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Discussion Starter · #1 ·
The problem is my MFW-15 bottoms out every so often in many action movies. The beginning Paramount stars sequence in ROTF, Hellboy II tree fight scene, Ironman when he walks out of the cave. At first I did not notice it and just enjoyed the growl and hit the MFW gave for it relatively cheap price. Then it was a gurgle here and flap ther. Then the Stars sequence in ROTF made the sub flap like a dying goose. Now I notice it more and more.


AV123 sent me a new driver but it performs exactly like the old one. Bottoms at the same scenes.


So, I got some test tones and a 33-2050 spl meter.


Auddyssey MULT EQ XT wants to put the SW level at -1.50 but I have it backed down to -4.0 with the sub gain at 10oclock and the Denon AVR volume at -21.


I have attached the measurements I took and some basic pics of the room below. The DB readings can be a little misleading as anything below 30 hz is not much of a tone just a bunch of flapping or distortion. At 30 hz it is a little distorted. At 25 hz it is distortion and flap. 20hz is straight flapping noises.


The room is 13x26x9 with some soffits and such I figure brings the cf to 2800-2900 . I have bass traps in the front and the room is sealed


Can anyone look at these readings and see if there are any clues that my set up is flawed?


The sub is located in the front right portion of the room. Six inches away from the side wall and five feet from the front wall. Just below and in front of the ironman poster. hard to see in the pic.


Sorry for the long post but these are the details.



The file I grabbed says it does spl correction but I am not sure if it is for the SPL meter I have but the original readings are listed in black





 

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Discussion Starter · #3 ·
Thanks! I am just trying to get the sub to perform as well.
 

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Hey Cabo. Do you have Dynamic EQ turn on in your AVR? I have been reading and hearing stories that Dynamic EQ can cause certain subs to bottom out. Can you try tonight and turn Dynamic EQ off and see if that makes a difference. I am just curious.


If some of the others can chime in about what they read or heard about this issue it would be a good read.
 

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You should be discussing this with no one less than MLS. This is the kind of thing where he should certainly be able to shed some light on the issues.


Just looking, it seems to me that you may need more in the way of subwoofing.


If you can't resolve your issues, you may be a good candidate for the Turbo upgrade with its superior driver and 1,000 watt amp. Still, I hate to see you have to spend another ~$700 to get a subwoofer that performs properly.


Best Regards
 

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Discussion Starter · #7 ·
I will check Dynamic EQ. I don't remember it being on, but then again I don't remember it being off.



I don't know how to interpret the spl chart so not sure if there is something I can tweek or not.
 

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Quote:
Originally Posted by GoCaboNow /forum/post/18161729


I will check Dynamic EQ. I don't remember it being on, but then again I don't remember it being off.



I don't know how to interpret the spl chart so not sure if there is something I can tweek or not.


After you check the Dynamic EQ, if that doesn't solve your problem, you should be in direct contact with MLS so you can get to the bottom of the problem. That includes interpreting the spl chart. All of that is fair game when it comes to customer service.
 

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Discussion Starter · #9 ·

Quote:
Originally Posted by spyboy /forum/post/18161681


You should be discussing this with no one less than MLS. This is the kind of thing where he should certainly be able to shed some light on the issues.


Just looking, it seems to me that you may need more in the way of subwoofing.


If you can't resolve your issues, you may be a good candidate for the Turbo upgrade with its superior driver and 1,000 watt amp. Still, I hate to see you have to spend another ~$700 to get a subwoofer that performs properly.


Best Regards

Yeah, me too!



I started off with Mark and now I am with Kyle. Both have been good to work with but nothing is really happening. Kyle is continuing to check with Mark or check on something but again nothing is happening. I either want to have them confirm that this is the expected performance of the sub or send me a driver that can perform without bottoming like this. I also want to make sure I am doing my due diligence in checking set up on my end.
 

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Quote:
Originally Posted by GoCaboNow /forum/post/18161816


Yeah, me too!



I started off with Mark and now I am with Kyle. Both have been good to work with but nothing is really happening. Kyle is continuing to check with Mark or check on something but again nothing is happening. I either want to have them confirm that this is the expected performance of the sub or send me a driver that can perform without bottoming like this. I also want to make sure I am doing my due diligence in checking set up on my end.

Have you posted on the AV123 Forum?


I would post your pictures and some narrative about the disconnect with Customer Service. You may need to become the squeaky wheel. Just make sure that it's not Dynamic EQ...
 

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Cabo I had to change my NIC card at work so I could see your pictures.


That one sub is being over driven in that large of a room. You should stop right now troubleshooting that MFW, sell it and get a pair of something else. I really don't see 1 sub pressurizing that large of a space. You have spent good money on building a very nice looking cinema and now you should consider a higher end dual sub system than what you got. Then I will be over as soon as you do.
 

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Quote:
Originally Posted by hometheatergeek /forum/post/18161971


Cabo I had to change my NIC card at work so I could see your pictures.


That one sub is being over driven in that large of a room. You should stop right now troubleshooting that MFW, sell it and get a pair of something else. I really don't see 1 sub pressurizing that large of a space. You have spent good money on building a very nice looking cinema and now you should consider a higher end dual sub system than what you got. Then I will be over as soon as you do.

Agree.


As soon as I saw your room, I thought WOW, that is huge (and pretty flippin' sweet!). According to the graph, you're getting over 100dB at the LP at 20hz with just one MFW in that massive room? Wow, how close to the LP is the sub? Must be pretty close.


I would definitely look to upgrade to multiple subs for a room that size.
 

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How loud are you listening to the movies at? Maybe one sub is not enough for your room. Your cheapest option would be to add a 2nd MFW 15.


My room is about 1600 square feet & my single MFW 15 is more than enough. I was watching universal soldier regeneration last night & with the master volumer at -5 db I was getting SPL readings of over 110 db at my seating postion & over 120 db at the sub & it was NOT bottoming out!


Good Luck.
 

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Gurgles and flaps have historically been associated with air leakage. Since you obviously know how to remove the driver, there are a few things you can do which may mitigate your issues.


Obtain access to the driver and ensure none of the screws are stripped. Then carefully remove the driver and examine the back of the driver to ensure there is some sort of continuous gasket material that goes all the way around in order to provide an air tight seal when the driver is attached. I'm not sure what AV451 calls it but they may also refer to it as an o-ring. If there's a problem have it replaced or ask what a suitable substitute would be at a home improvement store.


Next, examine the wood where the driver is attached. It may have additional holes drilled besides the ones you use for attaching the driver. As you run your finger across the wood you may feel raised edges especially from where the extra holes were drilled. If so, fill them (just the extra, unused holes) with putty and sand smooth. Also sand smooth if necessary the holes from where you removed the screws so that the entire mounting surface is flat and smooth.


Let's see where that gets you. If there are still problems then maybe we can attack any possible air leakage spots elsewhere. But try this first and then post back with what you discovered.
 

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Discussion Starter · #15 ·

Quote:
Originally Posted by hometheatergeek /forum/post/18161971


Cabo I had to change my NIC card at work so I could see your pictures.


That one sub is being over driven in that large of a room. You should stop right now troubleshooting that MFW, sell it and get a pair of something else. I really don't see 1 sub pressurizing that large of a space. You have spent good money on building a very nice looking cinema and now you should consider a higher end dual sub system than what you got. Then I will be over as soon as you do.

You may be right but it is a long way to Oregon for you.




As a short term solution I added my old sub to the room so I could turn down the MFW and still get some impact. My old sub (12" Athena POS
) can pressurize the room by itself to a certain level. It is boomy though but still adds some effect for movies. It, added to the mfw, allows me to turn the mfw down but I loose the growl from the mfw AND the mfw still bottoms on the 20hz material that shows up in some movies.


My last resort is to get a 30hz high pass fmod but is that the best this sub can do? Just over 30hz stuff? I know it is not a ton of money as far as subs go but I thought I would get it's level of growl and mid bass and not bottom at 20hz?
 

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Discussion Starter · #16 ·

Quote:
Originally Posted by Noubourne /forum/post/18162048


Agree.


As soon as I saw your room, I thought WOW, that is huge (and pretty flippin' sweet!). According to the graph, you're getting over 100dB at the LP at 20hz with just one MFW in that massive room? Wow, how close to the LP is the sub? Must be pretty close.


I would definitely look to upgrade to multiple subs for a room that size.

I did it from the front row so less than 10 feet to the sub. 2nd row drops a few db.


But you can see on the graph that all the sub 35hz stuff is higher than the 35-80hz because it is just flopping or distorted noise. Kind of ugly and embarassing in a movie with freinds over.
 

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Discussion Starter · #17 ·

Quote:
Originally Posted by Chu Gai /forum/post/18162082


Next, examine the wood where the driver is attached. It may have additional holes drilled besides the ones you use for attaching the driver. As you run your finger across the wood you may feel raised edges especially from where the extra holes were drilled. If so, fill them (just the extra, unused holes) with putty and sand smooth. Also sand smooth if necessary the holes from where you removed the screws so that the entire mounting surface is flat and smooth.


Let's see where that gets you. If there are still problems then maybe we can attack any possible air leakage spots elsewhere. But try this first and then post back with what you discovered.

Good point. I have been thinking about that as I have had multiple drivers in there. Although performance is the same as to when there were no extra screw holes but it is worth a shot at renovating the holes.
 

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Discussion Starter · #18 ·

Quote:
Originally Posted by juiceblrc /forum/post/18162068


How loud are you listening to the movies at? Maybe one sub is not enough for your room. Your cheapest option would be to add a 2nd MFW 15.


My room is about 1600 square feet & my single MFW 15 is more than enough. I was watching universal soldier regeneration last night & with the master volumer at -5 db I was getting SPL readings of over 110 db at my seating postion & over 120 db at the sub & it was NOT bottoming out!


Good Luck.

I think it performs great on over 30-35 hz material. The scene in ROTF where the robot slams down on a bunch pipe sends a real nice shudder through the room. It fails on certain types of signals which I am assuming are 20-30hz stuff based off test tones.


Universal Soldier reg is in my queue for the weekend so I will let you know how it does.
 

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Just as another data point, I have three and none have bottoming issues. I've thrown a lot of tough scenes at them, including WOTW most recently (which has stuff as low as 5Hz right?) and they sounded great at teeth rattling volumes. My measured -3dB point is 12Hz (at 75dB target of course), so the MFW is good for sub-30Hz source, but it doesn't sound like pushing the sub is your problem, it's the low frequencies that are wreaking havoc no matter how hard.


I'll give those scenes you mentioned a shot, just to make sure.


Something isn't right, it's just a matter of finding out what exactly. What Chu Gai is saying sounds like it makes perfect sense.


Is there a way to force air into the port (while keeping it sealed) to see where air leakage may be around the driver?
 

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I almost want to suggest the old soapy water look for the leak in the inner tube approach. Almost.
 
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