Properties of Speakers

[zumbo]

It doesn't matter where they fire, you will hear port noise.

SheepStar

I agree. That is why I prefer a sealed design. I do believe "rear firing" will cancel-out some of that noise, or smooth it out.

 

[Buckle-meister]

On a midbass application, the port may output mid frequency resonances/noises. There for, it is preferable to have the port fire from the rear on such application(s).

It doesn't matter where they fire, you will hear port noise.

I agree. That is why I prefer a sealed design. I do believe "rear firing" will cancel-out some of that noise, or smooth it out.

Why are some ports placed on the front then? Is it purely for aesthetics?

It will be up to you to define your weighting.

Bah!

I am not familar with a material by that name.

Sorry WmAx, I meant Granitech (you'll need to scan through the text a little).

 

[zumbo]

Why are some ports placed on the front then? Is it purely for aesthetics?

Not sure. I have a guess. Let's say the speaker maker designed the speaker to reproduce sound a certain way. If the port is in the rear, there would be a bigger difference in sound depending on placement and room acoustics. I would think it would be much harder to guess what the sound would be during building and testing. No real way to design the speaker to sound a certain way.

Now, with a front port, I think it's a little different. The sound would change much less with placement and room acoustics. It is still a factor, but I would think it would be much less of one. So, the speaker would sound closer to the sound intended when used in different applications.

Shorter explanation. A front ported speaker may be easier to place due to room acoustics.

 

[Buckle-meister]

Shorter explination. A front ported speaker may be easier to place due to room acoustics.

Argh! Now you've gone and raised the opposite question; if the above is true, why don't speaker manufacturers always place ports on the front? After all, a speaker that sounds fabulous independant of a room's acoustics sounds like it'd be the Holy Grail to speaker manufacturers to me.

 

[Sheep]

Buckle, relax, we need you breathing

I have used front and rear firing subs (2 front, 1 rear) and the front firing ones gained very little from corner placement. That rear firing sub sounded different IMO. It excited differnt room modes, or something, because the output changed drastically. The Athena AS-P400 and Velodyne DPS-12 had a similar style response in my room while in the same spot. Ofcourse the Velodyne went down lower and had a different sound characteristic, but the peaks and valleys seemed to be in the same spots.

Take this with a grain of salt.

Maybe I will flip my sub around and tell you how it sounds, if you're nice.

SheepStar

 

[zumbo]

Argh! Now you've gone and raised the opposite question; if the above is true, why don't speaker manufacturers always place ports on the front? After all, a speaker that sounds fabulous independant of a room's acoustics sounds like it'd be the Holy Grail to speaker manufacturers to me.

Probably because the reasons listed about the nasty port sounds you can get from time-to-time. I am pleased with the ports on my towers, but not so pleased with the port on my sub(at HIGH volumes).

Let's look at the favorite design features I listed.

Sealed: Much more power is needed. The consumer has to invest in a high-power amp. There is a better market for speakers that can run off of a 100w receiver.

Curved or odd shaped cabinets: (a)More expensive to build. Have to pass the cost on to the consumer. (b)You can do some fancy work inside the cabinet and achieve similar results.

High-quality crossover network: See #2(a).

IMO, the best speakers are sealed, curved or odd shaped, and expensive. There is just not much of a market for that. But if one were to build their own, this is what I would do.

 

[WmAx]

If the port is in the rear, there would be a bigger difference in sound depending on placement and room acoustics.

Placing a port on an opposite side as the driver only makes placement a bigger problem due to logistics: You can't put the speaker right up against a wall because it will obstruct the port. Other than this, of course, you are moving part of the LF response the distance of the enclosure depth away from where a front port would create sound. Any change in posisition in the room will affect the LF interaction(s) in some way (magnitude of which is depedant in particular circumstances), so of course the same speaker with a front port as compared to the same speaker with a rear port, would sound different in the same spot.

-Chris

 

[WmAx]

It doesn't matter where they fire, you will hear port noise.

SheepStar

A subwoofer that creates audible port noise[chuffing] during normal operation is poorly designed. A midrange/midbass enclosure that creates audible port noise will be a different type of noise; being a narrow band of frequencies reflected/resonated in the tube. This varies in actual severity(is it audible in a particulare case, for example). But the majority of frequencies created in either case(subwoofer or midrange/midbass) will be high enough in frequency that the width of the cabinet will be substantial in relation to the frequency wavelength in air. There for, you can redirect the noise, and it will attenuate/diffuse to some degree before arrival, as compared to being a directly radiated from the front of the cabinet.

-Chris

 

[Buckle-meister]

Off-axis response

Speaker manufacturer's frequency response specifications are virtually always stipulated on-axis (though I believe that some stipulate additional, off-axis responses.

I know that people commonly 'aim' speakers slightly past them, so clearly good off-axis response is an advantageous property for a speaker to possess. Or is it?

If a speakers off-axis response isn't particularly good, why not simply turn the speaker so that it faces you directly? The front soundstage might alter a little, but ignoring room acoustics for the sake of simplicity, at least you'd be back to within ±3dB.

 

[WmAx]

I know that people commonly 'aim' speakers slightly past them, so clearly good off-axis response is an advantageous property for a speaker to possess. Or is it?

Consistent off axis response is very important if you want to have a consistent tonal balance across more than a single listening spot. Off axis response is critical to sound quality [as demonstrated in published perceptual research studies] in situations where room acoustics are a variable, as has been discussed in other threads.

If a speakers off-axis response isn't particularly good, why not simply turn the speaker so that it faces you directly? The front sound stage might alter a little, but ignoring room acoustics for the sake of simplicity, at least you'd be back to within ±3dB.

Yes, for the direct arrival sound, this is a solution. But it does not solve the problem of the uneven sound balance radiated into the ambient field. If you have treatments approaching the level found in an audio control room, then obviously, off axis response is of little concern so far as the room ambient field is concerned.

-Chris

 

[nfrnoman]

Is anyone out there aware of a component that converts traditional sound signal to multi-tonal vibration? I'm struggling to locate such an item and thought I might go fishing in the forums. Thanks.

 

[Buckle-meister]

For my next two questions, I first need to give a bit of background information.

I currently have Mission's Elegante e82 system in 5.1 configuration. My curent surround speakers are therefore the e80s, the specification for which maybe found here.

At some point in the future I'll be upgrading to a 7.1 configuration and maybe a 9.1 configuration. However, instead of buying 2 additional e80s for the surround-backs or 4 for surround-backs and presence, I am considering buying up to 4 of the larger e81s from Mission's larger e83 system, the specifications for which may be found here. If I do, then my little e80s would be perfect for use as the presence channels.

Note: I am not looking for advice on various brands of speaker to buy. I will definately be getting either the e80s or e81s as I want them to be in keeping with the look of my existing speakers (not to mention that they'd be timber matched).

So, my questions are:

1. How can it be that a speaker (e81) which has more drivers in it than another (e80) can be easier to drive? Why isn't the opposite true that the e81s require more power due to their additional driver when compared to the e80s?
2. Somewhat along the same lines, how is it that the lower bound figure for the e81's frequency response is the same as that of the e80s? If there're more drivers in the former why aren't they able to extend lower than the latter?

 

[Sheep]

1.)How can it be that a speaker (e81) which has more drivers in it than another (e80) can be easier to drive? Why isn't the opposite true that the e81s require more power due to their additional driver when compared to the e80s?

2.)Somewhat along the same lines, how is it that the lower bound figure for the e81's frequency response is the same as that of the e80s? If there're more drivers in the former why aren't they able to extend lower than the latter?

1A. More drivers equals more sound. I think adding an extra driver will give you a 2dB boost (if the crossover is right). The e81 can handle more power though.

2A. That would depend on the cabinet, tuning, etc.

SheepStar

 

[Buckle-meister]

Frequency response plots

Hello all (again ),

Out of curiosity I clicked Audioholics' home page's link to the Axiom speaker package and more specifically the frequency response of the EP600 subwoofer (scroll down and click on 'Graph' on the left hand side of the page). I couldn't help but notice that for all intents and purposes, the graph falls off in a straight line below the natural limit of the driver.

Now, I'm not picking on this speaker in any way. I only chose it because it was handy. Any plot for a woofer would, I suspect, be similar but for the driver's limits moving further up or down the scale. My question is:

Why does the response fall off in an almost straight line? If a driver reaches its lower limit and then progressively struggles to output at the same SPL, why doesn't the graph show a slowly, but progressively steepening curved response falling off (such as in the attached plot below)?

 

[Sheep]

Is that just a driver or a driver in a box?

When a driver isn't in a box (IE: Free Air) the back waves cancel out the front waves (in the low end). Thats why it rolls off steeper.

SheepStar

 

[Buckle-meister]

Is that just a driver or a driver in a box? When a driver isn't in a box (IE: Free Air) the back waves cancel out the front waves (in the low end). Thats why it rolls off steeper.

The Axiom's response, which is the steeper of the two, is in its own enclosure.

 

[Sheep]

The Axiom's response, which is the steeper of the two, is in its own enclosure.

Is it sealed? Looks similar to a sealed roll off in an anechoic chamber, but it rolls earlier then I've seen.

SheepStar

 

[Buckle-meister]

Is it sealed?

The axiom's enclosure is not sealed.

 

[Sheep]

The axiom's enclosure is not sealed.

Then..


EWWWW!

SheepStar

 

[WmAx]

Hello all (again ),

Out of curiosity I clicked Audioholics' home page's link to the Axiom speaker package and more specifically the frequency response of the EP600 subwoofer (scroll down and click on 'Graph' on the left hand side of the page). I couldn't help but notice that for all intents and purposes, the graph falls off in a straight line below the natural limit of the driver.

Now, I'm not picking on this speaker in any way. I only chose it because it was handy. Any plot for a woofer would, I suspect, be similar but for the driver's limits moving further up or down the scale. My question is:

Why does the response fall off in an almost straight line? If a driver reaches its lower limit and then progressively struggles to output at the same SPL, why doesn't the graph show a slowly, but progressively steepening curved response falling off (such as in the attached plot below)?

The Axiom graph is perfectly normal for a ported system. The graph that you attached to your forum post is probably a sealed system. A ported system attenuates at *24 dB/octave compared to *12 dB/octave for a sealed system. Also, your attached graph is not comparable to the Axiom graph. Please note the dB scales of both graphs.

*Note: The actual attenuation rate at any given point can vary dramatically, depending on the specific box alignment used. For example, one can design a non-conventional ported system with the roll off characteristic of a sealed system for much of it's attenuation range, only beginning to attenuate more rapidly at the lowest limits.

-Chris