could you make a transformerless short ribbon work with a series Xover - diyAudio
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Old 10th March 2006, 09:15 AM   #1
Puggie is offline Puggie  United Kingdom
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Default could you make a transformerless short ribbon work with a series Xover

Ok, sorry about the long title and lack of pictures.

I'm looking at building a pair of short ribbon tweets, one set will be 1" long super tweets to go with some wide range horns that lack a little from about 15kHz up (I'm thinking along the lines of the townshend Maximum audio supertweets), and the other pair will be more conventional 3" ribbon tweets.

I was thinking could you run a ribbon without a transformer in a variant of a series Xover?

sorry no pics but I'll try and explain

ribbon in series with the midbass driver, the total impedance is about the same as the midbass driver (4ohm) then put an inductor in parallel with the ribbon and a cap between the top of the ribbon and the inductor so the inductor is now in parallel with the cap/ribbon comination.

the amp would see the impedance of the midbass, the ribbon would have the bass blocked by the cap and the inductor would take these low frequencies to the midbass. The whole unit will have about the same impedance as the midbass driver so no prob for the amp, and the ribbon will be free of any transformer.

would this work, am I oversimplifying things?
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Old 11th March 2006, 01:50 AM   #2
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Hi Puggie,

Most ribbons are very delicate and will stretch or tear if driven with low frequency power. For this reason, a steep 4th to 8th order crossover is frequently used. A high order passive network will have several inductors which can be wound with thin high resistance wire to help create an amplifier safe impedance. You will probably need a simulation program, or at least SPICE, to design this lossy network.
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Old 13th March 2006, 12:07 PM   #3
Puggie is offline Puggie  United Kingdom
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4th or 8th order!!!

I was thinking 2nd or 3rd order (electrical) slopes. But it is acceptable to use low dia wire to increase resistance and not use a transformer for ribbon tweets.
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Old 13th March 2006, 12:21 PM   #4
tinitus is offline tinitus  Europe
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above 10khz it should be possible to use a series resistor of 2 - 3 ohm - a Vifa or ScSp "ringradiator" is about 3 ohm

At very high crossover frequency it should be sufficient with low order slopes

I am working on something similar

But you have to consider how efficient you want it to be - a series resistor will take away some of it - but actually I think you dont need very high efficiency at these high frequencies

Your ideas about using a series crossover are interesting, but a 3-way series crossover - I wouldnt, and I wouldnt even consider a 3-way

Make your 3" ribbon about 1/2" wide - will do the trick alone
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Old 2nd July 2013, 10:45 AM   #5
Rewind is offline Rewind  Sweden
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I might be living on the edge here but I use a 0.5ohm DIY Duelund resistor and it works great. I cross at 7kHz with minidsp with 12-24dB slope. Take cover!

Last edited by Rewind; 2nd July 2013 at 11:10 AM.
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Old 2nd July 2013, 05:24 PM   #6
john65b is offline john65b  United States
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Hmmm, try it out and let us know. This is an interesting concept for a series xover.

But isn't a simple series xover like you detail a 1st order, and thus not very steep?

I guess if you make the cap selection correctly (high enough) it wouldn't matter?
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Old 2nd July 2013, 05:39 PM   #7
Rewind is offline Rewind  Sweden
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The midrange would act as a 4 ohm resistor. I tried with a DIY 4 ohm Duelund resistor and it was hard to get any sound out of it. I had to use a 0.5ohm. The amp didn't like 0 ohm for some reason. :P

The midrange need to be something like a pure resistive load, like an AMT, because cone drivers vary a lot. I just measured my Beyma TPL-150 with a simple multimeter while playing music and it hold steady at 5.3 ohm. The TPL-150 is 98 db sensitive. Mundorf 2340 has a 90dB sensitivity and is 3.9 ohm, which is the same sensitivity as a typical true ribbon driver, but that is with the ribbon driver transformer. I don't know how sensitive it is with a 0.5 ohm DIY Duelund resistor but it is low. Like 85-88dB. If I were to use a 4 ohm resistor, then I would get only whispers. Get a minidsp instead.

It was a good idea!

Last edited by Rewind; 2nd July 2013 at 05:43 PM.
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