Alternative subwoofer & no more hum problem

[zinc]

This is my first time, so be gentle...

I have put together a resonable HT system, but have been missing a subwoofer, and funds are severely limited. However, I have two guitar amps siting around and decided to audition them for the part. When each was connected to the subwoofer out port of my receiver/amp, the main result was a loud hum. Thanks to some hints on this site and on a Yamaha site, I tried the three prong to two prong cheater adapter solution and it worked like a charm. Both amps work well now, although obviously the 300 watt amp is the preferred choice over the 15 watt cube amp (which still sounds not bad).

The question is, is there any problem anyone can see with this arrangement? WHat would be lost in doing this? Neither is a closed cabinet, but the sound output is not bad. Also, not being an actual powered subwoofer, it would seem to avoid the double filtering problem mentioned in the terrific Polk audio site (http://www.polkaudio.com/home/faqad/advice.php?article=bassmanage).

So, is there anything I should be concerned about?
Many thanks for the previous hints and for any help you can give now!

[This Guy]

Ok, since the guitar amp's speaker is in open air, has little cone excursion, and an fs of around 80 hertz it isn't gonna go very low. And it certainly won't handle that 300 watts in the bass frequencies. Find where the speaker starts to bottom out and never go that loud again. Just be careful because that speaker is not meant to handle the frequencies you're throwing at it.

-Joey

[zinc]

Thanks, Joey. Went away for a little while, so only had a chance to test your suggestion out yesterday. You are right -- the original tests I did on my new "subwoofer" involved mostly voicetracks, with only a little deeper frequencies. Yesterday, the DVD had a significant musical sound track and the amp/subwoofer was emitting a sort of popping sound in response to the driving bass line of the sound track -- probably the bottoming out to which you were referring. Did not sound healthy at all. So I have kept the volume below that, which loses a lot of "presence" but better than nothing.

Question: Do you think a bass guitar amp could handle the frequency range?

Thanks,
Z.

[This Guy]

It certainly would be better, but it still won't be quite up to par as a regular subwoofer. Bass amps tend to have their boxes tuned to around 60 hertz, so you get lots of sound at that frequency and up, but anything lower than that and it will bottom out like crazy and may ruin the speaker. It will be a decent temporary solution, but still save up for a good sub with a lot of excursion, decent power, and goes low.

-Joey

[zinc]

Thanks again. Sounds like a temporary solution, then, at best. While I have had the amps for a while, they are still used, so wouldn't want to blow the speakers.

Z.