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kipman725

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kipman725 last won the day on August 5

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  1. would if I was in the US
  2. If this method was implemented the short term power handling would also increase: https://patents.google.com/patent/US4757547A/en
  3. 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.
  4. 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.
  5. 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.
  6. 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).
  7. 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
  8. 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.
  9. If you look at the picture in the post above I have also added the hornresp response with the drive level adjusted so it should match the +3dB curve in lime green. To match the voltage in hornresp should be -3dB from 2.83V to take into account the +3dB gain over the 2.83V and -6dB due to the measurements been done at 2m resulting in 2V. The actual speaker displays lower than expected sensitivity and different high frequency rolloff character. I will get an impedance plot of the box tonight for further comparison.
  10. I also managed to measure the boxes outdoors (2m ground plane). However the results don't match my hornresp simulations, unfortunately I was quite ill when I took the outdoor measurements and so may have made sensitivity errors. Despite that not even the shape of the response matches simulation... I have measured a few of the drivers and they seem to have consistent T/S parameters and have used the semi-inductance model. The attached data is for the dual driver subwoofers that have two drivers on opposed faces driven in parallel. pyle.dat DualBox.mdat
  11. So now I have two failed drivers I have had a chance to take one of them apart. The top plate is 6mm thick and the voice coil is 20mm tall therefore the mathematical xmax is 7mm: https://speakerwizard.co.uk/driver-ts-parameters-xmax/ This particular driver has failed during transport by the pole piece becoming unglued and then non centered trapping the voice coil.
  12. My sub situation is pretty marginal as its only a hobby for me. Normally I'm running 12*15"low cost drivers in undersized sealed boxes of an NU6000 which I equalise flat. This has just about been enough for indoors. However with only 8 drivers at an outdoor event I just didn't have enough sub; however to good news is that on closer examination to have only lost one driver due to thermal failure during the event and the one that failed before hand in transit so should be able to get up and running again soon. Longer term I'm looking into changing my boxes into eight isobaric bass reflex (weak motors) which will increase output about +10dB according to hornresp and should be fairly compatible with other better drivers as an upgrade path.
  13. I seem to have burnt a load of drivers using the same amp this weekend. 4*15" per channel (only 2.5" VC though) @ 8 ohm total load per channel, sealed boxes. Hitting the built in limiter a lot and for sustained periods of time. I just didn't have enough output to match my tops and the required SPL after loosing a sub due to transit damage. Noticed that one of the drivers seemed to be stuck in place at the end of the night... (totally melted) I presume there are more.
  14. I'm pretty sure I could make a device that could plug into the inputs and outputs of most sub amps and measure the voice coil temperature while the drivers in use. Sounds like there would would be some interest in the device. I have a spare voice coil and have ordered some other bits to test the method so should be able to report back next month on my progress. I don't quite understand why amplifiers don't implement voice coil resistance sensing though as it would be very easy to inject a small DC offset and measure using that, DC protect could just be set to a higher level than the small offset.
  15. Here is some MATLAB code in this case the exact frequency was known in relation to the sample rate and so the carrier is locally generated and didn't need to be recorded as the same sample clock is used for the ADCs as the the DAC that generated the carrier (thus only needing two ADC channels). This was used in another impedance measurement device that used a similar method. As you can see its quite a simple process and could be continuous unlike if you used Fourier methods, so doesn't need a lot of memory for long integration times. function [ Z ] = CalcZIQ(V, I, Fs, F) %CalcZIQ calulates impedance from the voltage and current results % by increasing the length of the voltage and current recording length % less energy is integrated into the result not from the test stimulous %James Lawson 2018 %Inputs: %V: voltage waveform at constant sample rate [V] %I: current waveform at constant sample rate [A] %FS: sample rate [Hz] %F: frequency of interest [Hz] %Outputs: %Z: complex impedance [ohm] %Trim off trailing zero values (caused by result storage method sometimes) %do this by finding first non zero value index = length(V); while V(index) == 0 index = index-1; if index == 1 break; end; end; if index ~= 1 V = V(1:index); I = I(1:index); end; %Generate sine waves at the sample rate to demodulate the data TimePoints = (0:index-1)/Fs; %Sample times demod = sqrt(2)*sin(2*pi*F*TimePoints); %Demodulation waveforms demod90 = sqrt(2)*sin(2*pi*F*TimePoints+pi/2); %IQ modulators ReVmult = demod.*V'; ImVmult = demod90.*V'; ReImult = demod.*I'; ImImult = demod90.*I'; %Low pass filter to remove 2*f component PassbandFreq = Fs/length(V)*10; lpFilt = designfilt('lowpassiir','FilterOrder',8, ... 'PassbandFrequency',PassbandFreq,'PassbandRipple',3, ... 'SampleRate',Fs); %fvtool(lpFilt) ReVmult_filt = filter(lpFilt,ReVmult); ImVmult_filt = filter(lpFilt,ImVmult); ReImult_filt = filter(lpFilt,ReImult); ImImult_filt = filter(lpFilt,ImImult); %integrate, there is not need to do division step as all parts equaly %effected ReVacum = sum(ReVmult_filt); ImVacum = sum(ImVmult_filt); ReIacum = sum(ReImult_filt); ImIacum = sum(ImImult_filt); %Calculate final impedance Z = (ReVacum+1i*ImVacum)./(ReIacum+1i*ImIacum); end
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