Where to cross in a supertweeter with 2 WR125ST's?

[Brisso57]

I have a pair of Foster E100T10 ribbon tweeters, and I'm considering using them as supertweeters with a pair of CSS WR125ST's (placed one above & against the other).

I have two cabinets, each of approx 48 litres volume (which I can decrease by simply adding bags of sand). They can be sealed or vented, as I can modify the baffle.

The Fosters run from approx 6kHz to 40kHz. Approx 92dB.
Here is the data: www.allenorgan.com/forsale/fosterWithOutFacePlate.pdf

Here is the data for the WR125ST's:
http://homepage.mac.com/tlinespeakers/FAL/downloads/CSS-FR-WR125-datasheet.pdf
86dB, but I believe running 2 in parallel with give a 6dB lift, making them net 92dB at 7 ohms?

OK.
Now I want to run the WR's full-range, and to blend in the ribbons just as the WR's fall away.

What freq should I cross over? (9500? 12000?)
What slope? Would 18dB be enough?

Thanks

Doug

 

[Cal Weldon]

If you have some caps laying around try a 1.5 or 1.0 mfd. May not need anything else unless you're concerned about the beaming of the WR's that seems to start about 5K. Oh and you'll only get 3 more dB for the same amount of power fed to the WR's so you might also have to add a little padding to the tweeter.

 

[audiobomber]

You're going to have a lot of comb filtering with a pair of WR's running that high, due to long center-to-center distances between drivers.

You should consider a 2.5-way TMM instead, which will give you baffle step compensation, allowing you to move the speakers out from the walls for best soundstaging.

 

[Brisso57]

Details of TMM 2.5

You're going to have a lot of comb filtering with a pair of WR's running that high, due to long center-to-center distances between drivers.

You should consider a 2.5-way TMM instead, which will give you baffle step compensation, allowing you to move the speakers out from the walls for best soundstaging.

2.5?
Do you mean running the upper WR full range, with the lower one cutting out at, say, 4000Hz?

Doug

 

[audiobomber]

Re: Details of TMM 2.5

2.5?
Do you mean running the upper WR full range, with the lower one cutting out at, say, 4000Hz?

Doug

No, the lower woofer would cut out at the baffle step frequency (more like 400 Hz) and the upper woofer would run up to the tweeter crossover. The upper woofer-to-tweeter cross would be conventional, as in a two-way.

 

[Cal Weldon]

I tried this but too much combing and beaming. even when I hung a big 'ol coil on the bottom unit, I was not happy.

 

[Cal Weldon]

So I ended up doing this. Much better. No combing, no need for BSC. Both WR's running full and a small cap on the tweet.

 

[Brisso57]

So I ended up doing this. Much better. No combing, no need for BSC. Both WR's running full and a small cap on the tweet.

Thanks Cal. I recognize the cabinets. 🙂

Doug

 

[planet10]

I recognize the cabinets.

The mutation of the Spawns that started the entire Chang dynasty.

dave

 

[audiobomber]

So I ended up doing this. Much better. No combing, no need for BSC. Both WR's running full and a small cap on the tweet.

Interesting idea. Maybe easier to place than bipoles?

 

[Brisso57]

General query re side placement of second driver

So I ended up doing this. Much better. No combing, no need for BSC. Both WR's running full and a small cap on the tweet.

Looking at the drawing of the Calhoun on the P-10 site, I see that the side driver is located at about 750mm from the floor.

As long as it wasn't TOO close to the top of the cabinet, could this be generally applied to using two WR125ST's retrofitted to a donor speakerbox? (A frankenspeaker, if you will.) Would the same avoidance of BSC apply?

Doug

 

[Cal Weldon]

Re: General query re side placement of second driver

Looking at the drawing of the Calhoun on the P-10 site, I see that the side driver is located at about 750mm from the floor.

889mm on mine.

As long as it wasn't TOO close to the top of the cabinet, could this be generally applied to using two WR125ST's retrofitted to a donor speakerbox? (A frankenspeaker, if you will.) Would the same avoidance of BSC apply?[/B]

The BSC is avoided by side firing the driver. The other option is to run it as a 2.5 way if you want them both front firing, but that's what I had to begin with and was not fully happy.

 

[audiobomber]

Re: Re: General query re side placement of second driver

The BSC is avoided by side firing the driver. The other option is to run it as a 2.5 way if you want them both front firing, but that's what I had to begin with and was not fully happy.

Third option would be mount one on the rear, creating a bipole. There's lots of info on this site and at Planet10's site. http://www.planet10-hifi.com/boxes-CSS.html

 

[Cal Weldon]

Hi Dan,

Yes, that is a good third option. Not possible on the Calhoun unfortunately.

 

[Brisso57]

Re: Re: Re: General query re side placement of second driver

Third option would be mount one on the rear, creating a bipole. There's lots of info on this site and at Planet10's site. http://www.planet10-hifi.com/boxes-CSS.html

Rear firing will mean the boxes will need to be placed further away from the walls, and it's here that the dreaded WAF intrudes on the physics of the matter! :-(

In my case - with the donor boxes I want to use having non-vertical sides - rear firing could be achieved more practically.

A fourth option I investigated would be to internally partition the box and then use the lower chamber for a small subwoofer of appropriate Vas and Fo (crossing over at ~200Hz), thereby eliminating the need for two WR's.

Hmmm

Doug

 

[Brisso57]

Re: Re: Re: Re: General query re side placement of second driver

A fourth option I investigated would be to internally partition the box and then use the lower chamber for a small subwoofer of appropriate Vas and Fo (crossing over at ~200Hz), thereby eliminating the need for two WR's.

Hmmm

Doug

Here is the (sub)woofer that I'm considering:

www.jaycar.com.au/productView.asp?I...&pageNumber=&priceMin=&priceMax=&SUBCATID=383

The sensitivity is a good match for the WR / FR speaker.

The JAYCAR catalog also goes on to recommend a vented cabinet volume of 26 L, and a vent of 50mm ID and 133mm length, giving a tuned freq of 37Hz and a -3dB freq of 35Hz.

Donor cabinet volume is approx 48L, so 26L for the sub leaves 22L (minus braces, etc) for the WR / FR.

Seems like a feasible match.

Doug