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#406711 - 08/20/14 01:23 PM Re: New Video! Designing the M100 [Re: Amie]
Scottinwa Offline
frequent flier

Registered: 08/18/14
Posts: 13
Loc: Washington, USA
I too found Sibilance due to the following:
- Source material
- Poor electronics (amp, preamp and or digital source. Never got sibilance from vinyl unless it was on the recording.
- Crossover.

Crossover? Yes. Midfi speakers (not axiom) use electrolytic caps in the crossover, occasionally bypass by a small value mylar cap. Electrolytics simply don't belong in the path of the mid or tweeter. As a woofer choke, OK. These 39 cent caps are 10-20% value, and smear the signal (time). Sibilance is one of the deleterious effects.

Simple proof: I just refurbish four Bose 301 speakers. Bose are the king of thump and sizzle. Most blame the sibilance on the cheap drivers....but that's not the whole story.

When I rebuilt the 301's, I replaced the crossover caps with 5% metallized polypropelene. The result was a much cleaner treble and 90% of the sibilance and grain was ameliorated.

I had some ATC SCM 12 which are ruthlessly revealing. I was getting some sibilance and grain, until I upgraded my then cheap technics cd player to an Arcam Alpha 9. Sibilance was GONE.

A final source of noise might be power. If you live near an industrial park or military base, there is a ton of hash in the power, and even a modest power filter helps.
_________________________
Great Speakers start with great engineers.

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#406717 - 08/20/14 06:16 PM Re: New Video! Designing the M100 [Re: Amie]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5420
Loc: Bowmanville, Ontario, Canada
"In My Head" from No Doubt's Rock Steady album is referred to as "The Sibilance Song" around here, although I guess strictly speaking there are more fff sounds than sss sounds.

When I read the HTS review my first thought from looking at distance & toe-in details for the M100's (before reading the actual review) was "they're too close to the front wall and toed in too much" - I find that even M60s sound bright & bass heavy like that. In fairness, folks who own the other speakers are probably making similar comments about how *their* speaker would have sounded better if only blah blah blah.

The big revelation for me was that (a) if you treat *all* the first reflection points properly you don't have to toe in so much to get really good imaging and (b) the "BBC dip" that some speakers have (but not Axioms) also seems to reduce the fatiguing impact of untreated reflection points.


Edited by bridgman (08/20/14 06:26 PM)

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#406912 - 08/31/14 02:15 AM Re: New Video! Designing the M100 [Re: Amie]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5420
Loc: Bowmanville, Ontario, Canada
Speaking of port plugs... any idea how they impact the frequency response, ie whether they just reduce port output or whether they shift the enclosure tuning as well ?

Reason I'm asking is that when I look at the FR charts for speakers with the HP woofers they seem just a bit peaked-up in the 50-100 hz range which usually ends up bothering me, however...

(a) I remember there being some discussion about the anechoic chamber readings needing adjustment below a certain freq (80 Hz ?) due to finite size so maybe there is some room reinforcement already present, and

(b) if the port plugs have the same effect as they do on SVS subs (they seem to lower the port tuning, so bass drops off a bit sooner but extends lower) a bit of port plugging would probably make the FR ideal for me. The legend on this chart has 4 entries and only 3 lines (with no colours), but I'm pretty sure green is all 3 ports open and purple is one port plugged.



Obviously I'm hoping someone got bored one rainy day in Dwight and ran a set of tests on an M*HP with and without port plugs.


Edited by bridgman (08/31/14 02:27 AM)

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#406914 - 08/31/14 03:14 AM Re: New Video! Designing the M100 [Re: Amie]
exlabdriver Offline
connoisseur

Registered: 09/07/11
Posts: 1029
This may not be relevant, but when I plugged the rear port on my M3s that are on stands in corners that were excessively reinforcing the bass response, the sound cleaned up dramatically.

I was able to completely remove the EQ from the bottom end & run them flat from my receiver. So, at least in my case, port plugging worked exceedingly well & I don't perceive that I lost anything except all of the muddiness...

TAM


Edited by exlabdriver (08/31/14 03:20 AM)

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#406915 - 08/31/14 03:14 AM Re: New Video! Designing the M100 [Re: Amie]
exlabdriver Offline
connoisseur

Registered: 09/07/11
Posts: 1029
Deleted double post...

TAM


Edited by exlabdriver (08/31/14 03:15 AM)

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#406925 - 08/31/14 09:55 PM Re: New Video! Designing the M100 [Re: bridgman]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10395
John, yes using port plugs does have an effect on the enclosure tuning besides reducing the port output. The charts you included show the response expected from a vented enclosure in the top curve(i.e., a sharp drop off at 24dB/octave below the 3dB down F3 point). The bottom curve, presumably with the plugs installed, shows the higher F3 frequency, but with a slower 12dB/octave drop off below that which is typical of a sealed enclosure.

This doesn't indicate that an optimally tuned vented enclosure can be converted into an optimally tuned sealed enclosure simply by using port plugs, but situations involving excessive room resonances in the mid-bass frequencies can be partially corrected with the use of the plugs.
_________________________
-----------------------------------

Enjoy the music, not the equipment.



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#406936 - 09/01/14 04:05 PM Re: New Video! Designing the M100 [Re: bridgman]
Nick B Offline
devotee

Registered: 08/05/06
Posts: 496
Originally Posted By: bridgman
Speaking of port plugs... any idea how they impact the frequency response, ie whether they just reduce port output or whether they shift the enclosure tuning as well ?

Reason I'm asking is that when I look at the FR charts for speakers with the HP woofers they seem just a bit peaked-up in the 50-100 hz range which usually ends up bothering me, however...

(a) I remember there being some discussion about the anechoic chamber readings needing adjustment below a certain freq (80 Hz ?) due to finite size so maybe there is some room reinforcement already present, and

(b) if the port plugs have the same effect as they do on SVS subs (they seem to lower the port tuning, so bass drops off a bit sooner but extends lower) a bit of port plugging would probably make the FR ideal for me. The legend on this chart has 4 entries and only 3 lines (with no colours), but I'm pretty sure green is all 3 ports open and purple is one port plugged.



Obviously I'm hoping someone got bored one rainy day in Dwight and ran a set of tests on an M*HP with and without port plugs.


Check out http://www.data-bass.com/systems


More specifically look at the SVS PB13 Ultra. If you click on the different modes (15 Hz, 20 Hz and sealed) you can see how many things change. For example, the long term output compression, waterfall plots and distortion measurements vary quite a bit from one mode to another. The same ideas will be true if you have the SVS PB12+. Just it will have a bit less extension and a bit less maximum output before compression sets in and distortion begins to rise, in comparison to its bigger brother.

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