Maplins close-out on AP100Z0

[mhennessy]

Originally posted by richie00boy
I've been trying to measure an AP100Z0 this evening. It's straight out of the box. I measured Fs at 96Hz.

I'm having problems with the Fl and Fh for calculating Q though -- the sanity check yields Fs of 90Hz. I'm using the Brian Steele method, but without any series resistor -- just putting my meter in series and reading off current. Should be the same thing The meter is staying on the same range so it's resistance is constant, so that rules that out.

Must try and get my constant-current circuit sorted and see if that gives any better results.

I found that a brand-new driver needed running for a couple of minutes before FS would stabilise. Did you go back and re-check FS? It's possible it was just running in while you were making the measurements.

Two of my drivers have had a reasonable amount of use since I measured them, so I'll be interested to see how much they've changed when I get the chance to measure them at the weekend...

Something that may affect your measurements (although probably not the sanity-check frequency) - does your meter measure true-RMS?

Cheers,

Mark

[richie00boy]

I went back and manually checked Fs after getting the 'wrong' sanity check result. It was within 0.25Hz of my original reading. I was only driving at 200mV, so no chances of significant cone movement to cause running-in. If your driver is running in whilst you are testing it then you are driving it far too hard! I also did the entire test again to double check. Same results

The meter I am using is a top of the range Fluke that I have just skinted myself out on. It measures true RMS and frequency at the same time. I bought the meter as I was fed up with faffing about with leads, blurry scope screens and laborious reading interpretation. So I'm a little cross that it's not going right!

[mhennessy]

Originally posted by richie00boy
I went back and manually checked Fs after getting the 'wrong' sanity check result. It was within 0.25Hz of my original reading. I was only driving at 200mV, so no chances of significant cone movement to cause running-in. If your driver is running in whilst you are testing it then you are driving it far too hard!

That's true, but these drivers do seem to need a little run-in from brand new. The new driver I was talking about had an initial FS in the 80's, and I knew that the others that I had tested were in the 60's. These had all had some (not much) use. So, I ran it for a few minutes at around 15Hz, letting the cone move a few mm's each way. I left it for a few minutes before measuring FS again (in case there was any voicecoil heating). FS now measured 66.9Hz, and the sanity check gave 66.58

I was using 1.41V RMS, and a 7.5 ohm series resistance for the measurements... Your sanity-check results suggests a problem with the experiment rather than the driver. I guess your signal source is flat? I also guess your Fluke has a flat frequency response at these frequencies? These two are easy enough to check. I'm not sure what else is there to go wrong... One thing - you're measuring current directly - I wonder if it's worth trying a series resistor? That way, you can type the numbers directly into the spreadsheet...

I also did the entire test again to double check. Same results

I can understand your frustration. I noted that others have run these things in for many hours at mechanical limits (not xmax!) - I haven't done that, but already I have results that are pretty close to Audax's numbers. I will be able to do more testing at the weekend - I'll also measure the unused pair. Maybe I've just been lucky with the pair I'm currently listening to

The meter I am using is a top of the range Fluke that I have just skinted myself out on. It measures true RMS and frequency at the same time. I bought the meter as I was fed up with faffing about with leads, blurry scope screens and laborious reading interpretation. So I'm a little cross that it's not going right!

Sounds nice! What model did you go for? I've been promising myself a proper Fluke for 10 years now

Cheers,

Mark

[richie00boy]

I'm expecting Fs to be high and it's not a problem, the sanity check is. I'm want to do a before and after running-in, to see how much difference it makes. I'm wondering if just an hour or so will run it in enough.

I can't see how it can affect the results doing it on pure current measurement, but I'm going to try a series resistor of 10 ohms and see what results I get then.

I'm confident in the source as that's a decent signal generator. The meter is also flat (within 1.5%) from 0.5Hz to 100kHz, IIRC. I got a Fluke 187 with cal certificate. Basically my mate bought it when he got a new job. Then about a month later his contract ran out and there was no work for him, so he was in need of cash. So I got a huge bargain

[mhennessy]

Originally posted by richie00boy
I got a Fluke 187 with cal certificate. Basically my mate bought it when he got a new job. Then about a month later his contract ran out and there was no work for him, so he was in need of cash. So I got a huge bargain

OK, so now I'm really jealous

But it is my birthday next week.....

[wytco0]

ttt
any updates guys? Thanks

[5th element]

Well mine are going to be probably a while yet. Althought the cabinets are pretty much (sort of others need choppin up) sorted. Im replacing the fronts of all my front end (amps preamp DAC etc) so they all match and then buliding and equipment rack. Realistically this shouldnt take too long, but things always take longer then you think!

[richie00boy]

Yeah I will be a while yet, too. I also have some of the AP210Z0 to make a budget Orion OB, and a major sub project to tackle.

I'm also trying to source a pair of TM025F1 to match up with the AP100Z0 as Maplin did get a new lot in then promptly removed them from sale/sold out.

[Mark25]

i've been doing some testing lately, go with the two34xo, its in a different class! there are less than 20 left too!

[Ian J]

Richie,
would that budget Orion be passive/active/bi-amped whatever? Last year I started a thread on using these Audax 8" for OB (specifically the M0 with its high Q) but was warned they would need a lot of EQ.
Mark,
is that a Wilmslow HSM there?

Ian