So I am undecided on subs....

[chipstien]

I have been wracking my brain for 3 weeks now trying to design a system for my volvo V40 sport wagon. Between different brand subs and different sizes I am truly floored. For starters, I will be upgrading the electrical as needed. Big 3 with 1/0 Knu. OFC wire, along with at least one set of said wire running to the back with a HC3800 battery or equivalent. Amps are pretty much a given at this point though the end wattage is dependent on the subs I get. Crescendo 5500 or two 3500 strapped or single 3500. I wont go into the highs at this point as it is probably irrelevant.

So my original plans were two AQ HDC3 15 Al on the 5500. Then I have also kicked around the idea of 1 HDC3 18 Al on a 3500 but scratched that idea because, while I have lately been listening to mostly hip hop, rap and Top40, I also listen to a ton of Country with some various other genres of music thrown in. I have heard that the 18 would be a little slow to react on that stuff and while I am leaning towards an SPL setup, I am not sure how much I am willing to sacrifice on SQ. Which leads me to my last setup... 2 Fi Q 15,s on a single 3500. AQ enclosures would be tuned around 35 hz while I am leaning towards a 32 or 33 hz tuning on the Fi Q. Airspace for 15s is slightly low at 3.1cuft after displacements while 18 enclosure was 6cuft after displacements.

A couple other options I have kicked around but haven't put a ton of weight into is 2 Fi Q high QTS 18's in sealed enclosure or a single 18 and two 10's tuned higher. Feel free to comment on that too.

So bottom line, what should I run? Will the AQs still have pretty good SQ or am I giving up a ton there. If so, will the Fi Q still get loud as heck like I want? Any other subs in the 200 to 350 price range that might suit me better? My only requirements are 15" or larger. I already have a SQ setup in my truck with four 10's in a sealed enclosure and want to go big for fun this time. Need any more info just ask.

Take care

*edit*, I should clarify that the 15 enclosures are 3.1 cubes PER SUB....

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[Slayerx 10+ year member]

W7

 

[chipstien]

No chance. I used to do the expensive named brand stuff but no more. My truck is all the good early 2000 Fosgate stuff and had a Mustang with four 12W6's in it. JL's are great but you pay too much for the name. I am sticking to the small internet guys this time around.

 

[Electrodynamic 10+ year member]

I have heard that the 18 would be a little slow to react on that stuff and while I am leaning towards an SPL setup, I am not sure how much I am willing to sacrifice on SQ.

Why would the 18" be slow to react? The size of the driver has nothing to do with transient response.

 

[mylows10 5,000+ posts]

Dc all the way

 

[i2ain2thunder 10+ year member]

Why would the 18" be slow to react? The size of the driver has nothing to do with transient response.

Yes but typically 8s and 10s have the most accurate response IMO.

 

[disturbed471985 5,000+ posts]

I have heard many of 18"s that could hang with alot of so called sq subs . All in the box!!

 

[mast240 10+ year member]

yup... a good 18 (one designed for more of the sq spectrum, instead of spl) will be able to hang with other "sq" 10's and 12's all day long. if your looking for sq tho, hdc3's are not the way to go. the fi q would sound nice, as would a pair of ssa icon 15's, as well as a dc level 3 or 4.

 

[mlstrass 5,000+ posts]

HDC's sound fine and can sound very good in the right enclosure, unfortunately 3.1 net is NOT the right size for a 15" HDC....

 

[Electrodynamic 10+ year member]

Yes but typically 8s and 10s have the most accurate response IMO.

There is a common misconception about heavy or big woofers must be “slow” and light or small woofers must be fast. The same thing goes for BL/Mms as an indicator of woofer speed/transient response. At first you think “yeah, that sounds about right!” but all of the latter is incorrect.

Breaking it down, force equals mass times acceleration (F=ma). A loudspeaker consists of what – a coil of wire which creates an alternating magnetic field which interacts with a static magnetic field in the gap coupled to a fixed amount of mass. Pass current though the voice coil and the coil moves. And as the current changes the voice coil moves in and out. So motor force (BL) times current (i) equals the moving mass of the driver times acceleration of the driver (a).

Now we have BLi=ma. Looking at this new equation we can see that:

BL is time invariant.

i is the current into the driver (music, test tone, etc) which is an AC waveform which changes with time.

m is mass and if this changes as you operate you have a BIG problem! Mass stays the same while in operation.

a is the acceleration. This is what we are after. The rate of acceleration is the transient response.

If we re-write the last equation using a “C” to indicate what remains constant you get:

Ci=Ca or i:: a (the “::” symbol is for proportionality), which shows that the change in acceleration of a driver is strictly a function of the current through the driver.

Looking back on the model of a loudspeaker you have a coil of wire wound on a former that attaches to the cone. What does a voice coil look like? How about an inductor? You know those things in crossovers that look like tiny voice coils? A voice coil IS an inductor! An inductor stores energy in the magnetic field. Inductors like to hold current. The higher the inductance the longer it can/will hold current flowing it, which means that the more time elapses before it starts to respond to the amplifiers applied voltage. AKA slower transient response.

Here is an impulse graph showing modifications to a speaker and how those modifications have impacted the performance of the driver. The red line is the raw driver. The other two lines are added mass and added inductance.

The blue is added mass. The green is with an inductor in series.

The green has delays in the negative and the positive.

And here is a graph of the frequency response:

 

[SPLaudio 5,000+ posts]

18s will play lower frequencys louder than a bunch of 8s with the same cone are

"18s are sloppy" i have heard this sence i been in the game mid 90s and its not true. back then there wasnt motors strong enough to really drive a 18" cone well. but really it was bad installs