Why is the volume of my sub so quiet with my new Crown amp?

[Inertia]

I just hooked up my Crown XLS amp to my sub in bridge mode with RCA cable and I had to turn the volume for my sub all the way to +10 on my receiver and the gain on the Crown almost all the way up to hear the bass thump good like it was with my plate amp. I have an 20hz high pass Fmod hooked up to the sub cable before the amp in case that might matter. Anyone know what I need to do? Thanks for your time!

 

[tcarcio]

Your reciever might not be putting out enough voltage from your sub-out to power the amp to it's full potential. Usually pro amps need at least 1.4v of input to work correctley. That is why some use an Art cleanbox or a samson s-convert to go in between your reciever and amp. The samson has been discontinued and is harder to find but the Art cleanbox is still available. Also look at your manual of your reciever as some have the ability to adjust their output voltage.

 

[DS-21]

Also, your plate amp probably had some low-end boost built in. So even though its limits were lower, it put out more power down low at low volumes.

 

[TLS Guy]

I just hooked up my Crown XLS amp to my sub in bridge mode with RCA cable and I had to turn the volume for my sub all the way to +10 on my receiver and the gain on the Crown almost all the way up to hear the bass thump good like it was with my plate amp. I have an 20hz high pass Fmod hooked up to the sub cable before the amp in case that might matter. Anyone know what I need to do? Thanks for your time!

Your crown amp requires 1.25 volts for full modulation. What is the LFE output from your receiver?

You are aware that in bridged mode those amps must see an 8 ohm load? Not many subs are 8 ohm. If the impedance is less, serious damage can occur. You might be sending your amp into restricted current protection mode, in fact this is probable. Also the channels must be matched perfectly in terms of volume at all times, as otherwise serious damage can occur. The best plan is to fully advance both volume controls and hope the amps are perfectly matched. (They usually are not). Any difference in output between channels raises distortion through the roof, as the sine wave is then asymmetric. If this wave becomes too asymmetric due to channel imbalance, one or more channels may blow, and quickly.

I would unbridge the amp and test it, to make sure both channels are still working. You may already have blown a channel and if one side is down, you will just get reduced distorted output.

In general bridging amps is a bad idea and not recommended for most situations. Many amps go to amp Heaven after injudicious bridging set ups.

 

[DS-21]

You are aware that in bridged mode those amps must see an 8 ohm load?

Actually, Crown quite clearly rates the whole XLS Drivecore line down to 4Ω bridged mono.

Never mind that most "4Ω" subwoofers are actually well above that for most of the relevant passband.

And even a nominally "3Ω" load like the JBL W15GTi in parallel is in real life a ≤4Ω load in the relevant passband.

In general bridging amps is a bad idea and not recommended for most situations.

That's silly generally, but especially when one's talking about modern Class D chip-amps in 2012. The kinds of mismatches one often saw with discrete parts just do not happen when both channels are on the same chip.

So bridging in and of itself is toweringly unlikely to be the issue here.

His issues (unless one amp's gain knob is set very different from the other) more likely than not stem from one of three things, in the order I consider them likely:

(1) Bass boost built into the plate amp, not replicated with an external processor here.
Solution: a miniDSP (balanced version, to get enough output), Berry DCX, or similar processor to contour the frequency response. (That will also allow removal of the Fmod.)

(2) Insufficient signal levels going into the Crown amp
Solution: a Samson S-Convert, modified Art Cleanbox, or other bump box to get signal levels up.

(3) A wiring error somewhere, possibly including a bad interconnect.
Solution: basic troubleshooting. Verify that the amp is wired properly for bridged operation, that the sub is wired for the correct impedance (if it worked on the plate, it should be fine here), that none of the interconnects are dodgy, that you're not using one of those Monoprice RCA-XLR cables (most of them seem to be miswired), etc.

Also, maybe the Fmod is dodgy. Try running without it.

 

[lsiberian]

I think it's the Fmod most likely. I'm sure you've tried it without the fmod to see if it works though.

 

[TLS Guy]

Actually, Crown quite clearly rates the whole XLS Drivecore line down to 4Ω bridged mono.

Never mind that most "4Ω" subwoofers are actually well above that for most of the relevant passband.

And even a nominally "3Ω" load like the JBL W15GTi in parallel is in real life a ≤4Ω load in the relevant passband.



That's silly generally, but especially when one's talking about modern Class D chip-amps in 2012. The kinds of mismatches one often saw with discrete parts just do not happen when both channels are on the same chip.

So bridging in and of itself is toweringly unlikely to be the issue here.

His issues (unless one amp's gain knob is set very different from the other) more likely than not stem from one of three things, in the order I consider them likely:

(1) Bass boost built into the plate amp, not replicated with an external processor here.
Solution: a miniDSP (balanced version, to get enough output), Berry DCX, or similar processor to contour the frequency response. (That will also allow removal of the Fmod.)

(2) Insufficient signal levels going into the Crown amp
Solution: a Samson S-Convert, modified Art Cleanbox, or other bump box to get signal levels up.

(3) A wiring error somewhere, possibly including a bad interconnect.
Solution: basic troubleshooting. Verify that the amp is wired properly for bridged operation, that the sub is wired for the correct impedance (if it worked on the plate, it should be fine here), that none of the interconnects are dodgy, that you're not using one of those Monoprice RCA-XLR cables (most of them seem to be miswired), etc.

Also, maybe the Fmod is dodgy. Try running without it.

The OP said it was an XLS. On the data sheet I found only the XLS 5000 is bridgeable into 4 ohms. If he has a Drivecore amp, that is a different issue.

I see can find no information that these amps are class D, and have no experience bridging class D amps. However I have seen trouble a plenty bridging everything else. A more powerful monoblock is a much preferable solution.

It would be interesting to find out exactly what he is driving with that amp.

The OP now has an O audio Bash 500 watt plate amp for sale, so I suspect that is what he was using. It has no built in bass boost, but does have parametric Eq, and I know not whether the OP was using it.

 

[lsiberian]

The OP said it was an XLS. On the data sheet I found only the XLS 5000 is bridgeable into 4 ohms. If he has a Drivecore amp, that is a different issue.

I see can find no information that these amps are class D, and have no experience bridging class D amps. However I have seen trouble a plenty bridging everything else. A more powerful monoblock is a much preferable solution.

It would be interesting to find out exactly what he is driving with that amp.

The OP now has an O audio Bash 500 watt plate amp for sale, so I suspect that is what he was using. It has no built in bass boost, but does have parametric Eq, and I know not whether the OP was using it.

I don't recommend bridging amps either because it can complicate issues.

He has two custom ported builds and will be driving two JL Audio 12w7s in them. He certainly didn't have or use a boost.

 

[TLS Guy]

I don't recommend bridging amps either because it can complicate issues.

He has two custom ported builds and will be driving two JL Audio 12w7s in them. He certainly didn't have or use a boost.

Those drivers are three ohm.

He should have plenty of voltage to drive the Crown. LFE line out is a volt at specified input modulation. That 0.25 volt short to his Crown 1.25 volt is not even a db.

So there is either a wiring fault. If no wiring fault, then the amp is in current protected output mode, or already damaged on my view.

If damaged it is not the manufacturers fault.

 

[Inertia]

The sub plays loud with the gain knob around 3 o clock and it does not go into the red clipping! But I expected the output at 3 o clock to be closer to the 12 o clock position! Would I be better off buying one Crown XLS2000 or two XLS1000's? And I only had a few minutes to check out the sub/amp so did not try without the fmod.... Here are specs for the Crown XLS1000 it says its 4ohm mono stable:


Specifications
- Total Harmonic Distortion (THD): < 0.5%
- Intermodulation Distortion (IMD): (60Hz and 7kHz at 4:1), From full rated output to -30dB: <0.3%
- Damping Factor (8 ohm): 10 Hz to 400 Hz: > 200
- Crosstalk (below rated 8Ohm power): At 1kHz: > 85dB, At 20kHz: >55dB
- Input Impedance (nominal): 20 kOhm balanced, 10 kOhm unbalanced
- Load Impedance: 2 to 8 Ohm per channel in Stereo, 4 to 8 Ohm in Bridge Mono
- AC Line Voltage and Frequency Configurations Available (+/- 10%): 120 VAC 60 Hz
- Ventilation: Flow-through ventilation from front to back
- Cooling: Internal heat sinks with forced-air cooling for rapid, uniform heat dissipation
- Air Volume Requirements (per minute per unit): 80.15 ft

Minimum Guaranteed Power (per channel, both channels driven)
- Stereo, 2 ohms: 550W
- Stereo, 4 ohms: 350W
- Stereo, 8 ohms: 215W
- Bridged mono, 4 ohms: 1100W
- Bridged mono, 8 ohms: 700W Dimensions and Weight in PackagingBase ItemShipping Weight: 14 lbs

 

[TLS Guy]

The sub plays loud with the gain knob around 3 o clock and it does not go into the red clipping! But I expected the output at 3 o clock to be closer to the 12 o clock position! Would I be better off buying one Crown XLS2000 or two XLS1000's? And I only had a few minutes to check out the sub/amp so did not try without the fmod.... Here are specs for the Crown XLS1000 it says its 4ohm mono stable:


Specifications
- Total Harmonic Distortion (THD): < 0.5%
- Intermodulation Distortion (IMD): (60Hz and 7kHz at 4:1), From full rated output to -30dB: <0.3%
- Damping Factor (8 ohm): 10 Hz to 400 Hz: > 200
- Crosstalk (below rated 8Ohm power): At 1kHz: > 85dB, At 20kHz: >55dB
- Input Impedance (nominal): 20 kOhm balanced, 10 kOhm unbalanced
- Load Impedance: 2 to 8 Ohm per channel in Stereo, 4 to 8 Ohm in Bridge Mono
- AC Line Voltage and Frequency Configurations Available (+/- 10%): 120 VAC 60 Hz
- Ventilation: Flow-through ventilation from front to back
- Cooling: Internal heat sinks with forced-air cooling for rapid, uniform heat dissipation
- Air Volume Requirements (per minute per unit): 80.15 ft

Minimum Guaranteed Power (per channel, both channels driven)
- Stereo, 2 ohms: 550W
- Stereo, 4 ohms: 350W
- Stereo, 8 ohms: 215W
- Bridged mono, 4 ohms: 1100W
- Bridged mono, 8 ohms: 700W Dimensions and Weight in PackagingBase ItemShipping Weight: 14 lbs

So you don't have the standard XLS but the XLS Drivecore, correct?

You should advance both controls on the Crown amp fully clockwise, as this is most likely to balance the amps the best. Control you sub level, by correctly setting the LFE out on your receiver.

If you are planning to run two 3 ohm subs, then one XLS 2000 one channel to each sub, will be far preferable to two bridged amps.

 

[adwilk]

If you are planning to run two 3 ohm subs, then one XLS 2000 one channel to each sub, will be far preferable to two bridged amps.

I believe you, but I'd be curious to hear the explanation???

 

[DS-21]

A more powerful monoblock is a much preferable solution.

Don't see why. Bridging works just fine. Especially for subs, where what matters most is voltage swing.

The OP now has an O audio Bash 500 watt plate amp for sale, so I suspect that is what he was using. It has no built in bass boost, but does have parametric Eq, and I know not whether the OP was using it.

Actually, depending on the setting of the highpass filter, the Oaudio amp can have considerable low end boost. See manual, at 12.

 

[lsiberian]

You should get plenty of SPL with one channel per sub. If you need more I recommend upgrading the amp to a Yamaha P7000.

I realize bridging can be fine, but I'm very conservative when it come to my subs, and amps. 1 channel will give you plenty of power and a second channel will only net you 3 more db at most.

Remember these drivers don't necessarily bottom before they blow so take it easy this is an extremely low distortion driver capable of great output, but it won't give you the warning the infinity did if you are cranking it too much.

I don't use the full gain control on my amps for subwoofers. Adjusting levels with the knob is sufficient for the home user.

 

[TLS Guy]

I believe you, but I'd be curious to hear the explanation???

You have to understand what bridging is. The input goes to a phase splitter and then +ve deflections go to one amp and -ve to the other.

So the amps have to be perfectly matched otherwise +ve and -ve deflections are lopsided and that equals distortion. Bridging halves the speaker impedance the amp sees, so there is a stress right there.

The next issue is reliability. In a situation like the OP has with two subs if he bridges he will have four power amps, whereas with two unbridged amps he will have two less stressed power amps. So he has over a 100% increase in the chance of a failure.

I don't and won't recommend bridging as a first choice option and would personally never select it from an engineering standpoint.

 

[GranteedEV]

These are pro amps, designed to take abuse. You should see some of the testing Crown does to them.

Crown I-Tech Amplifier Drop-Test - YouTube

Beyond that though, they have fans which kick in at high stress levels. If OP hasn't even triggered the fans, then obviously he's not even pushing the amps near their limits.

See also:

Crown DriveCore

Anyways all of that aside, I suspect what's happening, is that OP was used to his older amp making clipping "boom" and the drivecore is just too clean to be heard.

 

[Inertia]

I am going to get one single XLS2500. I do not have the XLS1000 drive core. Where do you get the drive core amps they are not at zzounds I dont think. What are the differences between XLS and drive core? The fan has never kicked on my use.

 

[GranteedEV]

I am going to get one single XLS2500. I do not have the XLS1000 drive core. Where do you get the drive core amps they are not at zzounds I dont think. What are the differences between XLS and drive core? The fan has never kicked on my use.

The XLS 1000 / 1500 /2000 / 2500 are drivecore.

the older XLS x02 qmps are not.

 

[Inertia]

I have an XLS2500 on the way! I hooked up one JL audio W7 to my simple Kappa Perfect build and the W7 completely blows away the Kappa perfect VQ. Not even in the same category. SQ is better and at much higher SPL levels! Can't wait to hear these bad boys in a 5.25ft3 tuned at 20hz where they belong! The Crown is loud but still at about 3 o clock position. I have a Samson S-Convert in trade with some cash on the way for my old O audio BASH 500 watt amp.

 

[TLS Guy]

I have an XLS2500 on the way! I hooked up one JL audio W7 to my simple Kappa Perfect build and the W7 completely blows away the Kappa perfect VQ. Not even in the same category. SQ is better and at much higher SPL levels! Can't wait to hear these bad boys in a 5.25ft3 tuned at 20hz where they belong! The Crown is loud but still at about 3 o clock position. I have a Samson S-Convert in trade with some cash on the way for my old O audio BASH 500 watt amp.

That was a smart decision to get the XLS2500.

I'm going to post the design you plan to build. I see you are going with the ported alignment, which require less amplifier power, but a large cabinet.

I'm posting the model I did for you for the W12-7AE


I'm also posting the sealed model.

That driver actually favors a sealed model, however if you don't mind the large enclosures and it will run over 5 cu.ft, with port, driver displacement and bracing, then you will have prodigious bass output.

The driver has high power handling and high xmax. It would give a tighter bass, albeit with lower output in a sealed enclosure of 1.5 cu.ft.

Eq would have to be applied 12db per octave starting at around 60 Hz. That driver would tolerate that Eq. Qt would be around 0.6 giving a tight bass with little if any blooming. You will get some blooming on the ported alignment as this is a relatively high Qt driver.

As I explained to you the port of the vented enclosure is so long that this sub will need crossing over at 60 Hz fourth order to avoid exciting the port resonance.

This will be an exciting build. You will have large cabinet walls so you design will have to include obsessional bracing, just like the kappa build of Aversvi's. Keep us posted.