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Old 23rd August 2010, 01:37 AM   #21
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Don't want to rain on the parade, but you might want to also take into account the room and the relationship to the room boundaries since that will do a whole lot to alter the presumed "flatness" of output... also the height above the floor plays a role.

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Old 23rd August 2010, 02:25 AM   #22
Ron E is offline Ron E  United States
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Quote:
Originally Posted by jaybee View Post
Thanks so much for doing that.
It looks like a pretty sophisticated program, all the enclosure losses are broken out. That's nuts!
I've been putting the peak to peak linear excursion in ported.xls because that's what I thought they were asking for. I see now this thing isn't going to be quite as wonderful as I thought. That's going to get even worse with the active filter, since it has a 2.8 dB bump before rolloff.
Are most manufacturers quoting one-way xmax? If so, I feel misled by Seas.
Yeah, its my own Unibox - style PR sheet, started around 1998 when I was just a wee lad . I've been wanting to add filter response, just haven't had a motivation until now - attached is the filtered response with your parameters - ignore the group delay/phase chart for now - too many interrelated cells on that one to untangle just yet.

Most manufacturers nowadays quote one way xmax - SEAS and Dynaudio were notable exceptions in that they always quoted peak-peak - they do specify "p-p" but if you don't know what that means, it can be misleading. The only 8" woofer I know of with close to 14mm of one way excursion is the tangband W8-something or other, IIRC
Tang Band W8-1363SB 8" Subwoofer | Parts-Express.com

This design you have made has OK extension, but not much power handling just above resonance. MaxSPL is quite good for an 8", but music with power in the 30-50Hz range could cause issues depending on how much power you feed it. Excursion shown is for a 35W/8 ohm input.

If you boost closer to the tuning frequency, you will have less of a problem with excursion. Attached is your design 1, and my example 2, both with the same woofer and 10" PR, mine with slightly altered tuning and filter - note that this is far from optimized, just an example showing better results with filter and pr tuning matched.

What are your goals for this system?
Attached Files
File Type: pdf passivebetafiltered.pdf (155.2 KB, 6 views)
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Last edited by Ron E; 23rd August 2010 at 02:32 AM.
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Old 23rd August 2010, 02:48 AM   #23
Ron E is offline Ron E  United States
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Nice guitar sound, BTW, Jeffrey. Lush hollow-body tone.
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Old 23rd August 2010, 04:45 AM   #24
jaybee is offline jaybee  United States
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Thanks Ron. I'm most impressed with your skills too.

The application for this thing is a 3-way near field studio reference monitor. I realize this is not an easy project for an unexperienced designer, but I hoped to minimize my chance of utter failure by triamping, or biamping and using a known-good design for the passive mid-high part of the system.

So the design goals are what you'd expect for the intended use; primarily, high headroom (fail!) and low distortion. This design is obviously coming up way short and I'm scrapping it. I compromised somewhat on potential efficiency with the SC4 alignment - I read from Small that this is one of the best among ported designs for transient response and this is important in my mind at least. Very low frequency extension is probably the lowest priority but a modest 40Hz was the rough goal.
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Old 23rd August 2010, 04:48 AM   #25
jaybee is offline jaybee  United States
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Bear, thanks for chiming in. As you can imagine, in light of the application, my little production suite will be treated to the best of my ability.
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