Well first off do you know what gage the old speaker wire is????
Did the old speakers sound good with the old speaker wire??
Just a wild guess but I think the problem is with the new speakers not thw wire.
But if you want to get new wire just go to Home Depo and get some 16ga lamp cord. Or if you want to spend a little more they have some nice 16ga "speaker wire". John
I have an old Dennon ($1100 in 1990) system for my bedroom and a visitor blew out one of the speakers. I plan to replace the whole system eventually, but not right now.
I replaced the speakers with some Jensen C220 Champion Series 2-Way Bookshelf Speakers with 6.5" Woofers for less than $50 for the pair.
I was disappointed in the sound quality and realized that the speaker wires are cheap (came with the original system) and are from 1990. I thought I might improve the sound a bit with better speaker wires --but what to get?
The Dennon Audio system D-200 is amp gives out 40 watts per channel.min.RMS, at 8 ohms from 20 HZ-20kHZ with no more than 0.5% T.H.D. The system otherwise works pretty well, CD changer and Tuner being the items I use the most.
You just wrap bare wire around posts at the amp end and stick bare wire into a slot that then clamps down at the other end.
I have experienced major imporvements on my main stereo system in my living room with good wires.
I know that Monster cables are a ripoff in terms of price.
I plan to use the system for another year at least as I have other things I want to buy in the meantime. And I listen to it all the time.
Anyone have any suggestions?
I don't want to spend much as I see this as a temporary fix--there are other problems with system and it will go completely I am sure in a few months.
Any suggestions as to speakers?

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