# Thirlmere Bipole using the CSS EL70



## StereoClarity (Apr 22, 2008)

As I’m sure most of you know, Bob and Mark have a new driver called the EL70. A very special driver indeed. It’s a paper cone driver that shares the same basket as the CHR-70. Anyways, Bob was so kind as to give me 4 of these for testing so I he could get some initial opinions on the drivers in an actual application. Needless to say, I was excited to try some new toys and build something interesting.

Out of the box, the drivers appear to be very well built, as can be expected from both Mark Audio and CSS products. I was happy to find that the drivers came with mounting hardware since the basket design has a very small countersink for bolts. The supplied foam gasket was also a nice touch.

Scott and Dave have been working on a multitude of designs for this new driver and I was like a kid in a candy shop. I had 4 drivers total and was anxious to get started. I wanted an 8ohm final load and hadn’t built a bipole before so I decided on the Thirlmere design. 

The build was fairly easy and went along without incident. After some primer and a few coats of paint these cabinets were looking sharp! (pictures to follow)

Unfortunately, I didn’t have time to break in these drivers before listening to them. The first time I turned them on I honestly wasn’t too pleased with the performance. The sound was vague like I was listening to speakers on the other side of a thin towel. They sounded a bit flat on the top end and the image was very blurry. Most notably, these things had an 18db spike at 300hz! First time I heard it I about fell off the bed. 

All that changed when I made the needed changes. The first change that I made was to pull them away from the wall. Bob told me that a bipole needs to be about 3 or more feet from the rear wall to function properly. After I did this the image was dead center and placement was very clear. After I generously stuffed the cabinets the 300hz peak was tamed a bit but just a small bit of the peak remained. I think if I stuffed the cabinet a little more the peak would all but disappear. Dave has suggested a few different options for the driver placement that should take care of the inherent 300hz happy spot 

Driver break in was also something that improved the sound and just took time. The top end is still a little lacking in my opinion but a touch of EQ or a super tweeter would yield outstanding results. After a while I found myself bringing the EQ closer and closer to flat. These speakers have a very live sound about them that is hard to explain. I think it’s the fact that they are bipoles but I’m not sure since they are the first pair that I own. After some thought, I imagined each instrument in my room and the sounds they would make. Each sound emanating from a live sound travels in every direction (like the rear wall) and not just at the listener. I think this might be why I think these sound so natural. 

These drivers need a bit of break in time as I've stated above. Give them a few hours of play time before making any final judgments. I think you'll find that the sound develops quite a bit. Overall, I'm pretty impressed with these drivers and they get my approval! 


Pictures below.....


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## Sonnie (Apr 11, 2006)

Is the cabinet design based on the Thirlmere design? I am not familiar with it. I have never seen an angled port like that... or is it a transmission line?

What does the inside of the cabinet look like?

I wonder what might happen if you placed a super tweeter in the top facing up.

Nice work... :T


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## Mike P. (Apr 6, 2007)

The dual horns in the background, are they a BVR design?


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## StereoClarity (Apr 22, 2008)

Mike P. said:


> The dual horns in the background, are they a BVR design?


Yes indeed.....and they are marvelous. I'll be building another pair before too long since I'm always building. I hope my energy doesn't fail me when I get older. I love this stuff too much!


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## StereoClarity (Apr 22, 2008)

Sonnie said:


> Is the cabinet design based on the Thirlmere design? I am not familiar with it. I have never seen an angled port like that... or is it a transmission line?
> 
> What does the inside of the cabinet look like?
> 
> ...


Thanks Sonnie! There are a few different variations of the Thirlmere design that Dave and Scott developed. This is just one of them. Check out more of their designs at www.Frugal-Horn.com


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## Creative Sound (Mar 29, 2007)

Hi,

Thirlmere is one of what Scott and Dave have called the Lake District designs.

Lake District Maps

Bob


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## StereoClarity (Apr 22, 2008)

Recently I've been experimenting with these in my room with some fantastic results. These have been breaking in beautifully. I've tried moving them around the room and they have really surprised me. 

I put about 10feet between these (with about 3.5feet from the walls) and the imaging is incredible. That's not the best part though. I feel like when I spaced these apart the perceived image size also got much larger! The best way I can explain it is by using a TV comparison. You have a 1080p screen that's 20". It's ultra sharp and clear but it's still a small screen. Then, you switch to a 1080p 60" screen and you still have that clarity and detail but it's much more engaging and enveloping. The image before was a little cramped and squished like it was scaled down. Now it's life size. 

I'm starting to enjoy these


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