# Old School MTX Thunder 280 Question



## Radius (May 22, 2011)

I found some room to install some 8" midbass drivers in my current project that I plan to run off an old school MTX Thunder 280 I have kicking around.

The problem is I lost the manual. 

I want to high pass these 8's at 80 hz and then cut them off at around 600hz. The Thunder 280 has an adjustable x-over labelled "EQ" I can't remember if this is a low pass or high pass xover. I *think* it's a high pass but I can't remember for sure. 

If so I can adjust it then put together a passive x-over to cut everything above 600hz. And speaking of that, anyone have a chart what will give me the components and values I will need to build a 12 or 24db x-over for these? They will be in the back of the car and I really don't want much in the way of midrange frequencies going to them, just midbass. I don't want them to mess with the front stage. They're really just "fill in" for some of the midbass I am lacking.

Thanks,
Michael


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## ryan s (Dec 19, 2006)

The switch is to activate the 80Hz *lowpass *only, unfortunately. MTX either cheaped out on the XO section, or they were really confident on that "280w dynamic power" rating and figured most people would use them on subs :laugh:


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## Radius (May 22, 2011)

ryan s said:


> The switch is to activate the 80Hz *lowpass *only, unfortunately. MTX either cheaped out on the XO section, or they were really confident on that "280w dynamic power" rating and figured most people would use them on subs :laugh:


Dang it. Ok then what's the "EQ" adjustment for? Does that change the center freq of the "bass boost" adustment?

I guess now I hafta figure out a bandpass pass x-over for these little 8" drivers. They are useless below 80hz - besides that's what the subs are for - and I certainly don't want them to play anything above 6-700 hz.

As for the power, I remember the "birth certificate" that came with the amp. Seemed pretty respectable to me at the time. The amp tested at something like 87 and 86 watts or something like that RMS into 4 ohms. Hey at least it wasn't wildly over rated like some amps of the day. 

Thanks,
Michael


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## Brian Steele (Jun 1, 2007)

*deleted*


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## FartinInTheTub (May 25, 2010)

Those are great little amps. As for being powerful enough to rock some midbass I don't know. If you had the 2160 then I would say yes. There is no adjustment to the crossover... It's 80hz as stated above.


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## Radius (May 22, 2011)

Ok, so the gain is of course self explanatory. The EQ adjustment is basically a "bass boost" function centered at approx 45hz, and the x-over switch turns on a 80hz LOWPASS filter, right?

If so, passive x-over questions coming next in a new thread.

Yes, they are great little amps. I used this amp in my old Eclipse for some 6.5" midbass drivers in the center console. Worked pretty nicely. 

It should easily run a couple of Dayton 8" midbass drivers. Specifically the Dayton Audio RS225-4. Parts Express item #295-376. Since I am going to bandpass these from 80-600hz I won't be asking too much of the amp. At least I don't think so.

Thanks, 
Michael


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## ryan s (Dec 19, 2006)

Here's a handy (back focused) picture I already had uploaded...










Bass boost is centered at 40Hz, so that doesn't help the situation.

But this is a good excuse to run active


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## Radius (May 22, 2011)

ryan s said:


> Here's a handy (back focused) picture I already had uploaded...
> 
> Bass boost is centered at 40Hz, so that doesn't help the situation.


Thanks for the pic. The label on the back of mine has seen better days. I am curious as to why MTX does not have this manual online. They seem to have everything else _but_ the 280. Even stuff older than the 280. 



ryan s said:


> But this is a good excuse to run active


Yup... I was going to build a passive but now I am leaning heavily towards an audiocontrol 6XS. Would love a DQXS but $$$$$ 

See my post here: 

http://www.diymobileaudio.com/forum/diyma-sq-forum-technical-advanced/110808-crossover-questions-passive-vs-active-lanzar-optix10.html

Thanks,
Michael


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## ryan s (Dec 19, 2006)

I thought I had found the manual, once upon a time, but it was only a promotional brochure for the 1991 line or something. MTX definitely has weak legacy support, considering the manual is probably only 1-3MB in PDF form...


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## FartinInTheTub (May 25, 2010)

There's a cheap 2160 on ebay right now. just fyi.


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## Radius (May 22, 2011)

ryan s said:


> I thought I had found the manual, once upon a time, but it was only a promotional brochure for the 1991 line or something. MTX definitely has weak legacy support, considering the manual is probably only 1-3MB in PDF form...


Very true. Disappointing actually.

Michael


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## Radius (May 22, 2011)

FartinInTheTub said:


> There's a cheap 2160 on ebay right now. just fyi.


Thanks for the heads up. I will keep an eye on these.

Michael


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## King Nothing (Oct 10, 2005)

ryan s said:


> or they were really confident on that "280w dynamic power" rating and figured most people would use them on subs :laugh:


Actually, I think this is probably the case. i had a 275x (same amp but next series) bridged on a thunder 7000 10 in a truck box and I had no complaints. I think most of these amps were intended to run subs


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## King Nothing (Oct 10, 2005)

FartinInTheTub said:


> There's a cheap 2160 on ebay right now. just fyi.


There ae several nics OS mtx amps on the bay right now, including a BNIB white 225ho that id love to have but its a little spendy


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## TheHulk9er (Oct 28, 2010)

If you want to sell that 280 let me know.

I have the 240 which is rated at 20 x 2 running a pair of MB Quart QSC comps for rear fill and they scream with the gains almost all the way down.

These amps are vastly underrated. I think they basically put out about twice what they are rated. If you remember the old days when classes were divided by how many watts you were running you understand why this was the case.

Here's the manual link:

http://www.manualslib.com/manual/435902/Mtx-Thunder-240-280-2160-2300.html?page=17#manual


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