Hello,
Is there a rule of thumb minimum distance (ratio of cone size) between the front and rear cabinet walls please. I am a novice cabinet designer and have just about got a grip on most of the params and in's n out's of sealed and ported boxes. But in all my research i have not found any guideline for minimum practical distance behind the driver.
Just looking at the situation i have the gut feeling that a system with the rear wall 1mm behind the magnet might not perform as well as a system that has more space behind the driver.
Many thanks in advance
Is there a rule of thumb minimum distance (ratio of cone size) between the front and rear cabinet walls please. I am a novice cabinet designer and have just about got a grip on most of the params and in's n out's of sealed and ported boxes. But in all my research i have not found any guideline for minimum practical distance behind the driver.
Just looking at the situation i have the gut feeling that a system with the rear wall 1mm behind the magnet might not perform as well as a system that has more space behind the driver.
Many thanks in advance
Golden ratio is not the way, it can work, but it's not always the case and i would not consider this for acoustic reasons.
But the general philosophy behind it, no sides are equal or multiples of the other is true and important to avoid strong resonances in the box.
And to answer the OP question, best is to leave much more space and line the backwall to avoid reflections trough the membrane of the driver. I try to keep at least the same space behind the driver as the depth of the driver. That is not with all designs possible, but when it is it's a good guideline
And also keep in mind, a lot of drivers have vent holes in the magnet that can not be blocked. I would keep at least a few cm of free space behind it (so not counting the lining in those space).
But the general philosophy behind it, no sides are equal or multiples of the other is true and important to avoid strong resonances in the box.
And to answer the OP question, best is to leave much more space and line the backwall to avoid reflections trough the membrane of the driver. I try to keep at least the same space behind the driver as the depth of the driver. That is not with all designs possible, but when it is it's a good guideline
And also keep in mind, a lot of drivers have vent holes in the magnet that can not be blocked. I would keep at least a few cm of free space behind it (so not counting the lining in those space).
The driver might have one or more holes in the magnet for better voice coil cooling. Leave at least some space for the cooling effect.
It might be advantageous to keep the depth minimum in some situations such as better coupling to a wall if it is a wall mount speaker. Or, depending on the woofer passpand you might be able to push the reflection from backwall above the passband. Some beefy pro drivers have such a big magnets it already functions as a back wall to the membrane etc. All in all, just make you speaker look good and fit its purpose. If not happy, you might be able to identify the problems you are hearing. If some of them are due to box you could make some prototype boxes weed them out. Have fun! 🙂
It might be advantageous to keep the depth minimum in some situations such as better coupling to a wall if it is a wall mount speaker. Or, depending on the woofer passpand you might be able to push the reflection from backwall above the passband. Some beefy pro drivers have such a big magnets it already functions as a back wall to the membrane etc. All in all, just make you speaker look good and fit its purpose. If not happy, you might be able to identify the problems you are hearing. If some of them are due to box you could make some prototype boxes weed them out. Have fun! 🙂
FWIW, Altec told me to allow at least 1.5x driver depth for rear exhaust in a sealed alignment and regardless of whether front or rear exhausted in a vented alignment.
GM
GM
I would have thought the shortest distance to the back wall as possible so the phase shift of the sound wave between driver cone-backwall-driver cone is minimal.
Obviously leave a gap for cooling.
Then make other two sides none factors/multiples of each other.
Obviously leave a gap for cooling.
Then make other two sides none factors/multiples of each other.
Hmm, first time I can recall anyone commenting on my periodically repeated post, so to be more clear 😉, the 1.5x dim is from the baffle mounting plane to any parallel wall, so minimum sealed internal dims would be 3x depth in width, height, 1.5x depth as a R-O-T against excessive VC long term heat buildup.
This of course pertains to high power apps from back when it was 100 - 150 W, so fine for typical HIFI/HT apps, but with today's mega power systems, no clue or even if they care now that adhesives have such high temp points, DSP to shape seriously distorted frequency responses due to thermal power compression.
GM
This of course pertains to high power apps from back when it was 100 - 150 W, so fine for typical HIFI/HT apps, but with today's mega power systems, no clue or even if they care now that adhesives have such high temp points, DSP to shape seriously distorted frequency responses due to thermal power compression.
GM