mustang guy Posted September 15, 2014 Author Share Posted September 15, 2014 (edited) Please be advised, I did not follow Bill Fitzmaurice's protocol when making this measurement. Mostly because I just found them. I can't measure from 4 meters away because my little cord only reaches about 1.5 meters... Here are his notes on the subject: -3dB and -10dB points are tricky, as you have to decide what your 0dB average SPL is. I don't use them, as they're too open to 'interpretation'. Reading SPL with pink noise as a source tells you very little, especially with a sub. For instance, with direct radiators you'll be reading a lot of midbass Doppler harmonic distortion, even if you low-pass the pink noise, because the speaker is the source of the Doppler. You can only get a useful result if your mic output is brickwall filtered at the corner frequencies of the passband. In any event a pink noise SPL will always register about 6dB less than what you want. which is a swept sine wave SPL. But you can calibrate a pink noise sweep to quite close to a swept sine result. To calibrate a chart run a 100 Hz sine wave at 2.83v, the resulting 100 Hz figure is your base SPL. Then adjust the pink noise chart so that the 100 Hz reading on it is the same as it was with the sine wave and you're there. Going back to the -3dB and -10dB figures, most manufacturers will quote those relative to the highest reading of the plot, which is just so much baloney. A more honest method would be to call the peak reading +3dB from average and calculate the -3dB and -10dB points accordingly. Most engineering departments would opt for that method, but they tend to get over-ruled by marketing departments. ****** For testing purposes you really need to do it outdoors, away from buildings or walls, the box on the ground. To get a standard half-space reading you do two measurements. The first is ground plane, with the mic 6 inches above the ground. This is good for up to 200 Hz or so. The second is on-axis, with the mic on-axis, to get the above 200 Hz response. You then combine the two, using the frequency where they overlap as the joint. (This duplicates as close as possible a true half-space measurement, which involves digging a hole in the ground, setting the speaker in the hole with the radiaing plane flush at ground level and backfilled, with the mic suspended overhead on-center.) The ground plane measurement can be done at 1 meter, though a longer distance is better. The on-axis should be done from at least 4 meters away. ****** Edited September 15, 2014 by mustang guy Quote Link to comment Share on other sites More sharing options...
jason str Posted September 15, 2014 Share Posted September 15, 2014 Mostly loss of output from air leaks, even a pinhole size leak will cause loss. Lets not forget this is not the full size THT, the 3 ft wide model is dam near flat to 25 Hz. I will test for leaks. Pretty easy, right from the build sheets... Will report back in this post.. #40 Results: No leaks. These speakers are 100% tight. These are 24" wide THT's. Together, they are 48" wide, and dual drivers. Should result in flatter curve than a 36 with a single driver. Am I wrong? Two cabinets net you increased SPL as you clearly see in your chart. The wider you build the cabinet(s) the flatter your response and increased efficiency. 1 Quote Link to comment Share on other sites More sharing options...
mustang guy Posted September 15, 2014 Author Share Posted September 15, 2014 Mostly loss of output from air leaks, even a pinhole size leak will cause loss. Lets not forget this is not the full size THT, the 3 ft wide model is dam near flat to 25 Hz. I will test for leaks. Pretty easy, right from the build sheets... Will report back in this post.. #40 Results: No leaks. These speakers are 100% tight. These are 24" wide THT's. Together, they are 48" wide, and dual drivers. Should result in flatter curve than a 36 with a single driver. Am I wrong? Two cabinets net you increased SPL as you clearly see in your chart. The wider you build the cabinet(s) the flatter your response and increased efficiency. That brings something to mind. Two honker 36" wide THT's would be an option for comparison to the 1802. Do you have a 36" one? 1 Quote Link to comment Share on other sites More sharing options...
Turbox Posted September 15, 2014 Share Posted September 15, 2014 Does anyone have any curves for the F20? Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted September 15, 2014 Share Posted September 15, 2014 FYI, sub 1 was slightly louder than sub2. I'm not sure what caused this, but it was the inside sub, and sub 2 was the outside sub. The measurements were taken in my shop. The closest wall is 60' away. The ceiling height is 24' at the eves. Looking at your previous measurements and these pictures I believe you probably have several things that are adding up to the difference in the loudness of the two subs, (1) Driver manufacture's variation of sensitivity could be part of the difference. (2) If not driven from the same amplifier channel then amplifier output power variation could be a factor also. (3) sub1 being close to the LaScala could explain some of the gain difference as measured frequency increases. miketn Quote Link to comment Share on other sites More sharing options...
jason str Posted September 15, 2014 Share Posted September 15, 2014 Mostly loss of output from air leaks, even a pinhole size leak will cause loss. Lets not forget this is not the full size THT, the 3 ft wide model is dam near flat to 25 Hz. I will test for leaks. Pretty easy, right from the build sheets... Will report back in this post.. #40 Results: No leaks. These speakers are 100% tight. These are 24" wide THT's. Together, they are 48" wide, and dual drivers. Should result in flatter curve than a 36 with a single driver. Am I wrong? Two cabinets net you increased SPL as you clearly see in your chart. The wider you build the cabinet(s) the flatter your response and increased efficiency. That brings something to mind. Two honker 36" wide THT's would be an option for comparison to the 1802. Do you have a 36" one? I don't have any rooms big enough to benefit from using a bigger THT, in fact the plan is to eventually build a 18" wide Lab 15 loaded to accompany my pair of La Scala's. Either way is really overkill for a small to medium sized room but a little over the top is something we all crave i think. By the way are you happy with your pair of BFM THT's ? Never thought to ask. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted September 15, 2014 Author Share Posted September 15, 2014 FYI, sub 1 was slightly louder than sub2. I'm not sure what caused this, but it was the inside sub, and sub 2 was the outside sub. The measurements were taken in my shop. The closest wall is 60' away. The ceiling height is 24' at the eves. Looking at your previous measurements and these pictures I believe you probably have several things that are adding up to the difference in the loudness of the two subs, (1) Driver manufacture's variation of sensitivity could be part of the difference. (2) If not driven from the same amplifier channel then amplifier output power variation could be a factor also. (3) sub1 being close to the LaScala could explain some of the gain difference as measured frequency increases. miketn 1. Same drivers in each, possibly one slightly off spec from the other. 2. It was the other channel from the same amp. Also could be the other channel of the pink noise which was slightly different. I should have used the same amp channel. My bad. 3. That it true. There could have been some resonation going on from the LaScala and from the other THT which flank sub1. Mostly loss of output from air leaks, even a pinhole size leak will cause loss. Lets not forget this is not the full size THT, the 3 ft wide model is dam near flat to 25 Hz. I will test for leaks. Pretty easy, right from the build sheets... Will report back in this post.. #40 Results: No leaks. These speakers are 100% tight. These are 24" wide THT's. Together, they are 48" wide, and dual drivers. Should result in flatter curve than a 36 with a single driver. Am I wrong? Two cabinets net you increased SPL as you clearly see in your chart. The wider you build the cabinet(s) the flatter your response and increased efficiency. That brings something to mind. Two honker 36" wide THT's would be an option for comparison to the 1802. Do you have a 36" one? I don't have any rooms big enough to benefit from using a bigger THT, in fact the plan is to eventually build a 18" wide Lab 15 loaded to accompany my pair of La Scala's. Either way is really overkill for a small to medium sized room but a little over the top is something we all crave i think. By the way are you happy with your pair of BFM THT's ? Never thought to ask. Overjoyed. I am using them on my main system, and have unhooked the KPT-684's. The THT's match with the LaScalas much better. I will be moving the KPT-684's to the back of the shop so as to better fill it with sub-bass. Klipsch says the KPT-684's are flat to 20Hz with eq, which I will do. I don't feel the need to EQ the THT's, although by the looks of it, they could use a slight boost in the 25Hz are, and some taken away in the midbass region. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted September 16, 2014 Share Posted September 16, 2014 (edited) Does anyone have any curves for the F20? More HERE Edited September 16, 2014 by CECAA850 Quote Link to comment Share on other sites More sharing options...
Thaddeus Smith Posted September 16, 2014 Share Posted September 16, 2014 Does anyone have any curves for the F20? More HERE I cross mine over to the KP-201's at 80hz and it seems to work well for both speakers' limitations. I don't have any measurement equipment so not sure how low I go below 20hz with room gain, but I'm sure there's some. I've never found myself wanting more bass with this sub. 1 Quote Link to comment Share on other sites More sharing options...
Schu Posted September 16, 2014 Share Posted September 16, 2014 OK, I should have better things to do with my time than draw, but it's been a long weekend. it took a long weekend to draw that? Quote Link to comment Share on other sites More sharing options...
Turbox Posted September 16, 2014 Share Posted September 16, 2014 Thanks for the curves guys. Quote Link to comment Share on other sites More sharing options...
Chris A Posted September 17, 2014 Share Posted September 17, 2014 Thanks for the curves guys. Do you have measurements of the 1802? All that has been posted are tabular values for performance (which I believe), but it sure would be nice to see in-room upsweep performance curves using something like REW. Quote Link to comment Share on other sites More sharing options...
Turbox Posted September 17, 2014 Share Posted September 17, 2014 no curves sorry. i dont have anything to measure that with yet. Quote Link to comment Share on other sites More sharing options...
ClaudeJ1 Posted September 17, 2014 Share Posted September 17, 2014 I would vote for the the 3 THT's because you can spread them around the room for more even bass coverage. 4 would be best. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted September 17, 2014 Author Share Posted September 17, 2014 I would vote for the the 3 THT's because you can spread them around the room for more even bass coverage. 4 would be best. Good point Claude. They take up roughly the same real estate, but spread out, they wouldn't be quite as intrusive also. Still, they are huge for most rooms, and something like the F20 with it's slim design can be stood against a wall, put under chairs, etc. Quote Link to comment Share on other sites More sharing options...
ClaudeJ1 Posted September 17, 2014 Share Posted September 17, 2014 I would vote for the the 3 THT's because you can spread them around the room for more even bass coverage. 4 would be best. Good point Claude. They take up roughly the same real estate, but spread out, they wouldn't be quite as intrusive also. Still, they are huge for most rooms, and something like the F20 with it's slim design can be stood against a wall, put under chairs, etc. Well, 4 F-20's would work too. Considering all the companies that get $500 to several $1,000's for direct radiator subs, any of these fully horn loaded subs would totally stomp them in pure performance. In terms of performance per dollar, it would kick them all to the proverbial curb. 1 Quote Link to comment Share on other sites More sharing options...
Turbox Posted September 17, 2014 Share Posted September 17, 2014 I have Dayton woofers to build two F20's...maybe when I get back from florida. But tomorrow, my three 402's are being delivered. Quote Link to comment Share on other sites More sharing options...
jason str Posted September 17, 2014 Share Posted September 17, 2014 Don't mix the KPT-1802 with the F-20's. Its going to give you phase problems. Quote Link to comment Share on other sites More sharing options...
Turbox Posted September 18, 2014 Share Posted September 18, 2014 don't tell me that, your not movitating me to build them. Quote Link to comment Share on other sites More sharing options...
ClaudeJ1 Posted September 18, 2014 Share Posted September 18, 2014 Don't mix the KPT-1802 with the F-20's. Its going to give you phase problems. Hmm. I'm not sure about that, since the room modes dominate the radiator of the super long waves. It's all room dependent, but you gotta have a good horn transducer to start. Quote Link to comment Share on other sites More sharing options...
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