Wow. Every now and then I learn something that I never expected.

This is the most interesting thing I have heard about in quite some time. I am in the process of upgrading the audio in the S along with remodeling the basement for an entertainment center installation. I am very interested in learning more about this technology and how to use it.

One question I have involves the microphone. I see the circuit for building a pre-amp as well as the discussion involving the Radio Shack SPL meter. One version of software listed 'Corrects' (?) the SPL up to 5 Khz. Maybe the other software packages do more. I am wondering if I were to do this, which is the preferred method? I do not know if off the shelf components soldered together by me will create a combination that is better or worse than the SPL. If I could test it, I would know. But it seems that I have to 'Trust' the best method and go with it.

All advice is greatly appreciated, Thank-you in advance for your help.

 

those are some nasty peaks and dips you have there, have you considered going with an alpine pxa-h701 combo?

 

wonder how much i can get for the sercret spy photos "It's just my cell phone john" as steve walks around John's car with his camara phone

Yup and i'll bring the beers

 

What time will you be coming over? Anytime after 2 should be good, with me.

 

[QUOTE=Surreal_S2K,Mar 1 2005, 07:51 PM]
One question I have involves the microphone.

 

Microphones can be accurate, but you need to know what you are dealing with. The Panasonic capsule microphones are cheap and measure well. Here are some pages that talk about thier perfrormance. I also believe in them because when I measure my home speakers, they measure smooth and how the data sheets say the speakers perform.

http://www.gti.net/wallin/audio/preamp/preamp.html
http://orca.st.usm.edu/~jmneal/pre_meas.htm

You also need to make sure the preamp is working well. The preamp can be in the sound card or not, as long as it works well.

Something to consider is that getting the weird peaks and valleys under control is key. You can set the overall shape by ear. Want more bass? Turn it up. How do you pick up a +5 dB 1 khz peak with a 100 bandwidth? I can't hear that well enough to cancel it out.


With regards to the pxa-h701 combo, it seems like a nice unit, but I am using the head unit amps and the simplicity there is nice. It also costs more than my whole system. It looks to have a lot of the flexibility that I want, though.

What I really want is for someone to show how to load digital biquad coefficients for the filters / eq instead of relying on Alpine for the filter shapes. That is asking quite a lot for a consumer electronics piece, though.

 

Otter, I looked over more of your links tonite. I have a great appreciation for your previous work, it seems you have worked in this area for some time.

Earlier you mentioned :

I'm curious about your day job. It sounds interesting.


I will read your links on building a pre-amp again and give it a try. Will it operate just as well hard wired as on the circuit board? If so, I may do it this way. It was at least 15 years ago that I last etched a circuit board. If one is available from another source, let me know. Also, I noticed an address for calibration still listed on one of your pages. Does this exist as well?

I guess my interest spills into your knowledge of home audio as much as the S. I look forward to working on this project and hope to learn something along the way.

 

Thanks for the compliments, Surreal_S2K. I do robotics control systems in the day. Lots of frequency response work there (except phase is what you live and die by in control systems). I actually make a frequency response tool at work.

Hard wired, solder protoboard, dedicated pcb, they should all be fine. I would stay away from solderless protoboards, though. I can't tell you why they don't work, but I have made audio cicuits on them that are noisy and don't measure well. The folks that make the mitey mike will calibrate, if that is what you are looking for.

These guys make a microphone kit that sure looks interesting, though I have never used it. The price is right for what you get. No calibration that I saw. I found it
here, and they seem to like it.

Audio is fun. I have noticed that with a few tools like these it has changed from something that felt like I was designing stereos by tarot card to something that was much easier and cheaper to get good results with.

 

Ok, I ordered a HEL preamp kit. I will get it together as soon as time permits. If you want to inspect it, I would be happy to send it to you. I would be interested in the way it compares to your current preamps.

I have not downloaded the software yet. I guess the gist is to send out a given frequency while simultaneously listening to the reproduction. If so, does the system check certain frequencies or cover the entire 20-20KHz spectrum? How long does it take to do this? I would guess it might be easiest to work "one band at a time" when tuning or it might get overwelming.

Earlier you discussed the parametric equilizer limitations, but it must be better than the 'normal 7-band equilizer' I guess(?). I am curious to how 'Good' a system can get. I looked at some photos of your home speakers on the web. Would it be possible to show their graph as a basis for what good is? I am curious about home audio as well and guess this would set a benchmark to shoot for.

Thanks again for the help.

 

Thanks for the offer, Surreal_S2K. I think you should play with it, not me. The schematic is very similar to what I have, except they don't use spare parts from my junk drawer I am sure it will serve you very well.

The software uses a psuedo random output, not a sine wave. That means it sounds like white noise. It is pretty obnoxious to listen to while testing (I use earplugs), but it give you the entire frequency response in one test (< 30 seconds).

The parametric eq sure is better than a 7 band. I moan and groan about the 9835, but it's a pretty good little unit. Even better considering they can be had on eBay for < $350, new.

I find Speaker Workshop very easy to use after I remember that I have to double (not single) click on the speaker icon to get the measurement icons. I have spent half an hour figuring that one out more than once They have a pretty good tutorial here. Just remember that if you just want a frequency response, you can skip a lot of the tutorial.

Here is a quick and dirty measurement of my main speakers. It looks like the tweeter was a little hot in this measurement, and judging from the rolloff on the tweeter, something strange was going on. It isn't horrible, anyway. I'll dig up some older measurements in a while and compare.



Looking forward to hearing about your measurements.