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Multi-Way Conventional loudspeakers with crossovers

Anyone seen a project using Seas U18RNX/P and 27TBFC/G paired?
Anyone seen a project using Seas U18RNX/P and 27TBFC/G paired?
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Old 16th February 2014, 07:04 PM   #1
Stewart Holmes is offline Stewart Holmes  United Kingdom
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Default Anyone seen a project using Seas U18RNX/P and 27TBFC/G paired?

Hi, Am building my first 2 ways with Seas U18RNX/P woofer and Seas 27TBFC/G tweeter. Has anyone seen these drivers paired before? I could do with having a look at the crossover schematics and some opinions on how they sound. Any advice would be much appreciated.
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Old 19th February 2014, 06:47 PM   #2
Juhazi is online now Juhazi  Finland
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You can use Zaph's L18 as guideline. U18 is cleaner and has a bit different T/S parameters, but soory I can't tell you which components to change!
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Old 19th February 2014, 07:01 PM   #3
Stewart Holmes is offline Stewart Holmes  United Kingdom
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Thanks for your reply i did think only last night 'surely my x/o wont be much different from Zaph Audios L18'. I'll start a new thread see who may know what to do, thanks again Juhazi Hey just noticed your system has Zaphs L18, how do they sound? I was so close to getting the L18.
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Old 19th February 2014, 10:59 PM   #4
PeteMcK is offline PeteMcK
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re:"'surely my x/o wont be much different from Zaph Audios L18' - The L18 notch probably won't be needed for a poly cone woofer, & you'd need to tweak the inductor value for any differences in the impedance graphs & baffle width, although it's probably not that critical...
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Old 20th February 2014, 12:13 AM   #5
Stewart Holmes is offline Stewart Holmes  United Kingdom
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Thanks Pete, that's a great help. I had to do my homework on what a notch filter is then. I forgot it has an offset tweeter to help with the diffraction and baffle width is almost 2" wider (presuming they not chamfered the driver hole or used bitumen/felt dampening on the internal side walls) yet the tweeter distance is within 2mm (at this time).

I think i'll give it a go knowing it will need tweaking, i will know a lot more about crossovers by then and I think copying a design from a respectable loudspeaker builder will be much better than am likely to design.
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Old 25th February 2014, 11:50 AM   #6
Stewart Holmes is offline Stewart Holmes  United Kingdom
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Quote:
Originally Posted by PeteMcK View Post
re:"'surely my x/o wont be much different from Zaph Audios L18' - The L18 notch probably won't be needed for a poly cone woofer, & you'd need to tweak the inductor value for any differences in the impedance graphs & baffle width, although it's probably not that critical...
Hello again, I am going to order the components for my new crossover. Do you recommend I order different values of inductor? Its a 2.2mH and was thinking of getting a 1.8mH and a 2.0mH and see which sounds best, or should I order the 2.2mH and unwind the coil till it sounds good? Thanks.
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Old 25th February 2014, 05:05 PM   #7
sreten is offline sreten  United Kingdom
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Hi,

The L18 x/o is a completely different kettle of fish
to that required for the U18 and will be wrong.

rgds, sreten.

http://sites.google.com/site/undefinition/diy
(see if nothing else, the excellent FAQs)
The Speaker Building Bible
http://audio.claub.net/Simple%20Loud...ign%20ver2.pdf
FRD Consortium tools guide
Designing Crossovers with Software Only

Note the Seas curves are measured in boxes, not
a big baffle, though they show baffle response.
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Old 25th February 2014, 06:26 PM   #8
Stewart Holmes is offline Stewart Holmes  United Kingdom
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Quote:
Originally Posted by sreten View Post
Hi,

The L18 x/o is a completely different kettle of fish
to that required for the U18 and will be wrong.

rgds, sreten.

http://sites.google.com/site/undefinition/diy
(see if nothing else, the excellent FAQs)
The Speaker Building Bible
http://audio.claub.net/Simple%20Loud...ign%20ver2.pdf
FRD Consortium tools guide
Designing Crossovers with Software Only

Note the Seas curves are measured in boxes, not
a big baffle, though they show baffle response.
Thanks Sreten, I thought with Zaphs L18 crossover only having a inductor in the LF and both drivers having the same sensitivity Zaphs crossover would only need adjustments in the woofers inductor, with having the same tweeters. The Zaph one has a notch filter because of the cone break-up in the L18 woofers cone yet the U18 is a lot cleaner so won't need the notch.

You know more than than me though so will I need a new design crossover altogether? Thanks again.
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Old 25th February 2014, 06:57 PM   #9
sreten is offline sreten  United Kingdom
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Hi,

The L18 x/o is elliptical. The notch is carefully dimensioned,
to also shape the response in the x/o region to the target
4th order L/R acoustic slopes, and get phase tracking right.

(Basically C of the notch is matched to the BSC L moreorless,
and then L of the notch adjusted to hit around 8KHz, and
you basically live with what you get at that L notch value.)

YMMV but 2nd order L/R target acoustic slopes may be
possible, or some other variation which you can only
really investigated with some serious modelling / simming.

Note the very different responses of the L18 and U18
around 1KHz and the range above on Seas site.
No way will their x/o's have much in common.
(Note Seas measure bassmids in boxes.)

rgds, sreten.

Many would pair the U18 with the Seas 27TDFC.

Last edited by sreten; 25th February 2014 at 07:16 PM.
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Old 25th February 2014, 09:59 PM   #10
PeteMcK is offline PeteMcK
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re:"Do you recommend I order different values of inductor? " - no, that's too expensive, just calculate the correct value. First work out your baffle step freq. = 115/baffle width.
Then look up the impedance of the woofer at that frequency from manufacturer's data sheet. Put that value into an online 1st order crossover calculator, which should give the inductor value. Buy the next available size up, but buy a good one, with low DCR.
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