Question about partial correction.

[Trdat]

I read the help file and for the partial correction it states no correction above 15000 and 3000 respectively, so I am preusming the number entered stops any coorection above that point. But what about if I want no correction below a certain frequency?

 

[hulkss]

I do not believe there is any way to do that other than no correction at all (you can still have crossover filters). What are you trying to do?

 

[juicehifi]

Audiolense can’t do that. Why would you it?

 

[Trdat]

Well, my SVS SB1000 subwoofer is quite a low end boombox type sub(I was tricked with SVS marketing) when I add a correction the bass gets significantly worse. I blamed Audiolense at first, then when adding correction to a normal sub I found regardless of the roll off you essentially get "how you correct it" or the bass extension or time domian correction you play with. The results are great, time alignemnt is superb but on the SVS it renders it significantly worse.

With the SVS sub no matter how you roll it off even a winkle of a correction renders the sub like boombox. Now, I am hazarding a guess that the plate amp already has some DSP which bumps up the frequency towards the lower end and artificallly attempting to flatten that perhaps causes it to get even boomier, I dont know. I am not an expert but there must be a reason why this happens. I have had some experts on forums swear that a sub regardless of size with the same roll off is hard to distinguish from one another of course if parameters are similar, and I do agree transients are better with a natural sealed roll off compared to when adding a correction but again this is specualtive at best. My point is why does the SVS get worse when giving it a full sealed type roll off and riding it with its lowest extension? In theory it should get a little more transient, unless the thoery is totally off.

Anyway I digress. For some reason the SVS sub unfotunately can't get better with correction it actually gets significatnly worse so I would like to leave the sub and correct what is above my sub crossover point.

 

[juicehifi]

I am having trouble believing that this sub is uncorrectable.

A correction simply modifies the input signal. Some frequencies are amplified, some are attenuated and some are shifted in time. Music itself has a lot more of the same. Frequencies that come and go ad various strengths etc. So if your sub responds reasonably well to a music signal, it should respond reasonably well to a corrected signal.

Trdat, I can take a look at your measurement, regardless of whether I have done so in the past or not.

 

[Trdat]

I am having trouble believing that this sub is uncorrectable.

A correction simply modifies the input signal. Some frequencies are amplified, some are attenuated and some are shifted in time. Music itself has a lot more of the same. Frequencies that come and go ad various strengths etc. So if your sub responds reasonably well to a music signal, it should respond reasonably well to a corrected signal.

Trdat, I can take a look at your measurement, regardless of whether I have done so in the past or not.

Well, no it doesn't respond properly it is very boomy and nothing is really helping it. In saying that your comment has motivated me to keep trying. I need to keep playing with it. I will experiment a little more and see if its just the transients I am displeased with and perhaps with music not needing bass with no overhang I might be able to it get to respond better. Nothing is wrong per se, its just the limitation of the sub woofer. If I feel, I need you to have a look I will get in touch appreciate it.

 

[juicehifi]

Don't hesitate to reach out if you don't get a good result. I really want this to work for you.

 

[Omid]

I would suggest doing an REW measurement (8 repeats of 4m length) from 10 to 200Hz on your sub (no dsp). Aim for a volume that yields ~85db loudness. and then look at the distortion figures. If you have very high distortion (>20% say) throughout the spectrum, I doubt anything can be done. Also if you have a DAC that has a trim on the output make sure to adjust it down, so you don't exceed your sub's input sensitivity. For example my MOTU DAC puts out up to 7.5 V, whereas my sub's input shouldn't exceed 2.5 v.

 

[Trdat]

Don't hesitate to reach out if you don't get a good result. I really want this to work for you.

Don't hesitate to reach out if you don't get a good result. I really want this to work for you.

Hello Bernt,

So I experimented with different corrections on this particular sub(that gets boomy)and one without true time domain correction and the sub woofer still gets very boomy. After heaps of experimentation the best performance of the sub is with no correction although there was times with huge roll offs that the sub did okay. Any ideas on what could be creating group delay if that is the problem at hand?

I have experimented with my better subs and whatever I throw at it, the bass is superb, clean and transient as possible.

Even if you have an idea of what I can try just to narrow it down before I send you the file to look at. If I can understand better what might be happening I am sure it will help you find what is going on. The general correction is awesome but the subs get boomy.

Maybe a target file that resemebles a closed off to see if it responds well?

i'll be honest, when using equalizer APO playing around with the frequency curve down low the sub responds well.

 

[Trdat]

I would suggest doing an REW measurement (8 repeats of 4m length) from 10 to 200Hz on your sub (no dsp). Aim for a volume that yields ~85db loudness. and then look at the distortion figures. If you have very high distortion (>20% say) throughout the spectrum, I doubt anything can be done. Also if you have a DAC that has a trim on the output make sure to adjust it down, so you don't exceed your sub's input sensitivity. For example my MOTU DAC puts out up to 7.5 V, whereas my sub's input shouldn't exceed 2.5 v.

I am still learning to read the distortion graphs on REW and from what I understand on dbfs the low frequencies reach -80 which is nowhere near 20% right?

And yes I am aware of the input Vrms and it should be okay, thanks for the idea though.

 

[juicehifi]

Hello Bernt,

So I experimented with different corrections on this particular sub(that gets boomy)and one without true time domain correction and the sub woofer still gets very boomy. After heaps of experimentation the best performance of the sub is with no correction although there was times with huge roll offs that the sub did okay. Any ideas on what could be creating group delay if that is the problem at hand?

I have experimented with my better subs and whatever I throw at it, the bass is superb, clean and transient as possible.

Even if you have an idea of what I can try just to narrow it down before I send you the file to look at. If I can understand better what might be happening I am sure it will help you find what is going on. The general correction is awesome but the subs get boomy.

Maybe a target file that resemebles a closed off to see if it responds well?

i'll be honest, when using equalizer APO playing around with the frequency curve down low the sub responds well.

It is hard to tell what's going on without doing a proper validation of your measurement and examining how you make the correction. What you describe sounds like something does not work as it should. First suspect is (as always) measurement flaws.