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Discussion Starter · #1 ·
Hi All,

I'm thinking outside the box a little for my next project, a curved baffle centre channel.
After searching this forum for curved baffle speakers, the only thread that came anywhere near to what I want to do is the wine barrel subwoofer by Mark DN, but it's the barrel that's the common component only.

I've read in many articles that a curved baffle has many advantages over a flat baffle, so I'm putting it out there for discussion.

I've attached a pic of where I want to go, but my main question is whether to go convex curve to aid dispersion, or concave curve do help with directivity?
My next issue is how I'm going to router the driver holes in a curved surface. Am I mad? probably.:bigsmile:
 

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That certainly is a challenge. You will need to make a jig to route the level flat unless you have access to a friend with a CNC router. :bigsmile:
As for convex\concave If you had an MTM arrangement either should work ok.

It is going to be interesting to see how you progress.
 

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Awesome idea. It will be pretty awesome looking if you can pull it off. My vote is convex!
 

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Discussion Starter · #4 ·
Hi All,

Here's a pic of the first pieces being glued together. Six pieces will be used to make up the baffle.

I have a question about the drivers and placement. My current centre channel is MMTMM with the outer woofers crossed at approx. 800Hz for better low end. What I want to do with the new design is to have just an MTM on the front baffle and use the extra two mid woofers as rear firing. Will this work?
 

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Definitely a challenging project! Kudos for taking it on. Not only do you have to deal with the curve in one direction but two (the bend along the axis of the barrel and the circumferential bend!) This is a really cool build :T
 

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What I want to do with the new design is to have just an MTM on the front baffle and use the extra two mid woofers as rear firing. Will this work?
That shouldn't be an issue depending on the depth of the cabinet and the crossover frequency.
 

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Discussion Starter · #7 ·
Hi Everyone,

Here is the latest update. I have managed to assemble and glue the baffle, and have just sanded it smooth.
I've included a few pics to show progress.
Now I need some help? I have a few options with regard to drivers for this project. I'd like to use the existing drivers out of my current centre channel in some sort of way, but I'd also like to really enhance the lower octaves. The drivers I have available are: 4 x CW2194 6.5" mid bass drivers and 2 x 10" infinity kappa KSC100BR drivers. What do you guys reckon?
The front baffle is 90cm wide and 32cm high, the depth is only limited by entertainment unit but that's 50cm, so I could make a rather large box if necessary. I've added a pic of a design I was thinking about to aid in vertical dispersion. Comments please?
 

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If you want to enhance your low end, then sure build a sub with your Infinity drivers you have. That seems like a separate project from your center to me and I wouldn't suggest building a sub into your center.
 

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If you want to enhance your low end, then sure build a sub with your Infinity drivers you have. That seems like a separate project from your center to me and I wouldn't suggest building a sub into your center.
I would agree also, use the 6.5 inch drivers. I would suggest you model the 6.5 as a MTM setup. Two of these drivers in parallel in a vented 40 liter enclosure will nett you a box tuning frequency around 42 Hz which is way lower than you need in a mid if you run a sub.

I use these drivers in vented enclosures a a mid-range speaker in my HT mains. They work very well as the main driver or as a mid.

To fit them I would partial route the flange recess as the curve will be flush at the mid points and the flange exposed at the other points. Option two would be to bury the flange completely until the highest point is flush with the surface of the baffle, but to me that would look somewhat ugly in appearance, although if you intend to have a grill that's not such an issue.

That then leaves your 10inch drivers for a nice little sub project :)
 

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Meet the family

Aria HT's at center with Aria2 on the right and the Aria Pettites left.



And with their clothes on :)



Some of you will recognize the Jaycar drivers. The HT's use the CW2194 for a mid and the CW2196 for the bass driver. With this setup I dont run a sub, it isn't necessary, in fact the family complains about there being too much bass at times. You can also see the CT2007 tweeter. Its a Vifa OEM clone and its a good unit, but it needs an L-Pap and a contour filter as it has a rising spl in the 15000 to 20000 kHz range of 5 dB that needs to be smoothed out before the L-pad is effective.
 

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Discussion Starter · #11 ·
Re: Meet the family

Aria HT's at center with Aria2 on the right and the Aria Pettites left.



And with their clothes on :)



Some of you will recognize the Jaycar drivers. The HT's use the CW2194 for a mid and the CW2196 for the bass driver. With this setup I dont run a sub, it isn't necessary, in fact the family complains about there being too much bass at times. You can also see the CT2007 tweeter. Its a Vifa OEM clone and its a good unit, but it needs an L-Pap and a contour filter as it has a rising spl in the 15000 to 20000 kHz range of 5 dB that needs to be smoothed out before the L-pad is effective.
What crossover frequency did you end up using for your centre channel?
I already have a sub. It's the frequencies in the 80-400 range that I want to enhance, the region of baffle step roll off.

As I already have my main towers with SB Acoustics drivers, I want to keep the tone similar. My current centre channel that is pictured above, uses the drivers out of a Todds Auditone centre channel and an extra pair of Vifa M13SG drivers. Sounds good already but it gets serious lobing when you sit off centre and the vertical dispersion is limited. I wanted to expand the vertical dispersion by using the configuration in the last pic. I want to see if a 3 way system will work, 4 x CW2194 drivers rear firing, 4 x mids and a tweeter on the front baffle. That being said, if I use the 5" drivers for mid range only, could I get away with an open baffle? and have a box behind the baffle for the mid bass drivers? I want to get around the excursion limits of the drivers by using multiple units.
 

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Re: Meet the family

As my amp allows me to adjust crossover frequency for the sub from 40 to 120Hz I settled on 100Hz for the centre as its more important ( at least in my set-up ) that the vocal range and a little below it is well covered right through to 4000khz where the tweeter crosses over.

I used two 5 inch CW2192 in parallel for my centre speaker and used a KEF T-33 tweeter for the top end.
The CW2192 turned out to be good performer covering 70 Hz to 7000 kHz
 

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EG9,

I really like the creative use of the barrel pieces for a front baffle. That is going to have some real character. Very neat idea indeed! Mounting is going to be a real trick!

----------------------------------


I'd like to take this opportunity to encourage anyone following along here to download a free simulation program called "edge." Edge is a simulation program that simulates the diffraction effects, as well as the effect of driver size, number of drivers, and listening position, on the response.

With a little math on paper one could easily determine the lack of suitability of most horizontal MTM configurations by just considering the wavelength size as one approach's the crossover to the tweeter, and consider how little horizontal axis rotation is required to move the 2 midbass drivers out of phase. However, allowing "edge" to simulate the effect is much more stimulating and motivating because it produces a charted response revealing the magnitude of the problem with greater clarity.

  • Use "edge" to make a baffle to work inside of. (doesn't need to be exactly like yours, just similar dimensions).
  • Set driver quantity to "2."
  • Set the speaker "size" to the diaphragm diameter in the speakers used.
  • Set the center to center distance to match a real world configuration, (make sure to actually calculate it, visually the speaker diaphragm size alone will appear smaller in the simulation than the entire speaker does in real life, which can lead to spacing that is guesstimated to be much closer than is possible. Set the actual center to center distance in the design intended or built.)
  • Set speaker source density to ~6-10
  • Set the microphone on the center axis.
  • Adjust the mic distance to match the distance to ear position at the "center" seating position.
  • observe response
  • Move microphone horizontally to positions representative of people sitting a seat over, then 2 seats over.
  • observe response.
Note: the person sitting right NEXT to the "center" seating position is missing nearly an entire octave of response if the crossover is set in a traditional ~3K range.

--------------

For center channel designs with limited vertical space, I think it's hard to beat a WTMW configuration with the "TM" in the center arranged vertically. The Morel CAT 558 (MDM 55) comes to mind as a good midrange unit with the sensitivity and dynamic reach for a center channel. Crossed to one of the small flange neo tweeter options (like the little dayton/aura 3/4" rear-mounting units) ~4-5K, then flanked by a pair of midbass drivers and crossed ~500-750hz.

An approach like I have described extends the usable horizontal axis to involve basically anyone in the room. Nobody will be missing entire octaves of response at their seating position.

-------------
 

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Discussion Starter · #14 · (Edited)
Thanks mdocod.
Have you had a look at my pic with regard to my proposed design for this build. I think it will end up like a large coaxial speaker with the added advantage of better off axis response due to the curved baffle.
I will have a look at edge software. I have been using the excel spreadsheet programs to simulate baffle diffraction and step, along with response modelling and crossover design.
Nothing can really simulate a curved baffle. I'm going to have to make another baffle to use for testing purposes.
What does everyone think about my design with four drivers surrounding the tweeter?
 

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Hi EG92,

The curved baffle will help adjust the directivity of the baffle diffraction, which may help breakup up the primary baffle response peaks to a slight degree. In reality it's not going to be a major player in solving off axis issues especially considering that center channel speakers are so often cluttered into a space with so many other diffraction boundaries that the shape of the center channel box is going to serve primarily as an aesthetic fulfillment, not an acoustic solution.

Here's a simulation of some 6.5" drivers on a baffle in a configuration that would fit a traditional flange size dome in the center of them...



listening position is 22 degrees off axis. Total cancellation occurs at ~2300hz on midbass drivers. Crossover would have to be very low (~1600hz?) to maintain "usable" response even at just 22 degrees off axis. Move to 45 degrees off axis and the cancellation is centered at 1300hz. (there is no crossover point that can solve this to a traditional dome tweeter).

A good center channel speaker should not "drop" any of the mid-range within a ~ +/-45 degree or better horizontal axis. Some designs shoot for +/-60 degrees of usable off axis response.

Regards,
Eric
 

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Discussion Starter · #16 ·
Thanks Eric.
Would a wide baffle be of any advantage? The current baffle width is 90cm, height is 32cm. I'm toying with different designs at the moment, trying to find the best one. My other option would be go three way and use 2x6.5" mid bass, 2x5" mid, and a good tweeter. Put the mids under the tweeter in the centre and find a good place for the mid bass drivers.

Cheers Jason
 

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EG9,

I really like the creative use of the barrel pieces for a front baffle. That is going to have some real character. Very neat idea indeed! Mounting is going to be a real trick!

----------------------------------


I'd like to take this opportunity to encourage anyone following along here to download a free simulation program called "edge." Edge is a simulation program that simulates the diffraction effects, as well as the effect of driver size, number of drivers, and listening position, on the response.

With a little math on paper one could easily determine the lack of suitability of most horizontal MTM configurations by just considering the wavelength size as one approach's the crossover to the tweeter, and consider how little horizontal axis rotation is required to move the 2 midbass drivers out of phase. However, allowing "edge" to simulate the effect is much more stimulating and motivating because it produces a charted response revealing the magnitude of the problem with greater clarity.

  • Use "edge" to make a baffle to work inside of. (doesn't need to be exactly like yours, just similar dimensions).
  • Set driver quantity to "2."
  • Set the speaker "size" to the diaphragm diameter in the speakers used.
  • Set the center to center distance to match a real world configuration, (make sure to actually calculate it, visually the speaker diaphragm size alone will appear smaller in the simulation than the entire speaker does in real life, which can lead to spacing that is guesstimated to be much closer than is possible. Set the actual center to center distance in the design intended or built.)
  • Set speaker source density to ~6-10
  • Set the microphone on the center axis.
  • Adjust the mic distance to match the distance to ear position at the "center" seating position.
  • observe response
  • Move microphone horizontally to positions representative of people sitting a seat over, then 2 seats over.
  • observe response.
Could you post a link to that software, I'd be interested in having a look at it.
 

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Discussion Starter · #20 · (Edited)
Edge is a great program. Used it tonight. Thanks Eric
With my baffle dimensions I can manage 2 x 5" mid drivers in the lower centre of the baffle, tweeter mounted above directly in the centre, 2 x 6.5" mid bass at the outer edges of the baffle.

My next issue will be how I'm going to mount the tweeter. Being a curved baffle and the tweeter mounted directly in the centre, it's going to require a waveguide or something to recess it to the same depth of the woofers. Acoustic response is important. It seems many things come to the surface when working with a curved baffle.

Jason
 
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