CA18RLY or SB17 ?

[percy]

As an end result of this thread I have narrowed it down to these two choices -

Seas CA18RLY
SBA SB17

The CA18RLY requires twice the enclosure volume, but besides that, I would like to know if there are any other pros and cons between these two drivers that I am missing. Looking at the specs of the CA18RLY its Qms, Qes, Mms, magnet weight, suspension compliance are quite apart from other "18" series woofers from Seas but I dont know what that means in terms of audio performance difference.

The CA18RLY could still be made to fit in a ~1.25ft³ to yield the same F3 as the SB17, and with just a little bit of a boombox bass hump. Again, what would be the implications on the audio performance of the woofer in this case ?

Looking forward to your inputs and comments.
Thanks!

[mayhem13]

I have no experience with the SB17, but have used the SEAS in several designs of TM,TMM and WMTW center channels. Even though the driver is very smooth to 3kh, it really shines when crossed low and sealed....keeping both LF distortion and HF cone breakup out of it's operating range. I've measured F3 of 60hz with a single CA18RLY in .75cuft sealed where the cabinet loading allows for a smooth rolloff while maintaining power handling. Sub 60hz content belongs with the large format drivers anyway.

If you want a small box bass champ, the CA18RNX is the driver you need or the slightly more expensive ER18 whose distortion profile is on par with woofers costing magnatudes more.

[percy]

Originally Posted by mayhem13

..it really shines when crossed low and sealed....

but then practically any respectable driver will when crossed low and sealed.

Originally Posted by mayhem13

If you want a small box bass champ, the CA18RNX is the driver you need or the slightly more expensive ER18 whose distortion profile is on par with woofers costing magnatudes more.

Yes the ER18 is great for 0.5ft³ range, but I am getting greedy for the extra 10hz or so of low end extension . unless you guys can talk me out of it

[mayhem13]

What would really clarify your needs is the intended tweeter to use with it.....how low can it cross?, or will it need to?, off axis reponse as compared to the upper range of the midwoofer?....and so on.

The Ca18RLY can easily do 4khz LR4 and has a seemingy natural 4th order rolloff with virtually no cone breakup to speak of while the SB has 3 nasty peaks above 3.5khz so if that helps make up your mind.....The CA seems the perfect fit for a ribbon/planar while the SB need's a robust 1" dome.

[cnclld]

I wouldn't cross any 6.5 inch woofer above 3kHz. The big cone just gets too directive that high which leads to a very uneven power response, even if you are using a waveguide. The CA18RLY has in addition a deep suckout at 3kHz off axis which limits its usable bandwith to about 2kHz. I'm using the CA18RLY myself as midrange and I'm very happy with its performance apart from its off axis behavior in the top end.

[twest820]

Haven't used either, but I've designed to this space and for me it's the SB17 hands down. Like most Seas the CA18RLY starts beaming around 500Hz and is a low Qms/high Rms driver. I prefer to keep directivity as consistent as possible and favor high Qms/low Rms parts. Distortion between the two is comparable, but I'd give the SB17 the edge.

[mayhem13]

Beaming......directivity......beaming....directivi ty.....and the difference is?

[twest820]

Prolly depends on how one thinks about things. Personally I'd say beaming is a subset of directivity considerations. Some of the others would be the basic radiation pattern of the speaker design (omni, dipole, omni to front firing, point source, line source...), use of waveguides or horns to shape the radiation pattern, and the crossover's effects on the pattern.

[dlr]

Originally Posted by percy

but then practically any respectable driver will when crossed low and sealed.

Yes the ER18 is great for 0.5ft³ range, but I am getting greedy for the extra 10hz or so of low end extension . unless you guys can talk me out of it

The ER18 is supposed to be a good driver and is used on John K's new system (to be auditioned at DIY NE in Oct.) called the NOTE. It does use two with the second one boosting the output below 300, but then it's needed because it is a dipole.

I can't say how it sounds in a 2-way system, but I have a design with the SB in a 2-way that was well received at our event last year. It may help you with your decision.

The Chameleon

Dave