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Old 30th March 2011, 04:14 PM   #11
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Hi Roger,

Good transformers make a great difference to sound. I thought I had good sound, but when I put on a pair of really good transformers, I didn't want to go back to the old ones.

Making good transformers for full range ESL is not easy at all.

Wachara C.
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Old 30th March 2011, 04:36 PM   #12
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Are the Dayton-Wright speakers the ones best to win the full-range trophy? Good output below 60 Hz. But even so, there's no magic method for keeping the impedance in a tolerable range down there.

Each transformer (conventional winding, I believe) weighs 41 lbs. They were created by a transformer guru at Hammond Transformers.

I wonder if some of these "interface units" are floating around? They don't get attacked by cats, after all.

I suppose all of us think this is pure Don Quixote hubris, making bass with an ESL. But I gotta say, "WOW, fascinating idea... wonder what it sounds like". Not sure there are serious objections to using cones for sub-woofer and everybody does it. But I sure am curious about the sound. "Fast bass" eh? How many sq meters of film?
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Last edited by bentoronto; 30th March 2011 at 04:40 PM.
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Old 30th March 2011, 04:48 PM   #13
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Hi
Power transformers have a greater “leakage inductance” than say tube output transformers BUT other than that work the same way.
The power transformers I have measured, often were just fine for audio up to 500-1KHz.

All cored transformers have a maximum flux which is permissible, working through the math, one finds this puts a limit on how much voltage per turn can be tolerated AT some frequency.

Thus, if one used a transformer which was designed to have 110 volts across a winding at 60Hz, one knows then that at 30Hz, the maximum Voltage is half that and at 15Hz half of that again.

So, if you know your max input voltage and frequency, you can scale up to find what the input side spec’s should look like.
On the output, you need a pretty large step up ratio so you might look at more of a high voltage power transformer.
Best,
Tom Danley
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Old 30th March 2011, 04:52 PM   #14
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You can look at this site : Transformator Elektrostaten Audio 4 for a transformer
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Old 30th March 2011, 05:47 PM   #15
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Again this is very true.

I got an incredibly beautiful fullrange sound out of my mini panel at a low level.

But at a more progessive level bass quality quickly diminished.

I last year I was going to get some huge cores but other things came up and now I'll have to wait, hopfully not very long,because I too would like to explore a bass panel setup.

I having been batting around Idea the of a fold panel design with a surface area of at least 32 square feet. jer
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Old 30th March 2011, 06:37 PM   #16
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Quote:
Originally Posted by Tom Danley View Post
Hi
Power transformers have a greater “leakage inductance” than say tube output transformers BUT other than that work the same way.
The power transformers I have measured, often were just fine for audio up to 500-1KHz.
You may find it useful to know that most modern toroidal power transformers in the 60VA to 200VA have surprisingly low leakage inductance. Most will drive 500pF - 1000pF ESL panels with an upper bandwidth limit of 25kHz - 40kHz. The only limitation is that of core saturation which restricts their use to hybrids with crossovers at 300Hz and above.
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Old 30th March 2011, 06:56 PM   #17
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Quote:
Originally Posted by SM7UYJ View Post
bolserst:

I may have totaly confused my measurements, but as I recal I got about 1V/turn on my 400VA trafo!?

With 12 turns on my LV side I get a transformation ratio off abt. 1:20.

This should make things a bit easier as to ad windings to the HV side, but I definitly get what you are saying!

I'm beginning to think that my setup perhaps is good enough as it is!

The bass panel plays with good output from ~30Hz and I get distorsion only when I crank my small 60W amp up to 75%.

Roger
Sounds like your transformer was designed with a larger core size than the 400VA units I have tested. As you stated, this allows the use of fewer turns on both the HV and LV side and makes things easier for you if you decided to try and add turns to the windings.

On the topic of core saturation and distortion.
Our ears are pretty forgiving of distortion at LF. Especially low order harmonics(2nd & 3rd) which dominate at the onset of core saturation. So you can be pushing your bass transformers into saturation onset and not notice it. If you are hearing audible distortion, you are probably driving the transformer into, or close to, hard saturation.

Transformer core saturation is not an all or nothing event. At the onset of saturation the current in the LV winding stops following the applied voltage. In particular, if you monitor the current, you will notice current spikes on top of the audio signal. As you push further and further into saturation, the magnitude of the spikes grow. Hard saturation is reached when the current is limited only by the DC resistance of the winding and any series resistor added between the LV winding and the amplifier. This is a good reason to always use at least a 1 ohm resistor in series with the LV winding of a bass transformer to protect your amplifier.
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Old 30th March 2011, 07:11 PM   #18
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I just tried to hook up four 12V/240V/400VA toroids to my bass panel, and I now have to turn the volume to nearly max to hear distorsion - amp clipping or saturation - I have not measured !?

For now, I think I'll try 6 pcs 400VA in my speakers - if I can get them to fit in the box!

Roger
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Old 30th March 2011, 07:14 PM   #19
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Quote:
Originally Posted by bentoronto View Post
Are the Dayton-Wright speakers the ones best to win the full-range trophy? Good output below 60 Hz. But even so, there's no magic method for keeping the impedance in a tolerable range down there.

Each transformer (conventional winding, I believe) weighs 41 lbs. They were created by a transformer guru at Hammond Transformers.
The only truly full range ESL I have been able to measure was a Sound Lab A-1. It had solid output below 30Hz. Their interface unit uses a nearly identical setup to Acoustat where they have a large bass transformer with high turns count and high leakage inductance mixed with a toroidal treble transformer with low turns count and low leakage inductance. The toridal transformer is only driven above about 250Hz.

Since this is a thread about ESL Bass transformers, here are a few particulars on the Acoustat and Sound Lab bass transformers.

Acoustat 1+1 bass transformer: step-up ratio(250:1)
EI transformer with core = 3.0 in^2 = 19.4 cm^2
Primary winding = 40 turns
Secondary winding = 10,000 turns

Soundlab A-1 bass transformer: step-up ratio(200:1)
EI transformer with core = 4.5 in^2 = 29 cm^2
Primary winding = 120 turns
Secondary winding = 24,000 turns

Now you can see why I call the Soundlab truly full range.
Onset of saturation is not reached at 30Hz till 50Vrms!
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Old 30th March 2011, 07:33 PM   #20
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Bolserst wrote “You may find it useful to know that most modern toroidal power transformers in the 60VA to 200VA have surprisingly low leakage inductance. Most will drive 500pF - 1000pF ESL panels with an upper bandwidth limit of 25kHz - 40kHz. The only limitation is that of core saturation which restricts their use to hybrids with crossovers at 300Hz and above.”

That is interesting, all of the ones I had measured were larger and EI cores.

“Now you can see why I call the Soundlab truly full range.

Onset of saturation is not reached at 30Hz till 50Vrms!”

That is a studly transformer.
In American power transformer terms, it would be happy with 100V @60Hz on the primary and would have 20KV on the output.

What you’re looking for here is a high voltage power transformer, not a low voltage unit.

If you want to put bass through it, it has to have a higher voltage primary / input.
Remember what ever the design voltage is at 50 or 60Hz, it will reach the same core flux at half the voltage AT half the frequency.

Search out a Neon sign transformer, oil burner igniter or high voltage power transformer with a 110V primary. These will have more leakage L BUT who cares if it’s a low frequency speaker.
Best,
Tom Danley
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