Guest atilsley Posted September 16, 2008 Posted September 16, 2008 I'm building the Carfrae Little Big Horn and was wondering if I actually need a cross over. The speaker will have in-built D-class plate amps driving the bass speakers. The amps use a normal adjustable frequency control up to approx 250Hz. So why can't I simply piggy back the RCA signal from the pre-amp direct to the plate amp as well as to the main valve amp?
Guest Parmenter Sound Posted September 16, 2008 Posted September 16, 2008 Hi atilsley, you should be able to do exactly what you say if the plate amp has a built in crossover adjustment. If you are using the Lowther driver it will still be getting sent a full range signal from your main power amplifiers, this will make the Lowther try to play back full range where you might want it to only go down to where your plate amplifier is crossed over. You could always add a active crossover before your power amplifiers then you can control where you want the frequency crossover over between drivers. The other option is a passive crossover before the Lowther taking just the lower bass frequency out. Thanks Jason.
Aslan Posted September 16, 2008 Posted September 16, 2008 (edited) Hi Andrew, the plate amp will roll off the top end of the woofer up to 250Hz but does not provide any lower cutoff on the other driver. As stated it will get a full signal, and therefore not be operating optimally. Jason's options are good ones. EDIT...............for a passive crossover before the driver (assuming it is 8 ohm), place a 7.6mH coil in series with the positive and a 100uF capacitor across the positive and negative after the coil. This will roll off the driver at 12dB per octave at 200Hz and give you some room to move on the plate amp. Edited September 16, 2008 by Aslan
Guest atilsley Posted September 16, 2008 Posted September 16, 2008 Thanks guys...appreciated. I guess with the config I'm looking at, I can start with the cross over in the amp to see what the overall sound quality is like, then look at the active/passive units down the track.
Guest Parmenter Sound Posted September 17, 2008 Posted September 17, 2008 Atilsley, yes you can. I have used the RL Acouistique Lamhorn 1.8 http://www.rlacoustique.com/lamhorn.htm & the Lowther Big Fun Horns with Lowthers (AER & REPs drivers) in the past. Matching subwoofer speed to the Lowther is the hardest part. The Best I ever heard the Lowthers was running the 50 Watt Marantz T1 Project mono block amplifiers in to either the Lamhorns 1.8 or the Big Fun horns full range with no subwoofers connected, really special music. All the best with your new speaker project, half the fun is in the experimenting. Cheers Jason. http://cgim.audiogon.com/cgi-bin/vs.pl?vaslt&1213592673&viewitem&o25
Aslan Posted September 17, 2008 Posted September 17, 2008 Ooooops..........................Doh.....................****head. I should have said the capacitor is in series and the coil is in parallel for a high pass xover. Having one of those days I'm afraid.
Nigel Posted September 17, 2008 Posted September 17, 2008 Andrew, fellow 'Tahs supporter....when/where are you demonstrating your R1s next, I'd love to hear them (and check that you have the capacitors/inductors oriented correctly !!). I shouldn't get your hopes up, I will never be able to afford them. My wife has some large knives in the kitchen. I am especially interested in hearing the ribbon. The last ribbon I heard at Rage years ago, was a long one that tried to do mid-range as well. Some of Rob Mackinlay's estatics ate them for lunch, but as a pure tweeter, I imagine a good ribbon may be nice.
Aslan Posted September 17, 2008 Posted September 17, 2008 Hi Nigel, the R1's are available for a listen anytime you want to pop over. Only problem in the short term is that I have other committments on the next two weekends and will be otherwise occupied. I'm usually here during the day and well into the evening on weekdays. Do we share the same surname?
Gee Emm Posted September 17, 2008 Posted September 17, 2008 I'm building the Carfrae Little Big Horn and was wondering if I actually need a cross over.The speaker will have in-built D-class plate amps driving the bass speakers. The amps use a normal adjustable frequency control up to approx 250Hz. G'day atilsley Love the look of those horns. What a great project. Which drivers are you going to use? When does it start?
Nigel Posted September 17, 2008 Posted September 17, 2008 Andrew, is your name Ward? If so, then you are almost certainly my brother spearated at birth ! How is mum ? Is she still ...........you know.??
Aslan Posted September 17, 2008 Posted September 17, 2008 Andrew, is your name Ward? If so, then you are almost certainly my brother spearated at birth ! How is mum ? Is she still ...........you know.?? It certainly is! I already have a brother thanks...............one is plenty! I'll send you excerpts from an email from the bloke who bought the other unit. He's raving about the sucker..............your's confirmed, awaiting ETA.
Guest atilsley Posted September 18, 2008 Posted September 18, 2008 Little Big Horn has started. Materials being sourced, so there's no turning back now. CAD plans now underway with my guy, plus heaps of emails back and forth with Jim Carfrae the designer. Drivers are Lowther DX4...but maybe a less costly option eg PM2. Bass driver is Volt B250.8 10-inch, driven by a pair of Jaycar's new D-class 150-watt plate amps. CNC routing for the entire horn, plus bass module. Veneered MDF panels to exterior, and solid Blackbutt (at this stage) for the front fancy wood work. Expect these to weigh 70Kgs each...ouch. Can't wait. I'll be making a DVD of the build process.
Aslan Posted September 18, 2008 Posted September 18, 2008 Good stuff mate...............yes, we must have a build diary.
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