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The Singing Canary Sub

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volcano View Drop Down
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    Posted: 22 September 2016 at 7:31pm
Hello all,

I'm planning to build a new soundsystem.

As top boxes I'm going to make a DIY MID HIGH, a 2x 12" BPH loaded Mid bass and a 1.4" coax BMS driver. Link here:
https://soundforums.net/forum/low-earth-orbit/diy-audio/11601-new-diy-mid-high

So I was on a quest of some bass boxes to be able to follow these tops.
I wanted a system that is reasonably sized and a one man lift, after testing different drivers my eye fell on the BMS 18n862, as it gives the response I was after in the right sized box, The Singing Canary was born!
Per side i want 3 bassboxes vs 1 topbox.

This is the first time I'm designing a reflex box, so it would be nice to have some feedback from more experienced designers.


Sizes are 50 x 55 x 93.5 cm so two can fit in my car.


I didn't draw the 3 bassreflex tubes yet, as my skills on SketchUp are limited. They obviously start at the front of the box, at the back of the box they make a 90degree turn up till the highest board with three holes. In total the tubes are just a little shorter as 1 meter.
Also not drawn are the round flares I will make at both ends of the tube te reduce turbulation. The flares will have a r of 3cm (20% of the 14cm diam. of the tube).

I paid extra attentions to bracing, especially because this box can drop low and can produce serious SPL levels. All outside panels will be Birch ply, but on the inside i wanted to used a lighter pine wood to save some weight.




After experimenting 3 tubes with a diameter of 14cm gave me the least air velocity. 28m/s at 1500W is the best I could achieve while still be able to fit the tubes in the box.
Is this figure acceptable?


this is the response with a Q2 filter on 28.5Hz applied.

Vb is 153 Liters, the ports take up 46 Liters, bracing and the speaker 15.5 Liters, So the total volume of the box is 214.5 Liters



Cone excursion... Here I would like some input, the BMS 18n862 has a Xmax of 19mm, the Xlim is unknown to me. At 1500W the speaker goes slightly over Xmax at 40Hz and more at 20Hz.
Is this acceptable? Or is this maybe too conservative because the probably the Xlim isn't in reach yet?


The filters I applied:




Before making the actual speakers I'm going to make a prototype, so I can measure the impedance and tune the speaker precisely accordenly.

Please share your thoughts...
Once the box is tested I'll draw up complete plans and will share it here with the community.

Blessings



Edited by volcano - 22 September 2016 at 11:35pm
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fatfreddiescat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 22 September 2016 at 7:51pm
With a quick glance it looks very good, full width slot ports may help with cooling if used for all night EDM. Bracing looks really good. no need to countersink the driver on the baffle, just weakens it, also how is the grill going to be fitted?
Looks like your going to have a tasty little system  - little in size onlyThumbs Up


Edited by fatfreddiescat - 22 September 2016 at 7:53pm
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volcano View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote volcano Quote  Post ReplyReply Direct Link To This Post Posted: 22 September 2016 at 8:10pm
For the grills I got inspired by the Tannoy SRM 15X as I would like to rock a 80s home stereo look.


I will use magnets to keep them in place, so two grills with a guitarspeaker cloth per box.

I tried a slot BR pipe but it gave me more air velocity as three pipes, I'm also scared about turbulence at high volumes in the square forms.


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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 22 September 2016 at 9:12pm
6db boost at the drivers resonant frequency is not a good thing in my book.
Actually any boost of 6db on subs is not good in my book.
What you are doing is pushing 4 times more power at 28.5hz.
It might be ok cone displacement wise, but the VC will be thermally stressed.


Marjan Milosevic
MM-Acoustics
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volcano View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote volcano Quote  Post ReplyReply Direct Link To This Post Posted: 22 September 2016 at 9:29pm
You guess that the coils will burn with an SAE PCM 20 at full tilt on 4 speaker?
Would you suggest to use no EQ at all? Or do you have a golden amount.
Without EQ the box will need to be 330L to go as deep... Thats starting to get out of my comfort zone.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote volcano Quote  Post ReplyReply Direct Link To This Post Posted: 22 September 2016 at 9:36pm
The actual boost is 4.4dB or 2.75 times more power, because of the High-pass filter that I'm using at the same time.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve20131 Quote  Post ReplyReply Direct Link To This Post Posted: 22 September 2016 at 9:36pm
If memory serves me correctly winisd recomends velocity to not exceed 17m/s,  nice sketch up
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 22 September 2016 at 9:36pm
There is no free lunch my friend.
Lets say you set the limiter to give 1500w. It will start limiting at the point when it delivers 1500W at 28.5hz.
At the same time the amp will be giving about 400W in the rest of the bandwidth.
So you will make boom at 28hz. What about the rest of the bass specter? 
Marjan Milosevic
MM-Acoustics
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Post Options Post Options   Thanks (0) Thanks(0)   Quote volcano Quote  Post ReplyReply Direct Link To This Post Posted: 22 September 2016 at 10:11pm
Because of the price of the driver I thought I paid my lunch already :D
500 euro a piece, my gosh... but it models so beautifull.

I understand your reasoning about the 400W, I was worrying about it myself.

So what can be a solution? less boost? different tuning?
BTW this is the size of cabinet that BMS recommends for this driver, Any idea what they recommend as filter settings?



Edited by volcano - 22 September 2016 at 10:12pm
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 22 September 2016 at 10:51pm
Where do they recommend a 170lit?
Marjan Milosevic
MM-Acoustics
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Post Options Post Options   Thanks (0) Thanks(0)   Quote volcano Quote  Post ReplyReply Direct Link To This Post Posted: 22 September 2016 at 11:24pm
http://www.bmsspeakers.com/index.php?id=18n862_specification

the bottom of the page says:

Recommended reflex enclosure:
153 L / 28,5 Hz, BRD = 200 mm / 601 mm long
Closed enclosure 100 L, -3 dB = 50Hz
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 22 September 2016 at 11:31pm
Take a look at the Coda subwoofers where they use that driver. CSP sub (2x18N862) has 520 lit outside volume. And yet it goes down to 25hz at -6db.
Marjan Milosevic
MM-Acoustics
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