Some thoughts on the ported vs sealed debate

[Steve81]

Lol, nope, not gonna drag Ed in here; I am sure he has enough problems! Anyway, I doubt he would say that any one design is superior over others, and that application and context has to be considered.

Probably not when the other design is superior to the SVS offering Still, might be interesting to get perspective on what their design decisions were. Tom V. Is clearly going for the SubM formula in his own way.

PS: I had the successor to the ISD, the PB-10NSD. I think the main switch was diaphragm material.

 

[Steve81]

Most people would be happy with an in-room F3 of 30Hz so long as it has adequate dynamic range to back that extension up.

In truth, I’d say something like the old Hsu MBM’s with slightly deeper tuning would cover most people’s desires pretty well. I don’t know that many outside the enthusiast community care that much about rumble vs a good mid-bass punch in the gut.

 

[caioferrari]

I’d like to add my experience to the thread.

I have a diy sub here that I used in ported mode by a long time. I always liked its sound and and tried to test it in a sealed mode. With the enclosure size, i simulated a Qtc = 0,6

I rana frequency response test until I matched the spl on low frequencies.
I perceived a difference in sound between the two modes. On sealed the sound seemed to be more damped, should be the “fast” bass? I don’t know. The sound seemed more natural for me, more “soft”.
I feel dumb trying to find adjectives to describe what I heard…
But since I’m a data-oriented guy, I’d like to know why I’m hearing that difference. I don’t think is just SPL… I don’t hear those differences when I lower the volume of my system.

 

[Verdinut]

I’d like to add my experience to the thread.

I have a diy sub here that I used in ported mode by a long time. I always liked its sound and and tried to test it in a sealed mode. With the enclosure size, i simulated a Qtc = 0,6

I rana frequency response test until I matched the spl on low frequencies.
I perceived a difference in sound between the two modes. On sealed the sound seemed to be more damped, should be the “fast” bass? I don’t know. The sound seemed more natural for me, more “soft”.
I feel dumb trying to find adjectives to describe what I heard…
But since I’m a data-oriented guy, I’d like to know why I’m hearing that difference. I don’t think is just SPL… I don’t hear those differences when I lower the volume of my system.

If the transient response of your subwoofer in the ported box was not as tight than in the sealed enclosure, here are the most possible reasons:
1. The sub is designed only to operate in a sealed cabinet (It has a Qts above 0.5)
2. The ported box was not properly tuned for the driver
3. The amplifier driving it had too high an output resistance

When a subwoofer is designed to function in a ported box, the box has the right net internal volume, with its resonance tuned for the driver Thiele/Small parameters, and the amplifier is matched with it, the transient response should be good and comparable to that of a sealed subwoofer.

 

[Steve81]

I’d like to add my experience to the thread.

I have a diy sub here that I used in ported mode by a long time. I always liked its sound and and tried to test it in a sealed mode. With the enclosure size, i simulated a Qtc = 0,6

I rana frequency response test until I matched the spl on low frequencies.
I perceived a difference in sound between the two modes. On sealed the sound seemed to be more damped, should be the “fast” bass? I don’t know. The sound seemed more natural for me, more “soft”.
I feel dumb trying to find adjectives to describe what I heard…
But since I’m a data-oriented guy, I’d like to know why I’m hearing that difference. I don’t think is just SPL… I don’t hear those differences when I lower the volume of my system.

Could be expectation bias,, could be some of the factors Verdinut described, etc. I will say an FR that's tilted towards the high end of a subwoofer's passband will tend to sound "faster", simply because low bass sound "slow". Low bass involves huge wavelengths with long decay times, etc., and depending on how hard you drive the system (i.e. towards the limits), the FR will change as the EQed response reverts back to the natural response.

 

[caioferrari]

If the transient response of your subwoofer in the ported box was not as tight than in the sealed enclosure, here are the most possible reasons:
1. The sub is designed only to operate in a sealed cabinet (It has a Qts above 0.5)
2. The ported box was not properly tuned for the driver
3. The amplifier driving it had too high an output resistance

When a subwoofer is designed to function in a ported box, the box has the right net internal volume, with its resonance tuned for the driver Thiele/Small parameters, and the amplifier is matched with it, the transient response should be good and comparable to that of a sealed subwoofer.

The Sub has a 0.4 Qts
The box was properly tuned.

The driver is a JBL GTO 1014D in a 43L box and Fb = 30Hz

 

[Verdinut]

The Sub has a 0.4 Qts
The box was properly tuned.

The driver is a JBL GTO 1014D in a 43L box and Fb = 30Hz

From the technical data supplied by JBL, the optimal box volume for this sub driver is 35.4 liters and it should be tuned to 33.0 Hz.

IMO, since you used a box volume larger by 21.4% than the one suggested, there was a reduced air compression on the cone which contributed to a looser control with resulting reduced transient response.

 

[caioferrari]

From the technical data supplied by JBL, the optimal box volume for this sub driver is 35.4 liters and it should be tuned to 33.0 Hz.

IMO, since you used a box volume larger by 21.4% than the one suggested, there was a reduced air compression on the cone which contributed to a looser control with resulting reduced transient response.

I know that. But if you see the next model, JBL Club that has essentially the same TS parameters is recommended to be used with 40 ish liter enclosure.
I contacted the tech team that told me the 35L box was optimized to be used at car…
Could be that volume increase that decreased transient?

but… assuming that the answer is yes, we do have parameters that tell us different sounding beyond frequency response, right?

 

[Steve81]

but… assuming that the answer is yes, we do have parameters that tell us different sounding beyond frequency response, right?

As noted, FR isn’t a single, static thing. Subs with EQed response or ports will begin to compress as they reach their limits. Re: decay times, see this:

RT60 Graph

.

 

[Verdinut]

I know that. But if you see the next model, JBL Club that has essentially the same TS parameters is recommended to be used with 40 ish liter enclosure.
I contacted the tech team that told me the 35L box was optimized to be used at car…
Could be that volume increase that decreased transient?

but… assuming that the answer is yes, we do have parameters that tell us different sounding beyond frequency response, right?

Your JBL GTO 1014D is a sub to be used in a car. That could explain what is happening to its performance. You should ask your questions to an expert in car audio. This site is for home theater audio purposes.

 

[caioferrari]

Your JBL GTO 1014D is a sub to be used in a car. That could explain what is happening to its performance. You should ask your questions to an expert in car audio. This site is for home theater audio purposes.

It makes no sense.

 

[Verdinut]

It makes no sense.

What makes no sense?

 

[TLS Guy]

It makes no sense.

It probably does make sense.

Are you using that driver in a car or for home use? It is a car subwoofer driver. Generally drivers designed for car use have a skewed response because of the cab gain of car environments, that makes them unsuitable for home Hi-Fi/HT use as a rule. I have not modelled the driver, but I can bet that is you issue. But the Fs of the driver really rules it out for home use, as at best it would be a bass module and not a sub driver.

 

[Steve81]

It makes no sense.

What he’s saying is that because it’s a car audio driver, it’s inherently designed to roll off earlier than a comparable sealed unit built for the purpose of home audio. There is more cabin gain in a car, so less need for extension in the design. As you push the sub harder, this will tend to show through in the FR, regardless of EQ.

 

[caioferrari]

What makes no sense?

you tell me to ask about my sub to a car áudio especialist.
It’s a speaker that operates under the same laws os physics of any other speaker.

I asked about difference between this speaker operating in a bass reflex and sealed in my room. Your answer should not depend if it’s a car, pro or home speaker.

 

[caioferrari]

What he’s saying is that because it’s a car audio driver, it’s inherently designed to roll off earlier than a comparable sealed unit built for the purpose of home audio. There is more cabin gain in a car, so less need for extension in the design. As you push the sub harder, this will tend to show through in the FR, regardless of EQ.

But that was not what I was asking about.

 

[Steve81]

But that was not what I was asking about.

You were asking why it sounded “faster” sealed than ported, correct? Between that and the RT measurements I referenced earlier, you’ll find your answer.

 

[caioferrari]

You were asking why it sounded “faster” sealed than ported, correct? Between that and the RT measurements I referenced earlier, you’ll find your answer.

i didn’t understand what the compression you said is related with decay time.

 

[davidscott]

Maybe a dumb question but where does a sealed sub with a passive radiator fit in the ported vs sealed debate? Just a question as I have never owned a sub and since purchasing a condo I probably never will. My tower speakers provide plenty of bass (38 -29 plus or minus 3db) and since they are close to the back wall maybe a bit more. Thanks.

 

[TLS Guy]

i didn’t understand what the compression you said is related with decay time.

As I said, I have not modelled the driver. In general car drivers are designed specifically for sealed alignment. Just eyeballing the T/S parameters that seems to be the case. My hunch is that in a vented alignment the total system Q is high. This results in over resonant reproduction, although with optimal modelling this can be minimized.
If you build any DIY speaker you really have to model it, and never take a vendors word for anything. Then you really have to fuss with the model to make certain you have optimized it for optimal sound quality. If you did not model your builds then your comments carry no weight at all about generalized conclusions.