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Amp on fire!

2230 Views 43 Replies 15 Participants Last post by  daloudin
Well.not fire but too hot to touch. please keep answers serious as this is really bothering me.
its a Skar RP.150.4ab amp.
in order to keep it alive ive put steel mesh on the bottom and added 2x140mm fans hooked to the fan header as it runs 24/7 and now ive added a 12” radiator fan to make sure it doesn’t go into protection.
ohms is between 2-4 on each channel. But its the AMOUNT of speakers that worry me.
2x- 8” full range
4x- 3.5” componant.
6x- tweeters

too many speakers being driven? I do add some bass around 220hrz
so whats next? Im gonna remove some speakers today if it doesn’t rain.
i really like the sound of the amp and speakers.
so if i need another amp, what do you suggest in the $200-$250 range?
i am considering the CT Sounds CT-150.4D Full-Range Class D 4 Channel Car Audio Amplifier, 1000 Watts RMS
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I dont do series on speakers,only parallel.
Hence your amp being on fire. Assuming you mean the Skar 3.5s in front comprise one of the three sets of tweeters and you've retained the passive crossovers, in the upper frequencies the amp will see a load of 1.3 ohms as others have pointed out. But if your 6x9s are coaxials, then you actually have 4 tweeters up front and will be at 1 ohm from ~3500 Hz up (or whatever frequency gets you above the crossover point of both the 3.5s and the 6x9s)...

One option, again assuming you've retained the passive crossover for the 3.5s, and whether or not the 6x9s are bass drivers only or coaxials, would be to add another passive crossover between the 6x9s and another of your existing pairs of tweeters. This will keep your amp from burning up long enough for you to figure out why we are all saying you should only have one tweeter per channel.

So from the front channels you would have
Left --> Crossover 1 --> tweeter
...................................--> 3.5" woofer
.......--> Crossover 2 --> tweeter
..................................--> 6x9" woofer
Presenting a 2 ohm load overall. Rinse & repeat for the right channel.

BUT you could also just buy a 3-way crossover and do
Left --> Crossover --> tweeter
...............................--> 3.5" mid
...............................--> 6x9" woofer
(And if that doesn't get you enough sound at 4 ohms total, buy a bigger amp).

The rear I won't try too hard to decipher, but don't put tweeters on your rear package tray. It sounds like you could get it down to either a single 2-way crossover (full range 8" + tweeter) or a 3-way crossover there as well (8", 3.5", tweeter) and then leave it at that.

Of course none of this considers the subwoofers as they are driven off of separate amplifier(s) and you haven't stated you have any problems with them.

So apart from subs, you can get it down to 12 total or 10 total drivers off a 4 channel amp, and still present a 4 ohm load provided crossovers are configured properly.

Then disconnect your two rear channels and enjoy.
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(Edited for typos)

My advice, and I expect you'll get the same from others, is you have clearly made some improvements, now pause for a moment, spend time listening to your system, read about driver selection, and study, study, study installation and tuning methods before you pour any more money into components that may not work well together.

A few starting concepts, and you can research further from here:

Low bass frequencies, especially when played in a small room, are omnidirectional and cannot be located by your ears. Don't worry about subwoofer placement so much as installation technique.

Midrange and high frequencies contain lots of imaging cues and are easily located by your ears, this is in part a function of having shorter wavelengths relative to the spacing between your ears. In other words, your brain can interpret the intensity difference and the time delay between when the signal reaches your two ears, and instinctively direct your attention to the origin of the sound. For this reason, placement of these speakers is key to recreating sound that is similar to what was recorded.

It's worth trying the following: wrap the backs of your midrange drivers in a few layers of towels to cancel the back wave. Cut holes in tennis balls and install your tweeters into those holes. Wire both up with extra length of wire, and move them around the cabin, placing them close to any feasible locations where your could install them, and listen for differences. You can temporarily prop these up with twine, tape, Velcro, putty - whatever makes sense and will hold each speaker in place long enough for you to listen to a familiar recording and form an impression of how realistic or unrealistic the sound reproduction is. Repeat this exercise until you've tried every feasible location and angle for each driver, and identified the "sweet spot" where everything sounds nearly as good as you hope - with no signal processing whatsoever besides basic crossover setup either via passive crossovers (if your available number of channels of DSP and amplification are limited), or with the active crossovers built into your DSP. Proceed to install in those locations.

Setting crossover points is another whole topic. Your best starting point is to look up the Fs (resonant frequency) of your tweeter, and set your crossover point to 2x Fs. On the flip side of that, you'll want to consider the size of the drivers reproducing your midrange and woofer or "mid bass" as we sometimes call it, and consider how high each of these will be required to play based on the tweeter crossover settings.

You can calculate (searchable, though I don't store the formulas in my active memory) based on the size of the midrange and mid bass drivers where you can expect to hear cone breakup, beaming, and cancellation - effectively wherever frequencies from one side of the driver will cancel out the frequencies from the other side based on the distance between them adding up to half the wavelength of a given note. Manufacturer's frequency response charts, if available, will also shed light on the range in which you can expect a flat response - especially if a chart is provided for both on-axis and off-axis response. Try to cross your mids below the upper end of that flat range depending on the orientation. (Unless you get fancy, mids and woofers will almost always be mounted off-axis in the mobile audio environment, i.e., a typical door installation.)

If you have a 2-way setup and find you have a frequency gap between how high your woofers play and how low your tweeters play, then you have entered territory where a 3-way soundstage is appropriate and perhaps necessary for satisfactory results. You'll have to make a studied decision on whether or not that is appropriate in your build.

Once you understand everything I typed above, as well as all follow-up questions that have arisen, THEN commit to your next set of experiments. In the meantime, continue listening to what you currently have installed to establish a baseline you can refer back to, and detect whether any changes you make going forward lead you toward or away from accurate sound reproduction.

$.02.... my first stereo had two Auto Zone "bass tubes" running off the back two channels of an 80 watt head unit, with a pair of door mounted no-name coaxials with Mylar tweeters in ugly wooden spacers in the front door cards. We all start somewhere, and we all go through many iterations to get to something satisfying to our ears. The trick is, as we learn more, we hear more. It is an endless rabbit hole, but if you're going to head down it, you'll do best if your next attempts are studied and intentional, so you can understand why you get the results you do.

Good luck! As you can see, those of us who have been around this block a time or two are all very willing to help out where we can when someone presents a genuine question. We blend art and science here to a large degree, which means you'll often find more than one approach that works. The trick is gaining the background to understand why something does or doesn't work, and the craftsmanship to present it in a way you can personally enjoy and be proud of. Hope this and the comments you've received from others have been helpful.


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I read all of that and if I were him I'd listen. I love reading what knowledgeable ppl have to say. But I think he just wants to get loud and wake his neighbors when he gets home. Maybe make a YouTube video of his body panels "flexin" like Redondo beach waves. But you are right and in this game less is more.
I mean, I can also tell you how to break the windshield on a GMC 1500. Many years ago, an old buddy had me design and build a half-wall of 4 12s in 13 CF replacing the second row of a cab-and-a-half pickup. Roughly 2500 watts clean RMS, 2/0 wiring everywhere, and a 350 amp alternator. You could hear him well over a mile away, but I still made sure his tweeters were located properly for decent imaging ---- not that he would ever notice with the bass-induced deafness that certainly followed after a few weeks of listening

I will say, the bass was so intense I wore earplugs and earmuffs while tuning the system, and still had to take a break every 5-10 minutes so I wouldn't be sick to my stomach. You wanna wake up the neighbors? I won't condone it but I can sure pull it off when it's the order of the day.

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Lol, I think Im beyond the point of wanting just gut punching, ear ringing bass. I've had my share of one note wonders and I'd end up just turning the bass down cuz It just destroyed any enjoyment of music. I'm all for a little bass maybe alot of bass but it has to be the complete bass spectrum. I have found a new love for high excursion, low distortion high power handling, subs in sealed boxes. I have a 4k amp in my car now but you can't hear me a mile away and I'm not ok with waking my neighbors. 99% of the time my windows are up when I'm blasting music.
Yes, not remotely my style either. Even in high school I knew to turn my system down whenever I was within a few blocks of home, or whenever I was going to park the car in public, to not draw unwanted attention from neighbors or opportunist thieves. This was a paying customer though, so I met the design specifications, and had fun doing it. It's not something I'd want to live with in my own car though.

But I think I've kind of unintentionally thread jacked here. Let's wait and see if OP needs anything further.

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Make sure you get one that's 1 Ohm stable on all 4 channels...
The one you've linked doesn't appear to be one of the ones they advertise as 1 ohm stable. Not familiar with the brand, just going by the packaging. Their 440x4 and 800x4 do claim 1 ohm stable, but that's not a claim I'd personally be eager to test on an amplifier in that price range.

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