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Thread: First time serious builder need a couple pointers

  1. Back To Top    #11

    Re: First time serious builder need a couple pointers

    Quote Originally Posted by Euphonic View Post
    Hey, me too.



    This might be an unpopular opinion, but I dislike amp dynos. They don't serve much of a purpose in the actual use of the amplifier. For example, I'm happy your amp will do 1000 watts at one frequency with a resistive load, but how does it actually perform on a reactive load in the bandwidth you need it to play? Let's look at the Rockford Fosgate T2500-1bdCP (which is the amp I assume your buddy has). Per Rockford, it has a dynamic power of 2940 watts @ 2 ohm and 2980 watts @ 1 ohm. They also state that it's 77.7% efficient @ 2 ohms and 64.5% efficient @ 1 ohm. With those numbers, there is simply no reason to run it at 1 ohm. Another spec listed on their site is that it's max current draw with a sinewave is 350 amps, while it's average current draw with music is 175. So, if it outputs 2980 watts with a tone, it will average 1490 watts with music.

    There's no way to predict if the system you're planning will give you the end result you're looking for. I've been in vehicles that hit a bit over 150db on a meter, but sound louder with music than others that were in the low 160's. The best advice I can give you is to buy quality gear and use it as intended.
    Yeah I get what you mean. I learned what Thiele Small specs actually mean and for some of them, what that means compared to the "price of tea in China". Like this guy literally said that fs is the frequency at which the subs is most efficient, then immediately said that doesn't matter because it's going to change depending on the enclosure. So I took notes and came up with the following:

    Qt: between .4 to .7, but closer to .4
    Cms: high for the lower bass and less stiff cone for easier movement
    Re/Le lower than 1 Every video I saw said that but I don't understand why totally. I got that the Re is the impedance in ohms at the voice coil but I don't understand Le.
    BL: How ready it is for the cone to be moved by the magnet.
    MMS: lower is better because it's the mobility of all moving parts and air
    Xmax: How much the cone can move in one direction before distortion. I see that that's really important so you don't fry the voice coil but don't understand what that means in real life
    Spl: is actually the efficiency of the sub at 1 watt. So higher isn't always best. Application can obviously change that if I'm guessing right.

    I figured out that if I use my workout headphones (they tune out everything that involves real life they're awesome) and listen to test tones that I could roughly guess what range of bass that I like. I came up with between 30 and 45 but idk if the headphones can play lower test tones correctly.

    Based on that I'm really thinking about the Sundown SA-12 V.2 D2 12" Dual 2 OHM subwoofers. Looking at the specs it's perfect for a sealed enclosure.

    Here's the TS for the Sundowns:
    T/S SPECS SAV2 12″ D2
    RE (Ohms) 3.91
    FS (Hz) 38.8866
    VAS (L) 26.2867
    Qes 0.5070
    Qms 4.5133
    Qts 0.4558
    Le (mH) 3.1785
    BL (NA) 21.9903
    Mms (Grams) 256.554
    Cms (uM/N) 65.2922
    Sens (dB @ 1w/1m) 86.59

    If I'm reading this right it meets all of the qualifications that I'm looking for in a sealed application. Did I miss anything?

  2. Back To Top    #12

    Re: First time serious builder need a couple pointers

    If you have 4 or 5 cu.ft. that could be two 12s or a single 15, vented.

    If you like the low stuff, again you'll want to model it up but - something with a low Fs and lots of displacement potential, in a vented box tuned low with a slot vent, can not only get loud but low. Nothing crazy - tuned 25-30hz (model it) is usually a good balance... Loud, boom car loud, but not a one-note wonder.

    Quick explainer on cabin gain:
    Frequencies have wavelengths. Roughly whatever wavelength corresponds to the longest interior dimension of your cabin - you'll start getting a natural bass boost, about a 12dB/octave gain the lower you play. So you need to factor that into it as you model it up - on the screen, that doesn't factor in your car interior. And the smaller the interior, the more boost you get because this all starts at a higher frequency.

    Personally I'd cap things off with a

    I never really understood why Sundown grew like they did - I don't want to take anything away from anyone's general decent quality and decent service and business talent, for sure...
    ...but call me crazy - there's enough traditional overhung motor nothing particularly special drivers in the world.

    I do like that you are looking at specs - they are a reputable company so you can trust those numbers, I'm sure.

    To answer your question - those TS specs are not bad - but I don't see Xmax listed and that's directly important to "loudness" when sealed. And the Fs there really isn't very low at all. But, the Qts is good for sealed.
    Really though, for sealed - call me spoiled, but something like a W7 sealed is impressive. And nearly as impressive - subs like the CCS SDX 12. With the XBL^2 tech to eliminate IMD distortion and increase excursion. And if you really look inside the W7... That cross drilled pole... It's XBL^2.

    There's other high excursion subs made for sealed - subs like the Dayton Ultimax would be worth looking into, though they don't have the intermodulation-killing tech.

    I honestly don't know if I'd go sealed for you, though. You might even look at a pair of Kicker L7 12s. Or a single L7 15. Vented. The square cones are a different way to gain displacement, from the cone. And their stuff always kills it vented. I haven't sold Kicker in a decade but it's still the same.

    You can make it loud by making the box big...
    With sealed, that's ALL you can do. It'll play low and loud... And clean... (Especially if one of those XBL^2 or a W7)...
    ...but a pair of L7s vented at 28hz or so would be probably be anywhere from half- again you even twice as loud, depending on your vent tuning.

    I don't know your vehicle, but again "power is the worst way to try to get loud". I'd get a good 1000w amp, where you don't really need to do anything to your alternator. Do 1/0 wiring. Do "the big three". Get one of those supercapacitors that look like a battery to install in the back at the amps.

    If you had a 2000w amp - that would only gain 3dB, the amount where a person would say "uh... Yeah... I think I heard it get a little louder than last time."
    So - just not worth it, IMO, to cross that line where you are spending big money in the sketchy alternator industry just to find out it doesn't do what you really want at the RPMs your actually cruise at.

    And you COULD go old-school with a manual EQ, but there's more modern ways for bass control.
    Option 1 - the remote knob for the sub amp. Just turn it ALL down. Or up.
    Option 2 - you can pick up a DSP for a few hundred, unlock a million tuning options - including 3 or 4 presets to pick from the dash remote.

    Food for thought.

    Sent from my LM-G820 using Tapatalk

  3. Back To Top    #13

    Re: First time serious builder need a couple pointers

    Thanks. I'm still researching now that i have a general idea of what the numbers mean. The reason I thought about it and decided to go with sealed is for the sound clarity. I realized that i didn't want to trade that away for louder. But there's not too many ways to make it louder that I've seen so far and retain clarity except more cone area in a bigger space. I'll check those speakers as well.

    The reason for the old school crossover isn't the the bass, it's for the mid and high. Depending on the song I want to be able to tune certain frequencies that bug me down or out totally.

    Thanks for the heads up,

    Lewis King
    Last edited by Original wis; 03-10-2022 at 02:42 AM.

  4. Back To Top    #14

    Re: First time serious builder need a couple pointers

    So after thinking everything through I've decided to go with the following budget build. It's s compromise between what i originally planned and what I've learned thus far.

    4 CT Sounds TROPO-12-D2 in a sealed box, 650 RMS per
    1 inch birch sealed box double baffle, net 5 cube as per specs.
    Here's the TS:
    Fs: 32.50 Hz
    Qms: 6.25
    Qes: 0.62
    Qts: 0.57
    Vas: 44.33 L
    Cms: 0.11 mm/N
    Mms: 216 gr
    Sd: 531 cm²
    Re: 1.12
    Le: 0.58
    BI: 8.92 n/a
    Sensitivity: 87.91 dB
    Xmax: 11mm (one-way)
    Recommended 1.25 cube per for sealed enclosure.
    Taramp's Smart 3k

    4 Power Acoustik NB-4 250-Watt 4-Way Mount Tweeters which I will mount at ear level in the A pillars. They're 60 watts RMS
    Taramp's 400x4 63 watts RMS per tweeter.

    4 Rockford Fosgate punch 6.75 3 way speakers, 60 watts RMS per mounted in the doors and rear deck
    Taramps 440x4 69 watts RMS per

    2 runs of 0 gauge, big 3, 320 amp Singer alternator, XS Power D5100.

    Priced everything as follows:
    Subs 120 per = 500
    Taramps 3k = 300
    Box build = 500 budget
    4xTweeters = 27
    Taramps 400x4 = 75
    4xFosgate 6.75 = 260
    Taramps 440x4 = 87
    Alternator = 600
    Big 3 kit = 100
    XS Power D5100 = 300
    Clarion EQS = 60
    200 for head unit since undecided as of yet.
    2 cooling fans = 25 total

    Assuming that I do the work myself in estimating close to 3500 total since wire, sound deadening, fuse boxes and power distribution will add another 200-300 to the total. I estimated 5 for the box to include material, sealant, rhino paint, screws, wood glue, and corner and box bracing.

    So with shenanigans being what they are I'm thinking 4k total just in case. It'll be 2k less than what I originally thought and probably sounds way better and room to grow if needed that won't break the bank.

    I also found a "TV shelf" on Amazon that would make a perfect amp, distribution, and battery rack for 16 bucks. The woods already pre cut into the dimensions needed to fit in the car in front of the enclosure.

    Any thoughts?

    Lewis King

  5. Back To Top    #15

    Re: First time serious builder need a couple pointers

    Closing

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