measuring the fountek ribbon driver impedance

[daly41k]

Hi amigos and friends, I have finished a line array speaker project using 12-5" fountex ribbon drivers per side (neo 2.0)
and 12-5" eaton mid-woofers per side. Meniscus audio in Grand Rapids helped me design a crossover using 24db per octave slopes and set at 2600hz. This is where we heard the best sound from both drivers. I have been happily listening to them for 8 months. Now I would like to biamp. The passive crossover is external in its own encloseure.

Here is my question, when biamping the ribbon drivers will have their own amp. I will protect them with a 20uf cap in series with the amp output to prevent any dc offset etc from getting to them.
I am using a DEQX 2.6p digital speaker calibration and room correcton pre amp. It has the ability to set the new biamp crossover to 96db per octave (more if I want) at 2600hz. The Deqx crossover will feed the amp.

However when I measured the resistance of the tweeter array I get .7ohms. I do not have an impedance meter. The tweeters were done in a series parallel arrangement so that I could get 6ohms impedance (it had to be graphed by frequency at the input of the crossover). These tweeters have impedance matching transformers and I cannot figure out why in a static condition I am reading a direct short (the crossover is disconnected). I am worried that my amp would complain about a low impedance connection when there is no passive crossover inbetween.

Has anyone ever used the fountek ribbon in a biamp design and what did you do for impedance matching. thanks a bunch. I am ususally on the Pass site but this is the better forum for this question. dave

[ABJensen]

Your measuring the primary vinding of the transformer. You can not measure it whit DC.

Andre´

[sreten]

Hi,

The capacitor is not really needed with transformers in the way.

/sreten.

[daly41k]

Hi-thanks guys, I went back to the manufacturers literature and Fountek claims a DCR of .2 ohms pre unit with an impedance of 7ohms. I also remember where I put the measured impedance curve and tonight I will check it out but with all the series parallel connections I hope things work out. I will keep in touch. dave

[tinitus]

It says everywhere.....never run a ribbon without a series kondensator

The slightest malfunktion and you can blow up a small fortune

But kondensator will ofcourse influence slopes of your digital crossover... and phase

If I am not mistaken everybody says that ribbons are at their best with low order filters - I think with that many ribbons you should not have any problems

Digital crossover might be ok on bass/mid - but wont it kill the magic of a ribbon

Maybe I would cross a bit higher pure passive on ribbons - use a normal preamp and only have Eq on amp to bass/mids

[sreten]

Originally posted by tinitus


It says everywhere.....never run a ribbon without a series kondensator

The slightest malfunktion and you can blow up a small fortune

Hi, does not apply for transformer coupled, it can't pass DC either, /sreten.

[daly41k]

Hi everyone, I am actually very happy with the passive crossover using the DEQX 2.6p with the speakers and room corrected.

I was just going to expierment a bit but I want to make sure that I can do it safely. I have an outboard crossover encloseure and yes I can passively run the ribbons and actively run the bass mids.

Line arrays have an issue with so many drivers and that you must locate thier centers as closely as possible and cross them over steeply to avoid lobbing affects. I don't notice any lobbing affects when I sit as normal in the far field. I think with a digital steep crossover I can improve the dispersion of the mid/woofer and its distortion (with 12 drivers that is minimal anyway) on the high pass side as 2600hz is close to the 3000 hz (high side) speck of the eatons. The eatons roll off from 60-80 hz depending on the cabinet. dave

[tinitus]

Well, Sreten you are as always most convincing ..... cant pass DC .....and ofcourse you are right

But imagine the scenario where a ground connection fails at the end of chain ... fore some reason.....it seldom happens, but it does occationally..... what will happen then

[v-bro]

I suppose the filter includes circuitry for the Etons? Can't you split the passive filter?

I drooled over some pictures of Fountek ribbons myself lately, how are they? I was hoping they could be implemented in a less complex way, I suppose a two way (not line array) could do for my small room?

[cocolino]

Hi, does not apply for transformer coupled, it can't pass DC either, /sreten

Although a transformer can`t pass DC, IMO a cap before a transformer coupled "true" ribbon tweeter is not a bad idea though.
It`s not so uncommon that audio gear sometimes produce some very low-frequency noise when switching on or off. This can push (pull) a ribbon diaphragm way out of the air gap and overstretch it.