Double down, good or bad?


I came across this article on Atma Sphere's website:

http://www.atma-sphere.com/papers/myth.html

In short, Atma Sphere believes having a power amp that is capable of doubling its power when impedance is half is not necessarily a good thing because speakers in general do not have a flat impedance across all freq range.

On paper, it does make sense. Though I am sure speaker designers take that into consideration and reduce/increase output where necessary to achieve the flatest freq response, that explains why most of the speakers measured by Stereophile or other magazines have near flat responses.

But what if designer use tube amps to design his speakers, mating them with solid state should yield higher bass output in general? Vice versa, tube amps yield less bass output at home?

I have always been a tube guy and learned to live with less bass weight/impact in exchange of better midrange/top end. Will one be better off buying the same exact amp the speakers were "voiced" with, not that it will guarantee good sound, at least not to everyone's ear.
semi

Showing 4 responses by almarg

In the case of the B&W, the woofers are in parallel (4 ohms) and are 3 db less efficient than the 8 ohm midrange and tweeter; if a transistor amp is used it will have double the power into the 4 ohm portion of the impedance curve, thus driving the woofers with the 3 db extra needed for them to operate with the midrange and tweeter. The speaker cannot be driven properly by any amp that does not double power as impedance is halved.
Ralph, re "the speaker cannot be driven properly by any amp that does not double power as impedance is halved," you may recall that we discussed a similar point in another thread a couple of months ago. Wouldn't it be more correct to say that to be able to drive this impedance characteristic properly the amp has to have a low output impedance (relative to 4 ohms), and power capability into 4 ohms that is adequate to support the required volume? In other words, a solid state amp rated at say 200W into 8 ohms, but only 300W into 4 ohms, will do just as well with this speaker (IF all else is equal, and if the output impedance and 4 ohm output power criteria are met) as a solid state amp rated at 200W into 8 ohms and 400W into 4 ohms.

Regards,
-- Al
Ralph & Kirk,

I think that the confusion (or lack thereof) between power at the clipping point and output impedance comes down to what I said in my post dated 11/24. It is important to clearly maintain a distinction, in discussions such as we have in this thread, between doubling down of an amplifier's RATED power output into 4 ohms vs. 8 ohms (which is what this thread was originally about, and which amplifiers having very low output impedance may or may not be able to do), and the fact that ANY amplifier having very low output impedance WILL deliver double the power into a 4 ohm speaker impedance vs. an 8 ohm speaker impedance, provided that it is not driven to the point where its output is limited by clipping or other factors.

Best regards,
-- Al
What the Voltage Paradigm seeks to do is call an amplifier a 'voltage source' when it refers to an amplifier that makes constant voltage into any load (i.e. doubles its power as the load impedance is cut in half).
For the benefit of others who may read this, and along the lines of my earlier post in this thread, I think it is important to clarify here that "doubles its power as the load impedance is cut in half" in this context does NOT necessarily mean that the power RATING doubles as the load impedance is cut in half.

It means simply that a voltage paradigm amplifier, as a consequence of its very low output impedance, WILL deliver twice as much power into a 4 ohm load as into an 8 ohm load, provided that it is not called upon to deliver more power than it is capable of delivering (e.g., it reaches the clipping point). And that maximum power capability will in some cases correspond to significantly less than twice the number of watts at 4 ohms as at 8 ohms.

Regards,
-- Al