Sub Woofer hook up with McIntosh MC 501

I'm currently thinking about purchasing a pair of subwoofers and run in stereo. I own a pair of McIntosh MC-501 monoblocks. The Mac's have 8,4,and 2 ohm connections, I run my speakers on the 4ohm taps, can I run a powered sub off the 2ohm taps without doing any harm. I would very much appreciate some help with this issue. Thanks
Run RCA's to your subs, don't use speaker cables to them.
I already run xlr's to the input on the amp for the pre-amp you can only run one input line, the mac is switchable between xlr and rca this allows you to run only one input at a time.
Active subwoofers accept line-level inputs so you could run the connections from your preamp instead of your amps. If you insist on passive subs, you may need another amp just for them.

I have also heard of people running a sub off the speakers. I am not sure what that would do to the amplifier load however...not that 501s would really notice if the connection is in parallel but... Personally, I wouldn't go with this option.

If only one set of outputs at a time are valid with your preamp you could change your preamp, or get a Y-Cable that plugs into your preamp or get a custom Y cable (my friend had this option done so he could biamp with 2 amplifiers) if you using RCA's Monster makes a single solid 1 into 2 adpaters (audio advisor sells them) I use to use these so I could run my single sub output to two subs.

I would not try running both off your amp.. only bad things could happen..
Are you suggesting running a sub off the speakers will do damage? I don't understand where you are going with this.

Has anyone setup their sub to run from your speakers?
Yes Mitch, I think it "could" do damage in certain circumstances. It is all a matter of parallel or series circuits. In the former, you get a big drop in load impedance for the amp. In the latter, you get current sharing issues which can be quite complicated.

I forget where I read about doing it that way - I think it was a thread right here on Agon some time back. Maybe someone who has done it can chime in.
Mmitch: The speaker inputs on The sub are supposed to be used with a direct run from your amp and then run speaker cables from the sub to your speakers.. not two runs from the amplifier (which affects the load) But the first option will really affect sound quality on your main speakers.
I spoke with Albert Von Schweikert concerning this issue, since his VRS/1 subwoofer is the one I will connect to. He states the sub amp was designed to take a load from an amp as long as the connection is made to the high input on the back of the sub. He also states that his Von Schweikert circuits are designed to be compatible with one another, therefore they may be connected in either configuration.

Just quoting what the designer himself told me
All I'm saying is you shouldn't cause the Mcintosh to drive two output ohm taps. I know other amps would have problems.. The Autoformers on the Mcintosh can play low impedences but I'm not sure they will support playing 2 & 4ohm taps at the same time.. put both wires on the 4ohm tap and ground.

I would call Mcintosh.
Upon your advice, I have placed a call to Chuck Hinton at McIntosh. Thanks
Here is a possible solution
With a Vandersteen 2WQ you can safely take speaker
level out at the amp into the pair of 2WQs the reason is it has a safe 1/2 Mega ohm input Imp. You will also receive the benefits of
high Passing the main amps which will lower distortion
and dramatically clean up the clarity of your system and music.

I ran my Velodyne DD-15 from BAT-75SE power amp's speakers terminals, and the main speakers from the SAME amp terminals, using spades for one, and bananas for the other.
I don't think, you shoud use 4 ohms term. for the main speakers and 2 ohms for the subs.
Many people prefer speaker level signal to drive sub.
Spoke to Chuck Hinton at McIntosh, his feelings were it would probably be best not to run the sub and the mac together, although it may be possible depending on how they react to one another, it's not advisable. He did state that REL sub are setup to connect directly to an amp