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Advice on tuning for multiway

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Nut84 View Drop Down
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    Posted: 10 March 2023 at 2:16pm

Hello,


I'm new to this forum, although have been reading a lot of posts on here, but now need to reach out for some specific help! 


I have been designing a system that is quite large, and am right about at the stage to build test cabs to take measurements from to then fine tune before the actual build begins.


I have been doing as much homework as possible over the past couple of years, reading, researching, and recently plotting on WinISD.


But have some questions regarding tuning and cut offs of the bass cabs and how they should work together that I cant find the answer too, or rather get my head around!


The system will be a 4-way to be used as a pa at various small events and eventually finding a permanent home in a venue.


The drivers are as follows:


Sub: JBL 2241G

Mid Bass: TAD 1601A

Mid High: Altec 299 mated to JBL 2360a Horn (I will also build and test multicell horn in future)

High: JBL 2405


These will be bi-amped with active crossover / DSP


The actual construction / carpentry design of the cabs is not an issue at all, but rather the physics of tuning and cut off etc.


Because I have taken T&S parameters from each driver using DATS V3, there are slight differences between the two JBLs and the two TADs. So I have plotted all 4 drivers in WinISD to get a good median design. The parameters also differ from the official JBL literature.


JBL 2241G:

My parameters:

Fs 44.18Hz & 40.51Hz

Vas 271L & 318L

Qts 0.48 & 0.44


Official:

Fs 35Hz

Vas 310L

Qts 0.40



TAD 1601a:

My parameters:

Fs 32.33Hz & 33.24Hz

Vas 394L & 388L

Qts 0.37 & 0.38


Official:

Fs 28Hz

Vas 307L

Qts 0.34


The differences between the respective drivers when plotted in WinISD with the same tuning and volume are minimal, so I am not too worried about that.

Below are some screen shots from WinISD for both the JBL (Yellow) and TAD (Blue).


Current enclosure plots are:

JBL 2241G - 300L / 38Hz

F3 around 39Hz


TAD - 150L / 35Hz

F3 around 48Hz


Transfer Function

1678453187074.png


Group Delay

1678453201947.png


Rear Port Velocity

1678453214347.png



I am not completely fixed with the volume or tuning, and I am sure these will change after some input from others. size of enclosures is not an issue either.


Obviously this does not take into account where the x-over points will be, and that is where I need some advice: The relationship of tuning depending on x-overs


I can see that both the JBL and TAD drivers are not too dissimilar with what can be achieved.


The 18" JBL will purely be for the additional low end, where as the 15" TAD will be crossed higher for mid bass, which is not plotted. crossover point are yet to solved / decided!!


Say for example I crossed these drivers at 100hz (that may be completely wrong) Does that mean I do not have to worry so much about the tuning of the 15" TAD as it will cut off above tuning? How will this affect tuning and response etc?


Should I be designing with crossover points in mind? and too what degree or tolerance?


I also have read differing info on whether to tune above or below F3?


And how does tuning the enclosure relate to the Fs? Does it matter how close they are?



Any help or advice is very much appreciated.

I have tried to clearly explain as much as possible!


Thank you

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snowflake View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 10 March 2023 at 3:23pm
do you need your mid-bass section to be reflex cabinets?
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Nut84 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nut84 Quote  Post ReplyReply Direct Link To This Post Posted: 10 March 2023 at 3:48pm
Hi,

When I inputted all parameters into winisd it highly suggested reflex over sealed. And all cabinets I've seen for that tad driver are reflex.

That's not to say I'm against sealed. I want what's best for overall sound.

 I guess I can seal any ports with the test cabs and adjust size.

What are you thinking??

Cheers 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lucasdude Quote  Post ReplyReply Direct Link To This Post Posted: 10 March 2023 at 4:19pm
The specs for the 2241 have a relatively high Qts and fairly low Xmax, so a reflex enclosure tuned to no lower than fs with a steep HPF just below should ensure no over excursion at max power. Check the port velocity for audible chuffing as the original JBL cabinets did suffer from this at high power levels.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 12 March 2023 at 4:42pm
Originally posted by Nut84 Nut84 wrote:

Obviously this does not take into account where the x-over points will be, and that is where I need some advice: The relationship of tuning depending on x-overs

I can see that both the JBL and TAD drivers are not too dissimilar with what can be achieved.

Should I be designing with crossover points in mind? 

YES. Unless the system will sometimes be used without the 18" subs there is no need to build the mid/bass cabs as big as they would need to be to maximize the lowend response from those drivers. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nut84 Quote  Post ReplyReply Direct Link To This Post Posted: 13 March 2023 at 8:32am
Cool, thanks for the help
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nut84 Quote  Post ReplyReply Direct Link To This Post Posted: 13 March 2023 at 8:33am
Cheers for advice. Much appreciated 
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