I'm planning to build a pair of hybrid esl's, de bass going to be a 12" dipole woofer per side. The esl is propably going to be a panel of 20 cm width and 50 cm height, with stators made of wire. As a step up tranformer i want to use a pair of standard 220v/6v transformers per side, are http://www.ratoshop.be/transformatoren/ringkern/100000979c0c62825.html]this[/URL] transformer capable of doing the job? the site is in dutch but i think/hope you understand the specs.
(Sorry for writing english the wrong way, i have no problems to read is but writing it is an other thing
)
(Sorry for writing english the wrong way, i have no problems to read is but writing it is an other thing
)Sorry i have done something wrong, the correct url should be:
http://www.ratoshop.be/transformatoren/ringkern/100000979c0c62825.html
http://www.ratoshop.be/transformatoren/ringkern/100000979c0c62825.html
If they are any good for audio is difficult to tell, you have to get one and measure it.
I fear a 15VA model is not terrible large, I would consider switching to a larger model. Depends on crossover freq, but with a 12" sub I suppose you want to crossover below 150hz?
You might want to consider a higher panel, will give you more output and better imaging (line source).
Btw what woofer do you plan to use for the dipole?
I fear a 15VA model is not terrible large, I would consider switching to a larger model. Depends on crossover freq, but with a 12" sub I suppose you want to crossover below 150hz?
You might want to consider a higher panel, will give you more output and better imaging (line source).
Btw what woofer do you plan to use for the dipole?
Thanks for your answer Maudio, the problem is that i don't have the equipment to measure the transformers, how large do you thinks the transformers should be? 30/50Va?
I don't know yet how low a want to set the crossover, i want to build a measurement microphone first so i can measure the frequence response of the woofers.
I have a couple of units who are produced with different names like skytronix and xxl, the are not verry expensive but, the are made of aluminium, have a fs of 23 hz and produce 97db/w
Some specs:
Référence : PAW 305
Diamètre ext : 310 mm
Bande passante : 20 - 2000 Hz
Puissance maxi RMS : 450 W/215 W
Sensibilité : 97 dB
Fréquence de résonance : 23 Hz
Impédance : 8 ?
Poids : 4850 g
Normally i would not buy speakers of this brand but because dipole woofers are not that critic, i like to give them a try.
I don't know yet how low a want to set the crossover, i want to build a measurement microphone first so i can measure the frequence response of the woofers.
I have a couple of units who are produced with different names like skytronix and xxl, the are not verry expensive but, the are made of aluminium, have a fs of 23 hz and produce 97db/w
Some specs:
Référence : PAW 305
Diamètre ext : 310 mm
Bande passante : 20 - 2000 Hz
Puissance maxi RMS : 450 W/215 W
Sensibilité : 97 dB
Fréquence de résonance : 23 Hz
Impédance : 8 ?
Poids : 4850 g
An externally hosted image should be here but it was not working when we last tested it.
Normally i would not buy speakers of this brand but because dipole woofers are not that critic, i like to give them a try.
Hi, badduh.
I_Forgot talks about toroid transformers in this post. He feels 30VA should be fine.
There's a lot of variables in ESL building, so you'll probably have to build your ESLs and measure their low end cutoff to find your initial crossover frequency. Then listen and adjust the crossover as needed to blend in with the woofers. A computer and soundcard with crossover software will make this quite easy.
I agree with maudio about the size of the ESL, bigger is better.
I_Forgot talks about toroid transformers in this post. He feels 30VA should be fine.
There's a lot of variables in ESL building, so you'll probably have to build your ESLs and measure their low end cutoff to find your initial crossover frequency. Then listen and adjust the crossover as needed to blend in with the woofers. A computer and soundcard with crossover software will make this quite easy.
I agree with maudio about the size of the ESL, bigger is better.
BillH said:
I should make it clear that I have not yet tried the power transformer trick. My speculation that 30W transformers should be adequate is based on using one or two 30W audio output transformers per speaker and finding them adequate. There are others lurking about this forum who have used power transformers in lieu of audio output transformers and can tell you their actual experience.
Power transformer ratings are based in part on the frequency of operation and the size of the core. They are almost always spec'd at 50 or 60 Hz. Audio transformer power ratings are based on the same things, but thanks to the marketing guys, their power ratings may be quoted at different frequencies. Based on this, a 30VA power transformer should be good for 30W of audio at 50-60Hz. An ESL won't use the 30W, even when playing loudly while driven by a 200W amplifier.
I will always recommend using two transformers per speaker when the builder's economic situation allows it. Power transformers are so cheap there is no reason not to use two of them per speaker.
I_F
@maudio. I become interested in dipole woofers bij this http://www.diyaudio.com/forums/showthread.php?s=&threadid=14179&highlight= thread, the conclusion of the topic was that woofers witch normally would sound horrible in a monopole setup could sound suprisenly good in a dipole setup. I had the uppertunity to buy a pair of the xxl paw-305 woofers for 40 euro, i think i can't go wrong for that. But as i mentioned before i have to measure them first, to see what they're capable of.
@iforgot Do you think it is posible to use 15Va transformers? The 30Va type is significant more expensive than the 15 Va type. On the other hand, if you think that the minimum is 30 Va i could also buy the 50 Va type because the price difference between 30 and 50 Va is only 0,5 euro. Do i understand you correctly if i say that the higher the crossover, the lower the Va has to be?
@iforgot Do you think it is posible to use 15Va transformers? The 30Va type is significant more expensive than the 15 Va type. On the other hand, if you think that the minimum is 30 Va i could also buy the 50 Va type because the price difference between 30 and 50 Va is only 0,5 euro. Do i understand you correctly if i say that the higher the crossover, the lower the Va has to be?
badduh said:
I hope you're not buying the transformers new... If you look at some surplus dealers you can usually find transformers in the 15-50VA range for $5-10 each. If you can't find cheap 30-50VA transformers, keep looking- they are out there.
15VA will work, but may not work well when you try to play at loud volumes. OTOH, if you're crossing over so the low frequencies never go to the ESLs, 15VA may be fine. If they are cheap, try them and let us know if they work.
I_F
I have searched the internet but i haven't found them second hand in europe. I also didn't vind the somewhere cheaper than the shop mentioned in my first post, The 15 Va ampere costs 13,50 euro incl. vat, i don't think that i wil find them anywhere cheaper in europe.
A have made al litle design for the speaker, i want to make something that looks like this:
A have made al litle design for the speaker, i want to make something that looks like this:
Attachments
Your ESL will have really limited vertical dispersion, so you may want to consider a taller one, or your speaker will only sound good sitting down. Mine are 4 feet tall sitting on a 1 foot tall bass module, and when I stand up (I'm 6'2"), the high frequencies disappear. It's really amazing how "laser beam" the sound is. It makes imaging and dynamics in the sweet spot really remarkable, but the smaller your panel is the smaller that sweet spot will be.
I'm really curious about the performance of power transformers as well. I've got lots of measurement gear (computer and soundcard, digital scope that I can capture waveforms, analog scopes, and function generators). If we can agree on a transformer that I can get cheaply, I'll be glad to test the snot out of it. I'd recommend the $20 50 watt toroids from digikey as a good test mule.
Also, my friend and I built both dipole and transmission line speakers and we both favored the TL's with the panels. We were using Lambda acoustics woofers that on paper should have worked about as good as anything out there for dipole service. In my experience, the room resonances weren't really any different with TL vs dipole. To be fair, I kept the dipole lined up with the panel rather than pushing it around, but I did that with the TL too. Now that I have a much bigger room, I should repeat the experiment.
Also my friend built panels about 66% of the size of my 4' x 20" panels, and the dynamics of his were not nearly as good as mine. With ESL's size does matter.
Sheldon
I'm really curious about the performance of power transformers as well. I've got lots of measurement gear (computer and soundcard, digital scope that I can capture waveforms, analog scopes, and function generators). If we can agree on a transformer that I can get cheaply, I'll be glad to test the snot out of it. I'd recommend the $20 50 watt toroids from digikey as a good test mule.
Also, my friend and I built both dipole and transmission line speakers and we both favored the TL's with the panels. We were using Lambda acoustics woofers that on paper should have worked about as good as anything out there for dipole service. In my experience, the room resonances weren't really any different with TL vs dipole. To be fair, I kept the dipole lined up with the panel rather than pushing it around, but I did that with the TL too. Now that I have a much bigger room, I should repeat the experiment.
Also my friend built panels about 66% of the size of my 4' x 20" panels, and the dynamics of his were not nearly as good as mine. With ESL's size does matter.
Sheldon
Sheldon,
When you compared dipole woofers to TLs, did you use an array of woofers in dipole mode, or just a single woofer? Also, were your friend's ESLs 66% the size of yours in both width and height, or perhaps just narrower (or just shorter)? I'm really worried that as I build a new pair of smaller ESLs I'm going to lose the dynamics that I like so much with my current panels. I don't have a clear sense of what I'll lose if I shrink the width but leave the height unchanged, for example.
Few
When you compared dipole woofers to TLs, did you use an array of woofers in dipole mode, or just a single woofer? Also, were your friend's ESLs 66% the size of yours in both width and height, or perhaps just narrower (or just shorter)? I'm really worried that as I build a new pair of smaller ESLs I'm going to lose the dynamics that I like so much with my current panels. I don't have a clear sense of what I'll lose if I shrink the width but leave the height unchanged, for example.
Few
Stokessd is right about panel hight, a small and tall panel will radiate a more or less cilindrical pattern. Above and below there isn't much to listen to.
Panel width also looks rather small to me. Smaller panels will have higher resonance frequency and it's better not to use the panel around that area. Try to aim for a resonance freq at least one octave below crossover point. With a 12" woofer you want it to be well below 100hz, which requires a panel at least 15 or 20 cm wide.
Woofer baffling: This you want to maximize. Each doubling of the baffle size will give you 6dB more woofer output which is very welcome in dipole woofers. If ou don't want to increase speaker size you can fold it to the back creating an U-baffle, but an H baffle is even better. Check out www.linkwitzlab.com/woofer.htm
Power rating of the transformer:
A higher power rating basically means it's able to deliver more current into the panel, providing the amp can deliver. A too small transformer limits bandwidth.
Large transformers will also have less turns due to bigger core area. This a a Very Good Thing in an audio transformer as less turns equals lower leakage inductance and less internal capacitances> better high freq response. So if all else is equal a bigger transformer will show much better performance. With stepuptrannies it's always balancing on the limits of physics, this is a bad place to try to save a few $$. Go as big as you can affort. Looking at commercial esl-stepup transformers you'll see core sizes equivalent to 100-500VA power transformers for full range. 2 15VA's (=30VA) is not somehing I would consider for a panel that has to play down to 150 hz or so. Better go for the 50VA's, even better use 4 smaller ones(will double output voltage).
Crossover freq is what determines the whole design. Panel dimensions, stepup requirements all depend on it. You should start with choosing a crossover frequency. Have a close look at the woofer specs.
Panel width also looks rather small to me. Smaller panels will have higher resonance frequency and it's better not to use the panel around that area. Try to aim for a resonance freq at least one octave below crossover point. With a 12" woofer you want it to be well below 100hz, which requires a panel at least 15 or 20 cm wide.
Woofer baffling: This you want to maximize. Each doubling of the baffle size will give you 6dB more woofer output which is very welcome in dipole woofers. If ou don't want to increase speaker size you can fold it to the back creating an U-baffle, but an H baffle is even better. Check out www.linkwitzlab.com/woofer.htm
Power rating of the transformer:
A higher power rating basically means it's able to deliver more current into the panel, providing the amp can deliver. A too small transformer limits bandwidth.
Large transformers will also have less turns due to bigger core area. This a a Very Good Thing in an audio transformer as less turns equals lower leakage inductance and less internal capacitances> better high freq response. So if all else is equal a bigger transformer will show much better performance. With stepuptrannies it's always balancing on the limits of physics, this is a bad place to try to save a few $$. Go as big as you can affort. Looking at commercial esl-stepup transformers you'll see core sizes equivalent to 100-500VA power transformers for full range. 2 15VA's (=30VA) is not somehing I would consider for a panel that has to play down to 150 hz or so. Better go for the 50VA's, even better use 4 smaller ones(will double output voltage).
Crossover freq is what determines the whole design. Panel dimensions, stepup requirements all depend on it. You should start with choosing a crossover frequency. Have a close look at the woofer specs.
Few said:
We used a single Lambda woofer per channel in an "H" box. If you read on Linkwitz's site about dipole woofers, he makes it sound like the cones will be jumping around like Michael Flatley's nutsack, and I'd need huge amounts of xmax. I'm sure this would be the case with small woofers, but we had some fairly substantial units. We only tried a single driver per side with the idea of putting the woofer under the panel. The woofer cone hardly moved at all, we're talking like 1mm or so. And we were playing the panels quite loudly.
My friend's panels were about 14" wide by 48" high. My panels are 20" x48". It wasn't a huge difference in dynamics, but noticeable switching from one set of panels to another. We were using identical input transformers and power supplies.
I'm thinking of building another set of ESL's as well, something smaller maybe with wire stators. My 24" x 24" x 12" bass boxes under the speakers are going to be a problem where I want to put them. I'm also concerned with reducing the panel size and having to accept reduced dynamics
I built a small set of panels (the mini-mite) which were about 20" x 6" in size and they didn't sound particularly good at all. That strikes me as just too small for any ESL that will play down into the midbass. I was trying to pair it with a Jordan JX-92 in a TL cabinet. The Jordan sounds great up to about 5KHz, and my first reaction was to push the crossover up to 2-3KHz, but that as a nightmare to try to get crossed over nicely. The acoustic center of the panel is a long ways away from the center of the woofer, and they have radically different dispersion patterns. I could never get a seamless crossover point, and I tried beating on it with a steep active crossover too. I ended up removing the drivers and beating the cabinets apart with a mallet and tossing them out.
That experience reinforced my belief that large panels that can play low are the secret to good performing ESL's, and the lower you can cross over the panel the better you are. I'm a big fan of woofers under the panel and crossing over in the 130Hz region. My issue with that concept now is that I've got a great room to listen but it's a multi-purpose room that I don't want to fill up one end of. so I'm looking for a smaller solution. I'm now seriously considering a 2-way TL design with an active crossover and amplifiers for each driver in the enclosure.
Thanks, I love being right.
One trick I found when proto-typing my ESL's is to support them with small dots in the middle rather than a solid vertical support (dividing the panel into two sub-panels). See:
http://quadesl.com/speaker/diyesl/temp_frames.jpg
http://quadesl.com/speaker/diyesl/panel_measure.jpg
I needed the support to keep the diaphragm from collapsing (18" of unsupported length was too much for my 1/8" stator spacing). Using the dots, allowed my diaphram to be supported where it was needed, but my panel resonance was much lower than it would have been if I used a solid vertical support. Those panels have an active area of 18" x 46" and they have a resonance of about 35 Hz. I'm using 3.8 uM film.
I built a strip ESL (as I mentioned in other threads) as part of an experiment to try a segmented perf metal ESL. The narrow cavity had an insane resonant point in the midrange, and I couldn't never beat it down and have it sound good. I think I had two resonant problems, the first was the narrow width and the natural diaphragm resonance, and the second was a cavity resonance from the perf. Whatever it was, it was nasty and went in the dumpster. this again, reinforced my belief that big ESL's are the ticket to success.
I have a pair of Plitron ESL step-up transformers that are HUGE (and expensive). They are about 500 VA sized units. I've swapped them out against my innersound step-ups and with my 130 Hz crossover point, I can't notice any significant differences (after adjusting the damping resistor for each unit). They are so similar, that I don't use the expensive ones. I have run my ESL's full range, and they run out of steam in the bass. I'm not sure if it's amplifier, input transformer, or the diaphragm itself. It never sounded promising enough to make me investigate it further. But the point is that if you are building a full range ESL, you probably would need the big core of these ESL trannies. But from 130 Hz up, I certainly dont. The innersound trannies have about the core area of a ST-70 output transformer which is a 35 watt tube amp class transformer. Based on my limited experience, you don't want to build a full range ESL anyway, they get too big for what you get. Use a woofer, cross it low, and then you can use small step-up transformers.
If you are doing active crossover with your ESL, which you should IMHO. It frees up your design space a bit with respect to step-up ratios, crossover points and woofer spec's. With active XO, your pressure feedback EQ isn't subtractitive, and you can set the woofer output to match your panel efficiency, listening distance, and room characteristics.
Sheldon
Thanks, Sheldon, for the response. I'm starting to give myself a headache going back and forth with the design trade-offs. I'd really like to make smaller ESL panels than I now have, and I *need* to broaden the sweet spot. My panels are the same width as yours (20") but stand about 6' 6" tall. It's nice not having to worry about losing the highs while standing, so I'd like to maintain the height. The beaminess, though, is just nuts. I'm hoping that if I go with wire stators, narrow central tweeters, and an overall width of about 10-12", I'll gain more than I lose. I was planning to cross over to a vertical array of open baffle 8" woofers, and use a crossover frequency that is a bit higher than you're suggesting, but if I ever get the damn things built I may very well find that crossing lower works better. I just don't want to invest in over a dozen woofers and end up using them only to cover the range from 70 - 140Hz! (I'm planning to use a pair of sealed woofers for the bottom octave or two.)
Few
Few
Thanks for all the information.
About the bafle of the dipole's, the problem is that i don't want the speakers to become to big, to make a U bafle could be an option but to be honest is like a flat bafle, i think it makes the speaker look modern and less fat. I wan't to make an active crossover, so am i correct that i can compensate the loss of woofer output with the active crossover?
Than about the size of the esl, here's the same problem i don't want to make the speaker to big, i think 120 cm is the max height that i can put in my interior. So minus the woofer of 30 cm and the space around the woofer en and esl, the maximum height of the esl diagram becomes 70 cm.
If i understand you all correctly if i make the diagram widther the resonance freq becomes lower but also the spreading of the heigh tones becomes less. So what would be the best compromise, for resonance fq vs spreading?
@Maudio thanks fore the links to farnell, that's a nice price for that transformer.
About the bafle of the dipole's, the problem is that i don't want the speakers to become to big, to make a U bafle could be an option but to be honest is like a flat bafle, i think it makes the speaker look modern and less fat. I wan't to make an active crossover, so am i correct that i can compensate the loss of woofer output with the active crossover?
Than about the size of the esl, here's the same problem i don't want to make the speaker to big, i think 120 cm is the max height that i can put in my interior. So minus the woofer of 30 cm and the space around the woofer en and esl, the maximum height of the esl diagram becomes 70 cm.
If i understand you all correctly if i make the diagram widther the resonance freq becomes lower but also the spreading of the heigh tones becomes less. So what would be the best compromise, for resonance fq vs spreading?
@Maudio thanks fore the links to farnell, that's a nice price for that transformer.
Hi,
while You can play with the hight of the panel there is not so much room to play with the width. As my rule of thumb, I wouldn´t want to drive a 4" wide panel lower than 80-600Hz. I use my actual 8-9" wide panels just down to 300Hz. Since their diaphragm is pulled very taut (Fs~170Hz) I couldn´t go much lower anyway. I used to have panels of this width with Fs below 100Hz and though those played nicely, they never came close to the high-Fs panels with regard of dynamics and livelyness. I find it a misbelief that going ever lower by using less stretching force could lead to better ESL-sound. Using high tension and sizing up the width of the panel is imo the right way to go (besides that this can raise efficiency, lower transformation-factor and raise headroom and raise electrical safety!). For a >100Hz-panel think of how a ML Statement is built! If You want Your ESL to play dynamic like a horn You need size size size.
jauu
Calvin
while You can play with the hight of the panel there is not so much room to play with the width. As my rule of thumb, I wouldn´t want to drive a 4" wide panel lower than 80-600Hz. I use my actual 8-9" wide panels just down to 300Hz. Since their diaphragm is pulled very taut (Fs~170Hz) I couldn´t go much lower anyway. I used to have panels of this width with Fs below 100Hz and though those played nicely, they never came close to the high-Fs panels with regard of dynamics and livelyness. I find it a misbelief that going ever lower by using less stretching force could lead to better ESL-sound. Using high tension and sizing up the width of the panel is imo the right way to go (besides that this can raise efficiency, lower transformation-factor and raise headroom and raise electrical safety!). For a >100Hz-panel think of how a ML Statement is built! If You want Your ESL to play dynamic like a horn You need size size size.
jauu
Calvin
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