Another word of caution against over-tightening of drive units.
Don't do it.
As mentioned earlier it alters the tone, but it does more than that, it alters the amount of resonance pumped into the baffle. Since the baffle due to the cutouts is normally the weakest part of the cabinet, you certainly don't want more resonances there.
With large drivers the issue becomes paramount.
Some, like Harbeth only recommend finger tight, and I tend to agree.
Over-tightening in my experience often results in an uptight and dynamically constrained sound.
For sure there are better ways of attaching drive units to the baffle, but they are all more time consuming and more expensive to implement than simple wood screws.
Here's what Siegfried Linkwitz had to say on the subject.
Mounting a driver to a baffle
'Typically a loudspeaker driver has screw holes in its basket for mounting it to a baffle. Usually a sealing gasket is placed between the driver basket rim and the baffle. The driver becomes in effect stiffly clamped to the baffle.
This method sets up a mechanically resonant structure which is formed by the compliance of the basket and the mass of the magnet...
A) Drivers with a stamped metal baskets are prone to exhibit a high Q resonance when tightly clamped to the baffle. The magnet moves relative to the voice coil at the resonance frequency. Energy is stored and also readily transmitted from the moving mass of the cone into the cabinet.
B) Soft mounting the driver basket to the baffle using rubber grommets reduces the resonance frequency. A 2nd order lowpass filter is formed that reduces the transmission of vibration energy from the moving cone to the baffle and cabinet. The resonance must occur below the operating range of the driver.
C) If the driver is mounted from the magnet and the basket rim touches the baffle only softly, then the magnet-basket resonance cannot occur and the transmission of vibration energy into the baffle is minimized. The basket-magnet resonance can be measured with an accelerometer that is mounted to the magnet.
The drive signal is optimally a shaped toneburst.
Its energy is concentrated in a narrow frequency band. When tuned to the right frequency a long decay tail becomes visible on an oscilloscope. Often the resonance can be seen as a small bump in the driver's impedance curve in the few hundred Hz range. It should not be confused with the higher frequency bump due to cone breakup.
An early example of a box loudspeaker where a KEF B110 midrange/woofer driver magnet is clamped to a support structure. The clamp can be tightened from the outside of the box. The basket rim is floating.
Often the effects due to driver mounting are deemed to be of secondary importance to the overall sound quality of a loudspeaker. They are usually costly to remedy. They cannot be ignored when the goal is to design a loudspeaker of the highest accuracy.
http://www.linkwitzlab.com/frontiers_2.htm#N
Don't do it.
As mentioned earlier it alters the tone, but it does more than that, it alters the amount of resonance pumped into the baffle. Since the baffle due to the cutouts is normally the weakest part of the cabinet, you certainly don't want more resonances there.
With large drivers the issue becomes paramount.
Some, like Harbeth only recommend finger tight, and I tend to agree.
Over-tightening in my experience often results in an uptight and dynamically constrained sound.
For sure there are better ways of attaching drive units to the baffle, but they are all more time consuming and more expensive to implement than simple wood screws.
Here's what Siegfried Linkwitz had to say on the subject.
Mounting a driver to a baffle
'Typically a loudspeaker driver has screw holes in its basket for mounting it to a baffle. Usually a sealing gasket is placed between the driver basket rim and the baffle. The driver becomes in effect stiffly clamped to the baffle.
This method sets up a mechanically resonant structure which is formed by the compliance of the basket and the mass of the magnet...
A) Drivers with a stamped metal baskets are prone to exhibit a high Q resonance when tightly clamped to the baffle. The magnet moves relative to the voice coil at the resonance frequency. Energy is stored and also readily transmitted from the moving mass of the cone into the cabinet.
B) Soft mounting the driver basket to the baffle using rubber grommets reduces the resonance frequency. A 2nd order lowpass filter is formed that reduces the transmission of vibration energy from the moving cone to the baffle and cabinet. The resonance must occur below the operating range of the driver.
C) If the driver is mounted from the magnet and the basket rim touches the baffle only softly, then the magnet-basket resonance cannot occur and the transmission of vibration energy into the baffle is minimized. The basket-magnet resonance can be measured with an accelerometer that is mounted to the magnet.
The drive signal is optimally a shaped toneburst.
Its energy is concentrated in a narrow frequency band. When tuned to the right frequency a long decay tail becomes visible on an oscilloscope. Often the resonance can be seen as a small bump in the driver's impedance curve in the few hundred Hz range. It should not be confused with the higher frequency bump due to cone breakup.
An early example of a box loudspeaker where a KEF B110 midrange/woofer driver magnet is clamped to a support structure. The clamp can be tightened from the outside of the box. The basket rim is floating.
Often the effects due to driver mounting are deemed to be of secondary importance to the overall sound quality of a loudspeaker. They are usually costly to remedy. They cannot be ignored when the goal is to design a loudspeaker of the highest accuracy.
http://www.linkwitzlab.com/frontiers_2.htm#N