Friday, September 21, 2007

Information from the person himself!

Perhaps the best method to find out the crossover frequency and slope is to talk to the designer himself! I sent an email to Mr. Skannings and here is his response

"Yes, you can easily cross the drivers at 3000 Hz - no problem.The 96 dB/Oct filter is really a tough filter. We are used to 6, 12 or 18dB/Oct filters, and have never heard of anyone using 96 dB/Oct filtersbefore. When you use filters with a such high order, there will come absolutely no information from the drivers as soon as they pass the x-overfrequency. It might be, that you need some kind of energy from either tweeter or midrange when using the high order filter and we agree that it might be an idea to move to a less order type. Rising the x-over frequencyto 3000 Hz might also help, as it will give your tweeter better working conditions."

Following his advice and the advice on the diyaudio forum, I tried these settings as a starting point

Tweeter: 3000Hz up
Mid: 200 - 3000Hz
Woofer: 200Hz and below

The results is a much more dynamic mid to midbass. The human voice has got more muscle and more emotions. The high is just as crystal clear. The next thing I will try is to crossover to the W210 sub, probably at 60Hz.

Wednesday, September 19, 2007

My speakers

After all these digital crossover and room correction stuff. I think I have forgotten to write about my speakers!! My new speaker is actually a DIY speakers from a local company. Over the years, I know the cheif designer very well and we are good friends. He said he can design a speaker for me based on the drivers he has but I need to work on the crossover! Not problem. I like the challange and so the project started! The design was actually a TMW design and when he gave me the outlook of the speakers, I was really thrilled! It was so beautiful!!

I took awhile to find a factory to produce the speaker case as we only made 2. We eventually managed to find one and a few months ago, my dream speaker came into reality. So which drivers did we chose

Tweeter - Raven 2.0
Mid - Audio Technology 15cm
Woofer - Audiotechnology 23 cm
Sub woofer - Tact 210

When I set it up initially using digital crossover and all that, I chose the following slope and frequency

Tweeter: 2000Hz up, 96dB/Octave
Mid: 350Hz - 2000Hz, 96dB/Octave
Woofer: 150Hz - 350Hz, 96dB/Octave
Sub: 150Hz below, 96dB/Octave

The sound? Well, not bad, the details are great, and the highs are excellent. but the mid is kind of lifeless, not involving and flat. The bass are good but can be better with these drivers.

Then I came across this thread again. I got the recommendation as follows:

"Hi again Arthur,

It sounds like your system is basically the LGT but in slimmed down TMW form. At least from a driver perspective anyway.The thin midrange problem I was having and which you seem to be relating to was due to some over excessive stop band correction which Uli fixed and showed me how to avoid. Before making any changes are you sure you haven't fell into this trap also?

During this project I made a few discoveries about the RAAL ribbon which will very likely apply to any ribbon. I'm not sure about dome tweeters but their dead and lifeless nature means it probably doesn't matter how they're used, they'll still sound unnatural. Dome tweeter jokes aside, if I crossed the RAAL low at 1.5Khz it simply sounds wrong in comparison to what I have now. You lose the presence and body of the upper midrange/lower treble and this is true despite very similar measured performance. Perhaps it is odd high order harmonic distortion from the ribbon being crossed low? Perhaps it is a mass/radiating area issue? I'm not 100% sure about either but I can say it doesn't sound as good. Try the Raven at 3Khz, since your crossing to the 5" the narrowing directivity of the mid driver will improve overall power response and better mate the directivity patterns of the two drivers at the crossover points. I assume you mid and tweeter spacing is close here.

I would try to abandon the steep filters for use with AT drivers, it harms the sound more than it helps. They're wideband and smooth at both ends so why create a problematic solution to an issue that doesn't exist. Its best to evaluate on the basis of each case and go for the lesser of evils approach. For example I found steep filters worked well with the ATC midrange but this was actually beneficial because I was running it right upto its upper and lower limits where resonanaces and distortion, respectively, became an issue overiding negatives surrounding steep filtering.In this instance I chose 24dB LR slopes and it really does suit the AT's offering a good blend of stop band rejection, lessening driver to driver crossover stopband interaction along with promoting a more cohesive sound from drivers more effectively blending creating less of a sense of shifting directivity lobes and tonality. By this I mean with steep filtering the drivers can become more subjectively isolated and I find I can tell a shift of sound direction and tonality when different frequencies, covered by different drivers, are playing. A bit more crossover overlap from shallower filtering can create a more cohesive speaker and we are lucky that we can make the drivers behave optimally to virtually eliminate the phase problems from doing so.

You've also got a lot going on down low: A sub crossed in at 150hz to an 8" driver that then works to 350hz. I haven't heard your system so can't say whether it works and maybe you have preference for this setup but looking at it on paper its less than optimal IMO. Personally I'd shift the mid down to 200hz which allows it to cover yet more of the frequency range, it works excellently in my setup where I tried it at 500hz, 300hz, 200hz and 150hz. 200hz had the best blend of mid/upper bass weight and seamless integration out to the midrange.

For the 8" I'd use this with just a low pass and no high pass then bring the sub in at non directional frequencies to blend with the overall sound and fill out the low end. Reason being the sub will be some distance from the main driver array and at 150hz sound is directional. Crossing in at say 50 or 60hz is much better.

These are just my thoughts on how I'd do it and not everyone agree's on how things should be implemented but since your not 100% happy with the sound and we also have similar drive units then I think some of the ideas might be worth looking at."

Sounds very reasonable. I will try this setting and report back!

Wednesday, September 12, 2007

Further updates

When I first setted up the system, I do not have a line level volume control. Everything was done with at the digital domain with the HTPC. I am lossing resolution. To bring the listerning level to acceptable, I have to attenuate about 20dB. Not good. I have since then sourced a line level 8 channels volume control for studio use. So far I am very happy with it.

I also came across another persson using the exact same software on digital crossover and room correction that I am using but expalin it better. So I though I should post the link. He has also DIY a great speaker!!