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Old 29th October 2012, 11:08 PM   #1
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Join Date: Jul 2004
Location: Kayseri/Turkey
Default Speaker enclosure design confusion !

Hi everbody

I wanted to find some good designs of a studio reference monitor for mostly learning and maybe building one in future , I searched and searched and found a few good designs and I started to gather any info I could find ...
and before I continue , I know designing a speaker is not a easy job and it s more complicate when you wanna design somethin as accurate as a reference studio monitor , but if I can learn it ,why not ! and I know I need some equipment for measuring that I don have ,but it s not what confuse me right now ... and one thing else forget about the crossover I am a fan of bi-amping and active crossovers ...

so I found a few good design and start to compare them together and start to read a few things about designing a loudspeaker and things become complicate for me ! , I found a very good design at Zalph Audio (ZA-SR71) for studio monitor and when I put the woofer driver parameters in speaker design volume calculator I found the almost exact same parameters for volume as it is in the Zalph Audio project , but when I do the same thing for Vance Dickason LDC6 studio monitor design I get some results far different from the volume of the enclosure that Vance designed !
same results when I compare my calculations with some other high end loudspeaker designs ... so now I confused , for example why Vance 's encloser for Seas 18/8545k00 is almost half of the size of the volume that I calculate with the same parameters ?! in madisound the recommended volume for Seas18/8545k is 0.25 for f3 of 84 in sealed design ,almost the same as my calculation and for lower f3 you have to go ported, but in Vance designs (I know it s an older version driver with different parameters) for a f3 of 50 Hz the sealed enclosure volume is 0.28 ft3 but with same parameters that Vance used my calculation for f3 of 50hz it needs 0.85 ft3 , so how is it ?!
same story goes with other designs , some volume size and other parameters are same or slightly different from what I got but some are much different , I wonder how and why ?!!!
I would be so grateful if you guys can help me out
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Old 30th October 2012, 01:51 AM   #2
Dissi is offline Dissi  Switzerland
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Join Date: Sep 2012
Location: Winterthur
A simulation of the LDC6 unravels the mystery. The spl at 50 Hz is 8 dB down. 50 Hz is never f3, it's around 82 Hz, as predicted by theory. The reference level is actually 85 dB, but the designer uses a large coil of 3mH, causing a falling frequency response above 150 Hz.

SimulationLDC6.jpg
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Old 30th October 2012, 02:09 AM   #3
pski is offline pski  United States
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Join Date: May 2011
Location: Flatrock Community, GA, USA
Quote:
Originally Posted by Ahmad_tbp View Post
Hi everbody

I wanted to find some good designs of a studio reference monitor for mostly learning and maybe building one in future , I searched and searched and found a few good designs and I started to gather any info I could find ...
and before I continue , I know designing a speaker is not a easy job and it s more complicate when you wanna design somethin as accurate as a reference studio monitor , but if I can learn it ,why not ! and I know I need some equipment for measuring that I don have ,but it s not what confuse me right now ... and one thing else forget about the crossover I am a fan of bi-amping and active crossovers ...

so I found a few good design and start to compare them together and start to read a few things about designing a loudspeaker and things become complicate for me ! , I found a very good design at Zalph Audio (ZA-SR71) for studio monitor and when I put the woofer driver parameters in speaker design volume calculator I found the almost exact same parameters for volume as it is in the Zalph Audio project , but when I do the same thing for Vance Dickason LDC6 studio monitor design I get some results far different from the volume of the enclosure that Vance designed !
same results when I compare my calculations with some other high end loudspeaker designs ... so now I confused , for example why Vance 's encloser for Seas 18/8545k00 is almost half of the size of the volume that I calculate with the same parameters ?! in madisound the recommended volume for Seas18/8545k is 0.25 for f3 of 84 in sealed design ,almost the same as my calculation and for lower f3 you have to go ported, but in Vance designs (I know it s an older version driver with different parameters) for a f3 of 50 Hz the sealed enclosure volume is 0.28 ft3 but with same parameters that Vance used my calculation for f3 of 50hz it needs 0.85 ft3 , so how is it ?!
same story goes with other designs , some volume size and other parameters are same or slightly different from what I got but some are much different , I wonder how and why ?!!!
I would be so grateful if you guys can help me out
What your are told is not always what you get.

For monitors, look at the most successful monitors and finds something close. Measurement parameters are not so important as the installation location.

Hence: JBL 4311

This speaker was the basis for the Century 100 and later monitor models.

They are very efficient and have front panel crossover controls that were widely abused.

Their properties are well known and models are available to buy. (There is no letter after the model except on speakers you don't want to buy.)



Well known improvements (TROELS) are also well documented.
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Old 30th October 2012, 10:49 AM   #4
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Join Date: Jul 2004
Location: Kayseri/Turkey
so if I got it right , the calculation was right and f3 should be around 80hz not 50hz in a 0.28 ft3 sealed box , and if I understand it right ,by using a large coil ,he somehow make it sound bigger ?! (by causing the freq respond falling above 150)

I read about the 4311 it s a revolutionary design for its time , some of the theories and innovations are used in various designs , but today's designs are much different and much more accurate to fit today's needs ... and I read a lot about monitor placement and room acoustic balance and etc ,and I know that without a calculated and controlled placement and acoustics you can not have a accurate sound , and it s not about that , it s about the enclosure itself design , and I was confused should I trust my calculation for designing a loudspeaker or not ...
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