8 ohm suggestions needed
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New member Username: SeawolfeBismarck, ND USA Post Number: 8 Registered: Sep-04 | First .. I don't care about 2 ohm .. I want a cold and efficient system .. please don't bother telling me I should go the 2 ohm way (last placed I posted this got me too many responses about going 2 ohms and none with what I was asking for). Second .. Please be patient as I haven't kept up with car audio for over 10 years. I have 2 kicker 8" competition SVC subs (yes .. SVC .. from back when kicker comps were the thing to have). These are rated 100RMS/200MAX @ 4 Ohms. I plan on wiring them in series into a box with no divider. The question: What 2-channel bridgable amps work well with this scenario that wont require me to give up my first born son? |
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Gold Member Username: Jonathan_fGA USA Post Number: 2081 Registered: May-04 | 200W RMS isn't hard to accomplish with an 8 ohm bridge. Anything that does 400W Bridged into 4 ohm so that's a 100x2 2 channel amp. What's your budget? |
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New member Username: SeawolfeBismarck, ND USA Post Number: 10 Registered: Sep-04 | I would prefer to stay under $200 if possible. My wife .. love her dearly .. is grumbling about the money I am putting into my trucks sound system when I don't live in it. Best scenario would be if I can budget a max of $350 for that and a decent 4ch amp at 75-90W RMS (4 ohms). |
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Bronze Member Username: StanleycPost Number: 27 Registered: Oct-04 | Hey, I am relatively new to car audio. I noticed that Dave said he wanted a "cold and effiecient system," and wants it in 8ohms. So from that I assume the higher the ohms, the more efficient a system is. Is that correct? I always thought the lower the better for lower resistance, or whatever its called, which would lead to higher overall efficiency. Also, don't amplifiers supply more wattage to through lower ohms? So since I am completely a new, I just got a bit confused because so far everything I have read tells me the lower the ohms the better. ?=( so confused... |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 11 Registered: Sep-04 | Look at it like this .. start with an amp rating of 200Watts RMS at 4 ohms, 2 ohm stable and bridgable. What that means is that the amp will run at 2 ohms but the power you can pull from it is now 400Watts RMS (approximately). Now associate power with heat. if you bridge it you get a 200Watts RMS at 4 ohms amp on, effectively, one channel. Attach an 8 ohm speaker system to it and you get a 100Watts RMS amp. Less power = less heat. As to efficiency .. your amp isn't straining to pump out power at 8ohms. It will probably remain luke warm to stone cold. BUT .. efficiency = less loud. If you want loud go with a 2 ohm stable amp and make sure you keep it cool. |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 12 Registered: Sep-04 | oh .. Jonathan .. as to the second (4 channel) amp .. I am running midbass drivers in the back doors of the truck. (all speakers are diamond motorsport components). The front components and the midbass specs say 5-100W RMS. |
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Gold Member Username: Jonathan_fGA USA Post Number: 2096 Registered: May-04 | The higher the impedance you're running, the amp will generally exhibit great damping characteristics, more dynamic range, lower distortion, etc. Better SQ, basically, b/c the power supply isn't straining to produce power as much as it would with a low impedance. Dave, something like a JBL P180.2 would work if you can find one. It's rated at 360x1 bridged at 4 ohms, but typically puts out over 400 on a bench test (amps were rated at 12.5V, at 14.4 the power will be higher). Cheap amps as well, won't be so hard on your other half. Here's a site that tested it if you're curious about it. Great amp for the money. That amp put out 428 bridged into 4 ohm, it'll do over 200 bridged into 8. |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 13 Registered: Sep-04 | Cool .. thanks. I'm going to get the sub amp first and maybe leave off the 4channel till later. It'll suck for a while running the diamonds off of the HU (Pioneer Premier P960MP - 4x25W RMS) but I'd rather get a good 4 channel amp in the end. I take long road trips to see family and sometimes for business and 10 - 18 hours of crummy sound would get on my nerves. |
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Gold Member Username: Jonathan_fGA USA Post Number: 2105 Registered: May-04 | They also produced a P75.4, which is a little less power, but the 4 channel equivalent. Should be under $350 easily. |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 14 Registered: Sep-04 | Unfortunately I can't seem to find the P75.4 anywhere  I suppose I could go with the GTO series instead. |
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Gold Member Username: Jonathan_fGA USA Post Number: 2107 Registered: May-04 | You should be able to find a JBL P180.2 a little over 100 bucks. 2 of them wouldn't run over your budget. |
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Bronze Member Username: StanleycPost Number: 33 Registered: Oct-04 | So I should be connecting my speakers in series? How do I calculate how many watts I need to produce? I know the ohm double in series and half in parallel from what I have read so far. If connecting speakers in series produces better SQ then I will be doing so. =) |
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Gold Member Username: Jonathan_fGA USA Post Number: 2117 Registered: May-04 | Series is your only option. Wire the positive terminal of sub #1 to the amp, then the negative of that sub to the positive of sub #2. Then, the negative of sub #2 to the amp. |
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Bronze Member Username: StanleycPost Number: 34 Registered: Oct-04 | What about when wiring components? Do I use parallel? So if I use two 750w subs, how many watts would the amp need to be producing? |
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Gold Member Username: Jonathan_fGA USA Post Number: 2118 Registered: May-04 | Oops, thought you were the other guy when I responded to that post. Sorry. What kind of subs do you have? |
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Bronze Member Username: StanleycPost Number: 35 Registered: Oct-04 | I was thinkin of the JL W7s or the IDMax12. |
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Gold Member Username: Jonathan_fGA USA Post Number: 2119 Registered: May-04 | Parallel for you. Series is only when you have a dual 1 or dual 2 ohm sub, especially in a high power application such as with the ID Max or W7, because with higher power you usually have to run lower impedances. Series was mainly to accomodate the guy's want to run an 8 ohm bridge. For you, a mono amp putting out the required power at 2 ohm (or 3 for the JL) will work well. |
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Gold Member Username: Jonathan_fGA USA Post Number: 2120 Registered: May-04 | When you wire components, you hook them directly to their designated amp channel, by the way. What's your budget for the amp? |
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Bronze Member Username: StanleycPost Number: 38 Registered: Oct-04 | I have a budget of 1500 for just the front stuff including the components, HU and amp. O yea wires and stuff too. If I don't get a sub at first, would I be better off with a 3 way set up front? I saw you mentioning it to the guy who wanted the 6W0 in the front. |
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Gold Member Username: Jonathan_fGA USA Post Number: 2122 Registered: May-04 | 2 way vs. 3 way is a never ending debate really, both have their advantages and downfalls. I posted on it not too long ago, here it is: There are many opinions of what is better as far as 2 way vs. 3 way components. There are differences that have to be weighed out when choosing. Pros and cons are so: 2 way components: Benefits are that they are smaller, cheaper, and easier to install. Crossover design is also simpler and has less crossover points, which is good for sound quality because the less crossover points, the better blending between drivers, also, a crossover point in an important frequency range results in degraded sound quality, so the fewer crossover points you have, the better. The problem is that the woofer has to produce a wide frequency band, from midbass up to midrange (wherever the crossover point is, typically 3-3.5k). This makes design of the mid a compromise, and the mid has to be a "jack of all trades" so to speak, just imagine a mid trying to produce midbass and high midrange at virtually the same time, so a poor design lacks one way or the other, sometimes midbass won't be up to par, and some will have a fatiguing, screechy higher midrange reproduction. Of course, excellent design combats these problems. Because of smaller drivers (typically 6.5"), midbass is usually not as good as a well designed 3 way system, meaning you'll have to choose a subwoofer very carefully, because the sub will need to have good midbass transition (around 80 hz or so usually). It sounds bad, but consider that every winning IASCA vehicle that I've seen has done so with a 2 way component system, proof that 2 ways are more than sufficient for sound quality, more on this later. 3 way components: Benefits are that 3 ways have dedicated drivers for midbass, midrange, and treble. A well designed 3 way system will give you punchy midbass, a smoother, more articulate midrange with less listening fatigue, and crisp, detailed treble, you also have less distortion because you have dedicated drivers that are focused within a narrow range. They can also usually handle more amplifier power and get louder than an equivalent 2 way system. Cons are that they are difficult to install, they have more complicated crossovers, drivers have to be designed to blend well and work well with the crossover so SQ doesn't degrade at crossover points (which are usually in an important range), they are also more expensive. They are more difficult to install for optimum SQ. There are less compromises in the design between the midbass and midrange region, meaning the drivers can be optimized for a certain narrower region, and can lead to more accurate reproduction and a more dynamic sound. The midbass, usually around 8", can drop lower than that of a 2 way system usually, the typical 2 way system is typically accurate to around 80hz, with the very best ones going down to around 60. A 3 way's midbass can typically handle 40-60 hz accurately, allowing better bass transition and keeping the bass up front more easily, it also allows you more sub options as midbass transition isn't as important. This means that you can choose that high excursion, more SPL inclined sub and not suffer as much from it  (lower bass, say below 50 hz, doesn't have the subtle nuances that midbass does, plus it's very hard to pick up distortion on bass that low) With that in mind, you HAVE to choose what is right not only for your ears, but for your vehicle. Install is worth about 90% of how a system sounds. On paper, a 3 way component system would appear to be the most sonically accurate, but in the real world, it's a lot different. A 3 way component system will offer fewer installation options than a 2 way system will, meaning that if you do not have a lot of room to work with to get it right, you're probably better off with a 2 way system. Blending of drivers has to be considered, and with 3 ways this is usually limited to door locations with most vehicles, and while some door locations sound great when done right, others suffer. The midbass from a 3 way system will require more airspace, and usually require seperate airspace from the midrange, also a concern to those with smaller vehicles. Top notch SQ vehicles angle the midrange to get the best center and side to side imaging, this is usually done with 2 way systems because there is more room to get it perfect(plus there is only one driver to angle, with a 3 way, you'd more than likely have to angle the midbass and midrange similarly, much harder to do it right), this is a lot of the reason that most winning IASCA systems use 2 way systems. If you can accomodate 3 ways and properly install them, go for it. If you're just going to stick them in the one place they'll fit, chances are you're better off with a 2 way system. So that $1500 is only for HU, amp for components and the components, and you plan to save up for the sub? |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 15 Registered: Sep-04 | Hmm .. 3 amps .. seems a little much for the room (2004 Ford F-150 supercab). As it is I am going to build a custom center console in the back for the subs (still haven't figured out just how I am going to do it .. an isobaric system maybe). That will let me put an amp under the front passenger seat and one under the rear drivers side. I was going to put them behind the rear seat but I decided that I didn't want to deal with pulling the seatback if I wanted or had to check the amps. I'll wait for a bit to get the 4 channel. Even at just 25W RMS the speakers should sound okay (not great) for a couple of months. Maybe around X-Mas the local crossfire/eclipse shop in town will have a sale. |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 16 Registered: Sep-04 | Oh .. btw .. I did order the JBL P-180.2 (from CarDomain.com) last night. Should have it either Friday or Monday next. Thanks for that Info. Now I just need to get to work on that center console/box. Hmmm ... time for a search on isobaric enclosure designs. |
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Silver Member Username: FishyTamarac, FL USA Post Number: 378 Registered: Sep-04 | Ummm..... back to Daves 8 ohm quest for sound quality. I totally agree. IF SPL is not what you're after its definitely the way to go but I kinda question hooking those SVC Kicker's up in series. I was under the impression that running subs in series can lead to phase differences due to the way these two reactive loads electrically interact with each other when connected in series. I wouldn't think this would be very desirable in a SQ application. If high dampening and meager amounts of distortion(and phase interference) are Dave's goals wouldn't a very clean, low impedance/high current 2 channel amp run "stereo"(mono input) be a better solution? Like this: http://www.acaraudio.com/product_info.php?manufacturers_id=27&products_id=515 or this: http://www.acaraudio.com/product_info.php?manufacturers_id=27&products_id=516 I know these two options are mega expensive and probably overkill in this dampening factor/minimal distortion/dynamic headroom "quest", but what about just running some of those 2 channel "4 ohm" suggestions in stereo? I would think the phase coherence benefits would far outweigh any channel imbalance problems. In other words, why not "stereo" instead of bridged? Just a thought. -Fishy |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 17 Registered: Sep-04 | Hmm .. hadn't heard about there being phase differences in the series setup. I'll have to check on that. The main reason I went with bridged is because I will be building either a sealed (not-divided) box under the seat or an isobaric box as a back seat center console. I was under the impression that running the subs in stereo would not be very condusive to either of them. But thought taken. Time to do a bit of searching on phase problems in series circuits. |
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Silver Member Username: FishyTamarac, FL USA Post Number: 389 Registered: Sep-04 | Yeah I don't exactly understand how it works but I think Jonathan said something about up to a 15 degeree phase shift between drivers when hooked in series. I don't even know what the acoustic result would be exactly from this. Maybe a slight loss in SPL(180 degree phase shift would mean total cancellation theoretically) and a bit more "muddiness"? However if your using using a common enclosure then you might very well be better of bridged. I dunno. Where's the master anyways? He's sposed to be here 24/7! -Fishy |
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Gold Member Username: Jonathan_fGA USA Post Number: 2140 Registered: May-04 | Yeah, it'll cause a phase shift(approximately 15 degrees), and usually 15 degrees doesn't make a huge difference when the subs have their own box, BUT in an isobaric application it will cause problems since both subs have to fire simultaneously. Best option is to wire the subs on each channel. It'll perform exactly the same as bridged, it just won't be in mono. If the subs had independant enclosures, it wouldn't make a huge difference. |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 25 Registered: Sep-04 | Okay .. so a push/pull Isobaric isn't really an option unless I go with the subs in parallel? hmm .. now I have to rethink my box. I was going to create a custom center console with an isobaric setup. |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 27 Registered: Sep-04 | Is there any way to "bridge" the pre-amp signal so that left and right are the same at the amp input? |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 28 Registered: Sep-04 | Maybe bridge is the wrong word to use there. I meant convert the pre-amp signal from stereo to mono. |
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Gold Member Username: Jonathan_fGA USA Post Number: 2148 Registered: May-04 | I should have mentioned it, but when you said on the first post that so many people had told you to go w/ two ohms, I figured that may have been mentioned, but you seemed pretty bent on 8 ohms . SQ with a 4 ohm load on each channel will be the same or better. You can convert to a mono signal as well, easy way is to get two y adaptors, one male to 2 female, and one female to 2 male. Then, plug the RCAs into the 2 female, then the one male to the other RCA adaptor's female. Then, those two males to the amp. Instant mono signal. |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 29 Registered: Sep-04 | okay .. that sounds like a plan then. Any cons to merging the signal like that? |
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Silver Member Username: FishyTamarac, FL USA Post Number: 390 Registered: Sep-04 | Hmmmm..... I didn't read "isobaric" you'd need a summing amp http://psn.quake.net/sg-schm.gif which any amp that uses both inputs for bridged output already has. Only problem is that unless you have a manual bridged mode "switch" that turns this deal on and off you can't utilize it in stereo mode. Most external crossovers have mono sub outs which means they have summing amp circuitry built in. You might be able to find a good one real cheap on ebay. I have built in crossovers in my Xtants but I'm utilizing a PPI frx456 for its adjustable subsonic filter and other stuff. Its kinda neat. I have it mounted in my center console so I can tweak while in my listening position. I think if you've got room for something like that its a big plus. I don't think you'd wanna go isobaric with just 2 8's anyways. You'll get a lot more output with a regular sealed enclosure. Of course it will take up around 4 times the space. I really don't know how much stereo material there is in sub 80 Hz recordings. It might not even be enough to worry about. Just use a Y connector to run it off one side if your worried about it damaging your subs. It might just sound a lil "different" but won't hurt nothin. -Fishy |
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Silver Member Username: FishyTamarac, FL USA Post Number: 391 Registered: Sep-04 | [note] thats one side of your preouts, not one side of your amp. -Fishy |
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Gold Member Username: Jonathan_fGA USA Post Number: 2153 Registered: May-04 | Isobaric won't impress for SPL, but it is unique and saves a little space. There is a little stereo below 80 hz, not terribly too much though. Depends on what kind of music you're playing, rap with synthesizers will usually be mono, bass on live CDs etc. will have a set location in the soundstage. A preamp with crossover or external crossover with summing output would be the best way to do it, but that may not be an option w/ your budget. The Y adaptors I mentioned is the cheap mans way of doing it. |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 30 Registered: Sep-04 | Well gentlemen. I want to thank you for all the info in this thread. I also just checked the manual for the amp (found it on JBL's site) and lo and behold .. there is an input mode switch for stereo and mono. So I can run them from each channel and set the amp to properly merge the signal itself. I'm going to try the isobaric approach first because it's different and I've never heard it before. And because I can easily modify my box if I don't like it (it'd be hard to cover the holes in the sides if I decided to try it later). btw .. what the hell does spl stand for? .. I think I can guess sq as sound quality. |
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Gold Member Username: Jonathan_fGA USA Post Number: 2157 Registered: May-04 | Good for you, the adaptors would look kinda cheap . Couldn't remember if it had a summing input or not. SQ is sound quality. SPL is Sound Pressure Level, how loud the system gets in decibels. You have a good many options for isobaric, each with advantages and disadvantages. Go here, and under tech stuff, it has an enclosure design theory tab and isobaric is under there. http://www.maximacar.com/ |
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Silver Member Username: FishyTamarac, FL USA Post Number: 396 Registered: Sep-04 | Err... dave. I'm not exactly sure that mono switch will engage a summing amp, but that would be my guess. I can't think of why else you would need such a switch. And Jonathan. Have you actually successfully implemented that "poor man's summing amp"? I thought of doing that a couple times but thought it would screw up the preamp in my h/u. Isn't that just like hooking a couple of positive speaker wires off an amp together? I mean isn't a preamp just a "baby" amp? or is the output impedance on a h/u's preamp so much higher than the input impedance on an amp that it wouldn't hurt nothin. lol, I went to a whole lot of trouble to utilize the summing amp on my 4180c to run that Class A 50 mono. I gots plenty a Y connectors. -Fishy |
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Gold Member Username: Jonathan_fGA USA Post Number: 2163 Registered: May-04 | Amp input impedance varies so greatly, and is so high, that it really doesn't make a difference. Amp gain settings vary impedance greatly as well, remember that a potentiometer really only varies resistance. The head unit is designed to drive a huge variance of loads. In the past when 3 sets of preouts weren't out there, people used y adaptors so that the head unit could drive a 4 channel amplifier, that cheap summing amp isn't any different saying that the connections are both parallel. |
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Silver Member Username: FishyTamarac, FL USA Post Number: 404 Registered: Sep-04 | Yeah I understand that. My first Alpine had one set of preouts and I had many amps running off it. Its just that with the poor man's method aren't you effectively "shorting" the left and right preamp outputs together? I know the grounds are already common, but I didn't think you could ever connect an output to an output w/o running the risk of frying something. I mean you don't do that with power amplifier outs. Do you? -Fishy |
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Gold Member Username: Jonathan_fGA USA Post Number: 2171 Registered: May-04 | It doesn't hurt anything. There are many people that combine two preouts to drive a single preout, such as powered home subwoofer amplifiers in the home arena, they have a single mono jack. Same as a summing amp, really the signals have to combine somewhere. |
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Silver Member Username: FishyTamarac, FL USA Post Number: 419 Registered: Sep-04 | Yeah I was worried they would combine on the other side of my preamp's output transistor after wrecking the place. :P -Fishy |
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Bronze Member Username: SeawolfeBismarck, ND USA Post Number: 31 Registered: Sep-04 | I just took a y-connector apart as I wanted to see what it was doing. Looks like the same thing when bridging an amp. On the cable I cut apart(2f 1m) the left(-) and right(+) were connected but not a part of the male contacts. The left(+) was center contact and the right(-) was outside contact. Argggg .. figures .. I haul out one of my packrat boxes and suddenly I'm getting nagged about storage space and going through all my old "extra" stuff. |
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