BillFitzmaurice.info

pumpsfast wrote: Even this simple test is not the end all of test, its merely a reference. If the figures are close to the cabs spl chart all is well, if way off something might be amiss with the cab or driver and that where the fun starts, ask missile crisis .....

Haha, welcome to my life. Haven't built a sub that matched the chart to date, I'm still working on determining what is at fault. If someone knows a good SPL meter (let's keep it under 100 please) that I can use for sub testing I could really use one to set the level on my mic. Obviously the one I have is pretty bad so I'd like to find out just how bad. That's some great advice btw pumpsfast.

I would like everyone to get their I TOLD YOU SO!'s out of the way now.

The SPL meter was a POS...

Attached is an image showing just how much so. this was at 1.4 V I think (corner loaded but roughly 7 feet away) 40 Hz (yeah I know the whole c-weighting is 3ish dB low at this frequency part but that's not what I'm arguing). See how far off the POS meter is.
Note, the penciled in marks are just so you can read the meter (it was really bright and didn't show up in the pic so I drew over the numbers in paint)

Lol, hind sight is 20/20, good going. Ps which meter did you get?
edit American Recording Technologies mic, saw it on other thread

Righto then; I'm kind of lost

Was your original SPL meter the dud and not the T60?

What does your new meter say now for T60 output? Close to the mark or what?

Mate my dual demolishes, especially for only two $160 12 inch drivers.

Are you happy with your sub building ability now?

Fill me in bud, no told you so's here, just want to hear from another happy enthusiast

First mistake was buying anything with the word Pyle on it.

Titanium Hand wrote:Righto then; I'm kind of lost

Was your original SPL meter the dud and not the T60?

What does your new meter say now for T60 output? Close to the mark or what?

Mate my dual demolishes, especially for only two $160 12 inch drivers.

Are you happy with your sub building ability now?

Fill me in bud, no told you so's here, just want to hear from another happy enthusiast

Yes. The old (pyle) meter was the problem. Preliminary testing that needs to be repeated outdoors tells me that it is at least in the ballpark of matching the spl chart. Yes I'm happier with my sun building capabilities. What was bothering me was the fact that I overbuilt the sub such that it wouldn't leak and when it still read low I was concerned. Now I know that I was getting worked up over nothing.

Bruce Weldy wrote:First mistake was buying anything with the word Pyle on it.

Not doing that again.
+1000

Reading 125 dB here at max volume (c-weighted 7 feet from sub corner loaded). Playing music not sine waves.

MissileCrisis wrote:Reading 125 dB here at max volume (c-weighted 7 feet from sub corner loaded). Playing music not sine waves.

The meter doesn't have "A" weighted or "unweighted"?

I think you mean z weighted and no it doesn't have unweighted . It only has a and c. So yes it has a. However a weighted measures more than 20db low for subs so I don't know why I would use that to measure my subs. At least c weighted is closer.

I have yet to see an spl meter with an unweighted option (within reason) label budget. What is important is that this spl meter is accurate and is type 2.

Big day today, I took the subwoofer outside, duratexed it with 2 coats to supplement the base coat I painted on a few days ago, installed the wheels (thanks for suggesting them Leland - they look awesome and work amazingly) installed the rubber stopper things and installed the second set of speakon jacks. Now, for what you guys actually came here to see... the pictures. Also, I did some 1 w/ 1 m testing just because I had it outside and what not. I found that my T60 is within device error (+- 2 dB) of Bill's 20 inch wide T60 chart. I did a few different frequency based tests and I was sitting at ~92.8 dB at 25 Hz, 94 dB at 30 Hz 97 dB at 40 Hz 102 dB at 50 Hz and I didn't go any higher up because it was late and I didn't want to annoy the neighbors. I did for grins take it up to approximately 110 dB at 25 Hz and I wasn't near maxing it (guessing mid 20's of volts). I did run 1 sweep test with the microphone at a measured 1 m and although I didn't have the time to perfectly calibrate it to the meter for absolute spl accuracy it closely resembled the published spl curve in shape.

More pictures in the next post, I didn't know there was a max number?

Part 2 of finishing. I love these wheels, so I took close-ups. Back where it should be, all done. Proof that it is possible to half finish -> test, leave it there for a couple weeks, then pull it outside and finish it right (rather than just leave it halfway finished). Notes: I will have to touch up the paint in a few spots where I roughed it up a bit in turning it and miscellaneous scrapes, but otherwise it's looking pretty good imo. If any forum member questions the accuracy of the spl measurement charts point them my way and I'll back up that my T60 works exactly like the chart , and I'm not even a pro builder. IMHO my build quality for this subwoofer very solid, despite a mess-up early on everything has been using screws, dados, and very precise bracing. The only place I know I fall short is the finishing and aesthetics. For one thing we Dado-ed the whole bottom edge so there is a gap where the front handles are which I had to bondo and that part looks a little rough. A few other mismatches with the width of panels making slightly uneven edges (externally) makes it look a little less awesome but hey, I can say I built it.

Id say you did a superb job for a non professional builder. The first is always the hardest and being able to play it and it does what it is advertised to do and you built it by yourself with your own two hands is priceless IMHO. Now lets confirm the T39 is up to spec also!

After I verified the t 60 that thought crossed my mind. I'll let you know how it goes.