ESL57, banishing the sweet spot

[Firebottle]

Something I have thought about for a long time, adding a wide dispersion tweeter to the ESL57.
The sweet spot really is narrow for the top registers, so if you are not sat in the sweet spot the treble can seem a fair bit down in level.

So I've finally got around to it and sourced some HiVi RT1C-A Planar Isodynamic tweeters. They are 5 ohms so I have padded them out to 8 ohms, the drop in efficiency is welcome as the tweeters are well in excess of the '57s sensitivity. They are installed on top of the '57s as shown:

http://i63.tinypic.com/spej9k.jpg

I've ordered some variable L pads to control the level which haven't arrived yet, so the sound is a tad bright (understatement) :eek:

I crossed them in at about 5KHz, they augment the '57s treble rather than replacing it.

http://i64.tinypic.com/24vso7c.jpg

Has it banished the sweet spot? Totally annihilated it :thumbsup:

[walpurgis]

Ah. Nice one Alan! :)

[Light Dependant Resistor]

I have never had an issue with dispersion from ESL57, there is no sweet spot, just
equal wide gorgeous stereo sound.

[User211]

I remember a pair at Scalford with a ribbon tweeter on top. Not sure what frequency it cut in at, but that was just bizarre. As you walked between the speakers you'd move in and out of multiple HF hotspots.

Put it this way Alan, they sounded far less even than your pair did at the Midlands do as you moved around.

[Arkless Electronics]

They do indeed have a very narrow sweet spot... Nothing else comes close in my experience. I can't see this not causing colouration etc though personally... When in the sweet spot you will be hearing the full correct amount of treble from the ESL's plus the treble from the tweeter I would have thought...

[Firebottle]

Your thinking is of course right Jez, however when not in the sweet spot I think the compromise is a better one.

I've always wanted a little extra treble from the stats anyway, now I have the L pads fitted I can dial it in to whatever level I want :)

[Arkless Electronics]

Your thinking is of course right Jez, however when not in the sweet spot I think the compromise is a better one.

I've always wanted a little extra treble from the stats anyway, now I have the L pads fitted I can dial it in to whatever level I want :)

Fairy snuff... I'd put an on-off switch in as well though!

[Firebottle]

The L pads go from zero to max (straight through) so no problem.

I have been turning the level down as I have been listening to get a good compromise.

[walpurgis]

How are you finding the treble quality with the HiVi units Alan? It should be good.

[Firebottle]

Excellent actually Geoff, I'm glad I chose them.

[wee tee cee]

Brian gave me a try of his supertweeters had a wee play about positioning wise. firing vertically velcroed to the 57s they seem to do the business.

he never got them back-57s are singing....

[Firebottle]

Excellent Tony :D

[bumpy]

The L pads go from zero to max (straight through) so no problem.

I have been turning the level down as I have been listening to get a good compromise.

Which ones did you use?

[wee tee cee]

batpure i think. Brian housed them in a wee wooden box.
They come from japan and were about 50 quid but Brian got stung for import duty this time round to replace my ones so mid 60s.

[Firebottle]

Which ones did you use?

https://www.ebay.co.uk/itm/Monacor-Speaker-L-Pad-LP-100-8/132400947495?hash=item1ed3b62127:g:1osAAOSwiYlaDRa g

Note that these are 8 ohm so some resistive padding may be required if the tweeter used isn't 8 ohms, as in my case. :)

[bumpy]

https://www.ebay.co.uk/itm/Monacor-Speaker-L-Pad-LP-100-8/132400947495?hash=item1ed3b62127:g:1osAAOSwiYlaDRa g

Note that these are 8 ohm so some resistive padding may be required if the tweeter used isn't 8 ohms, as in my case. :)

Thanks

Is there some trick whereby you can adjust it to give the right level for the driver, then take some measurement of the volume control and replace it with two quality resistors. You can probably tell I am no expert at electronics.

[sq225917]

Misterdog (PFM) had a set of small ribbons on his, he's recently swapped them for a set of ADAM's AMT ribbons. Both had the effect of lifting the height of the speakers. Call it a broader sweetspot, more diffuse, less focussed. I doubt it's more accurate in terms of lobing, defraction, timing etc, just an easier listen in terms of accommodation.

[bumpy]

Anyone??

"Is there some trick whereby you can adjust the L Pad volume control to give the right level for the driver, then take some measurement of the volume control and replace it with two quality resistors. You can probably tell I am no expert at electronics."

[Firebottle]

This shows how to calculate for an entered value of required attenuation

http://www.sengpielaudio.com/calculator-Lpad.htm

With a constant impedance L pad 'volume control' it is impossible to measure the resistance to ascertain the attenuation, as the impedance is designed to stay constant.

[bumpy]

Thanks Alan

Looks like a case of laying in a few cheap resistors to experiment with. :)