I’ve always had a love/hate relationship with ribbon tweeters. Mostly hate TBH.

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Of the few I’ve owned over the years, I've either sold them or sent them back. The Raal, Fountek and LCY are just a few of the brands I've owned.

The same goes for the ESS Heils, AMT (Beyma call them TPL) or planar tweeters in general.

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Pros:

• Great step response. (from extremely low mass of a ribbon compared to a 1" dome for example).

• Reach higher frequencies than other technologies, with the exception of AMT that doesn't always reach super high.

• Sensitivity is usually good… though not great. (planar are usually on the lower efficiency side but RAAL ribbon are high).

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Cons: 

• Unfortunately, ribbons all beam like crazy, meaning you have a very annoying, super tiny sweet spot.

• Exhibit higher distortion than most other tweeters when higher SPL is required.

• Are a royal pain to integrate with a cone mid-ranges as the sound signature and dispersion doesn't match very well to a heavy 6.5" mid-range as an example. I often laugh when proud owner say they "blend" seamlessly to their 6" woofer... what a joke.

• Often need to be crossed higher than specifications recommend, to obtain acceptable distortion results.

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I purchased the RAAL 70-10, to use as super tweeter on my ESL speaker. I was using a first order crossover, and the 70-10 kicked in at 11 kHz. It worked well and matched the ESL sound signature.

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The 70-10 addition added some much-needed "air" to the overall sound as most ESL speaker can't reach ultra high frequency.

A pair of super tweeters should ideally come as stock with every ESL speaker , as all badly lack high frequency extension BTW.

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I ended up selling my ESL’s. I like to listen louder than what any ESL could ever do. Even with a high pass and dedicated sub-woofer, they were constantly clipping. ESL are great till you try to listen louder, they then collapse in front of you, what a failed technology...

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After selling my last pair of ESL (I've owned 3 pair so far and likely never will own ESL again), I was stuck with the 70-10 and tried to "recycle them" as tweeter for DIY speaker projects. It never worked great and 100% of the time, a regular dome tweeter would work better.

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I eventually smartened up and sold the RAAL.

I only see the 70-10 as a match and intelligent use for augmenting ESL speakers capability, or perhaps matching them with several planar mid-range. (Never tried that 2nd option but it makes sense and could work).

Anything else will fail, miserably.

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Below is a 3" distance measurement, with the microphone placed in the middle of the RAAL 70-10

Foam pads were present and placed to provide maximum opening (pads being farthest apart).

• I was then using my USB microphone (MiniDSP Umik 1), sadly, this mic doesn't have the sampling resolution to record above 20kHz so I can't show the extension...

• clever google research would yield higher resolution measurement of some Raal tweeters.

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Unfortunately, I don’t have a picture of the set-up as the 70-10 were long sold before I published this.

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