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Old 19th June 2008, 02:47 AM   #1
pjpoes is offline pjpoes  United States
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Default Scan-Speak 3-way design (Ekta Grande modified)

I've been wanting to build the Ekta Grande that Troels Graveson designed. However, the cost, cabinet complexity, and fact that it doesn't match my other speakers had deterred me from this. I was in the process of building a set of towers using some focal drivers I had, but after a Lightening storm took out my speakers, an amplifier, and two tv's, I decided that maybe its time to build that Ekta I wanted to build. Then I saw Zaph's 2.5 way ZRT design, and started thinking more seriously about this. Zaph is using the great Aircirc tweeter with the same two midbass drivers, but no midrange. In fact, in the end, I may just build this nice design as is, and not worry about the more complex 3 or 3.5 way (Which I'm proposing). Troels and a few others who listened to a design somewhat similar to the ZRT, but with a somewhat higher crossover point, felt the 18W drivers didn't give a very accurate midrange, and felt that adding a midrange greatly improved things. I believe Zaph has circumvented this issue with the low 1.6khz crossover point, but then, it has to be at the expense of lower output and higher distortion. The problem I have with the Ekta is that the woofers are simply run in parallel, and I think this will not be best, I think using a baffle step inductor on the second woofer, making for a 3.5 way design is a better idea. My plan is to use externally mounted crossovers, so that I can activly cross these over in the future, or at least play with the idea, but for now I plan on building the crossovers as a passive design, and use a C-core toroirodal inductor for the second woofer, in order to keep the high value with a low enough ESR. I'm wondering what you all think of this modified crossover design. It's quite a bit different from the original Ekta's in values, and its possible that the original values will be better, and that mine are off as a result of not having actual measurements yet, but I can't get the drivers to measure until I straighten some things out first.

I'm also kind of thinking that no inductor on the second woofer simplifies things and might work find, in which case it would remain a normal 3 way, but would have some modifications to the crossover values. As I said, I think I need to actually mesure the drivers before ordering any crossover parts. If anyone has actual measurements of all these drivers, I would appreciate it, give me something to do.
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Old 19th June 2008, 02:57 AM   #2
pjpoes is offline pjpoes  United States
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oh I should probably put in some links to the other sites and let you know which drivers I'm using. This is all very preliminary, so I'm not set on the drivers. I could use the Focal TC120Td5's I have, I could go with the Aircirc, we shall see.

The current drivers I'm thinking and modeling with are the Scan-Speak 18W/8531G00 x2, 12M/4631G00 x1, and the Vifa Xt25BG60-04 (New dual magnet version). I know that tweeter seems a little out of place considering the other drivers, but I think it might be a good option, and the Scan-Speak version is just too expensive.Ekta Grande
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Old 19th June 2008, 04:31 AM   #3
bastek is offline bastek  United States
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It would be great to see (and hear, i'm in NY also) the Ekta Grande. This is a large room speaker, so i'm sure you take this into account. I did build the Selah audio SSR, and the mids from the 18w/ 8531 sound great. good luck with your project.
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Old 19th June 2008, 04:49 AM   #4
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pj,

Where have you sourced your FR data for the drivers? What offsets are you using in SW (assuming you've chosen / re-using the Etka baffle geometry).

Can you post an impedance curve.

Thanks,
David.
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Old 19th June 2008, 09:13 AM   #5
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what is up with the offset baffle on the Etka Grande? Cant see how the front baffle wouldnt achieve same results with a centered version. I guess I need to be educated. Thanks in advance.
Brad Wellman - Spinnerbait15
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Old 19th June 2008, 12:11 PM   #6
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I would stick with the proven design using the XT25TG-30-40, which is excellent value compared to the D2904/7000. If you make adjustments, then you are building a different loudspeaker.

I know that Troels has some XO variations for different tweeters on the original Ekta. 95000, or 97000 if I remember correctly.

I suggest that you contact him. He is usually very happy to discuss options.

Let us know how you get on.

Good luck
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Old 19th June 2008, 05:43 PM   #7
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I am in the process of building the ekta grande right now. All my crossovers are complete. I normally build all the cabinets myself, but this time, a friend of mine is getting the cabinets built, and is buying me a set as well. So I couldn't complain too much about that. Both him and I will be using the 7000 ring radiator. While it may not be a great value, I suspect it is better than the Vifa. I know troels likes the Vifa better, but according to zaph's site, the 7000 is better.

I had every intention of building Zaph's 2 1/2 way, but I think you are right, it will help with the midrange. I'm excited to get this project complete. I think the sound quality should be very impressive.
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Old 19th June 2008, 09:43 PM   #8
pjpoes is offline pjpoes  United States
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Yeah, First, let me say I fully understand that changing values will change the design, thats why I said that. First let me say that I realized my own offsets were completely wrong, and I need to change that, er rather, i did change that, and found that very different values were needed. Oops!!! Thats what I get for modeling things quickly.

As for where I got my data, I was able to get actual impedance measurements for the woofers and midrange, but not the tweeter. The FR files are traces, nothing more. I don't usually trust them much, but to be honest, I've been told they are closer than I would give them credit for (Probably depends on how carefully you trace, and how many data points you use). I would much prefer real measurements for the FR files, and some real impedance files for all the speakers, but that means buying the drivers, which I can't do at the moment.

I'm planning on putting them into a smaller sealed box, as the bass will be fine (They will be used with a subwoofer), and I like the sound of those drivers in sealed boxes.

I will talk with Troels, if I can, about the crossover some more. I'm thinking of the Aircirc tweeter as an alternative. However, I feel like his cap size choice in the midrange is too small for good response, and would like to see what he thinks of enlarging that to something in the 30-40uf range.
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Old 20th June 2008, 12:47 PM   #9
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Maybe the Vertigo is also worth considering?

It is a very good sounding 3-way design with the following SS -drivers:

T = 7000
M = 12M
W = 18W

You can download the drawings & X-over here:

http://www.audiocomponents.nl/speake...ad/vertigo.zip
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Old 21st June 2008, 01:03 AM   #10
obiwan is offline obiwan  Australia
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Vertigo looks good. If it had 2 bass drivers per speaker it would be perfect. Think I'd just want the greater headroom/safety of 2 bass drivers per side.
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