Some thoughts on the ported vs sealed debate

[TLS Guy]

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.

An ABR design is virtually the same as a vented design, except bass roll off is steeper at 36 db/octave rather than 24db/octave for a port. ABR is selected if the port will not fit in the box or is long enough to give rise to a port resonance in the operating range of the design.

 

[Steve81]

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

I'm suggesting you perform some measurements. You EQ'ed at a certain level using measurements, but that didn't tell you the whole story. This may: start running sweeps on your sub in sealed mode at a low level, and push the volume up in increments you are comfortable with (3dB steps perhaps), and observe changes in FR and RT60 behavior in the system. Don't drive the sub to self destruction of course, and perhaps have some ear plugs at the ready. Now repeat the experiment with the sub in ported mode. Compare and contrast, and you may arrive at an answer.

 

[isolar8001]

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.

As someone who sold, designed and installed high end car audio systems...listen to what the experts are telling you here.
Car drivers are designed differently.
Or maybe the 3 days I spent at a Rockford Fosgate training camp were all a hallucination ?

 

[davidscott]

An ABR design is virtually the same as a vented design, except bass roll off is steeper at 36 db/octave rather than 24db/octave for a port. ABR is selected if the port will not fit in the box or is long enough to give rise to a port resonance in the operating range of the design.

Thanks for the info.

 

[caioferrari]

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.

the driver is not designed for sealed enclosure, that driver works well on both alignments, it’s EBP is around 60.
My project was modeled and I’ve not trusted on vendors, I really don’t know why you’re assuming that.

 

[caioferrari]

As someone who sold, designed and installed high end car audio systems...listen to what the experts are telling you here.
Car drivers are designed differently.
Or maybe the 3 days I spent at a Rockford Fosgate training camp were all a hallucination ?

I don’t understand your point. I’m not telling that’s no difference between car drivers and home drivers.
My question was never about “why my car speaker sounds bad in my room” or “why my car driver sound worse than a home driver”.

I said earlier what was my question.

If a car driver makes you guy send my to talk with a car audio specialist, let’s change the question:

why a SVS sub working no sealed mode sounds “faster” than a ported one?

what is the measurement that shows that? Or it’s a placebo?

 

[Verdinut]

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.

A driver in a sealed box with a passive radiator functions like a ported box. You adjust the box resonance with the use of added weights to the moving mass of the passive radiator.

 

[Verdinut]

If a car driver makes you guy send my to talk with a car audio specialist, let’s change the question:

why a SVS sub working no sealed mode sounds “faster” than a ported one?

I answered that question in post #24. TLS Guy gave you answers as well. You would need to read books that teach you about loudspeaker functioning. There's not much more help we can give you here.

 

[Steve81]

why a SVS sub working no sealed mode sounds “faster” than a ported one?

what is the measurement that shows that? Or it’s a placebo?

Perform my experiment. You've got the relevant measures (FR, RT60 decay) and the equipment given that you FR matched the sub in sealed and ported mode. You'll find out if its placebo, or if there's actually more resonance (slowness) in your room between the sealed and ported alignments. I'm not trying to be an arse; I'm as interested in the results as you are.

 

[lovinthehd]

"Fast" for subs is just not good terminology.

 

[William Lemmerhirt]

"Fast" for subs is just not good terminology.

Right?!?! A 25hz tone is 25 times per second no matter how fast or slow it is! Lmao.

 

[Verdinut]

Good transient response of a speaker driver has nothing to do with frequency. It's how the driver responds to the amplifier in moving instantly upon receiving a current surge, and stopping its excursion with very minimal delay which no one can notice when the amplifier stops supplying it with power.

Of course, you can get that excellent transient response only with a good solid state amplifier. No tube amp will have an output resistance low enough.

 

[Steve81]

Good transient response of a speaker driver has nothing to do with frequency. It's how the driver responds to the amplifier in moving instantly upon receiving a current surge, and stopping its excursion with very minimal delay which no one can notice when the amplifier stops supplying it with power.

Of course, you can get that excellent transient response only with a good solid state amplifier. No tube amp will have an output resistance low enough.

You’re not accounting for the room in this analysis. For example, why did I seal my LCR array? I decided to investigate system performance one day, having set everything up as per usual guidelines (80Hz cross, speakers were vented). I measured the speaker’s FR without the subwoofer in play, but the high-pass filter still in place. Much to my surprise, there was a rather large peak around 45Hz, nearly an octave below the XO frequency. I decided to try sealing the speakers with manufacturer supplied plugs, and set the XO up to 120Hz to minimize driver excursion on the LCRs. The peak was eliminated, and I’ve had no reason to revisit that decision.

To wit, if the peak was that bad with an XO in place, it certainly would have been a very audible issue if I had run the speakers full range.

 

[Verdinut]

You’re not accounting for the room in this analysis. For example, why did I seal my LCR array? I decided to investigate system performance one day, having set everything up as per usual guidelines (80Hz cross, speakers were vented). I measured the speaker’s FR without the subwoofer in play, but the high-pass filter still in place. Much to my surprise, there was a rather large peak around 45Hz, nearly an octave below the XO frequency. I decided to try sealing the speakers with manufacturer supplied plugs, and set the XO up to 120Hz to minimize driver excursion on the LCRs. The peak was eliminated, and I’ve had no reason to revisit that decision.

To wit, if the peak was that bad with an XO in place, it certainly would have been a very audible issue if I had run the speakers full range.

Room acoustics are a completely different matter.

 

[Steve81]

Room acoustics are a completely different matter.

Indeed, but they are rather relevant to @caioferrari ’s observations.

 

[davidscott]

A driver in a sealed box with a passive radiator functions like a ported box. You adjust the box resonance with the use of added weights to the moving mass of the passive radiator.

Thanks

 

[Verdinut]

Thanks

It's my pleasure to reply to intelligent questions.
By the way, if the fs of the moving mass of the passive radiator is lower than that for the required fb, then it becomes useless.

 

[caioferrari]

Perform my experiment. You've got the relevant measures (FR, RT60 decay) and the equipment given that you FR matched the sub in sealed and ported mode. You'll find out if its placebo, or if there's actually more resonance (slowness) in your room between the sealed and ported alignments. I'm not trying to be an arse; I'm as interested in the results as you are.

I already did some measurments. I don't think I cant interpret my RT60 graphs ...

all was measured on listening position

 

[Steve81]

I already did some measurments. I don't think I cant interpret my RT60 graphs ...

all was measured on listening position

The change in FR is expected, and you can see the impact of the sealed alignment in the low 20Hz range, as it serves to reduce that peak there by 5dB.

On the RT60, the line graph is at 67.88Hz and shows no appreciable difference there (wouldn’t expect one). The waterfall shows the full bandwidth, and there’s less acoustic energy there after 581ms with sealed vs ported.

 

[caioferrari]

The change in FR is expected, and you can see the impact of the sealed alignment in the low 20Hz range, as it serves to reduce that peak there by 5dB.

On the RT60, the line graph is at 67.88Hz and shows no appreciable difference there (wouldn’t expect one). The waterfall shows the full bandwidth, and there’s less acoustic energy there after 581ms with sealed vs ported.

would I set the line at another frequency?

As you see, is there a diference between the two alignments or I’m being fooled by placebo effect?

thank your time so far