Baffle Step Correction: ignored in commercial systems - diyAudio
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Old 6th June 2004, 01:15 PM   #1
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Default Baffle Step Correction: ignored in commercial systems

Thanks to the people in the NET I've learned about this potential problem.
However it seems that commercial systems completely ignore that "feature": if one looks at the frequency response of these systems one can see a FR that is (at its best) flat.
On the other side I had the chance of experimenting with a B&W 704. They are declared as flat. When positioned near the walls the basses had the tendency of mix up with the mediums. I've got a decent results only with the speakers in the middle of the room (so, no ... WAF at all).
So, it seems to me that the reflections from the back greatly reduce the problem. People says only by 3dB, it could be more.
What is your thought and experience ?
Thanks
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Old 6th June 2004, 02:25 PM   #2
Ola is offline Ola
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What has all this to do with the baffle step thing?
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Old 6th June 2004, 02:32 PM   #3
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teadorom

You have discovered for yourself why most companies don't use BSC. It tends to get swamped by room modes, speaker positioning etc...
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Old 6th June 2004, 02:34 PM   #4
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I think you've confused baffle step with room nodes. The baffle step takes place where the baffle is one wavelength wide; above the step frequency the radiation is unidirectional, below it radiation is omnidirectional. When the radiation shifts from unidirectional to omnidirectional there is an on-axis SPL drop of 6dB.

If the baffle is 30cm wide the baffle step takes place at about 1130 Hz; a 15cm wide baffle has the step at 2260 Hz and so forth. For that reason the baffle step is primarily a midrange concern. Your problem is more likely to be related to room response frequency nodes.
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Old 6th June 2004, 03:41 PM   #5
sreten is offline sreten  United Kingdom
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simply not true, baffle step is all too apparent in anechoic
measurements at 1m (or 2m) and speakers measuring
flat in fact have included baffle step compensation.

Speakers designed as such are not suited to close to wall placement.

Optimum placement has been done to death allready,

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Old 6th June 2004, 05:07 PM   #6
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Default Until no w ...

Until now I have received two contrasting answers:
1. BSC is ignored by commercial designers because there are other nightmares caused by in room positioning that tend to obfuscate the (eventual) BSC solution
2. When measuring FR, commercial designers already take into account BSC, so the FR diagrams one can find in magazines are made flat (+3-6dB in the 2pi region) in some way (active vs. passive compensation)
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Old 6th June 2004, 05:15 PM   #7
sreten is offline sreten  United Kingdom
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2) is the case for quality "hifi" speakers.

1) is the case for cheap speakers and a lot of AV speakers.

Case 3) is including some BSC, but not enough for free space placement.

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Old 6th June 2004, 05:55 PM   #8
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Default I could agree but ...

I could agree but ... how can one distinguish ?
I've never, never heard about it in the (italian) magazines.
I read Audio Review and Costruire Alta Fedeltà (CHF).
Let me give some examples:[list=1][*]Wilson Audio Sophia, 18550€[*]Focal JM Lab Diva Utopia, 10550€[*]Nagra HP, 24000€[*]Mission Pilastro, 37000€[/list=1]
All the FR are flat, measured by the magazine and they never mention BSC.
Please, don't assume that I'm saying that BSC is a no-problem, that all of you are crazy or deaf, I'm only trying to understand the problem and then take my decisions (and spend some amount/a lot of money).
Thanks
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Old 6th June 2004, 08:31 PM   #9
sreten is offline sreten  United Kingdom
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They don't mention BSC because its accounted for.

go to www.seas.no and look at the graphs of the drivers
measured in boxes, not in flat baffles, the 6dB baffle step
should be obvious.

Note a bass/ mid driver measuring 91dB on a large baffle
= one that will measure flat in a box at 85dB with BSC.

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Old 6th June 2004, 10:51 PM   #10
lowHz is offline lowHz  United States
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I know of two very high priced speakers that do not have any baffle step at all. The Krell LAT-2 and the Wilson Audio Cub. I have measured them too. (I own LEAP 5 and LMS 4 from LinearX...) There is an online review of the Krell somewhere that clearly shows the drop in output below 800 Hz or so. Both speakers sound incredibly bright and fatiguing, especially after a lengthy listening session. (5 minutes )

A usual giveaway to no BSC is speakers that have very high efficiency ratings. (The CUB is rated at 93 dB I believe...) Taking 3 to 6 dB of efficiency away from a speaker for something that many consumers are completely unaware of (and usually don't understand) doesn't look good on paper, and usually isn't in their best interest since most speaker companies are out to sell speakers. Sad but true. On the salesfloor, it is often akin to selling televisions. The brightest TV always looks the best to untrained eyes. Any speakers being A/B'ed with a pair of Klipsch speakers will typically "lose" if the person giving the comparison is not adjusting the gain.
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