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Simonon

Best crossover frequency for ribbon super tweeter

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I am building myself a couple of super tweeters after being given a couple of Fountek Ribbons. Luckily I have most of the parts required to build myself something that looks nice but am unsure of the crossover frequency that I want these to cover so I thought I would ask on this forum based on the experience of others. Not much happens with my vintage tube amps past 16k where the roll off is significant ( cant hear past 15k anyway with my 50 year old ears).

My choices are 7K, 9K or 14K and thinking of a simple second order crossover with some series resistors for attenuation if they prove too efficient ( 96dB efficiency from the datasheet). Would second or third order crossover be best? as the calculated inductors and foil capacitors are cheap from WES components.

Hoping to get a little bit more upper detail which is where my vintage speakers fall short compared to modern designs and the fact that this venture will cost me very little,  I thought why not give it a try. A little experiment that may work or bring about disappointment but satisfies my need to fiddle.

 

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1 hour ago, Simonon said:

I am building myself a couple of super tweeters after being given a couple of Fountek Ribbons. Luckily I have most of the parts required to build myself something that looks nice but am unsure of the crossover frequency that I want these to cover so I thought I would ask on this forum based on the experience of others. Not much happens with my vintage tube amps past 16k where the roll off is significant ( cant hear past 15k anyway with my 50 year old ears).

 

If the o/p transformers on your tube amps don't deliver much past 16kHz ... then adding supertweeters ain't like to do much.  🙁

 

1 hour ago, Simonon said:

My choices are 7K, 9K or 14K and thinking of a simple second order crossover with some series resistors for attenuation if they prove too efficient ( 96dB efficiency from the datasheet). Would second or third order crossover be best? as the calculated inductors and foil capacitors are cheap from WES components.

 

With 2nd order, I would choose 9kHz (given your amp).

 

1 hour ago, Simonon said:

Hoping to get a little bit more upper detail which is where my vintage speakers fall short compared to modern designs and the fact that this venture will cost me very little,  I thought why not give it a try. A little experiment that may work or bring about disappointment but satisfies my need to fiddle.

 

To give you more clue about what to do ... maybe you should borrow a mate's non-tube amp and see if that delivers more HF with your speakers?  Then you can decide whether you need to add a supertweeter to your current setup ... or replace your amp.  🙂

 

Andy

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Hi Andy

The amps are built into the back of the speakers so replacing is not an option. I think you are right with the 9khz 2nd order crossover as this was my thought also.  I doubt these tube amps pass much beyond 15k if anything as they date from 1964. I am very curious into what these ribbons will achieve.

I am about to give the amps a birthday with some 5% metal film resistors and some nice foil capacitors. Measured heaps of drift with the old carbons.

The ribbon exercise will cost me about 40 dollars with some inductors and caps for the crossover. If I don't like the result nothing is lost.

DSC02004.JPG

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On 10/07/2018 at 8:40 PM, Simonon said:

I am building myself a couple of super tweeters after being given a couple of Fountek Ribbons. Luckily I have most of the parts required to build myself something that looks nice but am unsure of the crossover frequency that I want these to cover so I thought I would ask on this forum based on the experience of others. Not much happens with my vintage tube amps past 16k where the roll off is significant ( cant hear past 15k anyway with my 50 year old ears).

My choices are 7K, 9K or 14K and thinking of a simple second order crossover with some series resistors for attenuation if they prove too efficient ( 96dB efficiency from the datasheet). Would second or third order crossover be best? as the calculated inductors and foil capacitors are cheap from WES components.

 

 

Good luck with that. 

 

Crossing over above 6kHz isn't easy to do without creating combing effects, due to the distance as a fraction of wavelength between the drive units, even with 4th order filters.  It means that the optimum listening height will be reduced to a very small slice of space.   

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5 hours ago, Art Vandelay said:

Good luck with that. 

 

Crossing over above 6kHz isn't easy to do without creating combing effects, due to the distance as a fraction of wavelength between the drive units, even with 4th order filters.  It means that the optimum listening height will be reduced to a very small slice of space.   

 

With the 1.7, Magnepan bring the 'supertweeter' in at about 10kHz - simple 6dB slope with a cap.  The supertweeter is close to the mid/tweeter, though - it's the last few lines of wire on the mylar out of about a dozen or so.

 

They don't roll off the mid/tweeter, though, to match.

 

Andy

 

Edited by andyr

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1 hour ago, andyr said:

They don't roll off the mid/tweeter, though, to match.

At these frequencies the summed response is so very spatially dependant it's unlikely to even make a significant difference.

 

 

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15 minutes ago, davewantsmoore said:

At these frequencies the summed response is so very spatially dependant it's unlikely to even make a significant difference.

 

You may well be correct, Dave (it's beyond my techernical knowledge).

 

I posted simply to suggest to Art that mfrs have been able to bring in supertweeters successfully.

 

Andy

 

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Hi Simon - nice tweak! Good luck; hope you get the results you want. Those beautiful old speakers sound very fine already. :)
 
If anything this little project satisfies my need to fiddle and excuse to spend time in my workshop. My wife is happy because it is costing nothing
I will be interested in the results as the 1950s designed Wharfedale Super 3 tweeters are not really tweeters in the modern sense. Past 12k the roll off is significant so these ribbons should achieve something I would expect. Not sure about phase yet but Im gonna find out shortly when the caps and inductors arrive for the 2nd order 9k crossover. If not I have learned something from the exercise. A frequency sweep of the old type 3 amps also showed up an issue on the left channel which I suspect is some out of tolerance carbon resistors which I have some 5w metal film replacements.
Hopefully I can get Christos over with his expensive mic and audio analysis software to see what happens when I hook them up.

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2 hours ago, andyr said:

 

You may well be correct, Dave (it's beyond my techernical knowledge).

 

I posted simply to suggest to Art that mfrs have been able to bring in supertweeters successfully.

 

Andy

 

OK, my bad, I wasn't aware that the speaker in question was a quasi ribbon.

 

I have seen / heard super tweeter implementations that worked quite well with large ribbons that tend to beam at the top of the passband.   

The best approach is often to misalign the axis of the super tweeter so that it's beaming >45 degrees from the axis of the speaker panel.  

This can mean beaming the super tweeter directly at the listener and removing / adjusting the toe-in of the main panels to create the desired  acoustic roll-off at the listening position - to blend with the tweeter output- including the first order filter response.  

 

Of course best to scope it out first with a decent measurement mic and fft-an software.  

 

Cheers,

Art

 

 

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@Art Vandelay

 

its been a while. Are you still running those B & W 802 is it?  Or have you moved on?

 

i can see you’re playing with the ME but what digital Front end have are you using?

 

Aplogies to the OP for going off topic.

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What a surprise these ribbons are on my vintage system. I am still waiting for the caps and indictors for my 9k 2nd order crossover but thought I would give them a go with a 3uf cap to give 10.6 khz 1 st order. Early indications without any measurements are impressive.08543393875ba56c80f046d459d472c7.jpg

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6 minutes ago, Zaphod Beeblebrox said:

@Simonon   Mmmmm. I spotted a couple of AVOs in the background.

 

AVO?  (Apprehended Violence Order??)

 

Andy

 

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AVO meters, old things with precision indicator arms.

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1 hour ago, andyr said:

 

AVO?  (Apprehended Violence Order??)

 

Andy

 

AVO (Amps, Volts, Ohms). The first multimeter. They ceased making them sometime in 2008, because meter movements were getting very expensive. I have one of the last ones ever made (a MK 7) and one of the earlier ones (ca. 1960s).

 

https://www.google.com/search?q=avo+meter+images&client=firefox-b&tbm=isch&tbo=u&source=univ&sa=X&ved=2ahUKEwiPzrSfwKDcAhVLEpQKHeaHBGAQsAR6BAgGEAE&biw=1259&bih=937

 

https://en.wikipedia.org/wiki/Avometer

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10 minutes ago, Zaphod Beeblebrox said:

AVO (Amps, Volts, Ohms). The first multimeter. They ceased making them sometime in 2008, because meter movements were getting very expensive. I have one of the last ones ever made (a MK 7) and one of the earlier ones (ca. 1960s).

 

https://www.google.com/search?q=avo+meter+images&client=firefox-b&tbm=isch&tbo=u&source=univ&sa=X&ved=2ahUKEwiPzrSfwKDcAhVLEpQKHeaHBGAQsAR6BAgGEAE&biw=1259&bih=937

 

https://en.wikipedia.org/wiki/Avometer

Now you’re showing your age....:P

 

when i I was a kid,  under 10, I scrapped enough money and waited till the local Tandy electronics store had a special on those kit AVO and it served me until I ended up in TAFE.    Great meter it was and I looooved the scales and range and the reflective curved mirror on the scales.   Keep it Trevor,  beautiful meters with super scale!

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Love my old test gear. Nixie stuff is even betterfc2f9708ae999bae149271b67a737a29.jpg

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For those reminiscing over old avo meters here is my mk3. Found unused in its original box with leads and manual.8b6f5ddef7d892fca839ce8fadc6506d.jpg

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I get a lot of enjoyment from usin old test gear when restoring vintage electronics using a digital meter doesnt feel right09b61fdeb5ca51c4619f42b462df9223.jpgad6dd3bb802e7cdc5f2db4e0134373f3.jpgd84a1643f5fb0630337400be504da1f5.jpg

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50 minutes ago, Simonon said:

For those reminiscing over old avo meters here is my mk3. Found unused in its original box with leads and manual.8b6f5ddef7d892fca839ce8fadc6506d.jpg

Wow! Nice.It sure is in spectacular condition. Whatever you do, don't look on eBay. AVOs sell WAY under their original price. I'm on the hunt for a Triplett:

 

https://www.google.com/search?q=triplett+630&client=firefox-b&tbm=isch&tbo=u&source=univ&sa=X&ved=2ahUKEwjboPKx4aDcAhWUCqYKHRK-BeYQsAR6BAgCEAE&biw=1259&bih=937

 

Construction quality on later models leaves the AVO for dead.

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7 minutes ago, Simonon said:

I get a lot of enjoyment from usin old test gear when restoring vintage electronics using a digital meter doesnt feel right09b61fdeb5ca51c4619f42b462df9223.jpg

Indeed! something reassuring re a point to point needle ha!-- the Digital Ones are useful though for load settings on MC phono Stages :)

 

Willco

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