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Old 13th May 2010, 02:01 AM   #61
doug20 is offline doug20  United States
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Quote:
Originally Posted by Lambo240z View Post
The Peavey Black Widow 15" I had. I am pretty much stuck with these, thats why they have been trying to work around them in the 3way and 2way.
Leo
That is what I thought but can that woofer really play high enough for a 2-way designs? any off-axis measurements so we can see where it dips > 6dB @ 45 deg off axis (beaming point, I believe) ?

Last edited by doug20; 13th May 2010 at 02:03 AM.
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Old 13th May 2010, 02:28 AM   #62
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by Lambo240z View Post
First, for the 2 way I will use the Fountek NeoCd2.0M as a tweeter that not only is a real good one but it also looks awesome Then later when I upgrade to the 3 way I can keep it and add the Audax PR170M0 and the final result would be really cool sounding and looking.
The second reason is that now will all the information that I learned form you guys, I am kinda curious to see the differences between a good 2 way and a good 3 way later.
Forgive for being the lone voice of reason. However it is not easy to blend a ribbon and a cone woofer together so that the results make sonic sense. The Fountek Ribbon probably needs at least a third order crossover to avoid overloading it.

Running a 15" Guitar Woofer up to 1.5KHz is asking for trouble, as it quite possibly has a very non-flat frequency response with significant resonances. One would have to have at least a decent and detailed frequency response plot of the driver available.

Even so I would see a 3-Way as severely challenging.

If you want to go 2-Way, the 600Hz capable Horn/Ribbon combo I am using in a kit speaker that will soon be released has also been tested with a 15" Woofer, though it may break your budget. For this I could give you a crossover that will work. You can have a look here:

Eureka! 100db from a 30L Cabinet - 65hz to 25khz | Diy HiFi Supply

If you really want to go that way, e-mail diyhifisupply. I know theu have stock of the ribbon/horn combo and all crossover parts.

Well, again, in the end it is your funereal, not mine. I still would suggest that the Peavey/Audax/Fostex 3-Way has a good chance to sound good without too much tweaking and has a near certainty of getting a good and working end result. The two-way would be WAY more challenging.

But please pick your poison. BTW, unless you full detailed models of the drivers that follow the actual frequency response of the drivers one should not consider the results of simulations as anything but basic feasibility studies that will tell what absolutely cannot work.

Even a full and highly complex sim with driver models that are quite close to reality tends to give useless crossover configurations two in three times, looks good on paper, sounds bad in practice.

Ciao T

PS, have a look at AMR's LS-77. I designed that, it too around 10 Different rounds of the final crossover technology and many more tries of fundamental topologies untill we had something we felt we could sell...
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Old 13th May 2010, 02:32 AM   #63
Loren42 is offline Loren42  United States
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Location: "Space Coast" Florida, USA
Quote:
Originally Posted by doug20 View Post
That is what I thought but can that woofer really play high enough for a 2-way designs? any off-axis measurements so we can see where it dips > 6dB @ 45 deg off axis (beaming point, I believe) ?
Funny you should ask! I was just working at that.

Here is the driver SPL plot. This includes the baffle step into full-space (4∏), so I'll explain that shortly...

Click the image to open in full size.

Now, here is the polar response for that driver and it explains a few things...

Click the image to open in full size.

The SPL plot shows a dip at 550 Hz. Look at the polar plot and you see that there is a transition from full-space (4∏) to half-space (2∏) and it is where the transducer starts beaming.

From that point onward it continues to build in amplitude and the off-axis response gets narrower and narrower until we hit 2 kHz and it starts to drop again.

LEAP seems to display a lot of interesting data that BassBox Pro can not. The model for the driver is right out of LEAP's driver library. I can't really say if it is 100% accurate, but I think that Vance Dickason did these measurements (I could be wrong).

If I model this in 2∏ space the lower end is a flat line, instead of dropping off. In a real room the bottom end should be somewhere in between the two.

Click the image to open in full size.

Here is the 2∏ polar plot...

Click the image to open in full size.

Interesting stuff?

I need to add the tweeter next. I'll see if I can get that modeled tomorrow, then I should be able to transition to designing the crossover if things match up.
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Old 13th May 2010, 02:32 AM   #64
doug20 is offline doug20  United States
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Join Date: Mar 2009
Quote:
Eureka! 100db from a 30L Cabinet - 65hz to 25khz | Diy HiFi Supply

If you really want to go that way, e-mail diyhifisupply. I know theu have stock of the ribbon/horn combo and all crossover parts.
That is pretty cool, I have 3 unused Neopro5is sitting around waiting for a project. I wonder if they fit ???
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Old 13th May 2010, 02:37 AM   #65
Loren42 is offline Loren42  United States
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Join Date: Sep 2008
Location: "Space Coast" Florida, USA
Quote:
Originally Posted by ThorstenL View Post
Hi,



Forgive for being the lone voice of reason. However it is not easy to blend a ribbon and a cone woofer together so that the results make sonic sense. The Fountek Ribbon probably needs at least a third order crossover to avoid overloading it.

Running a 15" Guitar Woofer up to 1.5KHz is asking for trouble, as it quite possibly has a very non-flat frequency response with significant resonances. One would have to have at least a decent and detailed frequency response plot of the driver available.

Even so I would see a 3-Way as severely challenging.

If you want to go 2-Way, the 600Hz capable Horn/Ribbon combo I am using in a kit speaker that will soon be released has also been tested with a 15" Woofer, though it may break your budget. For this I could give you a crossover that will work. You can have a look here:

Eureka! 100db from a 30L Cabinet - 65hz to 25khz | Diy HiFi Supply

If you really want to go that way, e-mail diyhifisupply. I know theu have stock of the ribbon/horn combo and all crossover parts.

Well, again, in the end it is your funereal, not mine. I still would suggest that the Peavey/Audax/Fostex 3-Way has a good chance to sound good without too much tweaking and has a near certainty of getting a good and working end result. The two-way would be WAY more challenging.

But please pick your poison. BTW, unless you full detailed models of the drivers that follow the actual frequency response of the drivers one should not consider the results of simulations as anything but basic feasibility studies that will tell what absolutely cannot work.

Even a full and highly complex sim with driver models that are quite close to reality tends to give useless crossover configurations two in three times, looks good on paper, sounds bad in practice.

Ciao T

PS, have a look at AMR's LS-77. I designed that, it too around 10 Different rounds of the final crossover technology and many more tries of fundamental topologies untill we had something we felt we could sell...
Thanks for your inputs. Maybe we should revisit the 3-way. From my initial 2-way analysis it seems that there are indeed some issues with beaming.

Your thoughts?
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Old 13th May 2010, 02:45 AM   #66
doug20 is offline doug20  United States
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He already owns the drivers correct?

How about building a 2 way passive with the mid/tweeter then a bass bin with the peavy woofer use the CX-3400 to create a simple crossover down around 300Hz.
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Old 13th May 2010, 03:16 AM   #67
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Well, I only have the Peaveys, the rest I have to buy so it can very well be the 2 way or the 3 way.
Thorsten, as I said before, I am only going for the 2way because it seems to be cheaper and simpler but if things start to get more complicated and maybe the price difference is not that much, then by all means I will try to make a 3 way as you suggested.
I think that is better to explore all possibilities to make sure everything goes as smooth as possible when I get to build it.
As Loren is saying now, maybe with the new calculations, things may show that a 3way could be the solution, I dont know.
As they say, 2 heads thing better than 1 and your 2 heads know a lot about this so...
Thanks again guys...
Leo
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Old 13th May 2010, 06:15 AM   #68
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by doug20 View Post
That is pretty cool, I have 3 unused Neopro5is sitting around waiting for a project. I wonder if they fit ???
Not in that design.

Ciao T
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Old 13th May 2010, 07:33 AM   #69
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Hi,

Quote:
Originally Posted by Lambo240z View Post
Thorsten, as I said before, I am only going for the 2way because it seems to be cheaper and simpler but if things start to get more complicated and maybe the price difference is not that much, then by all means I will try to make a 3 way as you suggested.
Okay, to give a little more reasoning, as to why I think the 3-Way as suggested is a better choice:

1) This kind of speaker exists and is used in both PA and Studio Applications, pretty much for the last two decades, with similar horn tweeters and 15" Woofers complementing an Audax PR170M0.

The german Klang & Ton Mag had a design using all Audax Drivers (15" Audax pro Woofer, the earlier version of the PR170M0 and a horn tweeter not very different in nature to the Fostex), all with a 2nd order crossover at 500Hz and 5KHz.

2) One key determining factor in speaker sound in room is the off axis response. A 15" Driver will not do too well at higher frequencies, on the other hand the Ribbon will have a very wide dispersion just above the crossover. This means the off-axis response will be quite non-flat and the speaker will not sound well balanced, no matter what on-axis response simulations predict.

On the other hand the Audax Driver will match the off axis response of the Woofer quite well and will show an ever narrowing dispersion as frequency rises and it does so quite smoothly and the Fostex horn tweeters dispersion dovetails well with the Audax driver.

The net result is a speaker with a pretty flat on axis response and a response that smoothly falls off the more with rising frequency the more we move off axis. So the overall sound will be a little "warm".

3) Using (as I suggested) first order filters only means you have some leeway for errors. First order crossovers placed in an essentially linear frequency range of both drivers almost always work okay (unless grossly messed up), the higher order the crossover the larger the chance for things to go badly wrong.

So, I repeat, a basic 3-Way with your woofer, an Audax Wideband/Midrange and Fostex Horn Tweeter (mainly selected for low cost) with first order crossovers at around 400Hz and around 8KHz will actually give you a working speaker with a great likelyhood of sucess.

It may be in the end less good as the 2-Way with ribbon and all IF that speaker is gotten right "just so", but the likelyhood of getting it "just so" is small, unless you have a lot of experience, decent measurement gear and a lot of time.

You probably also would need to construct a waveguide for the Ribbon to control it's excessively wide horizontal dispersion which in turn usually means you need to restore the frequency response to flat by equalisation.

Trust me, it is not trivial. A 2-Way speaker looks easier, but that is only the case if you have a classic "2-Way" with a crossover at 2-4KHz and even these are not that easy.

My suggestions for a woofer enclosure BTW would mean a box of around 150 Liter in the golden ratio (seems around 90cm X 55cm X 38cm interior dimensions would seem okay) tuned to around 40Hz.

I would recommend a single slot port 35cm wide, 10cm high and 28cm deep at the very bottom of the box. This will give around 40Hz tuning.

I would as said place the Audax into an enclosure of maybe around 15 liters and I would "vent" this chamber with 4 holes of around 3cm diameter and box wall thickness. However I would fill the chamber with stuffing and use felt layers over the vents. This will damp the resonance quite well. This can be tested using a Multimeter and a PC as signal generator. Then a single higpass capacitor can be used.

Maybe around 47uF & 3.3...3.9mH could work okay in the ballpark (in part to offset the rising midrange response of the Peavey woofer, add 8.2 Ohm and 10uF across the Peavey woofers terminals to compensate the rising impedance.

For an idea of how such a system may be assembled, look here:

Kenwood LS-1900 on TVK

Ciao T
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Old 13th May 2010, 10:55 AM   #70
Loren42 is offline Loren42  United States
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Join Date: Sep 2008
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Quote:
Originally Posted by ThorstenL View Post
Hi,

Okay, to give a little more reasoning, as to why I think the 3-Way as suggested is a better choice:

Ciao T
After sleeping on this I am warming up to the 3-way design, too. My concern is the response curve for the Peavey at and above 500 Hz.

I use the Audax PR170M0 in my own 3-way, so I have actual acoustic data at my command.

Where my thinking diverges is with the execution. Here are my issues:

1. I think the woofer enclosure should be tuned to 58 Hz. Reasons:
a. He intends to use a sub that he already has, so 58 Hz yields the maximally flat response.
b. 40 Hz will have an F3 well over 100 Hz and drops quickly after that. The sub should be able to manage with a higher Fb of 58 Hz.

2. I would not vent the Audax. You just don't need to. I cross my Audax at 400 Hz in a sealed .25 cubic foot box and it works perfectly. I can't see what would be different here if we choose the same crossover frequency.

Again, I would also worry about Xmax for the Audax in a vented enclosure, particularly for a first order filter. Have you looked at that?

Somewhere, I remember seeing a rational as to why it is generally not good practice to vent a mid, but if you have a compelling argument as to why in this specific case that makes sense, I would welcome hearing it. I was not able to model that specific configuration.

By the way, I appreciate your inputs!

Leo, can you give us details of the sub you have? That would help since it is going to be part of the system.

Last edited by Loren42; 13th May 2010 at 10:58 AM.
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