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Fulcrum Acoustic FA12, FA15 and FA28 (1 of 4)
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<blockquote data-quote="Langston Holland" data-source="post: 49664" data-attributes="member: 171"><p>Re: Fulcrum Acoustic FA12, FA15 and FA28 (4 of 4)</p><p></p><p><strong>The FA12 Crossover</strong>:</p><p></p><p>The crossovers in these loudspeakers are unusual enough to warrant particular attention.</p><p></p><p>These are full range "passive" loudspeakers that share some important advantages with biamped or "active" designs without requiring twice the number of processing and amplifier channels. There are no padding resistors that reduce electrical damping, waste power, reduce reliability and vary response with voice coil heating. The reduction in passive EQ L/C/R components eliminates another source of response variation with voice coil heating. Why not just use active EQ to lower the level and... drum roll please... do the EQ? The active replacement of passive processing also gives the designer a way of easing the load the amplifier will face without sacrificing SPL. And why waste amplifier output with complicated passive networks that sink current back to ground instead using it to move the drivers? There is quite a bit of this same type of thinking in EAW's KF730 passive mid/high crossover with very good results. For the life of me, I don't understand why we don't see this in far more designs since the end user will be employing a loudspeaker processor virtually without exception in the middle market and up.</p><p></p><p>I want to underscore how big a deal it is to remove the padding resistor(s) to the compression driver in a full range system. Let's look at some example specs for EAW's Microwedge 12", which from all reports is a world class product when used with the UX8800 in biamped mode. This is also a coaxial wedge, but contains a traditional "full service" passive crossover when used in full range mode.</p><p></p><p><u>From EAW's Spec Sheet</u>:</p><p></p><p><em>Calculated Axial Output Limit (whole space SPL)</em></p><p><em></em></p><p><em><u>Aver</u> - <u>Peak</u></em></p><p><em>122dB 128dB (LF/HF)</em></p><p><em>123dB 129dB (LF)</em></p><p><em>128dB 134dB (HF)</em></p><p></p><p>Notice that when biamped, the MW12 has <u>6dB</u> more headroom available from it's compression driver (1kHz and higher). That folks is a huge waste that the FA series avoids.</p><p></p><p>The Fulcrum two-way full range loudspeakers must hold the record for the most complex processing delivered through the simplest passive network. Something else you'll notice if you look closely on the circuit board is that every solder point is labeled "hand load" to confuse the competition's attempts at reverse engineering. Fulcrum keeps a special pair of 3D electromagnetic wavelength decoding glasses locked up that reveal the true solder legends that the assemblers are allowed to use only under armed guard.</p><p></p><p><img src="http://soundscapesweb.com/files/PSW/FAreview/FA12_Crossover.JPG" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>I thought it would be interesting to illustrate how this works by measuring the two passbands independently. Conceptually, the final output of these loudspeakers is a two stage process with the L2 presets and a three stage process with the L1 presets. The third stage involves TQ processing and while included in these measurements is not relevant to the discussion.</p><p></p><p>The first stage is the acoustic output of the passive network and driver after the amplifier. The second stage is the electronic processing before the amplifier. The raw driver overlap between passbands is largely dealt with in the first stage and when combined with the active processing delivers the intended response. To do this well, this type of design still requires a rather beefy compression driver and physically close acoustic origins between passbands. That means an expensive coax driver with a horn that transitions well into the woofer's polar response throughout the crossover region.</p><p></p><p><u>Measurement Setup</u>:</p><p></p><p><img src="http://soundscapesweb.com/files/PSW/FAreview/FA12WedgeMic.JPG" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>I used Smaart v5.4 for the following plots due to its coherence blanking feature that hides the useless out of band phase noise. If you study these closely you'll see that they agree flawlessly with the previous full system measurements using the much more detailed CLIO even though they were made during different measurement sessions. I really need to get with the program (groan) and learn Smaart v7, just been too busy and CLIO stole my heart.</p><p></p><p><u>The following measurements show the FA12 acoustic woofer output(1) in stage monitor position with the passive filter alone (cyan) and with the addition of the active filter (green)</u>:</p><p></p><p><img src="http://soundscapesweb.com/files/PSW/FAreview/FA12_Act_Pass_Low.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><u>The following measurements show the FA12 acoustic compression driver output in stage monitor position with the passive filter alone (blue) and with the addition of the active filter (purple)</u>:</p><p></p><p><img src="http://soundscapesweb.com/files/PSW/FAreview/FA12_Act_Pass_High.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><u>Now we see the active plus passive transfer functions of both woofer and compression drivers with complimentary phase curves</u>:</p><p></p><p><img src="http://soundscapesweb.com/files/PSW/FAreview/FA12_Act_Pass_Both.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><u>Footnote</u>:</p><p></p><p>1. The grill was removed for these measurements to make it easier to disconnect and reconnect the high and low passbands as needed. The unused passive crossover leads were connected to a 10Ω power resistor. I also shorted the positive and negative driver terminals of the unused passband. See below.</p><p></p><p><img src="http://soundscapesweb.com/files/PSW/FAreview/FA12Internal.JPG" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>(End Part 4 of 4)</p></blockquote><p></p>
[QUOTE="Langston Holland, post: 49664, member: 171"] Re: Fulcrum Acoustic FA12, FA15 and FA28 (4 of 4) [B]The FA12 Crossover[/B]: The crossovers in these loudspeakers are unusual enough to warrant particular attention. These are full range "passive" loudspeakers that share some important advantages with biamped or "active" designs without requiring twice the number of processing and amplifier channels. There are no padding resistors that reduce electrical damping, waste power, reduce reliability and vary response with voice coil heating. The reduction in passive EQ L/C/R components eliminates another source of response variation with voice coil heating. Why not just use active EQ to lower the level and... drum roll please... do the EQ? The active replacement of passive processing also gives the designer a way of easing the load the amplifier will face without sacrificing SPL. And why waste amplifier output with complicated passive networks that sink current back to ground instead using it to move the drivers? There is quite a bit of this same type of thinking in EAW's KF730 passive mid/high crossover with very good results. For the life of me, I don't understand why we don't see this in far more designs since the end user will be employing a loudspeaker processor virtually without exception in the middle market and up. I want to underscore how big a deal it is to remove the padding resistor(s) to the compression driver in a full range system. Let's look at some example specs for EAW's Microwedge 12", which from all reports is a world class product when used with the UX8800 in biamped mode. This is also a coaxial wedge, but contains a traditional "full service" passive crossover when used in full range mode. [U]From EAW's Spec Sheet[/U]: [I]Calculated Axial Output Limit (whole space SPL) [U]Aver[/U] - [U]Peak[/U] 122dB 128dB (LF/HF) 123dB 129dB (LF) 128dB 134dB (HF)[/I] Notice that when biamped, the MW12 has [U]6dB[/U] more headroom available from it's compression driver (1kHz and higher). That folks is a huge waste that the FA series avoids. The Fulcrum two-way full range loudspeakers must hold the record for the most complex processing delivered through the simplest passive network. Something else you'll notice if you look closely on the circuit board is that every solder point is labeled "hand load" to confuse the competition's attempts at reverse engineering. Fulcrum keeps a special pair of 3D electromagnetic wavelength decoding glasses locked up that reveal the true solder legends that the assemblers are allowed to use only under armed guard. [IMG]http://soundscapesweb.com/files/PSW/FAreview/FA12_Crossover.JPG[/IMG] I thought it would be interesting to illustrate how this works by measuring the two passbands independently. Conceptually, the final output of these loudspeakers is a two stage process with the L2 presets and a three stage process with the L1 presets. The third stage involves TQ processing and while included in these measurements is not relevant to the discussion. The first stage is the acoustic output of the passive network and driver after the amplifier. The second stage is the electronic processing before the amplifier. The raw driver overlap between passbands is largely dealt with in the first stage and when combined with the active processing delivers the intended response. To do this well, this type of design still requires a rather beefy compression driver and physically close acoustic origins between passbands. That means an expensive coax driver with a horn that transitions well into the woofer's polar response throughout the crossover region. [U]Measurement Setup[/U]: [IMG]http://soundscapesweb.com/files/PSW/FAreview/FA12WedgeMic.JPG[/IMG] I used Smaart v5.4 for the following plots due to its coherence blanking feature that hides the useless out of band phase noise. If you study these closely you'll see that they agree flawlessly with the previous full system measurements using the much more detailed CLIO even though they were made during different measurement sessions. I really need to get with the program (groan) and learn Smaart v7, just been too busy and CLIO stole my heart. [U]The following measurements show the FA12 acoustic woofer output(1) in stage monitor position with the passive filter alone (cyan) and with the addition of the active filter (green)[/U]: [IMG]http://soundscapesweb.com/files/PSW/FAreview/FA12_Act_Pass_Low.png[/IMG] [U]The following measurements show the FA12 acoustic compression driver output in stage monitor position with the passive filter alone (blue) and with the addition of the active filter (purple)[/U]: [IMG]http://soundscapesweb.com/files/PSW/FAreview/FA12_Act_Pass_High.png[/IMG] [U]Now we see the active plus passive transfer functions of both woofer and compression drivers with complimentary phase curves[/U]: [IMG]http://soundscapesweb.com/files/PSW/FAreview/FA12_Act_Pass_Both.png[/IMG] [U]Footnote[/U]: 1. The grill was removed for these measurements to make it easier to disconnect and reconnect the high and low passbands as needed. The unused passive crossover leads were connected to a 10Ω power resistor. I also shorted the positive and negative driver terminals of the unused passband. See below. [IMG]http://soundscapesweb.com/files/PSW/FAreview/FA12Internal.JPG[/IMG] (End Part 4 of 4) [/QUOTE]
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