I am looking to test out drivers in the 5.25"-7" size class that use an inverted surround. The only drivers I am aware of are the Audax HM130C0/HM170C0.
Can anyone suggest others?
The next best thing would be a flat surround. For example there is the 6.5" Audax PR170M0 and the recent SB Audience Nero-6MRN150D 6" Midrange. Anything else like these out there?
Can anyone suggest others?
The next best thing would be a flat surround. For example there is the 6.5" Audax PR170M0 and the recent SB Audience Nero-6MRN150D 6" Midrange. Anything else like these out there?
Flat surround and shallow expo cone profile
PHL...?
I have attached a PDF of the PHL 1120 (8 Ohm) and 1130 (16 Ohm) the drivers have average measurements on paper (http://lsv-achenbach.de/images/lautsprecher/test/KT_Test_phl-E17-1120.jpg) but sound superb, so I personally would be very interested in your opinion of subjective Vs objective tests.
I have used the 1130 and love it... Its a high sensitivity Pro driver with super high ratio Bl 12.7 to 8.2g Mms combined with high power handling / very high SPL capabilities... Around 113 dB at 1 meter continuous AES 119dB peaks!!
So when used at typical domestic SPL's the driver is well within its limits and produces the most natural and detailed sounds between 400Hz and around 2 KHz when used with a good active / DSP crossover.
PHL...?
I have attached a PDF of the PHL 1120 (8 Ohm) and 1130 (16 Ohm) the drivers have average measurements on paper (http://lsv-achenbach.de/images/lautsprecher/test/KT_Test_phl-E17-1120.jpg) but sound superb, so I personally would be very interested in your opinion of subjective Vs objective tests.
I have used the 1130 and love it... Its a high sensitivity Pro driver with super high ratio Bl 12.7 to 8.2g Mms combined with high power handling / very high SPL capabilities... Around 113 dB at 1 meter continuous AES 119dB peaks!!
So when used at typical domestic SPL's the driver is well within its limits and produces the most natural and detailed sounds between 400Hz and around 2 KHz when used with a good active / DSP crossover.
Thanks for mentioning the PHL 1120 and the link to measurements. Breakup happening at a higher frequency than Audax PR170M0. Not inverted surround but at least flat. Looks good! Not easy to get in my country. I would have to order it from France at TleHP. Logistically that is probably not a good idea in these times.
Technically yes, but usually a 6-7" prosound driver has a ginormous magnet and teeny tiny basket windows, and that is not producing a good result in my particular application. But I am open to any and all suggestions.
Following up with a bit more detail. I recently purchased and tested a Faital Pro 5PR160, which has an accordion surround. The response (nude) is attached. The problem is with the large peak just above 1kHz. For smaller drivers this is often even higher Q that what you see in the measurements, which makes it a challenge to EQ out.
Almost every driver I have measured in the 5-7" size has some variety of response feature like this, when "in the nude" except these Audax models that have an inverted surround (HM130C0 and HM170C0). So I am trying to see if the surround is the root cause of the issue by finding more inverted surround drivers.
If I could take a driver and magically invert its surround that would make for a great A/B test, but I do not think that is possible!
Almost every driver I have measured in the 5-7" size has some variety of response feature like this, when "in the nude" except these Audax models that have an inverted surround (HM130C0 and HM170C0). So I am trying to see if the surround is the root cause of the issue by finding more inverted surround drivers.
If I could take a driver and magically invert its surround that would make for a great A/B test, but I do not think that is possible!
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So you think the surround is causing a resonance giving you that 1khz peak? Or am I misunderstanding you? But 1 kHz corresponds to about 34cm, so not sure that fits?
Anyways, the alpair 12pw has inverted surround iirc. It’s listed as 8” though, but I think the actual cone size is more like 7”.
Anyways, the alpair 12pw has inverted surround iirc. It’s listed as 8” though, but I think the actual cone size is more like 7”.
I don't know if it is the surround, but I can say for certain that the two drivers with an inverted surround that I have tested lack the resonance. This seems to be quite uncommon (inverted surround) so it is probably not something that is going to pan out.
I would prefer to stay with drivers that are generally available to the public as opposed to OEM specific replacement parts or parted out components.
That 1kHz peak is probably a dipole peak in combination with cavity resonance from the frame and magnet on the back. Even drivers with almost flat harmonic surround have this. The Audax PR170MO for example has a completely flat surround and also has this peak when used naked. Put them on a rectangular baffle and they measure and sound much better. Baffle shape helps here, round ani't very good for dipole and naked loudspeakers are in fact small round baffles. The idea of naked drivers is nice but not always the best solution, in fact, in most cases it can be improved upon. Drivers with very open frames with small neodynmium or alnico magnet work best here. Also no spider or magnet ventilation works better. Their cavities do strange things on the back, they work like small open baffle/cardioid on their own. Something you want to avoid went used out in the open. I have build lot's of dipoles and best of luck was always with drivers where I could have clear view on the cone when viewed from straight at the back. They measured and sounded best for this kind of application. Also some form of baffle other than round always worked out for the better. The 5PR160 wouldn't be my driver of choice, it's way to closed on the back and will most likely sound powerfull but restrained
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That is what I thought until recently. SL mentions cavity resonances as the source of the peak, but now I am not so sure what is causing it. The reason is that two drivers that are similar in size (frame OD) with a similar basket shape have very different responses. The HM130C0 is the outlier for sure, and the only thing really "different" about it is the surround. But that might be a red herring. Also, using the exact same frame from the same manufacturer, one driver has a resonance while the other does not. A peak near 1kHz is far below breakup for a 5.25" driver. Something does not really add up.
I also have found that when the motor is small and basket is open, there are fewer effects. The problem is finding smaller drivers that have a relatively small motor and very open basket. The PHY driver in your pic has like little spider legs for a basket! Nice. Wish there were more like that.
By the way, there is no baffle, so baffle shape has no bearing on this at all, and that includes the driver shape. For reference, see: Acoustics - Sound Fields and Transducers, Ch 13 of the 2012 version.
I also have found that when the motor is small and basket is open, there are fewer effects. The problem is finding smaller drivers that have a relatively small motor and very open basket. The PHY driver in your pic has like little spider legs for a basket! Nice. Wish there were more like that.
By the way, there is no baffle, so baffle shape has no bearing on this at all, and that includes the driver shape. For reference, see: Acoustics - Sound Fields and Transducers, Ch 13 of the 2012 version.
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Best way to find out would be to sacrifice some cheap drivers and recone one with inverted surround. I have done that in the past. With quite a lot of drivers the surround could be mounted either way. Would be a interesting experiment.
I also thought about the possibility of putting some stuffing between the back of the cone and the spider. It might change/decrease the resonance. It's not a fix for the long run but as a diagnostic it might confirm or disprove the basket resonance theory. It would also be less drastic than a recone!
Cool. Thanks for those suggestions as well!
Honestly, when I see measurements of a related driver from the Alpair series (the 10P) it makes me shudder.
Honestly, when I see measurements of a related driver from the Alpair series (the 10P) it makes me shudder.
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Retsel
The Lowther DX series have small, rare earth magnets and have inverted surrounds. There are the smaller 5.5 inch series, but the magnet obstructs a large portion of the cone. The 8 inch variety has a lot of the rear driver cone exposed.
Bud Purvine uses nude Lowther drivers with his speakers. You might want to look into what he is doing.
Retsel
The Lowther DX series have small, rare earth magnets and have inverted surrounds. There are the smaller 5.5 inch series, but the magnet obstructs a large portion of the cone. The 8 inch variety has a lot of the rear driver cone exposed.
Bud Purvine uses nude Lowther drivers with his speakers. You might want to look into what he is doing.
Retsel
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