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60 Degree DIY Mid Hi - AKA PM60
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<blockquote data-quote="Peter Morris" data-source="post: 141592" data-attributes="member: 652"><p>Re: 60 Degree DIY Mid Hi</p><p></p><p><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px">For this project to work the LF horn needed to get down to about 80Hz - 100Hz. To do that it had to be about 2 feet long and it had to be bent to make the box small enough to be stick mountable. </span></span></span></p><p><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px"></span></span></span></p><p> <span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px">The LF horn exits top and bottom with the HF horn in the middle. This has vertical directivity implications for the mid range and the bends in the horn limits the quality of the audio above about 800Hz. This meant it was important to be able to get the compression driver to go low – 600Hz to 700Hz. </span></span></span><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px"></span></span></span></p><p><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px"></span></span></span></p><p><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px"><em>Note : All the drivers in this design operate in their piston range and there is more or less no cone break-up.</em></span></span></span><u><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px"></span></span></span></u></p><p><u><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px"></span></span></span></u></p><p><u><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px">Compression Driver Selection</span></span></span></u></p><p></p><p><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px">The BMS driver was designed to operate as low as 300Hz. Above 500Hz the mid range has a peak rating of 1000W and an efficiency of about 110 dB (on a 60 x 40 horn); it maintains at least this efficiency all the way to 20kHz. </span></span></span></p><p></p><p><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px">In terms of distortion the standard 4594 initially doesn't look like anything special, however the HE version I used has flux demodulation rings to lower the distortion. It’s also very important to understand how we perceive distortion. Some distortions are more noticeable than others; some are too high to be heard and others can be masked by the fundamental tone/frequency. The masking occurs for the same reasons as we can delete a soft signal adjacent to a loud fundamental in music compression algorithms. </span></span></span></p><p><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px"></span></span></span></p><p><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px">In simple terms second harmonic distortion is not as objectionable as third harmonic and sub harmonic distortions. The BMS designs have low third and sub harmonic distortions. </span></span></span></p><p><span style="color: #000000"><span style="font-family: 'Calibri'"><span style="font-size: 12px">Sub harmonic distortions are generally caused by cone breakup and also have an effect on shape of the wave front. </span></span></span><a href="http://www.beyma.com/uploads/descargas/1352741021.pdf" target="_blank"><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #0000ff">http://www.beyma.com/uploads/descargas/1352741021.pdf</span></span></span></a></p><p></p><p><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #000000">The horn flare can also contribute to distortion and it is on of the reasons that the RCF HF950 and XT1464 were selected. (see the note on the XT1464 specifications)</span></span></span></p><p></p><p> T<span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px">he BMS is a two-way design which has some advantage for music reproduction. Instead of thinking in terms of <em>one frequency x power handling x efficiency</em>, think in terms of music, dynamics and energy over the whole audio spectrum. The LF part of the compression driver can be going flat out and then the VHF can add more energy to that, producing very substantial peaks. See my sketch below where I have used voltage as an analogy to sound pressure.</span></span></span></p><p></p><p> I suspect i<span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px">f you used a large 4” diaphragm compression driver in combination with a separate VHF driver you will get similar results to the BMS. This is what my friend does with his commercial cinema designs and they sound wonderful. </span></span></span></p><p></p><p><span style="color: #000000"><span style="font-size: 12px"><span style="font-family: 'Calibri'">By using the BMS there is substantial weight and space savings compared to using a 4' diaphragm compression driver or even a 6" - 8" mid plus a VHF driver. This is particularly important in this case where I was trying to keep the weight below 35 kgs. </span></span></span></p><p><span style="color: #000000"><span style="font-size: 12px"><span style="font-family: 'Calibri'"></span></span></span></p><p> <span style="color: #000000"><span style="font-size: 12px"><span style="font-family: 'Calibri'">With the DIY everything exits the same horn from above about 600Hz. The HF horn is also located in the centre of the LF horn. The end results is that DIY behaves very much like a perfect point source … and I’m sure you are aware of all the advantages of this, just ask Ivan </span><span style="font-family: 'Wingdings'"><span style="font-family: 'Wingdings'">J</span></span></span></span></p><p><span style="color: #000000"><span style="font-size: 12px"><span style="font-family: 'Calibri'"></span></span></span></p><p> <span style="color: #000000"><span style="font-size: 12px"><span style="font-family: 'Calibri'">In addition to Bennett’s suggestion of the new 1090, here are some other drivers that that may work. I don’t think you will get that studio monitor like sound quality out of them unless you use a separate VHFdriver or a Beryllium diaphragm variant. FWIW the 4594HE was initially developed for high end studio monitor applications. Except for the Beryllium alternatives they will all be cheaper than the 4594 </span><span style="font-family: 'Wingdings'"><span style="font-family: 'Wingdings'">J</span></span><span style="font-family: 'Calibri'">.</span></span></span></p><p></p><p><a href="http://www.eighteensound.it/PRODUCTS/Products/CatID/3/ProdID=152#.Vca5CmkiPDA" target="_blank"><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #0000ff">http://www.eighteensound.it/PRODUCTS/Products/CatID/3/ProdID=152#.Vca5CmkiPDA</span></span></span></a></p><p><a href="http://www.rcf.it/en_US/products/precision-transducers/neodymium-compression-drivers/nd950-1.4" target="_blank"><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #0000ff">http://www.rcf.it/en_US/products/precision-transducers/neodymium-compression-drivers/nd950-1.4</span></span></span></a></p><p><a href="http://www.rcf.it/en_US/products/precision-transducers/neodymium-compression-drivers/nd950-1.4" target="_blank"><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #0000ff">http://www.rcf.it/en_US/products/precision-transducers/neodymium-compression-drivers/nd950-1.4</span></span></span></a><span style="font-family: 'Calibri'"><span style="color: #000000"><span style="font-size: 12px"> - I think this is available in 1.4” and with a Beryllium diaphragm. </span></span></span></p><p><a href="http://www.beyma.com/products/compressiondrivers/1CP85ND8" target="_blank"><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #0000ff">http://www.beyma.com/products/compressiondrivers/1CP85ND8</span></span></span></a></p></blockquote><p></p>
[QUOTE="Peter Morris, post: 141592, member: 652"] Re: 60 Degree DIY Mid Hi [FONT=Calibri][COLOR=#000000][SIZE=3]For this project to work the LF horn needed to get down to about 80Hz - 100Hz. To do that it had to be about 2 feet long and it had to be bent to make the box small enough to be stick mountable. The LF horn exits top and bottom with the HF horn in the middle. This has vertical directivity implications for the mid range and the bends in the horn limits the quality of the audio above about 800Hz. This meant it was important to be able to get the compression driver to go low – 600Hz to 700Hz. [/SIZE][/COLOR][/FONT][FONT=Calibri][COLOR=#000000][SIZE=3] [I]Note : All the drivers in this design operate in their piston range and there is more or less no cone break-up.[/I][/SIZE][/COLOR][/FONT][U][FONT=Calibri][COLOR=#000000][SIZE=3] Compression Driver Selection[/SIZE][/COLOR][/FONT][/U] [FONT=Calibri][COLOR=#000000][SIZE=3]The BMS driver was designed to operate as low as 300Hz. Above 500Hz the mid range has a peak rating of 1000W and an efficiency of about 110 dB (on a 60 x 40 horn); it maintains at least this efficiency all the way to 20kHz. [/SIZE][/COLOR][/FONT] [FONT=Calibri][COLOR=#000000][SIZE=3]In terms of distortion the standard 4594 initially doesn't look like anything special, however the HE version I used has flux demodulation rings to lower the distortion. It’s also very important to understand how we perceive distortion. Some distortions are more noticeable than others; some are too high to be heard and others can be masked by the fundamental tone/frequency. The masking occurs for the same reasons as we can delete a soft signal adjacent to a loud fundamental in music compression algorithms. [/SIZE][/COLOR][/FONT] [FONT=Calibri][COLOR=#000000][SIZE=3]In simple terms second harmonic distortion is not as objectionable as third harmonic and sub harmonic distortions. The BMS designs have low third and sub harmonic distortions. [/SIZE][/COLOR][/FONT] [COLOR=#000000][FONT=Calibri][SIZE=3]Sub harmonic distortions are generally caused by cone breakup and also have an effect on shape of the wave front. [/SIZE][/FONT][/COLOR][URL="http://www.beyma.com/uploads/descargas/1352741021.pdf"][FONT=Calibri][SIZE=3][COLOR=#0000ff]http://www.beyma.com/uploads/descargas/1352741021.pdf[/COLOR][/SIZE][/FONT][/URL] [FONT=Calibri][SIZE=3][COLOR=#000000]The horn flare can also contribute to distortion and it is on of the reasons that the RCF HF950 and XT1464 were selected. (see the note on the XT1464 specifications)[/COLOR][/SIZE][/FONT] T[FONT=Calibri][COLOR=#000000][SIZE=3]he BMS is a two-way design which has some advantage for music reproduction. Instead of thinking in terms of [I]one frequency x power handling x efficiency[/I], think in terms of music, dynamics and energy over the whole audio spectrum. The LF part of the compression driver can be going flat out and then the VHF can add more energy to that, producing very substantial peaks. See my sketch below where I have used voltage as an analogy to sound pressure.[/SIZE][/COLOR][/FONT] I suspect i[FONT=Calibri][COLOR=#000000][SIZE=3]f you used a large 4” diaphragm compression driver in combination with a separate VHF driver you will get similar results to the BMS. This is what my friend does with his commercial cinema designs and they sound wonderful. [/SIZE][/COLOR][/FONT] [COLOR=#000000][SIZE=3][FONT=Calibri]By using the BMS there is substantial weight and space savings compared to using a 4' diaphragm compression driver or even a 6" - 8" mid plus a VHF driver. This is particularly important in this case where I was trying to keep the weight below 35 kgs. With the DIY everything exits the same horn from above about 600Hz. The HF horn is also located in the centre of the LF horn. The end results is that DIY behaves very much like a perfect point source … and I’m sure you are aware of all the advantages of this, just ask Ivan [/FONT][FONT=Wingdings][FONT=Wingdings]J[/FONT][/FONT][/SIZE][/COLOR] [COLOR=#000000][SIZE=3][FONT=Calibri] In addition to Bennett’s suggestion of the new 1090, here are some other drivers that that may work. I don’t think you will get that studio monitor like sound quality out of them unless you use a separate VHFdriver or a Beryllium diaphragm variant. FWIW the 4594HE was initially developed for high end studio monitor applications. Except for the Beryllium alternatives they will all be cheaper than the 4594 [/FONT][FONT=Wingdings][FONT=Wingdings]J[/FONT][/FONT][FONT=Calibri].[/FONT][/SIZE][/COLOR] [URL="http://www.eighteensound.it/PRODUCTS/Products/CatID/3/ProdID=152#.Vca5CmkiPDA"][FONT=Calibri][SIZE=3][COLOR=#0000ff]http://www.eighteensound.it/PRODUCTS/Products/CatID/3/ProdID=152#.Vca5CmkiPDA[/COLOR][/SIZE][/FONT][/URL] [URL="http://www.rcf.it/en_US/products/precision-transducers/neodymium-compression-drivers/nd950-1.4"][FONT=Calibri][SIZE=3][COLOR=#0000ff]http://www.rcf.it/en_US/products/precision-transducers/neodymium-compression-drivers/nd950-1.4[/COLOR][/SIZE][/FONT][/URL] [URL="http://www.rcf.it/en_US/products/precision-transducers/neodymium-compression-drivers/nd950-1.4"][FONT=Calibri][SIZE=3][COLOR=#0000ff]http://www.rcf.it/en_US/products/precision-transducers/neodymium-compression-drivers/nd950-1.4[/COLOR][/SIZE][/FONT][/URL][FONT=Calibri][COLOR=#000000][SIZE=3] - I think this is available in 1.4” and with a Beryllium diaphragm. [/SIZE][/COLOR][/FONT] [URL="http://www.beyma.com/products/compressiondrivers/1CP85ND8"][FONT=Calibri][SIZE=3][COLOR=#0000ff]http://www.beyma.com/products/compressiondrivers/1CP85ND8[/COLOR][/SIZE][/FONT][/URL] [/QUOTE]
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