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#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.

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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.

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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.

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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.

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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.

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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.

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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



Threaded Inserts (Sub woofer mounting solution)

Panel Names?


Below is a reference image
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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.

Reference Port Plug Design - link

Performance data (HR Estimations GP1m):
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)
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Common 18" Comparison Graphic
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Current (9-1-22) top picks!
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Note: The Alpha III and IV have narrow clones. The FBv6 has a narrower clone and the 18BMDSV2 has a clone.

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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18
#5,450 ·
Yes, high strength motor drivers work fairly well in any enclosure. The only concern might be hitting xmax before hitting a low frequency target SPL. As always, model the driver and all of the enclosures you are considering to understand the trade offs in size vs performance. If you are looking for a high strength motor with bigger xmax to run in a smaller sealed enclosure, take a look at Harbottle. They have drivers that closely mimic the strengths of a high end pro driver, but then also has the longer stroke and associated higher xmax to hit higher SPL at low frequency in a sealed box.
 
#5,453 ·
Why are we discussing boring @$$, inefficient, and distortion plenty sealed enclosures in a BP6P thread???

BP 4 Life!
 
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#5,455 ·
Without getting too technical with the differences between the NSW, DS and SAN the main difference will be power density. The NSW can crack a few more db vs the SAN or the DS with the much longer throw it is capable of. With current MSRPs the NSW is not the easy sell it once was.
 
#5,456 ·
Teaser - Mini 18 Stepped Version 3 with an 18DS100-4 on 1kw. The cabinet features a Flex tune. 22Hz, 18.5Hz and 15Hz for tuning options.

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#5,457 ·
Teaser - Mini 18 Stepped Version 3 with an 18DS100-4 on 1kw. The cabinet features a Flex tune. 22Hz, 18.5Hz and 15Hz for tuning options.
Eager to see the output curves for the alternate tunes. :)
 
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#5,464 · (Edited)
I'm going to put my V5 Lavoce up for sale tomorrow, so for the first time I got a taste of what one of these does on a suspended floor. My family room is 20'x18'x9' with a vaulted ceiling next to the kitchen (~20'x14'x8') and open to the rest of the first floor. Oh my!!! Even in a big open area this has big impact and is very impressive, even though it's not quite what the newer stepped models are. Also, it was also very clear some of the rushing air I feel in my theater on big impact scenes are coming from the ports on the V5 which aren't as large as the ones on the HOs (I have an NSW in my other V5 in use). :D
 
#5,470 ·
Mini 18 Stepped Version 3 Flex Tune

This box was the result of a request for hitting a specific form factor @Schurter. The gross box displacement is 15.6 cubic feet, so it sits between a Mini Marty and Full Marty in size. Tuning should work out to a bit over 21Hz with all ports open, around 18.5Hz with one port closed and about 15Hz with 2 ports plugged. The simulations are based on the 18DS100-4 pushing 1000 watts with an active 4th order Butterworth high pass filter active at 19Hz, 17Hz and 14Hz, based on the port plug configuration. The cabinet is relatively compact, so good power density is expected. The cut sheet is attached as a PDF.

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1000 watts 0 plugs

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1000 watts 1 plug

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1000 watts 2 plugs

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#5,472 ·
Can you overlay the graphs of Mini Marty vs Mini 18 Stepped vs Full Marty?
 
#5,473 ·
I do not have HR handy for the rest of the day. Which drivers are we comparing here? I think I did the math on the FM, did not do the math on the Mini.
 
#5,475 ·
I would have to look into it. The main issue is the depth. The D18SV2 would be pretty close to the target.
 
#5,480 ·
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Quick reference plot with a Full Marty UM 18 vs the M18SV3, both on 1kw.
 
#5,496 ·
Nothing that strikes me as a red flag off the bat. Motor could be a bit stronger. It would have to be used in a lower compression stepped front in my estimation.
 
#5,497 ·
That might be a good tapped horn (BP6S) driver.
 
#5,498 ·
Kind of quiet here.....my question.
I have a home theater in the basement until now a SBA. As a subwoofer have 2 pcs The Finalizer version 4 Shallow ( NSW6021-6)and 2 pcs kicker with 8Sound 15ND930. Now I want to rebuild and install a DBA. Unfortunately I don't have much room in the back in terms of depth, would something like this work well 21" Slim Nearfield 7.8cu ft Build with LaVoce SAN214.50
or even better the suggestion from Red Five 21" Slim Nearfield 7.8cu ft Build with LaVoce SAN214.50
As a driver, a SAN214.50 or a NSW6021-6 should be used. My desired size would be Marty calculator

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#5,500 ·
Kind of quiet here.....my question.
I have a home theater in the basement until now a SBA. As a subwoofer have 2 pcs The Finalizer version 4 Shallow ( NSW6021-6)and 2 pcs kicker with 8Sound 15ND930. Now I want to rebuild and install a DBA. Unfortunately I don't have much room in the back in terms of depth, would something like this work well 21" Slim Nearfield 7.8cu ft Build with LaVoce SAN214.50
or even better the suggestion from Red Five 21" Slim Nearfield 7.8cu ft Build with LaVoce SAN214.50
As a driver, a SAN214.50 or a NSW6021-6 should be used. My desired size would be Marty calculator

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Driver selection is mostly based on budget. The NSW is quite expensive, unless power density is the number one priority above all else you can probably get away with a SAN instead. Did you need me to check numbers on the current box with HR?
 
#5,499 ·
Why not a bandpass kick bin since this is a bandpass thread?
 
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#5,501 ·
@
BP1Fanatic
Well..I would also prefer to install 2 St. Devastator 21 rear but unfortunately have no space.

It will probably be the San, the NSW is with us as good as not available.
Did you need me to check numbers on the current box with HR?
That would make me very happy if it allows your time.:giggle:
It will probably 2 St. coffins that are narrow and high, but he should work quite well.:LOL:
 
#5,502 ·
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Based on what you had in the slot port calculator your tune is around 25Hz. Port height needs to come down quite a bit.
 
#5,503 ·
Thanks for your calculations (y) , this really doesn't look good.:eek:
The Marty Excel probably can not cope with such a strange design. Now I'm not the expert for such calculations, and this post is about the Devastator so I'd better create a new post with my coffin in DIY Speakers and Subs or I find a similar post and hang on.
 
#5,504 ·
Thanks for your calculations (y) , this really doesn't look good.:eek:
The Marty Excel probably can not cope with such a strange design. Now I'm not the expert for such calculations, and this post is about the Devastator so I'd better create a new post with my coffin in DIY Speakers and Subs or I find a similar post and hang on.
You could probably go up to 33" wide with the calculator sheet. I am assuming it does not add extra rails etc once you get past 10" wide spacing on those structures.
 
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