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Old 12th June 2005, 11:53 PM   #1
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Default Is WinISD always accurate?

I'm building a pair of very small, portable speakers.
The driver units are Visaton FRS 5 8ohm.

http://www.visaton.com/english/artikel/art_257_1_3.html

Frequency and impedance response:
http://www.visaton.com/english/bildg...quenzgang.html

Doesn't look bad at all...

But simulated on WinISD, I can't get much better than this.
There's always a big peak at around 300hz, no matter what volume or tuning freq. I choose.
WinISD chooses an 8.5L enclosure (?!), too big, but the peak is there.
Is WinISD fooled by the high(ish) FS of this driver - 250hz?
Or is Visaton telling us the Snow White story?
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Old 13th June 2005, 12:09 AM   #2
joensd is offline joensd  Germany
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Hi,
the driver has got a very high Qts and that makes it impossible to get a even near flat response in a BR.
What a lot of people do with the FRS8 for example (also high Qts) is to take a sealed box (~1l) and use a series cap too flatten out the peak.

greets
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Old 13th June 2005, 12:13 AM   #3
grrr is offline grrr  Netherlands
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Hello Carlos

I do not think you can get a flat response with a Qts 1,28 in a bas reflex enclosure. a leak closed box or open baffle may work.

Remco
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Old 13th June 2005, 01:14 AM   #4
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Quote:
Originally posted by joensd
What a lot of people do with the FRS8 for example (also high Qts) is to take a sealed box (~1l) and use a series cap too flatten out the peak.
Yes, the series cap is an option, but I would loose even more bass...

Quote:
Originally posted by grrr
I do not think you can get a flat response with a Qts 1,28 in a bas reflex enclosure. a leak closed box or open baffle may work.
I didn't think about the open baffle option, because I wanted a small speaker.
May give it a try.
What dimentions would you use for such a small driver?

Btw, after running-in for some days, these drivers sound quite good in the midband, and not bad at all in the treble, very extended.

Simulation for a 1,2L (default WinISD calc) sealed box.
The peak follows me around.
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Old 13th June 2005, 01:23 AM   #5
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Wrong speakers for your intended application.
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Old 13th June 2005, 01:35 AM   #6
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Quote:
Originally posted by Bill Fitzpatrick
Wrong speakers for your intended application.
I'm starting to figure that out...
At 8 a piece, well...
Gonna try some open baffles, it's easy and I have the MDF...

It's a slow day, you know...
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Old 13th June 2005, 07:50 AM   #7
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Or use negative output resistance for your amp to reduce Qes.

Regards

Charles
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Old 13th June 2005, 07:54 AM   #8
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Don't assume that an open baffle has to be large: they don't. They often are, especially with full-range drivers, but it's not an invariable rule. If you haven't looked in the theory section (concepts) here: I suggest you do before proceeding.
http://www.linkwitzlab.com/
Best
Scott

Oh -and WinISD is often quite accurate (not bad at all for freeware), but if you want better modelling software, get Martin King's MathCad worksheets.
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Old 13th June 2005, 09:25 AM   #9
joensd is offline joensd  Germany
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Quote:
Yes, the series cap is an option, but I would loose even more bass...
Thats what one would think in the first moment.
BUT a high pass at the right XO-frequency will effectively boost the bass.

Quite "trendy" at the moment in german DIY-magazines:
Sealed subwoofers with series cap(s).

greets
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Old 13th June 2005, 09:44 AM   #10
joensd is offline joensd  Germany
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Click the image to open in full size.
All I can come up with at the moment.
Plugged in some numbers in boxsim which is a nice,free and small loudspeaker sim written by a Visaton-forum-member and so includes measured responses from Visaton.

Volume is 1,2L, sealed with 120uF high-pass cap although Id just throw some different electrolyts at the speaker and listen.
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