WTF?! Dayton ND105-4 Fs over 1.5 times stated spec?

[Navy Guy]

I recently purchased a set of Dayton's ND105-4 to use in the bottom of a small 3-way bookshelf with the expectation that I would be able to get them down to 40hz in a reasonably sized box. I just measured them last night. Stated Fs is 53.8 and my measured Fs was 77.9/84.2 :eek:

All of the other parameters measured close enough to spec that it doesn't seem to be an issue with DATS. I also haven't had any trouble with any of the other drivers I have measured. What gives? Is there something I could be doing wrong to cause this or did I just get a bad set of drivers? I tried running some sine waves through one of them at high volumes for a few minutes and manually moving the cone to loosen the suspension, but it didn't really change anything.

Right now, I'm pretty upset because it makes them pretty much unusable for what I was wanting to do. Has anyone else had this problem with the ND105-4?

[dustinbagby]

Re: WTF?! Dayton ND105-4 Fs over 1.5 times stated spec?

I would try to break them in a little longer. I know a lit of members around here run 20-40hz sine waves for several hours before measuring.

[Chris Roemer]

Re: WTF?! Dayton ND105-4 Fs over 1.5 times stated spec?

Your Fs looks to be more like 25% above MY measurements, but, have you plugged YOUR parms into your box model software? Care to share ALL your parms?

When venting higher Q drivers, you've got to weigh your target F3 against box size and "ripple". If breaking them in "by hand" (which is how I do it), you should be gently pushing them to near Xmech (or Xlim), which is +/-10mm IIRC.

3 and 4 yrs ago I measured: Qts 0.48-0.52, Vas 0.12-0.13cf, Fs 56-65
Paul's measurements (from I don't know when): Qts 0.54, Vas 0.13, Fs 65.

They WILL do a strong 40 in about 0.3cf with these parms.

[Ryan]

Re: WTF?! Dayton ND105-4 Fs over 1.5 times stated spec?

I agree with Chris, when ever I measure an unusually high Fs I get a smaller Vas figure along with it and it often yields identicle results in relation to F3.

[Navy Guy]

Re: WTF?! Dayton ND105-4 Fs over 1.5 times stated spec?

I agree with Chris, when ever I measure an unusually high Fs I get a smaller Vas figure along with it and it often yields identicle results in relation to F3.

My Qts measured .60/.62 and vas measured .145/.150 cubic ft. I can still use them, it is just going to take a bigger box than I had planned. I was going to sacrifice a little bit of extension to fit them in a smaller box, but now I have to use the bigger box to get a similar response. It just doesn't fit into my original plans. I'm just disappointed because everything else I got from Dayton has been pretty spot-on.

[Chris Roemer]

Re: WTF?! Dayton ND105-4 Fs over 1.5 times stated spec?

I see what you're saying. It's looks like roughly 2x for box volume, or adding about 15Hz to the F3. Sorry 'bout that.

[SirNickity]

Re: WTF?! Dayton ND105-4 Fs over 1.5 times stated spec?

I bought a few of them about a year ago and one measured quite a bit off from the published specs. Turned out to have a bent frame.



I put it in my "DIY amplifier testing" pile.

[kanemack]

Re: WTF?! Dayton ND105-4 Fs over 1.5 times stated spec?

I bought a few of them about a year ago and one measured quite a bit off from the published specs. Turned out to have a bent frame.

[ATTACH=CONFIG]45420[/ATTACH]

I put it in my "DIY amplifier testing" pile.

that's just a new form of venting... it's called the f'd up frame vent. audiophile will have an article soon.

[SirNickity]

Re: WTF?! Dayton ND105-4 Fs over 1.5 times stated spec?

I was thinking it might be resonance control, but that makes sense too. ;)

[thekorvers]

Re: WTF?! Dayton ND105-4 Fs over 1.5 times stated spec?

I bought a few of them about a year ago and one measured quite a bit off from the published specs. Turned out to have a bent frame.

[ATTACH=CONFIG]45420[/ATTACH]

I put it in my "DIY amplifier testing" pile.

That doesn't look too bad. I am sure that that is fixable.

[billfitzmaurice]

Re: WTF?! Dayton ND105-4 Fs over 1.5 times stated spec?

I would try to break them in a little longer. I know a lit of members around here run 20-40hz sine waves for several hours before measuring.

I break them in overnight. Also, be aware of the temperature. If you're in a workshop that's not at least 65 degrees the suspension will stiffen, causing a high fs reading.