Looks good I think that you should be able to get down to around 300hz to 400hz maybe a little lower.
This is considering it is mounted in a frame with a 1" wide border.
My only concern is what are you going to drive it with?
Your area is about 10% less than 3 of my little panels.
It took all three panels to closely match the efficiency of my 5.25" woofer.
The details are a little vague as it was two years ago but some were documented in one of the threads.
I will try do some tests to get some exact figures for you.
I do know that I was possiblily using turns ratio of around 1:200 or higher and a Bias voltage of 5Kv or so to get there.
This was about 150pf of panel capacitance + about 600 pf (average) of transformer and a 1:100 ratio will present a 1 ohm load to the amplifier at 20Khz.
According to Bolserst if you used the Antek transformers,their capacitance is a bit on the high side of 1000pf although they have been used with great success with larger panels.
As an example your panel will have around 150pf and the antek's will have around 1:74 ratio,So with the added capacitance this come out to a 1.26 ohm impedance that the amp will see at 20khz.
If you doubled to length to 36" this increases the efficiency of the panel by 3db.
And yes this doubles the panels capacitance but only drops the impedance by a small margin due to the high capapcitance of the transformer to 1.117 ohms at 20khz.
But,since you have an increase of 3db in the panel efficiency the amp has to produce only 70.7% of the voltage ( or half the power) to produce the same SPL as that of a panel half its size.
A lot to gain for such a small decrease in impedance this makes it much easier on the amp although you still need to have an amp that can supply that kind of current should you want to crank it up once in a while.
Now for example you were to increase the area by another factor of 4 this would give you a total increase of +9db from where you started with your original size.
Let's say this is +10db increase and that is the difference between 1watt and 100watts of driving power for the same amount of SPL.
Lets see what happened to the impedance,
Our capacitance would now be 2200pf and this equates to .66 ohms at 20khz but if you include a series resistor of 1 ohm, this is now 1.66ohms that the amplifier see as a load.
But with the 10db( or 9db in our example) increase in panel efficiency the amp only has to work 1/10 as hard and has plenty of room to make up the difference of the added resistance should it be used.
This why surface area is so important.
If you plan on pursuing the winding of your own transformer then this can greatly reduce the transformer capacitance making it much more efficient to drive smaller panels.
This is where I am at right now.
So I am sorry to say that I don't have recipe to go by as of yet to build one.
But it is something that I will be working on more.
Now that I have everything set backup again.
jer 🙂
P.S. This is where I'm at just to give you in idea,
http://www.diyaudio.com/forums/plan...p-up-measurements-part-1-2-a.html#post2864507
The most my little amp would do with music is about 2Vrms to 4Vrms max and about 10v peak, with a 500 hz to 2khz steady test tone at 10v peak with a 1:330 ratio and no resistor,this was 1ohm(and 100watts)at 2Khz and about 98db at .5 meter,as this was the very First quick test.
OOps !!! I forgot that I already posted this data earlier in this thread! he,he,he
This is considering it is mounted in a frame with a 1" wide border.
My only concern is what are you going to drive it with?
Your area is about 10% less than 3 of my little panels.
It took all three panels to closely match the efficiency of my 5.25" woofer.
The details are a little vague as it was two years ago but some were documented in one of the threads.
I will try do some tests to get some exact figures for you.
I do know that I was possiblily using turns ratio of around 1:200 or higher and a Bias voltage of 5Kv or so to get there.
This was about 150pf of panel capacitance + about 600 pf (average) of transformer and a 1:100 ratio will present a 1 ohm load to the amplifier at 20Khz.
According to Bolserst if you used the Antek transformers,their capacitance is a bit on the high side of 1000pf although they have been used with great success with larger panels.
As an example your panel will have around 150pf and the antek's will have around 1:74 ratio,So with the added capacitance this come out to a 1.26 ohm impedance that the amp will see at 20khz.
If you doubled to length to 36" this increases the efficiency of the panel by 3db.
And yes this doubles the panels capacitance but only drops the impedance by a small margin due to the high capapcitance of the transformer to 1.117 ohms at 20khz.
But,since you have an increase of 3db in the panel efficiency the amp has to produce only 70.7% of the voltage ( or half the power) to produce the same SPL as that of a panel half its size.
A lot to gain for such a small decrease in impedance this makes it much easier on the amp although you still need to have an amp that can supply that kind of current should you want to crank it up once in a while.
Now for example you were to increase the area by another factor of 4 this would give you a total increase of +9db from where you started with your original size.
Let's say this is +10db increase and that is the difference between 1watt and 100watts of driving power for the same amount of SPL.
Lets see what happened to the impedance,
Our capacitance would now be 2200pf and this equates to .66 ohms at 20khz but if you include a series resistor of 1 ohm, this is now 1.66ohms that the amplifier see as a load.
But with the 10db( or 9db in our example) increase in panel efficiency the amp only has to work 1/10 as hard and has plenty of room to make up the difference of the added resistance should it be used.
This why surface area is so important.
If you plan on pursuing the winding of your own transformer then this can greatly reduce the transformer capacitance making it much more efficient to drive smaller panels.
This is where I am at right now.
So I am sorry to say that I don't have recipe to go by as of yet to build one.
But it is something that I will be working on more.
Now that I have everything set backup again.
jer 🙂
P.S. This is where I'm at just to give you in idea,
http://www.diyaudio.com/forums/plan...p-up-measurements-part-1-2-a.html#post2864507
The most my little amp would do with music is about 2Vrms to 4Vrms max and about 10v peak, with a 500 hz to 2khz steady test tone at 10v peak with a 1:330 ratio and no resistor,this was 1ohm(and 100watts)at 2Khz and about 98db at .5 meter,as this was the very First quick test.
OOps !!! I forgot that I already posted this data earlier in this thread! he,he,he
Last edited:
Ok thanks that actually helped a lot. I'll have to see how big I can comfortably make them without renovating my room...
I would assume that self wound transformers ate cheaper so yeah ill probably look into that. How hard could it be....
As I'm on a killer (in a bad way) budget, what do you think the cheapest passable amp would be to drive such a tricky load, I'm willing to make my own also if it could save me a significant amount
Luckily I might have someone who wants to commission some desktop speakers so I may have a minor boost to my cash flow soon 😀
I would assume that self wound transformers ate cheaper so yeah ill probably look into that. How hard could it be....
As I'm on a killer (in a bad way) budget, what do you think the cheapest passable amp would be to drive such a tricky load, I'm willing to make my own also if it could save me a significant amount
Luckily I might have someone who wants to commission some desktop speakers so I may have a minor boost to my cash flow soon 😀
A self wound transformer won't be cheaper but it will yield a better performance margin as far as wasted power in the transformer because of the lowered residual capacitance that it adds.
This will also move any self resonances well above the audio band reducing the need of any extra added resistances.
Many have had good success (as well as I) using a pair of common toroid power transformers with there larger panels providing you have a decent power amp.
I was and still am on the quest of a suitable DIY amplifier although I do have several large professional amps to choose from.
I have batted around a few ideas from a classic simple class b push-pull high current transistor design driving the transformer with a center tapped primary.
Such as Susan Parkers configuration using mosfets, or just some common high power BJT's such as some 2N3055 or more linear types like the 2N2772,2N3773 or some of the newer types that are available like the 2SC5200.
Or a highly paralleled chipamp using the LM3886 or LM4780's.
I have five LM4780's but I have not messed with them yet.
Here is an amp That I was planning to try as I had tweaked it in circuit maker for this particular use and uses junkbox parts that were quite common back in the day in amplifier designs, and are still available cheaply.
I have many similar design like this, But I do like this configuration,
http://www.diyaudio.com/forums/solid-state/167394-quasi-amplifier-beginners-10.html#post2680070
http://www.diyaudio.com/forums/solid-state/167394-quasi-amplifier-beginners-10.html#post2812503
http://www.diyaudio.com/forums/solid-state/167394-quasi-amplifier-beginners-10.html#post2812521
http://www.diyaudio.com/forums/solid-state/167394-quasi-amplifier-beginners-10.html#post2845377
or this may work very well,
http://www.diyaudio.com/forums/solid-state/167394-quasi-amplifier-beginners-10.html#post2677882
apex audio has some very nice designs as well and he has referred me to try his FB400,
Leaving Facebook... | Facebook
as well as many others and more recent designs that are documented in these threads.
Any good power amp in the 100 watt to 200watt range or better that can do well with a 2 ohm load should be good.
I don't mean a 100watt amp with two output devices, more like 3 or 4 or more pairs.
Watch Ebay for a good deal on amps as well.
A few DIYer's have had good luck with the ole' Adcom's and can be found rather cheaply on ebay as well as others.
Decent power amps are much cheaper these days than they used to be.
A very simple powerful and High Quality low cost amps have been made using the LMX48XXX series of driver chips and are almost unbeatable with very impressive specs,
http://www.diyaudio.com/forums/soli...sed-lme49830-lateral-mosfets.html#post2717072
I have seen high power amp kits using these on ebay for less than $30 to $50 for the board and the parts to populated it.
Incredible deals,But as always buyer beware and research them first, as many of those can be found in these threads and seem to be okay.
I Had found a 500watt amp like that for about $35 and I couldn't have made the board and populated it with half of the parts for that amount of money!
That's about 1/2 off But you still have to add a case,power transformer and heatsinks!
Still very affordable for what it is worth if you don't mind building it yourself.
There are many many options available.
But these are the things I look for.
An amp that can do a voltage swing of 30v to 40v or better,
And is stable down to 2 ohms.
The occasional 1ohm peaks at 20khz won't bother an amp of this capability in moderate use,unless you crank it alot and trust me these things can get incredibly loud so I doubt that this would be much of an issue.
My crown DC300A is rated for a 60peak swing or 15 amps which ever comes first ,
http://www.google.com/url?sa=t&rct=...6KT6Cw&usg=AFQjCNFgFmfo09_-6JB930RGUmgqiF1Q_Q
http://www.google.com/url?sa=t&rct=...6KT6Cw&usg=AFQjCNFv9UDH3xIZzDmAraaACAgabJOZ-g
This is an oldie but goodie brute of an amplifier and it doesn't have the greatest specs or high end like today's designs, But, it works and I got cheap from a pawn shop in the late 90's and never had a problem with it so far.
Due to the small heat sinks I have heat cycled this thing all day long many times(at full power) and it just keeps chugging along on a 1.6 ohm load.
I posted the links to the manuals just to give you an idea as they have some great charts in them.
There are plenty of design of this caliber that are better, But I like it and it serves me well !
jer 🙂
This will also move any self resonances well above the audio band reducing the need of any extra added resistances.
Many have had good success (as well as I) using a pair of common toroid power transformers with there larger panels providing you have a decent power amp.
I was and still am on the quest of a suitable DIY amplifier although I do have several large professional amps to choose from.
I have batted around a few ideas from a classic simple class b push-pull high current transistor design driving the transformer with a center tapped primary.
Such as Susan Parkers configuration using mosfets, or just some common high power BJT's such as some 2N3055 or more linear types like the 2N2772,2N3773 or some of the newer types that are available like the 2SC5200.
Or a highly paralleled chipamp using the LM3886 or LM4780's.
I have five LM4780's but I have not messed with them yet.
Here is an amp That I was planning to try as I had tweaked it in circuit maker for this particular use and uses junkbox parts that were quite common back in the day in amplifier designs, and are still available cheaply.
I have many similar design like this, But I do like this configuration,
http://www.diyaudio.com/forums/solid-state/167394-quasi-amplifier-beginners-10.html#post2680070
http://www.diyaudio.com/forums/solid-state/167394-quasi-amplifier-beginners-10.html#post2812503
http://www.diyaudio.com/forums/solid-state/167394-quasi-amplifier-beginners-10.html#post2812521
http://www.diyaudio.com/forums/solid-state/167394-quasi-amplifier-beginners-10.html#post2845377
or this may work very well,
http://www.diyaudio.com/forums/solid-state/167394-quasi-amplifier-beginners-10.html#post2677882
apex audio has some very nice designs as well and he has referred me to try his FB400,
Leaving Facebook... | Facebook
as well as many others and more recent designs that are documented in these threads.
Any good power amp in the 100 watt to 200watt range or better that can do well with a 2 ohm load should be good.
I don't mean a 100watt amp with two output devices, more like 3 or 4 or more pairs.
Watch Ebay for a good deal on amps as well.
A few DIYer's have had good luck with the ole' Adcom's and can be found rather cheaply on ebay as well as others.
Decent power amps are much cheaper these days than they used to be.
A very simple powerful and High Quality low cost amps have been made using the LMX48XXX series of driver chips and are almost unbeatable with very impressive specs,
http://www.diyaudio.com/forums/soli...sed-lme49830-lateral-mosfets.html#post2717072
I have seen high power amp kits using these on ebay for less than $30 to $50 for the board and the parts to populated it.
Incredible deals,But as always buyer beware and research them first, as many of those can be found in these threads and seem to be okay.
I Had found a 500watt amp like that for about $35 and I couldn't have made the board and populated it with half of the parts for that amount of money!
That's about 1/2 off But you still have to add a case,power transformer and heatsinks!
Still very affordable for what it is worth if you don't mind building it yourself.
There are many many options available.
But these are the things I look for.
An amp that can do a voltage swing of 30v to 40v or better,
And is stable down to 2 ohms.
The occasional 1ohm peaks at 20khz won't bother an amp of this capability in moderate use,unless you crank it alot and trust me these things can get incredibly loud so I doubt that this would be much of an issue.
My crown DC300A is rated for a 60peak swing or 15 amps which ever comes first ,
http://www.google.com/url?sa=t&rct=...6KT6Cw&usg=AFQjCNFgFmfo09_-6JB930RGUmgqiF1Q_Q
http://www.google.com/url?sa=t&rct=...6KT6Cw&usg=AFQjCNFv9UDH3xIZzDmAraaACAgabJOZ-g
This is an oldie but goodie brute of an amplifier and it doesn't have the greatest specs or high end like today's designs, But, it works and I got cheap from a pawn shop in the late 90's and never had a problem with it so far.
Due to the small heat sinks I have heat cycled this thing all day long many times(at full power) and it just keeps chugging along on a 1.6 ohm load.
I posted the links to the manuals just to give you an idea as they have some great charts in them.
There are plenty of design of this caliber that are better, But I like it and it serves me well !
jer 🙂
I'll vouch for the old Adcom power amps. They are built like tanks. The GFA-545 can often be had for under $100, from ebay. When I first got my Magnepan speakers, I bought two GFA-545 mk II amps (designed by Nelson Pass, by the way), because they were so cheap, and were like new. Wow they sound good. Later, I also got a GFA-585 (not exactly cheap, though), because it's rated to do 400 W/ch into 4 Ohms, and 1000 W/ch continuously into 1 Ohm! (And its distortion specs are even better than the GFA-545 II.)
Our friend Mavric has some 16x40 ESL panels coupled to pairs of toroidal trannys, and he drives them to very high volume with a pair of the little 100 w/ch Adcom amps-- sounds great too.
Yes,I have heard those things and get they right up there for sure !!!!
I was talking to him on the phone one day ,and ,I could hear those things plain as day and crystal clear with absolutely no distortion while he was out side on his porch with all of the doors and windows shut !!!!
Mavric !!
jer 🙂
I was talking to him on the phone one day ,and ,I could hear those things plain as day and crystal clear with absolutely no distortion while he was out side on his porch with all of the doors and windows shut !!!!
Mavric !!jer 🙂
Alright I think that GFA-545 II might be the way to go for me. When I get some budget I'll start watching for it on ebay. I just built some desktop full rangers (its amazing what a 3in speaker can do) that I plan to sell so if that works out I may have a new source of income...
This really must be unhealthy, its like an addiction. I finished my main speakers like a week ago and I already want to start on more. At least I have an excuse to make some electrostatics 😀
Once again thanks for all the info guys! Y'alls' (yeah its a word) eagerness to help always astounds me
This really must be unhealthy, its like an addiction. I finished my main speakers like a week ago and I already want to start on more. At least I have an excuse to make some electrostatics 😀
Once again thanks for all the info guys! Y'alls' (yeah its a word) eagerness to help always astounds me
Addiction? Yes very much so !!!!
It is a goal that pays off well in the end !
Amps and transformers are the issues I plan on tackling with full force this year kind of where I left off in July of 2010.
Although I have amps covered, I want a dedicated amp for the ESL's and save my pro amps for other things.
But a DIY friendly transformer build is my main goal and was why I had stopped in 2004 and then re-started again 2010.
jer 🙂
It is a goal that pays off well in the end !
Amps and transformers are the issues I plan on tackling with full force this year kind of where I left off in July of 2010.
Although I have amps covered, I want a dedicated amp for the ESL's and save my pro amps for other things.
But a DIY friendly transformer build is my main goal and was why I had stopped in 2004 and then re-started again 2010.
jer 🙂
I think that the GFA-565 is the monoblock version, which is probably what you were thinking of. The GFA-585, which is the one that I have, is supposed to be like two of those in one case. But, it has only one transformer, while the purist in me would have wanted two. Still, I have not noticed ANY deficiency, due to that.
Last line in the seller's ebay description: "She'll bring the thunder!!".
And how true it is. The only thing I have to worry about, with this amp, is instant speaker destruction. When my son was using it, he said that the remote-controlled motorized volume knob on my preamp got "stuck" in clockwise mode. Blew the tweeter fuses in both of my Magnepan MG-12s! Still had both of the factory-supplied replacement fuses that came with them. So that was probably the first time either of them had been blown. Many people bypass those fuses, "to improve the sound". Glad I didn't!!
I also have Vandersteen 2Ce speakers that I use with that amp and there are certain things that I like to play loud that usually end up lighting up the "over temp" warning lights in those speakers. I didn't even know they HAD over-temp warning lights, until I got this amp!
And I read somewhere on line where a guy who had the same amp turned it up "really loud" and went into another room. When he came back, one of his speakers was fully engulfed in flames(!), while the amp was still just happily playing on. <yikes!>
Now I'm thinking that maybe I should install some sort of mechanical stop on the GFP-500 II preamp's volume knob, so it can't go up past, say, the 1:00 position. It's plenty loud with the Magnepans when the knob is at the 9:30-10:00 position, and is about twice as loud with the Vandersteens, for any setting. And when I do feel like cranking it to insanely-loud levels, I've never gone past the 1:00 position. I don't want to permanently disfigure the knob or faceplate so maybe I could use a small hose clamp (over a strip of thin rubber) with the short side of a small L-bracket under the clamp, such that the long side of the bracket would contact something when the knob got to 1:00.
Cheers,
Tom
Yes, I remember the GFA-565 when it came out and then they did GFA-585.
I wanted to get the GFA-585 to power my Infinity SM-150's at the time.
Sadly we never got one and the Infinity's are long gone now,I did mange to keep the crossovers though,The suffered foam cancer. he,he
My Ashley FTX-2000 is one to contend with though rated at 675 in to 2ohms and I am running 1.6 ohms on it.
As with all of my amp I picked it up cheap in a pawn shop.
http://www.google.com/url?sa=t&rct=...6oD7Cw&usg=AFQjCNHpKQoUzNyZngor1sL-a9Abkhv4mg
jer 🙂
I wanted to get the GFA-585 to power my Infinity SM-150's at the time.
Sadly we never got one and the Infinity's are long gone now,I did mange to keep the crossovers though,The suffered foam cancer. he,he
My Ashley FTX-2000 is one to contend with though rated at 675 in to 2ohms and I am running 1.6 ohms on it.
As with all of my amp I picked it up cheap in a pawn shop.
http://www.google.com/url?sa=t&rct=...6oD7Cw&usg=AFQjCNHpKQoUzNyZngor1sL-a9Abkhv4mg
jer 🙂
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