Should BSC change when cabinet height changes?

abefroeman · 23rd February 2009, 04:50 PM

Hey all, I found a 2-way floorstanding monitor design that I like and I would like to build shorter cabinets and use stands. Baffle width will stay the same but the speaker will end up shorter. Will this effect my BSC?

sreten · 23rd February 2009, 07:10 PM

Hi,

Check it with one of the baffle modelling tools. It will do if you mount
the bass mid very close to the bottom, further is harder to define.

/sreten.

BlueWizard · 23rd February 2009, 08:06 PM

Define 'Shorter'?

Do you mean shorter with less volume or shorter with equal volume?

I think baffle step is mostly related to baffle (front panel) width, so I suspect you would be OK relative to baffle step. But if you shrink the overal volume of the cabinet, the cabinet tuning and bass response completely change.

I think that is why SReten suggested you use a modeling program, so you can visualize the effects of the changes you are going to make.

Again, I think if all other dimensions remain unchanged, and you make the cabinet shorter, you are losing bass because you are losing overall volume.

A modeling program should show you the changes to the frequency response clearly.

Just an opinion.

Steve/bluewizard

abefroeman · 23rd February 2009, 09:29 PM

Internal volume will stay the same.

basically i am removing the area of the floorstanding plan that is dedicated for filling with sand, and replacing it with a speaker stand.

Pan · 24th February 2009, 07:14 AM

Quote:

Will this effect my BSC? [/B]

Yes!

/Peter

BlueWizard · 24th February 2009, 07:25 AM

Peter,

I have no problem bowing to superior knowledge, but could you explain how cabinet height effects Baffle Step. I always thought it was related specifically to baffle width in the area of the woofer.

In reality he is not going to change the cabinets internal working volume, so why should the parameters or response of the cabinet change?

I confess I'm no expert, but an expansion of your response would be helpful.

Steve/bluewizard

breez · 24th February 2009, 09:22 AM

Baffle height will change the radiation pattern in the vertical direction. Think about it, you could flip the speaker and now your height is the new width!

Stuey · 24th February 2009, 09:55 AM

Isn't it simply because the driver radiates in a sphere (or half sphere, depending on frequency). Therefore, the height also makes a difference to that forward radiation.

However, as most baffles are narrower than they are wide, the biggest effect is caused by differences in width, because this has the greatest effect on total baffle area per mm of change in dimension (width vs. height).

I think, anyway...

Stuey

abefroeman · 24th February 2009, 08:00 PM

where can I find a calculator for BSC?

smellygas · 24th February 2009, 08:15 PM

Doesn't the Allison Effect cause frequency response dips/peaks relative to the speaker height (as well as wall distance)? I would think that this should be taken into account as well. I guess you could also just measure the frequency response with varying cabinet heights to see if you need to change your BSC!

SG

23rd February 2009, 04:50 PM	#1
abefroeman diyAudio Member Join Date: Feb 2009	Should BSC change when cabinet height changes? Hey all, I found a 2-way floorstanding monitor design that I like and I would like to build shorter cabinets and use stands. Baffle width will stay the same but the speaker will end up shorter. Will this effect my BSC?

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23rd February 2009, 07:10 PM	#2
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, Check it with one of the baffle modelling tools. It will do if you mount the bass mid very close to the bottom, further is harder to define. /sreten.

23rd February 2009, 08:06 PM	#3
BlueWizard diyAudio Member Join Date: Jun 2007	Define 'Shorter'? Do you mean shorter with less volume or shorter with equal volume? I think baffle step is mostly related to baffle (front panel) width, so I suspect you would be OK relative to baffle step. But if you shrink the overal volume of the cabinet, the cabinet tuning and bass response completely change. I think that is why SReten suggested you use a modeling program, so you can visualize the effects of the changes you are going to make. Again, I think if all other dimensions remain unchanged, and you make the cabinet shorter, you are losing bass because you are losing overall volume. A modeling program should show you the changes to the frequency response clearly. Just an opinion. Steve/bluewizard

23rd February 2009, 09:29 PM	#4
abefroeman diyAudio Member Join Date: Feb 2009	Internal volume will stay the same. basically i am removing the area of the floorstanding plan that is dedicated for filling with sand, and replacing it with a speaker stand.

24th February 2009, 07:25 AM	#6
BlueWizard diyAudio Member Join Date: Jun 2007	Peter, I have no problem bowing to superior knowledge, but could you explain how cabinet height effects Baffle Step. I always thought it was related specifically to baffle width in the area of the woofer. In reality he is not going to change the cabinets internal working volume, so why should the parameters or response of the cabinet change? I confess I'm no expert, but an expansion of your response would be helpful. Steve/bluewizard

24th February 2009, 09:22 AM	#7
breez diyAudio Member Join Date: Jul 2004 Location: Finland	Baffle height will change the radiation pattern in the vertical direction. Think about it, you could flip the speaker and now your height is the new width!

24th February 2009, 09:55 AM	#8
Stuey diyAudio Member Join Date: Mar 2006 Location: Perth, Western Australia	Isn't it simply because the driver radiates in a sphere (or half sphere, depending on frequency). Therefore, the height also makes a difference to that forward radiation. However, as most baffles are narrower than they are wide, the biggest effect is caused by differences in width, because this has the greatest effect on total baffle area per mm of change in dimension (width vs. height). I think, anyway... Stuey

24th February 2009, 08:00 PM	#9
abefroeman diyAudio Member Join Date: Feb 2009	where can I find a calculator for BSC?

24th February 2009, 08:15 PM	#10
smellygas diyAudio Member Join Date: May 2008	Doesn't the Allison Effect cause frequency response dips/peaks relative to the speaker height (as well as wall distance)? I would think that this should be taken into account as well. I guess you could also just measure the frequency response with varying cabinet heights to see if you need to change your BSC! SG

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