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How likely am i to have a spike in my room at 1500Hz?

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SteveRB

How likely am i to have a spike in my room at 1500Hz?
« on: 1 Aug 2016, 09:24 pm »
Hello,

How likely am i to have a spike in my room at 1500Hz?

I have a 600 sqft apartment. My living room / listening room is about 12'x14' and is open to the kitchen and dinning areas to one side. I have 8' ceilings.

Follow up, how likely am I to have a spike at 150Hz as well...?
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JLM

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Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #1 on: 2 Aug 2016, 12:12 am »
A 1500 Hz sound wave is 8.8 inches long (depending on your altitude and the barometric pressure), so it's not due to the room.  Could be something resonating in the room.  At this frequency you should be able to locate it by ear.

The last time this came up it was a loose window pane.
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Big Red Machine

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #2 on: 2 Aug 2016, 12:26 am »
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*Scotty*

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #3 on: 2 Aug 2016, 01:09 am »
As JLM said with 1500Hz having a wavelength of 8.8inches, it is high unlikely that you can have a room dimension related resonance at 1500Hz.
You could easily have a loudspeaker with an off axis bulge in it frequency at 1500Hz that is rattling around the room. Getting the speakers farther away from the sidewalls and adding some diffusion and absorption type room treatments could help if your problem is due to this.
Scotty
« Last Edit: 2 Aug 2016, 03:17 am by *Scotty* »
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richidoo

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #4 on: 2 Aug 2016, 02:35 am »
This calculator will help you see where the primary axial room modes and their harmonics are.
http://realtraps.com/modecalc.htm

Also handy: http://www.mcsquared.com/wavelength.htm

150Hz = 7.5 feet, typical ceiling height, so that's a prime suspect for a room mode. It is low enough that carpet will have only small effect on it. Wall modes can be affected by moving the speakers horizontally to move the peak away from listening position, but ceiling modes are more difficult. But try moving speakers to see if it helps anyway, since true axial ceiling mode should be localized near the speaker.
http://www.gikacoustics.com/what-are-room-modes/
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G Georgopoulos

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Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #5 on: 2 Aug 2016, 02:52 am »
all rooms have resonance ,acoustic feedback resonance in public address systems proves this,with hifi (nonacoustic feedback) systems this manifests as spikes of resonance as well, only less dramatic  :)
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SteveRB

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #6 on: 2 Aug 2016, 07:24 pm »
Thanks guys,

Looks like I try moving the speakers around a bit -- very little room to reposition though. Not much I can do about the ceiling height for now.

I can certainly look into padding down the first reflection on the left channel.
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SteveRB

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #7 on: 2 Aug 2016, 07:28 pm »
What brought this up was a recent test of my two way speakers. Each section had a spike at 1500Hz -- obviously when combined it seems more apparent.
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redbook

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Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #8 on: 2 Aug 2016, 07:58 pm »
 Well maybe a job for an equalizer to determine where the problem frequency occurs. :thumb:
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SteveRB

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #9 on: 2 Aug 2016, 08:02 pm »
Quote from: redbook on  2 Aug 2016, 07:58 pm
Well maybe a job for an equalizer to determine where the problem frequency occurs. :thumb:

ugh... that's not exactly on my to-do list.
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redbook

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Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #10 on: 2 Aug 2016, 08:12 pm »
Worth a try if you have a very good unit.  :thumb:
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SteveRB

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #11 on: 2 Aug 2016, 08:16 pm »
Quote from: redbook on  2 Aug 2016, 08:12 pm
Worth a try if you have a very good unit.  :thumb:

can you provide an example?
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redbook

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Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #12 on: 3 Aug 2016, 01:47 pm »


I have an API 5500. parametric unit
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richidoo

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #13 on: 3 Aug 2016, 04:22 pm »
If you use foobar or JRiver as digital source you can program an EQ notch to see if that helps.

Foobar and its plugins are free, and you can use the PC soundcard as your source for this simple EQ test. 
Google "foobar parametric EQ" for various plugins.

Could it be a cone breakup?
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SteveRB

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #14 on: 3 Aug 2016, 05:22 pm »
I use only analog source and tube amplification.
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Hipper

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #15 on: 3 Aug 2016, 08:08 pm »
Can you post the test results?

Can you hear these spikes?
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SteveRB

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #16 on: 3 Aug 2016, 08:15 pm »
Quote from: Hipper on  3 Aug 2016, 08:08 pm
Can you post the test results?

Can you hear these spikes?

These are my crude tests, in room at about 1m.


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richidoo

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #17 on: 4 Aug 2016, 02:57 am »
Woofer and tweeter both have same shape peaks at 1500, so it's prolly room or something else in the room ringing at that freq.

You can measure again 1/4" from the drivers to remove most of the room's effect. You'll have to turn the speakers way down, and that takes the room echos down too. The amplitude of the peaks on woof and tweeter should flatten out or disappear unless it's coming from the system.
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SteveRB

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #18 on: 4 Aug 2016, 02:44 pm »
Yes. I started this thread because of the peak in both the woofers.

What causes this: patio door, coffee table, a lamp...?
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Hipper

Re: How likely am i to have a spike in my room at 1500Hz?
« Reply #19 on: 7 Aug 2016, 08:13 pm »
The reading shows the measurements up at 150Hz (by about 8dB), up at 1500Hz (by 5dB) and up above 10,000Hz (10kHz, by 8dB), with a smaller peak at 680Hz.

The woofer peaks at 150Hz, 1500Hz and starts to rise at 10kHz, whilst the tweeter does not peak at 150Hz, does at about 1500Hz, and also above 10kHz. Both the woofer and tweeter also have the smaller peak at around 680Hz.

Using a lower smoothing would reveal more detail and likely higher dBs for the peaks.

As only the woofer peaks at 150Hz I think this is most likely caused by the room and can be altered by positioning. Moving the speakers or the measuring positioning (and for listening, your chair), will alter all frequencies but most notably up to around 300Hz. Bass traps will also help in this region. Above that and it is absorbers, or diffusers.

The 1500Hz peak is perhaps a resonance. It could perhaps also be hum, from speakers or amp maybe, a fault with the speakers, or with other parts of the playback system.

To see if it's a resonance, you need to trigger it. Of course you can do this by playing the appropriate frequency. The nearest typical test tone is 1600Hz. A warble tone of 1600 Hz makes a range of frequencies around 1600Hz but I don't know what that range is. Then you use your ears to find it. Anything can cause it from large sheets, like glass, to a loose light bulb. It's quite a high pitched frequency.
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