Magnum 12 MBM not what I'm expecting (so far) - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 84 Old 08-02-2018, 08:44 PM - Thread Starter
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Magnum 12 MBM not what I'm expecting (so far)

EDIT: There were 2 issues: 1) the XLS voltage of .775 doesn't play nice with some AVR's. I purchased a CleanBox and that fixed it immediately. 2) I had the Mag tuned to about 60 and once I tuned it to 43ish Hz it sounds GREAT!!!

CC: @Erich H

So I built a 1.2 cuft box for some DIYSG magnum 12's tuned to approx 45hz with a 300W 8Ohm Crown XLS2002 amp. It seems that I have to run it at max gain just to keep up with my mains during calibration which are Paradigm Prestige F75's (5" cones). The cone barely moves too.

When I'm at max gain I have some feedback or noise. Thoughts on why I need to run this at Max gain? I currently have 2 zip ties in the speaker holes so I can remove the speaker until I'm done veneering and screwing around. Would that "broken airtight seal" kill the volume that much.

I'm running the amp in .775V mode which is what I think I'm supposed to do. How can I get rid of that noise? I put a 3 prong to 2 prong adapter to limit the ground. I get that it's a high sensitivity 99.5dB driver so I'm not 100% surprised of the noise at max gain, but I feel at max gain it should be way out of proportion with my fronts not just keeping up.

Also, for my tests I was running at -25dB. I wanted to see if I could have the sub (MBM) run way way hotter than my fronts. I have the AVR at +6dB for the sub (MBM) and it's just keeping pace.

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post #2 of 84 Old 08-02-2018, 08:53 PM - Thread Starter
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Modeled in this box this driver should be able to hit 105dB at 33Hz and hit reference 115dB at 55Hz.
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post #3 of 84 Old 08-02-2018, 08:55 PM - Thread Starter
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correction the XLS2002 can do up to 375W at 8 Ohm!

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post #4 of 84 Old 08-02-2018, 09:21 PM
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What did you do to set it up/integrate it?

You need to get in alignment with your other speaker. Time/distance and polarity wise. Not sure if the amp your using is like some that reverses polarity like the Inuke and my Sunfire amp flips it 180 when using XLR vs the RCAs.

Edit looking at a pic online of the back of the amp and the XLR pinout it looks like it will reverse the polarity just the Inuke and my Sunfire since they wire it the same using the 3 pin as negative. That is the current standard for XLR.
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post #5 of 84 Old 08-02-2018, 10:11 PM - Thread Starter
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Originally Posted by bscool View Post
What did you do to set it up/integrate it?

You need to get in alignment with your other speaker. Time/distance and polarity wise. Not sure if the amp your using is like some that reverses polarity like the Inuke and my Sunfire amp flips it 180 when using XLR vs the RCAs.

Edit looking at a pic online of the back of the amp and the XLR pinout it looks like it will reverse the polarity just the Inuke and my Sunfire since they wire it the same using the 3 pin as negative. That is the current standard for XLR.
At this point I’m not looking to integrate it. I just want to run it hot and loud to test them.
Running at Max gain shouldn’t they be abnormally loud and not blend well? When I turn up the gain on my other subs to almost max it’s in appropriately and noticeably hot. I have them turned off as well as room correction for my experiment
I did switch the wires and it got a bit louder. I wonder if I use better speaker wire. I’ve got 16 gauge on there now. It was just some spare test wire I had

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post #6 of 84 Old 08-02-2018, 10:12 PM - Thread Starter
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Originally Posted by bscool View Post
What did you do to set it up/integrate it?

You need to get in alignment with your other speaker. Time/distance and polarity wise. Not sure if the amp your using is like some that reverses polarity like the Inuke and my Sunfire amp flips it 180 when using XLR vs the RCAs.

Edit looking at a pic online of the back of the amp and the XLR pinout it looks like it will reverse the polarity just the Inuke and my Sunfire since they wire it the same using the 3 pin as negative. That is the current standard for XLR.
I should note I’m using RCA

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post #7 of 84 Old 08-02-2018, 11:49 PM
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Do you have a mic and REW? If so do some measurements and check your dsp settings.
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post #8 of 84 Old 08-03-2018, 12:04 AM
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You need to set them up like you would any speaker or sub you add to a system(distance,x-overs, eq etc).

Have you tested just the 12" alone and took some close mic sweeps with REW to see what it is actually doing as far as FR and SPL? That is what I would do so I could see what the speaker is actually doing and see some numbers and then go from there if you think it is lacking output.

And yes it will affect output if you have air leaks around the speaker where the zip ties are holding it up from making an airtight seal.

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post #9 of 84 Old 08-03-2018, 12:16 AM
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I should note I’m using RCA
If you are using RCA to XLR it still flips polarity since the amps XLR pinout is opposite of RCA. You can check for yourself using REW and looking at the impulse.

Edit I see your amp has RCA inputs also. So nevermind my comment about the XLR. I would still check if the RCA on it gives you the same polarity as all of your other speakers. You will need to know this eventually anyway as you usually want all your speakers to have the same polarity.

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post #10 of 84 Old 08-03-2018, 02:44 AM
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Sounds like you need to buy a Cleanbox Pro:
https://www.parts-express.com/art-cl...erter--245-868
I have 3 of these, they work great. Flat to at least 8hz, suitable for mid-bass and subs. I wouldn't use them on tweeters for HiFi music though...

That will fix your level and noise problem. As that gives you real XLR, not fake XLR.
It is designed to convert between the two voltages, correctly.

Beyond that, it's just placement, room modes, and lack of EQ/Delay/Phase. A UMIK and REW should detect it.


Ported and Horned subs minimize excursion, and pro subs don't move far to start with. It should follow the box-model once you get real XLR to it. The leak will reduce some SPL and add some THD, but shouldn't be too horrible. Nothing like what you are describing.

That said: 12's aren't that loud...

Most basshead's need 4 PA-460's to have sufficient SPL in the mid-bass, so I'm not surprised if turns out that a single 12 still isn't "loud enough" for an AVS DIY'er hehe!
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post #11 of 84 Old 08-03-2018, 02:49 AM
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Quote:
Originally Posted by bscool View Post
If you are using RCA to XLR it still flips polarity since the amps XLR pinout is opposite of RCA. You can check for yourself using REW and looking at the impulse.

Edit I see your amp has RCA inputs also. So nevermind my comment about the XLR. I would still check if the RCA on it gives you the same polarity as all of other speakers. You will need to know this eventually anyway as you usually want all your speakers to have the same polarity.
So if I’m understanding you the + & ground of the RCA is connecting to pins that doesn’t correlate w/ the RCA polarity?

I am using an XLR to RCA adapter so I feel this is prudent information.

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post #12 of 84 Old 08-03-2018, 05:07 AM
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Originally Posted by BassThatHz View Post

Most basshead's need 4 PA-460's to have sufficient SPL in the mid-bass, so I'm not surprised if turns out that a single 12 still isn't "loud enough" for an AVS DIY'er hehe!
I am cautious to ask you this but what is sufficient SPL and what frequency range? (55-150hz?)
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post #13 of 84 Old 08-03-2018, 05:58 AM - Thread Starter
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Sounds like you need to buy a Cleanbox Pro:
https://www.parts-express.com/art-cl...erter--245-868
I have 3 of these, they work great. Flat to at least 8hz, suitable for mid-bass and subs. I wouldn't use them on tweeters for HiFi music though...

That will fix your level and noise problem. As that gives you real XLR, not fake XLR.
It is designed to convert between the two voltages, correctly.

Beyond that, it's just placement, room modes, and lack of EQ/Delay/Phase. A UMIK and REW should detect it.


Ported and Horned subs minimize excursion, and pro subs don't move far to start with. It should follow the box-model once you get real XLR to it. The leak will reduce some SPL and add some THD, but shouldn't be too horrible. Nothing like what you are describing.

That said: 12's aren't that loud...

Most basshead's need 4 PA-460's to have sufficient SPL in the mid-bass, so I'm not surprised if turns out that a single 12 still isn't "loud enough" for an AVS DIY'er hehe! [IMG class=inlineimg]/forum/images/smilies/tongue.gif[/IMG]
I’ll definitely pick up that bass box pro

I have some Rythmik 12’s that currently run circles around this. I hope the airflow is the issue.

Dirac doesn’t allow gain changes after calibration so I intended to run these hot on the amp side. Currently they can’t be run hot. The gain match is max gain

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post #14 of 84 Old 08-03-2018, 05:58 AM
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So if I’m understanding you the + & ground of the RCA is connecting to pins that doesn’t correlate w/ the RCA polarity?

I am using an XLR to RCA adapter so I feel this is prudent information.
Yep from the amps I have when using anything XLR to XLR or XLR to RCA the polarity is reversed compared to the AVR built-in amp or my Sunfire amp using RCA to RCA.

I know other people found the same thing and posted about it in the Inuke amp testing thread. As far as I can see it looks to me like most amps that use XLR use the latest PIN standard EIA Standard RS-297-A so most people are going to have this issue and they should verify the polarity of the amps they are using as different amps and different connection can cause issues.

Link to thread where it is discussed throughout the thread in different places. https://www.avsforum.com/forum/155-d...l#post54638692

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post #15 of 84 Old 08-03-2018, 06:00 AM - Thread Starter
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Quote:
Originally Posted by SpinMonster View Post
Quote:
Originally Posted by BassThatHz View Post

Most basshead's need 4 PA-460's to have sufficient SPL in the mid-bass, so I'm not surprised if turns out that a single 12 still isn't "loud enough" for an AVS DIY'er hehe! [IMG class=inlineimg]/forum/images/smilies/tongue.gif[/IMG]
I am cautious to ask you this but what is sufficient SPL and what frequency range? (55-150hz?)
Not sure. I figured max gain would be out of proportion with my fronts. That was the initial test.

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post #16 of 84 Old 08-03-2018, 06:03 AM - Thread Starter
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You need to set them up like you would any speaker or sub you add to a system(distance,x-overs, eq etc).

Have you tested just the 12" alone and took some close mic sweeps with REW to see what it is actually doing as far as FR and SPL? That is what I would do so I could see what the speaker is actually doing and see some numbers and then go from there if you think it is lacking output.

And yes it will affect output if you have air leaks around the speaker where the zip ties are holding it up from making an airtight seal.
I have a mic and have to get an old nvidia driver that works with REW. Nvidia drivers about 6 months ago broke ASIO4All.

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post #17 of 84 Old 08-03-2018, 06:19 AM
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I currently have 2 zip ties in the speaker holes so I can remove the speaker until I'm done veneering and screwing around. Would that "broken airtight seal" kill the volume that much.
Depending upon how much air is allowed to leak it will absolutely reduce SPL. With a big enough leak, you've kind of turned it into a dipole speaker and at low frequencies it will cancel itself out. If you've got it kinda snugged down a little other than the zip ties then that's probably not it (I'd expect *something* decent out of it) and it's something else that's been mentioned.
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post #18 of 84 Old 08-03-2018, 06:30 AM - Thread Starter
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Quote:
Originally Posted by tjcinnamon View Post
I currently have 2 zip ties in the speaker holes so I can remove the speaker until I'm done veneering and screwing around. Would that "broken airtight seal" kill the volume that much.
Depending upon how much air is allowed to leak it will absolutely reduce SPL. With a big enough leak, you've kind of turned it into a dipole speaker and at low frequencies it will cancel itself out. If you've got it kinda snugged down a little other than the zip ties then that's probably not it (I'd expect *something* decent out of it) and it's something else that's been mentioned.
I’ll take them out.

How do others take out the driver? Just tip the box?

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post #19 of 84 Old 08-03-2018, 06:31 AM - Thread Starter
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The amp is 9 months old but I’ve never used it. What are the chances it’s the amp and how can I measure it? I have a multimeter.

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post #20 of 84 Old 08-03-2018, 06:39 AM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
Sounds like you need to buy a Cleanbox Pro:
https://www.parts-express.com/art-cl...erter--245-868
I have 3 of these, they work great. Flat to at least 8hz, suitable for mid-bass and subs. I wouldn't use them on tweeters for HiFi music though...

That will fix your level and noise problem. As that gives you real XLR, not fake XLR.
It is designed to convert between the two voltages, correctly.

Beyond that, it's just placement, room modes, and lack of EQ/Delay/Phase. A UMIK and REW should detect it.


Ported and Horned subs minimize excursion, and pro subs don't move far to start with. It should follow the box-model once you get real XLR to it. The leak will reduce some SPL and add some THD, but shouldn't be too horrible. Nothing like what you are describing.

That said: 12's aren't that loud...

Most basshead's need 4 PA-460's to have sufficient SPL in the mid-bass, so I'm not surprised if turns out that a single 12 still isn't "loud enough" for an AVS DIY'er hehe! [IMG class=inlineimg]/forum/images/smilies/tongue.gif[/IMG]
I’ll have the bassbox in 3 hours. Do I keep the input sensitivity at .775 or move it to 1.4 now that I’m on XLR

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post #21 of 84 Old 08-03-2018, 09:02 AM
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I’ll take them out.

How do others take out the driver? Just tip the box?
I just lay a large pillow down and tip the box and sub onto it. You might have to find something to grab a hole in the sub to get it out. Depends if it sticks in there or not. I got some dental type picks that make so you can take them out easier if they are really stuck in there. Sometimes you can "tap" on the opposite end of the box when the sub is tipped to help loosen the driver too. The gasket tape from parts express can really "glue" them in though and that's when you will need a pick or something else to pry them loose.

https://www.menards.com/main/tools-h...4451312798.htm

Like @BassThatHz mentioned I wouldn't expect a lot out of a single 12" with 375watts. I have a B&C 18 with 1000watts plus and it would take around 4 your 12" to equal that so I think you might be expecting too much from a single 12. You might have to bridge that amp and run that to both 12s once you get them finished if you still want more output. I am not familiar with your amp and what it actually puts out vs advertised power.

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post #22 of 84 Old 08-03-2018, 09:02 AM
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I think that sensitivity is for RCA only, the manual should say. This is assuming your amp is working and not broken/hissing.

Rythmik is a HT sub, it will have lots more output near 20hz etc.
Going from a 12 to a 12 isn't much of an upgrade.

Just make sure the output level is higher than the input level otherwise the input will clip and you will never reach max rated watts. -3db is only half power. -10db is 1/10th and -20db is 1/100th. The signal has to be strong for there to be watts and thus loudness.

Just don't smoke the sub, especially in bridged mode.

Last edited by BassThatHz; 08-03-2018 at 09:17 AM.
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post #23 of 84 Old 08-03-2018, 09:26 AM
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I have several of the XLS series amps and have no problem with levels going to them and I'm using the 1.4 sensitivity setting. I have never needed any unbalanced to balanced converter. How are you getting the signal to them? Are you splitting the sub out between it and your other subs? If so and your subs are crossed at 80Hz, you aren't going to get much output from the MBM. The signal will start to roll off just as the MBMs are getting to the sweet spot. Make sure there is nothing in the receiver that is messing with the signal as well as check the DSP in the Crown amp.

I would also definitely remove the zip ties from the speaker. That could be causing a problem if it's not seated properly in the box.
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post #24 of 84 Old 08-03-2018, 09:49 AM
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Originally Posted by SpinMonster View Post
I am cautious to ask you this but what is sufficient SPL and what frequency range? (55-150hz?)
120db is a good start, at the lp, not 1m...
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post #25 of 84 Old 08-03-2018, 11:47 AM - Thread Starter
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Originally Posted by BassThatHz View Post
I think that sensitivity is for RCA only, the manual should say. This is assuming your amp is working and not broken/hissing.

Rythmik is a HT sub, it will have lots more output near 20hz etc.
Going from a 12 to a 12 isn't much of an upgrade.

Just make sure the output level is higher than the input level otherwise the input will clip and you will never reach max rated watts. -3db is only half power. -10db is 1/10th and -20db is 1/100th. The signal has to be strong for there to be watts and thus loudness.

Just don't smoke the sub, especially in bridged mode.
I just got the Cleanbox and it substantially upped the volume potential. When I had the Crown plugged in grounded it actually sounded much better (initailly I had a 3 prong to 2 prong adapter). What do you run your Cleanbox at? I was running it at Balanced Output of 10 but I'm not sure if that's "hot" or if that just means it's full passthrough?

It removed the 60Hz buzz (much like noise from a guitar,
) but now it's more of a subdued but noticeable static noise. Any idea how to get rid of that? What is that?

Also, I have to be real careful, when I turn off the Cleanbox with the amp on, it thumps big. So amp off first then Cleanbox off.

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Last edited by tjcinnamon; 08-03-2018 at 11:56 AM.
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post #26 of 84 Old 08-03-2018, 11:55 AM - Thread Starter
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Originally Posted by Jedi940 View Post
I have several of the XLS series amps and have no problem with levels going to them and I'm using the 1.4 sensitivity setting. I have never needed any unbalanced to balanced converter. How are you getting the signal to them? Are you splitting the sub out between it and your other subs? If so and your subs are crossed at 80Hz, you aren't going to get much output from the MBM. The signal will start to roll off just as the MBMs are getting to the sweet spot. Make sure there is nothing in the receiver that is messing with the signal as well as check the DSP in the Crown amp.

I would also definitely remove the zip ties from the speaker. That could be causing a problem if it's not seated properly in the box.
Without the converter I get a 60Hz buzz. I have Sub channel -> RCA -> miniDSP -> RCA -> XLS2002. The result is a 60Hz buzz. I'm going to remove that from the chain and see if that reduces any of the issue. I have my mains XO at 100Hz, center at 80Hz, and surrounds/tops at 120Hz.

The miniDSP acts as a "splitter" but it's a digital splitter. I've had issues with Y cables in the past.

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post #27 of 84 Old 08-03-2018, 11:58 AM - Thread Starter
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Originally Posted by BassThatHz View Post
I think that sensitivity is for RCA only, the manual should say. This is assuming your amp is working and not broken/hissing.

Rythmik is a HT sub, it will have lots more output near 20hz etc.
Going from a 12 to a 12 isn't much of an upgrade.

Just make sure the output level is higher than the input level otherwise the input will clip and you will never reach max rated watts. -3db is only half power. -10db is 1/10th and -20db is 1/100th. The signal has to be strong for there to be watts and thus loudness.

Just don't smoke the sub, especially in bridged mode.
The plan is to have the Rythmik handle 20 to 50, MBM's 50 to 120. The Rythmiks are hidden behind a couch (and I have them unhooked while I'm testing) the MBM's are right next to my mains. The idea being they will function as a 3rd/4th way speaker using the AVR's XO.

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Sub: 2x Rythmik LVX12 + MiniDSP
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post #28 of 84 Old 08-03-2018, 11:59 AM - Thread Starter
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Originally Posted by bscool View Post
I just lay a large pillow down and tip the box and sub onto it. You might have to find something to grab a hole in the sub to get it out. Depends if it sticks in there or not. I got some dental type picks that make so you can take them out easier if they are really stuck in there. Sometimes you can "tap" on the opposite end of the box when the sub is tipped to help loosen the driver too. The gasket tape from parts express can really "glue" them in though and that's when you will need a pick or something else to pry them loose.

https://www.menards.com/main/tools-h...4451312798.htm

Like @BassThatHz mentioned I wouldn't expect a lot out of a single 12" with 375watts. I have a B&C 18 with 1000watts plus and it would take around 4 your 12" to equal that so I think you might be expecting too much from a single 12. You might have to bridge that amp and run that to both 12s once you get them finished if you still want more output. I am not familiar with your amp and what it actually puts out vs advertised power.
The XLS2002 is 375 advertised and real world which is why it's a lower number. This speaker can handle up to 1000W per the specs at DIYSG. My port-size cannot without severe chuffing. (according to WinISD)

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Last edited by tjcinnamon; 08-03-2018 at 02:37 PM.
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post #29 of 84 Old 08-03-2018, 01:24 PM
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Originally Posted by tjcinnamon View Post
The XLS2002 is 375 advertised and real world which is why it's a lower number. This speaker can handle up to 1000W per the specs at DIYSG. My port-size cannot without severe chuffing.

I'd bridge it and set an limiter if need be. You also might want to experiment and see how much chuffing you can even hear at volume. I think a lot of people over estimate the amount of they will hear while the system is playing.


Do you have cable? I've had 3 different houses where the cable line wasn't grounded correctly and caused noise in my system.
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post #30 of 84 Old 08-03-2018, 01:56 PM - Thread Starter
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Originally Posted by BigJake82 View Post
I'd bridge it and set an limiter if need be. You also might want to experiment and see how much chuffing you can even hear at volume. I think a lot of people over estimate the amount of they will hear while the system is playing.

Do you have cable? I've had 3 different houses where the cable line wasn't grounded correctly and caused noise in my system.
Does that include a cable modem?
Also, the Cleanbox stopped the 60Hz hum but there is still a low static-y hum if the gain is too high. It's much less noticeable. The Cleanbox has a gain boost in it and I'm able to get it to satisfactory volumes now. I just need to get rid of the static hum. I'm wondering if a noise gate would work for that?

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Paradigm Prestige 75F's + 55C; 8x Paradigm CI Pro P65-R's
DIY MBMs: VRK Build thread + 2x Rotel 981 (bridged)
Sub: 2x Rythmik LVX12 + MiniDSP
DIY Room Treatments: Dutch Floral Prints
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