My Sub-Low Reflex Project
Printed From: Speakerplans.com
Category: Plans
Forum Name: New Projects Forum
Forum Description: Forum for new speakerplans projects, in memory of Tony Wilkes, 1953 - 2014
URL: https://forum.speakerplans.com/forum_posts.asp?TID=19599
Printed Date: 26 March 2026 at 10:55pm
Software Version: Web Wiz Forums 12.08 - https://www.webwizforums.com
Topic: My Sub-Low Reflex Project
Posted By: Elliot Thompson
Subject: My Sub-Low Reflex Project
Date Posted: 10 September 2008 at 7:32pm
After using my Double Eighteens for over 13 years, I feel it is time to build an extended version. I actually draft this design the same time I created the version I’m using today. The difference then, was not having the enough funds to build as many boxes as I would like due to its larger size. If it weren’t for me holding on to my Composition books when I was a teenager, I would have forgotten this design completely. 
My Double Eighteens offer the standard – 3dB @ 35 Hertz, which is common amongst all higher end Pro Audio dual eighteen cabinets. I’m not sure if they are taking 2.83 volt into consideration when they are posting their specs. Nevertheless, I always used Normalised Gain as my benchmark, which doesn’t take the additional voltage into factor. So, the response is based on how the drivers will react with no signal. I’m aiming for – 3dB @ 27 –28 Hertz while still offering the same SPL as my current Double Eighteens. This is just a preliminary analysis for I am still searching for other driver options at the moment. I’ve chosen two Beyma 21 L50s, which seems to meet my requirements. They are able to take a full 2000 watts (1000 watts per driver) from 100 – 27.4 Hertz while offering the same SPL as my current Double Eighteens. One thousand watts for each driver is my limit due using Crown Macrotech 5000s (2000 watts per channel @ 4 ohms) for my bass. 
------------- Elliot Thompson |
Replies:
Posted By: Elliot Thompson
Date Posted: 10 September 2008 at 11:03pm
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Furthering my research I decided to give other woofers that are known for their extended low frequency response a try. I’m using the Beyma as the benchmark for the driver will need to match or exceed its performance in terms of SPL. Once that happens I’ll compare the volume displacement amongst the two. With all the drivers wattage configured to get 1000 watts per driver, efficiency will be the deciding factor. The Acoupower offers a –3 dB at 23.73 Hertz, which is excellent. Unfortunately, at 1000 watts per driver, it only delivers 126 dB. 
Next, is the Ciare 18.00 SW. It offers a – 3 dB at 24.85 Hertz. But, 127 decibels is no better than the Acoupower. Moving right along is the McCauley 6174. I personally like this driver after hearing how low it can go. It offers a – 3dB at 26.85 Hertz. Still lower than Beyma which is 27.4 Hz. But, it falls short at 130 dB whereas, the Beyma is 132 decibels. 
Cone displacement is not even my concern after viewing the outcome. However, if you would like to see the results just look below. 
The Beyma is the most efficient. ------------- Elliot Thompson |
Posted By: nickyburnell
Date Posted: 10 September 2008 at 11:09pm
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And also the Beyma is a good price for a 21" ------------- It's everything, not everythink! |
Posted By: Elliot Thompson
Date Posted: 11 September 2008 at 12:13am
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Here is a nice 21-inch woofer shootout. This test was rather interesting for nearly all of them met or exceeded the Beyma. I didn’t even bother adding Precision devices for they are not available in the States. The candidates are: B&C 21 NW 160 Eighteen Sound 21 LW 1400 Madison Executioner X 21 P Audio SD 21 The B&C was only 1 dB short (131 dB) of matching the Beyma (132 dB). So, it is a good candidate. There is only one problem. The box is too big for this driver to handle, which is clear once it offered – 2 dB from 80 Hertz to 40 Hertz in the Normalised Gain chart. If I just looked at the Maximum Acoustic Power I would’ve said the Eighteen Sound is the winner offer 133 decibels. However, looking at the Normalised Gain and, seeing –3 dB from 67.8 Hertz to 36.7 Hz, it is obvious this driver is struggling to reach 29 Hertz before collapsing. The Madison offered 129 decibels and, still requires a bigger box than what I can offer. It offers + 3.5 dB from 39.4 – 38 Hertz. I don’t mind having + 1.2 dB in Normalised Gain. A +3.5 dB gain means the box is going to ring like a bell from 39.4 – 38 Hertz. The P Audio just fails in this cabinet period. It offers 135 dB from 107 Hertz and up. The – 3dB point is 103 Hertz and continues to decline. Whoever designed this woofer was aiming for horn usage. Possibly a nice HD 21 Kick Bin. 
Just a few more woofers to try before investing in some Beyma 21 L50s. ------------- Elliot Thompson |
Posted By: Elliot Thompson
Date Posted: 11 September 2008 at 12:27am
Right! The 21-inch Beymas cost around $600.00 each while the others (B&C and P Audio) are $750 - $800.00 I didn't even compare prices during my research until you stated they are cheaper. 
For my wallets sake, I hope the Beyma wins!
Best Regards, ------------- Elliot Thompson |
nickyburnell wrote:Posted By: bitzo
Date Posted: 11 September 2008 at 8:32am
No precision devices? or turbosound? |
Posted By: Deadbeat
Date Posted: 11 September 2008 at 8:41am
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Can't get turbo or PD in the US easily
------------- Away on extended leave. |
Posted By: Elliot Thompson
Date Posted: 11 September 2008 at 11:41am
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Precision Devices and Void is probably the only driver that is scarce in the States.
It didn't fair well in my box either. As you can see, it goes into compression from 34.7 - 55.6 Hertz in the Maximum Acoustic Power chart in addition to declining to - 3dB from 81.3 - 38.7 Hertz in the Normalised Amplitude Response. I would need to raise the tuning frequency to have a constant 133 dB across the frequency bandwidth, which would beat the Beyma by 1 dB. The only problem is the current tuning leaves the PD 2150 offering a - 3dB at 29.23 Hertz whereas, the Beyma is 27.4 Hz 
So this driver won't go low enough for my needs. 
As you can see I am very particular when it comes to speaker performance. I’m pretty particular period.
Best Regards, ------------- Elliot Thompson |
Posted By: Elliot Thompson
Date Posted: 11 September 2008 at 1:32pm
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I’ve resorted to 18-inch drivers again after seeing all of the 21-inch drivers (Excluding the Beyma) not performing to my expectations in my cabinet. I began randomly entering 18-inch drivers in Eminence Designer’s customized database and, here are the results. The drivers are the following: Beyma 18 SW 1600 ND (Not available yet) Faital Pro 18 FH 500 Peavey Low Rider 18 BMS 18 N 860 B&C TBX 100 Eminence Defini Max 18LF The 18 SW 1600 ND was only 1 decibel short (131 dB from 26.9 – 100 Hz) and – 3dB at 26.7 Hertz. It also did not dip under 1.7 decibels within a 27.7 – 100 Hz frequency bandwidth in the Normalised Amplitude Response Chart. This driver will enter the next stage. The Faital Pro exceeded all delivering 133 decibels (28.4 – 100 Hz) however, dipping to 132 dB from 37.3 – 47.2 Hertz. If the – 3dB were lower (29.34 Hz) I would retune the box. However, the Beyma 21 L50 reaches to 27.4 Hz. The driver doesn’t go low enough. The Peavey is astonishing. It reads 132 decibels from 27.4 – 100 Hz from the Maximum Acoustic Power chart with a – 3 dB @ 28.34 Hertz. This driver will enter the next stage. 
The BMS output is too low offering a mere 129 decibels from 26 – 100 Hz. While it offers the best – 3dB (25.6 Hz) it is just not loud enough for the job. It also has + 2.7 dB at 32.9 Hz in the Normalised Amplitude Response. It will ring like a bell once a track arrives at that frequency. The B&C and the Eminence fail instantly based on their compression beginning at 69 Hertz in the Maximum Acoustic Power Chart. 
I don’t remember how many drivers I evaluated but I feel it was more than enough. Time to move on the next stage. ------------- Elliot Thompson |
Posted By: Elliot Thompson
Date Posted: 12 September 2008 at 1:07pm
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Volume Displacement Comparison If you haven’t read Rog’s notes in regards to Volume Displacement hear it is:
It seems some brands use a two times method where some do not. Pretty much like the measurement of xmax. Some say plus minus while another will say one way. I’m going to use the two times method to prevent any confusion among the drivers. Peavey Low Rider 18 = 2375 (4752 for two drivers) cc Beyma 18 SW 1600ND = 2510 (5020 for two drivers) cc Beyma 21 L50 = 3200 (6400 for two drivers) cc Amplifier Tone Burst and Speaker Tolerance With all old Crown amplifiers, there is a Maximum Power chart located in their instruction booklet. While many feel this graph is useless, I do not. It tells you how much wattage the speaker is getting with high dynamic material. Pulses can destroy a driver just as fast as a long-term continuous signal. The Maximum Power listed on a 4 ohm load is 3220 watts 1 KHz @ 0.05% THD and, 2310 watts 50 Hertz 0.05% THD. I’m going to use 3220 watts for the THD is very low and, at 1% THD it is highly possible 100 – 20 Hz will favour the 1 KHz analysis. I’ve also added my Double Eighteens to compare. The Lavender line will be the Beyma G 550s I’m currently using and, used as a benchmark when I started the whole project. I’m using Cone Displacement different than how Eminence Designer/Bass Box Pro suggest. With Cone Displacement, it measures the linear movement and darkens the offending line that exceeds its linearity. What I want to know is how much xmax is used before it approaches its xmech limit. I will more than likely never feed each driver 1610 watts, but for the idiot who boosts the fader from 6 – full on my mixer, I need to know where the woofers will stand. 
As we can see the Peavey has encountered some difficulty, and begins to go into compression dropping 1 dB from 134 – 133 decibels. The xmax is the highest amongst all three offering a peak of 16.6 mm @ 40.1 Hz. Next, is the Beyma 18 SW 1600ND, which maintains its consistency, delivering 133 decibels from 27.9 – 100 Hz. The xmax peaks at 14.1 mm @ 38 Hz. With a one-way peak of 30 mm there is still ample amount of headroom. We now look at the Beyma 21 L50. This driver still showing it’s class having no difficulty to handle the power. It delivers 134 decibels from 100 – 27.4 Hz in addition offering the lowest xmax out of the two contenders. The one-way xmech is 17.5 (or 35mm Peak to Peak) mm. Its highest peak receiving 1610 watts (3220 for two woofers) is 11.9 mm @ 41.6 Hertz. The Beyma 18 SW 1600 ND has more leeway than the 21 L50 however we must take the Volume Displacement into consideration here. Beyma 18 SW 1600ND = 2510 (5020 for two drivers) cc Beyma 21 L50 = 3200 (6400 for two drivers) cc The 21 L50 offers 690 cc over the 18 SW 1600ND. In addition to having the ability to deliver 134 decibels at 27.4 Hz whereas, the 18 SW 1600ND offers 133 decibels @ 27.9 Hertz. So, the 21 L50 is the best choice for my Sub-Low Reflex cabinet. I will now move on to the next stage, which will be cabinet construction. ------------- Elliot Thompson |
Posted By: rich_gale
Date Posted: 12 September 2008 at 1:39pm
| if going for 18" id use the mccauley. being based in the US i think this would be my first choice. second would be to find that photo of some half completed bassmaxx's and work out the horn path. drop the mccauleys into the bassmaxx's and enjoy:) |
Posted By: Elliot Thompson
Date Posted: 12 September 2008 at 1:50pm
Since I've met David Lee at two Subwoofer Shootouts and have the utmost respect for the man, I wouldn't do that. The McCauley was already tested in my box and offered too low of an output. All the drivers I tested (With the exception of Precision Devices) are readily available in the States. So, I not importing nothing.
Best Regards, ------------- Elliot Thompson |
Posted By: Elliot Thompson
Date Posted: 15 September 2008 at 1:12pm
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The construction of this cabinet will follow the same principals as my Double Eighteens:
Having the proper height to stack my tops Solidly built to handle elements of the world Holding 250 – 400 pounds without the slightest bit of strain, all courtesy of my tops. Moving from 18 to 21-inch drivers, the thickness of the baffle board must be increased. This is due to the weight of the drivers (40 pounds each) and of course the diameter difference amongst the two. So, I’m going to use a 54 mm baffle board (Three 18 mm sheets of wood glued/screwed together) instead of the standard 38 mm for my Double Eighteens. The sidewalls will however remain at 18 mm in addition to the top and bottom. I am still debating to use either 18 mm or 38 mm for the rear wall based on the amount of abuse it will endure once the drives excursion begins. With my Double Eighteens being 13 years old with not a rattle, I will use the same 2 by 4 bracing scheme I did for the my Double Eighteens on the Double Twenty-Ones. The front to rear brace may be increased to 4 by 4. My Double Eighteens were designed using the screw and silicone method. Each cabinet was constructed using one box of drywall screws and one tube of GE silicone. The Double Twenty-Ones will use two boxes of drywall screws and, two tubes of GE silicone due to the increase in size. As you can see weight, is the furthest thing from my mind. I don’t fancy lightweight boxes when it comes to subs. The only benefit I ever saw using lightweight subs is ease to move about. When producing lower notes (40 Hz – down) you need a cabinet that can withstand the air pressure build up from the driver’s excursion without vibrating itself to the point of moving. Since I am aiming for Sub-Low frequencies a heavier box is needed for a better performance. I am still torn between going the Double Twenty-One route or Single Twenty One enclosures. The overall depth makes it more troublesome to move about in and out of venues. I will need to further investigate designing one over the other. ------------- Elliot Thompson |
Posted By: mobiele eenheid
Date Posted: 15 September 2008 at 2:02pm
Regards Johan
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Posted By: biotec
Date Posted: 15 September 2008 at 2:52pm
Surely this is not necessary?
Intuition tells me that 36mm is more than enough, even for a double 21inch box. I would be more inclined to brace the baffle board more thoroughly rather than resorting to 54mm wood. ------------- me so horny, me love you long throw. |
Posted By: H...
Date Posted: 15 September 2008 at 5:05pm
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What are you gonna call the cab ?
The back breaker?
I'd go for a single 21" with the cab construction you are talking about.
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Posted By: wafflesomd
Date Posted: 15 September 2008 at 5:16pm
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Could always try a 21" scoop :)
That would go pretty damn low. What about something like the TSW-721 |
Posted By: sKs01
Date Posted: 15 September 2008 at 6:50pm
^ not massively, ever had a look at th response plot of a scoop, aside from the hog theyre only really useful down to 40Hz or their abouts, elliot thanks for the very in depth laying out of your selection process, if you have in mind that level of bracing/construction, unless you have some verry well paid roadies i would definatley suggest singles, i wouldnt be happy lifting one of those up stairs with any amount of people to help personaly. too damn heavy bulky and aquard just my 2p, looking forward to some pics of this 
------------- You're a big man, but you're in bad shape. With me it's a full time job. Now behave yourself. |
Posted By: csg
Date Posted: 15 September 2008 at 7:00pm
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both a 21" scoop and the tsw721 will struggle much below 35Hz. Reflex loading is predictable, scalable and sounds good on any musical style
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Posted By: rich_gale
Date Posted: 15 September 2008 at 7:19pm
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christ! 54mm baffle. id rather do the whole cab in 24mm and brace accordingly. in a dropping situation those 21's are gonna buckle/break before any damage is done to a 24mm baffle board imo.
with drywall/plasterboard screws i find the thread too sharp and spacing to be too wide meaning they can sometimes overturn in the pilothole when tightening and you loose your grip/material in the pilot hole..
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Posted By: wafflesomd
Date Posted: 15 September 2008 at 7:34pm
| Is there a genre that needs below 30hrtz extension? Organ music maybe? |
Posted By: csg
Date Posted: 15 September 2008 at 7:48pm
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i would not advise the use of drywall screws - they are made from a very hard but britle steel which is SPAX screws are available in the US try them - they are the best available this side of the pond
having built some 21" b&c loaded reflex subs myself this year using 25mm birch ply i can tell you that with the correct bracing, pannel losses are very low indeed.
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Posted By: csg
Date Posted: 15 September 2008 at 7:51pm
| extention below 35hz is a debatable subject. whilst the -3db point of my larger rig is 27hz, i often use a hpf of 36hz as below this little is added to the music, but a lot of power is wasted. for d&b and dubstep only do i run to 27 |
Posted By: Elliot Thompson
Date Posted: 16 September 2008 at 12:51am
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Thanks for the input. I’ve been visiting sound system forums for around 10 years and within that time period I’ve rarely if any I’ve talked about my sound system. I own two systems. The larger one consists of Twelve Double Eighteens having two cabinets sitting on one Crown MA 5000. The Dual Twenty-One or Single Twenty-One will be added to this system and, get another 5000. If they perform as expected I will build more and buy more Crown 5000s. I have no use for Scoops, which I got rid of in the summer of 1995 due to having one Double Fifteen cabinet out shine two Scoops (out of a quantity of 10) from 50 Hertz – Down. My Double Eighteens go much lower than my Double Fifteens (Which I own 8 boxes and provides bass for my smaller system). The whole concept of this design is to exceed the Double Eighteens low-end response and maintain the same SPL or 1 dB less during the process. The last thing I need is bass. This is evident by having five 18-inch drivers sitting in cartons for over five years and, four W bins sitting in the basement (Loaded with 18 inch drivers) that haven’t been used since 2004. I am in no way gloating on what I have. I am merely letting everyone know where I stand with subs at the moment. I’ve used drywall screws, silicone and, glue (very little if any) to build all my subs. The only boxes I’ve encountered losing their strength throughout the years are the ones I never put together myself (Purchased from a store). Please keep in mind that the box will be completely (Skeleton) framed with 2 (inch thick) by 4 (inch thick) bracing. So all the panels are attached to the brace. This is the concept behind my Double Eighteens and, with 13 years of moving them about with no signs of weakening it’s proven reliability that I cannot overlook. The thickness of the baffle board will either be 36 mm or 58 mm pending if I go for a single 21 or two 21’s in one cabinet. I prefer having 58 mm wood holding 80 pounds (Two Beyma 21 L50s) of speaker than, 24 mm. I know my method to many may look as overkill but, that is the whole idea of building it your self. You design the box to meet your requirements. rich gale The only way I can see drywalls failing in real wood is if you are counter sinking and making pilot holes. If you just drill the drywall in real wood it will remain in place until you use the drill to pull it out. H…. & biotec I will more than likely go for one 21 in it’s own cabinet so, the baffle board will be 36 mm. No name necessary for this design. It’s just a basic reflex box designed to low. Save the fancy names for the horns.
mobiele eenheid strength is definitely the concept behind all my subs so, I might as well go for a 36 mm rear wall. csg I can’t say I’ve ever cut off my boxes at 36 Hertz. I’ve used 27 Hertz for a few years until last week when I reduced them down to 25 Hertz (12 dB octave). The driver’s unload (in the cabinet) at 14 Hertz. Yes, I measured them. When I noticed sound was still emitting through the boxes at 20 Hertz (SPL was low of course) I decided to find out how low will they go before the driver unloads. wafflesomd Having boxes offering frequencies below 30 Hz, usually means you are relatively flat @ 30 Hertz. For those tracks that sweep into 30 Hertz, a box offering a – 3dB in the upper twenties will do a far better job producing 30 Hertz than, a box offering a – 3dB point in the mid 30’s. There is a shop in NYC that sells Beyma's so, that will be the next step. Best Regards, ------------- Elliot Thompson |
Posted By: wafflesomd
Date Posted: 16 September 2008 at 12:57am
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Start the builds! I wanna see these monsters. |
Posted By: gratzi
Date Posted: 16 September 2008 at 4:20pm
what price does this driver reaches ?  ....and where you can buy these driver?...i heard it`s only a prototype for the moment...i didn`t knew it wass lauched for mass production.. |
Posted By: Elliot Thompson
Date Posted: 16 September 2008 at 8:44pm
In the States, there is a store that is advertising it as "Coming Soon." If it performed better than the 21 L50 in my cabinets, I would have waited. I'll need to wait nevertheless for the 21 L50's. The shop I visited will need to special order two for me. Best Regards, ------------- Elliot Thompson |
Posted By: H...
Date Posted: 16 September 2008 at 9:25pm
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Do you drive a V8?
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Posted By: Elliot Thompson
Date Posted: 18 September 2008 at 12:51pm
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With the economy turning into complete rubbish in the States, spending nearly $2000.00 on a project that is not necessary, would be an idiotic thing to do. So, I'm going to put this design on hold for now. As I mentioned in my previous post bass, was never an issue so, this type of splurge can wait. Best Regards, ------------- Elliot Thompson |
Posted By: wafflesomd
Date Posted: 18 September 2008 at 6:05pm
| Whereabouts are you located in the states? |
Posted By: Elliot Thompson
Date Posted: 18 September 2008 at 8:45pm
New York.
Best Regards, ------------- Elliot Thompson |
Posted By: Kumruz
Date Posted: 26 September 2008 at 12:23am
Regarding Volume Displacement Comparison I think that theres error in calculation of VD because if cone surface is 1100cm2 and xmax is 5mm thats 1100cmx0,5cm=550ccm one liter is 1cubic decimeter thats 10x10x10cm=1000ccm
also if surface 1100 and xmax 12mm thats 1100x1,2=1320ccm (1.32liter) Why not consider RCF drivers? ------------- size does matter(to my back and to my wife) |
Posted By: Elliot Thompson
Date Posted: 26 September 2008 at 12:34pm
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Kumruz,
Beyma drivers perform better in reflex cabinets than RCF for my requirements. There is another brand at the moment that exceeded Beyma's performance (Thanks Deadbeat for bringing it to my attention) however, they are still in the process of getting distributers. Which is fine for me. As I mentioned the economy is rubbish in the States (I guess they are too proud to say that we are in a recession) so, I'm holding off until things get better. As for the error in the calculation, that is something you will need to take up with Rog. Best Regards, ------------- Elliot Thompson |
Posted By: _radu
Date Posted: 06 October 2008 at 4:39pm
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Hi Elliot, Anything new with the cabs ? Pictures maybee ? :) |
Posted By: Elliot Thompson
Date Posted: 07 October 2008 at 10:20pm
Hello radu. The economy is getting worse in the States. I'm waiting for things to start picking up before I invest in such a project. Best Regards, ------------- Elliot Thompson |
Posted By: aperrado
Date Posted: 08 October 2008 at 5:16am
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hey guys I need help to get the volume and wood thickness for a gsub, I think it is nothing to see with this post but watching the grafics I think u can help me I tried winisd but I cant use it ------------- Im hard to learn but still asking |
Posted By: Battered
Date Posted: 21 May 2013 at 5:12am
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Elliot Did you ever get round to building any 21's? |
Posted By: Elliot Thompson
Date Posted: 21 May 2013 at 11:58am
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I built four of them a year later. They are fed 3000 watts (1500 watts per driver) per bin on some old Crown Powerbase 3 amplifiers bridged. There is another design in the works that should offer a -3 dB @ 23 - 24 Hz that I should be focusing on in 2014 however, they will be 18’s. Best Regards, ------------- Elliot Thompson |
Posted By: Battered
Date Posted: 21 May 2013 at 6:54pm
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Got any pics? I'm leaning towards a couple of 21" or 24" Reflex singles, I don't need the higher SPL of a 2 x 18 and a couple of extra octaves at the bottom will be better for me anyway. Size won't be a problem because they won't be moved, they'll stay in one place so they can be as heavy as they need to be. They won't have any Drum & Bass or Dubstep going through them, or any 'Sub heavy' music at all really, which is why I think large Reflex enclosures will be perfect. |
Posted By: Elliot Thompson
Date Posted: 21 May 2013 at 7:35pm
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For what you want it would be best to just make a new thread and start from scratch. Select the drivers you are looking to buy and take it from there. Best Regards, ------------- Elliot Thompson |
Posted By: Battered
Date Posted: 21 May 2013 at 7:49pm
No worries, I've pretty much decided the drivers I'll use. I'll start a thread when the time comes, your input will be welcome 
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Posted By: Elliot Thompson
Date Posted: 21 May 2013 at 8:22pm
I will most definitely help if I can. You may be able to achieve a –3 dB @ 20 Hz if the driver you select is capable of doing it and, you are willing to accept a large box. The single (21-inch) driver below is Made In Canada. It will actually offer 124 dB @ 17.4 Hertz before taking a nosedive. You could not feed it more than 600 watts. Anything above 600 watts power compression comes into play.  Best Regards, ------------- Elliot Thompson |
Posted By: Battered
Date Posted: 22 May 2013 at 12:48am
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I'm resigned to needing a big enclosure, but it won't be moving anywhere so it's not a problem
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