JD1000/1 and impedance rise question!!

[shredder1 10+ year member]

I'm in the middle of designing a 4th for a single Zvx-18 atm, can anyone tell me optimal tuning and airspace? I have ideas... Looking at excursion, velocities, phase, delay and impedance I may settle on 2.68ft3/5.36ft3 front chamber tuned 45hz /w/ 97.75in2 of port. Modeling the thing shows .7 rise /w/ a peak low 30's. Mind you this will have a sealed response under tuning so cabin size matters.
Whatever... it looks like a solid 2.5K like a constant power 2500 would touch the limits @ 1 ohm as designed. 7db flat hump before cabin gain is simulated too. Basic 2:1 4th /w/ no frills. 20hz-70hz bandwidth in vehicle should deliver. Anyone have input or maybe tips?

 

[hispls 5,000+ posts]

if I want to chase every bit of power

What is your objective here? Are you chasing numbers on the Termlab? Listening to music? Or just attempting to make your 1000/1 deliver 1000W? Stop and really think about this before getting hung up on any of this and then consider making another thread like "How to I gain on the meter?" or "How to I get my music to sound louder?"

The way a loudspeaker works is it's a complex circuit and impedance changes with frequency. So your "2 ohm" sub may be 2 ohms at 40hz then 8 ohms at 55hz. Impedance plot of a woofer in a ported box will look like some sort of misshapen cursive letter m with a low tail on the left and a tail rising up to infinity on the right. If you are playing more than 1 frequency through it you impedance will be all over the place between z-min (which may possibly be even lower than nominal impedance of your woofer) and on the high side seeing 4-6x nominal impedance at some frequencies wouldn't be unusual.

The way those "smart" amps are typically meant to work is that once they sense low impedance they'll drop the rail voltage so that they don't blow themselves up, so if it never sees below 4 ohms (or wherever they actually built in the switch) it'll be running in a mode that will produce 1000W into your 4 ohms, but once your impedance dips below 4 ohms once it will put you in low rail voltage mode where it'll only be able to make the 1000W into 2 ohms but it won't get damaged by trying to shift on the fly as your music constantly bounces around over and under whatever impedance is safe to run at the higher voltage.

Put another way, you may be able to "trick" this amp into making 1000W at one specific frequency using a 2 ohm (nominal) sub but it isn't going to accomplish a whole lot for you outside that one frequency and as others have explained you will very probably gain less than 2 clicks of the volume knob even at that one note.

 

[zoltman1991]

There are ways to answer questions without being a condescending a-hole .
Reconsider your wording next time you answer my question.
Edited to also add your post was helpful reading. So thank you for that.

 

[fa5chups]

In a silent sound room with no noise, 3 db (roughly 33%). In a car, about 10-15% Theoretical doubling of the sound to the ear requires more than an 8:1 ratio of power to realize a doubling of the volume to the ear. The math actually reads like this.
The ear perceives a doubling of the volume at roughly 9-10 db. Starting with a base line at 500 watts of input power, the math looks like this:
500 to 1000 watts, you get a 3 db gain or a 33% increase in volume.
1000 to 2000 watts, another 3 db gain or a 66% increase in volume
2000 to 4000 watts, another 3 db gain or a 99% increase, a doubling of the volume to the ear. That is a 8:1 ratio, in a perfectly quiet chamber with a mic placed 1 meter from the speaker.
So whether it’s the same wattage to a speaker that is 3 db more efficient or the same efficiency with increased power, the math applies either way. In a car environment, it will be much less that these results obtained in an sound testing room. Therefore, expect maybe a 15% difference all things being equal.

So is the sensitivity rating something really important when gauging what you think the spl of speaker will be?
Like let’s take for ex the sql15 a 95db @ w/m and the JL w7 12 a 86db (which I know is a great sub), that doesn’t mean the JL needs 8x the power to be as loud as the sql15 so how does it work

 

[Doxquzme Premium Member]

So is the sensitivity rating something really important when gauging what you think the spl of speaker will be?
Like let’s take for ex the sql15 a 95db @ w/m and the JL w7 12 a 86db (which I know is a great sub), that doesn’t mean the JL needs 8x the power to be as loud as the sql15 so how does it work

Actually, theoretically speaker-ing all things considered, all things the same, make and model line, yes, 8 times the power to hear a doubling of the volume to the ear, and that's in a test environment, likely more like 9 to 10 times as much in your car. So, if you had two JL's or an SQL's, same size, same model line, different efficiencies and it could handle that kind of power, then you need 8 times the power to makeup for that 9db difference in efficiency.

When you start comparing 12's and 15's, different cone sizes too, then when comparing the same model lines, so a JL or SQL from 12's to 15's, there is another 3db of difference to the equation if the efficiencies are the same.

 

[spokey9 5,000+ posts]

So is the sensitivity rating something really important when gauging what you think the spl of speaker will be?
Like let’s take for ex the sql15 a 95db @ w/m and the JL w7 12 a 86db (which I know is a great sub), that doesn’t mean the JL needs 8x the power to be as loud as the sql15 so how does it work

You're also comparing subs in vastly price points

For output and sound quality that the sql line has going for them...you'd need to jump up in price to find something that does both better

 

[fa5chups]

You're also comparing subs in vastly price points

For output and sound quality that the sql line has going for them...you'd need to jump up in price to find something that does both better

You're also comparing subs in vastly price points

For output and sound quality that the sql line has going for them...you'd need to jump up in price to find something that does both better

i see i was kinda js sayin like a what if idk just never knew it was that drastic of change in power to volume
which sparked the question of is sensitivy db really important when comparing speakers

 

[Doxquzme Premium Member]

i see i was kinda js sayin like a what if idk just never knew it was that drastic of change in power to volume
which sparked the question of is sensitivity db really important when comparing speakers

I see it all the time. A person goes from a very efficient 500 watt sub, gets a 1500 watt sub that's 6db less efficient and then wonders why his new sub pushed with a 1500 watts isn't any louder or in some cases isn't as loud.

The overall point is, that all if it matters and contributes to everything overall. Understanding what the numbers mean is something that used to take years to learn. Fortunately for you, the internet brings years and years of learning, right into your living room.

 

[fa5chups]

I see it all the time. A person goes from a very efficient 500 watt sub, gets a 1500 watt sub that's 6db less efficient and then wonders why his new sub pushed with a 1500 watts isn't any louder or in some cases isn't as loud.

The overall point is, that all if it matters and contributes to everything overall. Understanding what the numbers mean is something that used to take years to learn. Fortunately for you, the internet brings years and years of learning, right into your living room.

whattttt lmao thats actually crazy and what blows my mind that how many people dont know that because theres a large amnt of ppl with very simple systems like a single skar and their knowledge doesnt get much deeper than the size of sub. (I say this because i have quite a few freinds with systems getting installed in their cars so they have no idea really whats there yk?)
so how much of a factor does the fs play in enclosed subwoofers? (i think i remeber that fs in ib the speakers dont play much under that)

 

[spokey9 5,000+ posts]

i see i was kinda js sayin like a what if idk just never knew it was that drastic of change in power to volume
which sparked the question of is sensitivy db really important when comparing speakers

Sensitivity isn't as big of thing with subs since that can be overcome with power. But if put say a 15 with a sensitivity of 84db against 94db (both in a proper box for the sub) both on 100w you'll hear the more sensitive sub get louder. But sensitivity isn't something to fret over too much on a sub

 

[fa5chups]

Sensitivity isn't as big of thing with subs since that can be overcome with power. But if put say a 15 with a sensitivity of 84db against 94db (both in a proper box for the sub) both on 100w you'll hear the more sensitive sub get louder. But sensitivity isn't something to fret over too much on a sub

ah ok i got you

 

[dragon.breath 10+ year member]

But the sensitivity also does make a difference.
Several years ago a local guy built a Astro van with a wall and four 15 inch Mmats Juggernauts. And a couple of mmats d300’s. He ran it a couple of years and pulled the equipment out and sold the van to a high school kid. The kid put four 15 inch kicker comp’s and a 1000 watt kicker amp in the van. Same wall, same everything except equipment. The kickers were within a half of a db of the mmats. With less than half the power.

 

[fa5chups]

You're also comparing subs in vastly price points

For output and sound quality that the sql line has going for them...you'd need to jump up in price to find something that does both better

hey this off topic but ik somone wanting a 12 in a box budget 3-400
i was thinking between these 3
$300 - timpano 12" t2500 loaded enclosure @30hz
$400 - NVX VCW 12" or sundown sa classic 12 in d4s 'profab' box @ 32hz

But the sensitivity also does make a difference.
Several years ago a local guy built a Astro van with a wall and four 15 inch Mmats Juggernauts. And a couple of mmats d300’s. He ran it a couple of years and pulled the equipment out and sold the van to a high school kid. The kid put four 15 inch kicker comp’s and a 1000 watt kicker amp in the van. Same wall, same everything except equipment. The kickers were within a half of a db of the mmats. With less than half the power.

lmao why is that? because the kickers were matched with power perfeclty?
the jugernauts says an efficiency if 93db and kicker 90 enless im just looking at the wrong models/they changed

 

[deez283 10+ year member]

hey this off topic but ik somone wanting a 12 in a box budget 3-400
i was thinking between these 3
$300 - timpano 12" t2500 loaded enclosure @30hz
$400 - NVX VCW 12" or sundown sa classic 12 in d4s 'profab' box @ 32hz


lmao why is that? because the kickers were matched with power perfeclty?
the jugernauts says an efficiency if 93db and kicker 90 enless im just looking at the wrong models/they changed

Was the sensitivity rated at 1 watt for both subs?