Open Baffle natural roll off?
 

I am currently building a pair of dipole speakers similar in design to the Orion.

I am using a Seas L22RNX/P and 10" XLS woofer in a baffle with a width of 300mm and height 1000mm and a MiniDSP for the EQ and x-overs.

I have simulated my baffle design in EDGE, it is my understanding that dipole speakers exhibit a natural roll-off of 12dB/octave.

After I have notched the dipole peak I am left with the dipole roll off and -6dB at 100hz.

Rather than correct for the dipole roll off, could I just let the midrange roll off naturally and apply low pass LR2 to the woofer at 100hz?
Or am I missing something vital?

http://img571.imageshack.us/img571/9839/rolloff.jpg

Hi,

Yes you can. You could low pass lower down to extend the bass,
though your not going to get much SPL with 12" wide baffles.

BTW baffle loss is 6dB/octave not 12dB. Your extra roll-
off (not loss) is caused by using very low Qts drivers.
Your Edge sim only shows the baffle loss, 6dB/octave.

Final bass roll-off low down is 18dB/octave, 6dB due
to baffle loss and 12dB due to the drivers roll-off.

rgds, sreten.

Cross posts with Sreten.

In the Orion LW uses a Linkwitz transform to compensate for the low Q woofer, then uses a 6dB/oct shelf to correct for the OB roll off.

Opps, got my self in a muddle then.

The Peerless XLS 830452 woofer has a Q of 0.17, how would this affect it?

What would you set as the target Q in a Linkwitz Transform? 0.5?

It depends on what Q your're happy with, but people usually choose between 0.5-0.7.

Note here that the XLS drivers have a Q of something like 0.18 and a resonance close to 20Hz. These are the numbers you will use when setting the parameters for the LT and you will then pick the desired target fs and Q for it to equalise towards.

If you are wanting the main panels to give you extension down to say 40Hz, then picking a target Q of 0.7 + a target fs of 35Hz would be a good idea. If you combine this with a high pass with a Q of 0.7 and a corner frequency of 35Hz, then you will end up with an overall roll of centred on 35Hz with a Q of 0.5.

Do bare in mind that the XLS' fs and Qts will rise by a small amount when mounted on/in the baffle/frame.

Hi,

Crossed posts.

Rereading your post I've misunderstood your post and no you can't.

You need to model driver responses as well as the baffle loss.

Look at : https://sites.google.com/site/undefi...diy-sunflowers

A Qts of 0.17 sub in a 12" wide open baffle is a disaster area in all respects.
Baffle loss at 50Hz will turn a 10" driver into no better than a boxed 3" SPL.
Huge amounts of boost and power are required to produce piffling SPL.

rgds, sreten.

Rich,

You can target whatever Q you desire with available EQ tools, like the Linkwitz Transform. 0.5 would probably be an excellent target.

FYI, the Orion system does not use a Linkwitz Transform anywhere in the design. Q correction of the woofers is handled by a simple 6db/octave shelving filter.

Cheers,

Dave.

You can't handle Q correction with a simple shelving filter, I am sure I've seen a schematic or block diagram for the Orion that shows an LT on the woofers.

I forgot to mention, the 10" woofer will be mounted in an H-frame similar dimensions as the Orion.

I think I need to get outside and measure the responce of the baffle/driver and work out the shelf filter for the midrange and H-frame.

So there is no problem in using LT on the woofer then to achive a target of 35hz, Q=0.5 and a 6db/octave correction?