Sealed 21w-54:s with Linkwitz transform

[Saibot]

Hello!

I'm considering putting 2 parallelled Dynaudio 21w-54:s in a sealed box of 50 litres and a variovent and then raise the total Q again using a Linkwitz transform circuit. However, i'm a little scared about the Xmax of this driver, its only 7 mm linear p-p (max 29 mm).
What performance can I expect from this ? My goal is to get deeper bass than with an equally sized vented box and at the same time better transient response...

Has anyone here used the 21w-54 in this manner and how was the result ?

/Tobias

[sreten]

Deep bass requires extension and SPL capability.

Vented is the only sensible option.

Try a 70 litre box tuned to your wanted bass extension.

sreten.

[phase_accurate]

The first Dynaudio box I ever heard used this woofer in an isobaric configuration (more than twenty years ago).
That was one of the cleanest bass-reproductions that I have heard so far !
Depending on how loud you listen and the usual program material your config could be worth a try. Maybe you should use two seperate chambers and Variovents.

Regards

Charles

[Saibot]

Is there a benefit of using separate chambers ? Wouldn't the excursion be halved and the sensitivity increase by connecting them in parallell using the same chamber ?

I've already built the box (albeit no holes yet) so separate chambers would require a lot of more work...

/Tobias

[phase_accurate]

The benefit of seperate chambers would be less influence between the drivers that can be caused by differences in their TSPs.

Regards

Charles

[Saibot]

The drawback would be the excursion is not halved since the drivers no longer share the same chamber ?

The excursion is what I am afraid of by using this approach, how much can they take. The linear Xmax p-p is only 7mm (max is 29). However, I've heard Dynaudio drivers can take a lot more than they actually specify but I really don't want to blow this driver, it's quite expensive...

Rod Elliot describes a subwoofer controller to amplify the whole rolloff. Would this be better than a Linkwitz transform or is it just another namn for the same thing ?

/Tobias

[phase_accurate]

The drawback would be the excursion is not halved since the drivers no longer share the same chamber ?

This would still be the case as long as the drivers are mounted as closely as before. If you don't have a separation yet, don't worry too much about it, there are many speakers out there that work with a single chamber and multiple drivers. With high-quality drivers (less parameter differences between drivers) you would have to care even less.

Do you intend to use it as a subwoofer or do you build two of these boxes (i.e. 2 x 2 drivers) ?

Regards

Charles

[Saibot]

The 21w-54 are for Puppy "clones" so they will be used as subwoofers.
A Watt "clone" will be placed on each. The rest of the elements are Focal TC120TDX and Seas CA17RCY. I call it "clone" since it is not really a clone, I won't use a passive crossover and the materials used is only MDF.


/Tobias

[phase_accurate]

In this case you can make quite some noise, though not as much as with a reflex enclosure. The original Watt/Puppy is bass-reflex and using the same woofers. I have never hard it (I only heard the Sophia once) but it must be capable of quite some low end SPL.

I currently listen to a system with a 20W75 in the bass and it is sufficient for me.

At least the never Dynaudio drivers are very rugged. I managed to run a 300W/ch P.A. amp into clipping on a box with a 17W75 LQ, and the woofer didn't bootom out ! The sound however was quite blurred. So they can take quite some short-term abuse, but this is of course not the intended long term usage.

Regards

Charles

[markp]

I have beaten 21w54s to what should have been their death but they would not die! I'm talking a Yamaha P2400 in mono at full blast! The xmax is under rated at 7mm and the power handling is low too. I used a sealed box with three chambers separated by 1" furnace fiberglass(really dense). It was 75l total, 25 in each chamber with the woofer in the center chamber. Tight low base is what I got.