Axiom Home Page Forums General Discussion Technical Questions M22 technical question

Hi all,

I just picked up a pair of m22's, and I noticed something strange. When I ran a frequency sweep, the volume dropped off at around 125Hz, then came back and stayed steady until around 80 (where it started to drop off at their low end). Could it be my room acoustics, or might something be wrong with my m22's?

Thanks,
Tom

pschar,
Are you using a SPL meter to measure the levels?


Side note to pmbuko: does this post bring me back to active status?

No, just my ears right now. I have to go pick one up. If I sit very close to the speaker, I don't hear a change; only when I'm at my listening distance of around 12'.

Mike
I was wondering where you've been.

A meter will be very helpful in determining just how much (if any) it is "dropping off". Listening to frequency sweeps by ear alone can be very misleading. In all probability, at the listening position there is a null at 125Hz. Get your self a meter. They are very useful and fun to use (in a hobby kind of way).

Hey bro' bray!

Just been lurking (acording to peter) and reading all the terrific posts. It seems that everytime I think I might have some useful stuff to say some of the sharper members here beat me to it.
I've also been spending/wasting some time over at the Audio Asylum planar forum. AA, what a zoo! Lots of kooky ideas floating around there but entertaining none the less.

In reply to:

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AA, what a zoo! Lots of kooky ideas floating around there but entertaining none the less.

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After reading about three threads there, I started to look for ways of blocking content from their servers in my browser... kind of a "Nut Nanny."

Bren R.

LOL!
Yes, the bulls#!t meter goes off the chart sometimes. It can be difficult to wade through to get to the sane stuff.

Sounds like room acoustics. I can promise that the first time you play with an SPL meter and some graph paper you will be horrified at the terrible, lumpy response you are getting from your nice accurate speakers.

Tom, welcome. What you describe is almost certainly due to the effect of room modes(such as the partial null at the listening position Mike mentions), as indicated by the different result at different spots. Frequency measurements at the NRC show that the M22 is flat in that area and there's no sort of individual sample defect that could have that result.

Before you despair too much, I guess we should mention that you can often improve the situation by playing with how the speakers are located in the room. If your room shape & size just sucks then you might have to do something more drastic like bass trapping (adding specialized panels to reduce the impact of the room modes).

EDIT -- if you can supply some info about the room it's pretty easy to run the dimensions through some software to get a rough idea of how the room modes will affect your response. That will also help to understand the options for improving things...

Thanks, guys!

Just to follow up: I picked up an SPL today and I'll get some better information with it over the weekend, but last night I raised my m22's from 16" to 24" and the dip at 125 went away! Not only that, but I heard decent bass into the 70's and 60's where before it tapered off at around 80...

Such is the importance of placement!