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Advice on small loudspeakers, Sealed or Ported?
Arnold B. Kruege...
post Feb 13 2013, 15:33
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QUOTE (mzil @ Feb 12 2013, 15:37) *
Car speakers are designed for cars.


Not so much. Car speakers are designed to work in certain spaces with enclosures that fit into available space. The space inside a car follows the same laws of physics as any other room. The space for the enclosures is limited, but that is often the case anywhere else.

In a car there are major concerns with clearing enough free space so that speakers can operate free of obstructions, adversely reflecting nearby surfaces, and panel resonaces.

The drivers are themselves pretty conventional, often drawn from the same stocks and designs that are used for home speakers. The mounting holes may get moved around, etc. The drivers are bought in 10,000 and larger lots, so the manufacturers can be very accommodating.

Given that I live in the Detroit area and the audio community here is of a reasonable size, I have the opportunity to converse freely with many of the designers of car sound systems and their consultants. Some of these people are my closest friends. This is what they tell me. They tell me that a speaker driver is pretty much a speaker driver. Some of these people are just about the sole designers of systems that have sold 100,000s of copies with retail values up to several thousand dollars.

As a rule US manufacturers have vehicle sound quality, even for base systems, as an unusally high priority. A $50,000 car with a bad sound system is so much junk to most owners when they drive it routinely. Of course our car designers pay attention to cup holders as well. ;-)

There are a number of engineering samples that must be disposed of at the end of a project and some of them end up in personal systems. The designers whip out the Thiel/Small parameters for the driver and run some box design program and build accordingly. Sound familiar? ;-)
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mzil
post Feb 13 2013, 17:34
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QUOTE (Arnold B. Krueger @ Feb 13 2013, 10:33) *
QUOTE (mzil @ Feb 12 2013, 15:37) *
Car speakers are designed for cars.


Not so much. Car speakers are designed to work in certain spaces with enclosures that fit into available space.

Car speakers such as his, which sell for $2.15 in US dollars for TWO, are typically designed to have no specific "enclosure", at all, and work instead on the principal of infinite baffle, for example on a rear deck where the volume of air in the trunk is relatively vast [and immaterial to the driver's performance, it just needs to be isolated from the forward radiation to prevent bass cancellation] compared to the smaller ported or acoustic suspension box designs we might use in a home.

This post has been edited by mzil: Feb 13 2013, 18:30
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krafty
post Feb 13 2013, 23:06
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I am doing a port on the front of the box, below the midrange.
It will be a 14,3 cm (w) x 0,75 cm (h) opening and the port length is 9,8 cm.
It matches the size of the port volume and length suggested by WinISD.

I am building 1st Order But. Crossovers 6000Hz/12db. One inductor and one capacitor.
I am also following an article that deal with the piezo tweeter.

Over, DIYaudio, looks like people just walked away after seeing my car speakers.
I think they find it hopeless to work with it on this particular situation that they don't even bother replying.
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krafty
post Feb 13 2013, 23:10
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I am doing a port on the front of the box, below the midrange.
It will be a 14,3 cm (w) x 0,75 cm (h) opening and the port length is 9,8 cm.
It matches the size of the port volume and length suggested by WinISD.

I am building 1st Order But. Crossovers 6000Hz/12db. One inductor and one capacitor.
I am also following an article that deal with the piezo tweeter.
http://frugal-phile.com/piezo-XO.html

Over, DIYaudio, looks like people just walked away after seeing my car speakers.
I think they find it hopeless to work with it on this particular situation that they don't even bother replying.
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Arnold B. Kruege...
post Feb 14 2013, 14:54
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QUOTE (mzil @ Feb 13 2013, 11:34) *
QUOTE (Arnold B. Krueger @ Feb 13 2013, 10:33) *
QUOTE (mzil @ Feb 12 2013, 15:37) *
Car speakers are designed for cars.


Not so much. Car speakers are designed to work in certain spaces with enclosures that fit into available space.

Car speakers such as his, which sell for $2.15 in US dollars for TWO, are typically designed to have no specific "enclosure", at all, and work instead on the principal of infinite baffle, for example on a rear deck where the volume of air in the trunk is relatively vast [and immaterial to the driver's performance, it just needs to be isolated from the forward radiation to prevent bass cancellation] compared to the smaller ported or acoustic suspension box designs we might use in a home.


Most car speakers end up in the dash or the doors where the air volume is finite. The car trunk is usually reserved for the back volume of a subwoofer where again it is often not exactly infinite. It is not uncommon at all for there to be dedicated sealed volumes for car speakers.

http://a248.e.akamai.net/pix.crutchfield.c...SYS-o_spkr.jpeg
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krafty
post Feb 14 2013, 16:07
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Hey guys.

I have received a notice from the wood maker... He's done the box. I didn't even have the time to tell him to hold on and make a port in the front.

Original suggested port:

102mm Diameter circle with 98mm length OR
204mm˛ Square with 98mm length

No space on the front.

Can I make:

2 x 51mm diameter circles with 49mm length tubes on each back of enclosure pair ?

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mzil
post Feb 14 2013, 19:17
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QUOTE (Arnold B. Krueger @ Feb 14 2013, 09:54) *
Most car speakers end up in the dash or the doors where the air volume is finite.


Typical in-dash speakers optimistically work on the principle of infinite baffle, "free air", no dedicated, boxed volume of air that that act upon or "see". Designers would like to think the dash has no holes to allow the back wave from entering the cabin and canceling the front output, or in actual practice they act more like "open baffle". They are not ported nor acoustic suspension designs and there is no enclosed box structure hidden inside the dashboard; trust me. You do understand that the volume of air doesn't have to be literally infinite in order to call it an "infinite baffle design", right?

Although the volume of air in a car door is in a sense an enclosure, true, the volume of air in a typical, unmodified car door exceeds his inexpensive, 4-inch speaker's Vas, and therefore the speaker system would effectively act as an infinite baffle there as well, not acoustic suspension , nor ported. Building smaller volume enclosures into car doors for 4-inch drivers, such as his, is not common, at all, except possibly for some highly modified, competition level designs by the likes of your friend Richard Clark. Ask him.

If your knowledge of how car speakers are typically used is based on seeing his state-of-the-art, award winning work, you would have a poor understanding of how things are in the real world of consumer car audio, both factory level and typical after market upgrade level. [A field I worked in for many years, BTW.]

Subwoofers, usually trunk mounted, are the speakers in a car where one might more typically expect to see an average consumer make an enclosure/box design, sometimes using the entire trunk itself as the enclosure, such as ported or acoustic suspension, although subs are sometimes simply mounted as free air designs on the rear package tray, as well. When done this way the design is correctly called "infinite baffle", even though the volume of air is again, not infinite.

[I suspect the OP's 4 inch woofers would not work out very well as subwoofers, however, for either car or home.]

I have no idea why you included that picture of a car door speaker. If you were trying to make a point with it, please verbalize it.

This post has been edited by mzil: Feb 14 2013, 19:55
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Arnold B. Kruege...
post Feb 14 2013, 21:40
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QUOTE (mzil @ Feb 14 2013, 13:17) *
[I have no idea why you included that picture of a car door speaker. If you were trying to make a point with it, please verbalize it.


The closed mind could not see the built-in enclosures.
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mzil
post Feb 14 2013, 23:51
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QUOTE (Arnold B. Krueger @ Feb 14 2013, 09:54) *
Most car speakers end up in the dash or the doors where the air volume is finite. The car trunk is usually reserved for the back volume of a subwoofer where again it is often not exactly infinite. It is not uncommon at all for there to be dedicated sealed volumes for car speakers.

http://a248.e.akamai.net/pix.crutchfield.c...SYS-o_spkr.jpeg


QUOTE (Arnold B. Krueger @ Feb 14 2013, 16:40) *
QUOTE (mzil @ Feb 14 2013, 13:17) *
[I have no idea why you included that picture of a car door speaker. If you were trying to make a point with it, please verbalize it.


The closed mind could not see the built-in enclosures.



There is no built-in enclosure in that image, at all, just a speaker being held in front of a typical door cavity with a bracket.
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