What's to chat about?

[Grant Bunter]

Where, in the case of the Delta 12LFA and S2012, the S2012 boasts the higher Xmax and resultant Vd.
12LFA Vd 243
S2012 Vd 270

Your guess is good, and I was wrong.

What I'm finding interesting here (and every time this happens), is that, despite one driver having greater Xmax and hence Vd, it's voltage displacement limit is identical to another driver with less Vd.

To me, that means Vd is useful as a comparison tool, and, that's about it.

The only saving grace for the S2012 is the decreased weight...

[Seth]

...What I'm finding interesting here (and every time this happens), is that, despite one driver having greater Xmax and hence Vd, it's voltage displacement limit is identical to another driver with less Vd...

I noticed that too. I think a couple things are going on. Different drivers behave slightly differently, even though, as you said, the horn dictates response and/or sensitivity. The true importance and value of impedance curves and such are admittedly beyond me at the moment, but I think it has something to do with it too. But mostly, I think Bill just rounds things to the nearest safe number, knowing nobody is going to notice fractions of a decibel.

However, if we math out the voltage limits for the BP102 and S2010, it's completely linear.

28v x 28v / 8 Ohms = 98 watts... divided by 4.0 (the Xmax of the S2010) = 24.5 watts per millimeter... x 6.2 (Xmax of BP102) = 151.9 x 8 Ohms = 1215.2 of which the square root is... Ta Daaaahhh 34.85 volts, essentially 35, the BP102 Voltage limit.

The Xmax difference between the S2012 and the 12LFA is pretty small, only four-tenths of a millimeter. If I math that one out the same way, using 35 volts and the 12LFA as the benchmark, it would take 36.4 volts to get the extra 4 hairs worth of excursion. Scaling it up to the 9.1 mm Xmax of the 3012LF comes out to 48 volts. Pretty darn close to the recommended 50 volt limit in the T48 (55v in the T39). And, ya know... I just realized the 12LFA isn't listed in the T48 plans. I must have carried over the 35 volt figure from the T39 plans.

[Seth]

So, as far as measuring and loging speaker response, what's the budget solution? Would something like REW and a Behringer ECM8000 microphone produce acceptable results? I haven't really played with REW and have no idea if it's even an appropriate software solution for the purpose.

[Bill Fitzmaurice]

I use HolmImpulse freeware and Dayton UMM-6 USB mic.

[Seth]

I use HolmImpulse freeware and Dayton UMM-6 USB mic.

That's pretty great. Thanks for turning me on to that Bill. I don't see the option to graph the response as dB SPL like the graphs throughout your website. Can HolmImpulse do that or is that something different altogether?

[Bill Fitzmaurice]

You need a sound meter to get a SPL reading. Once you have a base reading at 100Hz you use that to calibrate the entire chart. If you buy a meter make sure it has 'C' weighting, 'A' weighting is useless.

[Seth]

I just picked up a new-to-me (used) 10" table saw and would like to put a fresh blade in it. Is there a super fantastic blade out there in bladeland any of you would recommend for the type of cutting we're doing here? Any reason to spend more than the typical $20 blade?

Here's the one I'm eyeballing
https://smile.amazon.com/Concord-Blades ... ms?ie=UTF8

[Bill Fitzmaurice]

I'm sure it's OK. I use Freud Diablo, which are similar.

[Seth]

Are Qts and Vas too far out on this driver to be used in the SLA Pro and Wedgehorn 6?

PRV 6MB250-NDY - Fs 113.6Hz, Qts 0.71, Vas 4.9L, xmax 4.25mm

SLA Pro - Fs 118Hz, Qts 0.54, Vas 5.8L, minimum xmax 3.5mm

Wedgehorn 6 - Fs 110Hz, Qts 0.5, Vas 6L, minimum xmax 3mm



PRV datasheet - https://prvaudio.com/wp-content/uploads ... asheet.pdf

[Bill Fitzmaurice]

Qts that high will cause boom.

[Seth]

Thanks Bill. And thanks for the blade feedback too

[Seth]

Going back to the point about equal loudness curves...

.. perhaps this could go towards explaining why EQ'd flat with pink noise is still a little thin on the bottom end.

Yup, that's the why because.

I inverted the dBA weighted curve and compared it to the equal loudness curves.

Seems like it could be worth a try and a listen to EQ flat, but to a A weighted curve.

[Charles Jenkinson]

Seth, did I miss the build thread? ...but then, being on the cusp is a worthy pass time.

[Seth]

Seth, did I miss the build thread? ...but then, being on the cusp is a worthy pass time.

Nope, you haven't missed anything. But here's where I'm at with everything:

Still looking for reasonably priced lighter species Plywood. Thought I came across an internet source the other day. But, they had the same story... "sorry, we only have one sheet left and our supplier doesn't stock it anymore". I'm half way considering ordering some off Alibaba. Half way... not quite serious about it. Yet.

I have all the drivers to complete 8 DR200's and 7 (of 8 ) T48's. Soon to purchase drivers for 4 Wedgehorn 6's.

I've recently sourced an air compressor, 1/4" crown stapler/18g brad gun, pin nailer, router, table saw (fresh new blade also), and a bunch of 30" quick clamps. Pretty well set in the tool department, but need/want to look into a circle cutting jig for the router and some sliders that fit the tabbed 5/8" miter slots on my particular table saw... for making a sled.

I've been purposefully delaying starting the build due to having scheduled a knee surgery. I'll start the build as I recover. Thinking the Wedgehorns would be manageable to get things rolling. The sugery is this Thursday, day after tomorrow. So, Id expect a build thread in 4-6 weeks, I'd think.

How have you been Charles? All good there?

[Bruce Weldy]

some sliders that fit the tabbed 5/8" miter slots on my particular table saw... for making a sled.

No need to buy those. You have a table saw now, make them yourself from some solid wood. I made mine with some red oak from HD. Not only do you get the job done, but building the sled from scratch will help to hone your woodworking skills.