This is a glossary of various types of enclosures that Nightmare Audio is capable of designing. There is a brief description beside each image. Keep in mind there are many ways to orient the drivers and ports in these enclosures. They do not need to appear strictly as shown.

A sealed enclosure is one of the simplest enclosures to design and build. It is characterised by a very gradual roll off, wide bandwidth, and low efficiency. They can be very small enclosures; they work great when space is at a premium. The response depends on the driver and the size of the enclosure. The 12dB/octave roll off of this box makes it a second order system

Ported enclosures are fairly simple enclosures to design and build. It is more efficient than the sealed box, but has a much steeper rolloff. They are typically medium sized boxes, larger than sealed for a given -3dB point but smaller than higher order enclosures (6th order bandpasses for example). The response depends on the driver, the volume of the enclosure, the port area and port length. The 12dB/octave roll off of the driver and 12dB/octave roll off of the port make this a 4th order system

This is a moderately difficult enclosure to design and build. It is more efficient than the sealed box within its passband. They are typically medium sized boxes, larger than sealed but smaller than higher order enclosures. Care must be taken to implement a method for removing the driver from the enclosure. The removable panel must be sealed tightly to avoid leaks. The response depends on the driver, the volume of the two chambers, the port area and port length. The vented chamber which acts as an acoustic low pass filter with a roll off is 12dB/octave. Combined with the driver having a high pass response with a roll off of 12dB/octave, the result is a bandpass with 12dB/octave slopes on either side. Thus this is a 4th order system. They are often thought of as one note wonders with terrible sound quality. All too often this is the case. However if designed properly they can have great sound quality. Because they roll off at a similar rate as cabin gain boosts, they can have a fairly flat in car response.

This is a fairly difficult enclosure to design and build. It is typically more efficient than the ported box or 4th order bandpass within its passband. To achieve this gain requires the enclosure to be larger. Care must be taken to implement a method for removing the driver from the enclosure. The removable panel must be sealed tightly to avoid leaks. The response depends on the driver, the volume of the two chambers, the port areas and port lengths. Each chamber is vented; they act as an acoustic high pass and an acoustic low pass each with a roll off of 12dB/octave. Combined with the driver having a high pass response with a roll off of 12dB/octave, the result is a bandpass with a 24dB/octave high pass and 12dB/octave low pass response. Thus this is a 6th order system. They are often thought of as one note wonders with terrible sound quality. All too often this is the case. However if designed properly they can have great sound quality. Because they have two ports and chambers, they can be tuned very precisely. They also have better control over excursion in their pass band than the lower order enclosures.

A fairly difficult enclosure to design and build. It is typically more efficient than the ported box or 4th order bandpass within its passband. To achieve this gain requires the enclosure to be larger. Care must be taken to implement a method for removing the driver from the enclosure. The removable panel must be sealed tightly to avoid leaks. The response depends on the driver, the volume of the two chambers, the port areas and port lengths. Each chamber is vented; they act as an acoustic high pass and an acoustic low pass each with a roll off of 12dB/octave. Combined with the driver having a high pass response with a roll off of 12dB/octave, the result is a bandpass with a 24dB/octave high pass and 12dB/octave low pass response. Thus this is a 6th order system. They are often thought of as one note wonders with terrible sound quality. Series tuned sixth order bandpasses usually exhibit several interesting behaviours. Firstly their lower -3dB point is often much lower than the lower tuning frequency. Secondly they often have a much deeper null between their peaks than a parallel sixth order bandpass. Also WinISD is not capable of modeling a series tuned 6th order bandpass.

A very difficult enclosure to design and build. There are not many programs that can model its response. It can be visualized as a parallel tuned 6th order that has been placed in a vented chamber. They can have very high gains, but in order to do so they must be very large. Care must be taken to implement a method for removing the driver from the enclosure. The removable panel must be sealed tightly to avoid leaks. The response depends on the driver, the volume of the three chambers, the port areas and port lengths. Each chamber is vented; they act as acoustic high pass and acoustic low pass filters. In this way there are 2 low pass and one high pass. Combined with the driver having a high pass response with a roll off of 12dB/octave, the result is a bandpass with a 24dB/octave high pass and 24dB/octave low pass response. Thus this is an 8th order system. Because they have many chambers and many tuning, they can be quite difficult to design. They have more ripples in their response than the lower order bandpasses.

This is similar to a ported box. It is often claimed to have the impact of a sealed box while still having the low end of a ported box. A DCR will have 3 impedance spikes instead of the one that a ported box out have. Below a certain frequency they box acts as one large volume, the middle port and partition acoustically vanish. Above this frequency the response becomes similar to if the box only had the one chamber and port. There are several rules of thumbs for calculating what the port lengths, areas and chamber volumes should be.

A quarter wave pipe operates fundamentally differently than ported enclosures. They are sometimes referred to as transmission lines; however I'll reserve that term for stuffed pipes. The quarter wave pipe has resonances at 1/4 wavelength, 3/4, ... (n+1)/4. This can lead to a somewhat peaky response. However since subwoofers in cars generally have only 1-2 octaves of bandwidth this is often not a problem. Unlike transmission lines, the rear wave is not dissipated as heat. This means it interacts with the front wave. Below tuning the quarter wave pipe will roll off at 24dB/octave.

A transmission line is a quarter wave pipe which has been lined with fiber. The purpose of this is to dissipate the rear wave as heat. This gives it a response similar to a sealed box, however there are no reflections through the cone. This gives it better sound quality than a sealed box.

More coming soon...

More coming soon...