1850 horn measured plots |
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pfly
Old Croc Joined: 25 October 2007 Location: Helsinki, Fin Status: Offline Points: 2828 |
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Posted: 10 May 2009 at 7:03pm |
I spent this afternoon with my friend and sound system co-owner measuring and tuning our sound.
We took frequency response plots from different stacks of 1850 horns. Horns have V18-1000s in them. They don't have mouth braces (lazy us!) and there is surprising amount of build tolerances between the cabs (one of them is approx 1cm shorter than the rest!) Measurement was done in proximity of a wall, about 4-5 meters away from it. Mic placement wasn't measured, you can see it from the pictures. Equipment used was Klark-Teknik 6051 -measurement microphone, Edirol UA-25 Interface and Easera Systune. Horns were driven by single QSC RMX 2450 in bridge mode, so we drove it ultimately into 1 ohm nominal load, but we didn't drive it too hard. Levels were kept the same so everytime we plugged another cab in, volume was increased due to lower impedance and mutual coupling. Edirol was plugged straight into the amp and all amp's limiters, filters and such were cut off. Mic was uncalibrated so no actual SPL figures. We started with single 1850 horn standing upright We continued with the same cab on its side Then we added another one Then we stacked them Then we put them upright next to each other Third one Stacked And finally fourth bin was added, first all standing in the same line And stacked in the most optimum way I'll put the second measurement (single cab on its side) again so it can be easily compared to the stack of four So by adding cabs this way we got 12db more sound around 50hz, flatter frequency response and nice bonus extension. Now if that stack would only go to 40hz flat, it would be real winner. I think getting from 50hz to 40hz is way more important than getting from 40 to 30hz, there is so much more relevant musical information in 40-50hz area. Edited by pfly - 10 May 2009 at 8:12pm |
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Sinfinity
Old Croc Joined: 06 July 2008 Status: Offline Points: 1632 |
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Thanks for the effort
Any chance of stacking another two on top please |
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Matt at ukamp dot co dot uk
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pfly
Old Croc Joined: 25 October 2007 Location: Helsinki, Fin Status: Offline Points: 2828 |
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So all four on top of each other? We couldn't lift them like that...
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Sinfinity
Old Croc Joined: 06 July 2008 Status: Offline Points: 1632 |
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No sorry, a stack of six 1850's please
2 wide 3 high Edited by Sinfinity - 10 May 2009 at 8:28pm |
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Matt at ukamp dot co dot uk
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Sinfinity
Old Croc Joined: 06 July 2008 Status: Offline Points: 1632 |
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I understand you have probably allready upset your neighbours, and therefore apologise in advance.
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Matt at ukamp dot co dot uk
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pfly
Old Croc Joined: 25 October 2007 Location: Helsinki, Fin Status: Offline Points: 2828 |
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We don't have six and these four are the only four in Finland as far as I know.
We are going to upgrade to Looneys if all goes well so no more 1850 building... The price of Looney is so cheap that I don't feel like building 1850s myself, even with shipping costs. |
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Sinfinity
Old Croc Joined: 06 July 2008 Status: Offline Points: 1632 |
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I wish you luck on you Looney acquisition
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Matt at ukamp dot co dot uk
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LjudLahger
Young Croc Joined: 31 July 2008 Location: Sweden Status: Offline Points: 838 |
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Rog
New Member Rogers Archive Posts Joined: 23 March 2010 Status: Offline Points: 2166 |
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Sorry to say this but those measurements are compleatly irrelevant.
You never take readings with a measurement mic at x distance from the ground. The mic to floor distance doubled with exhibit gain as you have half space condidtions. Above this you are working in free space. So you are in effect working in two different loading condidtions with the frequency set by the mic to the floor distance.
Please try to learn something about proper groundplane measuremnts before you undertake any measurments. You had a great opportunity and some good measurement kit at your disposal, and if you had taken the measurements correctly some very valid plots to share.
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jethrocker
Old Croc Joined: 07 June 2006 Location: Chiapas, Mexico Status: Offline Points: 1942 |
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So would you say that for measuring groundplane response of bassbins mic should be close to the floor so any halfwave gain would be well out of band?
Though the plots may not be accurate in terms of overall response, i think they're useful to demonstrate the changes in response from different stacking configs...something that comes up here again and again. The results seem to follow theory at least in that respect, you can see the slight extension gained by coupling and the general response slope lifting at bottom end. |
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Rog
New Member Rogers Archive Posts Joined: 23 March 2010 Status: Offline Points: 2166 |
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Yes for comparsion the plots are very usefull.
For groundplane measurements the mic should not be close to the ground, it should be on the ground. Halfspace loading will give 6dB of gain, so if you postion the mic 2 meters away, which will lose you 6dB, you will end up with a 1 meter reading.
2.83 volts in for 8ohms or 2.00 volts on for 4 ohms. I don't understand why they needed to bridge an amp into 1 ohm. Most measurements are taken with between 1 watt and 100 watts. Unless you are measuring power compression, there is no need for mega power amps when doing freuqency responses.
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jethrocker
Old Croc Joined: 07 June 2006 Location: Chiapas, Mexico Status: Offline Points: 1942 |
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So if you wanted to measure the actual halfspace response you would keep the mic at 1 metre, or do you mean that the extra 6dB results from the halfspace loading on the mic itself. I see now that mic on the ground makes sense to maintain the same loading conditions at all frequencies, though I'd still assume that the mic being a very short distance of the floor would make very little difference at low frequencies? |
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