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Old 7th November 2008, 08:06 PM   #21
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Originally posted by jol50 - With IB you want more cone area and need less amp. How much output do you need? A 15 in a box is capable of a lot of output, IB less but can give nice SQ and get really low like a large ported.
I'm concerned with SQ waaaay more than SPL. Which is why i'm only shooting for one really good sub and one amp and not 2. My desire is only for my own listening enjoyment - period. But I am a bass fiend and most of the music I listen to [drum n bass, dubstep, hiphop] has a solid majority of the song being mixed below 30hz.

Quote:
Another issue is if you are going to max out IB subs you need a subsonic on them, some sub amps have them built in I've seen some newer alpines do. Other amps have adjustable, some crossovers and HU have them. If you don't beat it hard as possible then not such an issue.
Again , i'm not looking to crush the sub , but I am looking to accurately reproduce the music i'm listening to at loud volumes - not loud by competition standards , but loud by driver in the car standards - and at the same time I'm a computer musician / dj so I do value my hearing especially considering how crucial it is for sound production and engineering.

Volume means almost nothing to me without clarity. Bass is the hardest end of the sound spectrum to shape and analyze so I dont expect perfection in my car.

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The only new amp I have bought in last decade I don't like for my use, its that kicker in the photo...I prefer older amps also but like class D for subs, mostly because I can do less power wiring and less power issues to deal with. I would add that under about 4-500rms it matters less and old amps run subs nicely at that level.
So would you recommend that Earthquake Amp over that Kenwood class D for use with this Dayton 15" for IB use? I'm an inch away from buying either one ...

[thanks for pushing that Earthquake ppia600 ]

I know you said that you usually end up swapping and mixing and matching to find the best fit but if you were to pick between those 2 which would it be? They are the same price within 5 dollars and both with free shipping.

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With IB when it hits xmax you are done, no matter what power you put to it to get there....that is often half or less than rated. That is because you don't have a box to hold the cone back. A more HD speaker will have stiffer spiders and suspension, thus take more power to reach xmax when IB. The Qms can tell you some about that, on the other hand when it gets to xmax you are pushing that much air no matter the power. You can use a larger amp just don't over drive the subs, you have to look at them at max output to see what they are doing....power ratings don't mean anything IB it is all about mechanical movements.
So whats a good basic rule of thumb for not going into xmax and messing up the speaker? Start with the gain all the way down and slowly creep it up while watching the speaker to make sure it isn't at full excursion? Find a sweet spot and leave it ??
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Old 8th November 2008, 12:12 AM   #22
jol50 is offline jol50  United States
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Quote:
So would you recommend that Earthquake Amp over that Kenwood class D for use with this Dayton 15" for IB use? I'm an inch away from buying either one ...

I know you said that you usually end up swapping and mixing and matching to find the best fit but if you were to pick between those 2 which would it be? They are the same price within 5 dollars and both with free shipping.
I can't recommend new amps because I don't buy or use many new ones and ones I have used I'm not impressed though they work ok, if I did I'd say get used...you could buy three and pick one for same money. I bought a 400w profile that is a little small for this use but it was ~$20 and works fine, would push a 12 I'd guess....if you see what I am saying. I'd rather spend on the HU and front speakers where it counts more for SQ. Cerwin Vega was another good deal as I recall one line used the same boards as a much more expensive line. The older amps tend to be EQ'd inside more, some of my best systems I used no EQ on. Things are different today but I still prefer older amps often.

You can run into an issue with too big an amp on IB subs they can get more dynamic. That means a peak in the bass can generate a lot of excursion even though listening level is not that high. This seems to be more of an issue with light duty subs that bottom easily. I don't use many expensive subs for IB I try to run more of them instead, in fact these infinity are most HD I have run IB. I mean if you think you might get a box later and need a larger amp, you could get it now. I don't think of it because I have 250/350/400/600/850/1kw rms class D amps sitting here, I could even strap two of the 1kw but never will. So far the newer amps I have listened to all have a flat curve, older amps may not.

Maybe someone else can chime in on amps. I work on them some now but still learning about quality and such. My issue is how they distort on mid/highs. Sub amps I don't worry about the sound that much either they have the power or not....but all that leads me right back to where I always been--try it and see. At least with a tweeter you have an idea of what one is brighter than another.

Quote:
So whats a good basic rule of thumb for not going into xmax and messing up the speaker? Start with the gain all the way down and slowly creep it up while watching the speaker to make sure it isn't at full excursion? Find a sweet spot and leave it ??
You have to look at it. I'd say set the system up like you would any other, then start cranking on it and watching the sub. When it gets real loud it will start moving and you will have to find the point you should stop, if you get there. With stock speakers I doubt you would. At normal listening levels my 12s hardly move. I'd say loud listening level is no wind noise at 80mph with all windows down. When mine get moving 1/4" I can feel it through the whole car, that is getting into show off territory there and above.

Like I said before mine is a little much and I did it to get db at 20Hz. It will blow me out of the car at 50Hz, my xover is at 45 and my EQ is -4db at 50. I want to swap to pair of moderate 15s, should still get 20Hz and give me more amp room, less weight. I will try a pair of cheap 15s first to see if they can do it, in fact will build the baffle to port the whole trunk to 20hz just for fun as that models to give way more output down there. If it worked I could use less power, but we will see and I'd have to deaden my trunk some. I have a little 350rms class D that would be perfect if it works, or could use about any amp really at that power level. Getting a lot out of a little is great fun when I have the time to play.
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Old 8th November 2008, 01:43 AM   #23
ppia600 is offline ppia600  United States
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/\ The amp I linked is used, not new. It is also a high quality amp with great damping, which is an important spec when running IB setups. More amplifier damping = better. He can always turn the gain down (like it says below \/ ) It doesn't hurt to have more clean rms power than you need. This way you can push the speakers to their usebale limits without any amplifier clipping.

Ok, the earthquake auction ended with "buy it now". My audio bug was actually trying to coherse me into buying it just in case, lol. Good thing someone else grabbed it
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Old 8th November 2008, 03:04 AM   #24
jol50 is offline jol50  United States
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I looked at it, that is a lot of cash for a scratchy thing but I guess it is a big USA amp. I have a 880rms sounstream sitting here I wish would fetch me that much.
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Old 8th November 2008, 03:45 AM   #25
ppia600 is offline ppia600  United States
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$175 a lot of cash for a good amp? Wow, then I really paid too much for my art amps... and they are only 600 watts rms. And the amp wasn't in bad shape, but a few scratches shouldn't matter to someone looking for sound quality and build quality.
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Old 8th November 2008, 09:16 AM   #26
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Quote:
Originally posted by ppia600
Good thing someone else grabbed it.
LOL , it was me ...

Its late and i'm really tired , I'll be back tomorrow, i can't think very clear right now
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Old 8th November 2008, 08:32 PM   #27
jol50 is offline jol50  United States
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Hey these amps have their values, I am not familiar with that brand. I assume it is a PPI amp? Look what people pay for LP....has little to do with their real world performance as an amp. Thing I didn't like is the rust on the ends, or what looks like rust. Most of these old amps that are rough go for half what a nice one goes for, but I have no idea what ppi 2150 are worth I was never into ppi.
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Old 8th November 2008, 09:29 PM   #28
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I am not familiar with that brand. I assume it is a PPI amp?
I was thinking Earthquakes were Zed amps. Someone around here knows for sure.

ppia600, do you know?

Supply caps look like those in my Autotek 7600BTS.
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Old 8th November 2008, 09:33 PM   #29
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Originally posted by tsmith1315
There isn't really such a thing as a 4 ohm amp. Maybe that's a source of confusion?
Ah ... I see ... It was.

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But, the trees are beginning to obscure the forest...

First, a 4ohm speaker is not really 4 ohms. Speaker impedance is polynomial function, not a constant. It will vary considerably with frequency, and be at itís highest value at resonance in sealed or IB/OB. Ported or transmission line systems will exhibit two peaks.

Letís look at the spec sheet for that Eminence Lab12, a 6 ohm woofer.

At 100Hz, itís impedance is about 5.5 ohms. Sounds about right, huh?
At 50 Hz, the impedance is just over 8 ohms. What? I thought this was a 6 ohm woofer.
At 40 Hz, the impedance is 11 ohms. OKÖ
At 30Hz, itís 30 ohms. Thatís right, 30 ohms.
And near resonance at 25Hz, the impedance is just over 100 ohms. Hmm.

So, donít nitpick over a couple of ohms when selecting woofers. Other things are usually more significant.

Another side to the storyÖ Speaker efficiency and frequency response.

Doubling the amplifier power theoretically gives you an additional 3dB in output. Conversely, to raise output 3dB requires twice as much input power.

Remember that the earlier comment about sensitivities of those IB 15ís being ~10dB higher at 20Hz? Well, it takes a *lot* of additional power to even out that difference at 20Hz. Even if your amp was only delivering half the power into the larger 15, SPL would be higher in the 20-40 Hz range.

They only need to keep up with a stock Bose system. This is supposed to be fun. After it's all in: tweak, learn, and repeat.

And whatever you decide to do, donít spend too much, relax, and enjoy the trip!
This post really cleared up alot of grey area for me ... Thank you very much for the education and the reminder to relax. You hit that nail right on the head!


Quote:
Originally posted by jol50
You can run into an issue with too big an amp on IB subs they can get more dynamic. That means a peak in the bass can generate a lot of excursion even though listening level is not that high. This seems to be more of an issue with light duty subs that bottom easily.
I just purchased that Earthquake amp ... When you say too big an amp do you mean in general just TOO BIG or when the gain is CRANKED ?? I can always just turn the gain way down right? And then EQ a -4db at that peak? Would there be a way to find what that peak may be before I actually played the sub so that I could EQ it before hand?


Quote:
When it gets real loud it will start moving and you will have to find the point you should stop, if you get there. With stock speakers I doubt you would. At normal listening levels my 12s hardly move. I'd say loud listening level is no wind noise at 80mph with all windows down. When mine get moving 1/4" I can feel it through the whole car, that is getting into show off territory there and above.
haha , nice way to put it ...

Quote:
Like I said before mine is a little much and I did it to get db at 20Hz. It will blow me out of the car at 50Hz, my xover is at 45 and my EQ is -4db at 50.
When you say your crossover is at 45 do you mean that only 45hz and below are being played by the subs or 45hz and Above are being played by the subs because the trunk/box creates the 45hz below frequencies??


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Getting a lot out of a little is great fun when I have the time to play.
Yeah man! Thats my motto for life , although I do tend to spend a little too much time obsessing over the fine details ...

Thanks!!!
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Old 8th November 2008, 09:35 PM   #30
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Quote:
Originally posted by jol50
[B]Thing I didn't like is the rust on the ends, or what looks like rust.
Should I just sand this to improve the connections?

What should I do to refurbish those rusty looking connections?
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