Hi Adejacko
Great to hear things are improving. It would be no fun if there were no rewards!
Careful of what you put in the horn mouth - I found it does affect the quality and quantity of the bass. I just have a small amount of lambs wool in the bottom of the cabinet to soak up any unwanted midrange escapeees.
My cabinets are angled so the sweet spot occurs about 1-2 feet behind my listening chair. I tried them crossing in front but found it narrowed the soundstage too much. So now I put them firing straight down the room, and tilt them in very slightly. Make sure they do not fire directly at your ears!
With the caps on the tweeter, you have to remember that the T90a is 106db efficient, than the Fe208 at 97db. So crossing at say 20,000 with 1uf cap means 103db efficient at 10,000, 100db efficient at 5,000 and 97db efficient at 2500 which is about where you want it. I found any value from 0.47 to 1.5uF seems to suit depending on your partnering equipment, ears (mine are a bit sensitive) and how loud you like it. I am using 0.68 to 1.0uf.
I have both an EL34 push pull, and a 45 SET amp, and have found the SET amp mates the best. Surprisingly it has the best bass too. EL34 seems to have more drive through the mids, but that is a function of its preferred frequency range - it doesnt do as well in the lows or highs. The 45 SET has a more even response, and the low damping factor (high output impedence) seems to mate well with the horns. THe SET has no feedback, but my PP does, so maybe that is part of it too.
Remember that the FE208 has only 1mm of xmax, so its not going to give you thundering bass. I would say the bass takes a while to come into its own, and one day you will be just sitting there and thinking, wow that sounds like bass! The kind of bass mine gives is not sub bass, movie theatre, car stereo style muffled crap bass, it is clear, distinct where you can hear the 3d sound of the bass guitar, a clear and clean note. I liken it to turning off the loudness switch on your car radio or home theater, or winding back the bass dial a quarter turn. You could always add a sub bass box as a seperate piece of kit if you want.
My enclosure was 22mm ply without the strips. It does flex somewhat, and some notes drone rather than pluck. I think this happens with many speakers at the resonant level. Unless you want to spend a fortune putting more wood on the exterior, or some additional bracing, I wouldnt worry. Certainly 36mm would deaden any resonances.
You could use an equilizer or go active. Some blokes do - probably more so with open baffle than horns. I keep thinking the original reason I built these was for the simplicity - a point source, one smalle simple amp, and some easy music. I didnt build them to be a home movie, or to play a 112 piece Mahler symphony or to show off to mates as Í have a bigger woofer than you...I think given time you will go full circle and come back to where you started and the motivation you bought these for originally.
Its funny, I now think I am very close to the sound I want, and with small tweaks like cables ( I use multistrand copper - tried the cat 5 - too bright for me), caps (I like the Obligatto as very clean with the T90a, and have some v-caps coming for my amp!), speaker positioning, and partnering equipment.
Enjoy the journey and have fun!
Adam
Great to hear things are improving. It would be no fun if there were no rewards!
Careful of what you put in the horn mouth - I found it does affect the quality and quantity of the bass. I just have a small amount of lambs wool in the bottom of the cabinet to soak up any unwanted midrange escapeees.
My cabinets are angled so the sweet spot occurs about 1-2 feet behind my listening chair. I tried them crossing in front but found it narrowed the soundstage too much. So now I put them firing straight down the room, and tilt them in very slightly. Make sure they do not fire directly at your ears!
With the caps on the tweeter, you have to remember that the T90a is 106db efficient, than the Fe208 at 97db. So crossing at say 20,000 with 1uf cap means 103db efficient at 10,000, 100db efficient at 5,000 and 97db efficient at 2500 which is about where you want it. I found any value from 0.47 to 1.5uF seems to suit depending on your partnering equipment, ears (mine are a bit sensitive) and how loud you like it. I am using 0.68 to 1.0uf.
I have both an EL34 push pull, and a 45 SET amp, and have found the SET amp mates the best. Surprisingly it has the best bass too. EL34 seems to have more drive through the mids, but that is a function of its preferred frequency range - it doesnt do as well in the lows or highs. The 45 SET has a more even response, and the low damping factor (high output impedence) seems to mate well with the horns. THe SET has no feedback, but my PP does, so maybe that is part of it too.
Remember that the FE208 has only 1mm of xmax, so its not going to give you thundering bass. I would say the bass takes a while to come into its own, and one day you will be just sitting there and thinking, wow that sounds like bass! The kind of bass mine gives is not sub bass, movie theatre, car stereo style muffled crap bass, it is clear, distinct where you can hear the 3d sound of the bass guitar, a clear and clean note. I liken it to turning off the loudness switch on your car radio or home theater, or winding back the bass dial a quarter turn. You could always add a sub bass box as a seperate piece of kit if you want.
My enclosure was 22mm ply without the strips. It does flex somewhat, and some notes drone rather than pluck. I think this happens with many speakers at the resonant level. Unless you want to spend a fortune putting more wood on the exterior, or some additional bracing, I wouldnt worry. Certainly 36mm would deaden any resonances.
You could use an equilizer or go active. Some blokes do - probably more so with open baffle than horns. I keep thinking the original reason I built these was for the simplicity - a point source, one smalle simple amp, and some easy music. I didnt build them to be a home movie, or to play a 112 piece Mahler symphony or to show off to mates as Í have a bigger woofer than you...I think given time you will go full circle and come back to where you started and the motivation you bought these for originally.
Its funny, I now think I am very close to the sound I want, and with small tweaks like cables ( I use multistrand copper - tried the cat 5 - too bright for me), caps (I like the Obligatto as very clean with the T90a, and have some v-caps coming for my amp!), speaker positioning, and partnering equipment.
Enjoy the journey and have fun!
Adam
Hi Adam,
I have Fostex attenuators for the tweeters, so I reduced the SPL by 6dB. Otherwise the 1.5uf cap, and crossover level would be too high.
At the moment, I have bitumen, felt and underlay in the mouth of one speaker, and nothing in the other - to test the effect on the bass. The former is tight, the latter woolly. So I'm gonna put the same in the second speaker. I know it sounds too much, but I'd rather hear all the bass notes than just feel vibration. I have just bitumen and felt in the cc, and am going to add the underlay, as it seems to help with the higher frequencies.
What is the 1mm of xmax? I have never heard of this.
At the moment, I have single strands of Cat5 connecting the tweeters and L-pads to the speaker terminals. I was thinking of adding a few more strands to the mix. If you don't like Cat5, what do you prefer?
The reason I built the SEX amp and horns is a bit messed up. I built the SEX amp for my headphones, then as an afterthought decided it would be nice to have some speakers too. I'd read about the magic of SET amps and horns. My brother has been talking about them for years, but never built either (he has a Class D amp and BIBs). He said that the Fostex 208 Sigmas were the drivers to get. I actually preferred smaller drivers, but they didn't have a high enough SPL. So when a pair of 208's turned up on ebay, I bid and won. Then ordered the flat-pack from Wilmslow Audio.
In retrospect, I would have bought the Stereomour rather than the SEX amp, and built a subwoofer to go with a pair of bookshelf speakers with 4" Fostex drivers my brother has lying around.
Anyway, it's done now, and I have to make the best of these huge monsters in my living room. It's been a learning experience, and it's still not over. The next step is to build a 2A3 or 45 SET amp. If you say the 45 has better bass, than that would be my choice.
What make of amp do you have?
I'm moving to Italy in 3 months, so they will go in storage until I get back summer 2014.
I will experiment with listening positions, damping materials and cables meanwhile.
As far as equalization is concerned, I don't know about active or passive - I am new to all this. I'll look into it. Also, there are these companies who can alter the drivers (painting dots on them) to even out the frequency response. Do you have any experience of this?
Cheers,
Ade
I have Fostex attenuators for the tweeters, so I reduced the SPL by 6dB. Otherwise the 1.5uf cap, and crossover level would be too high.
At the moment, I have bitumen, felt and underlay in the mouth of one speaker, and nothing in the other - to test the effect on the bass. The former is tight, the latter woolly. So I'm gonna put the same in the second speaker. I know it sounds too much, but I'd rather hear all the bass notes than just feel vibration. I have just bitumen and felt in the cc, and am going to add the underlay, as it seems to help with the higher frequencies.
What is the 1mm of xmax? I have never heard of this.
At the moment, I have single strands of Cat5 connecting the tweeters and L-pads to the speaker terminals. I was thinking of adding a few more strands to the mix. If you don't like Cat5, what do you prefer?
The reason I built the SEX amp and horns is a bit messed up. I built the SEX amp for my headphones, then as an afterthought decided it would be nice to have some speakers too. I'd read about the magic of SET amps and horns. My brother has been talking about them for years, but never built either (he has a Class D amp and BIBs). He said that the Fostex 208 Sigmas were the drivers to get. I actually preferred smaller drivers, but they didn't have a high enough SPL. So when a pair of 208's turned up on ebay, I bid and won. Then ordered the flat-pack from Wilmslow Audio.
In retrospect, I would have bought the Stereomour rather than the SEX amp, and built a subwoofer to go with a pair of bookshelf speakers with 4" Fostex drivers my brother has lying around.
Anyway, it's done now, and I have to make the best of these huge monsters in my living room. It's been a learning experience, and it's still not over. The next step is to build a 2A3 or 45 SET amp. If you say the 45 has better bass, than that would be my choice.
What make of amp do you have?
I'm moving to Italy in 3 months, so they will go in storage until I get back summer 2014.
I will experiment with listening positions, damping materials and cables meanwhile.
As far as equalization is concerned, I don't know about active or passive - I am new to all this. I'll look into it. Also, there are these companies who can alter the drivers (painting dots on them) to even out the frequency response. Do you have any experience of this?
Cheers,
Ade
Hi adejacko
I was wondering how the attenuators might sound. I have long thought about them to equlise the T90 with the 208 - can you tell much of a difference if they are removed and just a cap of 1.5 between the two?
1mm of xmax means the speaker cone does not move in and out very much. In order to get real bass, you need to move air (its a physics thing). many sub woofers have an excursion of 10mm or higher. This combined with a larger cone area means they move more air, and give more bass. The whole idea of the horn behind the cone is to take that small cone movement and amplify it down a line. The horn only works for frequencies below about 300hz. So what you dont want going down the line is the midrange that is also contained in the rear wave. The compression chamber somewhat controls that, but you also get some spillover which goes down the line and can blur the sound. So thats where damping comes in to damp out the unwanted mid range going down the horn.
The 45 amp is from a local builder here in Melbourne Weston Accoustics. He has a website, but predominantly builds for a vibrant local market here in Australia. This tube only puts out 1.8w per channel, so it is never going to give thumping bass nor is any other amp as the physics of the 208 driver will just not allow deep thumping bass. For that you will need a subwoofer regardeless. If you want clear well defined bass in unison with the music, then a SET/horn set up is great. However, if you have come from a multiway speaker with large amp background, this combination is always going to sound light and unsatisfying.
My take on the whole thing is the singe driver / horn / SET devotees are interested in simplicity, purity of tone, presence, and clarity. That is a very diffent set of objectives to other audionuts who want dynamics, bass, scale, or home theatre applications.
Maybe your idea of a 4inch plus sub would be better. I think if you spent a chunk of cash on an SET you may still be disatisfied with your bass as they are not really built for that large scale application. If you have bought the 208 second hand, they should already be pretty much run in, so I dont know your sound is going to change as much as if they were just new.
I like the 208 combination and encourage you to keep going and tweaking, but just be aware of its limitations, and try not to throw too much money at it. I like using multistrand copper wire as I found the single strand copper of the Cat 5 was too bright in my system and seemed to amplify the stridency and sibilance that can come from the 208 with this combination. The multistrand settled things down a bit, and gave me better bass weight (at the expense of bass definition).
Have fun
Adam
I was wondering how the attenuators might sound. I have long thought about them to equlise the T90 with the 208 - can you tell much of a difference if they are removed and just a cap of 1.5 between the two?
1mm of xmax means the speaker cone does not move in and out very much. In order to get real bass, you need to move air (its a physics thing). many sub woofers have an excursion of 10mm or higher. This combined with a larger cone area means they move more air, and give more bass. The whole idea of the horn behind the cone is to take that small cone movement and amplify it down a line. The horn only works for frequencies below about 300hz. So what you dont want going down the line is the midrange that is also contained in the rear wave. The compression chamber somewhat controls that, but you also get some spillover which goes down the line and can blur the sound. So thats where damping comes in to damp out the unwanted mid range going down the horn.
The 45 amp is from a local builder here in Melbourne Weston Accoustics. He has a website, but predominantly builds for a vibrant local market here in Australia. This tube only puts out 1.8w per channel, so it is never going to give thumping bass nor is any other amp as the physics of the 208 driver will just not allow deep thumping bass. For that you will need a subwoofer regardeless. If you want clear well defined bass in unison with the music, then a SET/horn set up is great. However, if you have come from a multiway speaker with large amp background, this combination is always going to sound light and unsatisfying.
My take on the whole thing is the singe driver / horn / SET devotees are interested in simplicity, purity of tone, presence, and clarity. That is a very diffent set of objectives to other audionuts who want dynamics, bass, scale, or home theatre applications.
Maybe your idea of a 4inch plus sub would be better. I think if you spent a chunk of cash on an SET you may still be disatisfied with your bass as they are not really built for that large scale application. If you have bought the 208 second hand, they should already be pretty much run in, so I dont know your sound is going to change as much as if they were just new.
I like the 208 combination and encourage you to keep going and tweaking, but just be aware of its limitations, and try not to throw too much money at it. I like using multistrand copper wire as I found the single strand copper of the Cat 5 was too bright in my system and seemed to amplify the stridency and sibilance that can come from the 208 with this combination. The multistrand settled things down a bit, and gave me better bass weight (at the expense of bass definition).
Have fun
Adam
Hi Adam,
I've tried the T90A's without the cap and without the attenuator. Obviously no cap means too much mid was coming through. And no attenuator meant the tops were a little too much, I could have lived with it, but have found that equalizing the SLP by reducing the T90a's input by 6dB was perfect. The beauty of the attenuator is that you can alter the tops between recordings, but I've found that -6dB is good for most.
My SEX amp is 2w, so 1.8 wouldn't cut it for me. I think I need another 2 watts to produce the sound I want. I'm having to turn the volume up full, which is never a good sign. I think that monoblocks might be the way to go in the future.
What I don't understand is the impedance/gain. I have the amp impedance switch at 8ohms, to match the speakers. However, I could up the gain to give more power, but I don't know if this would damage the driver/tweeter as I'd have an output impedance of 32 or 64ohms. I don't understand impedance, it seems to me like a 'boost' switch to give more power - but I know I'm wrong.
Found a 30 band active equalizer on ebay for under £100, might give it a go.
I don't know if the drivers had been used much by the previous owner - I don't think he'd had them for long (probably sold them before they'd hit their potential).
I read about people bi-amping a full range driver & sub set up; with a SET amp for the former, and a SS amp for the sub. This might be another possibility for future plans. I've also seen SET amps with a sub output (with xover), so that's another idea.
I have noticed that the 208 driver doesn't move much, I can see now how this could give greater detail, but less bass.
It's a massive learning experience for me, and I know I'm only at the tip of the iceberg.
Cheers for the help,
Adrian
I've tried the T90A's without the cap and without the attenuator. Obviously no cap means too much mid was coming through. And no attenuator meant the tops were a little too much, I could have lived with it, but have found that equalizing the SLP by reducing the T90a's input by 6dB was perfect. The beauty of the attenuator is that you can alter the tops between recordings, but I've found that -6dB is good for most.
My SEX amp is 2w, so 1.8 wouldn't cut it for me. I think I need another 2 watts to produce the sound I want. I'm having to turn the volume up full, which is never a good sign. I think that monoblocks might be the way to go in the future.
What I don't understand is the impedance/gain. I have the amp impedance switch at 8ohms, to match the speakers. However, I could up the gain to give more power, but I don't know if this would damage the driver/tweeter as I'd have an output impedance of 32 or 64ohms. I don't understand impedance, it seems to me like a 'boost' switch to give more power - but I know I'm wrong.
Found a 30 band active equalizer on ebay for under £100, might give it a go.
I don't know if the drivers had been used much by the previous owner - I don't think he'd had them for long (probably sold them before they'd hit their potential).
I read about people bi-amping a full range driver & sub set up; with a SET amp for the former, and a SS amp for the sub. This might be another possibility for future plans. I've also seen SET amps with a sub output (with xover), so that's another idea.
I have noticed that the 208 driver doesn't move much, I can see now how this could give greater detail, but less bass.
It's a massive learning experience for me, and I know I'm only at the tip of the iceberg.
Cheers for the help,
Adrian
HI again Adrian
Thanks for the info on the transformers...very interesting.
To be fair to the 208, it sounds like the SEX amp is not up to it if you are having gain/volume troubles.
My 1.8 watt 45 amp goes too loud for ordinary evening listening, but is great for a party when we get the 70's vinyl happening with a few beers. Most nights my listening is done between 10 and 12 on the dial, the designer tells me this is pretty optimal. When I get to 3 on the dial, thats the time to start dancing! I wonder if you could try another amp (or borrow one) and see if it gives you more boost. I would hate for your view on the 208 to be formed using just this amp.
You can add a sub and retain the SET amp with something like this:
Speaker (High Level) to Line Level Converter - Jaycar Electronics
I havent tried it, but I think that might give you bass that is lacking.
The whole thing is a journey - I havent stopped yet either. I have some v-cap capacitors coming from the US for decoupling caps in my amp - I am looking forward to hearing what the hype is all about.
I somehow think things will never be perfect, but last night when I listened for a while, and turned around and an hour and a half had gone by, I think 'this is a great hobby'!!
have fun ...Adam.
Thanks for the info on the transformers...very interesting.
To be fair to the 208, it sounds like the SEX amp is not up to it if you are having gain/volume troubles.
My 1.8 watt 45 amp goes too loud for ordinary evening listening, but is great for a party when we get the 70's vinyl happening with a few beers. Most nights my listening is done between 10 and 12 on the dial, the designer tells me this is pretty optimal. When I get to 3 on the dial, thats the time to start dancing! I wonder if you could try another amp (or borrow one) and see if it gives you more boost. I would hate for your view on the 208 to be formed using just this amp.
You can add a sub and retain the SET amp with something like this:
Speaker (High Level) to Line Level Converter - Jaycar Electronics
I havent tried it, but I think that might give you bass that is lacking.
The whole thing is a journey - I havent stopped yet either. I have some v-cap capacitors coming from the US for decoupling caps in my amp - I am looking forward to hearing what the hype is all about.
I somehow think things will never be perfect, but last night when I listened for a while, and turned around and an hour and a half had gone by, I think 'this is a great hobby'!!
have fun ...Adam.
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