WWMTM project

[rinx]

Hey all!

Fisrt of all have to tell you that my english is not yet the best but I try to get better
I am so far with my enclosure for WWMTM project that I am going to do a filter. So I know that everybody here dont have unlimited time and sometimes its easyer to tell-do your homework before coming to ask here. Well I have done so far homework on DIY field as posseble, but what is most harder for me is doing a filter. I am not so good in such techikal area, sometimes they say its mix from art and knolidge.
So, what I am looking is that somebody just can delve into my project.
I will give you information as much as posseble to make best decision. Most important is form me XO points and do I need to use notch or other things in filter.

Here is speakers I am using:
http://www.partsexpress.com/pdf/295-366g.pdf
http://www.hautparleur.fr/_audax/am130z2.jpg
http://www.madisound.com/catalog/PDF/seas/h881.pdf

Best regards from Ringo

[BlueWizard]

I'm not an expert in this area, I readily admit that.

Your woofer and tweeters look reasonable, but I'm not sure about the Midrange (Audax AM130Z2). It seems very good on the low end, but not so great on the high end. It doesn't look like it will crossover much higher than 2000hz or at the most 3000hz. That is probably a comfortable place for the Seas H881 tweeter, but it is at the limit of the Audax Midrange.

Of course, this is just my limited opinion.

I think (again limited knowledge) that the woofer has to crossover low; 800hz or below.

Fortunately, your Midrange has a very low resonance and looks flat down to about 150hz to 200hz.

There are many other things to consider, but on a superficial analysis, I would say you could crossover Woofer-to-Mid any where in the range between 350hz and 800hz.

On the high side (Mid-to-Tweeter), I don't think you can go much higher than 2000hz to at the most 2500hz.

For the moment, I'm assuming 12db per octave crossovers, but if you need to push you Mid up higher, then you might want to consider 18db/octave.

I'm not saying 'Do This', I'm merely saying, in my limited opinion, these are the working ranges you have.

Whether these are practical ranges, I don't know. I have seen commercial ready-made crossovers that crossover at 375hz/3000hz, 500hz/4000hz, 625hz/5000hz, and others. These seem to be trying to maintain a 3 octave range across the midrange.

That is about the limit of what I can say. I would suggest finding some Crossover modeling software, and trying various crossover points and slopes, and see which works best.

Steve/bluewizard

[rinx]

Good job!
But yes unfortunately I dont have such technical knowledge about doing really good filter + right now dont have equipments to measure speakers or whole system.
I have some software, like SpeakerWorkShop and LSPCad, but again I am lack of knowledge. In our language there is not enough material also to read.
Kind a trouble

[BlueWizard]

Have you already purchased your speakers, especially the Midrange?

If you change to a different midrange, you might be able to make this work.

You could consider a Tang Band full range for the Midrange speaker. You can pick anyone you want but these two might do the job -

Tang Band W3-879SC 3" Shielded Driver (264-810) $19.25 each

Tang Band W4-654SE 4" Shielded Driver (264-816) $20.28 each

http://www.partsexpress.com/webpage....ctGroup_ID=576

You might want to consider the -

Dayton DC50F-8 2" Dome Midrange (285-010) $31.96 each

http://www.partsexpress.com/pe/showd...number=285-010

My guess is that it is good from about 600hz to 800hz on the low end, to about 4,000hz or at the absolute most 5000hz on the high end.

As to Crossovers, you have a complication in that you are using TWO woofers, presumably 8 ohms each and presumably wired in parallel. That makes your woofer section 4 ohms, while your Mid and Tweeters are 8ohms. Not a problem if you are designing your own crossovers, but difficult for ready-made crossovers because they are usually designed assuming one impedance across low/mid/high.

One option would be to get 4 ohms woofers (Dayton makes them) and wire them in series for 8 ohms total. Another option, is to get Dual Voice Coil woofers (again Dayton makes them as well as others) wire the voice coils series for 16 ohms, then wire the woofers in parallel for 8 ohms.

These things are never easy.

Steve/bluewizard

[rinx]

Well, the thing is that I already have all those speakers. I have read about Audax a very good feedback, some people say they are one of the top midrange speakers, so thats why I wanted to use those and see how they sound.

One thing I would like to know is about phase, what I should consider in that case. What I should look about phase and does filter change phase?! and so on..

[rinx]

By the way:do you think I can go even lower with woofer-mid xo-point. In my case i need to go low as posseble, because woofer is side of the speaker. So what could be lowest I can go?

[tinitus]

Woofers on the side ?? That changes a lot of things ...you need an active sub plateamp fore that

Skip the MTM configuration and make a MMT ... make the xo 2.5way

Audax midbass looks ok to me...should work with a quite simple xo

[BlueWizard]

Regarding Low Bass/Mid crossover being low, it hinges on the midrange and tweeter you have. If you crossover low, that lowers the Mid/High crossover as well which makes it easier to find a Midrange but harder to find a Tweeter. It also hinges on how you define 'Low', do you mean 150hz low which is common in Subwoofers, or do you mean 500hz low, which is low for a standard 3-way design, or do you mean 350hz low, and again, can you find speakers to sufficiently span the necessary range?

Also, you say THE woofer is on the side, but your design has TWO woofers, are one or both of them on the side? If one is on the side, you might want to configure them in a Sub (side woofer), Mid-Bass (front woofer), Mid, and Tweeter combination. That complicates things, but is frequently done.

When you are shopping for speakers, you can't just go by the rated frequency response. A quick look at the Frequency Response Chart will tell you that specification can't be trusted. If the Frequency Response graph has high end peaks, as you commonly find in aluminum woofers, then you are going to have to stay away from those frequencies. You are going to have to crossover low or with a very steep slope or insert a filter specifically to reduce those peaks to make sure those peaks are sufficiently attenuated when you reach that frequency. Others have recommended to me that I leave a 3 octave gap, actually it's 36db attenuation, between the crossover and the trouble frequency. Again, this isn't a hard and fast rule, just a quick and easy guideline. So, as in the Daytons, with a peak at 7khz, you are going to have to crossover at 875hs or lower with a standard 12db/octave crossover.

Your Mids are easily going to have to functionally span the gap between where your woofer ends and your tweeter begins. As a general rule, you want to cross your tweeters over well above the resonance frequency of the tweeter. Most recommend 2 octaves above the resonance, but that's not an absolute rule, just a guideline. If you understand crossover design, you can crossover closer to the tweeter resonance, but in general, you want to stay away from it.

For both Midrange and tweeters, the listening field, or off axis response, will start to narrow as the frequency goes higher. For Mids, you want to stay out of this area as much as possible, that limits the available high end response of the Mids. Tweeters will frequently have a peak or a drop as they approach the 10khz to 20khz range. You need to decide if you can live with those inconsistencies as they are or whether you are going to have to compensate for them in the crossover design.

This is what makes choosing speakers and designing crossovers such a complex process. It is not as simply as matching speaker by their rated frequency response. You really have to study the Frequency Response and Impedance graphs and pay attention to dips and peaks as well as off axis response.

Hope that helps.

Steve/bluewizard

[Corax]

For experience sake and to figure out the phase realtionship (besides other things) I always build cheap separate enclosures with the correct (and calculated) volume for each involved chassis. This way you can shift them back and forth until the phase relationship (distance from the listening position) is perfect. Of course you need a preliminary version of the cross-over before you start this task. You'll see later on that changing the position will have an influence on the cross-over and vice versa. Further changes to the cross-over etc. are more likely to happen.
Another hint: make the enclosures as flat as possible in particular when using an MTM arrangement (D'Appolito setup). Then stack them in the order you had in mind - i.e. WWMTM, WMTMW, ...

That's so far the basic setup as a starting point for any measurements.

The pitty is that you don't have (according to your own words) any measurement equipment at all. And right here IMHO ends all your efforts because of lack of an appropriate equipment .

You desperately need some sort of audio measurement hardware and/or software .
Without - it might be a painful trial and error method just based on hearing experiences and the result is more likely to satisfy only you and nobody else.

[rinx]

Well, yes I have two woofers on side.
I am thinking that I should go approx 250hz, can I do that and will keep Mid/Tweeter XO approx. 2000-2500.
So then I should do first filter and start looking how well is my target? Also phase track, and when its not good start modifying filter?!


By the way, why I need active sub plateamp?! And if I am doing WWMMT, and MMT 2.5 system, then I am gonna have 3 XO points?!
1) Woofers/first mid
2)first mid/second mid
3)second mid/tweeter

My enclosure is pretty much done. Why I decided to put Woofers on side, is design, because I wanted front baffle to be narrow as posseble, and right now it is 20cm with lenght 145.
I am gonna do something like that:
http://www.audes.ee/?id=1840&tpl=1020

I have heard those, they sound OK, nothing really special. I think I can do better than those, because the speakers I use should be better (distortion and sound).
I have some software-SpeakerWorkshop, plus I bought Behringer mic to measure speakers. But I still feel that I am lack of knowledge how to create a good filter and how to chose speakers that will work together really well.