REW+BFD with two fullrange speakers no sub

[Wildt]

Hi!

I just bought the BFD and the ECM8000 mic, and is wondering how best to apporach the measurement. I have two fullrange speakers in an asymmetrical room (one speaker is closer to a corner than the other).

Should I calibrate using 1 measurement from the listening position and store the same filter in both L and R banks on the BSD, or measure each speaker individually and store the filter in the relevant channel bank?

/Brian

[brucek]

Should I calibrate using 1 measurement from the listening position and store the same filter in both L and R banks on the BSD, or measure each speaker individually and store the filter in the relevant channel bank?

If you were dealing with two subwoofers, this would be trial and error. Two subs may measure quite different when played in concert than they did when measured individually. You would normally make an attempt at equalizing individually and then make the necessary adjustments when both speakers are played together.

You do realize that trying to apply parametric filters to full range speakers is only recommended with very low Q filters. Trying to remove small peaks and dips is somewhat a waste since the listening position location that they will be effective is extremely small (don't move your head). REW will not recommend filters above 500Hz. Generally room treatment is recommended for the region above subwoofers to about 500Hz. Large bandwidth equalizers or tone controls can help with wide dips in levels at the higher frequencies for full range speakers. The BFD is normally assigned to subwoofers only.

brucek

[Wildt]

Thanks for the quick reply - and yeah, I'm aware that the target area are large dips/peaks in the <200 hz range. I can't see why the low range of two large fullrange speakers would differ from trying to tackle two subs, so I think your argument about how their behavior in concert can differ from their individual ditto applies. I guess the it's the tiresome trial and error method then.

Being a complete noob to the BFD i figured one-way MIDI would suffice, so I only bought one cable. Now I don't know if the configuration via REW isn't working due to the BFD being version 1.03 or the REW not being able communicate properly without two-way MIDI. So - how do I check the firmware version on the BFD?

[huff]

Wildt wrote:

how do I check the firmware version on the BFD?

fully power down the unit, press and hold the Filter Select button and power up

[brucek]

Now I don't know if the configuration via REW isn't working due to the BFD being version 1.03 or the REW not being able communicate properly without two-way MIDI. So - how do I check the firmware version on the BFD?

Power up while holding Filter Select button down and the version will appear in the display as long as you hold the button down.

I can't see why the low range of two large fullrange speakers would differ from trying to tackle two subs

Yep for sure.

brucek

[Wildt]

Ofcourse I have the 1.3 version.

I've seen the thread on how to replace the chip, and I'm up for it, just need to know how to get it?

And something unrelated - if I have a target level pretty much evenly dividing the dips and peaks of my speakers, REW only seemed to try and raise the dips, now lower the peaks. Am I doing something wrong?

[brucek]

Ofcourse I have the 1.3 version.

You can of course just enter the filters by hand. It's all I've ever done.

REW only seemed to try and raise the dips, now lower the peaks. Am I doing something wrong?

REW will only offer filters to reduce peaks. It won't touch the dips since it would require adding filters with gain.

You set the target.
Then Find Peaks from 20Hz to 200Hz
Then Assign Filters.
Then Optimize PK Gain & Q.

Can you show us a jpg of what you're talking about?

brucek

[huff]

I noticed the first few times I let REW calculate the filters (Find Peaks), it missed a peak. No problem. While on the "Filter Adjust" panel, open the EQ Filters window. Then change/add filters as needed. If you have "Corrected" checkbox checked below the graph, you'll see the "Corrected" graph line adjust itself on-the-fly.

[Wildt]

brucek wrote:

REW will only offer filters to reduce peaks. It won't touch the dips since it would require adding filters with gain.

Ah, that explains! My explanation was (100%) wrong - REW indeed only reduces peaks as you say. I just thought gain value was signed, so that it could do it both ways.

I'm writing the Behringer support, asking them to send me a 1.4 firmware chip.

[clubfoot]

Before adding filters you can use REW to fine tune your speakers by adjusting toe, width, distance and location for smoothest response at your usual seating location,...then add filters.

[Wildt]

Well, I ended up ordering the 1.4 firmware chip for the BFD from Hobbyroms, and the shipment from Canada to Denmark merely took from friday->wednesday.

Replaced the chip, and REW now correctly writes the filters to the BFD - even with 1-way MIDI (just 1 cable).

Success!

[Chrisbee]

Brian

I'm sure we'll all be fascinated to hear how the BFD affects the sound quality of your speakers.

The general opinion is that the BFD is detrimental to SQ.

Even if you only play with the lower frequencies the fullrange signal still has to pass through the BFD.

Please share your experiences with us.

[Doug Plumb]

You should take an average over the listening area of 6 measurements if you are going to measure room response for a single experiment.

Measuring a single curve to optimize response below a few hundred Hz and the upper modal range of likely around 100 Hz will yield essentially random results highly dependent on mic position.

Try taking two sets of measurements with the mic in displaced figure 8 patterns for each of two sets of measurements. Make the mic placements slightly different for each of the two experiments and see what kind of consistency you get in the measurements before EQing.

This is often why EQing is misused - people essentially perform experiments that are not repeatable below a certain frequency limit. EQ applied doesn't sound right.

Each experiment should be done with only one speaker playing - so do it with the left or right to get an idea of your ability to predict a response below X frequency and above the upper modal limit.

The conclusion will be that you cannot measure effectively between two frequencies - the upper modal limit and the frequency slightly above this. This frequency is determined as a wavelength = 4 times mic spacing. = about 1 hundred Hz to 2-3 hundred Hz in most rooms.

You can apply EQ above a few hundred Hz if you measure the speaker as I outline in my manual in ch4.




Properly applied EQ can do lots of good.

[Wildt]

Chrisbee wrote:

Even if you only play with the lower frequencies the fullrange signal still has to pass through the BFD.

Please share your experiences with us.

The fullrange speakers have terminals for low/high Q - and I'm running them bi-amped with two stereo power amps via Y-split XLR cable from the pre-amp. The BFD is only in the signal path to power amp driving the low Q.

[Doug Plumb]

How are you bi-amping full range speakers ?

[Wildt]

Doug Plumb wrote:

How are you bi-amping full range speakers ?

Like I said - they have seperate terminals for low/high Q.

[Doug Plumb]

I'm still not sure what you mean but if you mean that they have a LF low pass Q terminal for high and low Q then all you have on one terminal is a resistor that isn't on the other. I have no idea what you are talking about, that was just a guess. In which case there would be no point in bi amping.

If the Q refers to directivity than you have more than one speaker in the box.

[Wildt]

Well, maybe it's my poor english (I'm danish), but I think the confusion is due to my definition of a speaker is what you refer to as a speaker box. Hope that clarifies it.