I'm having some issues with a new subwoofer build. Here are some specs:
Subwoofer: Morel Ultimate UW 1058 10" sub, 500 W RMS, 1,500 W peak, 8 ohm.
Box: Sealed. Denovo Audio 1.25 cu.ft. knock down MDF box.
Amplifier: Crown XLS 2002 DriveCore, running bridged mono 8 ohm, 1,300 W
Wiring: 10 gauge solid-core magnet wire throughout.
I completed the build last night and fired it up. I'm having the following issues:
1) The output seems quiet. I'm coming from an 8" ported sub (150W) and I know sealed is less efficient, but I've gone up in cone size and speaker quality as well as significantly increased wattage and I think the 8" is as loud or louder. I'm having to turn up the amp all the way and even then the sound is not very impressive. The amp LED indicators show no clipping. This surprised me as the reviews for the Crown amps typically say they have more than enough wattage and people usually set the volume to about half, even with big 15" subs.
2) The bass is not very tight. My research, design and product reviews indicate that this would be a very tight sounding sub, but that's not what I'm hearing.
3) There is distortion of some sort. It sounds like the cone itself is making noise or a rattling sound. The amp does not show clipping. I've swapped the sub out and the issue persists. I'm hearing noise of some sort from the speaker well below reaching the xmax.
Troubleshooting:
1) I've rechecked wiring and system/amp setup.
2) I've tried switching from mono to stereo and just used one amp channel. Tried both the left and right channels.
3) I've bypassed as much as I can in the rest of the system to get the highest voltage signal from the RCA interconnect. The amp has an input setting for home audio gear (0.775V - High).
Nothing has seemed to help. A thought occurred to me today that the speaker terminals could be to blame. It's a custom made speaker terminal using threaded rod, washers, lock washers, and nuts. I've used this design on a speaker build and it seems to work fine (although it was a lower wattage system). I got to thinking about it more. The hardware is likely galvanized steel (zinc plated steel) which has a lower conductivity than copper. I figured it wouldn't matter too much since it's only a small portion of the speaker wire path and the threaded rod is thicker than my 8 gauge wire, but maybe I'm wrong. I've attached a photo of the terminals. The wire gets "crimped" between the two washers on both sides and the power passes through the hardware/threaded rod.
Can you guys help me troubleshoot this issue, please? Do you think my homemade terminals are to blame? Thank you!
Subwoofer: Morel Ultimate UW 1058 10" sub, 500 W RMS, 1,500 W peak, 8 ohm.
Box: Sealed. Denovo Audio 1.25 cu.ft. knock down MDF box.
Amplifier: Crown XLS 2002 DriveCore, running bridged mono 8 ohm, 1,300 W
Wiring: 10 gauge solid-core magnet wire throughout.
I completed the build last night and fired it up. I'm having the following issues:
1) The output seems quiet. I'm coming from an 8" ported sub (150W) and I know sealed is less efficient, but I've gone up in cone size and speaker quality as well as significantly increased wattage and I think the 8" is as loud or louder. I'm having to turn up the amp all the way and even then the sound is not very impressive. The amp LED indicators show no clipping. This surprised me as the reviews for the Crown amps typically say they have more than enough wattage and people usually set the volume to about half, even with big 15" subs.
2) The bass is not very tight. My research, design and product reviews indicate that this would be a very tight sounding sub, but that's not what I'm hearing.
3) There is distortion of some sort. It sounds like the cone itself is making noise or a rattling sound. The amp does not show clipping. I've swapped the sub out and the issue persists. I'm hearing noise of some sort from the speaker well below reaching the xmax.
Troubleshooting:
1) I've rechecked wiring and system/amp setup.
2) I've tried switching from mono to stereo and just used one amp channel. Tried both the left and right channels.
3) I've bypassed as much as I can in the rest of the system to get the highest voltage signal from the RCA interconnect. The amp has an input setting for home audio gear (0.775V - High).
Nothing has seemed to help. A thought occurred to me today that the speaker terminals could be to blame. It's a custom made speaker terminal using threaded rod, washers, lock washers, and nuts. I've used this design on a speaker build and it seems to work fine (although it was a lower wattage system). I got to thinking about it more. The hardware is likely galvanized steel (zinc plated steel) which has a lower conductivity than copper. I figured it wouldn't matter too much since it's only a small portion of the speaker wire path and the threaded rod is thicker than my 8 gauge wire, but maybe I'm wrong. I've attached a photo of the terminals. The wire gets "crimped" between the two washers on both sides and the power passes through the hardware/threaded rod.
Can you guys help me troubleshoot this issue, please? Do you think my homemade terminals are to blame? Thank you!
Attachments
What device are you driving the crown amp from?
What signal level are you seeing on the Crowns meters?
What if any crossover settings have you set in the crown or the upstream component?
My advice is remove all processing, these Crown amps have a non defeatble 20hz low cut filter IIRC so if for some reason you have the sub crossover at 30hz or 40hz there will be very little output.
If you are not seeing much signal level on the Crowns meters then either you have done something like above with the processing or you simply aren't getting much drive level from the upstream component. You should be able to drive the Crown into clipping.
Make double sure you have everything set and connected correctly for Bridged operation, speaker connected to the RED terminals only and follow instructions for menu selections and input controls.
Try running the sub directly connected to the amp with a piece of speaker wire out of the box. Start with the amp controls at zero and slowly raise them, you should be able to make the driver dance pretty good but don't go anywhere close to full power, if that works then your custom terminals are the problem. I doubt this is the case however I'd bet you have a signal level problem.
What signal level are you seeing on the Crowns meters?
What if any crossover settings have you set in the crown or the upstream component?
My advice is remove all processing, these Crown amps have a non defeatble 20hz low cut filter IIRC so if for some reason you have the sub crossover at 30hz or 40hz there will be very little output.
If you are not seeing much signal level on the Crowns meters then either you have done something like above with the processing or you simply aren't getting much drive level from the upstream component. You should be able to drive the Crown into clipping.
Make double sure you have everything set and connected correctly for Bridged operation, speaker connected to the RED terminals only and follow instructions for menu selections and input controls.
Try running the sub directly connected to the amp with a piece of speaker wire out of the box. Start with the amp controls at zero and slowly raise them, you should be able to make the driver dance pretty good but don't go anywhere close to full power, if that works then your custom terminals are the problem. I doubt this is the case however I'd bet you have a signal level problem.
The two sources I've tried are a portable CD player with a 3.5mm to RCA cable (definitely low power) and a desktop DAC with RCA cable (fair amount of output power).
The signal level I'm seeing is -20 db with a little flicker of the -10 here and there.
The only crossover is on the Crown. I've got it set to low-pass 85 Hz. I tried no crossover and high pass. The crossover circuit seems to be working.
If the only issue was low output, I would say the problem is low drive level and the answer is a pre-amp. The fact that I also have distortion going on and the bass is not tight at all makes me think there is another issue at play. If it was just low output, I don't know why I would get distortion, especially without the amp showing any clipping.
I will directly connect the sub to the amp tonight. Good idea! That's a good test to isolate the speaker terminals.
On another forum I read a discussion about undersized speaker wire (perhaps similar to my case if the problem is indeed the terminals). Someone said that high resistance in the wires leads to a larger voltage drop which means the amp has to push more current to maintain rail voltage. More current means more heat and more resistance and if the rail voltage sags too far, you get "flat topping"/hard distortion. Seems to make sense. I will report my findings later.
Thank you
The signal level I'm seeing is -20 db with a little flicker of the -10 here and there.
The only crossover is on the Crown. I've got it set to low-pass 85 Hz. I tried no crossover and high pass. The crossover circuit seems to be working.
If the only issue was low output, I would say the problem is low drive level and the answer is a pre-amp. The fact that I also have distortion going on and the bass is not tight at all makes me think there is another issue at play. If it was just low output, I don't know why I would get distortion, especially without the amp showing any clipping.
I will directly connect the sub to the amp tonight. Good idea! That's a good test to isolate the speaker terminals.
On another forum I read a discussion about undersized speaker wire (perhaps similar to my case if the problem is indeed the terminals). Someone said that high resistance in the wires leads to a larger voltage drop which means the amp has to push more current to maintain rail voltage. More current means more heat and more resistance and if the rail voltage sags too far, you get "flat topping"/hard distortion. Seems to make sense. I will report my findings later.
Thank you
OK that is good info but look at what it tells us. -20db down from the 1300w maximum output of this amp bridged into 8 ohms is 13 watts, -10db is still only 130w. Given that this driver has an 85dB sensitivity that won't produce a lot of sound particularly with sub bass frequencies but on the other hand it should be something similar to what you got from your other sub.
OK good there.
You definitely have a low drive level problem and you could also have a defective driver but don't just to any conclusions yet, sub bass all alone when there is a steep lowpass filter in use sounds really weird. Here is another test, hook up another driver to the amp and set things to get a moderate sound level, then without changing anything swap on the new sub driver. That isn't a definitive test because two drivers could have very different sensitivities and frequency response but it's a good comparison.
If you have a multimeter you could test the terminals for resistance, anything above a dead short means something is wrong.
Something else I just noticed... you said you used magnet wire inside the cab. Did you strip the ends of this wire where is connects to the terminals and speaker? This wire has a thin but very good insulating coating over it.
No that doesn't make any electronic sense unfortunately. An audio amplifier is first and foremost a voltage amplifier, increasing voltage gain(how big the output wave is compared to the input) is what you are doing when you raise the volume control. The current delivered to the load however is passive and totally dependent on the impedance of that load, everything inline between the amplifier terminals(wire, connectors, passive crossover components, and the speaker voice coil) affect it and the amp has no control over that. If impedance is higher due to really small gauge wires for example then less current and power is delivered, period. The amp cannot push more current but this should not produce any distortion unless gains are increased too much and somewhere along the signal chain something is clipped.
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You said in your OP that you "swapped the sub out and the issue persists"...can you elaborate on this? You mean you swapped it out for a different sub? you swapped it out for an identical driver? Just trying to get more info. Although I can't say I love your wiring scheme, I don't think that is your issue as long as you stripped the wire where you made connections and you are sure the wire itself is not rattling against something or contacting the moving parts of the driver as it is solid core.
I stripped the wire with 60 grit sandpaper until it resembled rough, raw copper.
Swapped it out for an identical driver and got the same problem. I double checked the wires and they aren't rattling against anything.
I just hooked up the sub directly, outside the box (bypassing the custom terminals) and I'm still getting the distortion. I've attached a video of the sub playing so you can hear and see it. Since I've ruled out the terminals and tested 2 subs, I'm thinking the issue is with the amp. However, I will test a completely different brand and model sub tomorrow just to make sure the issue isn't the sub. I can swap out the amp with a different one, but I don't think I have a low pass filter I can put in the chain. Will it hurt anything to send a full signal to the sub?
You can send a full-range signal to the sub just fine.
Push evenly on the sub's cone. Does it move in and out okay? It should feel completely smooth.
My suspicion here is that you're clipping something upstream of the Crown amplifier. Plug your phone/MP3 player into the amp directly, and raise the volume. How does that sound?
Chris
Push evenly on the sub's cone. Does it move in and out okay? It should feel completely smooth.
My suspicion here is that you're clipping something upstream of the Crown amplifier. Plug your phone/MP3 player into the amp directly, and raise the volume. How does that sound?
Chris
The movement seems fine - it's smooth and doesn't scrape on anything.
Updates:
1) I've tested a third sub and it made distortion as well.
2) Tested a 6x9 with the crossover - same noise. When I tested it full range, it sounded okay but I don't think I turned it up as much as I did for the subs or the 6x9 with the low pass.
Conclusion: The drivers are fine.
I also did a factory reset on the amp with no improvement.
Further testing: (feel free to recommend different tests if you see something I'm missing)
1) Change the RCA Cables
2) Change the power cord
3) Change the plug in location from power strip to wall.
4) Change the speaker cable.
5) Change the amp
6) Plug source directly into amp.
Are there any tests I can do with a multimeter that would help me out?
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My bet is your pre-amp is clipping trying to deliver enough level to drive the Crown amp properly.
Set off with the Crown amp volume wide open and turn the upstream component(s) down accordingly.
Chris
Set off with the Crown amp volume wide open and turn the upstream component(s) down accordingly.
Chris
I will try that and the other things later today. What about input and output impedances? I don't know much about those concepts. Is it possible the output impedence of my source doesn't play nicely with the input impedence of the amp?
Btw, my "pre-amp" is a Schiit SYS which is unpowered, passive - basically it's a potentiometer and an input selector.
You're getting good advice here, and your own efforts are spot-on as well. My money would have been on the Crown Factory Reset solving all troubles.
I kinda like your terminal solution, too, but gotta mention something. While it isn't likely to be part of the problem today, some months down the road it surely will. With probably 3 or 4 dissimilar metals -- metals having different electro-chemical activity -- humidity and other insults will eventually cause higher resistance.
Hope you get the break you need.
Rick
I kinda like your terminal solution, too, but gotta mention something. While it isn't likely to be part of the problem today, some months down the road it surely will. With probably 3 or 4 dissimilar metals -- metals having different electro-chemical activity -- humidity and other insults will eventually cause higher resistance.
Hope you get the break you need.
Rick
Just thought of something else -- how are the cables wired to connect the "pre-amp" to the Crown? Doesn't the Crown only have XLR inputs? I once almost completely blew a live gig with a rental crossover that drove pin 2, while my snake adapters at the amp 65 feet away were expecting signal on pin 3! (read 'deep professional embarrassment')
Rick
Rick
because your not using a true pre-amp, have you changed the input sensitivity to the "High" 0.775V mode through the menu guide? Just a thought, since I believe it comes set in the "Low/Normal" from the factory, which if you are using an RCA it would be very difficult to find anything that would drive the amp to full signal.
Hi, Have you been in bridge mode all along? Hooked up to the two hots?
If so, I'd go single channel since you're having so much trouble...eliminate one more variable.
I do not know that amp, but on a number of pro amps, it's necessary to turn Channel 2's gain all the way down when using bridge.
And Channel 1 should be the only one getting signal, whether you need to turn down 2 or not...
I agree with all who say turn amps gain up fully, and have input sensitivity set to High.
If so, I'd go single channel since you're having so much trouble...eliminate one more variable.
I do not know that amp, but on a number of pro amps, it's necessary to turn Channel 2's gain all the way down when using bridge.
And Channel 1 should be the only one getting signal, whether you need to turn down 2 or not...
I agree with all who say turn amps gain up fully, and have input sensitivity set to High.
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You guys are the best! Thank you for all the feedback. I'm still getting the hang of quoting people, so I'll reply like this: @mark100 - I have tried bridge mode and single channel, both right and left. I was actually confused as to which dial controls volume in bridge mode - I had just been keeping both at the same level. lol. @bullittstang - I have changed the input sensitivity to high 0.775 V. Does this setting mean consumer audio gear can drive this pro-grade amp? That was my understanding when I bought it. @Rick PA Stadel - It's connected with RCA cables. The Crown does have RCA inputs. Maybe the older models didn't. This is the newer model Crown XLS DriveCore 2 Model 2002. I've ran some more tests and have some interesting results. I'll share the most surprising ones: 1) I've swapped (or removed) most every component: RCA cables, pre-amp, speaker wires, power cables, changed wall outlets, source, etc. None of this helped. 2) I swapped the Crown amp for a Schiit Vidar... the distortion didn't go away! 3) I directly connected a portable CD player to the Vidar and drove the sub. This really seemed to help. I did the same with the DAC and got improvements as well. The conclusion I drew from this is that my line levels are far too low. Where I'm confused is that the Vidar is consumer-grade audio equipment and I wouldn't expect it to have the same problem as the pro-grade amp. Furthermore, I would expect low line levels to only produce low output levels, not audible distortion. Perhaps the line levels are so low that when they are amplified, the background noise in the signal is amplified to audible levels??? What really confuses me is that I can drive speakers with the Vidar with no problems and no distortion. Why is the sub any different? Do these conclusions make sense? What's the solution? A powered pre-amp? Any suggestions? A final note: when I was driving the sub outside the box, the holes in the voice coil were moving a lot of air. When inside the box and driven to higher levels, the sub made sort of a chuffing noise. Maybe this is related to the original problem and will go away with proper signal strength... Has anyone ever experienced this before?
Sorry for the poor formatting. I tried to edit it with line breaks but I can't figure out how to do that.
A follow up: I added a line-level booster between my DAC & volume control and my Crown amp that powers my sub: iBoost 800 Stereo Line Level Audio Amplifier. This seems to have taken care of my problem with the sub/amp having low output and the sub producing distorted sound. I keep the line level booster on high and control the sub volume with the Crown amp.
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