Use Linkwitz Transform to reduce size of Enclosure?

[Aucosticraft]

Shaun,
Never mind being late you are always welcome.

some questions I have are....

Is the graph of your own system?
Brown colored trace shows a fall below 20Hz have you applied HPF there? if yes What kind of ( is it LR4 or some other)?
Is the FR graph actual measurement by Mic. and then normalized?

cause the linearity it shows is very impressive.

And Would like to hear in very your own words. How is it when deep to 20Hz? Is F3 of 30Hz,40Hz don't make much difference when its listening ?

 

[Shaun]

Firstly, I forgot to mention, it is the opening few seconds of the track that I am referring to.

Is the graph of your own system?

Yes.

Is the FR graph actual measurement by Mic. and then normalized?

Yes

Brown colored trace shows a fall below 20Hz have you applied HPF there? if yes What kind of ( is it LR4 or some other)?
Is the FR graph actual measurement by Mic. and then normalized?

Yes. It is a combination: parametric EQ at 20Hz plus 2nd order Butterworth HPF at 2Hz. This was not done with excursion limits in mind; simply to match the target curve, roughly.

I second the recommendation by Sreten of using a peaking HPF instead of Linkwitz, as it performs both functions in one go. I have done this before (HPF with high Q).

The light blue trace is measured response of the woofer before filtering. Black is target response. Red is the filter/EQ transfer function, and dark blue is final response.

cause the linearity it shows is very impressive.

The measured graph is somewhat tailored at the low end to overcome noise issues in the measurement system. With the noise included, response seems to rise at the low end, which is not true. As it is now it is better representative of an ideal roll-off.

Would like to hear in very your own words. How is it when deep to 20Hz? Is F3 of 30Hz,40Hz don't make much difference when its listening ?

It makes a difference. With this driver (and this implementation) if there is deeps bass you will hear it and appreciate it. It, however, seems to be missing some mid-bass kick, which might be due to room issues or other cause which I have not yet discocered. Of course, with so much boost at the low end, max SPL is limited as I experienced with that track. But it's great to see the cone working.

 

[Shaun]

With this driver (and this implementation) if there is deeps bass you will hear it and appreciate it.

Or maybe the better term is "feel it".

 

[Aucosticraft]

I second the recommendation by Sreten of using a peaking HPF instead of Linkwitz, as it performs both functions in one go. I have done this before (HPF with high Q).

Yes I agree, completely. I had my same woofer system designed that way. The bass was bit loud but wasn't impressive. Rather I felt the bass is not a part of music.
I fear high GD is the culprit. Here I am posting one generated by WINISD.

 

[chris661]

Perhaps you need to work on integrating the subwoofer with the rest of the system. Try reversing the phase on the woofer, see if it melds better then...

 

[Aucosticraft]

Perhaps you need to work on integrating the subwoofer with the rest of the system. Try reversing the phase on the woofer, see if it melds better then...

I did try a lot. did phase reversal too. but not of great help. Did you see the GD plot? do you feel its a problem?

 

[Baldin]

Hi Acuosticraft

8" in a seled box trying to reach f3 at 20 Hz will not work well, I think.
I have a 12" with 300 W class-d with a LT doing f3 at 25 Hz, and I think it lacks output.

Have you considered AceBass?
There you can have the box size of a sealed LT but the output of a larger vented system.

I'm considering turning my 12" into a AceBass .... when I find the time

 

[Aucosticraft]

Baldin,

I was not aware of AceBass. What is it? any literature I get to read on this? I googled but no strong article "theory of operation " came up.

 

[Calvin]

Hi,

I second the recommendation by Sreten of using a peaking HPF instead of Linkwitz, as it performs both functions in one go.

That´s what I also recommended in post #20. But I suggest the usage of a CB instead a BR-system. The high order BR-systems need precise tuning. A bit off of the optimum and the sound is crappy, just loud, one noted bass and terribly boomy. The amplitude response of any BR alignement doesn´t fit the room´s own response which adds considerable roomgain. A CB with its falling response by -12dB/oct is just the counterfit to the rooms own response and design and tuning of a CB is easier. A simple 2nd order HPF is all You need to equalize after Your wish. Level, amplitude response and frequency of the filter may be tunable, which makes such a system alot more flexible too.

jauu
Calvin

 

[Shaun]

Calvin, do you perhaps mean post #38?

LT is intneded to be used with a sealed enclosure, as far as I'm aware. Good idea with the tunable filter.

 

[chris661]

AceBass is, simply, a synthesis of loudspeaker parameters, by changing how the amplifier's output impedance looks to the speaker. You can (without physically altering the driver) give it a lower resonance, higher Qts, and many other things.
Someone once set up a computer program to set them in real-time.
Using such a system, an example was given of a pair of 6.5" midbass drivers hitting silly SPLs (something like 120dB@1m) down to 40Hz.

It's very neat, if you can do it right. You need a dedicated amplifier and a "suitable" speaker for it.
Hopefully, someone'll have a link to the original article.

Chris

 

[bjorno]

ACE Bass

AceBass is, simply, a synthesis of loudspeaker parameters, by changing how the amplifier's output impedance looks to the speaker....Hopefully, someone'll have a link to the original article...Chris

Start here:

http://www.diyaudio.com/forums/subwoofers/104447-ace-bass-amplifier-design.html

This tread ends with presenting Baldin's very promising(AC-stable) ACE Bass clone design that is the best I've seen so far using up to date components.

PS: My old design is an internally DC-stable design but trickier to adjust for good long term stability( <=10 Years: typically needs 8 years re-trimming intervals if used heavily at a daily rate ) that depends both on aging driver parameters and of the component aging/drift of the ACE-Bass amp itself.

b

 

[Baldin]

Thanks bjorno for the kind words
Best source is the AES paper by Karl Erik Stahl, but you'll have to pay 20$ .... 95% the same is the patent: Loudspeaker lower bass response using negative resistance and impedance loading

Also take a look at by blog for further information on calculations sheet and a step by step guide etc: AceBass up and running | Baldin's Blog

Best regards Baldin

 

[Aucosticraft]

Thanks Everybody for briefing me on ACE-BASS. I had googled for it seems to be a bit deep subject. I ll do it later. ofcourse wont be able to understand it without your help. but durrently we r discussing LT,Peaking filter, and ACE-Bass. all three at a time is getting bit heavy for my small brain. So decided to keep ACE-BASS for later.

Sreten, I am trying to work on your advice. I have some old trial enclosure. I would adjust its volume to get the desired one.

BTW, what role does a group delay play? I have noticed that group delay goes very bad when filters are used. can some one throw light on this?