response shape for the in box measurement matches that of the compensated response. This box differs a bit from the Hornresp simulation in that there exists a cavity into which the port and driver fire which may increase SPL outside the low bass. Next stage I guess is to make a microphone that can cope with those savage in box pressures!
  7. Has anyone experience with microphone in box measurements? https://www.audioxpress.com/article/measuring-loudspeaker-low-frequency-response I was thinking with a transducer that remained linear at high pressures such as the MPX2010 series: https://docs-emea.rs-online.com/webdocs/0ef4/0900766b80ef40f2.pdf The maximum SPL of capabilities of ported and sealed boxes could be measured without resorting to ground plane measurements. I'm not sure though what port air velocity saturation would do to the relationship between internal and external pressure?
  8. would if I was in the US
  9. If this method was implemented the short term power handling would also increase: https://patents.google.com/patent/US4757547A/en
  10. Active driver cooling check out "RC1 soundsystem" and "real horns sound system" real horns are using water cooling for the 8 drivers in the bass horn and also realtime excursion measurement while RC1 have an 'active cooling system' which I think is water cooling. Tom Danley also has a patent on using a air blower through the pole vent. The main benefit is long term power handling as the magnet can be kept cool and heat removed from the box.
  11. Only one top per side they are 3 ways with a passive mid high crossover and active bass/mid-high. Coverage pattern is 90x40. For stereo you are assuming that left and right side add coherently? Good idea on the phone! I also have UMIK to check the accuracy.
  12. I do some PA stuff on an amateur basis, my tops are ~100 dB/1W and I run them off 4 amp channels rated as 120W (180W peak) per channel. On some drum and bass I have seen the clip lights flicker on the power amps would I be correct in estimating that would be about 110dB peaks and an average around 100dB at 3m from the speakers? Also what kind of instrumentation should I get to monitor SPL? as sometimes I worry that its too loud as it can be hard to tell as distortion is low.
  13. Another data point. I was stood next to the mixing desk at an Aphex Twin gig (electronic music) and could see the long term average SPL readout which was hovering around 120dB (no idea of weighting) for the majority and got to around 125dB towards the end. I would say it felt about right and they seemed to have a lot of headroom, at the end a few very low notes were hit hard without any evidence of fading or limiting. This was in a very large lossy indoor environment (warehouse effectively).
  14. It should be possible to load the pyle.dat above into Hornresp. The previous simulation was with 250L box volume but I will endeavor to be more accurate... (very little change in response from reduced volume) The box is 0.396x0.440 (drivers mounted on this face) x1.495 m with the drivers opposed at the bottom of the box. The box has an internal frame of 34 mm wood square planed wood at all vertices and with additional reinforcement around the drivers. There are also cross braces above the drivers which are 15mm dowels but these take up negligible volume these also hold the stuffing in place. Each box has 5 kG of polyfill in it filling the volume immediately above the driver. The internal volume is 239L - 11.0 L (Braces) - 12L (estimate for two drivers) =216L Stuffing density = 23g/L I have attached the .zma files I used to generate the complex inductance parameters using the spreadsheet; the added mass was 163.44 g of disc magnets around the edge of the cone. I haven't included the stuffing as I don't know what values to put in as don't think it would radically change the response shape. I don't think the whole problem can be directivityand opposed drivers as the sensitivity is 10dB lower than expected <60 Hz. added_mass1_163_44.zma free_air1.zma
  15. laid on its side on a wooden pallet with one driver facing towards the mic and one facing away. Microphone on the ground offset two meters from the central axis of the driver facing it.
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