Fi IB3-18 x 8 and SEOS pure 10 kits! - Page 36 - AVS Forum
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post #1051 of 1075 Old 08-04-2014, 07:29 AM - Thread Starter
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OK, so I ran through some of my movies last night and I noticed some extra low end but the levels seemed lower or equal to than what I had before overall. So I started to investigate and remembered what LTD told me a while ago. My sub system is massive and my room is not that big in comparison so if I add a port which side of the wall will be the enclosure? The IB shoots in both directions and I figured out why my measurements are just like my sealed. It is because my tune did not come out to be 7-8hz like I wanted, it came out to be 3.5hz! This seems awesome BUT my signal chain rolls off starting at 5hz so it ends up being just like the sealed in spl. I started modeling the ported IB with 1460 cubes as the enclosure size. So for me to have a 6.5 hz tune I need to cut the ports down to 1 inch! I knew something was wrong. So I have to cut the ports to 1 inch, 1 INCH! A one inch port will give me 32 SI's at 5hz, 96 SI's at 6hz, and 28 SI's at 10hz. Back to work again. Anyways, if I had a signal chain strong to 3hz this thing would be a monster down low.
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post #1052 of 1075 Old 08-04-2014, 10:20 AM
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So what exactly are you going to do? Get rid of the 12" ports for 1" ports?

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post #1053 of 1075 Old 08-04-2014, 10:24 AM - Thread Starter
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Not 1 inch round, 1 inch long 12 inch round ports. I already modeled and what I need is to cut my existing 24 inch ports in half and then have 4 12 inch round, 12 inch long ports and this gets me a 6.5 hz tune with hardly any port velocity. Better than what I have now except there is hardly any signal where the ports are so I would never know!
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post #1054 of 1075 Old 08-04-2014, 10:31 AM
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Quote:
Originally Posted by MKtheater View Post
OK, so I ran through some of my movies last night and I noticed some extra low end but the levels seemed lower or equal to than what I had before overall. So I started to investigate and remembered what LTD told me a while ago. My sub system is massive and my room is not that big in comparison so if I add a port which side of the wall will be the enclosure? The IB shoots in both directions and I figured out why my measurements are just like my sealed. It is because my tune did not come out to be 7-8hz like I wanted, it came out to be 3.5hz! This seems awesome BUT my signal chain rolls off starting at 5hz so it ends up being just like the sealed in spl. I started modeling the ported IB with 1460 cubes as the enclosure size. So for me to have a 6.5 hz tune I need to cut the ports down to 1 inch! I knew something was wrong. So I have to cut the ports to 1 inch, 1 INCH! A one inch port will give me 32 SI's at 5hz, 96 SI's at 6hz, and 28 SI's at 10hz. Back to work again. Anyways, if I had a signal chain strong to 3hz this thing would be a monster down low.

Lol yeah, James. You don't want it tuned that low. All you'll get is a sealed-like response but with all the nasties a resonant system will introduce. In otherwords, a downgrade from what you had.

So a simple chop of them tubes and you'll be in SPL land.

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post #1055 of 1075 Old 08-04-2014, 10:34 AM - Thread Starter
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Yup, I am making 4 12 inch by 12 inch ports and it will be a monster I expect.
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post #1056 of 1075 Old 08-04-2014, 10:47 AM
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96 SI's at 6 hz...

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post #1057 of 1075 Old 08-08-2014, 09:12 AM - Thread Starter
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I just ordered 4 SI 18HT's to go into the rear boxes, should add 16 SI's at 10hz! For about $100 more it should add 2 dBs from my single IB318. Anyways, it will give me a chance to hear the SI's for the first time.


BTW, I am taking out the ports and just leaving the opening without the ports. If the sims are correct this will give me either a 6.88hz tune or 14hz tune, I will experiment and get this right. The rear subs will be double 18's tuned to 11hz.
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post #1058 of 1075 Old 08-08-2014, 10:33 AM
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Aawwwwww s**t!!!!

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post #1059 of 1075 Old 08-08-2014, 03:58 PM
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Quote:
Originally Posted by Scott Simonian View Post
Aawwwwww s**t!!!! my pants

LOL....


haha Sorry Scott I had too....lol

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post #1060 of 1075 Old 08-08-2014, 04:22 PM
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Hahaha! I set myself up for that one.

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post #1061 of 1075 Old 08-08-2014, 04:25 PM
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haha I was almost in tears laughing when I posted that, my wife was looking at me like I'm an idiot!..lol


I often get that look from her though.

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post #1062 of 1075 Old 08-08-2014, 05:29 PM - Thread Starter
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Women are universal!

The sims are showing 112 dBs at 10hz for each sub so I will have 118 dBs from them and 123 dBs from the front wall, then add in my 22 dBs of room gain at 10hz and I should be OK for a while.
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post #1063 of 1075 Old 08-12-2014, 08:45 AM - Thread Starter
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I don't know what is going on but I need advise!


Here are the raw sealed and then ported responses. WTF.


Sealed





Ported





I EQ'd the ported response to 7hz and the bottom sweep is the result, I then turned it up.





The Nano AVR has a new bass management dsp and REW now added the nanoAVR to the EQ portion and here is my center channel at 20 dB below reference.


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post #1064 of 1075 Old 08-12-2014, 12:57 PM
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How many boosts or cuts are you putting on the ported method?

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post #1065 of 1075 Old 08-12-2014, 01:43 PM - Thread Starter
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All cuts but the NanoAVR does it all, 9 filters in all.
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post #1066 of 1075 Old 08-12-2014, 01:52 PM - Thread Starter
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BTW, I tried running some scenes with that response(EQ'd) and the bass is back big time! The 24 inch long ports were choking the system in comparison with the same response. The bass is massive again. I am running two 12 inch holes in the 1.5 inch thick plywood. I am still confused.
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post #1067 of 1075 Old 08-12-2014, 02:32 PM
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To compare sealed and ported frequency response you could measure first ported, assuming that's what you have now, and then measure sealed, with exactly same mic pos and eq and level, to get comparable measurements.

To make it sealed you just stuff the ports, use towels or something like that, foam will not do as it will leak lf.
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post #1068 of 1075 Old 08-12-2014, 02:34 PM - Thread Starter
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I will do that tonight and check.
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post #1069 of 1075 Old 08-12-2014, 02:35 PM
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Looks like you will need quite large towels..
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post #1070 of 1075 Old 08-12-2014, 02:35 PM - Thread Starter
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Maybe I am leaking LF from the get go? Maybe my mains are leaky and causing the wall to be ported all along? I insulated all around the mains though.
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post #1071 of 1075 Old 08-12-2014, 02:37 PM - Thread Starter
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I will just screw in some ply to cover the holes.
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post #1072 of 1075 Old 08-12-2014, 02:42 PM
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That is actually a very good possibility, the chamber needs to be perfectly sealed - part from the ports - or else it will not work as predicted.
A way to measure that could be to measure the port near-field, i.e. mic in the port, to see where the tuning is.
It should not be too far from what (I assume) you have simulated, you can also see this by measuring the drivers near-field, the response will have a noticeable dip at the tuning.
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post #1073 of 1075 Old 08-12-2014, 02:49 PM
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Quote:
Originally Posted by MKtheater View Post
... I insulated all around the mains though.
If there is a large gap just filled with insulation this could act like a damped port.

If you seal the (intended) ports, you can measure the drivers near-field to see if they have a tendency to dip down at some frequency, which would indicate that the chamber is not behaving like a completely sealed enclosure.
This may be hard to verify reliably, because the damping (insulation?) will reduce the ported effect, and there are also problems with measurement accuracy at these very low frequencies.

Ideally, when sealed, you should measure a smooth roll-off near-field.
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post #1074 of 1075 Old 08-12-2014, 03:20 PM - Thread Starter
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Here are some old attempts.


Quote:Originally Posted by exojam

MK,

When you do the close mic with the bassis engaged I would have everything set to zero.


What do you mean? On the Bassis?

I think what is happening is that the mic is not tracking the low end boost correctly under 10hz. Here is why. This is close mic vs Bassis. I used an Fs 38 Hz and a Qs of .3 since that is the response is matches. No boost and Qb set to .7



Now here they are compared to LP with nothing changed except added cal files(my cal files look just like C-weighting). The volume was not touched. According to the close mics I am gaining 3 dBs at 20hz, 6 dBs at 10hz, and 12 dBs at 4hz. The LP is not showing that and I bet I am feeling that! I will try another computer tomorrow and also compare the behringer to the RS meter. They are closer than you think.



Finally running graphs with the same volume.

Also EQ off on the sony.

How does one loopback using HDMI since it is the only connection to the AVR? I will do it.
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post #1075 of 1075 Old 08-13-2014, 11:49 AM - Thread Starter
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My 4 SI 18's came in today waiting for me Friday when I get back.
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