Hello, I have a subwoofer installed in my vert and i noticed that when i crank up the bass on the subs when playing a song, there is latency issue with the bass. In other words the bass coming from the subs don't sync with the song (or when the bass is supposed to kick in). The delay is pretty noticeable when cranked up high. I have an amp on the sub box. I DO NOT however have an equalizer, capacitor, or cross-fader installed. Any inputs on why this happens? Thanks!

 

4eva 27,

Based on the limited information provided, it sounds like you may need more power, and perhaps a 1 Farad cap (you can get these online for under $50, and they help protect your battery and alternator as well), especially if you notice your headlights or interior lights dimming. It may not be necessary to mention, but 4-gauge is probably the thinnest amp cables you should be using if you're pushing a sub. And it would beneficial to add another short 4-gauge (or higher) ground cable from your battery to a solid part of the chassis. This helps get more electrons to your amp. If you're not running a sealed battery (such as my Optima Yellow Top), remove the caps and make sure the battery wells are filled up to the bottoms of the plastic tubes with distilled water. You get lower voltage and a higher strain on the alternator if the water's low. It's also important to make sure the woofer is sealed against the box using a rubber or foam gasket. A lot of car audio installers simply screw down the woofer against the box carpet, which doesn't produce an airtight seal, resulting bass with unusual characteristics.

To elaborate...

To answer your question in normal-sounding terms, when the amp receives the bass signal, it attempts to push the sub against the centering force of the voicecoil(s) and against the air ("spring") in the box. The initial moving of the cone against these equilibrating forces requires the most energy (An object at rest etc...), and with each oscillation (in-and-out movement of the cone), the amp is able to increase the woofer's excursion. With inadequate power, in attempting to reproduce a 1-second bass note, the first 0.3 seconds won't as audible as the later 0.7 seconds, giving you the audio illusion that your bass is delayed and not keeping up with the rest of your system.

As an analogy, imagine standing along side, and then pushing a girl on a swing. During the first push, you're only able to push her forward over a distance (actually it would be called a "sector," but we don't need to be that technical ) of 3 feet from the starting point (equilibrium). Then on the second push, you're now able to push her 5 feet from equilibrium. On your third push, she now travels 6 feet from equilibrium. In this example, it's the restoring force of gravity that's assisting you in the displacement of the swing; For your subwoofer, it's the restoring forces of the voice coil(s) and the increases and decreases in air pressure in the box that assist the amp in moving the cone back and forth. If you had enough power (i.e. watts) you would have been able to push the girl 6 feet on just the first push.

Over the range of woofers from 8" to 15" - and I've installed all these sizes - it's easier to get tighter bass to keep up with your music by using the smaller woofers for the reason that obtaining tight bass from larger woofers requires a exponentially increasing amount of RMS power. Assuming the same excursion, getting a 15 to punch out and recoil back as fast as a 10 might require three times the power, since the 15 has to push more air, its cone weighs more, and its voice coils are tighter to control the heavier mass (not to mention that a 15's cone will flex more than the same woofer in a 10" size, which also somewhat affects sound quality). So given 300 RMS, a 10 will be very tight and controlled, but it can't compete with a 15 and 600 RMS in reproducing the lows on a song like Young Jeezy's "Put On," for example. But 600 RMS still might not be enough to get the 15 to be as tight as a 10 with 300 RMS.

Box size is also a consideration. Following the manufacturer's recommended internal volumes (no need to overanalyze the Thiele-Small measurements), the smaller boxes will produce tighter bass and allow you to push more power into the woofer without overexcursion. As a general rule, I like a sealed box to be just slightly larger than the smallest recommended enclosure. I prefer to install amps with setups where 80% of the amp's rated RMS output corresponds to the woofer's maximum RMS power handling. I never run amps at full gain, nor push full "rated RMS" into a subwoofer (for longevity reasons) but this is my preference to ensure that the amp can consistently maintain high power without breaking a sweat, and that you're extracting the right amount of performance from your subs without overheating the voice coils.

(I had some caffeine earlier)

 

Good god that was thorough, but excellent, precise, and very useful information. Thank you very much.
Here are the specs on my setup:

-4-gauge ground cable amp to chassis
-Lights do not dim
-If I remember correctly, the sub came with a thin layer of foam, thin as in about 1-2mm.

Earthquake Sound Amp TNT Series 2000 Watt Monoblock Class D
Max Power: 2000 Watts
2 Ohm RMS Power Mono: 1000W x 1
Input Sensitivity: .2mV- 6V
Signal To Noise Ratio: >104dB
Frequency Response: 10Hz-400Hz
Lowpass X-Over Frequency: 50Hz-300Hz
Bass Boost: 0dB-10dB
THD @ 4 Ohm Rated Power: <0.01%
THD @ 2 Ohm Rated Power: 0.016%
Fuses: 2- 30 amp
Capability: 2 Ohm Mono
Dimensions: 2 3/8" x 9 3/4" x 13 3/8"

Rockford Fosgate Punch P3 10-Inch 400-Watt Subwoofer - 4 Ohm
Size: 10"
Impedance: 4-Ohm x 2
Power Handling: 400 Watts RMS
800 Watts Max
Voice Coil Diameter: 2.5" 4-Layer (6.35 cm)
Motor Size: 78 oz. Double Stacked
Speaker Connector: Dual 10 AWG compression
SPL(1w/1m): 83 dB
Woofer Displacement: 0.074 cu. ft. (2.10 Liters)
Cutout Diameter: 9.0 in. (22.86 cm)
Mounting Depth:6.25 in. (15.56 cm)

The sub box looks like this:



Thanks again!!!

 

In my experience, it's easier to build a tight-hitting ("responsive" for lack of a better term) sealed box than a tight bandpass (ported) box. Bandpasses are leveraged toward providing loud boomy bass with as little as 50 RMS watts, although the bass does sound like it can't keep up with the rest of the system (I'll spare you the explanation on this one) Sealed boxes are always smaller and require more power (not a problem in your case) for the same loudness, but have a wider bass range and you can more easily identify the different bass tones. Equalizers help lessen the differences between the two boxes, but there's no changing the laws of physics.

Class D amps are more efficient and generally smaller than class A amps. The only real tradeoff is the damping factor is less compared to Class A amps, although realistically it's hard to tell the difference *in bass* unless you plug in a 400-watt Earthquake Class A, then swap it out for a 400-watt Earthquake Class D.

I'd first add another ground, and a cap to make sure your amp always has a reservoir of electrons at its disposal during those bass hits. After that, you might consider putting the woofer in a sealed box. I'm currently using two high-excursion stacked magnet 10s in 0.6 ft^3 sealed enclosures each with only about 225 RMS each, and there's no "delay." I'm not using a cap, although my amp is sitting right next to my Optima Yellow Top (awesome battery btw) in the trunk, and even with my E-shaft underdrive pulley, my lights don't dim even at night in traffic.

Had more caffeine again. Reviewing for my MCAT in March

 

Cool thanks again for good info. I'll add another ground , a cap and a sealed box like you said then. I have an FD alt and Yellow Top Optima waiting to be installed as soon as it warms up in NY. And good luck on your exam!

 

I used to have an alpine head unit that had the ability to add time delay to the speakers individually, and also the subs. Using the settings you could make the front speakers sound like they were each the same distance away from you, and also tune the subwoofers to hit at the same time as the surround speakers.
Sounded very good when I finally got the hang of tuning the time delay correctly.