Dayton dma series pr question

swann

Member
2010-05-23 11:32 pm
Berlin
Hello,

i really like the small new dma series from dayton and that they have for each driver an fitting passive radiator, but...for proper alignment the mms is way to high for this small prs.
That's way i am asking is there a failure in the documents from dayton or do they have really this high mms?
For instance the dma105 pr has an over all weight of roughly 30 gram so way to much, to put in good use for such a small pr.
So it seems that all the extra weight is coming from the thread/bolt and fitting which is glued in the voice coil because they're using the same cone and material as the normal driver. But the normal driver has an mms of only 4,9 gram so if i would like to have let's say a box with roughly 6,5 liters netto for the dma105-4 with an f3 of nearly 56 hz i would need an pr of about 5 and a halve gram...to get a flat response. There for the pr's mms is to high to get it to good use.

So the question is, do they have it wrong in their specs, like the counted the extra weight of washers and nuts into the mms or do they had made it really so heavy?

May someone has had her or his hands on some of the pr from this series and can tell some more about it.


Swany
 

swann

Member
2010-05-23 11:32 pm
Berlin
@ replies

oh dear, thing is i have a simulation software...:).

But thing is if you don't have a flat response in your simulation you don't have one in your speaker...or nearly what ever software you use.
So i model with Aj horn...

It says 6 liters by 56 by f3, and this is as good as it gets by a simulation software. Proof it wrong by building it :-D.

Jokes aside...

I know that the mms of the dma driver to pr are to heigh, but that was the question...is there may be a wrong doing in their documents or is it really THE mms?!

Greets Swan.
 
Hi Swann,

I did some modeling with an excel worksheet developed by Jeff Bagby.

Loudspeaker Design Software

What I notice is there is an optimal size for every passive radiator. So you need a software where you can input both the mass and volume of box and judge the response by the response graph.

So in a way you need to input the mass of the radiator and vary the box volume to set the optimum frequency response. Unlike a BR where you have the liberty of controlling both your port length and volume.

So in your case 6 liters is the ideal volume for a 5.6 gram PR. But if you input in a mass of 20gram. It would recommend a smaller volume. The entire system could be viewed as a mass at the end of the spring system. The spring is the air in the box. If your mass is too heavy and the spring is not stiff enough the vibration does not transfer over properly.

So if you used a 5gram mass, you would require a 6L spring. But for a 20gram mass, you would require a stiffer spring (smaller volume) to ensure proper transfer of energy. The lighter the PR the more efficient the system is, but requires a bigger volume. A normal box for a 4" speaker would typically be about 3 to 4 litres for BR. That is one of the benefits of PR, allowing you to tune to a lower frequency compared to a similar BR box.

I have actually used one of the dayton ones, a 3" PR and optimum volume for 100Hz is about 1 litre.

I haven't tried simulating yours yet but you can the proposed software by Jeff Bagby. Only problem is this worksheet only works on older versions of excel.


Oon.
 
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