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21" reflext enclosure needed

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Mel_Gibson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mel_Gibson Quote  Post ReplyReply Direct Link To This Post 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. 

Edited by Mel_Gibson - 05 December 2020 at 11:02am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Contour Quote  Post ReplyReply Direct Link To This Post 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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mel_Gibson Quote  Post ReplyReply Direct Link To This Post 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. 

Edited by Mel_Gibson - 04 December 2020 at 9:59pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mel_Gibson Quote  Post ReplyReply Direct Link To This Post 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 :





Edited by Mel_Gibson - 04 December 2020 at 7:58pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post 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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Noyzmunky Quote  Post ReplyReply Direct Link To This Post 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!.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mel_Gibson Quote  Post ReplyReply Direct Link To This Post 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



Edited by Mel_Gibson - 04 December 2020 at 3:14pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mel_Gibson Quote  Post ReplyReply Direct Link To This Post Posted: 03 December 2020 at 3:19pm
Would rectangular ports located at the bottom give me better performance? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post 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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mel_Gibson Quote  Post ReplyReply Direct Link To This Post 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. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post 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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mel_Gibson Quote  Post ReplyReply Direct Link To This Post 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. 


Edited by Mel_Gibson - 03 December 2020 at 1:46pm
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