[Brax]

I plan to convert my RM30s to the Series II configuration.

The first step was to replace the woofers with new 40oz Mega Woofers and that is complete.

Now here's where I have a few questions. In the second step I need to pull the existing PRs and plug the holes. I thought there may be an advantage to pulling the PRs but instead of plugging those holes, rework the base by closing the front off and sealing it to the bottom of the speaker to take advantage of the extra internal volume for the speaker. Can any comment on if they they thing this would improve the bass and was worth doing?

The second idea is to use the existing 10" driver for the PR. To accomplish this I will need to remove the motor, which I'm expecting I will need to saw off since the mounting screws are more than likely under the spider. I think this would be a good use of this driver since no one is finding drop in PRs. I don't think this driver is the same one used in the RM40 so I don't think there is a used market for them either.

Other than those two items, I will be following the directions listed in the sticky section of the forum. This will happen once the weather the in Wisconsin gets a little warmer so I can work on this my garage. Just looking for feedback on the two non standard changes I was planning to make.

[DFaulds]

I'm just guessing here, but I would be surprised if the magnet on the 10" is screwed onto the basket.  Besides commercial drivers that often require in field repair and very high end home woofers, the magnets are usually glued on with a high grade adhesive.  I’ve removed magnets from woofers in the past by brute force, but that can be problematic.

As long as there is no signal applied to the woofer, I’m pretty sure it will act as a passive radiator.  I would suggest posting this on the Parts Express forum where I’m sure you’ll get some very good advice.

[HAL]

You can use a regular driver as a passive radiator, but the mass of the cone will be heavier due to the voice coil and have a different resonance frequency even for the exact same cone.  If you have the mass and surround damping of the original passive radiator driver, you can use that as a guide.

If you do use a driver, you can wire a variable resistor in parallel to the voice coil.  It will act as variable damping that can be controlled by varying the resistance.   A bit of Q adjustment for the total box system.

The putty on the original cone adjusts the driver Fs frequency.  Similar to the way Theil-Small parameters for a driver are measured by using the added mass technique.

You will probably find it much easier to understand by using something like Room EQ Wizard to do near field measurements of the woofer system to see what might be change.  Works well for acoustic measurements for the 200Hz and below range.  The Dayton Audio UMM-6 calibrated mic works well with the software.

Good luck.

[Stimpy]

If you do use a driver, you can wire a variable resistor in parallel to the voice coil.  It will act as variable damping that can be controlled by varying the resistance.   A bit of Q adjustment for the total box system.

I've heard of this too.  Just use a standard woofer, with no amplifier connection to the voice-coil.  Then use a pot, wired to the woofer, to vary damping.  And if my memory serves me correctly, I believe Richard Vandersteen used to do this with his designs.  Maybe an early version of the Model 2?  Could still use this method, as far as I know?  I'm not sure?  Worth a shot, as it keeps a good woofer intact, and doesn't cost anything!   

Good luck!

[HAL]

If you want to make it totally passive with no damping, just put a switch in line with the pot wiring to turn it on or off.