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Old 26th August 2013, 01:38 AM   #21
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Originally Posted by Pallas View Post
I doubt that's the case. It looks like a very nicely thought-out and executed project. What I find especially interesting is that the measurements seem to show that Dave's WG removes the actual problem I've heard from the Vifa and ScanSpeak ring radiators: extremely extremely narrow treble dispersion.

That, by contrast, I suspect that would end up disappointing. Not because it wouldn't be good, but because there wouldn't be much improvement from what you already have. Probably get more people on forums to ooh and aah if you're able to throw out brand names like Audio Technology, Accuton, Scan Revelator, etc, but ultimately speakers really boil down to three things: listening axis FR, dispersion, and output capability. Your current project looks well-sorted for a speaker of that size. I'd say be happy, and add multiple subs.
Thank you. The lack of comments on the actual system had me thinking I wasted all the hours it took to document everything.

If you look at my pics in my original post you will see I run 4 15" TC sounds subs powered by 8000 watts.

I'm in sonic heaven right now.

Thanks again.
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Old 26th August 2013, 04:25 AM   #22
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Taking a closer look at how a wave guide/cap lowers distortion at frequencies over the crossover. Since a cap starts operating from a much higher freq to counter the lift of the guide, it is lowering distortion from above the cross freq.

Here is the bare tweeter distortion plot
Click the image to open in full size.

Here is the distortion plot with guide and cap. The F2 distortion is down by 25db at 2000hz and the response is again flat on the tweeter. Its not just low in frequency. Since the harmonics generate the noise up top that theyre based on, the F2 is down 15db from 6-10k Hz. Whats really interesting is that the higher order distortion is based on whats happening from the low end hiccups and thus the F4 and F5 is sent to the floor on the top of the range. Active crossover uses can use any slope they want countering the phase issues electronically. The roll off approximates an LR2 with just a cap. I dont know how to build passives but if you can then increase the crossover to LR4 from 1800 or so, the low end issues are off the map including the res freq ringing like a bell.
Click the image to open in full size.

1700 is not too low for an XT25 using a wave guide.

Last edited by SpinMonster; 26th August 2013 at 04:29 AM.
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Old 26th August 2013, 05:34 AM   #23
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Nice work Spin, thanks for the detailed write-up.
Looks like I'll have to get my xt25's reconed (connected to sub amp channel on active system.. Oooops) and make some guides.

All nitpicking aside, seems like some clear advantages to adding a waveguide to the xt25.

Cheers
Dean.
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Old 26th August 2013, 06:35 AM   #24
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While I'm at it. Does anybody know where I could get my xt25tg30-04 reconed or buy a kit?

Sorry for the OT, back to normal progam.

Dean
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Old 26th August 2013, 06:45 AM   #25
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Thanks for the post! Always good to have another build thread with detailed documentation.
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Old 26th August 2013, 06:48 AM   #26
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Originally Posted by thunk303 View Post
While I'm at it. Does anybody know where I could get my xt25tg30-04 reconed or buy a kit?

Sorry for the OT, back to normal progam.

Dean
The are not made to be fixed. The units are $35 for the better 60 model so its probably best to just upgrade
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Old 26th August 2013, 07:48 AM   #27
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just a short note
I made a small waveguide for a similar designed Vifa XT19 tweeter
at some point after dismantling I had problems with voice coil rubbing
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Old 26th August 2013, 08:21 AM   #28
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This is absolutely correct by the way. There is some gap flux addition, but the main effect is stray field reduction. The front plate also gets saturated, which reduces flux modulation. It is a Band-Aid however since this technique is an expensive waste of magnet volume.

Why is there a Hall sensor in a cell phone? How can it be used as you indicate?
Not sure why Earl, really do not know why. Have seen mention of an application where one could be tracked using magnetic field lines of force tho. You know, there's an APP for that! lol
Android Play store has several apps that allow direct reading of what is happening the Accelerometer (Gyro) and magnetometer (3 axis Hall) in 3 axis. Example : https://play.google.com/store/apps/d...eticspro&hl=en

There are many others on the market that will display the results of all the sensors built into most every Android device.

For the Trekie in me I use Tricorder also, which is a spin on ST the Next Generation Tricorder. Friend was laughing this afternoon when he asked someone if they were mic'd (a joke). Whipped out my phone and did a full body scan (with sound effects). Too funny.
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Old 26th August 2013, 08:26 AM   #29
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Quote:
Originally Posted by SpinMonster View Post
Taking a closer look at how a wave guide/cap lowers distortion at frequencies over the crossover. Since a cap starts operating from a much higher freq to counter the lift of the guide, it is lowering distortion from above the cross freq.

Here is the bare tweeter distortion plot
Click the image to open in full size.

Here is the distortion plot with guide and cap. The F2 distortion is down by 25db at 2000hz and the response is again flat on the tweeter. Its not just low in frequency. Since the harmonics generate the noise up top that theyre based on, the F2 is down 15db from 6-10k Hz. Whats really interesting is that the higher order distortion is based on whats happening from the low end hiccups and thus the F4 and F5 is sent to the floor on the top of the range. Active crossover uses can use any slope they want countering the phase issues electronically. The roll off approximates an LR2 with just a cap. I dont know how to build passives but if you can then increase the crossover to LR4 from 1800 or so, the low end issues are off the map including the res freq ringing like a bell.
Click the image to open in full size.

1700 is not too low for an XT25 using a wave guide.
I stand corrected, thank you

My other concern tho would be with excursion eg low end acoustic output. But with the waveguide helping alot here doesn't appear to be an issue.
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Old 26th August 2013, 10:02 AM   #30
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Originally Posted by Greebster View Post
I stand corrected, thank you

My other concern tho would be with excursion eg low end acoustic output. But with the waveguide helping alot here doesn't appear to be an issue.
The wave guide boosts 10db. After that you add in that the cap is starting to filter from 8000hz so by 1700 thats another 12db. The cap is filtering me past where the 4th order electrical was with what I guess is a 5th order electrical filter below 1700. I blew up quite a few bare tweeters which was the total system spl limit. Its hitting peaks far beyond where the 4th order electrical cross at 2000 was. At the listening position its 7db higher and the mid amps are now clipping so even thats not the limit. 5th order at 1700 minus 10db isnt more excursion than 4th order at 2000 was.

As a test, the mid amp is now the system limit even with me putting the crossover at 1500 4th order. 1700 isnt even close.

Also understand the reason I went to 1700 was to stop activating the 3000hz trigger for the twin peaks at 6k and 9k on the RS180. Had that not been the mid, I could cross higher if I used a scan speak midbass crossed at 2000hz.

Last edited by SpinMonster; 26th August 2013 at 10:12 AM.
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