Is WinISD always accurate?

[carlosfm]

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/bildgross/257_afrequenzgang.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?😕

 

[joensd]

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

 

[grrr]

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

 

[carlosfm]

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...😀

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.

 

[Bill Fitzpatrick]

Wrong speakers for your intended application.

 

[carlosfm]

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...😀

 

[phase_accurate]

Or use negative output resistance for your amp to reduce Qes.

Regards

Charles

 

[Scottmoose]

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.

 

[joensd]

Yes, the series cap is an option, but I would loose even more bass...

That´s 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

 

[joensd]

An externally hosted image should be here but it was not working when we last tested it.

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 I´d just throw some different electrolyts at the speaker and listen.

 

[carlosfm]

An externally hosted image should be here but it was not working when we last tested it.

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 I´d just throw some different electrolyts at the speaker and listen.

That's much better, thanks.
But it rolls-off at 200hz... my point in using the small bass-reflex enclosure was to extend the output a little lower to 80~90hz...

 

[carlosfm]

Aham...
I've cut two pieces of 10mm MDF, at 14.5*18cm.
Two round holes, stick the drivers in...
I'm surprized.😱
No strange effects, very natural sounding, there's even some "bass".
Midband and treble are very good.
Treble is very extended, unlike most fullranges. This is an advantage of such a small driver.
Gets me thinkin' if this driver wouldn't go really well in a two-way speaker, crossed low (like 500hz).
A mix of open-baffle and sealed woofer.



PS: oh, and they image like hell.