My MTM Project

Status
Not open for further replies.
Jump to Latest
#21
Jay_WJ said:
Now I can see. This is mainly due to the RS180's unique FR. And this is a bit exaggerated in the case of your bottom woofer because the tall baffle makes it less affected by baffle step loss. The top woofer's response will be a bit better if you add its diffaction effect.

As far as I know, no existing RS180 MTM designs use a notch filter to remedy this FR rise around 180 Hz. But you can use it for your design. Try the series LCR notch in parallel with the woofers and see how much the impedance is lowered. If it's okay with your amp, go with it.
Click to expand...


It seems that the impedance goes very easily below 3ohm. With good response the lowest point is 2,5ohm, not a good design.

What do you mean by unique FR? Looking at the responses from zaph's site I don't see any major difference in rs180.

So the parallel notch filter is not a good choice because of the electrolytic cap?
 
#22
Originally posted by Twisted85 What do you mean by unique FR? Looking at the responses from zaph's site I don't see any major difference in rs180.
Click to expand...

Zaph used far field 5 ms gating for his 6.5" FR measurements. The effect of gating seems to kick in as high as 500Hz in these measurements. So you can't trust their responses even for lower midrange.

So the parallel notch filter is not a good choice because of the electrolytic cap? [/B]
Click to expand...

Try and let you ear decide. But if I were you, I'd try to voice the speakers as closely to your taste as possible before deciding to add the notch filter. (The "Voicing your speakers" section of my crossover design page might be of some help).
 
#23
If I try the parallel notch filter, does the smaller value plastic film capacitor make any good parallel with the electrolytic cap? If it does, how high value this should be?
I am guessing the resistance simulated in soundeasy is the inductor resistance and the resistor value together? And air core inductor would be better even though it has higher resistance?

And thanks for all of your help so far!
 
#25
Jay_WJ said:
I'm not sure of this issue, I mean, whether it's better to mix the two types of capacitor, though I guess it'd be better. Try what you want.
Click to expand...

I've read/heard that using plastic film capacitor parallel with electrolytic would increase the capacitor performance when high values are needed.

What do you mean by "the resistance simulated in soundeasy?" You mean R15 in your schematic?
Click to expand...

Yes
 
#29
Jay_WJ said:


Is this true for a parallel notch, too?
Click to expand...

To clarify, what I said is true for the series notch. For the parallel notch I don't *think* it includes a resistance value for the inductor. At least I've never seen a way to enter one, which is strange considering how full featured SE is. Personally I use individual components to build the parallel notch in the CAD screen, so it's a none issue for me.
 
#31
Tosh said:
Twisted85: Do you have the ability to cut away arcs from the tweeter faceplate to allow the two mid-woofers to be closer together? It adds a nice touch visually and a theoretical improvement.
Click to expand...

The woofers aren't mounted to the surface and they are aldready 5mm over the tweeter faceplate. I did this for two reasons, first more importantly the woofer acoustic center should be closer to the tweeter (in depth) as the woofers are more forward, and to get the woofers closer to the tweeter.

Few days ago I purchased parts for the parallel filter. It really did a noticeable difference, and definitely for better direction. The sound is definitely better now.
I ended up buying corobar inductors for the filter, they are a bit more expensive, but are supposed to be better than ferrite coils. The resistance is 0.22ohm.

I also tried few things with soundeasy. I made the same parallel filter as I did before, and for a comparison from separate parts, and then tried the simpler ready built filter with and without the inductor resistance added.
This is what I got:

http://koti.mbnet.fi/twisted-/soundeasy/filter_comparison.gif

The red is the separate parts. Green is the ready built with only the resistor value (0.82ohm in my case) and the pink is with inductor resistance added (total of 1.04ohm)
 
#34
Thanks. Not everyone likes the golden screws, but I think they give the speakers a more unique look.

This is how the cabinet looks without the sides:

http://koti.mbnet.fi/twisted-/cabinet1.jpg

The parts are made mainly with a cnc router.
The sides are made of four 4mm mdf put together one by one, total of 16mm thickness.

http://koti.mbnet.fi/twisted-/cabinet2.jpg

Someday I will make a homepage of all my audio diy projects to share with other people as I've always enjoyed reading about other hobbyists diy projects.
 
Status
Not open for further replies.
Top Bottom