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Old 13th May 2011, 01:27 AM   #21
AllenB is offline AllenB  Australia
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I'm talking of equalisation, are you now talking about multi sub augmentation, are we at crossed purposes?
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Old 13th May 2011, 07:28 AM   #22
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Quote:
Originally Posted by rabbitz View Post
It's about baffle width and the space where the speaker is working. To calculate the F3 at the baffle step use 115/baffle width in metres.

I'll give you a visual example of baffle step using ants.

With a speaker against the wall (2PI space), picture the baffle covered in ants. As some ants escape to the back of the speaker they can't hide so you see them all (no baffle step reduction).

With a speaker in free space (4PI space), the escaped ants now can hide behind the box so you can't see them, only the remainder. That's the SPL reduction from baffle step.
I've always wondered what BSC, I like the idea of using ants.

Is it only the baffle width that's taken into account? Would the height of the baffle affect things also?

I remember seeing an online BSC calculator that asks for height here: Online Baffle Step Calculation but I'm not really sure of the maths this calculator is using.

Anyway I've tried adding some BSC a few minutes ago using the 115/width calculation and I can say has improved the sound from these speakers quite noticeably.

Here's my speaker:
Click the image to open in full size.

Here's filter settings on my DEQ:
Click the image to open in full size.

115/0.261 = 440.6 Hz (442 is the closest setting on my DEQ)

I'm using a 6db/octave low pass filter, can someone confirm I've got everything correctly set here? Thanks.
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Old 13th May 2011, 08:08 AM   #23
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Quote:
Originally Posted by MikeHunt79 View Post
Is it only the baffle width that's taken into account? Would the height of the baffle affect things also?
I don't know if the height affects the BSC, but I think it was Thiele who wrote that you would get a better response if you had the box go all the way to the floor, even if it was just a smaller system (like a two-way or MTM).
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Old 13th May 2011, 09:07 AM   #24
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I'm learning so much in such a short time, I feel realy blessed.
Just now I got the sound of my pc speakers to sound nice for the first time.
Little Logitechs, I'm loosing myself in the decay of the drumstick hitting the side of the snare on Brothers in arms now. I was just trying to apply some of the things that started to pop out at me, like placeing the satelites right up against the wall, the added some gain in the 2 octaves under the BSC knee on the EQ, with the bass knob on the back of the "sub" dialed to 0. Allthoug it still has a sweetspot the size of a melon, the sound is rather full, and it realy is hard to believe it comes from those tiny drivers. Of coarse we are not compareing to a true hifi set of speakers
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Old 13th May 2011, 11:26 AM   #25
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Here is a link to a post I made comparing BSC before the amp vs after the amp. I call the latter 'shelving'. Response measurements were made that show the effect of each method on a vintage 2-way New Large Advent loudspeaker. Worth a view.

BSC vs Shelving - The Classic Speaker Pages Discussion Forums

Here is a link to the Basel BSC thread I referenced in the above link. It's become quite popular.

http://www.classicspeakerpages.net/I...showtopic=2692

Last edited by speakerdoctor; 13th May 2011 at 11:29 AM.
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Old 13th May 2011, 04:19 PM   #26
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Quote:
Originally Posted by MikeHunt79 View Post
I've always wondered what BSC, I like the idea of using ants.

Is it only the baffle width that's taken into account? Would the height of the baffle affect things also?

I'm using a 6db/octave low pass filter, can someone confirm I've got everything correctly set here? Thanks.
The height of the baffle determines the vertical "step", the width the horizontal "step" frequency.

Distance to the floor and wall and cabinet depth also play into the depth of the step.

A six dB per octave LP filter set to 442 Hz would be about -30 dB at 14,000 Hz.

The graphic picture of your response does not look like a 6db/octave low pass filter, but looks about like what a baffle step compensation should look like. Whether it is correct (or needed) for your speakers and their position in the room could be measured, but not determined by looking at a DSP display.

Looks like you are using a shelving EQ :^).
Like a "loudness contour", that type of EQ often "sounds better", especially when listening at a lower level than the music was mixed at.

Art
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Old 14th May 2011, 12:52 AM   #27
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by MikeHunt79 View Post
I've tried adding some BSC
Since baffle step compensation is a compromise rather than a correction, it is worth trying a total of 4.5dB and 3dB as well.
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Old 14th May 2011, 02:47 AM   #28
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The most uniform bass response comes from using 4 subwoofers (more is better but not necessary as 4 is usually sufficient) located in the 4 corners or the 4 midpoints of the room walls. This according to Harman International's web site based on the work of Floyd Toole. Of course these give more bass reinforcement than moving the speakers away from the walls. The corners restrict radiation to only pi/2 steradians and mid wall placement on the floor restricts radiation to pi steradians.
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Old 14th May 2011, 05:31 AM   #29
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I think it as width around the sides, as the ants can't go through the floor to go around the box verticaly....

The woofer I want to use has a bit of a riseing response as you go up in frequency with a particularly bad 12db bump just a short distance after the crossover point.

Do I understand correctly that with active CO we would boost the lower frequencies rather than cut like with passive CO?
Would if crossed over, the slope follow its original trend, just x-db down, or does it just smoothe out...? Getting a scope soon then I can ask less questions.

Last edited by digits; 14th May 2011 at 05:37 AM.
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Old 14th May 2011, 06:45 AM   #30
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by digits View Post
I think it as width around the sides, as the ants can't go through the floor to go around the box verticaly....
The floor, yes, except where stands are used , but vertically (above)? Why not?

Quote:
a particularly bad 12db bump just a short distance after the crossover point.
This sounds like cone breakup, and if so you are right to cross before it. It needs to be fixed in its own right which you can either do separately or together with other fixes.

Quote:
Do I understand correctly that with active CO we would boost the lower frequencies rather than cut like with passive CO?
When active, this point largely becomes moot. (For what it's worth, I'd use passive components in my line level circuits before the amp.) The point that has been raised, as far as I can see it, is that with a pre amp correction there will be no passive components wasting the amp's power.

To me this is irrelevant as either way, the power amp will always play the bass at the same level for a given power output. Since passive and active systems are both worthy and viable it becomes your choice.

Quote:
Would if crossed over, the slope follow its original trend, just x-db down,
Applying active corrections will not affect how passive components work with the speaker. They will simply add to the overall effect.
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