Sealed monitor: Matching driver and box - Home Theater Forum and Systems - HomeTheaterShack.com

Old 04-08-12, 01:42 PM Thread Starter
Shackster

Join Date: Feb 2012
Posts: 7
Sealed monitor: Matching driver and box

Hi there guys,

I will be making a sealed monitor as an additional sound check while mixing.
I will be using a Visaton WS13E driver.

> On calculating the optimum volume using WinISD, it comes up with Vb=-13.47L.
1) What does this mean?

> Ideally this driver will be placed in a sealed box of inner volume 2.3L. That gives rise of about 6dB in the area of 200Hz.
2) The produced sound will be as its frequency response suggests, slightly shifted higher in the area of 200Hz?
3) In such case would there be a missmatch between driver action and volume of air in the box?
4) If I attach some absorbing material in the box will that make the box as being of larger volume?

Cheers
Costas
natureloop is offline

Old 04-08-12, 01:47 PM
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Russ

Join Date: May 2007
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Re: Sealed monitor: Matching driver and box

WinISD showing a negative volume is a bad sign, are you sure you input all T/S parameters correctly?

2.3L is a pretty tiny box. Also, a 6dB peak in the response is not at all desireable, I would strongly advise against building that. You should be able to extend much lower than 200Hz with a 5" driver.

 My Setup SI HT18, Sealed, NU3000dsp "HT 2.0" Monitors (704D, XT25) Flatpack Computer Speakers (ND91-8) The In-Walls
fusseli is offline
Old 04-08-12, 01:57 PM
Elite Shackster

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Re: Sealed monitor: Matching driver and box

Quote:
1) What does this mean?
Optimum volume, I'm assuming, is a Qtc = .707 alignment. Though whether that's optimum is up for debate.
Vb stands for something along the lines of Volume (Box). It is the internal air volume.

Quote:
> Ideally this driver will be placed in a sealed box of inner volume 2.3L. That gives rise of about 6dB in the area of 200Hz.
Look at the qts of the driver = 1.08

now qtc can never be lower than qts without external EQ. So you won't be able to get flat frequency response in any box (though it's possible it could work in an OB). The lowest qtc you could get is qts = qtc, which would only occur if the driver were mounted on an infinite baffle.

So realistically, there is no ideal box volume for this driver. However if winISD models suggest 13.5 L then that is probably a better bet than 2.3L - the only question is power handling.

Quote:
2) The produced sound will be as its frequency response suggests, slightly shifted higher in the area of 200Hz?
Yes, however there would be other factors at play. It seems that boost near 200hz is to compensate for baffle step (something which IMO should be done electronically because it occurs over a much wider bandwidth than this bump here). The driver in a box will probably have a dip from ~400hz to ~600hz, rather than a rise at 200hz.

Quote:
3) In such case would there be a missmatch between driver action and volume of air in the box?
This question is not clear.

Quote:
4) If I attach some absorbing material in the box will that make the box as being of larger volume?
It will reduce qtc from whatever you've got it at, but not much more than that. As I said earlier, your limitation on qtc however is not the box; it's the driver itself.

I'm going to be 100% honest with you - I think this project is probably a waste of your time and will not get you satisfactory results. If designing a crossover is an intimidating task (which it should be), you should strongly consider going the established design route, rather than mess with full range drivers and all their ills. Here is a design using a 5" midbass:

http://meniscusaudio.com/piccolo-p-1229.html

That I feel will be much more accurate. And for mixing, if you're not mixing for and on accurate systems, then you're just guessing and hoping. Even if a full range driver did have flat frequency response on a given test baffle, that does not mean that will be the case in a real box. It also means there may be stored energy or FM distortion. Most full range drivers still require contour networks and if you lack the ability to design one then I don't recommend a full range driver.

Don't underestimate us! Whether it be time, space, or alternate realities, they mean nothing to us! We will pierce the path and methods you've chosen! That is who we are!
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Old 04-08-12, 01:59 PM
Elite Shackster

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Re: Sealed monitor: Matching driver and box

Quote:
fusseli wrote: View Post
You should be able to extend much lower than 200Hz with a 5" driver.
Not likely without a resonator. I mean it's possible to get good extension from a sealed 5" driver, but those are the same 5" drivers that hit 40hz with a vent. More rare than common.

Don't underestimate us! Whether it be time, space, or alternate realities, they mean nothing to us! We will pierce the path and methods you've chosen! That is who we are!
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Old 04-08-12, 02:37 PM Thread Starter
Shackster

Join Date: Feb 2012
Posts: 7
Re: Sealed monitor: Matching driver and box

Quote:
fusseli wrote: View Post
WinISD showing a negative volume is a bad sign...
Quote:
GranteedEV wrote: View Post
...I'm going to be 100% honest with you - I think this project is probably a waste of your time and will not get you satisfactory results. If designing a crossover is an intimidating task (which it should be), you should strongly consider going the established design route, rather than mess with full range drivers and all their ills.
...
Quote:
GranteedEV wrote: View Post
Not likely without a resonator. I mean it's possible to get good extension from a sealed 5" driver, but those are the same 5" drivers that hit 40hz with a vent. More rare than common.

Very interesting!
So I will drop this driver!
The idea is not to mess with any crossover, much like the Auratone design.
Thanks a lot guys!
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Old 04-08-12, 04:14 PM
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Re: Sealed monitor: Matching driver and box

Quote:
natureloop wrote: View Post
The idea is not to mess with any crossover, much like the Auratone design.
Not sure what an auratone is, but in my opinion a well designed crossover / filter network will always get more transparency. Yes many crossovers are a mess but not all, and certainly not that jeff bagby one.

At the end of it all full range drivers are imperfect in onr eay or another. the closest you get to great sound without a crossover are large electrostat panels IE Quad and even they're not without their issues.

Don't underestimate us! Whether it be time, space, or alternate realities, they mean nothing to us! We will pierce the path and methods you've chosen! That is who we are!
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Old 04-08-12, 05:11 PM Thread Starter
Shackster

Join Date: Feb 2012
Posts: 7
Re: Sealed monitor: Matching driver and box

Quote:
GranteedEV wrote: View Post
Not sure what an auratone is, but in my opinion a well designed crossover / filter network will always get more transparency. Yes many crossovers are a mess but not all, and certainly not that jeff bagby one.

At the end of it all full range drivers are imperfect in onr eay or another. the closest you get to great sound without a crossover are large electrostat panels IE Quad and even they're not without their issues.
I agree with the above!

The auratone used-to-be/is a one driver monitor. It it used in order to evaluate the midrange as a whole, free from possible phase issues between tweeter-woofer of a 2way system.
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Old 04-08-12, 05:14 PM Thread Starter
Shackster

Join Date: Feb 2012
Posts: 7
Re: Sealed monitor: Matching driver and box

and its updated version is the avantone
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Old 04-08-12, 05:14 PM Thread Starter
Shackster

Join Date: Feb 2012
Posts: 7
natureloop is offline
Old 04-08-12, 05:23 PM
Elite Shackster

Kick logic 2 da curb

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Location: Calgary
Posts: 1,745
Re: Sealed monitor: Matching driver and box

Quote:
natureloop wrote: View Post
I agree with the above!

The auratone used-to-be/is a one driver monitor. It it used in order to evaluate the midrange as a whole, free from possible phase issues between tweeter-woofer of a 2way system.
Unless you listen in the wrong vertical axis, or in an anechoic chamber, phase issues in well designed loudspeaker crossovers are not audible. While phase distortion is measurable, it is instantly masked in any room with reflected sound. And I don't personally subscribe to the idea of absorbing everything and anything, not even for studio work.

As Dr. Floyd Toole said:

Quote:
" It turns out that, within very generous tolerances, humans are insensitive to phase shifts. Under carefully contrived circumstances, special signals auditioned in anechoic conditions, or through headphones, people have heard slight differences. However, even these limited results have failed to provide clear evidence of a 'preference' for a lack of phase shift. When auditioned in real rooms, these differences disappear.. ."
I'm not saying bad crossovers don't have issues from poor driver integration / relative phase, but phase distortion itself is not something to be getting overly caught up in. If there are issues with what you hear, they lie in design issues for the drivers, crossover, and box, not in the existance of those aspects themselves.

Don't underestimate us! Whether it be time, space, or alternate realities, they mean nothing to us! We will pierce the path and methods you've chosen! That is who we are!
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