Any alternative to Radio Shack sound level meter?

Thanks for the great responses. I have already done the simple setup a couple of years ago, with the xover at 50 hz and 24dB with the level set by the RS meter. But I want to set up the PEq, so I may need the precision of the option by Kijanki, and I as I have a 64 bit PC close enough to work, I will probably try that.  (My smart phone is only a cheapie Samsung.) Thanks again.

@oldears  I did few frequency sweeps only, so far (results  look pretty bad), but program has a lot of tools:

 It includes tools for generating audio test signals; measuring SPL and impedance; measuring frequency and impulse responses; measuring distortion; generating phase, group delay and spectral decay plots, waterfalls, spectrograms and energy-time curves; generating real time analyser (RTA) plots; calculating reverberation times; calculating Thiele-Small parameters; determining the frequencies and decay times of modal resonances; displaying equaliser responses and automatically adjusting the settings of parametric equalisers to counter the effects of room modes and adjust responses to match a target curve.

The easiest I've used is a free download app called audiotools.  It provides a sound level meter and also real time analyzer adn fast fourier transform tools.

You can see gaps in your system and room.  I use the stereophile test cds and play pink noise or other signals to see where the system and room is lacking.

not complicated at all and quite easy and simple to use.

Not professional quality because you are using your Ipad or Iphone's microphone, but it works pretty well non-the-less.

enjoy

Minorl, It is easy to see the problems but much harder to fix them.

Kijanki, don't feel bad. It always looks awful. When I show people what their system is actually doing they usually puke. Remember a lot of the variation below 150 Hz is room effect. If you move the microphone three feet in any direction it will look totally different. 

You are absolutely correct.  But, if you don't know what the problems are especially peaks and holes in your system/room response, you are stabbing in the dark.

but, you are right.  fixing it is serious business.  Room correction has got to be the most difficult mind numbing expensive experience.  not for the faint of heart.  The good thing is if you know the problems, it is no longer trial and error.  

enjoy