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Old 3rd February 2011, 08:49 AM   #311
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I also made my ss15s with 3/4 external by adding a half inch to the side panels in both dimensions.
Those numbers seem a bit optimistic though dont they? Even if they are, if still measures really really flat! Ive not tested my pair yet but i'm really really happy with them. They have gone straight into service with gigs about 5 nights a week. i will be building a whole shed loads more.
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Old 3rd February 2011, 11:14 AM   #312
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Quote:
Originally Posted by FlipC View Post
I think your test are a bit skewed.

Weighting on the rack shack?
Distance from mouth to meter?
Voltage into speaker?
I'm a bit of a noob at this, so I don't understand what you mean by "skewed".
In what way? What is "weighting"? distance from mouth to meter was posted.
one meter. voltage was 2.83 volts. I'm assuming the voltage doesn't have to be reset for each frequency change? Each burst of the sine wave was for three seconds and each frequency was run three times. there was no wind. the meter was on a stand pointed at the center of the horn opening. I was as carefull as I could be. I'm not interested in fooling myself, or others, with bogus numbers. The meter does have a possible inacuracy of +- 2 db though. that's the specs given. Yes, the numbers seem almost unbelievable, I can't dispute that and I can understand the doubts in peoples minds. If it helps, I would be willing to post actual video of the test in progress, too alleviate all doubt.

tb46:

I'll be doing the first bracing test today. I've got a bad feeling about it though. Somewhere on this site, I read a post stateing that panel resonance can smooth out a responce curve. I've got a feeling that the agressive use of bracing may have been an issue with the last cab I built.
Anyone have any thoughts on this?

Dave nonzero:

did you ever run a test on your cabs? would love to see your results.
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Old 3rd February 2011, 11:47 AM   #313
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Default Just to confirm

Which driver did you use, runrod1948 ?

Was it a normal 3015LF, 8 ohms?

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Old 3rd February 2011, 02:58 PM   #314
tb46 is offline tb46  United States
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Hi runrod1948,

I think your testing is fine for a starting point, and should be repeatable, that's really more important than the absolute accuracy. I is a heck of a lot better than anything I've been able to find time for in the last year. Thanks.

My past experience with inadequate bracing has always been a loss of output at the frequencies where a panel is resonating. In a tapped horn that may reduce an unwanted peak, but I doubt that it can fill in a dip in the response. So it would be interesting to see if that still holds true. Bracing could reduce the cross-sectional area of the horn, and that should be taken into account (particularly in the throat area), but I doubt the area reduction matters much in the large sections of a tapped horn.

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Old 3rd February 2011, 03:04 PM   #315
tb46 is offline tb46  United States
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Default Simulation v. Actual

Hi hellonwheels,

Take another look at soho54's comments in Post #298.

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Old 3rd February 2011, 03:32 PM   #316
jbell is offline jbell  United States
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Quote:
Originally Posted by tb46 View Post
Hi runrod1948,

I think your testing is fine for a starting point, and should be repeatable, that's really more important than the absolute accuracy. I is a heck of a lot better than anything I've been able to find time for in the last year. Thanks.

My past experience with inadequate bracing has always been a loss of output at the frequencies where a panel is resonating. In a tapped horn that may reduce an unwanted peak, but I doubt that it can fill in a dip in the response. So it would be interesting to see if that still holds true. Bracing could reduce the cross-sectional area of the horn, and that should be taken into account (particularly in the throat area), but I doubt the area reduction matters much in the large sections of a tapped horn.

Regards,
runrod:

I've never had an issue with 'hollow' bracing, only solid bracing. In particular a solid brace down the back cuts 40hz response by a couple db.

brace away, just keep it as open as possible.

I too think 111 is a bit optimistic, sounds like your ratshack is reading a bit high. Other than that, looks like the nice flat numbers I would expect, with the addition of more drop off due to your 50hz high pass.

glad you like your cabinet... it's one of the few designs of mine I'm happy with.

Last edited by jbell; 3rd February 2011 at 03:36 PM.
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Old 3rd February 2011, 04:04 PM   #317
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by jbell View Post
I too think 111 is a bit optimistic,
Does the poster say what signal voltage or what driver impedance he used for the test?
Or is he simply giving us his results for a comparative frequency response based on his test conditions?
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Old 3rd February 2011, 04:13 PM   #318
Xoc1 is offline Xoc1  United Kingdom
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I decided to have a go at plotting out the horn dimensions 'as drawn' to try to fathom out what is going on with this sub.
The results of the unfolded taper are reasonably linear apart from two restrictions.
When I sim with these results, and adjust the level to 7.5 V to match Runrods sensitivity readings it tracks his results within his 2db tolerance level.
Then I notice that Runrod says he is running a 50hz hi-pass (the plot thickens!)
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Old 3rd February 2011, 04:14 PM   #319
tb46 is offline tb46  United States
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Hi AndrewT,

Take another look at posts #307 and #312. Maybe runrod1948 can describe the environment is some more detail, but the main thing is that he repeats the tests with an identical (similar?) setup.

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Old 3rd February 2011, 04:23 PM   #320
AndrewT is offline AndrewT  Scotland
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Hi TB,
yes, both both clearly state 2.83Vac
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