Can simple crossover be designed w/ software + RS SPL meter?

[morbo]

I am trying to do a design for a widerange driver (TB 871) crossed to a woofer (Dayton RS 225) that has decent response to 1.5khz or so. I have access to LSPCad 5, but for measurement equipment, only have an RS SPL meter and a multimeter. Can I design a simple, good sounding crossover in the 200-500hz range using these tools?

 

[BillFitzmaurice]

Download an RTA program like the one at the Allen-Heath site, you can use the RS meter as a mic, it's accurate enough in that freq.range, then you can see what different components do in real time as you swap them.

 

[morbo]

Thanks for the suggestion Bill. How do you hook the RS SPL meter up to your computer though? Or do you measure and then manually enter values like in the parametric EQ spreadsheets I've seen?

 

[BillFitzmaurice]

The RTA has a pink noise source built in, the meter simply plugs from its RCA output into the computer soundcard. It's a very simple and easy to use rig, and within the midrange is adequately accurate. For the ten bucks or so the download costs a very useful tool.

 

[cjd]

I have also successfully used my SPL meter with Speaker Workshop for measurements. And Speaker Workshop is free. But it's a bit of a pain to get set up for measurements.

I finally realized I was probably not going to build a mic and pre, and sprung for a Behringer mic. With the rebate going right now, not a bad deal.

C

 

[BillFitzmaurice]

Speaker Workshop is nice but the required interface is a chore. The A-H RTA doesn't have the level of sophistication of SW but for crossover design and basic frequency response charting on the cheap it's very worthwhile and user friendly.

 

[morbo]

Ok well I will be trying this then, or some other similar RTA software, thanks a lot for the tips! If I had known the Ratshack meter was useful for this kind of thing, I'd have started fiddling a long time ago Has anyone been able to get useful measurement files that could be exported to something like LSPcad using such software and the RS meter? I've tried speaker workshop and the need for a jig, plus the interface really turned me off.

 

[kelticwizard]

Radio Shack SPL meter comes in different models, even different analog models.

The response curve for the mic of various models is given here. So you can take these into account when measuring.

http://www.gti.net/wallin/rsmeter.htm

 

[ergo]

Morbo,

If you can use LspCad then you can also use JustMLS that comes with LspCad. I have made all my project measurements with JustMLS and it works just fine.

With RTA type measurement you can not get acceptable results to import into LspCad. You will not have phase data and impedance mag + phase data. Also The freq response will be polluted with room reflections.

Check

measurements

crossover

Ergo

 

[morbo]

thankyou kelticwizard and ergo, I will use the correction files and see if I can't get up and running using the RS SPL meter in JustMLS. I presume I want to do this with the drivers mounted in the boxes (or is just the baffles ok?), but do I place the mike nearfield (6"?) or in the listening position? Maybe I should just get off my butt and start reading the manuals

 

[johninCR]

Will someone please explain why Morbo should even go to all that trouble. It's like getting a geologist out to do a ground sample when all you are doing is planting a bush.

Just pick a point based on your crossover slope. Say 250 with a steep slope and 500 for a shallow slope to take advantage of the 871's dynamic range.

What is measuring supposed to accomplish in picking a crossover point for 2 drivers that are obviously well within their non-stressed operating range. Measure the results if you must, but use and trust your ears too.