It seems to be a curious bad idea, mechanically unimaginable (when actuated by a center coil).
The straight cone is the best shape for the lows, and the manufacturers are experts.
Last edited:
Using a relatively small driver to produce relatively large wavelengths is not good for dynamics, even if the nonlinear distortion isn't that bad.
The reason may have to do with an inability to couple with the air. Think of trying to row a boat with a pool cue as the paddle. You'd make a lot of heat and noise but not get much control of motion. Its physical efficiency that has a lotf to do with dynamics, but not electrical efficiency.
I'm having a hard time getting my head around #1. Isn't the basket isolated from the magnet? And I am not picturing the magnet itself being a good vibrating material. Can you feel, or measure this? Can you measure it separate from the noise that is being produced in a magnet/basket? EG, excite the magnet and see the effect on the basket, without any amplification going through the speaker system?
2) I at first thought you meant the edge of the mounting apparatus that the surround attaches to, that is bolted to the cabinet, but after a couple reads through I now think you are speaking of the edge of the cone that attaches to the surround. Would you clarify this?
It makes sense that a stiffer frame and lighter magnet reduces resonance. The whole unit (minus the moving mass) forms a "stator" with the cabinet. So stronger and thicker with less flexing is better. But the benefits would depend a lot on volume?
I've been using some hivi m8ns lately. Jon Marsh over at htguide.com is a big fan of these, called them "accuton on the cheap". They are a stiff piston cone with a huge high loss surround. They have a massive break up around 2000, but I use equalizer APO and kill the signal before the break up.
Seas excel magnesium drivers would probably be a step up in performance since they are much lighter, also accuton take the piston driver concept to the extreme, with a very stiff light one piece cone.
In an active set up you can get around massive cone break ups a lot easier.
Interesting that the KEF B110 was so popular with DIY'ers. It was filled from motor to surface with hard foam, did that help?
A small driver can delivers good lows if you put your ear at 5 cm at low levels.
Very short radiating large wavelengths (you can try it with headphones like the Shure K1000)
2) Yes, the edge of the cone at the surround.
1) The magnet is not isolated from the basket it is rigidly attached to it. This means that the magnet is hanging off of a steel structure. The mass and that structure will have a resonance, several actually, but the longitudinal one is driven by the force between the cone and the basket/magnet structure, hence it will be the most sensitive.
I have not measured this directly, but after seeing this problem - a slight dip in the response at about 600 Hz, in virtually e3very woofer that I looked at, I had to conclude that something in resonance was drawing off energy from the cone. The fact that it exists in both the 12" and 15" drivers that I used extensively - both having identical magnet and basket structures (the 12 being a little smaller) - led me to assume this mechanism. Then when the Neo version of the same driver did not have this problem, I was fairly comfortable with my assessment (albeit it could be wrong!)
I know that it seems unlikely that a stiff cast basket could resonant, but then remember how heavy the massive ceramic magnet is. All structures resonant, its just where. A cars body structure has a fundamental resonance around 30-40 Hz and we think of those as "stiff". 600 Hz is not so unreasonable for a magnet/basket assembly.
Yes, of course, it was a great design, but did not have great HF performance. The foam adds a lot of mass as well. We made passive radiators this way for some prototype subs that were made.
A small driver can delivers good lows if you put your ear at 5 cm at low levels.
Headphones can have good bass if they are sealed tight, because the volume is so small. The smaller the volume being excited the greater the SPL for a given volume displacement - PV=nRT holds in this region. Insert headphone can have great bass because they are almost connected directly to the eardrum - but they have to seal tight!
Ah, nomenclature! I was going with Italian basket, or, cone. I am reading you now.
Very short radiating large wavelengths occurs with the K1000... you must find a way to explain it IMHO.
Last edited:
Very short radiating large wavelengths occurs with the K1000... you must find a way to explain it IMHO.
I would explain it as that the smaller cone can produce better bass at lower volumes since less velocity is required, there could be other techniques being used, I know some phones have high impedance and maybe that accelerates the cone quicker as well?
I've heard decent bass on headphones, but nothing that I would call dynamic. It seems like forming a seal has something to do with it but I don't know why, possibly it creates a chamber that allows the cone to interact better with the air mass, maybe similar to the way a horn loading works.
There are some great charming small speakers out there, but I don't believe small speakers can ever really sound like big ones (horns, arrays, or stats) in terms of dynamics. Air is air, and the wave front is small. Maybe omnidirectionals.
Last edited:
Maybe, It was a long time ago and there was this KEF "units" collection. I was talking about the oval planar woofer. You are probably right the B110 was the mid and the T110 was the tweeter IIRC.