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Isobaric sub based on Pyle PLPW15d
Isobaric sub based on Pyle PLPW15d
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Old 25th November 2019, 11:02 PM   #1
kipman725 is offline kipman725  United Kingdom
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Default Isobaric sub based on Pyle PLPW15d

I mainly made this document for my own records but I think the design is a good way of getting decent output from cheap high Qts car subwoofer drivers. The measured output is >115dB/1W/1m @ 30Hz.
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Old 26th November 2019, 01:44 AM   #2
Brian Steele is offline Brian Steele  Grenada
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Nice.

I'd take a closer look at that Hornresp sim. As it does not take losses into account, it should be predicting more, not less, output at very low frequencies (e.g. at 30 Hz, where the measurement seems to be 6dB higher than the Hornresp sim).
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Old 26th November 2019, 07:09 AM   #3
kipman725 is offline kipman725  United Kingdom
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At 30hz all the different measurement methods pretty much match, it's higher in frequency where the real world measurement methods show increased efficiency. What the simulation doesn't take I to account though is the acoustic path length from the front to the back of the driver and the directivity of the speaker due to the front baffle dimensions. I performed some baffle simulations and also a simulation of the speaker as a stepped tapped horn and am reasonably satisfied that these two effects are what I'm seeing.
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Old 26th November 2019, 11:51 AM   #4
Brian Steele is offline Brian Steele  Grenada
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If I'm reading this graph correctly, the Hornresp sim is 6dB below the actual measurement at 30 Hz. If you adjusted the relative levels to "line up the curves", the position of the Hornresp sim is still questionable because the sim does not include the impact of losses, which will always result in the measured 2PI response always being less than what the sim predicts at low frequencies.
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Old 26th November 2019, 12:46 PM   #5
kipman725 is offline kipman725  United Kingdom
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I read that as the Hornresp sim the same as the outdoor 2m ground plane sim(It has been adjusted to 1m distance) at 30Hz and the room compensated measurement and inbox measurement about 2dB above the simulation. A UMIK-1 with calibration and REW was used to get these measurements, so all apart from the InBox measurement did not require adjustment of levels for anything apart from drive voltage or distance. I don't have a microphone calibrator so cannot for certain tell you the microphone is working correctly but it has previously produced results I would expect. There are some more details of the measurement procedures and how (with help) I became satisfied that I understood the results I got:
Internal microphone to determine maximum SPL - Bass Gear - Data-Bass Forums
If you where looking for the most accurate representation of its performance in a typical domestic sized room I would use the 'room compensated' response which has no directivity effects. The inbox method is limited by the frequencies below which the pressure distribution is no longer uniform, from memory this is ~60Hz.
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Old 26th November 2019, 12:52 PM   #6
Brian Steele is offline Brian Steele  Grenada
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Oops, my mistake - the difference I was referring to is happening at 20 Hz, not 30 Hz. But the reason is the same - the Hornresp sim'd response should be higher than the measured response at 2.83V/1M (2PI), due to the effect of losses that are not accounted for in the Hornresp sim. If the sim is significantly lower in level (6dB in this case), then that suggests that one of the steps in the process needs to be reviewed.
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Old 26th November 2019, 06:11 PM   #7
kipman725 is offline kipman725  United Kingdom
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Ah I see! The outdoor measurements where done in a pretty cluttered yard there's some reflections or boundary reinforcement down that low. Best I can do unfortunately. The other methods are closer but they are also subject to more error.
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Old 4th March 2020, 07:59 PM   #8
kipman725 is offline kipman725  United Kingdom
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First gig done with four of this box driven from a P7000s in stereo mode with two subs per channel in a sort of warehouse style space (very large lossy room about 100 people). Subs performed remarkably well, where just enough for the party. For bands (heavy jazz funk) some peak limiting on the kick drum but not deleterious. For DJs mostly not limiting apart from very bass heavy passages. Lots of compliments on the sound and the extra depth compared to conventional sub setups was very noticeable. I checked the exposed driver temperature after a few hours and they where luke warm to the touch, no noticeable bass fade through the night, no driver failures.

Probably going to build a similar design around a single higher end driver in a few months to compare performance.
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