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Fane 12" Mids w/ dual modification

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mellotone View Drop Down
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    Posted: 27 April 2017 at 9:58pm
hello,

Starting a dual 12" cab build this weekend with a slight modification I had in mind based on an existing standard design and therefore wanted to share it out to see if there are any issues I haven't considered or that may prove to be problematic.

Basically I'm building the uber simple Compact Reflex Cabinet (51L tuned to 55Hz) for a single 12" from the old Fane book but I want to combine two cabinets into one like I've seen many people do with the 18" 200L reflex build.

So here's the Fane plan I'm referencing:




and here's the basic idea I had in mind for combining two of these into one cab:


FYI: The space in between the two 12" cutouts is a cosmetic detail and not intended for any type of driver. Also, in the side view the additional space added to the back was just to add depth.

I'm planning to load each with some new Fane Colossus 12MB I have to cover a rather large range of 100Hz to 1.6kHz and live above my 4 Colossus Studio 18B (400W versions) and below my 2" EV DH1a compression horn. 

Any issues I should be aware of here?
Should I scrap the idea completely?
Thoughts on whether or not to use damping material in these?
The plans doesn't appear to call for support bracing but I was planning on adding it in, I know that will reduce my internal volume some but not sure if it will be enough to cause issues.

Any help is appreciated and many thanks in advance.


Edited by mellotone - 27 April 2017 at 10:02pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote darkmatter Quote  Post ReplyReply Direct Link To This Post Posted: 28 April 2017 at 1:35pm
Not sure I'm reading the plan correctly - do the drivers share the rear chamber?

Have you modelled the driver in this cab in WinISD?

Assuming the drivers shared a chamber, my only suggestion would be to make the bit of wood for the port slightly longer than 3.5" so that you can tune it once you've built it.

Re. bracing - you can always cut holes out of the brace panels so that you can maintain rigidity without impacting internal volume too much.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mellotone Quote  Post ReplyReply Direct Link To This Post Posted: 28 April 2017 at 2:51pm
Originally posted by darkmatter darkmatter wrote:

do the drivers share the rear chamber? Hmm, by rear chamber are you referring to the additional depth I added to the side view of my sketch? Apologies for the quality of the scan.

Each driver would be contained in it's own 51L box with it's own port at the bottom (like shown in the first page/image) and would simply be placed side-by-side within a larger cab. That larger cab might have additional depth added to the back which would run the length of both boxes and yes would be a shared space.

Have you modelled the driver in this cab in WinISD? Have not yet, was planning to run that this evening.

Assuming the drivers shared a chamber, my only suggestion would be to make the bit of wood for the port slightly longer than 3.5" so that you can tune it once you've built it. Prolly a good idea anyways, thx.

Re. bracing - you can always cut holes out of the brace panels so that you can maintain rigidity without impacting internal volume too much. Yep god call, am thinking a single brace running side to side or top to bottom should be sufficient. Thx.




Edited by mellotone - 28 April 2017 at 3:18pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote colinmono Quote  Post ReplyReply Direct Link To This Post Posted: 28 April 2017 at 5:41pm
Might be worth having a look at Fane's newer plan for the Colossus 12MB

https://www.yumpu.com/en/document/view/50764896/constructor-series-2-way-trapezoidal-12-reflex-fane

I'd arrange your drivers vertically rather than side by side, to reduce comb filtering problems.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mellotone Quote  Post ReplyReply Direct Link To This Post Posted: 28 April 2017 at 7:24pm
Looked at that plan but (even though that one was design specifically with the Col 12MB in mind) decided to try something a little different.

Yeah, there was another thought I had concerning potential for comb-filtering but rather than stacking vertical I was thinking setting each at an outward angle of @ 9º- 15º could be helpful.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2017 at 1:06am
Originally posted by mellotone mellotone wrote:

Looked at that plan but (even though that one was design specifically with the Col 12MB in mind) decided to try something a little different.

Yeah, there was another thought I had concerning potential for comb-filtering but rather than stacking vertical I was thinking setting each at an outward angle of @ 9º- 15º could be helpful.


By trying something different, you will have to confirm through WinISD or any other loudspeaker simulator if the drivers you plan to use will work as good in the older Fane cabinet compared to newer cabinet designed for your loudspeakers.

Comb filtering applies mostly to wards high frequencies.

Best Regards, 

Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mellotone Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2017 at 5:36am
Ran it through winISD and it appears to check out, however tuning the cab from 55Hz to 68Hz yields a much flatter response.

Yes Elliot, planning to x/o @ 1.6kHz so hopefully avoiding comb effect.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2017 at 1:47pm
Tuning is the easy part for you can always retune the box if the sound is not to your liking.

Best Regards,

 
Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote darkmatter Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 2017 at 3:54pm
Originally posted by mellotone mellotone wrote:


Each driver would be contained in it's own 51L box with it's own port at the bottom (like shown in the first page/image) and would simply be placed side-by-side within a larger cab. That larger cab might have additional depth added to the back which would run the length of both boxes and yes would be a shared space.


In my view, they don't need their own separate 51L boxes. I think they can share a chamber, meaning you reduce weight, build complexity and external volume while maintaining the same internal volume.

If you're trying to reduce comb filtering, your probably want to reduce the distance between the acoustic centres of the drivers.

Remember when modelling port lengths that if the port uses the cabinet wall as one of it's boundaries, the length the driver sees may be slightly greater than the 'A' distance shown on the Fane plan.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mellotone Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2017 at 7:02am
Agreed, separate boxes certainly not needed. 

The thought was given the parameters/performance I was looking to achieve (100Hz -1.6kHz) and the recommended volume for that specific driver (ported enclosure between 25 - 80L) that I would be best suited going with a simple/proven enclosure design and doubling it. 

I wasn't able to locate an existing plan of a single chamber dual 12" design that gave me enough confidence to match with this driver and deliver the performance I'm after, if one exists I'd be very interested if anyone is willing to share or point me in the right direction. 

I know there's another dual 12 design in the Fane book that is angled but honestly those angles threw me off the more I considered it. Celestion also has an angled dual 12 but I couldn't find performance specs on it and it's not ported.

Here's an image I found (not sure of the baffle diameter) that looks to be what your describing darkmatter, single chamber with shared port:



If I were to use the same volume as the Fane plan indicates for a single cab but simply double it and remove the (inner facing) side walls to yield dimensions of a single, shared chamber theoretically the performance should be close to the same, no? 

Still, I'm struggling with calculating the dimensions of the shared port without a reference.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shortrope Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2017 at 7:51am
Sim it in winisd with two drivers.
My Tinnitus is coming along nicely!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mellotone Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2017 at 5:47am
Have now sim-ed with 2 drivers and twice the volume, tuned to the same freq and the plot is pretty much identical. Unless I'm not accounting for something, it appears safe to say the dual driver, single chamber should work just as well.

Nice to have options. However, keep me in check if this doesn't add up.

My initial box in a box plan was intended to add front to back depth (dead space) to the cab considering how it fits in above the bass and below the comp horn. Also, want to add a little room on the sides to accommodate handle boxes without detracting more from the internal volume. 

Lastly, I'm planning a vintage style baffle cut-out for this cab to give a finished look.
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