10" woofer for 3 way design - Seas L26RFX/P vs L26RO4Y

[Mario Pankov]

I thought the limited xmax would have been the reason for it not working well in a sealed box, hmm.

Would the phase plug really even be offering much for these lower frequencies?

The RO4Y has higher linear xmax of 14mm one way vs only 7mm for the RFX/P but is far less sensitive - about 82.5-83db under equal power ( even less in the bass notes compared to the RFX/P which is almost 3db more sensitive at 40hz on the IEC baffle ) so it will need to move far more in order to achieve the same sound pressure as the RFX/P. I do not see a big benefit of using it over the RFX/P purely based on excursion and linear stroke. Its inductance is massive - 3.85mH for a 4 ohm driver with a copper cap. This either means copper cap is not placed optimally ( doubt this ), or the voice coil is tremendous ( likely ). Large inductance means more distortion with any extra mm of xmax, under equal conditions for the remaining parameters and also mean higher mms. Not sure what the copper cap does on a driver intended to be used as a subwoofer.

Also, I think the RFX/P uses an undercut polepiece so it will be somewhat symmetrical even without copper/aluminium in the motor. The phase plug would help with heat transfer but these ( including the Magnesium ones ) leak air through the gap between the cone and the phase plug, perhaps this is what Juhazi had in mind when he mentioned its not that suitable for sealed.

 

[poshy]

The RO4Y has higher linear xmax of 14mm one way vs only 7mm for the RFX/P but is far less sensitive - about 82.5-83db under equal power ( even less in the bass notes compared to the RFX/P which is almost 3db more sensitive at 40hz on the IEC baffle ) so it will need to move far more in order to achieve the same sound pressure as the RFX/P. I do not see a big benefit of using it over the RFX/P purely based on excursion and linear stroke. Its inductance is massive - 3.85mH for a 4 ohm driver with a copper cap. This either means copper cap is not placed optimally ( doubt this ), or the voice coil is tremendous ( likely ). Large inductance means more distortion with any extra mm of xmax, under equal conditions for the remaining parameters and also mean higher mms. Not sure what the copper cap does on a driver intended to be used as a subwoofer.

Also, I think the RFX/P uses an undercut polepiece so it will be somewhat symmetrical even without copper/aluminium in the motor. The phase plug would help with heat transfer but these ( including the Magnesium ones ) leak air through the gap between the cone and the phase plug, perhaps this is what Juhazi had in mind when he mentioned its not that suitable for sealed.

Thanks for the analysis on this Mario, it's very interesting. Perhaps it's this added sensitivity is what people are referring to as it being musical.

 

[Face]

The RO4Y has higher linear xmax of 14mm one way vs only 7mm for the RFX/P but is far less sensitive - about 82.5-83db under equal power ( even less in the bass notes compared to the RFX/P which is almost 3db more sensitive at 40hz on the IEC baffle ) so it will need to move far more in order to achieve the same sound pressure as the RFX/P. I do not see a big benefit of using it over the RFX/P purely based on excursion and linear stroke. Its inductance is massive - 3.85mH for a 4 ohm driver with a copper cap. This either means copper cap is not placed optimally ( doubt this ), or the voice coil is tremendous ( likely ). Large inductance means more distortion with any extra mm of xmax, under equal conditions for the remaining parameters and also mean higher mms. Not sure what the copper cap does on a driver intended to be used as a subwoofer.

That inductance is no surprise with a 4 layer VC. If the driver is to be used in a 3 way, the original L26ROY makes more sense. https://www.madisoundspeakerstore.com/approx-10-subwoofers/seas-l26roy-10-subwoofer-d1001-04-4-ohm/

Here is a long read on inductance in subwoofers. http://www.avsforum.com/forum/155-diy-speakers-subs/1976745-more-inductance.html