MPS-2500 + 2 Interfire 12" DVC = What?

[interestingfellow]

I promise I'll stop asking silly questions shortly.

Does anyone have experience with interfire subs (12's)? Their specs look good on paper, as does thier price. I just wanted to get a couple opinions before I bought'm, and can't find anything more than some mentioning in a few posts on google (as far as non ads/mfr posts).

500rms/1200peak
DVC
2" EISV 4 layer coils
18mm xmax
.35spl/sealed box

Others had recommended JBL 12's or TI 12's (both DVC's); how do you think the interfire 12's compare. I plan on throwing them on this MS-2500 1ch/10hm.

Now I just have to engineer this bandpass 4th order box for under my back seat.....

Thanks again ya'll!

[ttocs]

first I have heard of them.

I never trust what others hear on the net. No matter what the product is you can find some dude somewhere that will say tha they are better then anything else out there, even if they are made from dog crap.

[interestingfellow]

first I have heard of them.

I never trust what others hear on the net. No matter what the product is you can find some dude somewhere that will say tha they are better then anything else out there, even if they are made from dog crap.

That's the beauty of the internet. Kind of along the same lines as "it was on TV, it has to be true", you know, before the internet machine was in every house and hand in the country. Oh how a society progresses. It really is, SSDD, no matter what.

SO, what have you heard of them, or just like my googling, just a mention.

[todd217]

why dont you just save some money and pick 1 sub and run it at 2ohms mono. see if you can find out how much those subs will take. putting 300-400 to each of those other subs may not be enough while putting 600+ to one may be perfect.

[interestingfellow]

Yeah, but it's a bad ace amp. I was told by tech support to treat it as 2ohm 2chx500wrms or 1ohm 1chx1000wrms. I know I'm asking for advice, but it seemed like a good match up to me.

Thoughts?

[The Golden One]

really it will be difficult to find the right subs until you find the number of subs you want to run, and also you need to get the formula right that accounts for heat loss that happens when you ohm the amp down. i know its not fun but there is a way to determine the power output at the given ohm load you intend run at. also its better to run subs with less power than the overall power the amp makes at that ohm load, that last part was only shadowed over to me by an spl competitor so i don't know the exact percentage. but the power is distributed to all the subs so each sub isn't seeing the full 1000 watts rms.

[gridracer]

Yeah, but it's a bad ace amp. I was told by tech support to treat it as 2ohm 2chx500wrms or 1ohm 1chx1000wrms. I know I'm asking for advice, but it seemed like a good match up to me.

Thoughts?

Yeah but you talked to AAMP tech support about an amp that was made 20 years before they owned the Phoenix Gold brand. Pm MW3 see what he says about the specs he worked at PG when this amp was produced.

[interestingfellow]

well thank you!
@The Golden One
Two subs. It'll take an act of congress to change my mind. I could be stubborn, or it could be legitimate consideration of the perspective install. And, JSYK, I'm no guru, nor am I seeking champagne (beer budget though). I only happened upon this amp by chance (traded for a $50 debt owed to me), and figured I should put in a little better subs than I had originally planned.
And, I've changed my mind about the box. It will still be under the rear bench seat of my astro (lots of cab volume to fill), but it will be sealed (I listen to everything, not just bass), subs firing down, with a 3 or 4 inch air gap at the bottom, and the bench mounted on top (unless I'm persuaded otherwise).

I am serious about the venture, but I'm also making a step up from the usual cheapchit I install (this is just for me, no comps). I"m also foaming and/or matting the whole van, replacing all the banged doors/panels, redoing the interior, and getting a real paint job. Currently, she looks like this:


@Gridracer
Thanks, I will right now.

@ttocs
I share your sentiment about people on the internet. Mind you, we are on the internet now ... I love irony.

I do appreciate all of ya'lls help and opinions, sincerely.

[The Golden One]

not to long ago a this guy had a van just like your's he had 4 10's in it i sounded real good he had a small amp pushing them and they were moving good. man that van looks like a worthy candidate for a sub machine with a wall of 12's and the 2500 can push them just with some cooling fans to keep it cool.

[interestingfellow]

i had a friend of a friend in NC about 15+ years ago. He had a 90 astro (like mine), but it was purple.... We called it a barney.

He had 40 something 10's in it, with about 800wrms each. Massive wall of amps in the back doors with walls of subs all the way around the inside. so far as I know, the slider was welded shut (or silicone, or just never opened).
Needless to say, he won a lot of comps. I didn't really pay attention to the competing, so much as the "how the hell did he do that" part.

Eh, I have to be able to haul my wife, kid, dog (#160 great dane), groceries, and/or friends around, so I gotta keep it modest. For now, 2 subs, new carpet, dye the hard vinyl, foam/dynamat the whole damn thing (as much for audio rattle as road noise).

And, I went ahead and got the IFX-12D (x2) for $130 off ebay..... I'm sorry, I feel like i sold out. Budget is budget, and a cheap bastard never changes. Doin a sealed box with a qtc of 0.707 (+/- %0.05). Wish me luck.

I'll report back.

[The Golden One]

i took a look at those subs they look like you could get them to work well, i would think a ported enclosure on the larger side tuned kinda low would work well on that amp. you may not need fans but if the amp gets hot enough to where you cant hold your hand on it long then a fan shroud may be something to consider.

[interestingfellow]

I'm looking at several calculators on the net right now, and in accordance with the speaker t/s numbers, a sealed box of 1.12ft3 per speaker should yield a qtc of .7077 (which I've read is the "best" for all round listening for a sub). I thought a sealed box would be a little easier to build, and not limit me to a narrow freq band. I listen to as much Johnny Cash as i do Dre.

I'm surprised at the size of the box! Manual recommends between .35ft3 and .7ft3. Called tech support to see if it would be safe to increase the box volume in order to meet qtc~0.7, and he said the biggest box they sell (I only asked to get a baseline for comparison) is 1.5ft3 (qtc .65).

Does all this sound right?

I've ran a sealed box in my last 2 vehicles, and am alright with the response I get across the band. I've used the same 12" in my C10 truck as in my Astro. I used a sealed box of 2.5ft3 in both (different custom boxes). Please, don't judge me, but it was a Radio Shack pro 12" and a Pioneer GT-300t (200w bridged). Sounded great in the small cab of the truck,but was barely anything for my astro.

[The Golden One]

i was thinking more on term's of efficiency and output that relates more toward the 2500 you would lose quite a few db going sealed with those subs and that amp. but when listening to different types of music sealed would most likely sound better overall but you will lose db the smaller you go with the box. small sealed enclosures are not the best for sq or overall output their more for fitting more speakers in the vehicle.

[dwnrodeo]

I'm looking at several calculators on the net right now, and in accordance with the speaker t/s numbers, a sealed box of 1.12ft3 per speaker should yield a qtc of .7077 (which I've read is the "best" for all round listening for a sub). I thought a sealed box would be a little easier to build, and not limit me to a narrow freq band. I listen to as much Johnny Cash as i do Dre.

I'm surprised at the size of the box! Manual recommends between .35ft3 and .7ft3. Called tech support to see if it would be safe to increase the box volume in order to meet qtc~0.7, and he said the biggest box they sell (I only asked to get a baseline for comparison) is 1.5ft3 (qtc .65).

Does all this sound right?

I've ran a sealed box in my last 2 vehicles, and am alright with the response I get across the band. I've used the same 12" in my C10 truck as in my Astro. I used a sealed box of 2.5ft3 in both (different custom boxes). Please, don't judge me, but it was a Radio Shack pro 12" and a Pioneer GT-300t (200w bridged). Sounded great in the small cab of the truck,but was barely anything for my astro.

Go with the 1.12 cu. ft. sealed box to yield a qtc of 0.7. Most manufacturers will give box recommendations for SQ and SPL with the smaller box typically pertaining to SPL. The larger box will allow the woofer to play lower while the smaller box will give the woofer extra output (~3db) usually around the 60-70 hz region.

[interestingfellow]

Well,
what dangers are there of going bigger in a sealed box (damage to the speaker, min/max freq, power handling, etc)?

I can easily accommodate 6.5ft3 (for both subs together). As it stands, dealing with a 2.3ft3 box (for both subs together) means that I would end up with some space to use some other way (another set of 6x9's, storage, mount the amp in w/fans, or just dead space).

[dwnrodeo]

http://www.diysubwoofers.org/faq.htm

1.05 - What happens if the box is too large?
Typically the low frequency extension of the system improves a little, at the expense of powerhandling. The bass will also sound tighter and "drier", which might not suit your listening tastes. In the case of vented systems, a too-large box may introduce a response peak around the the resonance frequency of the system.

[Eric D]

really it will be difficult to find the right subs until you find the number of subs you want to run, and also you need to get the formula right that accounts for heat loss that happens when you ohm the amp down. i know its not fun but there is a way to determine the power output at the given ohm load you intend run at. also its better to run subs with less power than the overall power the amp makes at that ohm load, that last part was only shadowed over to me by an spl competitor so i don't know the exact percentage. but the power is distributed to all the subs so each sub isn't seeing the full 1000 watts rms.

What do you mean by "get the formula right that accounts for heat loss that happens when you ohm the amp down"?

[ttocs]

I just ignored it.


I think my brain has started to produce a chemical that makes it easier to ignore these posts.

(thats what it looks like with my brain making the chemical)

[Eric D]

It is bad enough just trying to digest the "ohm the amp down" part of it. Having never heard it put that way it just sounds funny to me.

[ttocs]

but wut do you no?

[interestingfellow]

I think he meant something like this (taken from http://www.allaboutcircuits.com/vol_1/chpt_12/6.html
But I think it would get waaaaaaay complexer if you attempt to account for all the electronics' values and coefficients inside the amp.

;D

[Eric D]

That looks like thermal resistance to me, but would not have much to do with the amplifiers output (at least as the point was presented above).

[interestingfellow]

well, kinda.

more heat creates more resistance, and Ohm says that means less juice.

or something

[ttocs]

sure you don't have that mixed up? resistance can cause heat, but this is the first I have heard about anything temp related to finding your resistance either with my installation certs or with my electronics degree.

[interestingfellow]

I might be wrong. I've always thought "cooler=more juice". I know many electronics operate less efficiently when they are hot. i realize the need to keep heat off components that are generating heat themselves (fets, cpu's, motors, etc) becuase the heat can damage them.
Guess I never really thought about that aspect of it....Just ASSuMEd.

Isn't the formula I posted earlier expressing that relationship (hotter=more resistance)?