Frequency Response of Axiom Speakers

[JeffB]

From the Axiom website
http://www.axiomaudio.com/m60ti_main.html
M60ti -- 37Hz-22kHz +/- 3db

http://www.axiomaudio.com/m80ti_main.html
M80ti -- 34Hz - 22kHz +/- 3db

However, looking at the graphs that Axiom provides it looks like -3db at 65Hz for both speakers.

I am wondering what the deal is.

 

[wilkenboy]

However, looking at the graphs that Axiom provides it looks like -3db at 65Hz for both speakers.

I am wondering what the deal is.

A classic example of interpretation of data and specsmanship.

The average reader would look at the frequency response and notice a nice, flat response at around 90 dB from around 70Hz up to 18 kHz, just eye-balling it. That would be 90dB +/- 3dB, or 87 to 93 dB. Using those numbers you are right on, the -3dB point appears to be right around 65 Hz. Frequency response of the M60ti attached for reference.

However, Axiom has likely chosen 87 dB as their reference value. Doing the +/- 3 dB math yields 84 dB to 90 dB, and with that range the Axiom M60 easily meets the 37 Hz claim (although the 22 kHz claim is still dubious).

The trick is that you will likely calibrate this speaker level using pink noise, and your ear or an SPL meter would set this to where the bulk of the energy is coming from. The result is that the bass would be 6 dB down (not 3 dB) from the reference listening level.

Morale of the story: +/- 3 dB numbers can be decieving. Frequency response graphs mean much more, but your ear is the best test equipment on the planet.

~Josh

 

[silversurfer]

great explanation!

 

[wilkenboy]

Thanks, all those electrical engineer classes are worth something, I guess, de-bunking curious speaker specs!

~Josh

 

[Pat D]

From the Axiom website
http://www.axiomaudio.com/m60ti_main.html
M60ti -- 37Hz-22kHz +/- 3db

http://www.axiomaudio.com/m80ti_main.html
M80ti -- 34Hz - 22kHz +/- 3db

However, looking at the graphs that Axiom provides it looks like -3db at 65Hz for both speakers.

I am wondering what the deal is.

I think Axiom does exaggerate the depth of the bass response in their text but they are hardly alone in this. If you check out the NRC measurements for the M80ti on the Soundstage site, you can see that the -10 dB point is in the mid-30s, so 34 Hz is a realistic estimate of the limit of useful bass in a typical room.

http://www.soundstage.com/revequip/axiom_millenniam80ti.htm

http://www.soundstagemagazine.com/measurements/axiom_m80ti/

So, they have quite good response in the bass and you can see what the reviewer says about it.

I haven't heard an Axiom speaker for many years though I would like to, just for the interest.

 

[JeffB]

Wilkenboy,
That was a very good answer, and I like how you were able to post the graph.

However, now that I know that I am not completely incapable of reading the response graph, I still think the numbers are wrong.

I had assumed 89db as the reference point as the speaker is rated with a sensitivity of 89db at 1 watt/1 meter.

The 37Hz point on the graph is about 83db. So +3db brings the value to 86db.
From 70Hz to 17kHz the entire response graph is well above 86db at closer to 88 or 89 db.

I brought this whole topic up, not really to give Axiom a bad rep, but I sort of thought I had noticed this on some other graphs. Only now, I don't know where to find any other graphs. I am starting to wonder if the lower Hz number on speakers are remotely reliable.

I have been curious about the proper blending of sound with a subwoofer. In my recent demoing experience, bookshelves have been much harder to blend than floorstanders. Even though bookshelves are often rated down to 55Hz or so, which is well within subwoofer territory. Unless they are not really going down to 55Hz. Hell, if two 6.5s are only going down to 65Hz, what does one 6" in a small box really do.

 

[gene]

I thought I would chime in here to clarify some of the misinformation in this thread. The truth of the matter is the Axiom measurements were conducted anechoically thus the very low frequencies aren't accurately represented since the chamber isn't big enough.

Please note our comments on page2 of Rays review that discusses this:

As you can see from the above 1 meter frequency response, the M80ti measured very well and has a relatively flat anechoic response. The M80ti has an effective low frequency response of about 40-45Hz which is somewhat masked in the measurement since anechoic chambers bass response below 85Hz begin to taper off.

the 18kHz dip is likely a measurement anomaly from the plastic cap in the center of the tweeter (which some refer to as a phase plug). It's purpose is to eliminate driver ringing in the audible range while also increasing driver efficiency.

I hope this helps.

 

[wilkenboy]

I thought I would chime in here to clarify some of the misinformation in this thread.

I hope what I said about FR interpretation was not mis-information! Gene, I'll take whatever punishment necessary to atone for my sins. I committed them without knowing.

The truth of the matter is the Axiom measurements were conducted anechoically thus the very low frequencies aren't accurately represented since the chamber isn't big enough.

Gene makes an excellent point. Anechoic responses do not account for the natural lower extension speakers receive when coupled with the room response. So realistically with this speaker (or any other speaker, or sub for that matter) the anechoic response can be considered very conservative on low frequency. That's why you see some manufacturers state an anechoic response and an in-room response.

the 18kHz dip is likely a measurement anomaly from the plastic cap in the center of the tweeter (which some refer to as a phase plug). It's purpose is to eliminate driver ringing in the audible range while also increasing driver efficiency.

I'm no speaker design expert, but I do know measurements, even in the most pristine and carefully set up environments can be subject to all sorts of quirky stuff. Gene, would this dip be apparent to a user (or test equipment) at a reasonable distance?

DEFINETLY not trying to bash Axiom, I haven't heard their line, but the net and this forum are full of glowing reports. I'm simply trying to point out some common ways to interpret data, and how summaries of data can sometimes be insuffucient to describe what you could hear. There's hundreds of speakers out there claiming 40 Hz to 20 Khz +/- 3dB, at all price ranges, with all different "types" of sound. So take that spec for what its worth.

I love data and testing... but I love my ears more.

~Josh

 

[wilkenboy]

I like how you were able to post the graph.

I went to Axiom's site, downloaded the graph as a jpg to my local drive, and then used the "manage attachments" button to upload it to the site. You may have to scroll down to find it.

~Josh

 

[3db]

I also noticed the lack of the dip

around the 300Hz region which is a common trait among floorstanding speakers. I wonder how they were able to achieve that. The other thing I woud like to see are some frequency response curves done in r/w conditions ranging from a bright room to an overly damped room just to see the differences.

The other question I always have is; At what reference value (volume wise) do manufacturer's spec their speakers?

 

[jcPanny]

In my opinion . . .

The +/-3db spec listed by Axiom is a useful metric for comparing the frequency response of different speakers they manufacture, or comparing different manufacturers.
The fact that Axiom will publish frequency response charts for their speakers shows that they are confident in the design of their product.
How many other speaker manufacturers do you know of that are willing to do this?
What do you think the frequency response of a set of Bose speakers would look like?

 

[jaxvon]

They would look like this:

 

[silversurfer]

The +/-3db spec listed by Axiom is a useful metric for comparing the frequency response of different speakers they manufacture, or comparing different manufacturers.
The fact that Axiom will publish frequency response charts for their speakers shows that they are confident in the design of their product.
How many other speaker manufacturers do you know of that are willing to do this?
What do you think the frequency response of a set of Bose speakers would look like?

You may want to read this thread:
http://www.avsforum.com/avs-vb/showthread.php?p=5979142&&#post5979142

Don't read too much into specs.