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Old 21st October 2011, 09:19 AM   #21
spot is offline spot  Australia
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Just to confuse things more I'm thinking now of the 15" HO or HF, about the same price a the 12".

How much does keeping the Q low (critically damped) matter?
Bear in mind I intend to use a Linkwitz transform to reshape the response and the Q.
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Old 21st October 2011, 03:31 PM   #22
Tytte71 is offline Tytte71  Norway
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Quote:
Originally Posted by spot View Post
Just to confuse things more I'm thinking now of the 15" HO or HF, about the same price a the 12".

How much does keeping the Q low (critically damped) matter?
Bear in mind I intend to use a Linkwitz transform to reshape the response and the Q.
To my opinion, you don't have to bother on a critically damped system. A Qtc of 0,7 would do perfect. Qtc. of 0,7 is easy to equalize and the basis for the impulse response is just fine.
You should remember that the group delay and impulse reponse is in anyway changed when you put in filters and not least when you put the sub into your listening environment.

The greatest benefit of low Q (increasing volume) in this application is the extra output you gain in the low frequency region.
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Old 21st October 2011, 04:46 PM   #23
tb46 is offline tb46  United States
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Hi spot,

Post #21: "...Bear in mind I intend to use a Linkwitz transform to reshape the response..."

Take a close look at the attached article: ESP - The Linkwitz Transform Circuit

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Old 21st October 2011, 09:29 PM   #24
spot is offline spot  Australia
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Originally Posted by tb46 View Post
Hi spot,

Post #21: "...Bear in mind I intend to use a Linkwitz transform to reshape the response..."

Take a close look at the attached article: ESP - The Linkwitz Transform Circuit

Regards,
Yes that's an interesting article on the perils of too much freq extension with the Linkwitz transform, but I haven't been able to find anything on the practical realities of using a box/driver with higher Q and reducing the overall Q.
Theoretically if the filter was matched perfectly to the speaker, and the speaker behaved purely as the model, then the original Q cancellation should be perfect, but if that was the case we wouldn't be discussing which is the best speaker from a distortion point of view.
From a frequency response perspective, starting with lower Q does help with needing less power at lower frequencies though (a little bit).
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Old 22nd October 2011, 12:51 AM   #25
tb46 is offline tb46  United States
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Hi spot,

The Linkwitz Lab Thor subwoofer has a complete desing run-down that can be used as a guide for any sealed equalized subwoofer: THOR - subwoofer

As to the Dayton RSS390HO-4 v. HF-4: looks like both can be made to work in a 1.75ft^3_net box (Posts #1, #21) using the Linkwitz transform. The HO calls for a smaller box initially, but, as you are considering applying electronic equalization, the HF can be made to work in this relatively small box too, and the HF has 2mm more Xmax. It'll take some playing back and forth with the Linkwitz transform spreadsheets to arrive at a design.

Another similar form of sealed subwoofer equalization is described in: Sub-Woofer Controller

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Old 22nd October 2011, 07:16 PM   #26
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Sub-Woofer Controller

Quote:
Siegfried Linkwitz [3] developed a circuit that equalises the bottom end of the system, but does not affect the higher frequencies. This is shown and described fully in Project 71, and must be used with a crossover. Although it offers several advantages over the EAS system described here, it is also much more reliant on your detailed knowledge of the loudspeaker driver parameters.

Is there a thread here, or a page elsewhere, that discusses some of the pros/cons of these various approaches to small sealed sub EQ?

I'd be VERY interested in something that might be available with more 1-2-3 ABC instructions for the less sophisticated. There is also "Dayrl's RC filter mod" for the RSS HO and HF. It's discussed over at the TechTalk forum. Easier implementation, but very little real comment on its efficacy.

A small sealed RSS315HO-4, or RSS390HO-4 with the Elliot Sound extended low freq circuit.... Any successful examples posted out there? How tough would this be to get right for a relative electronics novice? Am I correct in thinking that it would be easier to put together correctly than the LT circuit? Are the HO RSS drivers definitively better for such sealed EQ'd applications than the HF?

Quote:
It'll take some playing back and forth with the Linkwitz transform spreadsheets to arrive at a design.
Anyone know of any posted designs for the Dayton RSS subs using LT?

And finally, I'm not sure how related the RC filter mod is to the other approaches, but it appears as if it functions somewhat independent of the amp. Rather I should say, it looks like once it's calcualted according to driver parameters, any amp can be swapped into the design. How much do the design of the other approaches depend upon the specific amp used?

Last edited by peace brainerd; 22nd October 2011 at 07:24 PM.
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Old 22nd October 2011, 07:22 PM   #27
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How about this one:

Super 8

Mike
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