Bi-amping: How to using cheap t-amps?

January 27, 2008 10:16 AM

Bi-amping two cheap Sonic Impact T-amps — is it worth it?

I've got two of the notorious Sonic Impact T-amp amplifiers on order. I'm not into audiophilia at all (which is why I'm asking this question here rather than on an audiophile forum). But I really want a clean and distinct sound, and my current amp isn't providing it. I listen to mostly classical and am mostly penniless.

I have Wharfedale Diamond 9.1 speakers, that have bi-wire connections on the back, and my plan is to simply use two line outputs from my CD player for each amp. Wiring from amp then goes to either the low or high posts of the speakers (amp 1 = high inputs, amp 2 = low inputs).

I don't intend to use a preamp because they're too expensive. I'll just adjust the volume of each amp in unison.

Will this work? Is it wise?

posted by humblepigeon to sports, hobbies, & recreation (14 comments total)

Oh, and please keep replies simple. There are lots of bi-amping explanations out there that lose me after the first few paragraphs.
posted by humblepigeon at 10:20 AM on January 27

I suspect you would be better off using off like this:
Amp 1 => Speaker 1 (high & low)
Amp 2 => speaker 2 (high & low)
posted by kickingtheground at 10:33 AM on January 27

I'm not anticipating loudness being an issue. I listen to classical music at moderate volume in a relatively small room. All reports on the SI t-amps say that they're fine for this kind of setup.
posted by humblepigeon at 10:42 AM on January 27

I'm not sure you'll hear an appreciable difference moving from normal wiring w/jumpers to what you're proposing. Having said that, I'm sure what you've described will work fine. Not having a preamp in the mix could arguably make more of a difference than bi-wiring or bi-amping, though you don't say what you currently have for equipment besides the Wharfedales... good luck.
posted by bakertim at 10:50 AM on January 27

It should work but you've got a problem. With bi-amping there is a crossover somewhere earlier in the system so you get around needing a crossover in the speakers themselves. The crossover splits the signal to send highs to the tweeters and lows to the woofers. In the case of a bi-amp system the split signal is sent to separate amps which drive the woofers and tweeters separately.

You'll be sending full-range to your tweeters and your woofers. The woofers isn't really a problem; they simply cannot reproduce frequencies above a certain point (dependent on the driver specifics). But the tweeters don't do so well with full-range because it's usually too much power for them and tweeters are pretty easy to blow. This gets even worse if you ever clip the amps because that produces a lot of high energy high frequency content.

Now it's possible that the high input of your speaker still uses it's internal crossover to limit the power but you'd have to check the manual or open them up to have a look. If this is not the case then you ought to put a crossover somewhere, or even just a simple high pass filter on the tweeter side. You can actually build a high pass filter yourself quite cheaply, but you'll need to do a bit of math and find specs on the speakers saying where the crossover point is. The crossover could either go between the amp and tweeter or between the CD line out and the amp on the tweeter side.
posted by 6550 at 12:00 PM on January 27

Bi-wirable consumer speakers will still have cross-over filters preceding the drivers when bi-wired. What 6550 (correctly) points out above is basically irrelevent to you.
posted by kickingtheground at 12:36 PM on January 27

The instructions say: "By connecting each loudspeaker drive unit to its own dedicated amplifier the advantages of by-wiring can be extended. If you have two identical stereo power amplifiers, your speakers may be bi-amplified. For further details please consult your dealer."
posted by humblepigeon at 12:45 PM on January 27

See how it sounds first with just one of them. (*)

I have a Panasonic receiver with one of those T-Type amps in it, and I am blown away by how good it sounds. Completely flat response all the way across the audio spectrum. I'm hearing stuff I've NEVER heard before. And I'm not a nut.

*- Does the CD player actually have two identical outputs? Because I *think* if you are just splitting one output to the two amps, you'll be amplifying half the signal twice as much, meaning a net loss in quality.

** - I also believe that bi-amping is only really beneficial with older analog amplifiers. The idea being that an amplifier that's "busy" pumping out the bass it will be distorting the high end. So one amp works on one end, the other on the other.

***- Or it's complete audiophile hokum.
posted by gjc at 4:08 PM on January 27

- I also believe that bi-amping is only really beneficial with older analog amplifiers.

Nope, it works with everyting. The idea is that if the signal is very treble heavy, the amp will be working to hand that load. You then get a sharp bass transient, and the amp has to try and handle that.

Note that to do bi- or tri- amping correctly, the signal needs to be split *before* the amplification stage. Otherwise, you're just doubling the power into the speaker.

CRITICAL: If you load many tweeter drivers with a low frequency signal, they will die. Period. As kickingtheground notes, consumer speakers put in filters because of this, but if you aren't sure that the filter is there, do NOT load a full frequency signal into the treble side of a bi-amp speaker cabinet.
posted by eriko at 5:56 PM on January 27

If you need something to split the signal (the highs and lows) Make has one.
posted by ooklala at 6:55 PM on January 27

It will work. Try it. To get more oomph you might rather put a more powerful, yet less sonically beautiful, amp on the bass and a T-amp on the treble. T-amps are pretty incredible for the price and they are fun to play with, and did I mention that the price is cheap. Experimentation is part of the fun. Let your own ears decide. to a degree they are giant killers, but there are a lot of giants that can kill them too. That should not diminish the fun of experimentation and the satisfaction with a pretty high quality sound for the price of a case of good beer.
posted by caddis at 7:03 PM on January 27

- I also believe that bi-amping is only really beneficial with older analog amplifiers.

Active crossovers sound better and are much more efficient than passive crossovers.

The one pair of speakers I have that can be biamped sound MUCH better when I do so.

...but they're 1200 watt professional sound reinforcement cabs.
posted by flaterik at 8:01 PM on January 27

"Nope, it works with everything."

Even a type-t digital amp that's not (supposed to be) susceptible to those types of sound coloring problems?
posted by gjc at 6:33 PM on January 28

yes
posted by caddis at 7:22 PM on January 28