[utahtaper]

I'm driving a pair of ADS L1290's with a Carver M500T. Carver is rated at 250w per channel at 8 ohms.
My speakers are 15 W minimum to 300 W maximum. They are 8 ohms with an efficiency of 90db spl from 2.8 vrms.
The speakers can be biamped and I thought about getting another M500T and bridging both amps to mono mode and running one to each speaker. Would I damage the speakers or amps by doing this? Would I gain anything from this? If not. Would it be more efficient to buy an amp that is rated at 300w per channel @8 ohms?
Or two monoblocks rated at 300w @8 ohms max each?

[lonewolfny42]

The speakers can be biamped and I thought about getting another M500T and bridging both amps to mono mode and running one to each speaker. Would I damage the speakers or amps by doing this?

No....but do you really need to bi-amp? How does it sound now?

Would I gain anything from this?

If you have a large room....and you play things very loud.

Would it be more efficient to buy an amp that is rated at 300w per channel @8 ohms?
Or two monoblocks rated at 300w @8 ohms max each?

Only if your not happy with what you have now.

[lonewolfny42]

Those 1290's are some vintage speakers....what kind of shape are they in ?

http://sportsbil.com/ads/l-1290-review.pdf

[utahtaper]

Those 1290's are some vintage speakers....what kind of shape are they in ?

http://sportsbil.com/ads/l-1290-review.pdf

They are in great shape! Sound awesome!

So essentially hooking up an amp of greater watts than what the speaker can handle won't damage the speaker? Or does it mean you can do it, but you have to watch how loud you turn it up to?

[srb]

So essentially hooking up an amp of greater watts than what the speaker can handle won't damage the speaker?

If the volume control is sensibly used, probably not.
 

Or does it mean you can do it, but you have to watch how loud you turn it up to?

Yes.
 
Most speakers are rated for how much continuous RMS power they need to (a) operate at a minimum and (b) can handle as a maxium, in your case, 15W - 300W.
 
If an amplifier is not powerful enough, and you overdrive it, that can result in a clipped waveform, similar to a square wave which contains an infinite number of odd harmonics (less so with tube amplifiers), and can damage speaker drivers, particularly tweeters.
 
But obviously a powerful amplifier might be capable of outputting more current than the voice coils of the speaker drivers can tolerate, and it is certainly possible to burn them out.  So you do have to be judicious in the application of power, and back off if distortion is present.
 
Because these wattages are continuous ratings, and music is anything but a constant signal amplitude, most drivers can tolerate higher wattage peaks associated with dynamics for a very short period of time (measured in milliseconds).
 
I certainly have used speakers rated at 75W maximum with 200W amplifiers, and they sounded great.  Yes, you should be careful in applying too much power and resultant volume than a speaker is capable of, but the beauty of having a powerful amplifier is that it can effortlessly reproduce quick demanding peaks without strain or waveform clipping, i.e. "headroom".
 
Steve

[ctviggen]

Unless you're using the speakers outside to blast music at a party, it would be highly unlikely you'd ever push them hard enough to hurt them.  At least I've never been able to do so (my ears will make me turn it down way before the speaker comes close to destruction. 

[gerald porzio]

Passive bi amping is of dubious benefit, IMO. Active is quite a different matter.

[JackD201]

Speakers face greater danger with too little watts (amp clips) than with more than the recommended rating. In the latter the speakers will get damaged playing louder than you can even stand or with silly accidents like yanking out an IC with the system on.

[JimJ]

Speakers face greater danger with too little watts (amp clips) than with more than the recommended rating. In the latter the speakers will get damaged playing louder than you can even stand or with silly accidents like yanking out an IC with the system on.

No speaker has ever been destroyed thermally by "too little" power.

In a clipping situation, the speaker might be receiving well over its recommended power.

[JackD201]

Semantics Jim J?

I see a tube in your avatar. I know you know that there is a big difference between the way a tube amp clips and the way a SS amp clips so I'll leave it at that.

[gitarretyp]

Having too much versus having too little power regarding damaging speakers is a more complicated topic than it first seems and anecdotal reports suggest. When you clip a normal solid state amp, two things happen: the waveform tends towards a square wave and the power output will be above the RMS rating of the amp. The squaring of the waveform will increase the amount of output into higher frequencies, which increases the likelihood of tweeter damage. That being said, if you're using a 10 W amp on speakers than can handle 100 W, there is virtually no chance of damaging the speakers. On the other hand, if you use a 500 W amp to drive 100 W rated speaker, there is a very real possibility of causing damage to the speaker.

[JLM]

Keep in mind too that doubling the power at best would only add 3 dB more sound (half again louder).  In your case with one amp handling the woofers, the additional sound pressure level (volume) might not even be noticable.  The main advantage of bi-amping is to synergize the drivers to the amps (typically solid state amplification with it's high damping factor to the woofers and smaller tube amplification to the midrange/tweeter).

(Note that some prefer tube sound.)

But honestly I'm not sure bi-amping $1300/pair, 25 year old speakers makes much sense (unless you have extra amps sitting around).

[utahtaper]

So how would you run this then? The speakers have two 8" woofers, one mid, and one tweet. If you biamp them(theres a switch in the back to put them in biamp mode), it splits one of the 8" woofer away from the other three speakers. Would you run one power amp to the L & R of just the subs alone and one power amp to the rest of the speakers? Or would you not biamp the speakers and just run each amp mono into each speaker?
What I'm thinking here is that I can squeeze a little more bass out of the speakers if I biamp them. ADS actually made an amp unit that plugged directly into the back of the speaker in biamp mode and powered just the one 8" on it's own. But those power supplies are tricky to find. I think they were called the PS-1?

[markC]

But honestly I'm not sure bi-amping $1300/pair, 25 year old speakers makes much sense (unless you have extra amps sitting around).


Got to agree with that statement.
Unless they're new old stock, they've got to be hurting to some degree.

[srb]

Everyone was referring here to standard passive biamplification, where a speaker has two pairs of speaker posts, one pair connected to the woofer section and one pair connected to the mid/tweeter section, normally connected together with a shorting strap or cable, which is removed for bi-wiring or passive biamplification.  When two amplifier channels are used in this situation, the passive internal crossover is still used, and each channel of amplifcation receives the full frequency spectrum signal and the internal crossover still splits the highs and lows as it normally would.  Because most of the amplifier power is used by the woofer and a much smaller amount by the mid/tweeter, that is why you received comments about dubious performance increases.
 
However, your ADS L1290 speakers are quite unique in that they have a switch to put them in an active biamplified mode, which actually disables the internal passive crossover between the woofer section (both woofers) and the mid/tweeter section.
 
Therefore you must use an electronic crossover, typically either the internal ADS PA1 Biamplifier (each containing two power amplifier channels and an electronic crossover and designed to fit into the rear recess of the speaker), or two standard external stereo power amplifiers connected to the ADS Biamplifier System Control electronic crossover.
 
It should be possible to use a non-ADS electronic crossover and match the 500Hz, 12dB/octave crossover design specification between the woofers and mid/tweeters, and experiment with adjusting the volume level between the two sections.
 
As far as being 25 year old speakers, I don't know.  They did use high quality drivers, and the cast frame woofers did have butyl rubber surrounds which are probably in good shape compared to 25 year old rotted foam surrounds.
 
Tough call, but if you did use an adjustable third-party electronic crossover, that piece and the pair of amplifiers could be used with a future pair of speakers, unlike the non-adjustable electronic crossover in the ADS components, which you probably couldn't locate anyway.
 
Steve
 
 

[utahtaper]

Thanks for the input guys.
Thanks for your knowledge on these speakers Steve. Very informative!

The speakers still sound super!
I'll have to keep my eyes peeled for the PA1 and electronic crossover and see if I can make it work in the future. I have a feeling they are going to be tricky but you never know. I found the old PB-1500 and C1500 for a really good deal here local. The amp in the PB1500 was broke but I was able to get it running replacing the PNP transiters. I could barely even find any info on that unit at all. I'm still looking for the schematics if anyone out there has them it would be much appreciated!