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post #31 of 37 Old 08-18-2013, 04:11 AM
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Originally Posted by Bob Sorel View Post

The problem, however (and the same happens with the Blueprint driver), is that, according to my research on the Web, both the HE-15 and Blueprint drivers have Vd in excess of 6 liters - this was one of the things that made these drivers so special at the time. AND the Xmax figures are also correct, so for whatever reason, the formula WinISD is using does not apply to these 2 drivers. I will not even pretend to understand why this is so, but if you search for info on the Web you will find threads talking about the high Xmax and the Vd in excess of 6 liters.
I never pay attention to what people "say" about things like Vd; it is a simple calculation (Sd x Xmax) so I do it myself. I believe the math rather than anecdotes or people merely repeating something they have heard without checking it out themselves.

For the BP: 804cm2 x 2.59cm = 2082cm3 or 2.082l one way, or 4.164l two way. Not 6l.

Though I don't use or like WinISD (I prefer Unibox), I never found it to be inaccurate. Vd is a large signal parameter and will not affect calculations using the small signal T/S parameters when determining box volumes etc.
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post #32 of 37 Old 08-18-2013, 11:21 AM - Thread Starter
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Vd is a large signal parameter and will not affect calculations using the small signal T/S parameters when determining box volumes etc.
Great! That's all that is important to me.

Now have to figure out why the modeling of these drivers looks so poor in a sealed enclosure...back to Google to at least attempt some self education.

Thanks for all of your help!

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post #33 of 37 Old 08-18-2013, 12:42 PM
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when you say "Now have to figure out why the modeling of these drivers looks so poor in a sealed enclosure..." what do you means?

if the driver has a powerful motor, the f3 will tend to be rather high and the driver will have a reasonably low qts in a very small enclosure. upper end sensitivity will be highish. lower end sensitivity will be lowish. but the driver can still typically be pushed to max excursion on the low end with equalization and sufficient power.

if the driver has a weak motor, the f3 will tend to be rather low and the driver will have a reasonable qts in a medium to large enclosure. upper end sensitivity will be lowish and lower end sensitivity will be highish. less equalization and power will be required to push the driver to its excursion limit.

there is a little more to it, but hope that helps explain some of what you are seeing.

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post #34 of 37 Old 08-19-2013, 07:03 AM
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Quote:
Originally Posted by Bob Sorel View Post

Great! That's all that is important to me.

Now have to figure out why the modeling of these drivers looks so poor in a sealed enclosure...back to Google to at least attempt some self education.

Thanks for all of your help!

To simplify what LTD02 said, they don't model bad. They model like a good sealed sub. You add in room gain and add a little eq and response will be flat.
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post #35 of 37 Old 08-19-2013, 04:19 PM - Thread Starter
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Thanks for the replies, guys.

I guess I really have a lot to learn about modeling. The tutorial I only used ported boxes as an example and seemed to indicate that I should play around with box size, tuning frequency, port diameter, and port length in order to flatten the frequency response of the sub as much as possible, or at least that is how I interpreted the instructions. And I found that it was fairly easy to juggle those parameters in order to achieve results that looked pretty flat on the transfer function magnitude graph.

But with sealed boxes, the only variable is box size since there is no port to affect frequency response otherwise. When I looked at the transfer function magnitude graph of the 2 drivers I own, I noticed that the sub starts to roll of around 200 hz, and F3 is around 65 hz. F10 is 28 hz, and at 20 hz the sub is down to -14 db. After playing around with ported enclosures, this looked pretty bad to me, but after the explanation from both of you, LTD02 and nograveconcern, I understand how the sealed design can be made to be flatter in room. Not considering room gain, I can improve the response significantly by adding a parametric EQ at 20 hz with 12 db gain and a Q of 1.5. 12 db is a pretty drastic increase in gain, though, and I assume that it would cause other complications, like running out of power, but I don' t know due to lack of experience and knowledge. Chances are that with the room gain I would not need such a high boost at 20 hz either.

Is there any general rule of thumb or common policy used when adding DSP to sealed boxes?

Thanks again for your patience as I go through this learning process.

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post #36 of 37 Old 08-19-2013, 05:24 PM
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You have to measure using a program like REW and adjust. 12db @ 20 would be a ton of gain. If you need that much gain to be flat then you might want a different alignment than sealed. However, a room can give you as much as 12db per octave below a predictable frequency based on the longest room dimension or some such thing. It depends on placement of the subs as well. Again, measurements are key.
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post #37 of 37 Old 08-19-2013, 05:47 PM
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Quote:
Originally Posted by Bob Sorel View Post

I just downloaded and installed WinISD Pro 0.50a7 and entered the HE-15 parameters in the driver editor, but when I try to save it I get a window saying "parameter error list" and the window lists a bunch of "errors". I rechecked to make sure that I entered things correctly - like entering Vas in liters), but no go. The help button doesn't work either.

Am I using the wrong program?

Edit: Ahhh...as long I uncheck the "auto calculate unknowns" box, then I can save the data...smile.gif

The non-pro version of WinISD (version 0.44) works fine on my Windows 7 machine. WinISD Pro seemed full of bugs...to me.
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