Studio monitors response curves measured today with REW (input please)...

[Ally-007]

Hi folks. I just acquired a pair of used Behringer Truth B2031A monitors, as I wanted something with 8" woofers (and also front-ported, as I need to have them backed up against the wall of my small home studio). Here is my initial measurement graph (1/6 smoothing), showing the left and right speakers. I thought the Truth B2031A was supposed to have a pretty flat frequency response, but this is not reflected in my readings of today (see graph). I think the high peak at around 140Hz is a room resonance between ceiling and floor (it has shown up when measuring other speakers in the same room) but I'm surprised to see such a wildly un-flat curve throughout the frequency range. Measurement mic placement was near-field (same as my usual listening position). Can anyone offer any insights, from looking at the graph? Thank you!

 

[Papanate]

Is your room balanced? - but I would say that the Behringers are not flat - see the response curve below - if you’re handy with a soldering iron and can do micro work you can get the Truths to be relatively flat with this set of Mods: Behringer Truth B2031A - how truthful is it?

 

[Ally-007]

Is your room balanced? - but I would say that the Behringers are not flat - see the response curve below - if you’re handy with a soldering iron and can do micro work you can get the Truths to be relatively flat with this set of Mods: Behringer Truth B2031A - how truthful is it?

View attachment 150077

Thanks for the reply. That curve (I've seen before, at noaudiophile.com) was reportedly done outdoors. Most of it (apart from the prominent bass peak) falls roughly within about a 5dB band, which I would call pretty good. My curves, on the other hand, sit roughly within a 15dB band, which is drastically worse. Yes, my test was done indoors, but the result is still much worse than vastly cheaper speakers I've tested in the same room, such as Edifier MR4 and Moukey M20-3. I'm not sure why. But at least they are flatter than my old passive Tannoy Reveals from 2003.

 

[Papanate]

Thanks for the reply. Where did you find the above curve? Does it represent a Truth B2301A, and was the measurement done in a room or outdoors? Most of this curve (apart from the prominent bass peak) falls roughly within about a 6dB band, which I would call reasonably good. My curves, on the other hand, mostlly sit roughly within a 15dB band, which is drastically worse, and much worse than vastly cheaper monitors I've tested in the same room, such as Edifier MR4 and Moukey M20-3.

I got it from Behringer - you REW sample looks close to the Behringer Frequency sample.

 

[Ally-007]

I got it from Behringer - you REW sample looks close to the Behringer Frequency sample.

Thanks. It's the same image I've seen at noaudiophile.com. That curve looks visually similar to mine... but when taking the dB scale (y axis) into consideration, mine is actually much worse (like about 3x worse). I'm not sure why. Maybe it's due to room resonances. However, I've tested vastly cheaper speakers in the same room, such as Edifier MR4 and Moukey M20-3, which both showed up as much flatter. Only my old 2003 passive Tannoy Reveals looked worse. The book 'Mixing Secrets' by Mike Senior shows the Truth B2031A curve as being exceptionally flat.

 

[Papanate]

The book 'Mixing Secrets' by Mike Senior shows the Truth B2031A curve as being exceptionally flat.

Maybe they are flat - but everyone I know who has/had them says the same thing - which is they aren’t flat at all - and emphasize bass too much.

 

[bouldersoundguy]

What mic are you using?

The 50 Hz peak and the 68 Hz dip look like possible room effects.

The waterfall display might tell us more about what's happening. The frequency response alone lacks all time information.

 

[Ally-007]

Maybe they are flat - but everyone I know who has/had them says the same thing - which is they aren’t flat at all - and emphasize bass too much.

That's certainly true in my room. I haven't tried changing the room EQ switches on the amps yet. If that doesn't fix it, my 31-band hardware equalizer probably will, when it arrives. To my ears, the higher frequencies could be more pronouced, but the graph doesn't say the same, so it must be my old ears!

 

[rob aylestone]

Take the speakers outside and repeat the test - I bet you get pretty much the factory published curve. In my studio (which I think sounds nice. spikey response curves are absolutely normal. I have an app on my phone and playing pink noise, I expected a pretty even display. Moving the phone around is amazingly strange when you see what a small movement does to the display. If you use the EQ, you will often make it worse. Unless the room is flat - the EQ will be a bit over-enthusiastic, and when you get it flat, mixes produced using that curve will sound very odd elsewhere. If you have some good headphones, repeat the test with them, with the mic sealed into the headphone cavity. That will be different.

 

[bouldersoundguy]

That's certainly true in my room. I haven't tried changing the room EQ switches on the amps yet. If that doesn't fix it, my 31-band hardware equalizer probably will, when it arrives. To my ears, the higher frequencies could be more pronouced, but the graph doesn't say the same, so it must be my old ears!

On-third octave equalizers are very blunt instruments. You'd be better off with two or three bands of fully parametric eq than 30 bands of fixed-width, fixed-frequency filters. And eqs aren't really suited to fixing room issues. At best, they can mitigate some problems at one very precise listening position. The proper way to address room problems is with acoustic treatment.

 

[Ally-007]

What mic are you using?

The 50 Hz peak and the 68 Hz dip look like possible room effects.

The waterfall display might tell us more about what's happening. The frequency response alone lacks all time information.

Thank you for your input, B. The measurement mic is a Behringer ECM8000. I'm not too familiar with waterfall analysis, so I hope I have set up the following graph suitably for analysis purposes. It shows up to 700Hz (right speaker only). If you want me to change the graph settings, or post the left speaker result, please let me know!

 

[bouldersoundguy]

Narrow down the time frame from 2 seconds (2001 ms) to about 200 ms. Most of what we're seeing in that graph is steady state noise in your room that has nothing to do with the output of your speakers.

 

[Ally-007]

On-third octave equalizers are very blunt instruments. You'd be better off with two or three bands of fully parametric eq than 30 bands of fixed-width, fixed-frequency filters. And eqs aren't really suited to fixing room issues. At best, they can mitigate some problems at one very precise listening position. The proper way to address room problems is with acoustic treatment.

I see. Now I wish I hadn't ordered it! Still, it was cheap (used), on eBay, so maybe it will come in handy for something. It has a subwoofer out with adjustable crossover, a feedback detection system, and a couple of other handy features so hopefully it'll be worth having around.

 

[Ally-007]

Narrow down the time frame from 2 seconds (2001 ms) to about 200 ms. Most of what we're seeing in that graph is steady state noise in your room that has nothing to do with the output of your speakers.

Ah, I see. Here it is to 200ms - thanks:

 

[bouldersoundguy]

I see what might be a resonance around 265, but otherwise not much resonance. I think the cases where it transitions sharply from a downward slope to a horizontal ridge are more likely room noise. I suspect that the main thing that's happening is boundary effect, a boost in LF due to being placed against a wall (see diagram on back of speakers). You might also be getting reflections off ceiling, wall or desk surfaces that are adding to or subtracting from (depending on timing) certain frequencies. Treating first reflection points may flatten things out in those areas. Running the tests outdoors on a tallish stand would tell us more, but that can run into issues with wind or extraneous noise.

 

[Ally-007]

I see what might be a resonance around 265, but otherwise not much resonance. I think the cases where it transitions sharply from a downward slope to a horizontal ridge are more likely room noise. I suspect that the main thing that's happening is boundary effect, a boost in LF due to being placed against a wall (see diagram on back of speakers). You might also be getting reflections off ceiling, wall or desk surfaces that are adding to or subtracting from (depending on timing) certain frequencies. Treating first reflection points may flatten things out in those areas. Running the tests outdoors on a tallish stand would tell us more, but that can run into issues with wind or extraneous noise.

Oh, that's very interesting - thank you so much. I must investigate those possibilities and see what can be done to mitigate them, and see if there's an improvement. Yes, I intend to test the speakers outdoors, when I get the chance. It will be very interesting to compare the two graphs: indoors and outdoors. I live in a rural area, so extraneous noise is not likely to be an issue, outdoors on a calm day. My small home studio has no typical acoustic treatment, but the walls are mostly covered with shelving, loaded with a lot of sound diffusing/absorbing junk, such as books and boxes of audo kit, etc. Only about 20%-25% of the walls are uncovered. Likewise for the carpeted floor, actually. The ceiling is the only big surface that's uncovered, but that is plasterboard with a good 9" of glass fibre insulation sitting on top, which I guess must have some dampening effect.

If I run a sine wave sweep through my monitors, from my sitting position, there are audible dips centered around 225Hz and 390Hz, and the most audible hump is at around 150Hz.

For what it's worth, here are the resonances predicted by the amroc room mode calculator, based on my room dimensions:

 

[Ally-007]

Take the speakers outside and repeat the test - I bet you get pretty much the factory published curve. In my studio (which I think sounds nice. spikey response curves are absolutely normal. I have an app on my phone and playing pink noise, I expected a pretty even display. Moving the phone around is amazingly strange when you see what a small movement does to the display. If you use the EQ, you will often make it worse. Unless the room is flat - the EQ will be a bit over-enthusiastic, and when you get it flat, mixes produced using that curve will sound very odd elsewhere. If you have some good headphones, repeat the test with them, with the mic sealed into the headphone cavity. That will be different.

Thanks for the suggestions, Rob. Yes, I must get organised for outdoor speaker testing. I have a shedload of speakers that all need testing outdoors. I will devote a day to it, as soon as I can. Yes, I've noticed how the SPL of different frequencies changes according to listening position. However, I alway sit in the same position when mixing & mastering, so that position is the only thing that concerns me. I do have have some flat-response headphones that I use for checking mixes.

 

[Ally-007]

Is your room balanced? - but I would say that the Behringers are not flat - see the response curve below - if you’re handy with a soldering iron and can do micro work you can get the Truths to be relatively flat with this set of Mods: Behringer Truth B2031A - how truthful is it?

Thanks for reminding me of that site/post. I haven't seen the circuit boards in the flesh yet, but if they are the same as his, I will probably try those mods. Going by the photos, each resistor seems to have a nice big blob of solder at each end, which is handy, as I'm not the greatest solderer on the planet. I'd certainly be happy if I can achieve the same response curve that he achieved. I wish he had also posted a way to change the sensitivitey of the auto-standby feature; the biggest bugbear of these speakers, for me, is that they are constantly going into standby mode, and stay that way, until I crank up the volume on my audio interface, quite high, to get them to fire up again. I tend to work at low volumes, which doesn't help.

 

[rob aylestone]

Twenty different monitor speaker models, twenty different sounds. If a flat frequency response made them all sound the same, there would be no need for expensive ones! Same with mics. Ever recorded with a flat measurement microphone? Might well be good for producing plots, but rubbish for recording music! It is not just frequency response, its how they reproduce transients. Tinkering with a signal chain’s EQ does not turn a Behringer into a Genelec. This is audiophile thinking. This stuff is not something any world class studio would support. Find a world class engineer who has any time for this stuff and promotes it? It’s fine as a hobby for people who like experimenting, but I just cannot subscribe to the silly stuff.