What does "impedance swamped" mean?

[beerrhino]

A few years ago I was looking for an attenuator and I was checking out the Weber Mass 150.  Unlike the other attenuators I had seen this one wasn't made for a specific impediance and it didn't have a selector switch, it just said "works with 4, 8 or 16 ohm cabinets".  I emailed Ted Weber to confirm this and he replied "the Weber Mass 150 is impedance swamped so it is safe to use with 4, 8 or 16 ohm loads".  He never replied when I asked him what impedance swamped meant.
I wound up buying it and it has worked without a problem for years so I'm not concerned but I have always wondered what impedance swamped meant.  Any help?

[Hemisaurus]

It's a new term to me, here's what googling got me.
My guess is the following explanation is correct (found on forums at freestompboxes.org):

"At different levels of attenuation, you will get different impedances depending on the ratio of the impedance of the attenuator in tandem with the impedance of the speaker plugged into it. This sort of attenuator will never give you an exact impedance match. They say that you can use it with 4, 8, or 16 ohm amps because most tube amps can tolerate impedance mismatches as long as they're not too far off. Using a 16 ohm speaker with the Mass Lite could potentially get you a range of impedances anywhere from 8 to 24 ohms, depending on the level of attenuation and the setting of the "Range" switch. This should be okay for a 16 ohm amp, but you have to be aware that mismatching the impedance will change the tone and response of the amp from its "normal" sound."

[beerrhino]

Thanks hemi, I googled it too but that explanation never came up in my searches.