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Old 6th August 2013, 07:17 AM   #131
Kev06 is offline Kev06  England
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Thanks also Greebster and face, yeah it seems like it could be a range of values depending on circumstances.. So I'll also have a look at the Diffraction and Boundary Simulator stuff, looks interesting from the screen shots.

I think ultimately i'll have to build some trial enclosures and get some sort of microphone for actual testing before I leap in with making the real cabinet. But if I can get it roughly right to begin with it'll help avoid fundamentally awkward mistakes with the choice of drivers.

Cheers
kev
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Old 6th August 2013, 08:12 AM   #132
Kev06 is offline Kev06  England
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A potentially daft question.. The SPL/sensitivity charts and specs for drivers don't always say if they were taken in a baffle or not (sometimes they do and have been), which may be one reason why WinISD often has a slightly different view of what the sensitivity is.

Should I assume that WinISD's sensitivity calculations are always for just the driver and that baffle gain would be on top?

Thanks
Kev
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Old 6th August 2013, 09:20 AM   #133
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I thnk that winisd modeled results assume an infinite baffle. So what you will actually see is a "potential" 6 db loss at the lowest point of the diffraction curve as opposed to any gain in the higher frequencies.

In any normal room though you will not need full 6db of compensation.

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Old 6th August 2013, 10:37 AM   #134
Kev06 is offline Kev06  England
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Thanks Tony

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Kev
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Old 6th August 2013, 01:13 PM   #135
Kev06 is offline Kev06  England
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I have looked into baffle step a bit more now; its perhaps not as scary as i thought, though I think i'd need measuring equipment to have confidence in purposely using it rather than avoiding it.

There are circuits that would help compensate, but would I be right in thinking that arranging the baffle size to step at about the mid/bass crossover frequency would let me compensate well enough simply through altering the relative driver/amp power?

Cheers
kev
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Old 6th August 2013, 01:22 PM   #136
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Originally Posted by Face View Post
As mentioned above, it depends on the room.

I find this program very accurate: Loudspeaker Design Software
Have it and is a very good suggestion.
Still relying on my rules of thumb, they hold up quite well and when they don't I'll crank up BD/BS
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Old 6th August 2013, 01:38 PM   #137
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Quote:
Originally Posted by Kev06 View Post
I have looked into baffle step a bit more now; its perhaps not as scary as i thought, though I think i'd need measuring equipment to have confidence in purposely using it rather than avoiding it.

There are circuits that would help compensate, but would I be right in thinking that arranging the baffle size to step at about the mid/bass crossover frequency would let me compensate well enough simply through altering the relative driver/amp power?

Cheers
kev
The width changes the frequency where BSL kicks in. Wider, lower the frequency, narrower higher. If made sufficiently wide we don't have loss aka an infinite baffle. Floor loading also doesn't have the low end loss caused by a narrower than optimal baffle that plagues tall thin towers. Changing level will raise or lower the entire spectrum of said driver when what we require is more akin to a shallow low pass filter, which sacrifices effeciency at the top end. Adding additional drivers as in an mtmMM where the MM sums with the mm to compensate without loss of effeciency. This can be 2/3 or 4 additional drivers depending on placement eg 3dB, 4.5dB and 6dB compensation. Floor loading with only two drivers gain 6dB, in this case EQ is your friend.
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Old 6th August 2013, 02:17 PM   #138
Kev06 is offline Kev06  England
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Ah, thanks indeed. Yes i see what you mean about the shallow pass filter rather than raising the whole driver; guess the 'step' is too much of a gentle slope to deal with using driver power and a 4th order crossover point.. Possibly it would be easier to arrange for the baffle step to occur within a single driver's range and tweak just that driver's response curve. EDIT: although maybe its stoo shallow to fully do that..

I'd read about using extra drivers to fill in for losses via baffle step, but i suspect that may be getting a bit complex for my first real build. Although.. I would probably trust myself to try the floor loading with a sub.

cheers
kev

Last edited by Kev06; 6th August 2013 at 02:28 PM.
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Old 6th August 2013, 02:40 PM   #139
tinitus is offline tinitus  Europe
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Originally Posted by Kev06 View Post
I'd read about using extra drivers to fill in for losses via baffle step, but i suspect that may be getting a bit complex ...
that will usually be a 2.5way
(mostly a 2way with two identical woofers)

in a 3way its good practice to use a woofer with higher sensitivity that the mid

but BSC can be a very delicate balance act
its easy enough to attenuate a midrange
if you can live with that
but you really do not want to attenuate a woofer, in the common sense
but might be done by using very big inductor
though not very practical, and expencive

btw, box tuning could in some cases have some influence
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Old 6th August 2013, 02:51 PM   #140
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Or 3.5 way.

But then again, aren't you going with an active crossover?
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