Why not horns?

Weseixas- You have been told repeatedly and politely that you and your friend, IMO, don't know what you are talking about. The JBL L-300 Summit loudspeaker I referenced above crosses from a 15 inch woofer to a horn at 800 HZ. The L-200 does the same at 1200 HZ. If you check another source besides your trusty IMO, you will find numerous examples from other esteemed manufacturers. When you are in this deep, it is usually best to stop digging.

Weseixas, down at 400 Hz, a 15" woofer has a radiation pattern that's approximately 150 degrees wide.

As far as coloration goes, the larger the cone the more difficult it is to get it to behave well. But as long as the behavior isn't too bad, it's possible to correct it or compensate for it in the crossover. On the other hand the smaller the cone the more excursion is required and (in general) the more the voice coil heats up, and therefore the more coloration we get from the motor going non-linear and/or from thermal compression. These types of coloration cannot be corrected in the crossover.

You mentioned coloration from the backwave energy of a large cone. For a given SPL, a large cone and a small cone are moving essentially the same amount of air, so we have the same amount of backwave energy to deal with. A large cone has more area for reflected backwave energy to strike and re-radiate through, but it usually has a larger box which can make better use of damping material to attenuate that backwave energy. I can offer up a link to anecdotal evidence that a good large cone can be low enough in coloration to compete with a good planar.

The main reason I like large cones has to do with radiation pattern control, another topic for another thread.

Having worked with cones large and small for many years (started as an amateur in 1979, turned pro in 2005), in my opinion a good large cone usually has greater performance potential than a good small cone - BUT it is usually a lot harder to work with.

Duke

Hello Duke ,

Thanks for the response and i'm sure a polar plot on that 15 inch woofer will prove what we are discussing. The published data including the response curve on both drivers will require eq-ing IMO for that speaker to be listenable, well unless it is being used for Sound reinforcement.

I could not find any data on the horn driver with that Horn type that is being used. The horn is beautifully made and the type of wood being used , from experience offers decent damping off setting the natural ringing of the driver in the 5 K range as confirmed by it's impedance curve.

A pity they never published the phase response , the woofer
also shows appreciable breakup.

All in all actually pretty decent driver Specs on the horn and below such on the woofer. I would work with the horn driver , but get a much better woofer for the application as this one appears better for sound reinforcement and since this is for domestic use the super high power handling is not a concern.......

Macrojack,

Hello to you 2 sir and many happies, get well soon ....

Hi Weseixas,

"The published data including the response curve on both drivers will require eq-ing IMO for that speaker to be listenable..."

Quite right you are! Aggressive equalization is virtually always required with such systems, and it's the crossover designer's job to do it. The published curves for the drivers only indicate how they start out, not how they end up. If you were evaluating the system based on how the individual driver curves start out (which makes perfect sense until someone tells you otherwise), no wonder you were skeptical! The published "before crossover/EQ" curves for the drivers I use look pretty awful at first glance, and the curves I actually measure before starting on the crossover are even worse.

The most useful curve for evaluating a compression driver is the "plane wave tube" curve, which is supplied by some manufacturers. Ideally, this curve slopes down uniformly without significant peaks or dips. Any curve measured on a horn has that horn's characteristics superimposed on the compression driver's output, which complicates any attempt to evaluate the driver.

All this talk is passing over my head at this point but I found a specification page for my woofer that may provide some clarification or narrow the discussion.

http://www.rcf.it/products/precision-transducers/low-frequency-transducers/l15p530

Is there anything useful in there?

Bill suggested I replace my native JBL LE 15B woofers with these because they are lighter, faster and more efficient.