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

Group Delay

Rear Port Velocity

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