PDA

View Full Version : BFD just got easier.



bikeman
04-14-2005, 01:44 PM
I haven't tried it yet. Will the first person who does report back?

http://homepage.ntlworld.com/john.mulcahy/roomeq/index.html

Have fun,
David

BradJudy
04-14-2005, 01:57 PM
Cool, I'll be checking it out as soon as I can.

sensibull
04-14-2005, 01:58 PM
Funny, I just posted that link not 5 min. ago in the "My BFD Experience" thread. I'll definitely be giving this app a spin once I get everything set up. Just hoping my soundcard will be up to snuff...

curtis
04-14-2005, 02:17 PM
I will give it a try at the end of next week when I have time for more measuring.

BradJudy
04-14-2005, 07:48 PM
Testing it now. It's doing a painfully slow 20-200Hz sweep. So far it seems pretty good and includes a lookback function like ETF. Unfortunately, my native notebook soundcard only has a mic in and not a stereo line in. I'm testing with my external card and mic right now. Will report back graph comparison to my previous findings.

BradJudy
04-14-2005, 08:19 PM
I'm done playing for this evening. It seems to work as advertised, but the 20-200Hz sweeps went in 1Hz increments and took 10min!! Talk about a painfully slow sweep.

The resulting graph looks very similar to my ETF one, except the 20-40Hz hump was disproportionally high. Both the RS meter and my ETF measurements (with the same equipment) showed those to peak around 20db above normal whereas this app showed them with a 30db peak. This confuses me since the rest of the measurements seemed to be on track.

My battery is dead and I'm going to chill for the rest of the night, so that's it for now. This definitely has a lot of potential.

sensibull
04-15-2005, 05:22 AM
Brad,

Can you clarify for me how you are sending the signal from your soundcard to your AVR/pre-amp? Are you simply connecting to the analog LFE (.1) input, or is your AVR/pre-amp capable of routing incoming signals to different speakers?

The reason I ask is that I am hoping to test my response: 1) before any changes, 2)with BFD filters in place, and 3)after the HK performs its EQ.

If I have to use the LFE analog input, I won't be able to test #3 (at least not with Room EQ Wizard) because the 635 will not do EQ on the 7.1 analog inputs, and I'm uncleear how to route an incoming signal (on say, the "CD" input) to just the sub.

Hope that made sense...

BradJudy
04-15-2005, 06:00 AM
I am just sending the input into the right channel of one of the analog inputs (specifically the one on the front panel). The AVR does its bass management (I have it set for an 80Hz crossover), but it does not have any EQ capabilities.

sensibull
04-15-2005, 07:17 AM
Ok, thanks. Maybe I'm just overthinking things (as usual), but I'm getting hung up on the following in the Room EQ Wizard's config requirements:

"The input used on your AV processor must be one that the processor can route to any speaker output....If the processor does not have such a signal routing facility it may have 5.1 or 7.1 analog inputs that can be used."

Does the software control the routing (i.e. send a standard analog signal to the sub only), or must the AVR have this ability?

BradJudy
04-15-2005, 08:03 AM
The software can't control the AVR at all. I don't know anything about the EQ function on your AVR, but the tests I did don't require any special 'routing' capabilities. I just set the receiver to have the sub as being 'on' with a crossover of 80Hz. It then sends signals below 80Hz (really above that too, depending ont he crossover slope) to the sub instead of the main speakers.

sensibull
04-15-2005, 08:29 AM
OK, well, if you'll pardon one last question, that's where my confusion lies. In your setup, when the sweep reaches the crossover range and above, doesn't the tone then begin to come out of your other speakers as well, and doesn't this compromise the test? Or do you just disconnect them during the sweep?

Mag_Neato
04-15-2005, 08:54 AM
Since you are primarily interested in sub equalization, you could run the sub without any sattelites.

I have my sub crossed at 80hz through the receiver. The subs crossover is set to it's 150hz max. setting to get it out of the way. I ran a series of test tones from 18 to 150hz with the main speakers unplugged.

Near the crossover point, 84hz, I had 85.5db. At 150hz I had 54.5db......down 31db.

This is a good way to evaluate the sub's in room response and see what needs attention, since the EQ'ing will affect the sub's response first.

A full system response can then be used to determine proper phase and crossover settings.

My sub drops like a rock below 30hz, so I'm thinking of a cut from 30 on up to bring the other frequencies down closer to the sub-30 response. I have enough gain on the sub volume to compensate and bring things back up.

sensibull
04-15-2005, 09:28 AM
Thanks, Mag.. "with the main speakers unplugged" is the info I was looking for. Hadn't seen (or hadn't registered) that step in any of the bass eq threads. Common sense, I know, but (despite my rather arbitrary user name -- I just liked the pun) sometimes I seem to be in short supply of it...

BradJudy
04-15-2005, 12:29 PM
No, I don't do it with the mains unplugged. That actually defeats the purpose. The purpose is to have the complete response be even, which might require some tweaking in the crossover range. Unless you do it with the mains connected, you won't know what the summed sound is like (you will also miss destructive interference if the phase is not configured correctly). I do all of these tests with my mains on for this reason.

DavidD
04-15-2005, 12:48 PM
No, I don't do it with the mains unplugged. That actually defeats the purpose. The purpose is to have the complete response be even, which might require some tweaking in the crossover range. Unless you do it with the mains connected, you won't know what the summed sound is like (you will also miss destructive interference if the phase is not configured correctly). I do all of these tests with my mains on for this reason.

Glad to see you post this. It seems that generally people test with the sub only. Assuming your signal is being bass managed, the only way to get a true picture of the final response is to measure with the mains on. If you mesure only the sub, you can get peaks caused by the output contributions from the mains. The phase issue is also a very good point.

bikeman
04-15-2005, 01:09 PM
What has worked best for me after much experimenting is to EQ the sub only and then run a test with the mains connected. I got my best results with the BFD this way. YMMV.

David

Nicholas Mosher
04-15-2005, 01:12 PM
I just use my SPL meter, a pad of paper, and a pencil... :D

Oh, and I too run my tones with the main five channels on. Not doing so will hurt you in the 60-120Hz range as the sub's output (in my case) needs to be cut at a few points in this range where it's supported by the main channels.

Mag_Neato
04-15-2005, 01:58 PM
When I asked for Dave F.'s advice, he suggested doing it first with sub only, than full system for phase & crossover tweaking.

BradJudy
04-15-2005, 03:09 PM
Apparently this app defaults to a C-weighting correction which I did not see and which accounts for the exaggerated hump. I will try measuring again this weekend, but I expect fixing this should put the measurement in-line with my ETF one.

BTW: If you read the AVS thread, the author posts there. Apparently he used to work for TAG.

Abhi
04-15-2005, 03:10 PM
No, I don't do it with the mains unplugged. That actually defeats the purpose. The purpose is to have the complete response be even, which might require some tweaking in the crossover range. Unless you do it with the mains connected, you won't know what the summed sound is like (you will also miss destructive interference if the phase is not configured correctly). I do all of these tests with my mains on for this reason.
BradJudy,
Since you are connecting ONLY the right channel input, How do you measure the response near crossover point?
Will these 2 cases yield different results?:
1. Use a splitter cable and feed both left and right channels of the AVR with the signal from the PC's right LINE out.
2. Connect the PC's LINE out (right) directly to the AVR's right and leave the left channel alone

BradJudy
04-15-2005, 03:36 PM
Yes, they do give different results. I should split the signal and send it to both, but I need to pick up a splitter which I haven't done yet.