Some thoughts on the ported vs sealed debate

[Steve81]

I will try a longer port. It’s the cheapest shot to try to save the design. If I don’t like the result, I’ll try the sealed or buy I comercial sub anyway.
The HPF is not adjustable and I don’t know what kind it is. Is just a standard filter that digital amps has on input.

I just thought that since I’m not liking my sub, I adjusted the receiver LPF crossover to 40 Hz (before judging me, I don’t reach my system limit!), the group delay of my sub is probably above the roof!!!!

No worries, assuming that it's a 2nd order filter, that'll do the trick of protecting the driver at least, and 350W will push the driver to xmax. Even adding the lowpass at 80Hz, the system doesn't go to hell on group delay. As Dr. Mark implies, the port velocity around 20Hz at max power will be excessive with a 3" port, though with most content, it won't be a major issue. You'd need to drive the sub pretty hard at 20Hz to reach 20m/s air velocity from the port. Given the lack of more sophisticated filters, not to mention the lack of real world content that's going to drive the sub that hard at 20Hz, it should be an acceptable tradeoff. If not, seal the sumbitch.

@TLS Guy that model of driver is discontinued, so he'd have to buy something else.

 

[TLS Guy]

No worries, assuming that it's a 2nd order filter, that'll do the trick of protecting the driver at least, and 350W will push the driver to xmax. Even adding the lowpass at 80Hz, the system doesn't go to hell on group delay. As Dr. Mark implies, the port velocity around 20Hz at max power will be excessive with a 3" port, though with most content, it won't be a major issue. You'd need to drive the sub pretty hard at 20Hz to reach 20m/s air velocity from the port. Given the lack of more sophisticated filters, not to mention the lack of real world content that's going to drive the sub that hard at 20Hz, it should be an acceptable tradeoff. If not, seal the sumbitch.

@TLS Guy that model of driver is discontinued, so he'd have to buy something else.

Then he needs to cut his losses and do a new design with a different driver, or drivers, or get that KEF Kube. Unfortunately his current sub is fatally mistuned. He should have posted here first.

 

[caioferrari]

Then he needs to cut his losses and do a new design with a different driver, or drivers, or get that KEF Kube. Unfortunately his current sub is fatally mistuned. He should have posted here first.

Yes, I should. But as I mentioned a few pages ago, i contacted Jbl tech support and they said the design was Ok

 

[caioferrari]

No worries, assuming that it's a 2nd order filter, that'll do the trick of protecting the driver at least, and 350W will push the driver to xmax. Even adding the lowpass at 80Hz, the system doesn't go to hell on group delay. As Dr. Mark implies, the port velocity around 20Hz at max power will be excessive with a 3" port, though with most content, it won't be a major issue. You'd need to drive the sub pretty hard at 20Hz to reach 20m/s air velocity from the port. Given the lack of more sophisticated filters, not to mention the lack of real world content that's going to drive the sub that hard at 20Hz, it should be an acceptable tradeoff. If not, seal the sumbitch.

@TLS Guy that model of driver is discontinued, so he'd have to buy something else.

But with a LPF at 40 Hz as is, I’m i correct to assume the group delay gone to hell On my actual design ?

(i really appreciate having a WinISD on Mac….)

 

[caioferrari]

Unfortunately that sub can not be tuned with a port. It takes a port 4" in diameter and 37 inches long! That would have a horrendous audible port resonance.

If it were me, I would buy another driver and seal the port. That really would make a very acceptable sub, that you would enjoy.

I missed the problem of using the actual system with the port sealed..

I could look for another driver too, but it would be another automotive stuff

 

[Steve81]

But with a LPF at 40 Hz as is, I’m i correct to assume the group delay gone to hell On my actual design ?

Yup. The model shows severely restricted bandwidth due to the 20Hz HPF and 40Hz LPF, and group delay on the order of 46ms at 30Hz. That’s about 1.4 cycles worth of delay, which could be audible.

 

[Steve81]

I could look for another driver too, but it would be another automotive stuff

Technically this guy is an automotive driver, but I’d take a couple in a heartbeat. What do you have available, and what can you afford? If you’ve got the time to DIY, that makes the most fiscal sense. Heck, even paying a local carpenter probably makes more sense than buying subs from most manufacturers. You’ve already got the amp side of the equation taken care of at least.

 

[lovinthehd]

Overall I just keep thinking just why is there so little choice in such a large population?

 

[Steve81]

Overall I just keep thinking just why is there so little choice in such a large population?

Overall I’m thinking if Dr. Mark and I can do a pretty decent engineering job with a random, discontinued 10” car audio driver, and a fixed 45L box size, wtf are most manufacturers doing?

 

[William Lemmerhirt]

Yup. The model shows severely restricted bandwidth due to the 20Hz HPF and 40Hz LPF, and group delay on the order of 46ms at 30Hz. That’s about 1.4 cycles worth of delay, which could be audible.

Yikes. It’s like a bandpass subwoofer.

 

[Verdinut]

Yikes. It’s like a bandpass subwoofer.

A group delay of 46 ms is rather odd for a loudspeaker. According to Floyd Toole, normal domestic and monitor loudspeakers don't exceed group delays of more than 2 ms (detection treshold is in the range of 1.6 to 2 ms and more noticeable in reflective spaces).

 

[Steve81]

IMO, nobody can hear a group delay of 46 ms. That group delay stuff is really debatable and is not worth noticing according to some acoustical experts.

That entirely depends on where in the frequency spectrum the 46ms delay takes place. AFAIK, there’s rather a dearth of hard information on group delay audibility in low bass. That’s why Josh Ricci put those 1 and 1.5 cycle guidelines in his GD graphs as hypothetical/speculative points where it would become an issue. More info about that here.

Although the audibility of group delay in bass frequencies hasn’t been found to be the subject of extensive research, an informal guideline in the audio business is that group delay under 1.5 cycles in bass frequencies isn’t likely to be audible, and in very deep frequency playback at around 30 Hz and under, human hearing will tolerate even higher levels of group delay before noticing it. According to the respected audio researcher Peter Mitchell, group delay in excess of 20 milliseconds can alter the subjective character of bass in more commonly heard bass frequencies, so for 50 Hz and above group delay should be kept to less than a single cycle for total inaudibility.

As far as the acoustical experts, I’d opine they’d be better served running actual blind trials to fill in our gaps in knowledge rather than spouting their baseless opinions. I’d further opine a lot of so called “experts” are fucking morons.

 

[caioferrari]

Overall I just keep thinking just why is there so little choice in such a large population?

because our population is weird. It’s a poor country with rich people who likes to be exclusive. So, some products are rare or very expensive just to be exclusive.
Just to know, a SVS Sb3000 costs about U$6k here! A Revel speaker is just twice off US price. What the reck the SVS dealer is thinking? About being exclusive. :/

Overall I’m thinking if Dr. Mark and I can do a pretty decent engineering job with a random, discontinued 10” car audio driver, and a fixed 45L box size, wtf are most manufacturers doing?

If you see the JBL manual, the port length and the Fb doesn’t match! The user manual seems to be wrong !!!

Yikes. It’s like a bandpass subwoofer.

At the room, it doesn’t! I get a pretty flat response between 20 and 40 Hz.

A group delay of 46 ms is rather odd for a loudspeaker. According to Floyd Toole, normal domestic and monitor loudspeakers don't exceed group delays of more than 2 ms (detection treshold is in the range of 1.6 to 2 ms and more noticeable in reflective spaces).

yes! So we found why my sub sound suck at ported mode.

Yup. The model shows severely restricted bandwidth due to the 20Hz HPF and 40Hz LPF, and group delay on the order of 46ms at 30Hz. That’s about 1.4 cycles worth of delay, which could be audible.

That’s what I’m looking for: a measurable explanation about why my sub suck.

 

[caioferrari]

Technically this guy is an automotive driver, but I’d take a couple in a heartbeat. What do you have available, and what can you afford? If you’ve got the time to DIY, that makes the most fiscal sense. Heck, even paying a local carpenter probably makes more sense than buying subs from most manufacturers. You’ve already got the amp side of the equation taken care of at least.

There are a lot of options here, but almost all of them suck because they’re made for the people who wants to play loud at the car without caring about quality. There are a just a few brands who makes drivers for sound quality that may be suitable for home use.
What are the parameters I should look for ?

 

[caioferrari]

I found I FR of KEF 12b.
I think it’s my best bet here in Brazil

 

[Verdinut]

There are a lot of options here, but almost all of them suck because they’re made for the people who wants to play loud at the car without caring about quality. There are a just a few brands who makes drivers for sound quality that may be suitable for home use.
What are the parameters I should look for ?

Just look for home drivers rather than car drivers. There are many brands of good home loudspeaker drivers around. There should be some available in Brazil, no? KEF is a good brand.

 

[Steve81]

There are a lot of options here, but almost all of them suck because they’re made for the people who wants to play loud at the car without caring about quality. There are a just a few brands who makes drivers for sound quality that may be suitable for home use.
What are the parameters I should look for ?

Unfortunately all the Thiele-Small parameters matter to one extent or another, and their interplay is what makes modeling programs so useful. If you could figure out a way to import Dayton Audio drivers from partsexpress.com for a reasonable cost, you’d be in business, vs trying to model random car audio drivers.

 

[caioferrari]

Just look for home drivers rather than car drivers. There are many brands of good home loudspeaker drivers around. There should be some available in Brazil, no? KEF is a good brand.

No! In Brasil we are used to try automotive drivers to home applications. Our other options are pro drivers that has higher sensitivity and very high Fs. For sub we need to get a 18” driver to achieve some low frequency.

Unfortunately all the Thiele-Small parameters matter to one extent or another, and their interplay is what makes modeling programs so useful. If you could figure out a way to import Dayton Audio drivers from partsexpress.com for a reasonable cost, you’d be in business, vs trying to model random car audio drivers.

I always think Thiele Small as a definitive guide for driver sound. As I see a Dayton with similar TS to my JBL I think as similar sounding.
I tried to simulate a U$230 Dayton shipping to Brasil. The shipping is about U$230 and there are another duty taxes that Parts Express can’t estimate.
Considering I could the Dayton driver with my enclosure as is, it’s more than 60% of a brand new KEF Kube 12b !

 

[lovinthehd]

because our population is weird. It’s a poor country with rich people who likes to be exclusive. So, some products are rare or very expensive just to be exclusive.
Just to know, a SVS Sb3000 costs about U$6k here! A Revel speaker is just twice off US price. What the reck the SVS dealer is thinking? About being exclusive. :/

Hope you at least get the extra $100 gloss black finish for the $6k Hard to see how that $1100/1200 sub goes up to $6k, tho. Back many years ago I did some exporting to Brazil, import permits were exacting and duties high and both often used as an excuse for bribes to Customs to make things go smoother/easier. Hope you find something suitable but the Kef 12b is less than the price here ($950 here in US) gotta wonder what Kef's secret is....

 

[caioferrari]

Hope you at least get the extra $100 gloss black finish for the $6k Hard to see how that $1100/1200 sub goes up to $6k, tho. Back many years ago I did some exporting to Brazil, import permits were exacting and duties high and both often used as an excuse for bribes to Customs to make things go smoother/easier. Hope you find something suitable but the Kef 12b is less than the price here ($950 here in US) gotta wonder what Kef's secret is....

I said how prices go to 6k: we have people here who wants to pay more just to be exclusive.
The KEF is imported from Paraguay where the prices are about the same of USA. The KEF I wrote about was imported when USD was cheaper for us. Since right now the USD is more expensive, seems the product is even cheaper.
When we buy from official importing, the prices are about 2 times the US price (Apple, Revel, Denon etc are just like that). Sometimes there are some crazy dealers who puts the prices that high.