Improving speaker efficiency??

[mitchyz250f]

What can be done to improve speaker efficiency besides porting? Stacking magnets, switchng surrounds....?

[AndrewT]

Hi,
none of those are able to improve efficiency.
Well, stacking magnets may increase the B of the BL product slightly. This in turn will very slightly increase efficiency, but I suspect it will be hardly noticeable.

Horn loading should improve efficiency significantly.

[Eva]

Placing two drivers together improves LF efficiency by 3dB. Total boost is 6dB if they are wired in parallel.

Horn loading allows to get 104dB/W to 108dB/W from cone drivers provided that size is not a problem.

[mitchyz250f]

Just a noob trying to learn but it would that if you reduce the resistance to movement (suspension) and increase the electromotive force (magnets) that there would be some increase in in sensitivity. There is a guy called 'clipped' on this formum that modifies speakers to improve their sensitivity for car audio SPL competition.

Why are some speakers more sensitive than others, sometimes much so.

[Magura]

Originally posted by AndrewT

Well, stacking magnets may increase the B of the BL product slightly. This in turn will very slightly increase efficiency, but I suspect it will be hardly noticeable.

It depends how many tesla you add. I just tripled the magnet power on my FE166e's, sure that made a noticeable difference.

Just keep in mind, that magnets are not exactly free. I added magnets for the same amount of cash, as I paid for the units.


Magura

[Tubamark]

Originally posted by mitchyz250f
Just a noob trying to learn but it would that if you reduce the resistance to movement (suspension) and increase the electromotive force (magnets) that there would be some increase in in sensitivity. There is a guy called 'clipped' on this formum that modifies speakers to improve their sensitivity for car audio SPL competition.

Why are some speakers more sensitive than others, sometimes much so.

See:
http://ldsg.snippets.org/appdx-a.php#HOFFMAN

"Low-frequency capability, box size, and efficiency form the three key aspects of system design. To increase any of the three, you have to give up something from the other two, with box size being the most sensitive. The often unpopular bottom line is therefore to plan on using the largest box you can comfortably live with. This partially explains the popularity of subwoofers, which can be both large and hidden from view, and often include their own built-in high power amplifier. "

No free lunch. If you look at all the efficient pro sound drivers compared to the same diameter "home" drivers, you'll nearly aways notice that the prosound ones have traded Fs (bass extention) for efficiency. Autosound drivers often trade efficiency for a smaller Vas (ie smaller box.)

So far as I know, Hoffman's law has never been broken.

--Hope this helps
--Mark

[Jack Hidley]

When I was 14, I purchased some 15" woofers with very stiff W roll paper surrounds. I mounted them in 5cu ft boxes. They played quite loud, but didn't have much bass extension. In retrospect, fs was probably 60Hz or so.

I had the drivers reconed by a reconing shop with new surrounds that had a much softer treated cloth surround. My assumption was that if the cone could move easier, it would produce more bass. When I got them back, I installed them back into the cabinets, fired up the system and was shocked to find that there was less bass than before!!!!

Thus began my search for some scientific method to loudspeaker behavior. Do a search on Wikipedia for Thiele Small parameters. Go get whatever loudspeaker design book that Radio Shack currently sells. That will be very basic. After reading that, buy a copy of the LDC (Loudspeaker Design Cookbook). That book will be much more challenging.

[mitchyz250f]

I can give up low end extension, a lot of it. The speakers I will be using for my midbass (Peerless SLS10) are 3db down @ 50hz. I can afford to be down 3 db @ 90hz. So what can I do to improve efficiency?

[Jack Hidley]

You can either increase the radiation resistance on the driver (put it in a horn, or use multiple drivers), decrease the moving mass or increase the motor force (BL). Since the driver is already assembled, you can't do option two. You can't really do option three either since the voice coil geometry is already fixed. You might be able to get a small increase (1dB) in sensitivity if you add bucking magnets to the back of the driver. Whether this works will depend on the how close to saturation various locations in the motor already are and what the stray field looks like.

The easiest solution is to get a second driver and wire them in parallel. Even with some small series resistance added, you will still have higher sensitivity.