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Old 14th August 2013, 12:12 AM   #31
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Quote:
Originally Posted by Loren42 View Post
3. Published T/S parameters are, at best, an average, and many times a simple fabrication by marketing. It's like shooting a rifle. You can slap a scope on and shoot away, but the results will more than likely be very bad until you align the scope. Again, the amount of effort you put in will reward your results and measuring the T/S parameters is not that hard.
Since T/S parameters are curves and not scalars, i feel it is important to have some tolerance of their changes under dynamic conditions -- a tightly tuned box will, most of the time, be out of tune.

dave
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Old 14th August 2013, 09:21 AM   #32
schmeet is offline schmeet  United Kingdom
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Quote:
Originally Posted by planet10 View Post
Since T/S parameters are curves and not scalars, i feel it is important to have some tolerance of their changes under dynamic conditions -- a tightly tuned box will, most of the time, be out of tune.

dave
What this guy said!

People get too hung up on things like:

"this program shows a 1.56dB rise in frequency response at 52.8Hz and program b doesn't. Which one is right?"
"how do I get rid of this 3dB ripple in my response".
"Is the Fs of my speaker 23Hz or 24Hz?"

You need to be aware of the tolerance, errors and 'ripple' of the whole system including, source, microphone, driver, cabinet, room, your ears etc. etc.

Don't try and design to such small tolerances, it's not practical. I tend to work to 3dB ish.
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Old 14th August 2013, 11:34 PM   #33
Jsixis is offline Jsixis  United States
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I always lean to a larger box. When using winisd I always round the numbers up on box size, then I'll add any angles I want to the design.
We are not making rockets, no 2 speakers will have the same specs. I've measured 100's they are all over the place.


Quote:
Originally Posted by The golden mean View Post
But he also suggest (if memory serves me) to build a temporary enclosure about 20% too large and measure, then if necessary diminish it by placing objects into it.

A 24 % change in Vas as in the example is significant.

Actual measured t/s data of pre and post break-in of the Audax AP100Z0 loudspeaker drivers. Shown over 0, 30, 50 and 70 hours.
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Old 14th August 2013, 11:37 PM   #34
Jsixis is offline Jsixis  United States
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wow, your WinISD layout is totally different then mine. Intersting.

Quote:
Originally Posted by Zero D View Post
@ Mr Jeff

I think you might like WinISD, i've been using it for years & have designed lots of nice sounding etc cabinets with it. I wrote a Help thread which should assist

How to correctly use WinISD

Latest version is here http://www.linearteam.org/download/winisd-07x.exe
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Old 22nd August 2013, 08:54 PM   #35
colofan is offline colofan  United States
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Also one small fact that is usually missing in modeling is that power level can and does change performance. T/S was designed around small signal levels where many assumptions were made on linear aspects of materials. High power changes a lot of things. You can still read the original article on how the Thiel/Small parameters are derived (mostly for engineer types (I admit it)) really depends on your math and physics skills. My point is most of the software floating around is based on something created in 1973. Yep some of us have been around this even before that
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Old 10th September 2013, 02:40 AM   #36
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I have a question about box design software...I recently purchased a new sub and in the process of choosing which driver i was trying to model each driver using the specs manufacturers posted...I kept getting a curve with peaks in the 110-130Hz range...i contacted the various companies and asked why this was...I was told that trying to model it was pointless given that the driver would have a totally different response after it is broken in. does this hold any truth?...to what degree
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Old 12th September 2013, 10:46 PM   #37
colofan is offline colofan  United States
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Quote:
Originally Posted by corie5508 View Post
I have a question about box design software...I recently purchased a new sub and in the process of choosing which driver i was trying to model each driver using the specs manufacturers posted...I kept getting a curve with peaks in the 110-130Hz range...i contacted the various companies and asked why this was...I was told that trying to model it was pointless given that the driver would have a totally different response after it is broken in. does this hold any truth?...to what degree
Which package are you using?

Sometimes boundary conditions reinforce that frequency range if reflections off the floor are taken into consideration.

What alignment are you using? (Sealed, ported, bandpass, horn..???)
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Old 13th September 2013, 02:27 PM   #38
schmeet is offline schmeet  United Kingdom
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Quote:
Originally Posted by corie5508 View Post
I have a question about box design software...I recently purchased a new sub and in the process of choosing which driver i was trying to model each driver using the specs manufacturers posted...I kept getting a curve with peaks in the 110-130Hz range...i contacted the various companies and asked why this was...I was told that trying to model it was pointless given that the driver would have a totally different response after it is broken in. does this hold any truth?...to what degree
I believe that the drivers specs that the manufacturer supplies are supposed to be after the driver has been 'broken in'. So although it will change, it should start out 'wrong' and become 'right'.

Therefore it is not pointless modelling drivers. Hence why we all do it!
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Old 13th September 2013, 06:13 PM   #39
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When you say "...peaks in the 110-130Hz range... what do you mean?

Is that flat-peak-flat or is the simply a response that has a general peak in that range, as in rising-peak-falling response.

The "Q" you specified in the design effects how the speaker will respond. A Q of 2 will have a large bass peak, a Q of 1 will have a slight bass peak, a Q of 0.7, most often regarded as the ideal, will have pretty flat response. A Q of less than 0.7 will have a much slower but likely deep roll off.

In certain software packages this "Q" is determined by the answer to a question - Do you want Most Bass, Flattest Response, or Deepest Response? If you choose Most Bass, then you chose to have this artificial peak.

Could you give us a screen shot of the response graph you are talking about, then we would have some framework for our answers?

Steve/bluewizard
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Old 13th September 2013, 06:21 PM   #40
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Again, precisely what you mean by a peak in the 110hz to 130hz range is vague. In a manner of speaking, all a Subwoofer is, is the peak of an arc. The response is the peak of a inverted parabolic arc. We simply slice off the top of that arc and call that our working range.

Think about how narrow the response is for a Subwoofer - say 20hz to 200hz. That is a very small window, and could be nothing less than an arc peaking around 100hz.

So again, are we talking flat-peak-flat, or is this simply the top of a gradual rising-peak-falling arc?

Steve/bluewizard

Last edited by BlueWizard; 13th September 2013 at 06:23 PM.
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