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21" reflext enclosure needed

Printed From: Speakerplans.com
Category: Plans
Forum Name: Ported Enclosures
Forum Description: Post all your reflex and bandpass and 'other' boxes with holes in stuff here...
URL: https://forum.speakerplans.com/forum_posts.asp?TID=105909
Printed Date: 04 December 2022 at 3:08pm
Software Version: Web Wiz Forums 12.05 - http://www.webwizforums.com


Topic: 21" reflext enclosure needed
Posted By: Mel_Gibson
Subject: 21" reflext enclosure needed
Date Posted: 02 December 2020 at 8:35pm
I'm going on holiday in January but in about Febuary or March i'm wanting two 21" reflex enclosures made, painted, handles, speakon sockets and grilles, painted black all the enclosure and grilles. Basically these plans are what i'd like built :
S-21LEX
http://www.beyma.com/en/enclosure-designs/ - http://www.beyma.com/en/enclosure-designs/

But i'd like handles on the side, castors aren't a big problem i'll be using a wheel board my mate made from plywood and attached castors to it. Is anyone able to do this professionally and give me a price for the two enclosures? I'll be buying the drivers when I get back from holiday.

Thanks.




Replies:
Posted By: smitske96
Date Posted: 02 December 2020 at 9:17pm
Personally I would not go for that particular design.
Ports are kind of small (definitely for triangle shaped ones). For such drivers I would look for designs with ports >800 cm2 slot/round. 


Posted By: Mel_Gibson
Date Posted: 02 December 2020 at 9:51pm
That enclosure was designed by Beyma themselves so I should think they know whether it's good enough, and many pro manufacturers have triangle ports which aren't actually very big. Martin Audio WS18X, EV QRX-218, RCF SUB-8002AS to name three out of many.


Posted By: smitske96
Date Posted: 02 December 2020 at 10:04pm
Not one of them uses a high power 21" 14mm xmax driver.
Look at the current offerings of big pro manufacturers like LA,PK, Meyer, JBL etc. 
They use huge ports for a reason. That triangle ports have more problems regarding to port compression (which changes tuning and therefore large signal performance) is a fact.

Still every design is made out of making compromises. Beyma chose for a simpler and easier port layout.
What you do with this info is all up to you Wink


Posted By: Mel_Gibson
Date Posted: 02 December 2020 at 10:09pm
I've emailed Beyma to see what they say as they designed the plans for the specific Beym 21LEX1600nd driver and they measured the response of the box loaded with the driver using pink noise with a 6db crest factor.


Posted By: djeddie
Date Posted: 03 December 2020 at 10:20am
One thing to bear in mind is that you haven't put your location down, not even which country.

-------------
Chas n Dave : it's like Drum and Bass but with beards.             E=mc² ±3dB


Posted By: cravings
Date Posted: 03 December 2020 at 11:22am
it's yet another account for djteknovibe / Jack_The_Ripper / richard stringer / Fred_Dibnah / richardstringer1993... so he's in Boston in Lincolnshire.


Posted By: Mel_Gibson
Date Posted: 03 December 2020 at 1:43pm
I live in Peterborough sorry i'll put my location on my profile now. I don't mind about ports not being triangular but I just figured Beyma should know what shape and sized ports would work best as they design the enclosures for their own drivers. 

I've seen on Youtube people have used Beyma, RCF, B&C etc...drivers to build their own subs and as far as I could see most are bottom rectangular ports. 


Posted By: smitske96
Date Posted: 03 December 2020 at 2:51pm
The Beyma designs are compromised. Its was a choice on their behalf. Going for a different port would be more difficult which then again costs more money.

9/10 times the youtube designs aren't particularly good. Most are really garbage.

A good design will cost time (and knowledge), after that you need to test and verifiy which again can take a lot of time. Maybe watch the enclosure design page of B&C for a while, they just put out some new designs and more are coming.


Posted By: Mel_Gibson
Date Posted: 03 December 2020 at 3:00pm
Originally posted by smitske96 smitske96 wrote:

The Beyma designs are compromised. Its was a choice on their behalf. Going for a different port would be more difficult which then again costs more money.

9/10 times the youtube designs aren't particularly good. Most are really garbage.

A good design will cost time (and knowledge), after that you need to test and verifiy which again can take a lot of time. Maybe watch the enclosure design page of B&C for a while, they just put out some new designs and more are coming.

How would you say they're compromised?

When I said Youtube I didn't mean people who make designs and upload videos of the designs I mean videos of people who've made subs using designs from B&C, Beyma etc..and then uploaded videos of them testing their subs out. 
Smile


Posted By: smitske96
Date Posted: 03 December 2020 at 3:17pm
Going for a smaller and triangle port is a compromise on itself. What you get in return is the bracing the port provides, and the easier practical tuning. Same goes for some older B&C S18cn design. Port area is around 122 cm2 and you want something in the sd/2 range. This combined with the triangle layout, you will get bad performance with large signals.


Posted By: Mel_Gibson
Date Posted: 03 December 2020 at 3:19pm
Would rectangular ports located at the bottom give me better performance? 


Posted By: Mel_Gibson
Date Posted: 04 December 2020 at 3:13pm
Right I received an email reply from Beyma about the ports on the 21LEX1600nd enclosure plans supposedly being too small as said on this forum and they said word for word :

Good morning

 

I paste below the answer from our R+D Department.

 

Thanks a lot for your interest in our products and for your question.

We can assure you the cabinet is tested and the ports size is 100% correct. If there is any doubt we would appreciate a reason to claim the ports design are “too small”.

According to our measurements and listening tests the ports are correct.

We hope this information helps.

 

Kind regards

Rebeca Rodríguez



Posted By: Noyzmunky
Date Posted: 04 December 2020 at 3:56pm
''We can assure you the cabinet is tested and the ports size is 100% correct when you consider the compromises inherent in the design...''


There, I fixed their reply for you. I can well imagine your email to them having read your replies on here... Were you expecting anything else to come back from them than ''it's fine''

-------------
my name is Inigo Montoya...you killed my father, prepare to die!.


Posted By: smitske96
Date Posted: 04 December 2020 at 7:13pm
Originally posted by Noyzmunky Noyzmunky wrote:

''We can assure you the cabinet is tested and the ports size is 100% correct when you consider the compromises inherent in the design...''


There, I fixed their reply for you. I can well imagine your email to them having read your replies on here... Were you expecting anything else to come back from them than ''it's fine''

This.


Posted By: Mel_Gibson
Date Posted: 04 December 2020 at 7:52pm
Originally posted by Noyzmunky Noyzmunky wrote:

''We can assure you the cabinet is tested and the ports size is 100% correct when you consider the compromises inherent in the design...''


There, I fixed their reply for you. I can well imagine your email to them having read your replies on here... Were you expecting anything else to come back from them than ''it's fine''

Well they tested the enclosure and got peaks of 137db with pink noise with a 6db crest factor so all I can say to you is :





Posted By: Mel_Gibson
Date Posted: 04 December 2020 at 9:57pm
By the way I was joking with that little kid and her face, lol. But seriously ok if the ports ARE too small what size ports would be ideal? Plus also i'm rubbish at carpentry so would getting a cabinet maker to make me up the enclosure be a good idea? If I had a decent plan for him to follow I mean. I've tried using WinISD and I have no idea so rather than take months to learn how to use it and learning to understand the results i'm seeing i'd rather get an enclosure designed as well as made. 


Posted By: Contour
Date Posted: 05 December 2020 at 9:39am
The ports indeed may be perfectly sized for the required optimal reflex tuning, but same tuning can be achieved using larger area, but longer port. The larger port area results in less port losses and higher output. In some cases however, the ports are designed so small on purpose, it effectively changes the cabinet tuning to a higher frequency when the driver warms up and it T/S parameters change, resulting is a more optimal design when the driver is working on its limit.  

Best regards,

Walter


Posted By: Mel_Gibson
Date Posted: 05 December 2020 at 11:01am
Thank you Walter for your excellent detailed reply that helps me a lot, one problem I have is, Beyma measured the peak SPL output at 137db using pink noise with a 6db Crest Factor I can't see how you could get more output from a single 21" reflex sub than that. So making the ports bigger would you say it's reasonable that even doing that would result in SPL output being not even noticeably higher? Unless it's gonna get 3db or more higher output it's probably not worth taking the time to design an enclosure with bigger ports as it'd mean pretty much re-designing the whole enclosure and testing it out once built then adjusting all for less than for example 3db output. 


Posted By: Chris Grimshaw
Date Posted: 05 December 2020 at 12:49pm
Originally posted by Contour Contour wrote:

The ports indeed may be perfectly sized for the required optimal reflex tuning, but same tuning can be achieved using larger area, but longer port. The larger port area results in less port losses and higher output.


... With the compromise that the larger ports directly mean a larger cabinet.

There's also the potential for 1/4-wave resonances to mess up the top of the bandwidth.


The time when under-sized ports become obvious is when you're demanding full output at/near the port tuning frequency. Whether that's likely to happen will depend entirely on the program material.

Example: https://www.youtube.com/watch?v=UnQY3swM4tA" rel="nofollow - https://www.youtube.com/watch?v=UnQY3swM4tA (caution - lyrics are nsfw)
Has a very compressed bass line which gives subs a hard time. If your port is tuned to 36Hz, you better make sure it has lots of area. You'll also need to make sure the magnets on the drivers are adequately ventilated.

Most program material isn't so demanding, and you can "get away with" smaller port areas without suffering much/any compression.

Chris


-------------
Quality sound from Sheffield
www.grimshawaudio.com


Posted By: Mel_Gibson
Date Posted: 05 December 2020 at 2:07pm
Originally posted by Chris Grimshaw Chris Grimshaw wrote:

Originally posted by Contour Contour wrote:

The ports indeed may be perfectly sized for the required optimal reflex tuning, but same tuning can be achieved using larger area, but longer port. The larger port area results in less port losses and higher output.


... With the compromise that the larger ports directly mean a larger cabinet.

There's also the potential for 1/4-wave resonances to mess up the top of the bandwidth.


The time when under-sized ports become obvious is when you're demanding full output at/near the port tuning frequency. Whether that's likely to happen will depend entirely on the program material.

Example: https://www.youtube.com/watch?v=UnQY3swM4tA" rel="nofollow - https://www.youtube.com/watch?v=UnQY3swM4tA (caution - lyrics are nsfw)
Has a very compressed bass line which gives subs a hard time. If your port is tuned to 36Hz, you better make sure it has lots of area. You'll also need to make sure the magnets on the drivers are adequately ventilated.

Most program material isn't so demanding, and you can "get away with" smaller port areas without suffering much/any compression.

Chris

In your opinion Chris which ports are the best overall shape? 


Posted By: Contour
Date Posted: 05 December 2020 at 2:11pm
Round, has the best ratio port area versus port wall surface. Use a very big radius at start and end of the port, google intertechnik jetset for an example. 


Posted By: Mel_Gibson
Date Posted: 05 December 2020 at 2:46pm
Don't round ports suffer more from the chuffing sound? I heard the chuffing sound on some old hi-fi speakers years ago and it sounded unpleasant. 


Posted By: jammin75
Date Posted: 05 December 2020 at 3:04pm
Originally posted by cravings cravings wrote:

it's yet another account for djteknovibe / Jack_The_Ripper / richard stringer / Fred_Dibnah / richardstringer1993... so he's in Boston in Lincolnshire.


Originally posted by Fred_dibna Fred_dibna wrote:

I have a quick port question, are circular, triangular or under driver slot ports best? The driver will be the RCF LF18X401, cabinet tuned to 36hz and i'll be powering a pair with a bridged QSC RMX4050HD giving the subs a combined 4k.

I was just curious, thanks.




LOL


-------------
feel the vibes !!!   "Who Feels it Knows it"            Strong like Lion              


Posted By: smitske96
Date Posted: 05 December 2020 at 4:36pm
Round ports would be the best, but can be difficult to omplement if they need to be long (and enough cm2). Slot ports can make inplementing much easier. The point in the end is that triangle shaped ports need to be bigger to be equal in terms of compression and the resulting distortion.
If you use said port area, you would get velocity of around 26m/s (with 1600 Watt AES input). If you go with something like 800cm2 you'll around 18m/s. I have write up somewhere from a fb forum were the 3 ports are compared. 

Personally i don't dig the 6dB crest factor measurements a lot (for any manufacturer). It only tells you one part of the story. Therefore I think CEA2010 would be more suitable.




Posted By: MarjanM
Date Posted: 05 December 2020 at 4:49pm
Why dont you just buy some subs? DIY is not always the answer.

-------------
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: Mel_Gibson
Date Posted: 05 December 2020 at 5:09pm
Because I can't afford subs that would give me the same performance as the custom subs i'm thinking of building or having built. I'd say to buy a pair of subs 21" that would be as good as ones I can custom make would probably cost about £1,500 each.


Posted By: MarjanM
Date Posted: 06 December 2020 at 12:36am
And what is your actual budget? 
BTW that Beyma 21 inch is not in the highest ranks of 21 inch drivers.


-------------
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: knet94
Date Posted: 07 December 2020 at 12:15pm
Originally posted by Mel_Gibson Mel_Gibson wrote:

Because I can't afford subs that would give me the same performance as the custom subs i'm thinking of building or having built. I'd say to buy a pair of subs 21" that would be as good as ones I can custom make would probably cost about £1,500 each.

I can't see the design that you have posted up costing anywhere near £1,500 each to build. 
https://www.beyma.com/wp-content/uploads/S-121LEX-SYSTEM-1.pdf" rel="nofollow - https://www.beyma.com/wp-content/uploads/S-121LEX-SYSTEM-1.pdf


Posted By: knet94
Date Posted: 07 December 2020 at 12:18pm
Have you considered going the 2nd hand route. Seen some really good cabs going for small money recently. Tho tbh far bigger than the Beyma ones.


Posted By: smitske96
Date Posted: 07 December 2020 at 1:37pm
Originally posted by knet94 knet94 wrote:

Originally posted by Mel_Gibson Mel_Gibson wrote:

Because I can't afford subs that would give me the same performance as the custom subs i'm thinking of building or having built. I'd say to buy a pair of subs 21" that would be as good as ones I can custom make would probably cost about £1,500 each.

I can't see the design that you have posted up costing anywhere near £1,500 each to build. 
https://www.beyma.com/wp-content/uploads/S-121LEX-SYSTEM-1.pdf" rel="nofollow - https://www.beyma.com/wp-content/uploads/S-121LEX-SYSTEM-1.pdf

He meant a factory cab with that 1500 each.
Secondhand would also be a good one. You can get some hefty subs for that kind of money (or even less).


Posted By: Mel_Gibson
Date Posted: 08 December 2020 at 8:55pm
Yeah I meant to buy a brand new subwoofer which would or could be as good as a custom made one using the Beyma 21LEX1600Nd I believe would cost around £1,500 brand new. Obviously it wouldn't cost £1,500 to custom make the subwoofer. The driver is around £450 but I have no idea how much someone would charge me to build me an enclosure for the driver. 


Posted By: Mel_Gibson
Date Posted: 08 December 2020 at 8:58pm
Originally posted by knet94 knet94 wrote:

Have you considered going the 2nd hand route. Seen some really good cabs going for small money recently. Tho tbh far bigger than the Beyma ones.

Yeah I have but one problem is finding the right pair of subs that are as compact as the Beyma 21LEX1600Nd Beyma enclosure plan which could give me the same kind of spl output and depth of bass is i've found near impossible. Even a pair of Martin Audio WS18x are smaller, tuned higher and wouldn't be as loud spl wise. 


Posted By: Mel_Gibson
Date Posted: 08 December 2020 at 9:06pm
Originally posted by MarjanM MarjanM wrote:

And what is your actual budget? 
BTW that Beyma 21 inch is not in the highest ranks of 21 inch drivers.

Maybe not their 21" but their 18LEX1600Nd I read somewhere was voted by Pro Sound Web as the best subwoofer driver in 2014. I don't mind going for the RCF LF21X451 driver it's cheaper, has an xmax of 14mm, it's rated at being able to handle 2,000 watts continuous average power and according to the frequency response chart is -3db at 45hz which I believe is free air and has a sensitivity of 98db at 55hz with a pretty flat'ish curve. It states it's good for reflex as well as horn loading. 


Posted By: Mel_Gibson
Date Posted: 10 December 2020 at 8:49pm
If I was to buy an RCF LF21X451 driver who could design and build me an enclosure for it and how much would it cost? 


Posted By: MarjanM
Date Posted: 11 December 2020 at 1:46pm
I dont really have much time for internet these days, but you should know few things.
That Beyma 21 inch driver is not that good as you think it is. 
One good reflex 21inch sub will never be louder then two good 18 inch subs. 
It might go lower, but not in a "compact" box.

If you buy any driver for like 450, and you pay 350-400 or so for the box, (which i purely speculate the cost) , how will that box look at the end?
Will it have professional box fit and finish?
What will be its resale value?

I am all for a DIY, but not when you can not actually do it your own but you have to pay someone to make it for you. That does not make any economical logic. At the end you will spend 1000 for a box that will kind of look well done, but not as good as a professionally made one.


-------------
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: Mel_Gibson
Date Posted: 11 December 2020 at 8:46pm
Are you saying a properly designed and built sub for example using the RCF LF21X451 won't be as good as a big name manufacturer sub that costs £1,000 new?


Posted By: MarjanM
Date Posted: 11 December 2020 at 11:27pm
I am saying that for 1000 pounds you can not make them looking like this. 






-------------
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: MarjanM
Date Posted: 11 December 2020 at 11:28pm
Or like this. 

-------------
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: Mel_Gibson
Date Posted: 12 December 2020 at 10:43pm
Thank you Marjan for your advice, your subs are beautiful but way out of my price range I live on a council estate and am poor, i'm a poor guy with a passion buring inside me for dj'ing and doing dance music parties but my lack of money is such an obstacle it's hard to decide what the best route for me is. 

Anyway thanks again mate.
Smile


Posted By: MarjanM
Date Posted: 13 December 2020 at 12:49am
My advice to you is to be patient and wait for a bargain on the used market. 
At this time many rental companies are trying to off load some of their gear in order to survive the crisis.
Here is one example of a pair of very solid double 18 inch box that goes for very little money.

https://gebrauchte-veranstaltungstechnik.de/ad-549564-JBL+SRX+728s+" rel="nofollow - https://gebrauchte-veranstaltungstechnik.de/ad-549564-JBL+SRX+728s+


-------------
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: Mel_Gibson
Date Posted: 13 December 2020 at 9:52am
Thanks Marjan.

:)


Posted By: bob4
Date Posted: 20 March 2021 at 9:41am


Bit late to the party........

This is a Josh Ricci Ckram (without front chamber attachment)
https://data-bass.ipbhost.com/topic/868-riccis-ckram-subwoofer-and-files/" rel="nofollow - https://data-bass.ipbhost.com/topic/868-riccis-ckram-subwoofer-and-files/

Loaded with B&C 21DS115, built by a friend of mine upon my suggestion.

Roughly about the same size as the beyma plan, but with a slot port with roughly twice the surface area, and nearly 1m port lenght in L shape. The tuning is exactly 30 Hz. 

It goes flat to 30 Hz, according to Joshs akabak simulation about 92 -93 dB sensitivity at 30 Hz! Averages about 95-96 dB in the upper band. Without processing. 

Box is mostly rebated, hasnt been glued up yet, currently assembled for testing with screws only. With most of the bracing in place, it is already quite impressive. We run it on a bridged yamaha h7000, and have not managed to get the amp to clip in the small workshop we are currently confined to by the weather. We have also not been able to get the ports to chuff yet. It sounds balanced,  very round and punchy, and plays all the sub 40 Hz stuff with authority. 

I assume the Beyma design you were talking about is this:
https://www.beyma.com/wp-content/uploads/S-21LEX1600-SYSTEM-2021-1.pdf" rel="nofollow - https://www.beyma.com/wp-content/uploads/S-21LEX1600-SYSTEM-2021-1.pdf

If you check the Beyma pdf, except for the unrealistic peak spl figure (without frequency reference!!!), the response of the box is 6-7 dB down at 30 Hz.
 This means  that  
1) the actual sensitivity of the beyma design at 30 Hz is 99 -6 = 93 dB AT BEST , but probably lower, plus the likelyhood of strong port compression and  chuffing
2) you will have to apply serious eq to get a flat response down to 30 Hz.


 To add further smoke and mirrors, their response graph is normalized, not telling you the true sensitivity of the design.

There is also a chart of eq settings, with a 2,5 dB boost at 45 Hz. 
If you look at the lenght of the triangle ports it is very obvious that the box is tuned very high, not lower than 45-50 Hz. 

Based on my experience i would strongly recommend the ckram in standard reflex configuration over this beyma design. I don't think the beyma design is any good if you need flat response down to 30 Hz.






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