FastAP2

Hey everyone.
I recently installed two JL w3v3's with a Rockford R1200-1d in my car and it feels a little lacking. I was wondering if anyone has any suggestions for getting more "punch in the chest" bass feeling.
The subs are in sealed boxes and I also installed dynamat in the trunk. And I have the alpine cde-hd149bt head unit.
Maybe different amp?

windhund116

Geez, 1200 watts should be enough. You sure the two speakers in the trunk, are in phase with each other? And their impedance matches the amp's output impedance?

One thing I did do in some setups, was to add a "choke and storage cap" pi-filter to the power supply input. I'd get surplus mil spec or commercial grade electrolytic caps (like 10,000+ mfd/ 50 or 100 VDC monsters) and put two in parallel with a choke in between. This LC circuit added filtering and boost transient power to the SW amp. I used to wind open-air-core chokes to 100mH (or so), rated to 25 amps. Then, place it in series... with two 10,000 mfd/50 VDC 'lytic caps, in parallel (to ground). With the power to the SW amp tapping off the second cap's (+) end. Kinda like the picture, but with two caps in parallel and choke in between. The cap's really added to the bass, esp during heavy bass runs or transients.

One thing to be cautious... those cap hold a LOT of energy, once charged up. And they will hold onto that power, long after the power supply has been turned off. So, watch tools and contacts! I usually covered all points with shrink wrap & silicone sealer on the cap's screws.

modifry

Just to be clear, the above diagram is not a "pi-filter". In order to be a pi filter you would have to put a second capacitor at the far left, between the battery and choke. What is drawn is an LC filter, but you should understand that the "L" part of the filter will actually limit "transient" power to the amplifier. Circuits like this are generally used to minimize alternator noise from getting into the power supply of the amplifier or head unit. The choke passes pure DC with very little resistance but will impede AC or fast pulses of DC current. The choke and cap are actually fighting each other if your goal is to increase power. You are better off getting an amp with more power, using larger power cables, or installing a bigger alternator. A 1200 watt amp will draw around 150 amps at full power. The S2000 has a 90-amp alternator. Hmmm.

Think about the definition of a Farad - "one Farad can supply one amp of current for one second with a 1-volt drop in voltage". So assuming you don't want the voltage to drop by more than 1 volt, your 10,000 uf capacitor (.01 Farads) can supply 1 amp for 1/100 of a second, or 10 amps for 1/1000 of a second. Is that really doing you any good? It won't even supply a single cycle (.02 seconds) of a 50-Hz bass note.

For Fast AP2 - I know nothing about the speakers you are using as I have no desire to damage my internal organs with chest-thumping bass. But you might want to double-check the cut-off frequency of the cabinets; they look pretty small in the photos. I assume you're using AWG 2 or 4 for amp power?

FastAP2

Wow thanks for the responses! Modifry I am using 4 awg wire for the amp. I'm looking for different amps seeing as there's a ton of reviews saying the lower end Rockford prime series doesn't perform very well. As for the cut-off frequency how would I check that?

osu1978

A few of the things that could be wrong:
- Speaker phase is incorrect.
- Enclosure size is out of spec.
- The amp and speakers are not wired/configured properly.
- Your head unit may be cutting out bass frequency via the EQ.

One thing I do know is that your setup should yield plenty of chest thumping bass. What do you have in the doors?

modifry

Check phasing first, as it's easy to do. Disconnect one speaker and see if the bass gets louder or quieter. If running on one sub is louder then reverse the wires on the speaker you just disconnected. Of course be careful with the wires to make sure they don't touch anything when you're doing this test.

Checking the cut-off frequency will either require some sophisticated testing gear or speaker design software to tell you how big the cabinet should be. As osu1978 mentioned, cabinet size is critical and can make a good speaker sound bad. You may be able to get a rough idea of cut-off frequency by using a test CD or a smart phone app to play low-frequency tones through the system. Look for a test that "sweeps" the frequency from maybe 150-200 Hz down to 20 Hz and listen for when the volume drops significantly. Bear in mind your system might have a high frequency cut-off of 100 or 120Hz, so if you do a 200Hz and down sweep the volume will be lower at 200, get louder around 100 or just below, and then maybe drop again as the frequency goes down. You want to compare the loudness of the 40-60 Hz range with the loudest part of the sweep. I would think the 40-60Hz range should be the loudest part of the sweep. If it's not it sounds like the enclosure might not be the best size for the speaker.

You may also be able to check on-line and see if the speaker manufacturer provides optimum cabinet volumes for their drivers. Many do. Look for the size they recommend for a sealed system and if yours is more than 20% smaller it might be the problem.

windhund116

Sounds like phasing or severe impedance mismatch, to me.

Yes Modifry, I used two caps in parallel with the choke, in series, in between the two. You know, good caps really help the bass (esp bass transients) by adding reserve power. So, the current draw isn't solely limited to battery supply. I'm surprised you haven't done this to your SW setups. It's an old trick I learned from a tech at Crystal Sonics. They used to be in Glendale, CA. The parts are cheap. You can get 10-20K mfd/50VDC caps from surplus mil spec or computer supplies, for $10-20 apiece. I wrapped the choke with single-strand enameled copper wire (like 18 or 20 gauge) around round plastic wire bobbin. Similar to wrapping chokes for speaker crossovers.

Anyhoo, I digress. Here's a better schemo...

FastAP2

Ok so I checked out the different suggestions you guys gave.
-head unit is set correctly. Not cutting out low frequency to the subs.
-checked wiring from amp to subs and everything is where it should be. I have two 2ohm subs wired at 1ohm.

-I'm thinking it has to do with enclosure size. JL recommends sealed enclosure of .625cf and I have them in .38cf boxes...

modifry

I have done it, but I used a scope to measure the results instead of the most inaccurate audio test meter in the world (the human ear). And that's why there are no big caps in my subwoofer system.

And I am familiar with "old tricks", including those that defy the known laws of physics.

modifry

Is that .38cf before installing the woofers, or after taking into account the volume taken up by the woofer cone and magnet? If the JL recommendation was the smallest box you could use for adequate performance then you could be on the other side of the "sweet spot". If, however, the .65cf was for optimum Q, and your .38cf is net, I don't think it would be a dramatic difference. But it might be worth cobbling together a .65cf box and throwing it in the trunk as a reference point, compare it (by itself) with the other sub (by itself).