REW Nearfield measurment with sub

[The_Nephilim]

Hey All,

I, have somewhat of a stumper, well for me anyway. I have a Mach 5 IXL 18.4 - 18"Driver in a 285L box ported and is supposed to be tuned @16hz. Now I ran the first MLP Measurement and got a wierd responce. I then tried a nearfield and the responce was almost similar with a wierd null @ 28hz, like that was it's tuning but it is supposed to have a 16hz tuning. Does anyone know what is going on here with this REW Graph:

I will post the pic of the graph and some specs of my setup:





my setup is as follows:

1. Integra 40.3 AVR.
2. iNuke 3000DSP amp
3. Mach 5 IXL 18.4 driver box supposed to be tuned @ 16hz.
4. Mini DSP.
5. U-Mik1

Now I was reading the guides on how to setup REW correctly. I believe it is all setup properly and all but I am not getting why I see that null @ 28hz?? I am pretty sure the crossover on the iNuke was bypassed and on the mini DSP I bypassed it for the test as well.

EDIT: I also wanted to add that I tried generating tones with the generator and it plays those notes and at high db. I just tried a 28hz tone and boy did the house quake.. I am really not understanding why they play fine but when I measure it they look bad?


EDIT: I will add the Original MLP Graph I started with:

 

[sm52]

Try to measure from a different position. 0.5 m to the side. Or 0.5 m further.

 

[Wayne A. Pflughaupt]

The good news is, that’s not a null. Nulls are a function of the room, and are sharp and deep. You can’t get a null with a nearfield measurement.

Aside from that, can’t say why the graphs show a slight depression there, but the fact that a test tone is rattling the room tells me it’s not going to be big deal with program material.

Regards,
Wayne

 

[The_Nephilim]

I did try and move the Mik but got a similar result..

If it is not a null sorry for the wrong terminolgy I am learning but what can I do with it since I was going to EQ it with REW and miniDSP?

 

[Wayne A. Pflughaupt]

Since it's not a null, you should be able to EQ it with the miniDSP. Just don’t be surprised if it doesn’t make an audible improvement, even if the graph looks better. It’s not that big of a problem. I mean, it’s below any meaningful musical content. It’s down in movie “boom country." I don’t expect you’re going to be going, “Oooh, yeah, that 28 Hz made a big difference with that last explosion!”

Regards,
Wayne

 

[The_Nephilim]

Well since that is not a null then it would just be a dip? (trying to get the terminology here) Yes I probally would not even notice it but I am just wondering why the sub seems to go lower then that graph suggests, is it possible I have a setting wrong or similar for it to be so Off?.

I guess I watched too many videos and expected an easy fix lol!! I know the sub is playing down to at least 16Hz as I can play that tone and it will shake the house.. IDK Maybe I expected too much, not sure but this is dissapointing ..

 

[Wayne A. Pflughaupt]

I am just wondering why the sub seems to go lower then that graph suggests,

A graph measured from the MLP would probably answer that.

Regards,
Wayne

 

[The_Nephilim]

OK I have the MLP Graph here it is does this tell us anything more??





I should have posted this first but I did the nearfiled first. but if you need more info Please let me know I can get more pics of my systems config settings and such..

 

[The_Nephilim]

OK I nuked it from orbit and started from scratch. here is my new MLP Graph. it looks a bit better in the lower region and some dips down or are they nulls?

 

[sm52]

I guess the room is to blame.

 

[Wayne A. Pflughaupt]

That’s more like what I’d expect a sub tuned to 16 Hz look like. Unfortunately, the nulls and depressions are too severe to remedy with equalization. It’s probably the result of poor placement in the room. I’d suggest trying a corner that has walls with no openings (windows, doors) in both directions.

Regards,
Wayne

 

[The_Nephilim]

well it is a unfinished basement and the sub is in the left front facing the corner. Should I turn it into the room??

 

[The_Nephilim]

hey good news I moved the sub and set the sub distance up a bit and crossovers here is the responce I know get:

 

[sm52]

I wanted to say about this, but I thought you already tried it.

 

[Wayne A. Pflughaupt]

Looks great!

Regards,
Wayne

 

[The_Nephilim]

Well I toiled around with REW All day today and wiped out all I did. I found out my mistake and tomorrow I will take another crack at it but this time when I do the 2nd tweaks to manually do the in the miniDSP.. I was auto EQ and got a good graph them autoe EQ the EQ'd graph and it never worked now I see why..

I believe I will be able to get back to a good EQ of it.

 

[The_Nephilim]

well I started off the graph looked like this:








I spent some time and got to this point, I still have a dip at 110hz I think that is my crossover. I was told I can adjust the subwoofer distance setting to bring that up a bit like I did last time.. I will work on it further this afternoon:

 

[Wayne A. Pflughaupt]

At this point it would be good to include your main speakers in the measurement, as they’ll probably fill in the 100 Hz depression.

Regards,
Wayne

 

[sm52]

The_Nephilim
to make the comparison correct, do the same smoothing for all the graphs. 1/24 or 1/6 or whatever you think is convenient.

 

[The_Nephilim]

The_Nephilim
to make the comparison correct, do the same smoothing for all the graphs. 1/24 or 1/6 or whatever you think is convenient.

HaHa, I did not even notice that I corrected the images they are now both 1/6th..

I do wonder why know the Bass seems different, is this because before the bass was boomy? I was used to how that sounded it is just like something is missing now??

I hope when I adjusted the distance setting something did not get poofed..!!

 

[The_Nephilim]

Well it appears I shorted the subwoofer out on my Reciever. I have a 7.2 so I tried the other port and it seemed to have worked like it should. I will give it a better test tomorrow so I will need to recalibrate it all and then rerun the sweeps to EQ it out.. Man I thought I fried my driver..

 

[The_Nephilim]

well after thinking I blew my sub it looks good agaqin. so I will wait until tomorrow for more tweak time but I think the signal out on my sub is fried..

 

[The_Nephilim]

here is what I came up with today. I put in a house curve as well. does not look to bad. I also at one pointthought I blew my subwoofer, is there a possiblity I could of partially blew it? I went to read the ohms of the driver and it read 2 ohms, it should be a 4ohm driver??

 

[sm52]

Here they write, your driver is 3.4 Ohm.

Mach 5 IXL 18.4 Box Help?

Hey Everybody, I had built this sub back in 2013, here are the dimensions of the box and it was supposed to be tuned @ 16hz. now when I tested it with my newly acquired U-Mik it appears the boxes tune is 28Hz? The driver is supposed to be a Mach 5 IXL 18.4 Driver. and the box was designed...

www.avsforum.com

Ha. So it was you.

 

[The_Nephilim]

yes, thatwas me I already know the rated ohms I am just wondering if the 2ohm reading was a fault of how I did it or was it supposed to read 3.4ohms? I measured my speakers and they where 7.4ohms?? I am just wondering if I partially baked the driver or was the 2ohm reading ok on a 3.4ohm driver?