4344 Active Project

[ayaboh]

Cool project! I like heavily braced designs too. Instead of 25mm plywood, I think you would find a slight improvement with 13mm MDF covered in 13mm birch ply. The bass will be slightly tighter with slightly less box loss.

If you don't mind, I'd love iges files of your drivers... I have been too lazy to build such nice examples.


Widget

Widget and Mats;

I can try to export the driver models to iges. I don't know if this will destroy the styles and formatting.

[Earl K]

Hi Earl.
Are you taking about the pole vent outlet,

-Yes, mostly that's my point .
- I'm concerned your bracing is too close to the vent outlet in the 2235s' magnet.
- JBL recommends at least 3 inches of clearance ( according to the 2226H spec sheet )

or is it that the bracing is to close to the magnet?
I think the clearence is 2 inches, but I have to check my drawings to be sure.

- Great drawings ! ( again )

[4313B]

Sorry, I don't have the equipment for that. Is this necessary because of the internal bracing/sub struc or the increased volume? If this throws the impedance and response for the 2235 way off, it will be much easier to copy the original 4344 cabs instead.

Yes, you're going to have to determine if that kind of bracing solution is going to negatively affect the response and tuning. Standing waves show up as blips in the impedance curve. When you tune an oscillator to those blips the resulting cacophony is usually quite irritating. You then try to damp them. I don't really have time to count how many standing waves this particular bracing solution is introducing right now but you probably get the idea. Usually the goal is to get the bracing to appear transparent to the volume or to get the standing waves so high in frequency relative to the intended badwidth that their effect is minimized.

[Mr. Widget]

Widget and Mats;

I can try to export the driver models to iges. I don't know if this will destroy the styles and formatting.

I would expect your nice looking foilcals will be lost, but the basic geometry should be fine. I'd really appreciate it if you could give it a shot and send me a PM.

Mr.Widget what drivers do you have on cad ?

I have only done place holders... that look close from the front... I've never taken the time to accurately build a driver.

BTW: I use Solidworks too. I is great for machine parts, but kind of sucks as a surface tool and it hates complex fillets and the like.



Widget

[Mr. Widget]

Sorry, I don't have the equipment for that. Is this necessary because of the internal bracing/sub struc or the increased volume? If this throws the impedance and response for the 2235 way off, it will be much easier to copy the original 4344 cabs instead.

Giskard makes a good point... all of those parallel surfaces can lead to some audible problems... every box has internal standing waves, it's the magnitude and frequency that are the issues.

One possible partial fix would be to angle each of your horizontal braces... it makes construction a bit more of a pain, but it does reduce the effect of standing waves.

As for measurement equipment, there is an inexpensive device that you can buy to measure your speakers' impedance. It is called the WT2.

http://www.woofertester.com/


Widget

[4313B]

every box has internal standing waves, it's the magnitude and frequency that are the issues.

And to use this opportunity to answer the people who have posted that "some subwoofers are cubes". Invariably those cubes are quite small (meaning the standing wave frequency is higher as opposed to lower) and the low pass filters set so low, and are of sufficiently high order, that the standing waves are "adequately" attenuated. Think "signal to noise", where the standing waves are the noise.

[Ian Mackenzie]

It looks very nice.

One potential issue might be buzzes and other nodal resonances with all those compartments. The other thing is assuming you intend to add fibreglass to all surfaces, the additional surface area of all those internal panels will increase the volume of Fill and this may effect the final tuning and the apparent bass quality.

If you are at all concerned about noise, put the ports anywhere but the front baffle. Reflex ports can be a significant contributor of audible internal enclosure noise (via the vent)

[WTPRO]

Hi

Regarding the final tuning, another Woofer Tester feature is the ability to measure and analyze the in box driver impedance to come up with an effective box size and tuning. This example is pretty typical when using the Rem/Xem measurement and modeling. This driver in particular is representative of a driver with a high Rem/Xem. In this case I am comparing the simulators driver output to the measured driver output. The port in this case is somewhat isolated and on the back side of the box. The in air measurement was made using a Woofer Tester Pro (that I am madly trying to get finished for the Xmas shopping season, along with the Speaker Tester).

For those not familiar with Rem/Xem, you can think of 'Le' as being a variable where 'Le' is the effective inductance at 1 Khz. I highly recommend using the Rem/Xem data and simulator, but we also support Le and 'none' if you need to compare with older models or methods.

Another feature people may not be aware of is that the WT can also measure Cms variation with drive level. Please check our FAQ for further information on that topic.

It may also be worth mentioning that we are also now a distributor for the Harris Tech 'Bass Box' products.

Best regards,
Keith Larson, WTPro
Smith and Larson Audio
www.woofertester.com

[4313B]

Nice job Keith!

[ayaboh]

Widget and Mats (and other);

You can get the IGES files here http://www.designcut.com/4344/Iges.zip and driver foilcals here http://www.designcut.com/4344/Driver%20Foilcals.zip.

[ayaboh]

Yes, you're going to have to determine if that kind of bracing solution is going to negatively affect the response and tuning. Standing waves show up as blips in the impedance curve. When you tune an oscillator to those blips the resulting cacophony is usually quite irritating. You then try to damp them. I don't really have time to count how many standing waves this particular bracing solution is introducing right now but you probably get the idea. Usually the goal is to get the bracing to appear transparent to the volume or to get the standing waves so high in frequency relative to the intended badwidth that their effect is minimized.

Yes, this can be a problem, but have any of you looked inside a B&W matrix cabinet? They don't seem to be concerned about all these parallel surfaces. Another thing, (and I have not checked or tried to calculate this) is the space inside a cab like this, large enough to support standing waves at the frequencies we are talking about, or is structure borne waves the problem?

Anyway, I will finish a model of an original 4344 according to Ian's plans. It is nice to have a complete set of production drawings for this speaker, and as a bonus, all the errors and typos shows up when you make a full 3D model.

[ayaboh]

It looks very nice.

One potential issue might be buzzes and other nodal resonances with all those compartments. The other thing is assuming you intend to add fibreglass to all surfaces, the additional surface area of all those internal panels will increase the volume of Fill and this may effect the final tuning and the apparent bass quality.

I have been thinking about thin Neoprene foam mats on the dividers.

If you are at all concerned about noise, put the ports anywhere but the front baffle. Reflex ports can be a significant contributor of audible internal enclosure noise (via the vent)

All the original JBL monitors have the ducts on the front.

[Robh3606]

All the original JBL monitors have the ducts on the front.

That is because of how they would typically be mounted in use. You don't have those constraints. Unless you are going to actually make exact copies which you obviously are not with the bracing and active crossovers keep an open mind. There are better ways to do them including changing the layout of the drivers, particulary the 2235, and getting the vents off the baffle board and away from the 2122 as an example compared to the original layout. Ports on the back is a good option.

Rob

[matsj]

ayaboh thanks alot. I will take a look at it when i come home.

regards mats

[Mr. Widget]

Widget and Mats (and other);

You can get the IGES files here http://www.designcut.com/4344/Iges.zip and driver foilcals here http://www.designcut.com/4344/Driver%20Foilcals.zip.

Thanks! I just downloaded them, but am on my Mac... I'll have to wait until I boot up my PC to check them out... I'll let you know how it works out.


Widget