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In the Forum: Horn-Loaded Speakers
In the Thread: Deep End DIY - Australian take one Macondo.
Post Subject: Speaker cablesPosted by anthony on: 10/2/2017
I've been thinking about how I am going to wire these Bass Cannons as well as the horns on the horn stack. For some time now I have preferred ribbon/foil speaker cables for the relatively low sensitivity speakers I have been using. The reason I believe is that the particularly low inductance of copper foils "helps" flesh out the bass so nicely, but I am wondering if they are particularly suited to my application with Macondo and in particular the Bass Cannons.
By their nature, foils are low R, high C and very low L. Two foils 0.05mm apart are able to reduce inductance to vanishingly low levels, but this closeness boosts capacitance. Each Cannon will need a metre of wire to get to the back of the tube, and then an average of about 75cm to get to the "junction box" (this is where the wires are starred to their individual Cannons in series/parallel or any combination thereof). That is 14m of speaker wire or 28m of copper foil that would normally be considered internal to the speaker. From the amplifier to Junction Box would be no more than a 1m run so this is very simple. With paralleled drivers, another way of thinking about it is that each driver has a 2.75m speaker cable to it once you go 1m from the amp to Junction Box and 1.75m on average from Junction Box to each individual driver. That is a lot of foil! More importantly that is a lot of capacitance for the amplifier to see and I don't know if it will be a problem.
Foil cable capacitance is in the order of 1nF per metre. 14m of foil cable = 14nF of capacitance that the Melquiades Bass Channel will see. Most speaker cables would be around one-third of that capacitance (but 10 times the inductance). On one hand long speaker cable runs are where you would expect to experience differences in sound due to different speaker cable electrical properties, and this is certainly a lot of speaker cable (14 metres or 46 feet) but is there any way to know if it will be too much capacitance without trial and error?
The other channels are fine. The RAALs will have B+ taken to them so no speaker cables are required. The 3 horns are quite close so I can make foils for them, if that is really required considering the sub 1m lengths required for the Upperbass and MF channels.
All input welcomed.Rerurn to Romy the Cat's Site