Can I/Should I use my Outlaw Amp to Power A Subwoofer?

Was not certain where to post this and this seems to be the most popular Amp forum.

In my post Katrina set up I do not currently have a dedicated subwoofer. Just a 5.none system. My uni room apt is about 8-9000 cubic feet (much bigger than most dens). Rather than buying a sub or subs and spending lots of money, could I use or modify existing equipment with good results?

I have an unused pair of Klipsch LaScala speakers and I can have 2 - 4 available (unused) channels from my Outlaw 750 Amp (165W/ch, X 5 channels).

Qs:
1. I think 165 W is not powerful enough to run any of the new commercially available subs on the market. LaScala's are very efficient speakers though, but is 165 W enough to run it as a sub? New subs are powered by 350-500-1000 W amps. Can I safely bridge or combine 2 channels off the 750 Amp to create a 330W Amp? If it is safe to do this exactly how do I connect the channels and output to the LaScala sub?

2. Can a Klipsch LaScala be used as a sub if I directly wire into the woofer and bypass the crossover network? Would the old Klipsch 12" driver be ok, or would I need to replace it with a "modern" dedicated 12-15 or 18" subwoofer driver? Would such new drivers require at least 330 W? Mind you, opening up a LaScala might require major surgery. But to save megabucks, I would do it.

Any and all thoughts appreciated.

Brian
Tulane University
New Orleans


My rig:
26" 20 yr old Sony TV - even Katrina couldn't kill it!
Outlaw 990 pre/pro
Amps:
a. Outlaw 750 (165 W/ch x 5 channels) - but only 3 channels currently used, powers Klipsch Academy center channel speaker (c. 1992) and Klipsch Heresy's - surrounds c. 1980,
b. McIntosh MC-240, powers my Klipschorns c. 1980,
c. and an old stereo amp (2 channels work most days), which could be used for the Heresy's. (Thus I have 4 potential unused channels off the 750).
Klipsch LaScala speakers, currently not used, c. 1980.
Oppo 981 DVD
Old DVD player
Tascam tape decks and other donated tape decks
Old donated VCRs
Technics SL 1200 DJ type turntable with 2 different DJ cartridges (listening to Joao Gilberto Jazz records from 1963, with a 1965 tube amp, and 1980 king size speakers - priceless)

Hi br, nice stuff, k-horns ,lascala's and heresy's and a mcintosh amp. I don't know if bypassing the crossover would be worth it.good luck

Your room is certainly large - close to three times the volume of my den. That's going to be a challenge for any sub to really fill with low frequency sound. I have a few thoughts, but I'm going to approach them somewhat "backwards" from your original questions.

Could the LaScala's be modified to serve as "subwoofers"? Based on these specs , I doubt that they'd serve the job particularly well. The LaScala's have a -4dB point of 53Hz. As a comparison, Outlaw's smallest sub has a -2dB point of 28Hz (the -4dB point is probably close to 20Hz, or more than an octave below the LaScala). Your existing mains (the Klipschorns) actually go 20Hz lower , making the LaScala's pretty superfluous. I doubt that modifying it would gain you much - and certainly not enough to provide the Klipschorns any appreciable help.

You would need to look at the power requirements of any subwoofer that you would be driving from the Model 750. Also keep in mind that the 750's power output will increase with a lower-impedance speaker - and many passive subs are going to be a 4 ohm load. That being said, there are also very few commercially available subs that are actually passive subs. The subwoofer market is dominated by powered subs that rely on their own built-in amps. Also, I would not bridge the channels of a 750 because the amp wasn't designed for that.

Gonk,

I don't know how you do it. Lots of posts and replies, even on Thanksgiving. Like Craigsub at avsforum, you are awesome My posting at avsforum yielded similar private and posted replies as yours: the LaScala will not go that low. I suspect the specs given are using their crossover network. However, I would bypass it and directly wire the woofer if used as a sub for 5.1, vs my current 5.nothing. I am happy with the K horns for bass; although I never heard a sub with them. Others have said a sub, as part of a 5.1 etc system is important as some music recordings and most movies have a discreet x.1 channel. Thus the Khorns alone, they say, are not enough. A foray at some local stereo places in metro New Orleans (all 3 higher end places) seems to confirm this to my ears.

In part due to my large 17 x 40 x 13 foot uni-room (den, study, dining room, kitchen), I am also thinking about 2 subs. Part of the reason is to keep the weight below 100-150 lbs per sub. Even at these weights, shipping and schlepping could be a major problem.

As for the amp Q, I thank you for the advice. I will try calling both Klipsch and Outlaw support after the holiday (no luck earlier this week). I like the amp and do not wish to kill it.

BTW (of topic) - Customer support both on the forums and over the phone has been great. It makes it easy to recc a great product when the support is also great. Try telling that to the airlines, FEMA, etc.

It's not really major surgery to get to the woofer.
Tip the speaker on a side or on the back. Remove the 16 screws around the baseplate, remove the baseplate, and you can reach in and unbolt the woofer.

However, this is not likely to be productive in getting you the bass response you want.

Your biggest problem is trying to match the tone quality and sheer dynamic range of the Klipshorns. With efficiency of 104 dB at 1 watt input and a typical sub at about 91, you'd need forty times the power on a single subwoofer as you have on your mains (per channel) to match peak levels.

You have to decide how deep you want the bass response and how loud you want it to be at peak levels. THX spec is for 115 dB peak levels on the low frequency effects channel.

I don't know of a reasonable sub that could do it. I'm trying to fill a 4500 ft3 room and have decided that my LFM 1 Plus isn't quite at the level I want. A pair of LFM 1 EX ought to do the trick, though.

Steve

The crossover network in the speaker is focusing on the transitions between drivers (tweet/mid/woof), not on the roll-off at the bottom end. The bottom end is likely determined entirely by the interaction of driver and enclosure, and with the enclosure serving as a constant I doubt that treating the driver as a variable (changing it out for a different driver) will buy you more than a few Hz.

Purpose-built powered subs would likely be the best solution to achieving really strong deep bass in your room. The idea of going with two subs in such a large room is also probably going to be for the best. Depending on what music you listen to, the Horns may very well be doing all you need - I know that I felt much the same with my Paradigm Studio/60's when I ran them without a sub. Movies definitely can benefit from a sub, though, and for some music the sub can also help.