USparc Posted July 8, 2001 Share Posted July 8, 2001 I was playing around with a Radio Shack SPL meter to help me giving my speakers a good place. While testing I noticed that the sound pressure in the highs drops from 14kHz. Surpriced by this I ended up measuring just one RF-3 at 1m distance at horn level. With this setup I measured just the frequencies that the horn is suposed to reproduce. Results: Hz dB 3150 78,5 6300 86 10000 83 11000 81 12000 83 13000 80 14000 78 15000 76 15500 75 16000 74 16500 74 17000 76 17500 74 18000 76 18500 77 19000 76 19500 69 20000 71 The 1000 Hz is set to 80 dB as reference point. What is going on here? Any comments on this one??? Moderators, some technical advise here please. ------------------ ------------------------- Receiver: Onkyo 676 DVD: Pioneer DV-525 Screen: Thomson 46" RetroProjection Front: RF-3's Rear: RF-3's Center: RC-3 Quote Link to comment Share on other sites More sharing options...
USparc Posted July 10, 2001 Author Share Posted July 10, 2001 Hey, I was expecting lots of replies on this one??? I am serious here, has anyone don this already?? Is that Radio Shack SPL meter accurate enough??? I asked someone to do the same on his Nautilus 803's!! I will post his results as soon as I get them. ( It could be the SPL meter ) Please some comments ... ------------------ ------------------------- Receiver: Onkyo 676 DVD: Pioneer DV-525 Screen: Thomson 46" RetroProjection Front: RF-3's Rear: RF-3's Center: RC-3 Quote Link to comment Share on other sites More sharing options...
Seb Posted July 10, 2001 Share Posted July 10, 2001 what's happening? you're experiencing "real life"... try it in an acoustically dead room, you'll get smoother response... :-) besides, no speaker is perfect. there are going to be little bumps and dips along the spectrum... Quote Link to comment Share on other sites More sharing options...
USparc Posted July 11, 2001 Author Share Posted July 11, 2001 Hey Seb, I know that, but this is al lot of attenuation in the highs. More than 10dB and measured right at the horn so that the room is more or les out of the question. I measured this also at about 30cm (12") right in front of the horn tweeter. I am certainly not complaining about how they sound. They sound very good. But this is just a technical issue. Thanks for the reply. ------------------ ------------------------- Receiver: Onkyo 676 DVD: Pioneer DV-525 Screen: Thomson 46" RetroProjection Front: RF-3's Rear: RF-3's Center: RC-3 Quote Link to comment Share on other sites More sharing options...
pzannucci Posted July 11, 2001 Share Posted July 11, 2001 I also have a Radio Shack (digital) SPL meter and I don't think it is much good over 12K (1/3 octave pink noise). I could be wrong but my speakers can be very unforgiving at high frequencies but the meter drops off similarly in the highs as yours. Also look at your input. Peter Z. Quote Link to comment Share on other sites More sharing options...
Ray Garrison Posted July 13, 2001 Share Posted July 13, 2001 USparc, The SPL meter is omnidirectional. It is also not super accuracte outside the (roughly) 100 to 10kHz range. Issue 1; as the meter is omnidirectional, and the speakers have a controlled directivity output, you will find that the in room response, as measured by your SPL meter, will drop in a fairly smooth manner as the frequency increases - the radiation pattern of the horn is narrowing. This is generally a good thing... lack of a lot of reflections coming off the side walls improves imaging. Your perception of the frequency balance will be based more on the direct than the reflected levels, so you will preceive the sound as having a more balanced frequency response than your meter will indicate. To see this in action, if you are able to set up your speakers outside, well away from the house (use a long run of cheap Home Depot cable just for experimentation), you'll find that you measure a more balanced frequency response than you do in room. Issue the second; the Radio Shack SPL meter is not super accurate in the topmost octave (10kHz to 20kHz) in particular. A +/- 10dB range is not unusual. Calibrated meters that are accurate within a dB or so over the whole frequency spectrum are muy expensivo. Ray ------------------ Music is art Audio is engineering Quote Link to comment Share on other sites More sharing options...
Guest BobG Posted July 13, 2001 Share Posted July 13, 2001 There is another important variable likely at work here. If you are using the pink noise like tone from your amplifier, it is usually not flat across frequency. It is typically filtered to minimize variation in highs and lows impact on the level matching you need to use it for. You can get equal amiplitude pink noise (REAL pink noise) on some test CD's. Do not assume your pink noise source is accurate. You could test this by connecting a voltmeter to speaker outputs, it would show the level change. Quote Link to comment Share on other sites More sharing options...
WMcD Posted July 13, 2001 Share Posted July 13, 2001 First, I wouldn't worry about the roll off, if it is a true roll off. 15,000 is pretty high for human perception. Certainly don't judge the speakers as being defective because of your test. Please tell us about the signal source. My guess is that it is not 1/3 octave noise or warble frequencies because your data points are not at standard 1/3 octave spacing. I haven't done the math for 1/3 octaves. But consider that at a given center frequency, some of the warble or noise is going to be much higher, and the whole system response could be rolling off, and still within spec. The RS meter, I believe is not calibrated for much over 12,000, to my recall. Do you have the spec sheet? Is the response plus or minus 2 dB up to 12,000 or the like? More sophisticated test equipment has a better microphone. Even those have calibration curves which are balanced out in the testing software. For $50, RS can't do this. Bottom line. The RS meter when fed with 1/3 octave noise is a real boon to home testing. It lets us get some hard numbers. None the less, it is not up to lab spec equipment. Also, you have to be wary of the equipment providing the signal. Gil This message has been edited by William F. Gil McDermott on 07-13-2001 at 09:24 PM Quote Link to comment Share on other sites More sharing options...
Guest BobG Posted July 14, 2001 Share Posted July 14, 2001 An additional comment. On axis response is not the be-all end-all metric of performance. In fact, if you have a speaker with ruler flat on-axis response, you may find it completely unlistenable. One way people get into trouble with equalizers is attempting just such results. Directivity and in-room energy are critical parameters of performance. While the idea that the response should not vary by 10 dB over the tested range is quite true, there is much more to the total picuture. Let us know what the signal source is. Quote Link to comment Share on other sites More sharing options...
USparc Posted July 15, 2001 Author Share Posted July 15, 2001 Ok, I just borowed this test equipment. It was the SPL meter and a test CD with over 90 numbers. I don't remember the titel but it started at nr 47 with the 150 Hz down to 16 Hz at nr 72 in 5 or 10 Hz steps. Each tone was about 20 seconds. From nr 73 (440 Hz) it goes up to 20kHz (nr 92)as the first post of this thread. My DVD player is digital connected (with IXOS digital coax interconnect) to my receiver which is set in direct mode. With this I think the source is OK and also what is send to my RF-3. So it has to be the SPL meter. Even my ears can still hear the 18kHz out of the horn. The 16kHz will drive me nuts. While it was fun playing around with this meter I will give my ears always the final judgement. Hey, the RF-3's are (musicaly) very nice speakers !!!! Thanks for the replies. ------------------ ------------------------- Receiver: Onkyo 676 DVD: Pioneer DV-525 Screen: Thomson 46" RetroProjection Front: RF-3's Rear: RF-3's Center: RC-3 Quote Link to comment Share on other sites More sharing options...
USparc Posted July 24, 2001 Author Share Posted July 24, 2001 Ok, The nautilus 803 test. The guy returned an email with the same results. So don't worry it is the SPL meter ------------------ ------------------------- Receiver: Onkyo 676 DVD: Pioneer DV-525 Screen: Thomson 46" RetroProjection Front: RF-3's Rear: RF-3's Center: RC-3 Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted July 24, 2001 Share Posted July 24, 2001 Hey, 18KHz, that's pretty good high frequency hearing for a man! You must be young, or have the level quite high. By the way Klipsch fans, if you can't hear a high pitch noise coming out of your computer monitor (or TV, or any device with a CRT), you can't hear 15KHz. CRT's emit a 15KHz tone constantly when they're on. Some days I can hear it, many days, I can't - it pretty close to my high frequency threshold (normal for a man after the age of about 25). My wife can always hear it. You can have the TV on with no signal, so the screen is black, and she'll walk into the room and say "Oh, the TV is on." She can hear it easily. How about you guys? Be honest. KG Quote Link to comment Share on other sites More sharing options...
USparc Posted July 27, 2001 Author Share Posted July 27, 2001 Yes, I'm young (23) Ok, I have to focus on the 18kHz to hear it. But indeed I have never forgotten to turn off my TV when it was still in my bedroom. I would not be able to sleep with that tone. ------------------ ------------------------- Receiver: Onkyo 676 DVD: Pioneer DV-525 Screen: Thomson 46" RetroProjection Front: RF-3's Rear: RF-3's Center: RC-3 Quote Link to comment Share on other sites More sharing options...
quadklipsh Posted March 28, 2011 Share Posted March 28, 2011 15800 hz was as high as i could go. no further. used headfones for the test. but i wonder if any of the original thread members are listening . its an old thread.[] Quote Link to comment Share on other sites More sharing options...
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