So I'm going to be tackling an active speaker project

[Johnloudb]

I welcome any and all input. Right now it appears to just be a case of blown output transistors but you never know what will turn up. I got to find some MOSFETs though.

[cjd]

Not quite yet. I think I've got it narrowed down to two, but I don't like the porting options I have for the enclosure. I need some elbows

I've got parts for one where the same holds - I believe I'll be doing a folded slot-port instead. Wants something like 50"x3" port... But in-room it'll hold to 20Hz in a relatively compact size (think it'll be 16x16x12) - if I had active circuitry in the mix I'd just build a 12" cube and apply something in the circuit to boost the bottom. 10" driver...

C

[twest820]

I use a 1.5mm chisel tip for everything from TSSOPs to 0805s to soldering 12ga wire to binding posts.

Hmm, SFP-CH15? Or one of the other profiles?

[Amphiprion]

That profile, but I use the STP tips since I am using leaded solder and like the lower temp tips. They work perfectly well even for heavy duty stuff. I also own drag hoofs and other chisels, but usually just leave the 1.5mm chisel tip on there.

Actually, the tips that get left in my iron stand are:

STP-CH15
STP-CH30
STP-CH50
STP-DRH15
STP-DRH35
and whatever the standard fine point hot tweezer tips are for the MFR-PTZ tweezer set.

I love the OKi station FWIW. I've used OKi, Pace, Weller, and Hakko. The heater technology of the OKi gear is just freakishly awesome.

[Amphiprion]

With regard to the subwoofer, I am leaning towards cramming two 15" drivers into the Parts Express 3.0cf cabinet and running it in a sealed LT configuration. One driver in the front, one in the back, forces cancel, etc. Likely candidates are the RS390HF 15" woofers. Power would probably be provided by my Adcom GFA-555mkII with 325w per driver. I would only LT them down to an f3 of 25-30hz and I will probably add a 2nd order HP around the LT'd cutoff to achieve a 4th order rolloff to limit low end excursion.

[Johnloudb]

Hi Mark,

So you mean like a dipole sub? Or Bipole? I never see bipole subs. Could that make placement more difficult?

I had have a pair old Nelson/Reed sub boxes that are almost 5 cu.ft. They were dipole subs with four 12" woofers, 2 front an 2 back.

I plan on putting two Peerless XXLS in each box, since they will fit perfectly in the holes and have a box Q of between 0.6 and 0.7.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-1114

So I just plan on using a second order low pass shelving filter to extend bass response.

It has holes in the back too. So, now I'm wondering if I should put one driver on front and one on the back, and make it Bipole?

I might try both - be interesting to compare.

[Amphiprion]

I guess it would be a 'bipole' sub, though I never would think of it that way. Just two actives on opposite sides of the box. Although now you mention it, neat things could be done with a little time delay to get anything from cardiod to dipole woofer patterns....

[Johnloudb]

Although now you mention it, neat things could be done with a little time delay to get anything from cardiod to dipole woofer patterns....

Now your cooking! :T

[Amphiprion]

Well I'm sold. Cardiod woofer it shall be. I never thought I'd be using Praxis to try and measure the acoustic center of a subwoofer though.... wacky. We'll see how that goes. The drivers are out of stock until late December.

[twest820]

I love the OKi station FWIW. I've used OKi, Pace, Weller, and Hakko. The heater technology of the OKi gear is just freakishly awesome.

Yeah, CH15 is a nice tidy up of the X71A and X72A OKi picked up when buying Metcal. Haven't used OKi stuff as the Metcals in my life all seem set to outlast me; any sense if the tips are back compatible with Metcal wands? I haven't found data either way and without having an OKi tip to look at it's hard to tell if it'd fit, much less heat.

Have you used Hakko FM or FP systems? From what I've read the heater performance of FM and FP tips sounds comparable to OKi/Metcal. But those stations aren't commonly used so there's not much info. They are interesting from a DIY perspective as with a little patience you can pick up used Hakko systems at the Metcal MX-500 price point for less than Weller WES51/WESD51, Hakko 936/937, or used Metcal SP-200s go for. That's potentially some pretty serious bang for the buck, particularly as my experience is doing medium pitch surface mount soldering without a temperature controlled iron is a hassle.

Cardiod woofer it shall be.

Interested to see how it works out.

[Amphiprion]

The Hakko stations I've used are the little 936 stations as well as an older unit we have in the lab at work (can't remember model number, but it's physically huge, black chassis, gold lettering I think. 3 adjustable temp outputs). Nothing recent unfortunately, so I can't compare. I have used very recent Pace and Weller stations. The Pace stations are nice for some things (I prefer their through hole desolder tool for instance), but overall I like the OKi. One of the techs at work uses a Metcal MX500 I think it is and he has the same opinion re: Pace. NASA really likes Pace for some reason though.

I doubt the OKi tips would work with Metcal wands, as I think they use different frequencies for the RF heating. One brand is just above the AM band, the other just below it, and I can't remember which is which.

[twest820]

You're likely right; don't know what OKi uses off the top of my head. Metcal SP-200's 470kHz and the higher end Metcals are, I think, all 13.56MHz. My soldering time's mostly with the SP-200 and MX-500. They get the job done just fine too.

[5th element]

Would a cardioid sub necessitate two separate air spaces for the individual woofers? Having the driver on the front pushing forwards, as well as the driver on the back pushing in the same direction would be a recipe for disaster so I'd imagine half way in between wouldn't be so hot either.

[Amphiprion]

Yes, I would definitely be adding an internal baffle to separate the airspace. They need to be completely independent at LF. I might add the smallest of pinholes between the two compartments to equalize atmospheric pressure at DC between the two once they are sealed up, but that would be it.

[Johnloudb]

I don't think having one sub pushing forward and one pushing back is a problem. It would just change the response. On our Nelson/Reed dipole subs were that way, of course they had a second order high pass slope in the pass band. This was corrected for electronically.

I think it would be interesting to see how changing the phase of one woofer affects the frequency response of the sub, in one box. I'd think as you alter the phase from bipole to dipole you'd go from a high Q to low Q response. You might find a nice cardioid response and flat frequency response at the same time. Probably not, but might be interesting to see what happens.

If it sounds like I don't know what I'm talking about, then I probably don't! Just thinking out loud.

[twest820]

Mark, any thoughts on via in pad for DIY? I'm laying out some two layer amp boards that'll run in a low cost process (7 mil DRC, 15 mil min drill, soldermask plug from the bottom) and wondering about the smallest feasible discrete size for VIP and hand soldering. 0805 and larger seem like they should be fine but 0603 might not be worth the hassle as 15% of the pad area would be voided by the drill---could be enough to cause the components to flip up.