# Sticky  Designed for sealed or ported...explained!



## 14642

*Re: Designed for sealed or ported*



captainscarlett said:


> I want to get into a bit of box building for the sake of a regaining some boot space. And as people seem to have a distinct disdain for prefab enclosures, i thought i'd start to do a bit of reading up to make sure I have at least a basic idea of what's going on.
> 
> 
> 
> Yet on another forum you get this advice, which seems contradict some of the suggestions for sealed or ported enclosures:
> 
> 
> 
> 
> So who or which advice do i believe? or am i looking at this wrong?
> 
> 
> So if I'm to take the above advice, this would be in a ported box ...
> 
> 
> 
> 
> The DD, of which I have all three enclosed subs, would be the biggest contender for a sealed box .. (but having a little experience of DD I wouldn't even try it)
> 
> 
> 
> 
> .... and this would have to be the biggest contender for a ported box and a sealed box wouldn't even get a look in!


they're both right and they're both wrong. 

Here's the deal...go get a cup of coffee...

The Qts of the speaker indicates the shape of the roll-off. A Qts of .707 is considered ideal for infinite baffle because provides the best compromise between low frequency extension and transient response. So, let's say you have a woofer and you want to build a sealed box. Let's also say you have a TARGET Qtc (total Q of the box and woofer) of .707 and your woofer has a Qts of .5

The box volume will be calculated to provide an "aid" to the speaker's suspension (makes the suspension stiffer) so that the Qtc will be raised to the target of .707. If the woofer has a very compliant suspension (low Q) then the box will have to contribute more restoring force, so it will have to be small. If the woofer has a stiff suspension (higher Q) then the box will have to contribute less restoring force, so it will have to be bigger. If the Qts of your woofer is higher than the target Qtc, then the target isn't achievable.

So, the Q of the woofer determines the volume of the box for a given target Qtc. The low frequency extension is determined by the woofer's resonance frequency, Fs. The Fs is also raised in the sealed box iin the same proportion as the increase in Qts to Qtc.

So, a woofer with a really low Qts and a low Fs is well suited to a small sealed box SO LONG AS THE VOICE COIL IS LONG. Sealed boxes require much more excursion from the speaker than vented boxes do. A woofer with a short coil is not well suited to a sealed box unless it will be driven with very low power.

A vented box is more complicated. It's a combination of a sealed box and an additional resonance. A low Q woofer designed for a sealed box will work just fine in a vented box, but the additional coil necessary for the sealed box will be wasted in the vented box and its mass makes for a less efficient system than a woofer with the same Q and less mass.

Anyway, the box volume for a vented box is calculated to provide a target response similar to the sealed box. Usually the volume is a bit bigger because we want a lower Qtc (which doesn't really exist in the vented arrangement, but we'll use it as an example). 

The port is basically a speaker that's designed to play loudly at one note. Its response is a peak. We design the port to have a response that compliments the response of the woofer. We hear the sum of the output of the woofer and the output of the port. If we increase the tuning frequency, we have an area where the port's response and the woofer's response have a small gap--that creates a peak in the response in those frequencies. If we move the port to a lower frequency, we have a dip in the frequencies in between. Usually, the resonance frequency is chosen to extend the low frequency response as low as possible while maintaining flat response. For small bookshelf-style home speakers, a little bump is often helpful in providing some additional bass. 

At the frequency where the box is tuned, the port plays, but the woofer hardly moves. This is because the acoustic impedance (pressure) inside the box is much higher. Yes, the pressure inside a ported box is HIGHER (at the tuned frequency) than in a sealed box. Below the frequency where the box is tuned, there is much LESS pressure than in a sealed box--hence the need for a subsonic filter. So, at the low frequencies where the box is tuned, the woofer doesn't move much, so we don't need a heavy long coil. That makes it easier to make a more efficient woofer, since we don't need so much moving mass.

OK, so what does all of this mean? 

1. If you're going to use lots of power and a sealed box, then you need a woofer with a long coil.

2. If you're going to use a vented box, a woofer with a shorter coil will be fine.

3. If you use a woofer designed for a small sealed box (low Q) in a vented box, the box volume requirement will be small and the port frequency requirement will be low. That means the port will be very long and the box will be difficult to build because the port will be difficult to fit in the box. 

4. If you use a woofer with a short coil, designed for a vented box, in a sealed box with high power, the woofer will run out of coil and you'll hear distortion. Because the condition that produces the distortion is symmetrical (coil leaves the gap in both directions), the distortion will be mostly odd-order, which sounds nasty. "Brap Brap Brap". 

So, what's the conclusion? 
Your power requirement and choice of box type determines whether a long coil (woofer with high Xmax) is necessary. Almost all woofers will work in a sealed or vented box, so long as the woofer's Qts is lower than your target Qtc. A woofer with a Qts higher than .707 will have a peak in its response NO MATTER WHAT KIND OF BOX YOU USE. The rest is a matter of compromising between box size, power required to hit a target SPL and required low frequency extension.

When you put the box in the car, the transfer function (car's frequency response) will be added to the response of the woofer. this will produce roughly a 12dB per octave increase in level as frequency is reduced starting at about 50 or 60 Hz, depending on the size of the car. A vented box will give you a big peak and a sealed box will not. If you have an EQ, then you can reduce the peak by reducing the power the amp has to provide at those frequencies. I think a vented box and EQ is always the best way to go, so long as you can afford the space and the EQ.


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## Iron Maiden

I would say very well put coming from a gentleman that works for a company, whose speakers can be found in most colesieums you would visit for a concert.(Simply look up).


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## sqshoestring

This can also help people understand how IB (infinite baffle) works, since it is generally a giant sealed. Though with IB you often have the option of going with more cone area to offset the use of lower xmax subs that can keep efficiency higher/distortions lower...since you only need mount them and not box them.


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## Married_Man

Is there a link to visit to determine what is considered a long voice coil for a given speaker diameter? Same with determining what is low or high for Q & Fs numbers?

I ask because I built a small sealed trunk corner fiberglass enclosure (~.6 to .7 cf) for a Pioneer TS-W259D4 sub before realizing I needed to consider all of this LOL...

It performs well except for punch. It's very weak in the bass drum punch area and I'm trying to nail down why. I still plan to fill it with some fiberglass insulation to see if that helps with any standing wave problems, but I'm curious if a different sub may fit the space better, ex JL Audio 10W3v3.

*TS-W259D4 Specs*
Free Air Resonance (Fs)	48.0 Hz
Electrical “Q” (Qes)	1.09
Mechanical “Q” (Qms)	11.64
Total Speaker “Q” (Qts)	1.00
Equivalent Compliance (Vas)	0.52 cu ft / 14.63 L
One-Way Linear Excursion (Xmax)*	0.47 in / 12.0 mm
Efficiency (1 W)**	92 dB SPL

*JL Audio 10W3v3 Specs*
Free Air Resonance (Fs)	32.97 Hz
Electrical “Q” (Qes)	0.533
Mechanical “Q” (Qms)	7.027
Total Speaker “Q” (Qts)	0.495
Equivalent Compliance (Vas)	1.136 cu ft / 32.17 L
One-Way Linear Excursion (Xmax)*	0.550 in / 14.0 mm
Efficiency (1 W / 1 m)**	85.37 dB SPL


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## mitchjr

So for a small sealed box you want a driver with a low Qts, low fs, and high xmax. Why does Fi offer a high Qts option on their Q subwoofers for a small sealed application? I'm just trying to get a better understanding of all of this.

And what does Fi change to achieve this?


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## Hanatsu

mitchjr said:


> So for a small sealed box you want a driver with a low Qts, low fs, and high xmax. Why does Fi offer a high Qts option on their Q subwoofers for a small sealed application? I'm just trying to get a better understanding of all of this.
> 
> And what does Fi change to achieve this?


The enclosure will raise Q, when we get beyond Qtc 0,8 there will be a response peak above -f3, the higher Q the higher the peak will be. Some might prefer the sound of such an enclosure but if you have a DSP you can EQ the peak out and get a more power efficient design. 

A high Q woofer generally have flatter response in IB configurations.

Sent from my Samsung Galaxy 3 via Tapatalk.


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## sqshoestring

You want to get confused, take a look at the Pioneer shallow subs' T/S specs.

Q is just where the sub is 'happy' at. Starts with Fs is where its tuned but the qts tells you how close to Fs it is happy. High qts will be happy down by Fs, so it will play (IB they are tested at) well low and naturally have more output higher...so it will be flatter IB. Lower qts means it will not be as happy down there, which leaves better response up higher so its weak on bass. Until you put it in a box and push the Q up, then it gets happy a little higher frequency down low than the IB sub did. But if your Fs was in the 20s it will be happy in the 30s which is ok in cars. The IB sub will be happy about 25 and up if Fs is 20.

The easiest way to see what is going on is to take some different drivers and model them. Even if you take an average sub and make up a fake TS with higher qts and lower, change the Fs, etc., then compare them all.


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## avanti1960

*Re: Designed for sealed or ported*



Andy Wehmeyer said:


> they're both right and they're both wrong.
> 
> Here's the deal...go get a cup of coffee...
> 
> The Qts of the speaker indicates the shape of the roll-off. A Qts of .707 is considered ideal for infinite baffle because provides the best compromise between low frequency extension and transient response. So, let's say you have a woofer and you want to build a sealed box. Let's also say you have a TARGET Qtc (total Q of the box and woofer) of .707 and your woofer has a Qts of .5
> 
> The box volume will be calculated to provide an "aid" to the speaker's suspension (makes the suspension stiffer) so that the Qtc will be raised to the target of .707. If the woofer has a very compliant suspension (low Q) then the box will have to contribute more restoring force, so it will have to be small. If the woofer has a stiff suspension (higher Q) then the box will have to contribute less restoring force, so it will have to be bigger. If the Qts of your woofer is higher than the target Qtc, then the target isn't achievable.
> 
> So, the Q of the woofer determines the volume of the box for a given target Qtc. The low frequency extension is determined by the woofer's resonance frequency, Fs. The Fs is also raised in the sealed box iin the same proportion as the increase in Qts to Qtc.
> 
> So, a woofer with a really low Qts and a low Fs is well suited to a small sealed box SO LONG AS THE VOICE COIL IS LONG. Sealed boxes require much more excursion from the speaker than vented boxes do. A woofer with a short coil is not well suited to a sealed box unless it will be driven with very low power.
> 
> A vented box is more complicated. It's a combination of a sealed box and an additional resonance. A low Q woofer designed for a sealed box will work just fine in a vented box, but the additional coil necessary for the sealed box will be wasted in the vented box and its mass makes for a less efficient system than a woofer with the same Q and less mass.
> 
> Anyway, the box volume for a vented box is calculated to provide a target response similar to the sealed box. Usually the volume is a bit bigger because we want a lower Qtc (which doesn't really exist in the vented arrangement, but we'll use it as an example).
> 
> The port is basically a speaker that's designed to play loudly at one note. Its response is a peak. We design the port to have a response that compliments the response of the woofer. We hear the sum of the output of the woofer and the output of the port. If we increase the tuning frequency, we have an area where the port's response and the woofer's response have a small gap--that creates a peak in the response in those frequencies. If we move the port to a lower frequency, we have a dip in the frequencies in between. Usually, the resonance frequency is chosen to extend the low frequency response as low as possible while maintaining flat response. For small bookshelf-style home speakers, a little bump is often helpful in providing some additional bass.
> 
> At the frequency where the box is tuned, the port plays, but the woofer hardly moves. This is because the acoustic impedance (pressure) inside the box is much higher. Yes, the pressure inside a ported box is HIGHER (at the tuned frequency) than in a sealed box. Below the frequency where the box is tuned, there is much LESS pressure than in a sealed box--hence the need for a subsonic filter. So, at the low frequencies where the box is tuned, the woofer doesn't move much, so we don't need a heavy long coil. That makes it easier to make a more efficient woofer, since we don't need so much moving mass.
> 
> OK, so what does all of this mean?
> 
> 1. If you're going to use lots of power and a sealed box, then you need a woofer with a long coil.
> 
> 2. If you're going to use a vented box, a woofer with a shorter coil will be fine.
> 
> 3. If you use a woofer designed for a small sealed box (low Q) in a vented box, the box volume requirement will be small and the port frequency requirement will be low. That means the port will be very long and the box will be difficult to build because the port will be difficult to fit in the box.
> 
> 4. If you use a woofer with a short coil, designed for a vented box, in a sealed box with high power, the woofer will run out of coil and you'll hear distortion. Because the condition that produces the distortion is symmetrical (coil leaves the gap in both directions), the distortion will be mostly odd-order, which sounds nasty. "Brap Brap Brap".
> 
> So, what's the conclusion?
> Your power requirement and choice of box type determines whether a long coil (woofer with high Xmax) is necessary. Almost all woofers will work in a sealed or vented box, so long as the woofer's Qts is lower than your target Qtc. A woofer with a Qts higher than .707 will have a peak in its response NO MATTER WHAT KIND OF BOX YOU USE. The rest is a matter of compromising between box size, power required to hit a target SPL and required low frequency extension.
> 
> When you put the box in the car, the transfer function (car's frequency response) will be added to the response of the woofer. this will produce roughly a 12dB per octave increase in level as frequency is reduced starting at about 50 or 60 Hz, depending on the size of the car. A vented box will give you a big peak and a sealed box will not. If you have an EQ, then you can reduce the peak by reducing the power the amp has to provide at those frequencies. I think a vented box and EQ is always the best way to go, so long as you can afford the space and the EQ.


So to quantify what a long voice coil looks like for a sealed enclosure- are we talking about the need for one of those rocket launcher looking subwoofers? e.g. with nearly as much mounting depth as the nominal size of the driver and with a 1-way excursion capability of 29mm for a 12" driver? 

Would it be safe to say a 12" driver with a 1-way xmax limit of 15mm would not qualify as "long"?


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## 14642

*Re: Designed for sealed or ported*



avanti1960 said:


> So to quantify what a long voice coil looks like for a sealed enclosure- are we talking about the need for one of those rocket launcher looking subwoofers? e.g. with nearly as much mounting depth as the nominal size of the driver and with a 1-way excursion capability of 29mm for a 12" driver?
> 
> Would it be safe to say a 12" driver with a 1-way xmax limit of 15mm would not qualify as "long"?


If you're using a 500-1000 watt amp, it's probably fine. If you're using some huge amp, then you'll probably want one of those rocket launcher-looking subs. 15mm is pretty long. 7mm is not.


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## ethelbritt

A sealed cabinet is considered a punchier, more accurate sound.


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## minbari

ethelbritt said:


> A sealed cabinet is considered a punchier, more accurate sound.


no its not. not anymore than an 8" sub is more punchy than a 15". this is a myth that has been disproved so many times its not funny.


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## sqnut

A sealed box always sounds cleaner......always


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## 14642

^^ No it doesn't. In fact, a vented box can be made to play with MUCH less distortion and MUCH more output.


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## mmiller

minbari said:


> no its not. not anymore than an 8" sub is more punchy than a 15". this is a myth that has been disproved so many times its not funny.


Ugg that misconception has been my biggest pet peeve in audio.....


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## Victor_inox

Andy Wehmeyer said:


> ^^ No it doesn't. In fact, a vented box can be made to play with MUCH less distortion and MUCH more output.


Listen to The Man God damn it. He is right on money with this one, I stopped using sealed at the age 18. I alway being able bass reflex (ported) if you prefer, sounds better then sealed even with "designed for sealed" drivers. I still have Klipschorns (sealed) and that is as far as I stretch my sealed collection. 
Sealed has one purpose - make the box smaller, everything else justified by that.


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## sqnut

Andy Wehmeyer said:


> ^^ No it doesn't. In fact, a vented box can be made to play with MUCH less distortion and MUCH more output.


I'm not talking about how it measures, but how it sounds. I spent 6 months trying to get a ported box sound like my 1.25 cuft box. Tried different box/ports, eq, timing etc etc. No go. Yes a ported is louder and yes it has lower measured 2nd order. My take is that some second order at the lower end adds warmth to the sound. 

Ported subs can also sound tight and punchy, that depends on the overall response. But the two do sound different. I'm just not qualified to say why.


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## troubleshootn

*Re: Designed for sealed or ported*



Andy Wehmeyer said:


> they're both right and they're both wrong.
> 
> Here's the deal...go get a cup of coffee...
> 
> The Qts of the speaker indicates the shape of the roll-off. A Qts of .707 is considered ideal for infinite baffle because provides the best compromise between low frequency extension and transient response. So, let's say you have a woofer and you want to build a sealed box. Let's also say you have a TARGET Qtc (total Q of the box and woofer) of .707 and your woofer has a Qts of .5
> 
> The box volume will be calculated to provide an "aid" to the speaker's suspension (makes the suspension stiffer) so that the Qtc will be raised to the target of .707. If the woofer has a very compliant suspension (low Q) then the box will have to contribute more restoring force, so it will have to be small. If the woofer has a stiff suspension (higher Q) then the box will have to contribute less restoring force, so it will have to be bigger. If the Qts of your woofer is higher than the target Qtc, then the target isn't achievable.
> 
> So, the Q of the woofer determines the volume of the box for a given target Qtc. The low frequency extension is determined by the woofer's resonance frequency, Fs. The Fs is also raised in the sealed box iin the same proportion as the increase in Qts to Qtc.
> 
> So, a woofer with a really low Qts and a low Fs is well suited to a small sealed box SO LONG AS THE VOICE COIL IS LONG. Sealed boxes require much more excursion from the speaker than vented boxes do. A woofer with a short coil is not well suited to a sealed box unless it will be driven with very low power.
> 
> A vented box is more complicated. It's a combination of a sealed box and an additional resonance. A low Q woofer designed for a sealed box will work just fine in a vented box, but the additional coil necessary for the sealed box will be wasted in the vented box and its mass makes for a less efficient system than a woofer with the same Q and less mass.
> 
> Anyway, the box volume for a vented box is calculated to provide a target response similar to the sealed box. Usually the volume is a bit bigger because we want a lower Qtc (which doesn't really exist in the vented arrangement, but we'll use it as an example).
> 
> The port is basically a speaker that's designed to play loudly at one note. Its response is a peak. We design the port to have a response that compliments the response of the woofer. We hear the sum of the output of the woofer and the output of the port. If we increase the tuning frequency, we have an area where the port's response and the woofer's response have a small gap--that creates a peak in the response in those frequencies. If we move the port to a lower frequency, we have a dip in the frequencies in between. Usually, the resonance frequency is chosen to extend the low frequency response as low as possible while maintaining flat response. For small bookshelf-style home speakers, a little bump is often helpful in providing some additional bass.
> 
> At the frequency where the box is tuned, the port plays, but the woofer hardly moves. This is because the acoustic impedance (pressure) inside the box is much higher. Yes, the pressure inside a ported box is HIGHER (at the tuned frequency) than in a sealed box. Below the frequency where the box is tuned, there is much LESS pressure than in a sealed box--hence the need for a subsonic filter. So, at the low frequencies where the box is tuned, the woofer doesn't move much, so we don't need a heavy long coil. That makes it easier to make a more efficient woofer, since we don't need so much moving mass.
> 
> OK, so what does all of this mean?
> 
> 1. If you're going to use lots of power and a sealed box, then you need a woofer with a long coil.
> 
> 2. If you're going to use a vented box, a woofer with a shorter coil will be fine.
> 
> 3. If you use a woofer designed for a small sealed box (low Q) in a vented box, the box volume requirement will be small and the port frequency requirement will be low. That means the port will be very long and the box will be difficult to build because the port will be difficult to fit in the box.
> 
> 4. If you use a woofer with a short coil, designed for a vented box, in a sealed box with high power, the woofer will run out of coil and you'll hear distortion. Because the condition that produces the distortion is symmetrical (coil leaves the gap in both directions), the distortion will be mostly odd-order, which sounds nasty. "Brap Brap Brap".
> 
> So, what's the conclusion?
> Your power requirement and choice of box type determines whether a long coil (woofer with high Xmax) is necessary. Almost all woofers will work in a sealed or vented box, so long as the woofer's Qts is lower than your target Qtc. A woofer with a Qts higher than .707 will have a peak in its response NO MATTER WHAT KIND OF BOX YOU USE. The rest is a matter of compromising between box size, power required to hit a target SPL and required low frequency extension.
> 
> When you put the box in the car, the transfer function (car's frequency response) will be added to the response of the woofer. this will produce roughly a 12dB per octave increase in level as frequency is reduced starting at about 50 or 60 Hz, depending on the size of the car. A vented box will give you a big peak and a sealed box will not. If you have an EQ, then you can reduce the peak by reducing the power the amp has to provide at those frequencies. I think a vented box and EQ is always the best way to go, so long as you can afford the space and the EQ.



Things that dictate low frequency response:


Environment - usually, a vehicle's transfer function offers a HUGE boost in the sub-bass region. Typically, a 20dB natural boost @ 16Hz. 

Enclosure - in a car, sealed will ALWAYS play lower than a vented enclosure. Typical sealed box woofers have no problem reaching down to 10Hz flat, in car. 

Driver: Fs is NOT a huge determiner of LFE. Qt is. The higher the Q, the lower the woofer will play - always. The more moving mass, the lower the driver will play (relative to Q). Less BL product (relative to Q). Etc etc etc. 

Excursion - will my driver have the ability to move enough air to play that low? Remember, in a sealed environment, or IB (etc), the lower the speaker plays, the more excursion is needed.


Cms, or compliance usually has VERY little to do with how low a speaker will play. Now, keep in mind, that the lower the Fs of a driver is, the lower the Q is - and remember, a high Q always plays lower. So, a low resonance speaker isn't always good. 


There is NO way to look at driver specs, to know how low a driver will play. You can get a good idea by looking at the Q. But, the BIGGEST factor of LFE, is environment. And, unless you map your transfer function of your vehicle, you cannot say that X driver will play down to Y. 

Would you agree with this statement?


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## Sine Swept

Andy I found it interesting that you said that the pressure inside the box is the greatest near the tuning frequency while at the same time the driver hardly moves. I have watched a CRX with a single 12 in a sonotube w/ port firing rear do +150db and to me it appeared that the speaker was hardly moving. I could never understand how a speaker that hardly moved could be so devastating.


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## 14642

*Re: Designed for sealed or ported*



troubleshootn said:


> Things that dictate low frequency response:
> 
> 
> Environment - usually, a vehicle's transfer function offers a HUGE boost in the sub-bass region. Typically, a 20dB natural boost @ 16Hz.
> 
> Enclosure - in a car, sealed will ALWAYS play lower than a vented enclosure. Typical sealed box woofers have no problem reaching down to 10Hz flat, in car.
> 
> Driver: Fs is NOT a huge determiner of LFE. Qt is. The higher the Q, the lower the woofer will play - always. The more moving mass, the lower the driver will play (relative to Q). Less BL product (relative to Q). Etc etc etc.
> 
> Excursion - will my driver have the ability to move enough air to play that low? Remember, in a sealed environment, or IB (etc), the lower the speaker plays, the more excursion is needed.
> 
> 
> Cms, or compliance usually has VERY little to do with how low a speaker will play. Now, keep in mind, that the lower the Fs of a driver is, the lower the Q is - and remember, a high Q always plays lower. So, a low resonance speaker isn't always good.
> 
> 
> There is NO way to look at driver specs, to know how low a driver will play. You can get a good idea by looking at the Q. But, the BIGGEST factor of LFE, is environment. And, unless you map your transfer function of your vehicle, you cannot say that X driver will play down to Y.
> 
> Would you agree with this statement?


No, I don't agree with that. The car is a constant and it boosts bass as frequency decreases. If X woofer will play Y frequency, it'll play Y frequency louder in the car than out of the car.


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## 14642

Sine Swept said:


> Andy I found it interesting that you said that the pressure inside the box is the greatest near the tuning frequency while at the same time the driver hardly moves. I have watched a CRX with a single 12 in a sonotube w/ port firing rear do +150db and to me it appeared that the speaker was hardly moving. I could never understand how a speaker that hardly moved could be so devastating.


Because at that frequency, most of the sound comes from a port. 

Think about swimming vs. flying. You can flap your arms all you want and you won't fly very far. Jump in the pool and flap your arms and you can swim pretty easily. The water provides greater resistance to the motion of your arms. The port in the box works the same way. It increases the acoustical impedance.


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## seafish

subbed for info.


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## 3sevenmafia

So how will it impact sound if it is a sealed enclosure in a sealed trunk vs an open back enclosure in a sealed trunk. will it work in a similar way or is the trunk just a bass chamber?


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## oabeieo

So when looking for an IB sub , the qts of the sub will be the qtc. 
So IB subs look for QtC between .5 and .7 
Obviously a trunk may raise q a bit so large vas numbers on sub help keep that number close to qts. 

Awesome sticky btw. Well explained


Andy, 
Would you care to elaborate on damping and it’s effects on transients below .707
It’s tough to explain and think your eloquence would add nicely to this sticky. 

Thanks in advance


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## Elektra

*Re: Designed for sealed or ported*



Andy Wehmeyer said:


> they're both right and they're both wrong.
> 
> Here's the deal...go get a cup of coffee...
> 
> The Qts of the speaker indicates the shape of the roll-off. A Qts of .707 is considered ideal for infinite baffle because provides the best compromise between low frequency extension and transient response. So, let's say you have a woofer and you want to build a sealed box. Let's also say you have a TARGET Qtc (total Q of the box and woofer) of .707 and your woofer has a Qts of .5
> 
> The box volume will be calculated to provide an "aid" to the speaker's suspension (makes the suspension stiffer) so that the Qtc will be raised to the target of .707. If the woofer has a very compliant suspension (low Q) then the box will have to contribute more restoring force, so it will have to be small. If the woofer has a stiff suspension (higher Q) then the box will have to contribute less restoring force, so it will have to be bigger. If the Qts of your woofer is higher than the target Qtc, then the target isn't achievable.
> 
> So, the Q of the woofer determines the volume of the box for a given target Qtc. The low frequency extension is determined by the woofer's resonance frequency, Fs. The Fs is also raised in the sealed box iin the same proportion as the increase in Qts to Qtc.
> 
> So, a woofer with a really low Qts and a low Fs is well suited to a small sealed box SO LONG AS THE VOICE COIL IS LONG. Sealed boxes require much more excursion from the speaker than vented boxes do. A woofer with a short coil is not well suited to a sealed box unless it will be driven with very low power.
> 
> A vented box is more complicated. It's a combination of a sealed box and an additional resonance. A low Q woofer designed for a sealed box will work just fine in a vented box, but the additional coil necessary for the sealed box will be wasted in the vented box and its mass makes for a less efficient system than a woofer with the same Q and less mass.
> 
> Anyway, the box volume for a vented box is calculated to provide a target response similar to the sealed box. Usually the volume is a bit bigger because we want a lower Qtc (which doesn't really exist in the vented arrangement, but we'll use it as an example).
> 
> The port is basically a speaker that's designed to play loudly at one note. Its response is a peak. We design the port to have a response that compliments the response of the woofer. We hear the sum of the output of the woofer and the output of the port. If we increase the tuning frequency, we have an area where the port's response and the woofer's response have a small gap--that creates a peak in the response in those frequencies. If we move the port to a lower frequency, we have a dip in the frequencies in between. Usually, the resonance frequency is chosen to extend the low frequency response as low as possible while maintaining flat response. For small bookshelf-style home speakers, a little bump is often helpful in providing some additional bass.
> 
> At the frequency where the box is tuned, the port plays, but the woofer hardly moves. This is because the acoustic impedance (pressure) inside the box is much higher. Yes, the pressure inside a ported box is HIGHER (at the tuned frequency) than in a sealed box. Below the frequency where the box is tuned, there is much LESS pressure than in a sealed box--hence the need for a subsonic filter. So, at the low frequencies where the box is tuned, the woofer doesn't move much, so we don't need a heavy long coil. That makes it easier to make a more efficient woofer, since we don't need so much moving mass.
> 
> OK, so what does all of this mean?
> 
> 1. If you're going to use lots of power and a sealed box, then you need a woofer with a long coil.
> 
> 2. If you're going to use a vented box, a woofer with a shorter coil will be fine.
> 
> 3. If you use a woofer designed for a small sealed box (low Q) in a vented box, the box volume requirement will be small and the port frequency requirement will be low. That means the port will be very long and the box will be difficult to build because the port will be difficult to fit in the box.
> 
> 4. If you use a woofer with a short coil, designed for a vented box, in a sealed box with high power, the woofer will run out of coil and you'll hear distortion. Because the condition that produces the distortion is symmetrical (coil leaves the gap in both directions), the distortion will be mostly odd-order, which sounds nasty. "Brap Brap Brap".
> 
> So, what's the conclusion?
> Your power requirement and choice of box type determines whether a long coil (woofer with high Xmax) is necessary. Almost all woofers will work in a sealed or vented box, so long as the woofer's Qts is lower than your target Qtc. A woofer with a Qts higher than .707 will have a peak in its response NO MATTER WHAT KIND OF BOX YOU USE. The rest is a matter of compromising between box size, power required to hit a target SPL and required low frequency extension.
> 
> When you put the box in the car, the transfer function (car's frequency response) will be added to the response of the woofer. this will produce roughly a 12dB per octave increase in level as frequency is reduced starting at about 50 or 60 Hz, depending on the size of the car. A vented box will give you a big peak and a sealed box will not. If you have an EQ, then you can reduce the peak by reducing the power the amp has to provide at those frequencies. I think a vented box and EQ is always the best way to go, so long as you can afford the space and the EQ.




Thanks Andy very informative as always...

Can you summarize the key points for people not as clued up as you are...

Such as what is considered a very low QTS and what’s considered to be a high Xmas and what’s considered a low FS? 

So essentially some sort of guide for sealed and ported based on numbers 

Thanks Andy


Sent from my iPhone using Tapatalk


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## SkizeR

guys, andy doesnt come around here anymore


----------



## 04quadcab

SkizeR said:


> guys, andy doesnt come around here anymore


To busy selling some of the best speakers on the market.


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## Rwhite90

So I guess no one else can answer? I'm looking for a sub and cabinet combo for possibly 2 15's in the back of a f150 super crew. Space not an issue, took the backseats out. But over a decade ago I had a digital design 2500 on a 1000 watt zx kicker in a Chevy S10 extended cab and I cannot find that kind of sound/flex/low frequency range again for the life of me. I was young and wasn't too educated just yet so all I know about the box was that it had a port lol no idea if it was labyrinth, cornered, ordered, bandpass, horn, baffle or any of that and I'm regretting it these days


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## Rwhite90

And now that I'm thinking about it I don't even know what coil size the sub was haha


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## Greggy G

I have the JL 10w6v3 sub in the JL HO box set up, .75cu and 39hz. It's great but I want to get a different box made due to the shape of the JL box. I think it sounds better rear firing in my trunk but it's long and sticks out into the rest of the trunk. If I buy a stage 3 quality box from sonix enclosures, I can get the shape I want. I'm stuck though because they can make the box 1.0cu and tune to whatever I want essentially. But I can't figure out what's best for this sub. I'm very happy with it as is but I don't need "high output", I want the quality sound quality and accuracy. Any thoughts on that box set up and those options? Thank you


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## oabeieo

Greggy G said:


> I have the JL 10w6v3 sub in the JL HO box set up, .75cu and 39hz. It's great but I want to get a different box made due to the shape of the JL box. I think it sounds better rear firing in my trunk but it's long and sticks out into the rest of the trunk. If I buy a stage 3 quality box from sonix enclosures, I can get the shape I want. I'm stuck though because they can make the box 1.0cu and tune to whatever I want essentially. But I can't figure out what's best for this sub. I'm very happy with it as is but I don't need "high output", I want the quality sound quality and accuracy. Any thoughts on that box set up and those options? Thank you


1st off; contrary to what god says , ported boxes have gobs of group delay and if you want accuracy, go sealed or IB , and don’t use W7s (unless you like almost zero output).

in sealed you need 2 subs to put out the same output as 1.... go figure.

So either do a BIG sealed single sub or a pair of 12s sealed.... bass will be everything you want (with proper eq)

OR you can EQ a ported box and have mediocre bass that sounds good , lacks transient response, has excessive GD but gobs of output with a single sub

I mean , you bought a w7 , why not go big volume ported and have tons and tons of shyttie sounding bass that has so much delay on the port that it might as well be two or three cars back.


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## Lou Frasier2

you ok?I dont recall seeing you post a response like this before


----------



## Grinder

oabeieo said:


> 1st off; contrary to what god says , ported boxes have gobs of group delay and if you want accuracy, go sealed or IB , and don’t use W7s (unless you like almost zero output).
> 
> in sealed you need 2 subs to put out the same output as 1.... go figure.
> 
> So either do a BIG sealed single sub or a pair of 12s sealed.... bass will be everything you want (with proper eq)
> 
> OR you can EQ a ported box and have mediocre bass that sounds good , lacks transient response, has excessive GD but gobs of output with a single sub
> 
> I mean , you bought a w7 , why not go big volume ported and have tons and tons of shyttie sounding bass that has so much delay on the port that it might as well be two or three cars back.


Would you care to define "gobs" of group delay? I mean, it's not as though all ported boxes are the same in this regard.

Have you heard of the "40/400" rule of thumb? Multiply group delay (m/s) by frequency (Hz), and a sum of 400 or less at anything over 40 Hz is okay (and as group delay cannot be heard at or below 40 Hz, any sum at or below 40 Hz is okay). I don't recall where I read this, but I am under the impression that it is a good rule of thumb. If I am mistaken, I would very much like to know.


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## Pooladdict247

Ported boxes sound just as good as sealed, if built properly. I don’t buy that nonsense that sealed is superior to ported. Ya sealed has more room for error design wise vs a ported and that’s why most choose sealed. Because a poorly designed sealed box will sound better than a poorly designed ported. I used to be a sealed/bandpass snob myself since buying prefab ported boxes that always seemed to lack. Built my first SQ ported box vs buying a generic “off the shelf” ported box and it was amazing. Also I’ve had custom made sealed boxes for that specific driver that sounded amazing, but still ported wins all day every day IMO if built right. At the end of the day it’s not a matter of sealed vs ported, but more of a what driver is better suited for sealed or ported and put in a _proper_ built box. You can have the most badass sub in the world but if you have a garbage box it gonna sound like garbage. Box design is just as important as the sub itself! Currently I’m rocking a 10” rear deck mounted trunk baffle which some consider IB but it’s not really IB because the trunk is the baffle. It sounds amazing off stock amp! Can’t wait until the helix dsp takes over to see the results. Anyways I chose the driver (kicker compVR) due to it’s high QTS. My trunk volume is 12.5 cu ft vs 3.0 cu ft max sealed that the driver calls for. More than 4x spec, but it sounds great, on a stock amp. Sure I could wall off the area to meet the drivers spec but why bother if it sounds good? Don’t get lost in the weeds fellas, trust your ears.
Edit: here’s its qts


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## oabeieo

Grinder said:


> Would you care to define "gobs" of group delay? I mean, it's not as though all ported boxes are the same in this regard.
> 
> Have you heard of the "40/400" rule of thumb? Multiply group delay (m/s) by frequency (Hz), and a sum of 400 or less at anything over 40 Hz is okay (and as group delay cannot be heard at or below 40 Hz, any sum at or below 40 Hz is okay). I don't recall where I read this, but I am under the impression that it is a good rule of thumb. If I am mistaken, I would very much like to know.


You can absolutely hear every ms 
and there is no “rule “ that’s the silliest thing I’ve ever heard 

do this , go listen to your sub and midbass , the fs of the midbass will give your sub away, so it makes this test super obvious

put 1ms on midbass and listen with sub tell me you don’t hear any difference..... it’s ginormous! Put 2 or 3 ms , it’s completely different sound

now that port adds 30ms...... Jesus !


----------



## Grinder

oabeieo said:


> You can absolutely hear every ms
> and there is no “rule “ that’s the silliest thing I’ve ever heard
> 
> do this , go listen to your sub and midbass , the fs of the midbass will give your sub away, so it makes this test super obvious
> 
> put 1ms on midbass and listen with sub tell me you don’t hear any difference..... it’s ginormous! Put 2 or 3 ms , it’s completely different sound
> 
> now that port adds 30ms...... Jesus !


----------



## oabeieo

Lou Frasier2 said:


> you ok?I dont recall seeing you post a response like this before


lol ..... sorry.... it was a little bit itchy now that I read it again.....

I just remember seeing somewhere in this thread someone was saying ported boxes with eq was superior..... and it’s just not. Lol


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## oabeieo

Grinder said:


>


Lmao 😁


----------



## oabeieo

Lou Frasier2 said:


> you ok?I dont recall seeing you post a response like this before


lol .....


Pooladdict247 said:


> Ported boxes sound just as good as sealed, if built properly. I don’t buy that nonsense that sealed is superior to ported. Ya sealed has more room for error design wise vs a ported and that’s why most choose sealed. Because a poorly designed sealed box will sound better than a poorly designed ported. I used to be a sealed/bandpass snob myself since buying prefab ported boxes that always seemed to lack. Built my first SQ ported box vs buying a generic “off the shelf” ported box and it was amazing. Also I’ve had custom made sealed boxes for that specific driver that sounded amazing, but still ported wins all day every day IMO if built right. At the end of the day it’s not a matter of sealed vs ported, but more of a what driver is better suited for sealed or ported and put in a _proper_ built box. You can have the most badass sub in the world but if you have a garbage box it gonna sound like garbage. Box design is just as important as the sub itself! Currently I’m rocking a 10” rear deck mounted trunk baffle which some consider IB but it’s not really IB because the trunk is the baffle. It sounds amazing off stock amp! Can’t wait until the helix dsp takes over to see the results. Anyways I chose the driver (kicker compVR) due to it’s high QTS. My trunk volume is 12.5 cu ft vs 3.0 cu ft max sealed that the driver calls for. More than 4x spec, but it sounds great, on a stock amp. Sure I could wall off the area to meet the drivers spec but why bother if it sounds good? Don’t get lost in the weeds fellas, trust your ears.
> Edit: here’s its qts
> View attachment 314301


you’ll learn something today , starting with , no there not. Sound quality is at its best when the system can faithfully reproduce the recording.

that starts with a flat frequency domain and a time domain that rises quickly and has very little “lag”

a port tuned at 35hz , the port needs to be somewhat in phase with the front of the speaker to work “properly “.

so a “proper” built ported box with a port tuned at 35hz. 35hz wavelength is ...... 32.2286 feet long (40°C : 1128 ft/sec) , the port is typically 90deg (1:4 wave) so that’s a GD equal to 8.05feet long.... and that’s a very very low theoretical number.... in reality, the GD is 20-30ms......

So if the sun bass starts dragging 8-30ms that’s not a faithful representation..... with proper EQ to make the response flat, and kill all the gain from port, eq will also fix phase , so it becomes closer to that 8ms number..... but it’s still 8ms out of time with that front of the speaker, and you hear both....

A sealed box has a constant GD that is in step and follows the shape of its natural roll off..... stick it in a car with cabin gain and it should play to DC mostly flat...

Once eq is applied, when it comes to group delay... guess what ...

Any residual group delay would be constant which means it could be removed using simple time delay.. as The back of the speaker is not interfering with the front of the speaker


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## 156546

No, group delay is not a very important aspect of subwoofer performance--or any performance--unless it's REALLY high. Vented boxes aren't "sloppy" because of group delay. If they're sloppy, it's because they are tuned too high and that means they're poorly designed for accurately reproducing music but likely optimized for playing as loudly as they can be made to play over a narrow band of frequencies. 

If we were so concerned about group delay, we'd also have to rule out crossovers. LOL


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## Grinder

How would you define or quantify "REALLY high" group delay?

Any thoughts on this:?


Grinder said:


> .... Have you heard of the "40/400" rule of thumb? Multiply group delay (m/s) by frequency (Hz), and a sum of 400 or less at anything over 40 Hz is okay (and as group delay cannot be heard at or below 40 Hz, any sum at or below 40 Hz is okay). I don't recall where I read this, but I am under the impression that it is a good rule of thumb. If I am mistaken, I would very much like to know.


----------



## 156546

Grinder said:


> How would you define or quantify "REALLY high" group delay?
> 
> Any thoughts on this:?


In excess of something like 50mS at low frequencies maybe. Group delay is the derivative of phase vs frequency. So, for any filter, the steeper the filter slope the greater the phase shift and therefore, the greater the group delay. The higher group delay of the vented box is because of the steeper rolloff. But this happens at the bottom of the frequency response. 50mS is about 1 cycle at 20Hz. This is not going to destroy ANYTHING. Being concerned about group delay in any kind of a normal system is being really lost in the technical weeds


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## Elektra

Andy Wehmeyer said:


> *Re: Designed for sealed or ported*
> 
> 
> 
> they're both right and they're both wrong.
> 
> Here's the deal...go get a cup of coffee...
> 
> The Qts of the speaker indicates the shape of the roll-off. A Qts of .707 is considered ideal for infinite baffle because provides the best compromise between low frequency extension and transient response. So, let's say you have a woofer and you want to build a sealed box. Let's also say you have a TARGET Qtc (total Q of the box and woofer) of .707 and your woofer has a Qts of .5
> 
> The box volume will be calculated to provide an "aid" to the speaker's suspension (makes the suspension stiffer) so that the Qtc will be raised to the target of .707. If the woofer has a very compliant suspension (low Q) then the box will have to contribute more restoring force, so it will have to be small. If the woofer has a stiff suspension (higher Q) then the box will have to contribute less restoring force, so it will have to be bigger. If the Qts of your woofer is higher than the target Qtc, then the target isn't achievable.
> 
> So, the Q of the woofer determines the volume of the box for a given target Qtc. The low frequency extension is determined by the woofer's resonance frequency, Fs. The Fs is also raised in the sealed box iin the same proportion as the increase in Qts to Qtc.
> 
> So, a woofer with a really low Qts and a low Fs is well suited to a small sealed box SO LONG AS THE VOICE COIL IS LONG. Sealed boxes require much more excursion from the speaker than vented boxes do. A woofer with a short coil is not well suited to a sealed box unless it will be driven with very low power.
> 
> A vented box is more complicated. It's a combination of a sealed box and an additional resonance. A low Q woofer designed for a sealed box will work just fine in a vented box, but the additional coil necessary for the sealed box will be wasted in the vented box and its mass makes for a less efficient system than a woofer with the same Q and less mass.
> 
> Anyway, the box volume for a vented box is calculated to provide a target response similar to the sealed box. Usually the volume is a bit bigger because we want a lower Qtc (which doesn't really exist in the vented arrangement, but we'll use it as an example).
> 
> The port is basically a speaker that's designed to play loudly at one note. Its response is a peak. We design the port to have a response that compliments the response of the woofer. We hear the sum of the output of the woofer and the output of the port. If we increase the tuning frequency, we have an area where the port's response and the woofer's response have a small gap--that creates a peak in the response in those frequencies. If we move the port to a lower frequency, we have a dip in the frequencies in between. Usually, the resonance frequency is chosen to extend the low frequency response as low as possible while maintaining flat response. For small bookshelf-style home speakers, a little bump is often helpful in providing some additional bass.
> 
> At the frequency where the box is tuned, the port plays, but the woofer hardly moves. This is because the acoustic impedance (pressure) inside the box is much higher. Yes, the pressure inside a ported box is HIGHER (at the tuned frequency) than in a sealed box. Below the frequency where the box is tuned, there is much LESS pressure than in a sealed box--hence the need for a subsonic filter. So, at the low frequencies where the box is tuned, the woofer doesn't move much, so we don't need a heavy long coil. That makes it easier to make a more efficient woofer, since we don't need so much moving mass.
> 
> OK, so what does all of this mean?
> 
> 1. If you're going to use lots of power and a sealed box, then you need a woofer with a long coil.
> 
> 2. If you're going to use a vented box, a woofer with a shorter coil will be fine.
> 
> 3. If you use a woofer designed for a small sealed box (low Q) in a vented box, the box volume requirement will be small and the port frequency requirement will be low. That means the port will be very long and the box will be difficult to build because the port will be difficult to fit in the box.
> 
> 4. If you use a woofer with a short coil, designed for a vented box, in a sealed box with high power, the woofer will run out of coil and you'll hear distortion. Because the condition that produces the distortion is symmetrical (coil leaves the gap in both directions), the distortion will be mostly odd-order, which sounds nasty. "Brap Brap Brap".
> 
> So, what's the conclusion?
> Your power requirement and choice of box type determines whether a long coil (woofer with high Xmax) is necessary. Almost all woofers will work in a sealed or vented box, so long as the woofer's Qts is lower than your target Qtc. A woofer with a Qts higher than .707 will have a peak in its response NO MATTER WHAT KIND OF BOX YOU USE. The rest is a matter of compromising between box size, power required to hit a target SPL and required low frequency extension.
> 
> When you put the box in the car, the transfer function (car's frequency response) will be added to the response of the woofer. this will produce roughly a 12dB per octave increase in level as frequency is reduced starting at about 50 or 60 Hz, depending on the size of the car. A vented box will give you a big peak and a sealed box will not. If you have an EQ, then you can reduce the peak by reducing the power the amp has to provide at those frequencies. I think a vented box and EQ is always the best way to go, so long as you can afford the space and the EQ.


What is considered a high QTS 0.7? Wouldn’t that driver be more suited to a IB situation as the box would need to be huge to keep the driver under 0.8ish? 


Sent from my iPhone using Tapatalk


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## oabeieo

GotFrogs said:


> No, group delay is not a very important aspect of subwoofer performance--or any performance--unless it's REALLY high. Vented boxes aren't "sloppy" because of group delay. If they're sloppy, it's because they are tuned too high and that means they're poorly designed for accurately reproducing music but likely optimized for playing as loudly as they can be made to play over a narrow band of frequencies.
> 
> If we were so concerned about group delay, we'd also have to rule out crossovers. LOL


now that is very precise and actually should be it’s own discussion. So for one I apologize for that reply, I suppose it was aimed at 30 to 40 Hz tuning and “manufacturer suggestion” designs. 

tuned too high….. yes…. For example winISD will do a recommendation for a lot of subs with gobs of volume and tuned below fs , in to low 20s and I’ve even seen one at 15hz.

I looked at all the parameters on a lot of those recommendations from the software and to my surprise you are actually correct the fees shift is very minimal, group delay is some might say pushed below the music, but the overall response and vent velocity was favorable.

so what do one do in a case like that you just build really big boxes for 8 inch subwoofers for cars? At least in the cases where box of volume needs to be big to reasonably get the port to reasonably fit in the box and the box to reasonably fit in a trunk…

But you’re exactly right, most of us installers are tuning in the 30s because output is the main goal of the system, and or someone simply doesn’t know any better..

Well said , I appreciate that response that helps us a lot


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## oabeieo

GotFrogs said:


> In excess of something like 50mS at low frequencies maybe. Group delay is the derivative of phase vs frequency. So, for any filter, the steeper the filter slope the greater the phase shift and therefore, the greater the group delay. The higher group delay of the vented box is because of the steeper rolloff. But this happens at the bottom of the frequency response. 50mS is about 1 cycle at 20Hz. This is not going to destroy ANYTHING. Being concerned about group delay in any kind of a normal system is being really lost in the technical weeds


In agreement, again, in my demo room I have Jl Audio 10 W7 and 5 ft.³ box with a 4 inch port tuned @ 18 Hz. Group delay is very low, and for a port alignment it has an excellent degree of sound quality, and boy does that thing boogie. And the responses ruler flat to 20 hz

but it does come out the cost of a little bit of efficiency in the 40s and 50s, but who cares right it sound quality where after… and for that subwoofer compared to its sealed alignment the port alignment is favorable. although I do agree with you on this point, I still do believe there are a lot of subwoofers that just belong in sealed boxes period. (Lol)

anyways , again, thank you for clarifying and making the distinction


----------



## oabeieo

So gang….. andy said something in a post that needs to be understood..

he said “the steeper the slope the more the group delay” (or something to that effect)

so keep in mind, there’s also besides the GD from the port, there’s a constant GD that is indicative of the frequency the crossover is set up and the shape of the slope or steepness.

the lower the frequency, the more GD the crossover produces.

the low pass of a crossover is lagging, that means the low pass is literally delayed, by many ms. When the roll off of the crossover on the low pass is in its attenuation, it eventually intersects.

that intersection between the low and high pass is where there at a constant slope, so both slopes “ideally” interact together to be 180deg from eachother at the crossover. Or 90 deg for quadratic crossovers. The sum of the crossovers make 0/90 degrees. Depending on filter topology of course

OK great and dandy but where is that phase shift coming from….. the filter.

not talking about stop bands, but the actual pass band of the low pass, it is many ms out of time with the pass band of the high pass!!!!

thats the point, the goal of a crossover is to have “all pass performance” as far as phase shift.

the end result is the low pass must have inherent delay so that they can sum properly during the stop band. And this is all math and stuff that’s a different topic. But in any minimum phase crossover, the low pass and high pass are many ms. apart.

you can use signal delay and delay the high pass to be in time with the low pass, but doing that will change the timing on the crossover area, which would be subsequently detrimental to the phase tracking characteristics of the allpass intended in the crossover design.

so there you have it that is what he means by group delay in the crossover. You can buy dsps that have fir filters that make the crossovers have linear phase and no group delay, but it comes at the cost of total output delay. Which makes it hard to sync with video. (Who cares where driving cars!, listening to music) 50 to 100 ms of constant delay is absolutely nothing when there’s no video to sync to. Minimum phase crossovers sound good. Linear phase crossovers sound good too. But the phase shift that makes it a noticeable difference I’m sorry to say it’s only in the low frequencies. You really can’t tell too much the all pass of a 3000hz crossover. It’s inaudible. At 80 Hz it’s very very audible. So much so it literally ruins and smears the time domain so incredibly badly, it’s absolutely unrepairable in all aspects in your completely lying to yourself if you think your minimum phase 80 hurts crossover sounds good. It may have good characteristics as far as resonating with the room in a positive sounding fashion. But then subs in the midbass are way way badly out of time with each other. It’s sad actually how poorly minimum phase crossovers maintain any degree of fidelity to the original signal.

anyway my original point was, in a subwoofer system there’s crossover group delay, and then there’s group delay caused by the port. The total of those two can be a disaster in the time domain.


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## 156546

Group delay is not something to worry about.


----------



## techila

Rwhite90 said:


> So I guess no one else can answer? I'm looking for a sub and cabinet combo for possibly 2 15's in the back of a f150 super crew. Space not an issue, took the backseats out. But over a decade ago I had a digital design 2500 on a 1000 watt zx kicker in a Chevy S10 extended cab and I cannot find that kind of sound/flex/low frequency range again for the life of me. I was young and wasn't too educated just yet so all I know about the box was that it had a port lol no idea if it was labyrinth, cornered, ordered, bandpass, horn, baffle or any of that and I'm regretting it these days


As harsh as it may sound, but age also is a factor in how well we can hear certain frequencies .. and hearing very loud sounds over years can also result in lesser sensitivity to certain sounds. I am 48 and I can't hear high frequencies that by 14 year old son can.


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## ckirocz28

techila said:


> As harsh as it may sound, but age also is a factor in how well we can hear certain frequencies .. and hearing very loud sounds over years can also result in lesser sensitivity to certain sounds. I am 48 and I can't hear high frequencies that by 14 year old son can.


Why can't young people hear common sense?


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## Lineman26

All good info me and my buddy should have had back in 1992 when he bought a MTX Eliminator 15” sub that I built a tiny wedge box for to fit in the back of his 1976 VW Beetle convertible. And yes, the MTX Eliminator was a free-air sub… Basically the exact opposite of what he needed. When we somehow finished the deck and amp install and hooked up my first of what would eventually be over 1000 “custom built” boxes, not surprisingly we were confused as to why it had good high bass punch but nothing below say 60hz. We decided maybe it needed to be ported, so I grabbed the largest drill bit on hand, and popped about 15 1/2” holes in the top of the box. Hearing no improvement, duct tape covered our failed ports, but that 15”midbass sub continued to bump in his beetle for a couple years, while I quickly figured out the right way to do things and had a pair of Kicker Comp 15’s in my 85 5.0 Mustang sounding good and loud running off a Punch 200ix amp.


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## Lineman26

Rwhite90 said:


> So I guess no one else can answer? I'm looking for a sub and cabinet combo for possibly 2 15's in the back of a f150 super crew. Space not an issue, took the backseats out. But over a decade ago I had a digital design 2500 on a 1000 watt zx kicker in a Chevy S10 extended cab and I cannot find that kind of sound/flex/low frequency range again for the life of me. I was young and wasn't too educated just yet so all I know about the box was that it had a port lol no idea if it was labyrinth, cornered, ordered, bandpass, horn, baffle or any of that and I'm regretting it these days


depending on your budget, there are many options. If you wan my powerful low note output, you probably will want a ported box tuned between 30 and 34hz, either using a couple 12’s or 15’s. My experience these days are 12” subs can play plenty low with the right tuning of box, so 15’s aren’t needed like years ago. Sometimes you get lucky with a combination of the box and sub you were using, coupled with the acoustics of the smaller vehicle. Over the years I’ve had many instances were I used different pre-fab or customer owned boxes for subs that I sold and sometimes they sounded awesome, sometimes they only played low, sometimes they only had punch. Same goes for vehicles. I’ve put identical sub/box/amp setups in many different cars over the years and the results can be so different that you would assume some of the setups have twice the power or number of woofers. In the early 90’s I had a 85 Mustang GT in high school, hatchback, and I had 2 Kicker Comp 15” subs running off a Rockford Punch200ix amp. For 1993, this was a pretty stout setup, around 500w RMS, but another kid had the same setup in the back of his mini truck and comparing them back to back, mine easily had twice the output, especially on the low notes. But rule of thumb if you want more deep bass. Box needs to be bigger, and if it’s ported you can make the port smaller in area or longer in length to lower the tuning of the box.


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## 2unfknblvbl

Im currently installing a system in my Mercury Milan, just the 6 speaker version with sync. I have 2 15" orion xtr (750 rms) on a skar rp-1500.1d (benched over 1500 rms, not sure the wattage tho) and made the decision to switch from a vented enclosure to a sealed one after reading the manufacturers recommendations. This is all new to me, but it seems to be an accepted formula. Im building the box to 2 ft³ and should be close to fully powered without clipping, but will know more after my buddy tunes it with an oscope


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## saltyone

Every time I believe I have everything figured out, I read a thread like this one and it throws me for a loop. I came into the thread with one set of beliefs. My beliefs were shot full of holes by page two, and by the end of page three I was almost back to my original beliefs. 

Is there consensus about SQ andsub boxes? Can there be a consensus in a community like this one? Which way is up and which way is down? I’m more confused than ever. Crap…now I’m thinking about adding a second 12” and using a sealed enclosure. LOL! Just freaking shoot me.


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## Grinder

saltyone said:


> Every time I believe I have everything figured out, I read a thread like this one and it throws me for a loop. I came into the thread with one set of beliefs. My beliefs were shot full of holes by page two, and by the end of page three I was almost back to my original beliefs.
> 
> Is there consensus about SQ andsub boxes? Can there be a consensus in a community like this one? Which way is up and which way is down? I’m more confused than ever. Crap…now I’m thinking about adding a second 12” and using a sealed enclosure. LOL! Just freaking shoot me.


I feel much the same way. Keep reading. Patterns do emerge.


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## seafish

This is the BEST explanation that i have ever watched on sealed vs ported--

INTRO from video--

"Right away lets dispel the notion that one of them will always outperform the the other ..."


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## oabeieo

saltyone said:


> Every time I believe I have everything figured out, I read a thread like this one and it throws me for a loop. I came into the thread with one set of beliefs. My beliefs were shot full of holes by page two, and by the end of page three I was almost back to my original beliefs.
> 
> Is there consensus about SQ andsub boxes? Can there be a consensus in a community like this one? Which way is up and which way is down? I’m more confused than ever. Crap…now I’m thinking about adding a second 12” and using a sealed enclosure. LOL! Just freaking shoot me.


Honestly Andy W was pretty spot on with his opening statements and his thread…. I disagree with him on a few things in other threads, but he is pretty solid here….

of course there’s some one offs that bend the rules with some trick phase filtering with dsp

but generally speaking, boxes in general, I believe his posts were well thought out and articulate and accurate…


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## saltyone

seafish said:


> This is the BEST explanation that i have ever watched on sealed vs ported--
> 
> INTRO from video--
> 
> "Right away lets dispel the notion that one of them will always outperform the the other ..."


So, basically, the very fast talking young man in the video says, “It Depends”. 

My take away from what he said, for SQ, go sealed and double up on the number of subs if you want the ability to occasionally get a little loud. Furthermore, if you really just want “loud” go with a well designed 4th order and you can get by with one less sub. Finally, all of this strongly depends on the individual sub and it’s inherent capabilities as some subs are better suited for 2nd order while others are better suited for 4th order. 

Did I get that right?


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## Grinder

saltyone said:


> So, basically, the very fast talking young man in the video says, “It Depends”.
> 
> My take away from what he said, for SQ, go sealed and double up on the number of subs if you want the ability to occasionally get a little loud. Furthermore, if you really just want “loud” go with a well designed 4th order and you can get by with one less sub. Finally, all of this strongly depends on the individual sub and it’s inherent capabilities as some subs are better suited for 2nd order while others are better suited for 4th order.
> 
> Did I get that right?


It depends...


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## Speedhunter

Usually what maker recomends is optimal, everything other is losing one end to gain another.

For example my sub is what would be said is for sealed enclosure and this is what maker recommends. By parameters, EBP shows it could work in the ported box after which you soon find out its near 100L. Similar results can be achieved with only 35L sealed. So for me taking whole trunk space and saying that this sub can work and sounds great in ported for me is nebulosis. So it depends.


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## MrHarris

oabeieo said:


> Honestly Andy W was pretty spot on with his opening statements and his thread…. I disagree with him on a few things in other threads, but he is pretty solid here….
> 
> of course there’s some one offs that bend the rules with some trick phase filtering with dsp
> 
> but generally speaking, boxes in general, I believe his posts were well thought out and articulate and accurate…


Sad he is gone


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