Sub Comparison

[1ndatrunk 10+ year member]

I've searched the threads for days now and still don't have any concrete answers, so I'll just ask you guys. In the trunk of my car I want to either go with three 18s sealed, or one 18 ported, both on 2000watts.

The subs would be 3 Mach 5 MJMs sealed in a 9-10cuft enclosure.

The single sub would be an AQ HDC3 18 in 7cuft@38hz.

I'm sure the sealed subs would get lower and sound better than the ported single sub, but which will get louder? The MJs would only actually get a 1.3 load, so probably only about 1700-1800watts, or 600watts per sub.

The AQ on the other hand would get a good amount of clean power and have more room in my trunk to "breath". Which would you choose? Will the cone area, eventhough they're sealed, be enough to take the AQ?

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[bones22 5,000+ posts]

3 18's > 1 18

 

[jusBloud 10+ year member]

go 3. imo

 

[1ndatrunk 10+ year member]

I'd go 1xAQHDC318
3 18's =more surface area but if they're barely moving you're wasting all that space on nothing

I understand what you mean, but the MJs are rated 700rms, so would 600 really be that far off?

 

[1ndatrunk 10+ year member]

go 3. imo

Any real reasons behind that sir?

 

[bones22 5,000+ posts]

if you go with 3 you wont be using any huge amount more of space

if they are rated at 700 rms they will do damn good on 600 each if you are sure you will get close to it

 

[1ndatrunk 10+ year member]

My amp does right at 1930@1ohm, and the 3 18s would yield a 1.34load. That would get me about 1600-1800 realistic watt @ that load. Even at 1600, I would get over 500 per sub, or a little less than 200 watts under rms

 

[bladebarrier 10+ year member]

I've searched the threads for days now and still don't have any concrete answers, so I'll just ask you guys. In the trunk of my car I want to either go with three 18s sealed, or one 18 ported, both on 2000watts.
The subs would be 3 Mach 5 MJMs sealed in a 9-10cuft enclosure.

The single sub would be an AQ HDC3 18 in 7cuft@38hz.

I'm sure the sealed subs would get lower and sound better than the ported single sub, but which will get louder? The MJs would only actually get a 1.3 load, so probably only about 1700-1800watts, or 600watts per sub.

The AQ on the other hand would get a good amount of clean power and have more room in my trunk to "breath". Which would you choose? Will the cone area, eventhough they're sealed, be enough to take the AQ?

3 Sealed will generally beat a single ported unless you're talking about a one note box.

Here's why. Each time you double up the surface area you'll get about 3db more sound, assuming no increase in power. So 2 18's will be 3db louder than a single, and 3 18's will be 4.5 db louder than a single. A ported box brings about 3db increase, as it utilizes the back side of the woofer, as if it were a second speaker. Sloppy spl boxes will boost it even more and turn the port into a resonant noise maker (think of the sound you get when blowing across a soda bottle top, when it's empty) and can get even more than that, but only over a certain frequency range, and can severely restrict the low bass ability of the subs when they operate below the tuning frequency, and act as if they're not in a box at all.

Now, you also need to consider the efficiency and design of the subs. If you take subs designed for a large box, and toss them in sealed boxes that are way too small, you'll only see this increase in spl occur at higher frequencies that you don't want your sub to produce. They will become extremely inefficient at low frequencies.

If you link some spec sheets for the subs in question, I'll run some math and give you some spl curves, but if the MJ's are designed for the smaller sealed box properly, they will almost assuredly out perform a single ported 18 at anything aside from sloppy, narrow frequency range, bass.

 

[JimJ 5,000+ posts]

I'd go 1xAQHDC318
3 18's =more surface area but if they're barely moving you're wasting all that space on nothing

Or by keeping cone travel to a minimum, linearity is maximized...//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif Lots of cone area with very little coil movement can be a very good thing for accuracy.

 

[bladebarrier 10+ year member]

My amp does right at 1930@1ohm, and the 3 18s would yield a 1.34load. That would get me about 1600-1800 realistic watt @ that load. Even at 1600, I would get over 500 per sub, or a little less than 200 watts under rms

That's not much power for multiple 18's, and increasing your power will allow you to put out db's without needing to use such a large box, but airspace is cheap if you're willing to sacrifice it. New alternators and amps are much more costly.

 

[skmfkr 5,000+ posts]

i think the single 18 would be louder. btw i know a guy that had 2 aa 18s sealed in like 11cubes and 2 saz 1500s and did a 143. and my aq 15 and 2200d does a 147 ported

 

[bladebarrier 10+ year member]

Or by keeping cone travel to a minimum, linearity is maximized...//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif Lots of cone area with very little coil movement can be a very good thing for accuracy.

This.

The less your woofers have to move the better. Excursion is only about utilizing the least amount of airspace for the maximum output. Larger airspace and cone area is always the optimal choice, over high excursion, high rms, subs.

It's also why concert speakers aren't tiny little boxes designed to take stupid amounts of power. If I went to a concert and saw a RE XXX type of sub on stage powered with 3k watts, I'd have to wonder if the sound engineer was dropped on his head as a child. Only in car audio would anyone try to create such an extreme design (mostly for bragging rites).

 

[1ndatrunk 10+ year member]

3 Sealed will generally beat a single ported unless you're talking about a one note box.
Here's why. Each time you double up the surface area you'll get about 3db more sound, assuming no increase in power. So 2 18's will be 3db louder than a single, and 3 18's will be 4.5 db louder than a single. A ported box brings about 3db increase, as it utilizes the back side of the woofer, as if it were a second speaker. Sloppy spl boxes will boost it even more and turn the port into a resonant noise maker (think of the sound you get when blowing across a soda bottle top, when it's empty) and can get even more than that, but only over a certain frequency range, and can severely restrict the low bass ability of the subs when they operate below the tuning frequency, and act as if they're not in a box at all.

Now, you also need to consider the efficiency and design of the subs. If you take subs designed for a large box, and toss them in sealed boxes that are way too small, you'll only see this increase in spl occur at higher frequencies that you don't want your sub to produce. They will become extremely inefficient at low frequencies.

If you link some spec sheets for the subs in question, I'll run some math and give you some spl curves, but if the MJ's are designed for the smaller sealed box properly, they will almost assuredly out perform a single ported 18 at anything aside from sloppy, narrow frequency range, bass.

The Mach5 site says the MJs take 3.3 sealed optimal. I know my power is a little low, but I am at least close to rms on these subs.

 

[1ndatrunk 10+ year member]

i think the single 18 would be louder. btw i know a guy that had 2 aa 18s sealed in like 11cubes and 2 saz 1500s and did a 143. and my aq 15 and 2200d does a 147 ported

Were both of these setups in the same vehicle?

Also if I went with the sealed triple threat I would be at max capacity in my trunk. Would this effect anything, as opposed to the single sub having a few cuft of space left over in trunk to breath?

 

[1ndatrunk 10+ year member]

Or by keeping cone travel to a minimum, linearity is maximized...//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif Lots of cone area with very little coil movement can be a very good thing for accuracy.

Accuracy isn't an issue, I just want loud with a tad bit of sq