[jeffh]

Danny,
In the current thread located here: http://www.audiocircle.com/index.php?topic=111297.msg1151871#msg1151871, you mentioned baffle step loss and the effect it has on the driver.

Could you please define and explain what this is in laymans terms? Pro's Con's etc...

[Danny Richie]

Imagine a driver mounted in a wall. All of its output moves forward and it has no loss at any frequency.

But when you mount it in an enclosure it looses low frequency output in relation to the size of the baffle. This is because the low frequency ranges become omni directional. So imagine if half of the output goes to the rear of the speaker and half to the front. Actually think of it as a rock thrown into a pond of water. The splash radiates in all directions. But only half of the energy comes toward you. The other half goes in the other direction. So you get half of the output.

So as the low frequency ranges wrap around the cabinet and that energy goes the other way then you loose about 6db of total output verses the directional output that radiates forward only and you get 100% of its output. In other words, as frequency increases they become more directional and do not wrap around the cabinet. They play from the cabinet forward. So you hear the full output.

As the baffle gets wider then lower frequency or frequency ranges at or near the transitional area reflect off of the baffle (or not depending on the wavelength) and don't wrap around the cabinet.

So on a 8" wide baffle that loss of output will start about 800Hz or so and drop off. On a 9" wide baffle it will shift to around 700Hz or so. The wider the baffle the lower in range the loss starts. Where that loss is located is called the baffle step loss.

In loudspeaker design we have to compensate for the loss of output. It is called baffle step compensation.

Make sense?

[gregfisk]

Imagine a driver mounted in a wall. All of its output moves forward and it has no loss at any frequency.

But when you mount it in an enclosure it looses low frequency output in relation to the size of the baffle. This is because the low frequency ranges become omni directional. So imagine if half of the output goes to the rear of the speaker and half to the front. Actually think of it as a rock thrown into a pond of water. The splash radiates in all directions. But only half of the energy comes toward you. The other half goes in the other direction. So you get half of the output.

So as the low frequency ranges wrap around the cabinet and that energy goes the other way then you loose about 6db of total output verses the directional output that radiates forward only and you get 100% of its output. In other words, as frequency increases they become more directional and do not wrap around the cabinet. They play from the cabinet forward. So you hear the full output.

As the baffle gets wider then lower frequency or frequency ranges at or near the transitional area reflect off of the baffle (or not depending on the wavelength) and don't wrap around the cabinet.

So on a 8" wide baffle that loss of output will start about 800Hz or so and drop off. On a 9" wide baffle it will shift to around 700Hz or so. The wider the baffle the lower in range the loss starts. Where that loss is located is called the baffle step loss.

In loudspeaker design we have to compensate for the loss of output. It is called baffle step compensation.

Make sense?

Danny, your explanations are very interesting and appreciated regarding this "baffle step loss" and also regarding the transmission of vibration from one speaker to the next. Do you in certain speaker designs widen the baffle to lower the loss of output?

The reason I ask is that you have mentioned before that it is better to have less baffle around a speaker. In most speaker tower type designs the speaker may have a very small baffle on the sides but of course the vertical baffle of the speaker is large.

Is there a time when it is better to have more baffle around a speaker in any free standing "not in-wall" type design?

Thanks, Greg

[Danny Richie]

I wider baffle will shift it to a lower range but not do away with it unless it is the size of a wall.

And again, adding a wider baffle will increase the surface reflections, and that is not a good thing.

I can compensate for the step loss with the network regardless of where it is.

You can also compensate for the loss with a three way design by letting the lower woofer (or woofers) fill in some of the loss, but you also have to be careful that you don't disrupt the mid-range by doing this.

Is there a time when it is better to have more baffle around a speaker in any free standing "not in-wall" type design?

Not that I can think of.

[jeffh]

And again, adding a wider baffle will increase the surface reflections, and that is not a good thing.

That explanation helps a lot, but let me ask this.  If a wider baffle is bad because of reflections, then baffle step loss is a good thing? Yes? But, if there is a need to compensate for it with the network, it seems like you would want a wider baffle.  OK, so I am still a little confused.

[Danny Richie]

That explanation helps a lot, but let me ask this.  If a wider baffle is bad because of reflections, then baffle step loss is a good thing? Yes? But, if there is a need to compensate for it with the network, it seems like you would want a wider baffle.  OK, so I am still a little confused.

Lets say the baffle is 7" wide and the step loss starts at 900Hz. We make the baffle 9" wide and now the step loss starts at 700Hz. You still have the same loss and both require compensation, but one has more surface reflections than the other (not good).

[stevenkelby]

Danny, does putting sides on a baffle (as in the Super V) lower the frequency for the baffle step loss, without increasing surface reflections?

[Danny Richie]

Danny, does putting sides on a baffle (as in the Super V) lower the frequency for the baffle step loss, without increasing surface reflections?

With an open baffle you can still have a step loss but you also get a dipole bump in the output.

Here is the same 5.25" woofer on two different 8" wide baffles with no network. One baffle is a small ported box (red line). The other is on an open baffle (green line).



Notice on the 8" wide ported box that the baffle step loss can be seen really taking a dive below 800Hz.

On the open baffle there is a huge peak at 1kHz. Making the baffle wider shifts that to a lower range, and reduces the height of the peak.

The idea of the Super-V baffle to shift it down into a lower range where the output is naturally rolling off. With the right sized baffle you can actually get a pretty flat response down to where the driver has a natural -6db down at the 200Hz crossover point. This is what was done with the Super-V baffle. It is 13" wide around the driver plus the wings on both sides. It makes it out to be about 23" wide if measuring from the middle of the driver starting at the back edge of one wing and wrapping around the front of the baffle to the back edge of the other wing. And the frontal area of the baffle is not much wider than the driver itself. 

[stevenkelby]

Thanks Danny, very interesting!

[fonz]

Hello Danny

I found this topic while searching for baffle step compensation.  I have a pair of speakers where the manufacturer supplied a baffle compensation device that inserts between the preamp and amp.  I notice great definition but the bass and dynamics do not sound as good as it does without it.  Is this common?

I use the Reference line Preeminence Two passive preamp.  I also own several active preamps as well and notice the same results.  The Reference Line which is my favorite was designed to overcome the common plagues of passive such as impedance changes that occur when the volume is turned up.

Educate me on what I should know about the baffle compensation networks.  From an emotional standpoint I'm feeling the system without the unit between my preamp and amp.

Best regards,
Fonz

[Danny Richie]

Hey Fonz,

I have noticed a few companies offering a similar device to compensate for the baffle step loss. The Merlin speaker company offers something like that on their top model and I have listened to them a couple of times. To me there is a slight muffled coloration added from the use of the op-amps in the device they use. Basically it is a selected boost range to pick up the bottom end. And to me the whole frequency range suffers some as the whole signal has to pass through that thing.

Keep in mind that just because the compensation is done actively does not mean there are fewer components in the signal path.

It can be done passively quite easily without adding additional crossover parts. It just uses a larger value inductor on the woofer and sometimes a lower crossover point.