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Discussion Starter · #1 · (Edited)
The number of Devastator versions and the number of documented Devastator builds is multiplying, it would be nice if some of this information were kept more neatly in one place. This thread is a work in progress. I will add new variants to this thread and also builds and link them below. :cool:

As always, in the pursuit of performance from the use of wood! Wood is still cheaper than amps and sub woofers.... Let's not forget the other part of the Devastator formula, simplicity! (remember we are dealing with a band pass here, they are more complicated). No diagonals, all panels are on right angles to simplify the building process.

Note: there are also some guides linked below in this post. If you have questions about how to assemble a Devastator, there is a lot of good information in the builds, do this and do not this. That is on top of the build guide. Basic assembly works its way from the top and front panels, towards the back and downwards. Top hatches, rear panel vents, high compression fronts and Stepped fronts have all be added as the Devastator has evolved. Items are listed for the most part in Chronological order. Several members have put a lot of time in documenting the build process. Please check out their build threads!

Want to design a Devastator all on your own? The Hornresp tutorial is posted below. If you have design questions feel free to post them in that thread! There are tools for helping design cabinets in Google Sheets posted in that thread too.

With the addition of the Stepped front Devastators, responses can be mostly flat natively. Knowing your room and what can fit in a space are going to be key factors for selection vs trying to leverage the response shape in spot the suites the box well.

Suggestions for box selection: Devastators have seen evolutionary progress as time has gone on. The biggest factor for selecting a Devastator is the space available. That is one of the main driving factors for the wide array of designs beyond achieving more performance from the use of building material. Room size is another big factor. (I grabbed this from Audioholics)

Room
Dimensional Volume
Small Room​
< 1,500 ft^3​
Medium Room​
1,500 ft^3 to 3,000 ft^3​
Large Room​
3,000 ft^3 to 5,000 ft^3​
Extreme Room​
> 5,000 ft^3​

Small room, you can probably get away with a couple Micro 15" Stepped V1s. Medium room, you will need a couple 18"s at least. Large room - 21"s. Extreme, how many Fat Boy V5s can your marriage take? Other factors, is the room open to other areas and is it an odd shape? That can mess with the equation especially if sub placement options are limited.

Why bass physics suck:

Below is the Fat Boy Version 5 with the native 22Hz tune in gray and I tweaked the vent area down so it is now tuned to 18Hz. As you can see from the graph output takes a huge 5db hit from the lower tuning. In room that 22Hz box will probably stick with all the other Index Devastators down to 17Hz or 18Hz. That is a bit room dependent, so your mileage may vary. Also, remember 6db is the equivalent of doubling your sub system, amps, boxes and sub woofers, 3db from cone area and box displacement and 3db from the input power doubling.

Rectangle Slope Font Plot Parallel



Now I am going to push this further down to 15Hz tuning on the rear chamber. As you can see we are down a solid 10db on the left corner from the original 22Hz tuning and another 5db from the 18Hz tuning.

Rectangle Slope Font Plot Parallel


The important thing to know? Each octave (dividing a given frequency by 2) you descend in frequency will require 4 times the displacement to achieve a given level of output. Let's say when tuned 20Hz a box can hit 88db on 1 watt of power with 1mm of excursion. If we tune the box to 10Hz it would take 4mm of excursion from the woofer to hit 88db. This is an important fact when selecting a Devastator. There are three factors that will come into play. Output, Extension and Cost, those factors will always have to be balanced. You can chose 2, but you cannot get all 3 unless you are in a very small space that gains very well. A 7000 cubic foot room on a concrete slab is not a good place to chase extension. It would be better to go with higher tuned cabinets and gain the wobble effect from a BOSS platform. Unless you have the luxury of unlimited budget.

High Pass Filter Orders:

Real quick rundown, 6db of slope is an order. For example a 2nd order Butterworth filter will knock the response down 12db per octave. If set to 20Hz the response will be down 12db at 10Hz, assuming it is applied to a flat line. 2nd order filters can make integration easier in certain circumstances. Especially if the cabinet tunes have a wider range than just a few Hertz. Integration with sealed cabinets can be more tiresome and require a lot of trial and error. An 8th order 48db per octave slope on the sealed cabinet and then using a 2nd order HPF a few Hertz over tune on the Devastator can be a good starting point. Once again YMMV. If you do plan on using a 2nd order filter, go a little over tune with the filter to control driver excursion below tune.

Order: (typically you will not see a Dev go over a 4th order, just keep multiplying by 6 to go up)
1st 6db per octave
2nd 12 db per octave
3rd 18db per octave
4th 24db per octave

Why do we need High Pass Filters on a Devastator?

Below the tuning frequency of the Low Frequency(LF) resonator cone excursion goes out of control(see example below). The cone is no longer seeing a load like it would above the tuning frequency of the LF resonator. The cone movement would be similar to the sub being given power in free air. A pro driver can take several hundred watts in most cases in free air when sent a low frequency waveform. Doing that to a woofer frequently could A. damage the woofer over time and B. if sent a more powerful signal could bottom the woofer out immediately. The High Frequency (HF) resonator does present some load to the woofer below the LF tuning frequency, but it is not enough to control the cone movement. DO NOT RUN your Devastator without a protective high pass filter.

Rectangle Slope Plot Line Font


As you see in the graph above, the cone motion with the 2000 watt input on this NSW6021-6 has the driver well outside of the 21mm xmax below 20Hz. Once a Butterworth 18Hz 4th order high pass filter is actived the cone is peaking around 19mm below 20Hz(light gray line) and that is inside the NSW6021-6's rated xmax.

Slang/Terms:

HCR - High Compression Ratio. This front has a bell curve, but is not quite as peaky as a lower compression front and uses less space. Good for shallow cabinets.
TR - Tactile Response
Stepped - A front quarter wave resonator with 2 or 2+ cross sectional areas. The response is typically more flat and they gain more low end output.
BR - Bass Reflex
QW - Quarter Wave resonator. These are typically referred to as horns. On a Devastator they do the high frequency lifting.
FPR - First Port Resonance
BB - Baltic Birch plywood. (not the veneer box store stuff, call a lumberyard)
BBv1 - Big Boy Version 1
MLP - Main listening position.
REW - Room EQ Wizard.
HPF - High Pass Filter.
BW - Butterworth.
LF - Low Frequency
HF - High Frequency
HO/SHO - High Output or Stepped High Output. Usually these cabinets have 22Hz tuning.
BMD - Beast Mode Devastator. Typically they are closer to 60" height vs 48"
FV - Finalizer. This cabinet started as a 48"x25.5"x34" cabinet with lower tuning. FV can be used for the 16Hz tuned rear chamber or the form factor
Dev - Devastator. Generally cabinets that are around 48" in height.
Mini - Typically this cabinet type is around 40" in height.
Micro - Usually in the above or around 30" in height.
Nano - Usually used for 12" cabinets.
FB - Fat Boy. Typically as deep as they are wide.
BAMF - Bass Ascension Module Five. Home music or PA cabinet with higher tuning and a Stepped QW resonator.
NSW - Eminence NSW6021-6
SAN - Lavoce SAN214.50 or the SAN215.30 is another good choice, but not usually that is referring to the 214.50.
DS - That could be a B&C 21DS115 or a 18DS100-4, both are great choices.
TBW - B&C 18TBW100 is usually the reference, but the 15TBW100 is another good woofer.
SAF - Lavoce SAF184.03
WAF - Should be the Lavoce WAF154.00
D21V6 - This would be an example the Devastator 21" version 6
M18V6 - This would be an example of the Mini Devastator 21" version 6
FB21V5 or FBv5 - Fat Boy Version 5
FV1 - Finalizer Version 1

Devastator response evolution:

The Devastator has seen developments over time. The examples below are on 48" tall cabinets to show the three main fronts and how they affect the response.

The Devastator 21" Version 1 is the first Devastator designed by John. As you can see the front HF QW resonator adds SPL across the entire frequency range, peaking in the mid bass region. Light gray is ported cabinet with the same vent length, vent area and chamber volume as the D21V1.

Rectangle Slope Font Plot Parallel


Next up we have the Devastator 21" Version 5 with an HCR front. The HCR front has a smaller cross section area vs the lower compression front, but still adds output across the range and takes up less space in the cabinet. Once again dark gray is the V5 and light is just a basic BR chamber with the same specs.

Rectangle Slope Plot Line Font


Finally we have the Fat Boy Version 5 with its Stepped QW resonator that has multiple cross sectional areas. The higher tuning coupled with the design of the QW resonator makes the cabinet very flat and efficient. The higher tuning also allows the resonators to be spaced 1 octave apart in frequency without cutting our top end short, so this design can still crossover at 80Hz into a sound system.

Rectangle Slope Font Plot Line


Other advantages to having the front QW resonator:

Cone protection from curious children, pets and sometimes friends that are tipsy. Less rear chabmer/motor noise, the panels dampen noise that would otherwise find its way through the cone and into the room. Obviously the QW resonator eats up more space vs having nothing in front of the woofer, but the QW resonator has a few things going for it.

Construction/material/tips:

The preferred building material is currently expensive. Baltic Birch plywood (not the veneer stuff at box store, call a local lumber yard) is the preferred building material. 18mm is close enough to 3/4" not to mess up the building process. MDF is heavy and makes a big dust mess and does not take screws well, tends to crack. ACX plywood is lightweight, but has voids and a tendency to warp. BB is lighter than MDF and does not make the dust mess and is less prone to warping and also voids. MDF also sucks for using Kregs.

If you have router with a flush trim bit, it is not a bad idea to add 1/8" inch on the side panels and then clean it up after assembly.

PL3X is the glue of choice due to how forgiving it is with voids and set time. When using PL, wear gloves, you do not want that stuff getting on your skin and it will mess up clothing. If you are a fluent wood worker, you do not have to say no to tight bond.

Marking panels before assembly is another pro tip. I would also suggest marking up the woofer cutout and drilling all the holes for fastening the woofer before assembly. Marking the panel alignments/positions on the side panel, front panel and baffle are all good ideas. Measure twice, cut once is another good rule to live by.

Air leaks around the access panel are usually the number one issue once the box is together. Especially if the measured response looks weak on the left corner. If you want to make sure you have a good seal, turn off the lights, put a flashlight in the rear chamber. Button the hatch up and look for light coming through the hatch seal. Weather stripping or the PE gasket tape will work.

If you have a question or are unsure of something when putting the cabinet together, feel free to post the question in the Index. This thread has large following that is happy to offer tips!

Bracing - here is a good example of a common bracing mistake. The wider dimension should be adjacent to the outside panel, like in the photo below.

Driver mounting - Chris made this write up for his technique for securing the sub to the baffle - link



Panel Names?

Below is a reference image
Rectangle Parallel Font Plan Diagram


Rear Chamber Resonance/dampening material

Chris when testing the JBL Quad Devastator did some measurements with different pillow configurations in the rear chamber. We also reached out to a few members for measurements they took. It would appear standing waves in the rear chamber start to encroach on the passband somewhere between 40" and 48" of rear chamber length. Boxes close to 48" on up need pillows tacked onto the side panels to alleviate near past band resonance. The goal is having a clear path from the back of the woofer to the vent inlet. Air restriction will hurt low end output. However, if there is minimal restriction in air movement, a minimal loss in low end output will take place. Here are the links to the Quad testing.

Resonance Testing Pt1
Resonance Testing Pt2

Does my UM18/IB/high Qts Sub work in a Devastator?

The short answer is no, it does not work in a Devastator. This is a UM18 in a Mini Devastator 18 Version 6.



As you can see the woofer gets a very sharp peak at the resonant point of the front horn of the cabinet. You might be thinking why not just EQ that peak? Here is the problem, the UM18 will ring when loaded in a Devastator, the cone stays in motion after a impulse. This is the UM18 vs the 18TBW100, pink is the UM18, green is the TBW. Notice how the cone on the TBW stops moving relatively quickly. Some subs are designed to work well in higher order band pass boxes, others are designed to work in lower order band pass boxes. There is a simple method for finding a good woofer using a specific metric. Efficiency Bandwidth Product (EBP), the woofers Fs value divided by its Qes value. The Devastator starts working once a value gets around 70 or so. Values closer to 100 are better, but not absolutely necessary. If you have a woofer with a value higher than 70 and are curios to see how it looks, just post a message in the thread :)



Any Devastators optimized for music?

Yes, the BAMFs are designed to handle music duty/PA use. There are currently three different versions available with different tuning depending on the needs of your system. If interested I have a smaller design meant for an 18" that will definitely make some loud noise that has not been released yet.

I bought a Crown amp that has a network card, how do I manage it???
Chris made a nice write up concerning this situation, you can find it right here. You will need the Harmon Audio Architect software installed on computer that is on the same network as the USP card.

Performance data:
The Big Boy Family 21"s
The Fat Boy Family 21"s
The Finalizer Family 21"s
The Alpha Family 21"s
The BAMF Family 18"s + 21"s
The BMD Family 21"s
The Mini Devastator Family 21"s
The Devastator Family 21"s
The Mini Devastator Family 18"s
The Devastator Family 18"s
The BMD Family 18"s
The Micro Devastator Family 18"s
Shallow + Narrow 21" + 18" Devastators

Common 21 Comparison Graphic (shoutout to Chris for his help with this)
Rectangle Slope Plot Font Line


Common 18" Comparison Graphic
Rectangle Slope Plot Line Font


PLEASE SHARE BUILDS IN THIS THREAD!!! (including pictures)

Designs (Guide is near the bottom of this post and see build links, a lot of go information in there.)

Broken down by woofer size:

24"
21"
18"
15"
12"
Build threads/other
Guides
 

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Discussion Starter · #3 ·
This is a great idea and will make things much smoother for people wanting to build these.

Sent from my SM-N950U using Tapatalk
That would be very helpful! If the pictures were in order with one sentence summaries of what needs to happen at each step that would be very helpful.
 

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That would be very helpful! If the pictures were in order with one sentence summaries of what needs to happen at each step that would be very helpful.


I’ll be honest that was my original intent but you get so caught up in the build you forget to take pictures of every step. Super good idea red five hats off to you for your help and support.

Ps don’t forget to add the MBM ;) that will be coming to to a home very near me!


Sent from my iPhone using Tapatalk
 

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Discussion Starter · #5 ·
I’ll be honest that was my original intent but you get so caught up in the build you forget to take pictures of every step. Super good idea red five hats off to you for your help and support.

Ps don’t forget to add the MBM ;) that will be coming to to a home very near me!


Sent from my iPhone using Tapatalk
The Mini MBM, the LBM, BMD MAX, 30" wide almost v1 and a new 18 inch version are on the eventual list. I should make an MBM version of the v1 tuned around 28Hz. :)
 

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Discussion Starter · #7 · (Edited)
Micro Devastator MBM 15"

Here is the Micro Devastator MBM! (going with micro something else might be a mini....) Comes in at an external 7.5 cuft, nice small foot print. Primary function is a two way configuration with the BMD MAX NSW to hit the mid bass really hard. Though it should work well with big ported HT drivers that lack the chest kick. Recommended crossover point is 60Hz. A 2nd order HPF for the micro and a 4th Order filter for the accompanying sub is recommended.


Sub drivers of choice. The Lavoce WAF154.00 or the B&C 15TBW100. Note not that usual panel overlaps. The Dayton PA380 is also viable, but power handling and excursion is more limited. Screen shot attached at the bottom.





2000 watts or 107.7 volts of power 45Hz 2nd HPF.






Particle velocity with 2000 watts of port and horn. Dark Port light horn 45Hz 2nd Order HPF active.










More detailed screen shots in the attachments!
 

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Discussion Starter · #8 · (Edited)
The BMD MAX 21"

This is the BMD MAX! The sub is built to handle the wrath of the Eminence NSW6021-6. Not too much has changed from the base BMD model. HPF 19Hz 2nd order should keep things in check. 95 volts = roughly 2.38 kw with 3.8 Ohms of load. The main goal of the design was keeping port velocity under 25m/s.











 

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Discussion Starter · #9 · (Edited)
The Mini Devastator 18" Box Size 40"x25.5"x24"

Tune on the box is 20Hz, this was squeezing all I could into the space, if you want a lower tune you can plug ports. The first port usually drops the tune 4Hz or so. External volume is only 14.2 cubic feet :) Preferred drivers are the LaVoce SAF184.03 and the SAN 184.03, the PA460 will work. I would also assume the 18TBW100 will work very well and the 18DS115 will work, but port velocity is high due to the stronger motor and higher excursion capability. The center of the sub woofer cutout is 10 inches from the top of the baffle panel. Assembly guide.






1300 watts or 87 volts, 20Hz 2nd order HPF.






PA460 1w1m vs the VBSS






Assembly order is mostly the same as a regular Devastator, the rear port board goes up the back panel and that is the main change.


















EQ setting for close to flat.

 

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Here is the Micro Devastator MBM! (going with micro something else might be a mini....) Comes in at an external 7.5 cuft, nice small foot print. Primary function is a two way configuration with the BMD MAX NSW to hit the mid bass really hard. Though it should work well with big ported HT drivers that lack the chest kick.


Sub drivers of choice. The Lavoce WAF154.00 or the B&C 15TBW100. Note not that usual panel overlaps. The Dayton PA380 is also viable, but power handling and excursion is more limited. Screen shot attached at the bottom.

OMG now your killing me. I've been debating replacing my entertainment center (link) with two larger shelf type units (one with AVR+5channel amp + Sources, the other with my 4 sub amps) and then spacing them out wider (moving to a 85" TV soon) and then using the area previously taken up by that entertainment center (63"W x 28"H x 20"D) for subs and my future center (which is 14" high).......

Two of these would fit in there side by side decently and work with the height I was wanting to go with too. I'd cover them (and the doors on the towers) with speaker fabric and they'd be "stealth"...

OK, is there going to be a flatpack of these by any chance? If not, I'd likely talk to the folks Mike uses in Chicago to at least cut everything down for me..... but a flatpack would still be easier (albeit more costly)......


GRRRRR ****Wheels spinning****
 

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Discussion Starter · #11 ·
OMG now your killing me. I've been debating replacing my entertainment center (link) with two larger shelf type units (one with AVR+5channel amp + Sources, the other with my 4 sub amps) and then spacing them out wider (moving to a 85" TV soon) and then using the area previously taken up by that entertainment center (63"W x 28"H x 20"D) for subs and my future center (which is 14" high).......

Two of these would fit in there side by side decently and work with the height I was wanting to go with too. I'd cover them (and the doors on the towers) with speaker fabric and they'd be "stealth"...

OK, is there going to be a flatpack of these by any chance? If not, I'd likely talk to the folks Mike uses in Chicago to at least cut everything down for me..... but a flatpack would still be easier (albeit more costly)......


GRRRRR ****Wheels spinning****

I have not had a conversation with Kevin about any of the variants yet... for now it is full DIY.
 

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I have not had a conversation with Kevin about any of the variants yet... for now it is full DIY.
No worries, in my excitement I failed there was a reason it was smaller....... it uses smaller drivers.... *DUH*...

I need larger drivers given the amount of space I have to fill, and the distance from the main LP...

I may still do something like that, but I'd likely need the larger variants (using 18 or 21" drivers)......

Thanks for letting me know these are full DIY. Makes sense.

Thanks for at least putting together all the graphs and plans. Thats a huge undertaking....
 

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Discussion Starter · #13 ·
No worries, in my excitement I failed there was a reason it was smaller....... it uses smaller drivers.... *DUH*...

I need larger drivers given the amount of space I have to fill, and the distance from the main LP...

I may still do something like that, but I'd likely need the larger variants (using 18 or 21" drivers)......

Thanks for letting me know these are full DIY. Makes sense.

Thanks for at least putting together all the graphs and plans. Thats a huge undertaking....

Well diaphragm size matters less as the frequency goes up. For every octave you go down, you need 4x the displacement to achieve the same level of efficiency. That is a good zone for running a 15 inch woofer. It only has to reach into the mid 50s region. 134db, is 134db with bass, but a 18 in a bigger box with a stronger motor could get a few more db potentially.
 

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Discussion Starter · #15 · (Edited)
I have the apples to apples comparison normalized to 1w1m. Then there is the 330 watt graph pushing close to 11mm of excursion which is the max for the 460. The outcome is expected, down about 8 db.





 

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Well diaphragm size matters less as the frequency goes up. For every octave you go down, you need 4x the displacement to achieve the same level of efficiency. That is a good zone for running a 15 inch woofer. It only has to reach into the mid 50s region. 134db, is 134db with bass, but a 18 in a bigger box with a stronger motor could get a few more db potentially.
Gotcha. Once I get things kinda finalized I will PM you with the space I've got available and what parameters I'm looking at, and we can discuss if any of these are a good idea. The issue is likely going to be my limited (for a horn) depth at around 22-24", which may limit the driver size choice for a horn, but not as much for just ported.

**Off Topic** Right now I've got WinISD open with a pair of 21's in 16cf tuned to 15hz @ 3m and the sims look good with port velocity in check.
 

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Discussion Starter · #17 ·
Gotcha. Once I get things kinda finalized I will PM you with the space I've got available and what parameters I'm looking at, and we can discuss if any of these are a good idea. The issue is likely going to be my limited (for a horn) depth at around 22-24", which may limit the driver size choice for a horn, but not as much for just ported.



**Off Topic** Right now I've got WinISD open with a pair of 21's in 16cf tuned to 15hz @ 3m and the sims look good with port velocity in check.
Well we can talk about it later. If you go 30 wide I can get an 18DS115 to do a lot. The horn cross sectional area is relative to the subs Sd. An 18 will be easier to keep shallow vs a 21".
 

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Tune on the box is 20Hz, this was squeezing all I could into the space, if you want a lower tune you can plug ports. The first port usually drops the tune 4Hz or so. External volume is only 14.2 cubic feet :) Preferred driver is the LaVoce SAF184.03 the PA460 will work. I would also assume the 18TBW100 will work very well and the 18DS115 will work, but port velocity is high due to the stronger motor and higher excursion capability. The sub woofer cutout is 10 inches from the top of the baffle panel.






1300 watts or 87 volts, 20Hz 2nd order HPF.









Assembly order is mostly the same as a regular Devastator, the rear port board goes up the back panel and that is the main change.
















Hello Red Five,


Can you explain more on "The sub woofer cutout is 10 inches from the top of the baffle panel." Should I mark 10" from the top and use it as the center for the circle?
 

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Discussion Starter · #19 ·
Hello Red Five,


Can you explain more on "The sub woofer cutout is 10 inches from the top of the baffle panel." Should I mark 10" from the top and use it as the center for the circle?

Correct, I will change the wording.
 
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