# why is my sub bottoming out?



## 60ampfuse (May 18, 2008)

I just got a new MB Quart RWE-202 8" sub which is rated at 150wrms. I am giving it less than that in a box with an airspace of .54 cubes. The recommended airspace is .5 cubes. I have tried filling up some of the airspace with some wood and I have tried polly fill but I cannot get this thing to quit bottoming out. And ideas before I send this thing back?


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## placenta (Feb 2, 2008)

what amp and what amp settings? what about crossover?


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## bobditts (Jul 19, 2006)

need to know what your crossover settings are. What is the lowest frequency that sub is rated to play? How did you set your gains? What volume is the sub bottoming out at?


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## 60ampfuse (May 18, 2008)

the amp is an alpine mrp-f450. It is bridged at 4 ohms and the gain is turned up less than half way. The amp is rated at 200 rms at 4 bridged. Crossover is set at 125 hertz. I tried it at 80 and it is almost inaudible. The volume where it bottoms out is maybe 3/4 way up. The sub is supposed to be rated at 30 - 300 hertz in the given box.


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## placenta (Feb 2, 2008)

what makes you think it is bottoming out? whats it sound like?


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## bobditts (Jul 19, 2006)

you have it highpassed at 125 hz? have you tried bandpassing it? Maybe only play it from 50hz to 125hz?


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## Oliver (Jun 25, 2007)

The space seems adequate, how well is the box sealed ?

A cigarette moved around the joints while it is playing will allow you to see if it is letting air get by.[ the smoke will not rise straight up ].

If you need to seal it better try bathtub silicone from your local stores.

You may need a ten inch or two 7kv's.


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## 60ampfuse (May 18, 2008)

anything less than 125 hertz and you cannot hear the sub. I believe it is bottoming out because on any bass note that is somewhat loud I can hear loud popping sounds from the sub. I sealed the box really well. In fact, i probably went overboard with the wood glue.


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## kaigoss69 (Apr 2, 2008)

Make sure the box is 100% air tight!


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## phatredpt (Feb 22, 2006)

60ampfuse said:


> the amp is an alpine mrp-f450. It is bridged at 4 ohms and the gain is turned up less than half way. The amp is rated at 200 rms at 4 bridged. Crossover is set at 125 hertz. I tried it at 80 and it is almost inaudible. The volume where it bottoms out is maybe 3/4 way up. The sub is supposed to be rated at 30 - 300 hertz in the given box.


It IS possible that you are just driving it too hard...
Being an 8 inch you may just be expecting too much out of it 
What kind of music are you listening to? (when bottoming)


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## Oliver (Jun 25, 2007)

60ampfuse said:


> the amp is an alpine mrp-f450. It is bridged at 4 ohms and the gain is turned up less than half way. The amp is rated at 200 rms at 4 bridged. Crossover is set at 125 hertz. I tried it at 80 and it is almost inaudible. The volume where it bottoms out is maybe 3/4 way up. The sub is supposed to be rated at 30 - 300 hertz in the given box.


So a dual voice coil ?

Try them in series.


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## placenta (Feb 2, 2008)

if he has a 4 ohm load he has them in series already

http://www.sonicelectronix.com/item_5585_MB+Quart+RWE+202.html


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## 60ampfuse (May 18, 2008)

Well I may be getting somewhere. Hang tight and ill upload a couple photos


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## placenta (Feb 2, 2008)

60ampfuse said:


> Well I may be getting somewhere. Hang tight and ill upload a couple photos



dont tell me you wired it in parallel for 1 ohm?


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## 60ampfuse (May 18, 2008)

look what i discovered.  Came right off. I did not pull hard I had just noticed that it didnt look very sealed.


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## Oliver (Jun 25, 2007)

I wouldn't be surprised to find out he has the plus from the amp connected to the plusses of both coils  especially with the problem he is describing.


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## 60ampfuse (May 18, 2008)

placenta said:


> dont tell me you wired it in parallel for 1 ohm?


Lol no. Definitely not


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## 60ampfuse (May 18, 2008)

a$$hole said:


> I wouldn't be surprised to find out he has the plus from the amp connected to the plusses of both coils  especially with the problem he is describing.


I think an mecp certified tech for 3 years deserves a little more credit than that.  ^ look up.


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## placenta (Feb 2, 2008)

damn that sux


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## 60ampfuse (May 18, 2008)

The funny thing is at loud volumes I actually thought it sounded good without any distortion. The only problem was what I thought was bottoming out. Turned out to be the dust cap slamming against the cone. Thanks MB Quart!!!!!


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## chad (Jun 30, 2005)

Maybe an 8 is not enough?


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## phatredpt (Feb 22, 2006)

ahhh soooo not grewwed veddy well!


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## 60ampfuse (May 18, 2008)

phatredpt said:


> ahhh soooo not grewwed veddy well!


Apparently not lol. This was my first MB Quart anything. I heard it was a nice sub. Do you guys think I should re glue it or send it back?


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## mvw2 (Oct 2, 2005)

What's the first thing you should ever do when considering running a particular subwoofer?

Answer: model it up. 

Now, if you did this, you would have noticed some things.

1) The box size is way off. Notice the high qts of this sub? It actually prefers a larger box, _much_ larger. In fact, to get a final Q of 0.71, you need a box size of 3 cu.ft., yes 3 cu.ft. for a 8" woofer. Now, it seems a lot of MB Quarts subs are high qts subs. It's useful for low end response, but the final Q is astronomical in the box sizes MB Quart suggests, ok not astronomical but high. You're probably sitting around a final Q of 1.

2) Low end response needs excursion. Unfortunately, an 8" driver isn't all that capable for low frequency duty. You're probably out of linear excursion by the time you throw 50 watts at it. The small box you're running helps a little in resisting cone movement. Frankly, with an 8" driver in a basic, sealed box, you don't have a whole lot of high output use below 80Hz to 100Hz. Ported is really the only route to make up for the lack of cone area and excursion, but it's not something you do with a large box woofer design. You're still in a box box and still using up a good deal of excursion. The plus side is you're basically running down to 20Hz flat, lol, just quietly.

I'm not really sure what you want from us. There's just not a lot you can do unless you're willing to turn it into a ported setup. You want something halfway useable? Ok, build a ported box for it. Build it at least to 3 cu.ft. Tune it low to 22Hz-23Hz. Then run a subsonic filter on it in the range of 20Hz-30Hz. The sub will run flat down to 20Hz. If you want low end response, you'll have it. As long as you keep the box size big enough, you'll keep the final Q respectable. MB Quart doesn't list xmax at all for the sub, and no one know what it is. I could guess that it's maybe in the range of 8mm to 10mm, xmech probably a bit higher as long as they built some throw into the sub. At 150w, excursion is 14mm, 12mm at 100w, and 8mm at 50w.


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## 60ampfuse (May 18, 2008)

mvw2 said:


> What's the first thing you should ever do when considering running a particular subwoofer?
> 
> Answer: model it up.
> 
> ...


I just built the box to the specs that mb quart recommended. They dont even suggest doing a ported enclosure for this box at all. Thats a long post, did you get a chance to see the pics i posted?


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## captainobvious (Mar 11, 2006)

um...yeah, thats not so good. Not glued well by the looks of it


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## Oliver (Jun 25, 2007)

60ampfuse said:


> Apparently not lol. This was my first MB Quart anything. I heard it was a nice sub. Do you guys think I should re glue it or send it back?


Send it back and call them to see if they will let you get a different sub with the credit from this one plus some additional cash.


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## mvw2 (Oct 2, 2005)

60ampfuse said:


> I just built the box to the specs that mb quart recommended. They dont even suggest doing a ported enclosure for this box at all. Thats a long post, did you get a chance to see the pics i posted?


No, I apparently wizzed right by the pics, lol.

Yeah, MB Quart suggests small boxes for all their subs, as does most every other car audio manufacturer. The problem is MB Quart, as well as most other car audio manufacturers, makes high qts subs. The benefit is good low frequency use. The problem is you just end up choking it in a small box and limiting low end sensitivity anyways. You can put it in a big box and lower the final Q and gain low end response, but this requires a lot more cone area and/or excursion to get any low end output. I mean your 8"s not going to have 40mm xmax to get the job done.

No, it's not an ideal ported sub, but it's a method to limit excursion use and let you make use of some more power. You'd be able to get lower and louder with the same sub, but yes, it's not really designed for ported use.


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

Wow, that dust "cone" popped right off... lol... Send it back or get crazy with the rubber cement.. lol..


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## 60ampfuse (May 18, 2008)

Yea I am pretty upset about it. I guess I will look into a 8W3. I hate to spend more money tho right before vacation. What are some other good subs out there for around the same price range? I'm looking for sql. A box of less than 1 cube ported would be nice. I would prefer an 8 but a 10 would be ok. Mostly listen to country and rock. No rap. Gf likes some r&b tho or whatever fergie kind of stuff is.


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## Oliver (Jun 25, 2007)

http://cgi.ebay.com/AUDAX-8-INCH-SU...oryZ3292QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


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## SublimeZ (Jan 28, 2008)

a$$hole said:


> http://cgi.ebay.com/AUDAX-8-INCH-SU...oryZ3292QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


Quote:
Q: Do you see a model number on these drivers? Thanks Jun-04-08 
A: The only number on these at all can be clearly seen in the photo's...i do not know anything at all about these.. i bought them because they were yellow. 


lol.


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## 60ampfuse (May 18, 2008)

a$$hole said:


> http://cgi.ebay.com/AUDAX-8-INCH-SU...oryZ3292QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


Is that really a good sub? Never heard of it?


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## Oliver (Jun 25, 2007)

It's a pair of french made subs 

Focal is also french.

umm, yeah, they're good


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## Oliver (Jun 25, 2007)

AUDAX 8 INCH SUBS MADE IN FRANCE VERY HIGH QUALITY PAIR
4 -0HM 8 INCH MADE IN FRANCE HIGH QUALITY


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## Candisa (Sep 15, 2007)

Renault is also french... I drive a Renault... when it's not in the garage for repair


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## 60ndown (Feb 8, 2007)

Candisa said:


> Renault is also french... I drive a Renault... when it's not in the garage for repair


i took my buddies renault 5 gt turbo out for a spin one day, was quick!


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## 60ndown (Feb 8, 2007)

60ampfuse said:


> I think an mecp certified tech for 3 years deserves a little more credit than that.  ^ look up.


and you purchased an 8" 150 watt driver for your sub bass?

id check the wireing


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## 60ampfuse (May 18, 2008)

60ndown said:


> and you purchased an 8" 150 watt driver for your sub bass?
> 
> id check the wireing


I'm trying to go for a shock factor. I want nice sounding bass with decent spl so that when people hear my sub they think its a 12. Then they go back there and look and an 8. Thats how it was for me when I first heard an image dynamics 8. I dont want that same sub because an installer of mine has it and I just dont want the same thing he has as childish as that may sound.  I plan on trying out many different subs.


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## Oliver (Jun 25, 2007)

1 day and 16 hours @ 7:30 A.M. 

He is in TEXAS, 2 subs for $50.00 or so.

United States 
Item location: Benbrook, TX, United States 

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=296-138
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=296-155


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## Oliver (Jun 25, 2007)

http://www.cadaudio.dk/ht210f0.pdf

AUDAX HT210F0 210mm - Fiberglass cone - 70W - 90 dB - 213mm o.d. - 1,1 kgs 62.10 british sterling pounds.


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## Oliver (Jun 25, 2007)

Who scored two 8"'s for Winning bid: US $41.00


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## 60ampfuse (May 18, 2008)

Wasn't me.


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