baffle step frequency

[ctrlx]

hi, i am trying to figure out my baffle step frequency.
unfortunately so far i have 3 differing numbers.

using the "formula" method i get 4560 / 12inch = 380Hz
using "the edge" program i get 144Hz
and after doing an "in-room" response test it could be interperated at 600Hz!

the baffle is 12 by 41inch (31x105cm) - any tips / suggestion are welcome.

 

[Lojzek]

Jeff Bagby's Software Page

 

[ctrlx]

Jeff Bagby's Software Page

i got a figure of 164Hz with that, pretty close to "the edge" value of 144Hz.

 

[Tyimo]

Hi!

What confuses me is how much is the Baffle step roll of? Most places was wtiten 6dB/octave, but on the graphs seem much less.
Another question: if I use BSC which is dimensioned for a given frequency,( say 200Hz,) is it means that on this frequency the BSC's operation start, or it is already -3 dB below like the first order crossovers in the crossover point?

Greets:
Tyimo

 

[sreten]

Hi,

The baffle step for a box is 6dB (with a ~ 2dB bump) total.
Its nowhere near 6dB/octave. Frequency is the 3dB point.

rgds, sreten.

 

[Tyimo]

Thanks Sreten!

Can you tell me how many dB/octave is the BSC's slope?

greets:
Tyimo

 

[sreten]

Zaph|Audio - ZA-SR71

Hi, It varies somewhat, as you would expect, rgds, sreten.

 

[woody]

Here is an article on it. It explains that this is not a 6db/oct but rather
a 6db total step responce . https://www.trueaudio.com/st_diff1.htm

 

[PeteMcK]

Baffle Step Compensation

Baffle step freq = 115/width in metres
= 115/.31 = 371Hz

 

[Tyimo]

Thanks to everyone!

I can see the BSC ciruit's operation in fig.4 Baffle Step Compensation

Greets:

Tyimo

 

[midrange]

There seem to be 2 significantly different results, one circa 150Hz, and one circa 380Hz. Can someone explain why.

 

[twinter]

Simplified approximation of baffle step slope is 2 dB/octave for 3 octaves, frequently starting around 200 to 250 Hz.

 

[PeteMcK]

re:"2 significantly different results" - because you're using the height for one of the calculations, rather than the width....

 

[danielwritesbac]

spreadsheet version

 

[5th element]

re:"2 significantly different results" - because you're using the height for one of the calculations, rather than the width....

I do not believe this is the problem. Some programs use the f3 where as some seem to use the f1 or similar. It can be quite confusing. I thought the f3 point, as per 'the edge' was standard protocol, but it seems like it is not.

 

[Tyimo]

Some programs use the f3 where as some seem to use the f1 or similar. It can be quite confusing. I thought the f3 point, as per 'the edge' was standard protocol, but it seems like it is not.

It confused me too.

I learnt from Troels: Any driver mounted on a baffle will have an f3 = 11,600/width of baffle in cm, but soemtimes I see this as f1.....


Greets:
Tyimo

 

[rich31td]

The way I understand it, the 6dB baffle step is only applicable is if the speaker is situated in free space away from any reflective surface.

If the speaker is close to a rear wall then 3dB is more realistic and if the speaker is close to a corner the no BSC is required, probably.

The distance to the nearest reflective surface may also alter the baffle step frequency as well as the SPL and of course the listening distance is worth consideration if used as a near field speaker.

The best way to be sure is to measure the speaker in both free space and also where the speaker will be positioned.

 

[Tyimo]

Is the Variable Equaliser circuit on the ESP site a "line level" type or before the driver to use?
Which BSC circuit is better:
1. signal parallel cap+resistor
2. signal series choke+resistor ?

 

[twinter]

The way I understand it, the 6dB baffle step is only applicable is if the speaker is situated in free space away from any reflective surface.

If the speaker is close to a rear wall then 3dB is more realistic and if the speaker is close to a corner the no BSC is required, probably.

The distance to the nearest reflective surface may also alter the baffle step frequency as well as the SPL and of course the listening distance is worth consideration if used as a near field speaker.

The best way to be sure is to measure the speaker in both free space and also where the speaker will be positioned.

That's correct.

Baffle step compensation is the electrical attenuation in the crossover to balance the totalized direct and indirect sound for best subjective fidelity, to counteract the baffle step phenomena, and boundary walls. Compensation is typically in the 3 to 4 dB total range in normal rooms.

 

[twinter]

Is the Variable Equaliser circuit on the ESP site a "line level" type or before the driver to use?
Which BSC circuit is better:
1. signal parallel cap+resistor
2. signal series choke+resistor ?

In a two way system, baffle step compensation can frequently be incorporated into the network by increasing the inductance of the series inductor (choke) to the woofer. Of course, other network component values will have to adjusted accordingly to ensure proper slopes, damping, and phasing. Application of BSC and its magnitude cannot always be determined by just viewing the crossover components.