TOPIC:

Hi all. Thought I knew a thing or two. Nope. I know nothing. Nada. 

Goal: to add a subwoofer to a system from before subwoofers were a thing.

My stuff:
Pre-amp: McIntosh C-30
Amplifier: McIntosh MC7300 (times 2) the plan; one amp like normal to the speakers, the other bridged mono/parallel to run the sub.
Main Speakers: McIntosh XR-7
Subwoofer: McIntosh HT-12 passive sub. Rated 4ohm

OK, ok, ok. I'm attempting something odd here and I know it. 

The pre-amp does NOT have LF sub outputs. 
The pre-amp has three outputs, MAIN and Speakers A & B.
I have MAIN going to Amp#1, then to the speakers like normal. 
I was planning on using Speaker A to Amp#2, then to the subwoofer.

Options: 
1, I've been offered a MiniDSP RevB to use. I think this goes in-between the Pre-Amp and the Amp. 
2, Up the street is a respectable speaker builder who said he can make me a crossover that I can install outside the sub box, or bring the sub in and he'll solder it in place internally (there is room, I checked).

To me, it makes sense to add "crossovers" to the pre-amped line, in between the pre-amp and the amp because why send an amplified signal to the sub and then filter it out. 

But…..

With a built in crossover, I don't have to worry about tech I don't understand and latency. Trying to fine dial in a MiniDSP sounds frightening to me. Excuse me while I head outside and yell up at some clouds. 

I'm back. Wait...Damned kids. Get off my lawn.

Where was I??

If I do the internal crossover, I'm locked into just one spot. Is it the correct spot? I dunno. 

If you need info about any of the pieces I mentioned, please visit the McIntosh Compendium. : www.mcintoshcompendium.com

Thanks. I appreciate those with knowledge greater than mine, sharing. 

Robert

 

Hi Robert,

I can provide further info - on XOs etc - but the first thing that hit me was your statement here:
Subwoofer: McIntosh HT-12 passive sub. Rated 4ohm

... coupled with this:
the plan; one amp like normal to the speakers, the other bridged mono/parallel to run the sub

You have a problem in that when you bridge an amp to double its power ... it becomes unable to drive 4 ohm spkrs.  So you need to use a different amp for your McIntosh HT-12 passive sub - one that can handle a 4 ohm load.

Or ... you buy a different sub!  The specs I found from a recent "For Sale" ad for an HT-12 said its frequ response was 29 to 500Hz; 29Hz is pretty woeful for a sub.  
(The specs for my 15" Dayton 'Ultimax' sub drivers say "Usable frequ range 20-500Hz.)
 

Think he's banned so may be a useless post.
Agree that 29 hz is woefully weak for a sub.  Mine are flat to like 14 Hz.

As to which approach, get the miniDSP.  From the McIntosh preamp, MAIN out to minidsp inputs 1 & 2.  Minidsp output 1 & 2 to amp driving speakers.  Minidsp output 3 to amp driving subwoofer.  Configure cross-overs, delays, etc. in the miniDSP.  This is how I do it in my 2 channel system.  I've also set up 4 configs in my miniDSP - 1 for 2.1 with subs EQ'ed, 2 is 1 + bass boost/house curve, 3 is 2.0 (no subs, but EQ bass of mains), 4 is 2.0 without EQ (speakers natural, since they'll play down (essentially flat) to 20 HZ or so in my room)

Hah - yes it seems he is!  I should've looked a bit more closely at his post.

(I wonder what you have to do ... to get banned!!??)

Flat to 14Hz - impressive!  

I agree - a miniDSP makes it simple to integrate a sub (preferably 2).  My setup was slightly more complex than yours - in that my 10x10HD was also providing the XOs for my 3-way active mains (as well as the 2 subs).
 

I wondered the same thing...didn't see anything obnoxious in his post. 

I have a pair of Rythmik E15HPs.  Great subs.

I was using a 10x10HD for awhile for both systems (HT & 2 channel).  Now I've got 2 Flex's - 1 for the HT (2 subs+Crowson Transducers) and 1 for the 2 Channel (2 subs).  Same subs for both systems, using LFE for HT and Line In for 2 channel.