Connecting Multiple Different Subs

[vinceb]

Guys, I wonder if you would give me your advice on the best way to approach this dilemma, I have had my HE15 sub disconnected for awhile and would like to hook it back up with two sealed Avalanche 15 subs.

The HE15 is the PR box with two 18" PRs and is a dual voice coil ~4 ohm per coil, the Ava are 4 ohm single voice coil and there are two. I have a BFD I'm using to tame room modes, and the amp is a crown K2 so I was thinking of two options that have different compromises:

First and probably the best is to connect the HE15 coils in parallel on one amp channel and the Ava in parallel on the other. This would give the ability to turn each channel up or down but the amp would see a different load on each channel (maybe this is a non-issue for the amp?) and would let me address not over-driving the HE xmax since while it is two voice coils it is just one cone. I guess the setup would involve near-field measurement of each cone to balance the output. I think this is the way to go....

Second, wire one coil of the HE15 in parallel with one Ava on each amp channel, amp would see the same load but no way to balance the subs independently.

I'm doing this is mostly for the fun of it but the HE is just sitting there and it would be cool to do something with it. Also I need to move one of my subs because it may be adversely affecting my projector which blew a bulb recently and I can stack all the subs in the corner - I've found elevating subs can be very positive to room response it's just not easy to achieve. Three cones will move more air than two, and while the Ava may be a bit cleaner the HE goes lower so the merger of the two should be interesting.

Thanks for your thoughts!

[ThomasW]

Second, wire one coil of the HE15 in parallel with one Ava on each amp channel, amp would see the same load but no way to balance the subs independently.

Nope, not a good idea...

[vinceb]

Okay, thanks - do you have a comment on the first option?

[ThomasW]

Unless you buy another amp, #1 is your only option

[vinceb]

I will take it then that #1 is not too heinous an option. The crown was a somewhat affordable ebay purchase and will be my sub amp for life. One day I want to do an IB with something on the order of 4x18" or equivalent.

From a quick take last night this is working well. For safety I used a VOM and measured 2.0 ohms and 1.9 ohms on the leads at the amp. I have the HE15 turned down 4db compared to the AVAs and my eyeball-xmax test says the woofers are seeing about the same excursion. This will have to suffice until I can re-wire the BFD for stereo and take measurements, then do corrections to each channel independently. Probably the HE doesn't need the house curve that's dialed in for the AVA, will be interesting to see the response of each and the BFD settings.

My initial impression is that the HE has some seriously low output that I've been missing, which is part of the motivation of all this after all. IB one day but right now I'm making the most of what I've got. On the up side, the crown now sees two 2 ohm loads which should let it deliver max output, and I'm using all the cone area I can muster to best advantage.