Hands off 
Bass Limiting an FE108E Sigma
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Paul Barker
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#16
Hands off -
Cressy Snr
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#17
I've been having another play about today with the 200Hz cutoff frequency and have succeeded in getting the sub to stay invisible by careful adjustment of level and phase controls.
I worked very carefully with the same track on repeat. "Killer Joe" by the Pete Downes trio contains a well-recorded set of ascending and descending bass runs that are present throughout the complete length of the track and is very useful for setting up a subwoofer.
Playing the track over a few times whilst lowering the crossover frequency by small increments at a time, until the sub disappeared, took quite a long time but was well worth it for the results obtained. I was able to maintain a pretty even in-room bass response without the sub appearing at any point, once the level was set correctly.
This crossover point is, for me, a better one than 90Hz as it takes away that last bit of excessive cone excursion and enables me to obtain very loud, clean levels, with only the 2W from the 6080 SE amp pushing things along.
The levels I can play the Mets at now are so far removed from the limited loudness capabilities I had previously that it is ridiculous. Obviously, I still can't play at stadium levels; I mean the laws of physics still apply, but in my little 12' x 12' room they easily bring a grin to the face.
Doing the maths, I need to replace the 100uF series cap with a 6.8mH inductor across the main driver to give the same 200Hz crossover. That'll be the next job in the coming weeks.
Steve
I worked very carefully with the same track on repeat. "Killer Joe" by the Pete Downes trio contains a well-recorded set of ascending and descending bass runs that are present throughout the complete length of the track and is very useful for setting up a subwoofer.
Playing the track over a few times whilst lowering the crossover frequency by small increments at a time, until the sub disappeared, took quite a long time but was well worth it for the results obtained. I was able to maintain a pretty even in-room bass response without the sub appearing at any point, once the level was set correctly.
This crossover point is, for me, a better one than 90Hz as it takes away that last bit of excessive cone excursion and enables me to obtain very loud, clean levels, with only the 2W from the 6080 SE amp pushing things along.
The levels I can play the Mets at now are so far removed from the limited loudness capabilities I had previously that it is ridiculous. Obviously, I still can't play at stadium levels; I mean the laws of physics still apply, but in my little 12' x 12' room they easily bring a grin to the face.
Doing the maths, I need to replace the 100uF series cap with a 6.8mH inductor across the main driver to give the same 200Hz crossover. That'll be the next job in the coming weeks.
Steve
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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Paul Barker
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#18
Maybe 9mH depends how you read the driver impedance graph on the data sheet, looking like 12 ohms or so at 200hz to my untrained eye.
Might be an expensive inductor, but would be nice to know how it turns out if you could obtain one.
Might be an expensive inductor, but would be nice to know how it turns out if you could obtain one.
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Cressy Snr
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#19
I can get a 9mH ferrite cored inductor for a fiver plus VAT from Wilmslow Audio.
You can probably multiply that cost by at least 3 for one of the air cored variety, even though that would be the best option by far.
It's probably best to save up for the real deal and use the caps until I can afford the entrance fee.
Steve
You can probably multiply that cost by at least 3 for one of the air cored variety, even though that would be the best option by far.
It's probably best to save up for the real deal and use the caps until I can afford the entrance fee.
Steve
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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Paul Barker
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#20
9mH air cored would be an imense task. I would give the ones you found a try because they are quite likely to sound better than the sort of cap you have procured, which lets face it you wouldn't dream of using as a coupling cap, but that is just what it is doing.
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Cressy Snr
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#21
Cheers Paul
I'll try the ferrites and report my findings. It sounds decent enough with the Russian teflon bypasses at the moment but those NP electrolytic caps still give me the willies.
Steve
I'll try the ferrites and report my findings. It sounds decent enough with the Russian teflon bypasses at the moment but those NP electrolytic caps still give me the willies.
Steve
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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Cressy Snr
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#22
The NP cap and the teflon bypass have been mounted on the base of the speakers and linked together with 2.5mm copper bus bars. Fitting the inductors once they arrive will be an easy job. Speaker cable is now lightly twisted solid core 2.5mm red/black mains cable from the output transformers to the driver lugs.
The 200Hz crossover point works really well with this setup. Incidentally I was reading one of my old speaker books and realised I had forgotten something fundamental from way back. The author warns against crossing over a driver at less than twice its resonant frequency; particularly if it is to be used in a ported enclosure, otherwise a peak can occur at the crossover point where it meets the lower frequency driver instead of a flat (ish) transition assuming the drivers are of the same efficiency.
For the FE108EZ driver with its 70Hz resonance, a 90Hz crossover point was certainly not ideal but luckily, with the active sub, it was possible to pull the crossover down so as to avoid peaky LF. A passive bass driver would probably have been hideous. So in this case, 200Hz is safely clear of the danger zone and allows the sub to fill in up to a higher frequency without problems.
Steve
The 200Hz crossover point works really well with this setup. Incidentally I was reading one of my old speaker books and realised I had forgotten something fundamental from way back. The author warns against crossing over a driver at less than twice its resonant frequency; particularly if it is to be used in a ported enclosure, otherwise a peak can occur at the crossover point where it meets the lower frequency driver instead of a flat (ish) transition assuming the drivers are of the same efficiency.
For the FE108EZ driver with its 70Hz resonance, a 90Hz crossover point was certainly not ideal but luckily, with the active sub, it was possible to pull the crossover down so as to avoid peaky LF. A passive bass driver would probably have been hideous. So in this case, 200Hz is safely clear of the danger zone and allows the sub to fill in up to a higher frequency without problems.
Steve
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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Cressy Snr
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#23
My 9mH ferrite cored indictors were waiting for me when I got home from school today, so after tea I removed the series caps and fitted the inductors across the Fostex drivers.
Much better! The air is back in a big way. It's quite a surprise how much of a veil poor quality caps can draw over the sound of a speaker system. It is quite benign so you don't really notice the distortion until you remove it.
Needless to say, as a filter, the inductors are a significant improvement over the caps .
Steve
Much better! The air is back in a big way. It's quite a surprise how much of a veil poor quality caps can draw over the sound of a speaker system. It is quite benign so you don't really notice the distortion until you remove it.
Needless to say, as a filter, the inductors are a significant improvement over the caps .
Steve
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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Paul Barker
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#24
Hay that's great news, so where chokes from how much?
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Cressy Snr
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#25
Hi Paul
I got the chokes from Wilmslow Audio. They were a fiver each plus VAT.
Look under crossover components - inductors. They have quite a wide range of values. Their air core ones go up to 4mH and the ferrites up to 9mH.
Steve
I got the chokes from Wilmslow Audio. They were a fiver each plus VAT.
Look under crossover components - inductors. They have quite a wide range of values. Their air core ones go up to 4mH and the ferrites up to 9mH.
Steve
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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Paul Barker
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#26
That is great info, especially that they sound good.
I don't find decent caps particularly noticeable but no doubt no cap is better.
The Rullit speakers I am using seem immune to the problem you can let them fall off naturally and don't need to protect them from bass. He seems to have used cannabis leather and wood to make them.
But those fozzies really don't like bass info.
I don't find decent caps particularly noticeable but no doubt no cap is better.
The Rullit speakers I am using seem immune to the problem you can let them fall off naturally and don't need to protect them from bass. He seems to have used cannabis leather and wood to make them.
But those fozzies really don't like bass info.