Andrew Tilsley Posted December 22, 2019 Share Posted December 22, 2019 Using Beyma TPL150 Air Motion Transducer in a three-way system. Passive first order crossover at 3,500Hz for the tweeter. Getting mixed readings when I run the sweep (from listening position). The drop off from 17,000 is unusual....given it does not occur on every sweep. What could be causing this...? Thanks and regards. Link to comment Share on other sites More sharing options...
MGO Posted December 23, 2019 Share Posted December 23, 2019 Hi Andrew, Is it the driver or could something wrong with test set up? Does the other driver do the same? Could be a dry joint on the connections perhaps. Mark Link to comment Share on other sites More sharing options...
Andrew Tilsley Posted December 23, 2019 Author Share Posted December 23, 2019 1 minute ago, MGO said: Hi Andrew, Is it the driver or could something wrong with test set up? Does the other driver do the same? Could be a dry joint on the connections perhaps. Mark Thanks Mark. It's not the driver...as a similar recording applies for each one separately. Thinking the mic is needing calibration...or maybe an amp issue that is changing the signal periodically. Link to comment Share on other sites More sharing options...
Andrew Tilsley Posted December 23, 2019 Author Share Posted December 23, 2019 OK, now this is telling. The red is using 512kb length data sweep...while the green is using 256kb. Red drops away after 20kHz, while green is about 17kHz. That would seem to be the issue. Link to comment Share on other sites More sharing options...
rockeater Posted December 23, 2019 Share Posted December 23, 2019 What rate is blue? Link to comment Share on other sites More sharing options...
Andrew Tilsley Posted December 23, 2019 Author Share Posted December 23, 2019 1 minute ago, rockeater said: What rate is blue? The earlier one with green and blue being flat, were sweeps taken in-room at seating position (stereo). They must have had the high res data for sweep. Link to comment Share on other sites More sharing options...
rockeater Posted December 23, 2019 Share Posted December 23, 2019 Then I would go with what MGO is suggesting, that it is a setup issue and the result is dependent in the data rate. Either on whatever generates the signal or whatever reads it. Play with it and see if the results are consistent. Link to comment Share on other sites More sharing options...
Andrew Tilsley Posted December 23, 2019 Author Share Posted December 23, 2019 OK, thanks. Link to comment Share on other sites More sharing options...
MGO Posted December 23, 2019 Share Posted December 23, 2019 Can you start swapping things out? LIke another set of tweeters without those capacitors. Work backwards to the source. It's REW you're using I think. You can chose in Measure fn Left or RIght input and output. Maybe that could shed some light? Link to comment Share on other sites More sharing options...
TMM Posted December 23, 2019 Share Posted December 23, 2019 Looks like some sort of software/driver issue to me. Either the playback or recording of the sweep is being cut short. If changing the sweep length fixes it (or at least gets you reliably to >20kHz) then I'd just do that and ignore it. Link to comment Share on other sites More sharing options...
Andrew Tilsley Posted December 23, 2019 Author Share Posted December 23, 2019 Thanks guys. Yes, using REW Link to comment Share on other sites More sharing options...
davewantsmoore Posted December 23, 2019 Share Posted December 23, 2019 (edited) 10 hours ago, atilsley said: Thinking the mic is needing calibration Not a "calibration" issue.... although could be a microphone on the way out (give it a v. gentle blow) .... or, well, I'd try that first. 3 hours ago, TMM said: Looks like some sort of software/driver issue to me. This. Didn't see the second post from Andrew. Some type of buffer issue in the driver, or setting in the driver, or REW. Edited December 23, 2019 by davewantsmoore Link to comment Share on other sites More sharing options...
Andrew Tilsley Posted December 23, 2019 Author Share Posted December 23, 2019 The only 'buffer' in the driver is a 5.4uF cap....and an expensive gold/silver Mundorf at that. Link to comment Share on other sites More sharing options...
TMM Posted December 24, 2019 Share Posted December 24, 2019 (edited) I probably should have clarified - looks like 'computer drivers' are the issue (something related to REW, your soundcard, microphone if it's a USB one), not the physical speaker driver . That type of sudden roll-off and a noisy trace after is indicative that the sweep being analysed by REW was just suddenly cut short for some reason - the only way the analogue part of your setup (amplifier, audio cables, crossover, speaker driver) could be causing that would be if you have an intermittent cable or connection which is being vibrated apart by high frequencies. If the sweep always starts 100% reliably I think the latter is unlikely, it's got to be a software/computer problem. Edited December 24, 2019 by TMM Link to comment Share on other sites More sharing options...
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