Help with WinISD please

robbie130280

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Hi

After being left disappointed by my svs pc13 ultra I'm going infinite baffle. I have a pair of FI IB3 15 drivers and am about to order the amp: Extreme 1000 I know the site says you can only pre order but bk have told me they can have one shipped in a couple of days!!!! There's just one thing, they've put a HP filter at 15 hz/ 24 db but say it can be moved within reason. I have modeled the system on winisd but I get the best curve for Xmas with 1000 watts and a 9hz/24db filter in place. This is the first time I've done anything like this and only have my own research to go off so a second opinion would be most reassuring. Also would I be right in thinking that a 24 db filter is fourth order?

Here's the driver info: Two 15" drivers each with a single 2 ohm voice coil that will be wired in series for a 4 ohm load

Fs: 22.7 Hz

Re: 1.5 Ohms/coil

Qms: 4.30

Qes: .74

Qts: .63

Mms: 247g

Sd: 810cm^2

Vas: 183.3 l

Spl: 86.4dB 1W/1m

Bl: 8.43 N/A

Xmax: 30mm

Rms: 550W @ 20Hz

Any help will be much appreciated.

Thanks.

Rob
 
Ah yes, it should be moved, I didn't spot that sub forum my apologies but thank you for the confirmation on the filter. The room is only 28m cubed so those two drivers should be enough, I hope
 
Ah yes, it should be moved, I didn't spot that sub forum my apologies but thank you for the confirmation on the filter. The room is only 28m cubed so those two drivers should be enough, I hope
how big is the space used by the IB?

as far as I can see, you cross xmax around ~21Hz so a high order filter at that sort of frequency will see leave you way past xmax between ~10-20Hz. A first order HPF at 11Hz keeps it under control though and only costs ~1dB at 20Hz (i.e. negligible).

Which EQ device are you using that is going to let you set such a low filter btw? or are you going to roll your own electrical filter? tbh I'd say you're better off with an inuke anyway, cheaper & with a more powerful/flexible DSP.
 
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how big is the space used by the IB?

There's a 2 foot crawl space that runs under the entire house. Its more than big enough :)

Which EQ device are you using that is going to let you set such a low filter btw?

The filter is being added by the manufacturer before they send it to me. The one they use looks to be a fourth order and there doesn't seem to be an option to remove it. So I really need to get this right.

as far as I can see, you cross xmax around ~21Hz so a high order filter at that sort of frequency will see leave you way past xmax between ~10-20Hz. A first order HPF at 11Hz keeps it under control though and only costs ~1dB at 20Hz (i.e. negligible).

I must have entered something wrong into winisd because it doesn't even get close to Xmas on my chart with 1st order set at 11hz. Here's what I get:



but with a 4th order set to 9hz I get this:



And this without a filter:



tbh I'd say you're better off with an inuke anyway, cheaper & with a more powerful/flexible DSP.

I've looked at all kind of amps. With this being a small room there isn't really anywhere I can hide a big pro amp. I don't want it on display as it wont match the rest of my gear. I plan to build this plate amp into the back of a piece of furniture where it will be nicely hidden away. I could save my self a lot of hassle if I went pro but it needs to look nice as well as sound amazing.
 
The filter is being added by the manufacturer before they send it to me. The one they use looks to be a fourth order and there doesn't seem to be an option to remove it. So I really need to get this right.
I think you're asking for trouble tbh, the model is one thing but actual real world performance in room is another. The model should be pretty accurate but it is not going to be absolutely bang on. There are other options though (e.g. a minidsp).

I must have entered something wrong into winisd because it doesn't even get close to Xmas on my chart with 1st order set at 11hz.
can you show your model? I entered the params you gave into winisd & then stuck in some large number for enclosure size (8000L) to turn it into an IB. It went past xmax at ~22Hz even at 1000L though (which would make a small IB I think).
 
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I spotted what I've done wrong. It seems my high school maths had eluded me when entering the box size. I was lazy and just entered 999 liters thinking it was a lot of volume not realizing it was only one square meter haha I've worked out the space and its close to 40000 liters and now I get cone exursion graphs like you describe. Whats strange though is that my model is now down by 2 db from the start:



I decided to phone the amp manufacturer today and they were willing to remove the high pass filter for me!! So I placed an order. Ill be using audessey xt32 for most of my dsp but ill still want a proper filter in place to protect my new gear. That minidsp is new to me and looks brilliant!!

I'm feeling a lot more confident about all this now. Thanks ever so much for your help mattkhan, it's very much appreciated
 

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