What's up with this room???

**mstailey** · **03-08-08, 07:45 PM**

Hooked up all related REW items incl BFD 1124 and took my first measurement on the sub only. Now, I'm no wiz kid but the end of the sweep does not look good. BTW - I've 2 MK 150THX subs stacked AWAY from the corner, actually mid wall out about 1 foot. Processor is set for THX standards (high pass 12db - low pass 24db).

Is this bass build up? Can this be removed via eq'ing or do I have a ton of work ahead of me in room treatments?

(edit)
I'm using the ECM8000 with the cal file in place.

**brucek** · **03-08-08, 07:57 PM**

Quote:

but the end of the sweep does not look good

Don't exactly know what you're referencing to?

Anyway, you normally take a first measure of the sub only with the mains disconnected, so you can evaluate the sub by itself and its interaction with the room.

Then you can also take a measure of the mains only.

Then take a sub + mains to check interaction between the two at the crossover...

After that, your evaluation will be much easier.

brucek

**mstailey** · **03-08-08, 08:08 PM**

Sorry brucek, what I'm trying to say is I measured the sub only - no speakers hooked up. I'm concerned about the rise between 100hz up to 196hz. REW shows the filters after I perform the process acording to the manual, to pull it down by some -18db at 168 hz. If my pre is set for a low pass of a 24db slope then why do I have to add a filter at that range?

My question is this normal to have to add a filter with this much of a drop? Or do you think I have a room / placement problem?

**brucek** · **03-08-08, 08:51 PM**

Quote:

what I'm trying to say is I measured the sub only - no speakers hooked up

Are you telling me that the graph you show is through a receiver with an 80 crossover set? - no.

BTW, use a vertical scale of 45dB-105dB and a horizontal scale of 15Hz-200Hz standard.

brucek

**mstailey** · **03-08-08, 09:19 PM**

Are you telling me that the graph you show is through a receiver with an 80 crossover set? - no.

Yes.

My setup is:
x-over 80hz
high pass 12db
low pass 24db
No speakers hooked up - subwoofer only

BTW, use a vertical scale of 45dB-105dB and a horizontal scale of 15Hz-200Hz standard.

I knew better on scale, sorry -

**brucek** · **03-08-08, 09:54 PM**

Quote:

My setup is:
x-over 80hz

Something isn't right. If it was me, I'd do an REW measure of my receiver only to check the crossover.

To do this you first do an REW measure of a loopback cable to be sure it returns a flat response. Then include the receiver in that loop, feeding the soundcard line-out to the receivers AUX-in and then the receivers SUB-out to the soundcards line-in. You have to play with the levels a bit, but it's easy to do.

Now the measure had better track that 80Hz target in REW.....

brucek

**mstailey** · **03-08-08, 10:22 PM**

Quote:

brucek wrote:

Something isn't right. If it was me, I'd do an REW measure of my receiver only to check the crossover.

Simple enough.

Thanks brucek.

Mike.

**Wayne A. Pflughaupt** · **03-08-08, 11:11 PM**

I would certainly expect a pair of $1500 subs to perform better than this - below 45 Hz this response curve is not even “equalizable.” Do you have a good corner you could move them to? I.e., one with no doorways or other openings close in either direction.

Regards,
Wayne

**mstailey** · **03-09-08, 12:11 AM**

Quote:

I would certainly expect a pair of $1500 subs to perform better than this - below 45 Hz this response curve is not even “equalizable.” Do you have a good corner you could move them to? I.e., one with no doorways or other openings close in either direction.

Hi Wyane,
Thanks for the reply.

I agree with your assesment but I'm trying to figure why the huge rise in upper low feq hence the position (from my first post) to remove any corner loading. Once I determine the problem I'll properly place the subs.

Mike.

**mstailey** · **03-09-08, 03:13 AM**

brucek,
Thank you so much for pointing me in the right direction. Per your suggestion of measuring feq response at the pre-amp got me looking in the right direction. I'll spare you the details of all the points I measured but when I got to the individual subs - well, a picture is worth a thousand words. Dummy me just took this system out of storage and threw it all together to get the BFD operational. Lesson learned here of 1 thing at a time. Now I'm off to make good with the wife who put up with the tones until 3:00 am....

Wayne,
We'll get'er in the corner asap.

Green = good sub
Red = bad sub

**Malice** · **03-11-08, 02:04 PM**

Your sub is supposed to be able to achieve:
Frequency Response: 20 - 125 Hz ± 3dB

There appear to be a number of "THX" filters and settings, none of which I understand the implications for, however, I do know that the drop off in frequency below 50Hz is not right. My current B&W mains speakers can muster better SPL at those frequencies! Something is still amiss!

**mstailey** · **03-11-08, 02:52 PM**

Hi Malice,
Thanks for responding.

Quote:

Malice wrote:

Your sub is supposed to be able to achieve:
Frequency Response: 20 - 125 Hz ± 3dB

As stated I pulled both subs out of the corner to isolate the upper feq's. I agree and here is what I'm currently working on with just 1 sub now which, is back in the corner. As you will see it is (the sub) doing fine. I turned smoothing on and have played with entering a couple of filters in my first attempt with BFD

Quote:

There appear to be a number of "THX" filters and settings, none of which I understand the implications for, however, I do know that the drop off in frequency below 50Hz is not right. My current B&W mains speakers can muster better SPL at those frequencies! Something is still amiss!

Nothing magical about the THX settings. Simply 80hz crossover with high/low pass slopes of 12db and 24db respective.

Mike.

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