Some Design Help on a Seas 2 Way

prighello

Member
2012-08-20 9:00 pm
Hello, I was hoping to get some help on a design I'm trying to put together. I've only built kits before so this is my first attempt to design a system. I won some drivers in a raffle: Seas 29tff/w tweeters and Seas L15 woofers and I'm trying to build a small set of stand mounts. I plan to use the PE 0.25 cubic foot enclosure and port it to get some additional extension. I cannot take measurements so I'm using the FR charts from Seas which is where I'm getting stuck.

The woofer FR chart says it was measure in a closed 7L enclosure and since the PE 0.25 ft^3 cab is roughly 7Ls I think I'm okay to use the chart with no need to adjust for baffle diffraction or box modeling. Does this sound right? What about the fact that I will add a port. Should I try to model this and if so how since the FR graph is for sealed?

The Tweet FR chart says it's measured on a 0.6m by 0.8m baffle which is about double the size of the baffle I will use plus I'm guessing it's placed in the center while mine will be above the woofer. Is this chart garbage then? Can I compensate for it in anyway. If not, could I use an infinite baffle measurement from say Zaph's website and then model the diffraction for my baffle/placement? If so, do I tell the software the tweeter is 1 inch (the dome size) or do I tell it the tweeter is 4 inches (size w/mounting plate)?

Sorry if these are dumb questions, I've only been in the hobby a few months and I am still learning. I appreciate any help or advice anyone could provide.
 

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I think 0.25 cu feet is way too small here. :)

You're just making life difficult...how you gonna squeeze everything in?

This 0.38 cu feet looks about right:
Dayton Audio TWC-0.38MA 0.38 ft³ 2-Way Curved Cabinet Maple 302-717

What is that? 11-12L. Better. Vas is 12L here on Qts 0.35.

SEAS L15RLY/P

The L15RLY/P is so similar to the W15CY001 that Troels has done most of the work already for you, especially the notch for metal cone breakup:
SEAS 5INCH

Troels also uses the 29TFF/W tweeter in the SEAS CURV. You just need to put it all together. :cool:
 

prighello

Member
2012-08-20 9:00 pm
Thank you all for the insight.

system7, if I change box sizes wont my published FR plot from Seas be useless? All I'm really trying to do is get the right plots so I can design the crossover correctly. I have no way to take measurements so I'm kind of at the mercy of what's available to me.
 
It's interesting to me that our diyaudio forum friend Joachim Gerhard made a damn fine loudspeaker with your SEAS L15RLY/P, which he even helped design:

Canalis Anima loudspeaker | Stereophile.com

[IMGDEAD]http://img267.imageshack.us/img267/7088/sonicsanima.jpg[/IMGDEAD]

This is not your usual flat baffle, of course.

Troels Gravesen uses similar drivers here in a slightly different way. Either way you follow in the footsteps of clever people. SEAS 5INCH

I can't help noticing how similar the bass and treble drivers are in most respects. I draw my own conclusions. Why reinvent the wheel? :D
 
Thank you all for the insight.

system7, if I change box sizes wont my published FR plot from Seas be useless? All I'm really trying to do is get the right plots so I can design the crossover correctly. I have no way to take measurements so I'm kind of at the mercy of what's available to me.
I noticed your question from before. (I prefer to answer 1 at a time, if it makes any sense to you). No, the measurements are done in a standard baffle free-field. If you want to be more accurate, you can measure your drivers (in your baffle) for final simulations and testings of the final speakers.
That was in general...
""...The dotted line is a calculated response in infinite baffle based on the parameters given for this specific driver. The impedance is measured in free air without baffle ""
You can read about the subject than just having an answer in one or two lines.
Measuring loudspeakers - and a training course
Measuring Loudspeakers, Part One | Stereophile.com
Measuring Loudspeakers, Part Two | Stereophile.com
Measuring Loudspeakers, Part Three | Stereophile.com
 
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prighello

Member
2012-08-20 9:00 pm
Well I just jumped in and did it based on the FR charts from Seas and Zaph. Simmed measurements for baffle, box, etc then tuned by ear. Here's the results, though it kind of looks funky it sounds better this way than the flat response I originally designed in the software. Thus, I can only assume this isn't spot on to what's actually going on, but ehh they sound good to me.
 

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Very nice, prighello. :)

Was that a 7 or 12L box in the end?

Metal woofers present some fierce difficulties. I see you did a 10kHz notch as required. I found a 3rd order treble filter had something going for it and a bit more bass rolloff.

But the circuit that really lines everything up nicely with a 5" metal woofer is an old-fashioned 4th order on the woofer. This is not a recommended circuit, because I only spent 5 minutes on it, and I'm sure it could be done better, but it lines phase up nicely.
 

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prighello

Member
2012-08-20 9:00 pm
Hi System7,

Thanks for the advice. I used a 7L box so space was a concern as you had mentioned. Thus, I went with a crossover design that didn't require a lot of components so I could actually fit it in the cab. I've some ideas on how to clean up the response but without real measurements I hesitate to muck with it much more.