Ok, what do you imagine the response would look like on the rear side of the box with one driver?
One driver in a small box? Back side response should be the same as the response on the front side, at least in the low bass. 6 dB down from MFG specs, because they assume radiation into the front hemisphere only.
Who else would it be for? 😉 To be honest I think you need to explain now why it wouldn't work, in case you think you already have......you haven't 🙂
You can't isolate the low frequency response, the whole idea is to get it flat across the audio band
Well, of course the idea is to get the whole audio band flat. Can you indulge me and just finish walking through the steps you started laying out?
Do you agree that the back side BASS response should be the same as that on the front side for a single woofer in a small box?
Do you agree that the back side BASS response should be the same as that on the front side for a single woofer in a small box?
Well, let's focus on the part of the response that is 6 dB down. That's the root of my question.
SO, if we add a 2nd identical woofer, and double the input power, will the very low frequency response everywhere in the room (ignoring modal and other reflection effects) be affected by WHERE we put that 2nd woofer? I get that the low bass will be louder, but I think it will be louder regardless of where we put that driver. In other words, it's not the BIPOLE arrangement (in the low bass) that mitigates the baffle step, it's the contribution of the 2nd driver, no matter where it's placed.
SO, if we add a 2nd identical woofer, and double the input power, will the very low frequency response everywhere in the room (ignoring modal and other reflection effects) be affected by WHERE we put that 2nd woofer? I get that the low bass will be louder, but I think it will be louder regardless of where we put that driver. In other words, it's not the BIPOLE arrangement (in the low bass) that mitigates the baffle step, it's the contribution of the 2nd driver, no matter where it's placed.
Using the word bipole is distracting, yes. That is a poor simplification and often used with multichannel surround speaker info, very much misleadingly.
Placing second woofer on side or backside doesn't mean anything down low, but at mentioned transition zone it starts to make difference, and this difference variates at different horizontal rotation angles.
When radiators are close to each other, the distance between them changes differently clockwise and counterclockwise. Thus, spl response at certain angle and frequency is different.
I don't know any specific bipole simulator, but propably Xsim-3D and Vituixcad can dot that. The Edge is 2-dimensional, but it has dipole option. Dipole is pretty much like bipole, the difference is that at low frequencies there is cancellation instead of summation. But the transition effects are similar. Look at this example with wall simulating second "pole".
With Edge you can study off-axis response by moving the mic symbol sideways! You can simulate side-mount woofer by placing the driver offset from midline.
A quick demo with Edge. Offset dipole radiator, on-axis and left-right
Placing second woofer on side or backside doesn't mean anything down low, but at mentioned transition zone it starts to make difference, and this difference variates at different horizontal rotation angles.
When radiators are close to each other, the distance between them changes differently clockwise and counterclockwise. Thus, spl response at certain angle and frequency is different.
I don't know any specific bipole simulator, but propably Xsim-3D and Vituixcad can dot that. The Edge is 2-dimensional, but it has dipole option. Dipole is pretty much like bipole, the difference is that at low frequencies there is cancellation instead of summation. But the transition effects are similar. Look at this example with wall simulating second "pole".
With Edge you can study off-axis response by moving the mic symbol sideways! You can simulate side-mount woofer by placing the driver offset from midline.
A quick demo with Edge. Offset dipole radiator, on-axis and left-right
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Great, thank you! That was my expectation. It just took a while to communicate it.
Good to know. For this particular exercise, I'm just trying to imagine the packaging requirements of a couple of small woofers in a very small box.
Thanks again!
As the response in the low frequencies to the front reduces so it increases to the rear, if you now add a woofer to the rear it's response does the same and effectively replaces what has been lost from the front, as was mentioned it's quite an elegant way to do it due to the slope. If you are only interested in what is 6dB down then, yes, it makes no difference, use filters, to get it flat, so what is this thread about??😀
OK, bear with me. What happens to the low frequency response if we place that 2nd woofer on the front instead of the rear; i.e., two woofers on the front of the box? Is the low frequency response different than it would be with a bipole woofer configuration?
jimmy, what size of speaker are yoou planning? Please give dimensions and driver diameters so I can do some simulations. My previous example simulates a largish floorstand with 8" woofer. With smaller dimensions clean summation will go higher than 200Hz.
So, basically, you shouldn't put the other bass driver on other side in a two-way design!
So, basically, you shouldn't put the other bass driver on other side in a two-way design!
The low frequency reponse will be the same. The difference is the content that is above the baffle step will also be louder if the 2nd woofer is on the front, yielding a non-flat frequency response, whereas if the 2nd woofer is on the rear, you effectively cancel out the content the 2nd woofer provides that is above the baffle step (assuming no room reflections).
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Understood, but only if the crossover is above the baffle step frequency. If it's well below that frequency, then no such content exists.
My apologies for not being as clear as I could have been. I was trying to be very succinct and got myself in trouble by leaving out some application-specific detail. This might have been a better question for the subwoofer forum. I appreciate everyone's patience and help!
Hehe, I have my suspicions 🙂 That's probably going to be below the transition, so you could put it in the next room and it wouldn't make much difference 😉
People can only respond to what you post, now there's a crossover, or is it just a low pass filter on one of the woofers? Perhaps set out exactly what you want to do, and then the options can be discussed.
It's not necessary, I was only interested in the low-frequency behavior (which was somewhat alluded to in my original post, but obviously wasn't super clear). Again, thanks for all the help.
Ok, but as I hope you now see it isn't just what's below the transition, it's the whole zone that's important and bipole works and can be a good way of compensating