Two cylinder sub-woofers in SVS style. - Page 5 - AVS Forum
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Old 05-22-2014, 10:23 AM
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Quote:
Originally Posted by cochinada View Post

Talking about filters, I've been reading the information about the miniDSP and it looks like I'm going to need to buy a plugin. mad.gif

Is this enough for the LT and HP and LP? Or do the LP and HP come with the box and don't need another plugin?

2way Advanced

 

You need a plugin do to anything with minidsp. Fortunately, they're only $10 and work really well. I'm using the 2.1 Advanced, but I'm not exactly sure what the difference is between the 2 and the 2.1 I know for sure you can do everything you want to do with the 2.1 Advanced though. 

 

Once you buy it, you get a link to download the .exe file, so you can install it on multiple computers if you want to.

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Old 05-24-2014, 09:59 AM - Thread Starter
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My miniDSP arrived Yesterday and I'm configuring it.

The LT was easy but it seems that for the high pass filter the minimum frequency is 10Hz! eek.gif I need to define 7Hz. I was not expecting this. What can I do?

Another thing: I connected the miniDSP to my pc via the USB port and was hoping it would get the power through it as well, allowing me to program it but nothing happened. Is this normal? Do I still need to connect it to 12V at the same time?

Linkwitz transform:

f0 = 30.876
Q0 = 0.694
fp = 15
Qp = 0.707

gives the following coefficients:

a0 1
a1 1,997222780521180
a2 -0,997226630491368

b0 1,001524250429360
b1 -1,997216549324100
b2 0,995708611259083
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Old 05-24-2014, 02:05 PM - Thread Starter
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I've been reading some more and I think that a HPF can also be implemented by a biquad filter.

Using the 'All-digital-coefs v1.2.xls' in worksheet HPF:

Fill in parameters:
Freq. 7 Hz
Q 0,707

Fs 48000 Hz


Digital coefficients: supply to the
MiniDSP plugin - advanced biquad
a0 1
a1 1,998703963861390
a2 -0,998704802919371

b0 0,999352191695191
b1 -1,998704383390380
b2 0,999352191695191

Status Stable


w0 0,000916298
alpha 0,000648018
a0 1,000648018
PF


However where do I define the order of the filter? Is this a 2nd order equivalent filter?
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Old 05-27-2014, 10:51 AM
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Quote:
Originally Posted by cochinada View Post

I've been reading some more and I think that a HPF can also be implemented by a biquad filter.

Using the 'All-digital-coefs v1.2.xls' in worksheet HPF:

Fill in parameters:
Freq. 7 Hz
Q 0,707

Fs 48000 Hz


Digital coefficients: supply to the
MiniDSP plugin - advanced biquad
a0 1
a1 1,998703963861390
a2 -0,998704802919371

b0 0,999352191695191
b1 -1,998704383390380
b2 0,999352191695191

Status Stable


w0 0,000916298
alpha 0,000648018
a0 1,000648018
PF


However where do I define the order of the filter? Is this a 2nd order equivalent filter?

 

I was actually just trying to find that. The iNuke dsp can't do filters below 20hz, but someone had figured out how to do it using biquads. 

 

I think that Q has to do with the order of the filter, but I'm not positive. 

 

If that doesn't work, you could just do an 8th order butterworth high pass at 10hz. It won't roll off very much above 10hz because of how steep it is. 

 

Wait, I thought you weren't going to use a high pass. Sorry, it's hard to keep up.

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Old 05-27-2014, 11:09 AM - Thread Starter
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Quote:
Originally Posted by TheGiantPeach View Post

I was actually just trying to find that. The iNuke dsp can't do filters below 20hz, but someone had figured out how to do it using biquads. 

I think that Q has to do with the order of the filter, but I'm not positive. 

If that doesn't work, you could just do an 8th order butterworth high pass at 10hz. It won't roll off very much above 10hz because of how steep it is. 

Wait, I thought you weren't going to use a high pass. Sorry, it's hard to keep up.

Yes, I also think that Q is related with order on that excel sheet but exactly how I don't know.

If I don't use a HP my cone excursion rises above Xmax under 10Hz or so, unless I lower the power.

Green = HP, Blue = No HP

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Old 05-27-2014, 03:04 PM
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Originally Posted by cochinada View Post


Yes, I also think that Q is related with order on that excel sheet but exactly how I don't know.

If I don't use a HP my cone excursion rises above Xmax under 10Hz or so, unless I lower the power.

Green = HP, Blue = No HP

 

Yeah looks like you do need one. Have you tried modelling a 8th order BW high pass at 10hz in winisd to see how much a difference it makes?

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Old 05-27-2014, 04:23 PM
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keep in mind that the typical signal chain has some rolloff in it. unless you measure, you won't know how much.

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Old 05-28-2014, 12:35 AM - Thread Starter
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Quote:
Originally Posted by TheGiantPeach View Post

Yeah looks like you do need one. Have you tried modelling a 8th order BW high pass at 10hz in winisd to see how much a difference it makes?

Here it is. 3 different models, one without filter, the other with 7Hz 2nd order and the last one with a 10Hz 8th order. The Group Delay goes off the roof and the cone excursion is not well taken advantage off in those really low frequencies I think:



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Old 05-28-2014, 12:37 AM - Thread Starter
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keep in mind that the typical signal chain has some rolloff in it. unless you measure, you won't know how much.

Do you mean I will lose SPL in the lower frequencies due to amplifiers and stuff like that? And what about room gain? Which one is most significant after all?
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Old 05-28-2014, 07:04 AM
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Originally Posted by cochinada View Post

Do you mean I will lose SPL in the lower frequencies due to amplifiers and stuff like that? And what about room gain? Which one is most significant after all?

Signal chain roll off is where the components in your setup, such as your receiver, BluRay/CD Player amplifier, ect..., all roll off at a frequency similar to how your subwoofer rolls off. For instance, your receiver may roll off the low frequency signal at say 10hz, or your source may roll off the low frequency signal at 12hz. If you are building your subwoofer setup for maximum extension down as you as possible, then you would be wise to measure & pick your components that do not have an early low frequency signal roll off. So yes, some components will roll off earlier than others. You can do a loop back test through REW to test out your components to see where they roll off.

Of course if you are building a ported sub than this would likely be a non issue. I personally do not like sealed subs as I would much rather get that awesome punch in the low frequencies that comes from having an additional 9db of SPL at the tuning frequency from a ported sub, instead of chasing that last bit of extension that I can't hear anyways..

Room gain is a term for how the room itself can somewhat amplify the low end response and bring the actual response down lower than what you would get in say an outdoor setup.
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Old 05-28-2014, 08:10 AM
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He's got some good points about signal chain roll off. And he feels as I do about the efficiency of ported subs. But you've chosen max extension over max output, and that's just fine. However, even without a high pass filter at all, you're down to 100dB max at 10hz. I know everyone hears ultra low frequencies differently, but 100db that low is (relatively) not that much output. You might not be able to hear or sense it at all. If you want lowest extension possible, it looks like you have to do the biquad filter workaround thing. But you should do some real world tests once you have everything set up to see if you're able to hear anything that low.

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Old 05-28-2014, 08:19 AM
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But you should do some real world tests once you have everything set up to see if you're able to hear anything that low.
Even then you usually don't really know. If you play 10Hz at 100dB with 10% THD, and that's what you can expect driven to xmax, the harmonic content will be running around 120dB. You'll hear the harmonics with ease, but you won't hear the fundamental at all.

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Old 05-28-2014, 08:25 AM
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Even then you usually don't really know. If you play 10Hz at 100dB with 10% THD, and that's what you can expect driven to xmax, the harmonic content will be running around 120dB. You'll hear the harmonics with ease, but you won't hear the fundamental at all.

 

Are you saying that then it wouldn't be worth it at 100dB,? Or are you saying that the audible harmonic content adds positive things to the overall experience?  

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Old 05-28-2014, 09:41 AM
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Are you saying that then it wouldn't be worth it at 100dB,? Or are you saying that the audible harmonic content adds positive things to the overall experience?  
What I'm saying is that the vast majority of those who think that they're hearing content below 15 Hz are really hearing the harmonics of the content below 15Hz. Even if the source is a sine wave generator played through electronics with essentially zero THD the speakers themselves will create the harmonics that are actually heard. In short, chasing below 15Hz with the intent of hearing it isn't productive. If you want to feel what's going on below 15Hz that's another matter entirely.

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Old 05-28-2014, 09:48 AM
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What I'm saying is that the vast majority of those who think that they're hearing content below 15 Hz are really hearing the harmonics of the content below 15Hz. Even if the source is a sine wave generator played through electronics with essentially zero THD the speakers themselves will create the harmonics that are actually heard. In short, chasing below 15Hz with the intent of hearing it isn't productive. If you want to feel what's going on below 15Hz that's another matter entirely.

 

Yeah I've basically come to the same conclusion, that it's not cost/space/power efficient to try to play below 15hz. My next sub build, I'll be shooting for reference levels to 15hz and then tactile transducers for below that. 

 

I'm definitely not denying that there is useful material below 15hz. I would love to experience all those great demo scenes in a room with 16 sealed subs... but it's just not worth it for me to try to pursue that :)

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Old 06-06-2014, 12:56 AM - Thread Starter
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Some pictures of the cabinets being cut by CNC...




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Old 06-06-2014, 06:52 AM
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Wow that is cool! Coming along nicely. How many layers of wood is it going to take? I predict a lot of wood glue and clamps in your future...

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Old 06-06-2014, 07:12 AM - Thread Starter
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biggrin.gif 27 layers of which 26 are 2 inches thick. Fortunately I'm not the one that is going to glue everything...
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Old 06-06-2014, 02:23 PM
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Some pictures of the cabinets being cut by CNC...





eek.gif WOHA!!! Nice!! Are you going to glue those on a sono tube??

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Theater Build and Two Sono Sub Builds Here-
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Old 06-06-2014, 02:29 PM
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He's putting veneer over top so i am guessing no, else i guess he wouldn't need the mdf
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Old 06-06-2014, 02:38 PM - Thread Starter
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Thanks!
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eek.gif WOHA!!! Nice!! Are you going to glue those on a sono tube??

Quote:
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This is what my subwoofer will look like. Instead of varnished baltic birch as planned it will probably be made of MDF and covered with cork panels.

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Old 06-06-2014, 02:41 PM
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I saw this before, but I always just figured you'd be gluing that to a sono tube.

Nice build man..... very nice....

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Old 06-06-2014, 02:45 PM - Thread Starter
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It would certainly be much cheaper but I couldn't find Sonotubes here and to be honest it didn't bother me that much as I prefer to spend a few more bucks and have a stronger cabinet.
And besides this guy has already did some work for me and he's very good. smile.gif

I'll be posting more pictures soon.

Thanks!
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Old 06-08-2014, 02:20 AM - Thread Starter
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All pieces cut waiting for assembling and gluing. On the pile at the left, on top we can see the two cover lids of the cabinets. The other whole pieces are for the bottom layers.
On the right we have all the subsections of the main cylinder.



Some mid layers of the main cylinder being glued...




I hesitated weather or not to use some inside bracing but ultimately decided not to do it as this would require me to increase the height of the cabinets for compensating for the decrease in volume.
But judging from these pictures it looks like the cabinets will be sturdy enough. smile.gif
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Old 06-09-2014, 01:30 PM - Thread Starter
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Each solid steel pillar weights around 7lbs. This will add to the total weight which I estimate at 200lbs per cabinet.

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Old 06-16-2014, 10:56 AM - Thread Starter
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Old 06-16-2014, 02:25 PM
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That's so epic. I'm loving seeing progress. Well done.
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Old 06-17-2014, 02:55 PM - Thread Starter
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Thanks! I'm expecting the cabinets to be ready this week. Then I will be able to work on them at last.
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Old 06-19-2014, 12:41 PM - Thread Starter
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Now that I'm getting very close to the finishing line I have this very stupid question that has been growing inside of me for quite a long time:

How do I know if I'm not applying too much power and putting the driver to jeopardy?
From my modelling in order not to exceed the linear excursion, I can only put out about 60W for System input power but the iNUKE 6000 has a whole lot more than that! I know that equalization will 'magically' spend a lot of juice and for instance the maximum Amplifier Apparent load power (VA) is 955 VA. But is there any safe way to control my Behringer?

Thanks in advance.
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Old 06-26-2014, 08:42 AM - Thread Starter
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Quote:
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Now that I'm getting very close to the finishing line I have this very stupid question that has been growing inside of me for quite a long time:

How do I know if I'm not applying too much power and putting the driver to jeopardy?
From my modelling in order not to exceed the linear excursion, I can only put out about 60W for System input power but the iNUKE 6000 has a whole lot more than that! I know that equalization will 'magically' spend a lot of juice and for instance the maximum Amplifier Apparent load power (VA) is 955 VA. But is there any safe way to control my Behringer?

Thanks in advance.
Can anyone please help?
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