Hi! Time to pick this up again. I will be looking at replacing the hookup cables and experimenting with speaker cables. On Daves recommendation i got some nice thin neotech hookup wire (26 or 28awg).
After my experiment with the hairline ethernet cable, I was under the impression that thinner cable would favour the bottom end, but recently reading a cable gauge comparison post on positive feedback blog and listening to some japanese diy vids about fostexes, it definitely looks and sounds like that thicker wire brings more bottom end.
I realise that different mechanics must be at play. The thin long ethernet strand actually acted as added series resistor (measurable).
But now im thinking, wouldnt it be best to just use a thicker (say 12 or 10awg) speaker cable all the way to the driver?
Why does this happen even?
After my experiment with the hairline ethernet cable, I was under the impression that thinner cable would favour the bottom end, but recently reading a cable gauge comparison post on positive feedback blog and listening to some japanese diy vids about fostexes, it definitely looks and sounds like that thicker wire brings more bottom end.
I realise that different mechanics must be at play. The thin long ethernet strand actually acted as added series resistor (measurable).
But now im thinking, wouldnt it be best to just use a thicker (say 12 or 10awg) speaker cable all the way to the driver?
Why does this happen even?
Basic wire sizing is all about voltage drop over distance, so the bigger the cable the lower the % and the greater the current rating required for 'amp suckers', hence one reason why my recommendation for Class A/B amps, but 'we' often like to use the wire as an inline resistor to 'dial in' the desired output impedance/frequency response, hence the tiny wire.
I've also noted that 'we' need a high power to handle dynamic headroom (at least +6 dB/4x), so a little 'flea power' amp to satisfy the impedance matching current draw ideally needs a very 'stiff' voltage supply to handle the 'fast' transients that makes the recording come alive as much as it's designed to do.
Well you told me to build 2 ACAs Dave, but I've only built one
Been paired with fostexes for the last year and I'm enjoying it. With room positioning, I have found a good balance (room response included below). Its for sure not the most refined sound, but its big, textured and engaging (coming from popular low efficiency speakers and "well measuring dacs/amps). I'm now looking to finally try those mods we've talked about a year ago, starting with cabinet damping, wiring and 0.98c mod.
I would think one cannot get the fostexes sounding overly syrupy, so am inclined to try an anaconda cable even as a hook up wire. Will look for that video, but bigger cables 8-10AWG deffinately sounded fuller, I just don't understand whats at play here?
Been paired with fostexes for the last year and I'm enjoying it. With room positioning, I have found a good balance (room response included below). Its for sure not the most refined sound, but its big, textured and engaging (coming from popular low efficiency speakers and "well measuring dacs/amps). I'm now looking to finally try those mods we've talked about a year ago, starting with cabinet damping, wiring and 0.98c mod.I would think one cannot get the fostexes sounding overly syrupy, so am inclined to try an anaconda cable even as a hook up wire. Will look for that video, but bigger cables 8-10AWG deffinately sounded fuller, I just don't understand whats at play here?
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Hey GM, nice to see you back in here too! See the pic of the setup bellow. Chord Mojo 2 (dac/amp) directly into single ACA, Mojo has a miniscule output impedance and a max output rating of around 700mW into 8ohms. I use it as a volume control at the same time. According to the volume colors chart below, at ca 0.5-0.6V output into ACA it is already unbearably loud. Most of the time im using half that, Since ACA seems stable enough all the way up to 1.6V input, I would think there is plenty of headroom, is it not? Mojos designer mentioned that Mojo has quite good current suppy capability. It can drive the Fostex horns on its own to reasonable levels.
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Yeah sorry for the product brochure plot
Heres a closer look! What do you make of it?Attachments
Yes indeed…I built a pair of F2J monoblocks years ago.
I stumbled on to Mr. Pass’ article on current source amps when I first took an interest in this hobby about 15 years ago.
I figured a single cross-overless fullrange type of speaker was the easiest way to get involved at that time. That led me to the F2 documentation.
I have also built an LM3875 gainclone, ACA monoblocks, SONY VFET and a pair of Babelfish J2. I have some nice commercial amps as well.
I would have to say that the F2J is probably still my favorite amp…especially with regards to driving wide/full range type speakers.
Up until recently I was listening to them every day through some Kirishima back loaded horns with modified Fostex 206E drivers.
The only reason they aren’t playing right now is because I’m relocating to a new house and everything is basically a mess and I haven’t had time to set them back up.
I have used the F2Js with front horns and open baffle speakers as well with quite a few different drivers i.e. Fostex, Lowther, Tang Band, Sonido etc and compared them to my other amps with the same speakers. The F2J always lures me back with it’s beautiful sound quality.
I attached some pics of the F2J in action with various speakers.
Best of luck in your endeavors.
I stumbled on to Mr. Pass’ article on current source amps when I first took an interest in this hobby about 15 years ago.
I figured a single cross-overless fullrange type of speaker was the easiest way to get involved at that time. That led me to the F2 documentation.
I have also built an LM3875 gainclone, ACA monoblocks, SONY VFET and a pair of Babelfish J2. I have some nice commercial amps as well.
I would have to say that the F2J is probably still my favorite amp…especially with regards to driving wide/full range type speakers.
Up until recently I was listening to them every day through some Kirishima back loaded horns with modified Fostex 206E drivers.
The only reason they aren’t playing right now is because I’m relocating to a new house and everything is basically a mess and I haven’t had time to set them back up.
I have used the F2Js with front horns and open baffle speakers as well with quite a few different drivers i.e. Fostex, Lowther, Tang Band, Sonido etc and compared them to my other amps with the same speakers. The F2J always lures me back with it’s beautiful sound quality.
I attached some pics of the F2J in action with various speakers.
Best of luck in your endeavors.
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The woofers that were in the open baffle and slot loaded open baffles supporting the wide/full range drivers were driven by different amps.
I was using a First Watt B5 active crossover to manage the signal.
I started with some Rotel HT amps, but then eventually moved on to Hypex amps for the low frequency.
I found that depending on the driver used up top and the situation (horn, open baffle etc.) that relieving it of the low frequency burden below 150-300Hz greatly improved the overall performance and sound quality I experienced.
P.S. The Kirishimas are remarkable and the only wideband/fullrange speakers that I can say I am not compelled to add bass support or a sub woofer to for about 90% of what I listen to…with nothing but the F2J driving them.
I was using a First Watt B5 active crossover to manage the signal.
I started with some Rotel HT amps, but then eventually moved on to Hypex amps for the low frequency.
I found that depending on the driver used up top and the situation (horn, open baffle etc.) that relieving it of the low frequency burden below 150-300Hz greatly improved the overall performance and sound quality I experienced.
P.S. The Kirishimas are remarkable and the only wideband/fullrange speakers that I can say I am not compelled to add bass support or a sub woofer to for about 90% of what I listen to…with nothing but the F2J driving them.
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Hi!
I have removed the mineral wool from the coupling chambers. They were packed with it. Measurements confirm that it released quite a bit more low/mid bass energy, but the low-mids and mids are now audiable through the horn. Some nasty cancellations happen as well as smeared imaging. Still sounds surprisingly decent, the low end is almost a bit much with boundry reinforcement.
Next stage will be to put some damping back in the coupling chamber to even out the mids, but keep the horn "breathing", Does a 5mm heavy acoustic felt (the kind found under the floor mats in cars) on the wall behind the driver sound reasonable? I also have a thicker one, 20mm felt with a 5 mm bituminized base layer. Would that be overkill?
Will put some on the magnet as well and maybe do driver spokes in the same go, but will be hard to track changes.
Appreciate comments as always!
Here are some nice images of driver/enclosure in question:
https://diyaudioprojects.com/Speakers/Fostex-FE206En-Back-Loaded-Horn-Speakers/
I have removed the mineral wool from the coupling chambers. They were packed with it. Measurements confirm that it released quite a bit more low/mid bass energy, but the low-mids and mids are now audiable through the horn. Some nasty cancellations happen as well as smeared imaging. Still sounds surprisingly decent, the low end is almost a bit much with boundry reinforcement.
Next stage will be to put some damping back in the coupling chamber to even out the mids, but keep the horn "breathing", Does a 5mm heavy acoustic felt (the kind found under the floor mats in cars) on the wall behind the driver sound reasonable? I also have a thicker one, 20mm felt with a 5 mm bituminized base layer. Would that be overkill?
Will put some on the magnet as well and maybe do driver spokes in the same go, but will be hard to track changes.
Appreciate comments as always!
Here are some nice images of driver/enclosure in question:
https://diyaudioprojects.com/Speakers/Fostex-FE206En-Back-Loaded-Horn-Speakers/
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