Home Theater Forum and Systems banner

1 - 16 of 16 Posts

·
Registered
Joined
·
56 Posts
Discussion Starter #1
Well my first attempt at a sub build and I'm pretty content with it. I wasn't sure at first since the response was all over the place. Finally figured out REW and my Rane PE17 and it sounds a lot better now. Only thing I'm curious about is most response curves I've seen posted fall off as they approach the crossover frequency. Mine track straight across. Why is that?

Here's the sub.



Response curve before EQ



Response curve after

 

·
Elite Shackster
Joined
·
1,506 Posts
Welcome to the shack Jailer!

Looks like a nice build and a nice job on the eq. What is the sub tuned to? When you run REW are you running it along with your mains at the same time or just the sub? If it's just the sub are you running REW through your receiver or straight into the 2500? Also, did you download and use the spl meter calibration files? From the looks of the graphs there is no sound card or spl meter calibration files active, which could explain the rapid rise in response to 15hz. I know that's a lot of questions, but hopefully we can answer your question with them!
 

·
Registered
Joined
·
56 Posts
Discussion Starter #3
Thanks for the kind words. This is my first build. I'm pretty happy with it so far now that I've got it EQ'd.


What is the sub tuned to?
24hz

When you run REW are you running it along with your mains at the same time or just the sub? If it's just the sub are you running REW through your receiver or straight into the 2500?
Just the sub and run directly into the 2500

Also, did you download and use the spl meter calibration files?
I downloaded the SPL files from here

From the looks of the graphs there is no sound card or spl meter calibration files active, which could explain the rapid rise in response to 15hz.
The sound card and SPL calibration files were active when the readings were taken. If your referring to the checkboxes not being checked in the pictures, I just unticked them to take the screenshots.

I have the high pass filter set at 20hz so I don't know why it shows the response rising below that.
 

·
Elite Shackster
Joined
·
1,506 Posts
Just the sub and run directly into the 2500.
Ah, that's probably why you have a straight line going to 200hz. The low pass filter in your receiver should take care of this. You may want to calibrate by running REW through your receiver and it's bass management to see what is really happening when you are listening.

The dip in your first graph just above 20hz looks like your 24 hz tune to me. The rising response below that is strange. It may be the noise floor creeping up due to the calibration files but maybe one of our REW experts can chime in on this. Anyway could you post a graph with those boxes checked so we can see what they look like? Also, are you applying any eq in the 20hz area?
 

·
Registered
Joined
·
56 Posts
Discussion Starter #5 (Edited)
No EQ applied at 20Hz. I've got 2 filters applied. One at 50Hz and the other at 80Hz.

I tell ya this thing sounds fantastic now compared to when I started. Especially since I disabled the high pass filter that was set at 50Hz on the EP2500. :explode:

Here's a shot of the graph with the check boxes ticked.

 

·
Registered
Joined
·
56 Posts
Discussion Starter #6
Well I'm bored and I can't seem to figure out how to PM yet so I'll post up some more pictures of my build. :bigsmile:

The enclosure is 6 cubic feet internal volume tuned to 24 Hz. The port is a slot port 22 1/2 inched wide 2 inches tall and 28 1/2 inches long. Looking back I should have made some sort of brace that runs front to back. The entire back wall isn't tied into anything. Oh well.

Rigging up our home made circle cutter. Worked great.







Main part of the cabinet assembled.



Ventilating the brace



Port installed



Brace installed



Complete

 

·
Registered
Joined
·
2,431 Posts
I would agree that something isn't right with your measurements. The low end should not look like that with a sub tuned to 24hz.:scratchhead:
 

·
Registered
Joined
·
56 Posts
Discussion Starter #8
I would agree that something isn't right with your measurements. The low end should not look like that with a sub tuned to 24hz.:scratchhead:
I know it should fall right off after the high pass filter at 20Hz. I don't know why it doesn't but every single measurement I've taken looks like that on the low end.

I used the on board audio on my motherboard to take the measurments. Maybe I'll try taking measurements through the Audigy 2 ZS or use one of my other computers to see if that makes a difference. :huh:
 

·
Elite Shackster
Joined
·
1,506 Posts
I'm thinking that the rising low end conicides with the calibration file pretty smoothly and that it is the noise floor creeping up. Try taking measurements at a high level like 85 or 90db and see if that helps.

Cool build pics, glad to hear it is sounding good. In the end that's all that matters!
 

·
Registered
Joined
·
56 Posts
Discussion Starter #10
Well I re took the measurements, this time through my Onkyo 805. The only problem is there is no way to run the analog signal to the sub using the AVR signal proccessing and crossover. The only way I could get it to work is to enable double bass in stereo mode. So still no measurements with the crossover active.

Anyway here are the results once again. First with the EQ bypassed and second with the EQ active. The results speak for themselves.



 

·
Registered
Joined
·
292 Posts
You didn't just EQ those huge room induced nulls/dips/caverns did you? I would suggest, if you did, you try some room/placement treatments before adding 18+ dB of boost to them.
 

·
Registered
Joined
·
56 Posts
Discussion Starter #12
You didn't just EQ those huge room induced nulls/dips/caverns did you? I would suggest, if you did, you try some room/placement treatments before adding 18+ dB of boost to them.
I didn't add +18 of boost. I took away -15 db from the peaks. Trust me the sub response sounds as even as that graph is. It's crossed over at 80Hz so ignore everything above that and everything below 20Hz.

Room treatments are out of the question. I had a hard enough time selling a big huge sub like this to the wife.
 

·
Elite Shackster
Joined
·
1,506 Posts
How are the setting on your Onkyo? Are your speakers set to small? If they are then the receiver should automatically redirect the bass to the sub through the crossover. Is Audessey engaged in the second graph? Looks like a great response but one that would require many filters...
 

·
Registered
Joined
·
56 Posts
Discussion Starter #14
How are the setting on your Onkyo? Are your speakers set to small? If they are then the receiver should automatically redirect the bass to the sub through the crossover. Is Audessey engaged in the second graph? Looks like a great response but one that would require many filters...
Auddessey was disabled. I forgot to enable it to take a comparison reading.

All speakers are set to full range. The 2 filters that are engaged at 50Hz and 80 Hz are set to 3 octaves on the bandwidth dial. That's what smoothed it out the most. I tried narrowing the bandwidth and it didn't touch the nulls at all.
 

·
Registered
Joined
·
56 Posts
Discussion Starter #15
First off big thanks for everyone's advice about taking measurements. Because of the responses I received from the graphs I posted, I couldn't just leave things alone and had to keep trying to tweak this more.

I finally got things working with my Audigy2 ZS and was ables to take some measurements that look like they are accurate this time. The results were quite a bit different from before.

This is the response curve with the EQ bypassed. There was a huge dip around 30Hz that I could not get rid of no matter what I did or how I positioned the sub so I decided to move it.



This is the repsponse after I moved to the other side of my mains. Still not great but the big depression was gone.



And here it is after many measurements and EQ adjustments. There is still a huge depression at 90Hz but the sub is crossed over at 80 so it should be OK.



Does that look a little better or should I still try to do something about that dip at 90Hz?
 

·
Registered
Joined
·
2,431 Posts
That does look better and more realistic. I'm not normally big on EQ unless it's absolutely needed. I think you could go ahead and take a measurement with your mains involved and see what that does in the crossover region. It may help out. Moving it a foot or 2 may help also. If you have to boost you can, but I don't think that you'll want to try to get it all the way back up to the target line. I wouldn't go much more than 8db. The reason for this is that your crossover should already have rolled of that area by about that much, so if you boost the signal in this area by about that amount you end up with the same power requirements on your amp and driver as if you were running a higher crossover. This should be pretty safe.
 
1 - 16 of 16 Posts
Top