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PA Top with AMT
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<blockquote data-quote="Moritz Bachmann" data-source="post: 213666" data-attributes="member: 13680"><p>Thank you all for your reply, we had a lot of other stuff to do, and managed it just now to continue with our project.</p><p></p><p>In the meantime, we met Bennet at the ISE in Amsterdam, which was very interesting for us. We talked a little about Josh´s Skram and the Ipals, but also a little about our problem with the AMT Top. The outcome for us was to go with a closed box and to EQ the lower end to where we need it. Amp power shouldn't be the problem, as we got two FP10k for our 4 Mids and the 2 AMT´s (and they will later get their own amps, so we will then have for each driver its own bridged Channel ... so that should be a lot of headroom).</p><p>Yesterday we tested different CB sizes for both, the 10" and 12" until we got problems with our neighbours- now we need to find another place for testing.</p><p>Again we changed sizes from 20-40L, but couldn´t find any big differences... the small ones with a little better IR and GD, the bigger ones with a aslightly better Frequency response. Also the difference between 10" and 12" is again marginal - here and there the 12" has 2-3dB more, but the 10" has again the better IR and GD. </p><p>So all the differences between the enclosure and driver size seems to point to one preference decision: a smalll enclosure/driver (with the better IR/ GD?!) but lower SPL and more EQ needed, or a larger one with natural worse IR/ GD, but less need of EQ and more output? </p><p>As we will have 2 drivers per AMT, and sound quality is more important than SPL and also the coupling to the AMT´s will be easier with the 10", we will built 2x 25 or 30L enclosures for the 10" and test wich alignment works better- MMT or MTM.</p><p></p><p>Now there poped up new questions for the cllosed box designs:</p><p></p><p>1. is it common/recommended to use the natural "HP filter" of the closed box? So to take the 2nd Order HP of the box and add just another 2nd Order LR/BW filter on the DSP to get a 4th order, instead of EQ it straight down to 70/80Hz, just to have the "real" 4th Order HP filter at 100Hz? of course we would use the 4th Order filter on the Skram then and adapt the Phase to fit the HP filter to the phase of the LP filter.</p><p></p><p>2. How much of EQ in the lower section is "allowed"? The DBX Venu 360 is cappable of doing a gain of 20dB, with one +12dB Bell we get the 12" down to 95Hz, the 10" needs 15dB Bell to come down to 90Hz in a 25L enclosure....</p><p></p><p>The measurents show the different driver sizes with and w/o eq, in 25L and the second with 40L... There is no filter used, and still the low end falls down rapidely in the lower end?</p><p>(all measurements are made without knwoing the voltage/ wattage, but the SPL meter showed on white noise ~89dB... we also made few measuremts with +10dB, wich look better, but they are also the reason why we can´t measure in our garden anymore :/)</p><p></p><p></p><p>Peter: the 3rd Image shows the 25L on ground, mic 2m away</p><p>and the last picture the 12" in our room with EQ</p><p></p><p>PS: "with EQ" means for al measurements a single 16dB Bell at 87Hz, Q=3.5... not optimised of course, but the best we found in 5min testing</p></blockquote><p></p>
[QUOTE="Moritz Bachmann, post: 213666, member: 13680"] Thank you all for your reply, we had a lot of other stuff to do, and managed it just now to continue with our project. In the meantime, we met Bennet at the ISE in Amsterdam, which was very interesting for us. We talked a little about Josh´s Skram and the Ipals, but also a little about our problem with the AMT Top. The outcome for us was to go with a closed box and to EQ the lower end to where we need it. Amp power shouldn't be the problem, as we got two FP10k for our 4 Mids and the 2 AMT´s (and they will later get their own amps, so we will then have for each driver its own bridged Channel ... so that should be a lot of headroom). Yesterday we tested different CB sizes for both, the 10" and 12" until we got problems with our neighbours- now we need to find another place for testing. Again we changed sizes from 20-40L, but couldn´t find any big differences... the small ones with a little better IR and GD, the bigger ones with a aslightly better Frequency response. Also the difference between 10" and 12" is again marginal - here and there the 12" has 2-3dB more, but the 10" has again the better IR and GD. So all the differences between the enclosure and driver size seems to point to one preference decision: a smalll enclosure/driver (with the better IR/ GD?!) but lower SPL and more EQ needed, or a larger one with natural worse IR/ GD, but less need of EQ and more output? As we will have 2 drivers per AMT, and sound quality is more important than SPL and also the coupling to the AMT´s will be easier with the 10", we will built 2x 25 or 30L enclosures for the 10" and test wich alignment works better- MMT or MTM. Now there poped up new questions for the cllosed box designs: 1. is it common/recommended to use the natural "HP filter" of the closed box? So to take the 2nd Order HP of the box and add just another 2nd Order LR/BW filter on the DSP to get a 4th order, instead of EQ it straight down to 70/80Hz, just to have the "real" 4th Order HP filter at 100Hz? of course we would use the 4th Order filter on the Skram then and adapt the Phase to fit the HP filter to the phase of the LP filter. 2. How much of EQ in the lower section is "allowed"? The DBX Venu 360 is cappable of doing a gain of 20dB, with one +12dB Bell we get the 12" down to 95Hz, the 10" needs 15dB Bell to come down to 90Hz in a 25L enclosure.... The measurents show the different driver sizes with and w/o eq, in 25L and the second with 40L... There is no filter used, and still the low end falls down rapidely in the lower end? (all measurements are made without knwoing the voltage/ wattage, but the SPL meter showed on white noise ~89dB... we also made few measuremts with +10dB, wich look better, but they are also the reason why we can´t measure in our garden anymore :/) Peter: the 3rd Image shows the 25L on ground, mic 2m away and the last picture the 12" in our room with EQ PS: "with EQ" means for al measurements a single 16dB Bell at 87Hz, Q=3.5... not optimised of course, but the best we found in 5min testing [/QUOTE]
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