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Car Forum / Driving, Maintenance, Tuning / Car Audio / May 20086" Kenwood speakers
Hi all My son bought some 6" Kenwood speakers from a local shop, not cheapies, and we installed them on the rear parcel shelf of his car on Sunday. If we crank the volume (to around 75%) and bass up the distortion is really severe. You can see the cones bouncing up and down and they make a vibrating sound which is very unpleasant so he has to either lower the volume of reduce the bass to eliminate this noise. What I'd like to know is if this effect is just a limitation of 6" speakers or whether the speakers themselves aren't up to par or if there's any way of reducing this distortion to acceptable levels. Would housing the speakers in boxes placed above the shelf help? Thanks Neil. > Hi all > My son bought some 6" Kenwood speakers from a local [quoted text clipped - 14 lines] > Thanks > Neil. What sort of car? What sort of parcel shelf? Without the speakers being mounted in a solid baffle, you'll lose some bass production simply through cancellation. Most 6" speakers won't produce a lot of bass to begin with, but proper mounting will produce a better bass response and you won't need to crank the bass knob as much. >> Hi all >> My son bought some 6" Kenwood speakers from a local [quoted text clipped - 19 lines] > baffle, you'll lose some bass production simply > through cancellation. It's a Nissan sedan, the parcel shelf has cutouts in the steel for the original speakers which suit the 6" Kenwoods. It also has a fabric covered composite board insert over the steel shelf. I thouhjt I could make some MDF boxes and mount them on top of the shelf, but if that doesn't reduce the distortion it will be a waste of time. > Most 6" speakers won't produce a lot of bass to > begin with, but proper mounting will produce a > better bass response and you won't need to crank the > bass knob as much. So is it worth making the boxes? I was thinking 12mm MDF, and paint them matt black. >>> Hi all >>> My son bought some 6" Kenwood speakers from a local [quoted text clipped - 35 lines] > So is it worth making the boxes? > I was thinking 12mm MDF, and paint them matt black. Those type of speakers are generally designed for an "infinite baffle" type setup, meaning they're not intended to have a box behind them. It'll work, and probably get rid of most of the "flapping" of the cones, but it won't really give you much better bass response simply by the lack of air behind the speakers. (see http://www.the12volt.com/caraudio/boxes1.asp) The problem you have is that there are probably other cutouts in that steel deck, and the cardboard panel (since that's really what it is, just stiff cardboard) over it is effectively "transparent" to most of the bass frequencies, so the mounting location has limited usefulness as a baffle. The ideal solution for using those speakers would be to build a more solid deck to replace or complement the cardboard insert. Even 1/4" (6mm) MDF would be a significant improvement. One other thing you want to check is the speaker phase - make sure both + terminals in the wiring are connected to the appropriate + terminal on each speaker. If the speakers are out of phase with each other (+/- reversed), the two cones will be working against each other and canceling bass that way. Ultimately, you want a separate sub and amp to get any sort of decent bass - 6" speakers like that simply aren't designed to move a lot of air, and most decks don't produce the power to move them very much. >>>> Hi all >>>> My son bought some 6" Kenwood speakers from a [quoted text clipped - 44 lines] > speakers. (see > http://www.the12volt.com/caraudio/boxes1.asp) It's the "flapping" as you call it that's the major concern for my son, and not the bass response as such. I could leave the bootom of the box open and place it over the cutout with some cloth or similar to restrict the air flow to the back of the cones. Would that work? > The problem you have is that there are probably > other cutouts in that steel deck, and the cardboard [quoted text clipped - 6 lines] > cardboard insert. Even 1/4" (6mm) MDF would be a > significant improvement. Easily done. > One other thing you want to check is the speaker > phase - make sure both + terminals in the wiring are > connected to the appropriate + terminal on each > speaker. If the speakers are out of phase with each > other (+/- reversed), the two cones will be working > against each other and canceling bass that way. Checked that with a meter, all OK. > Ultimately, you want a separate sub and amp to get > any sort of decent bass - 6" speakers like that > simply aren't designed to move a lot of air, and > most decks don't produce the power to move them very > much. I thought as much, but all he really wants is a nice clean sound without the rumbling. >>>>> Hi all >>>>> My son bought some 6" Kenwood speakers from a [quoted text clipped - 48 lines] > the air flow to the back of the cones. > Would that work? Well the "flapping" is likely a result of attempting to get more bass out of the speakers... solve the bass issue, and the flapping should take care of itself :) A backless box over the cutout really doesn't help the problem, as you still get the "leakage" through other cutouts in the metal. >> The problem you have is that there are probably >> other cutouts in that steel deck, and the cardboard [quoted text clipped - 8 lines] > > Easily done. I'd say that's your first stop then. If possible, use the cardboard insert as a template to ensure your new insert covers the entire rear deck - remember, the ultimate goal is no places for air movement between the top and bottom of the shelf. >> One other thing you want to check is the speaker >> phase - make sure both + terminals in the wiring are [quoted text clipped - 4 lines] > > Checked that with a meter, all OK. A meter won't tell you if the polarity is right. The speakers will be labeled, the positive terminal probably marked with red and maybe wider than the other. If you're using the factory wiring, one will PROBABLY have a larger/wider terminal lug on it. However, if they're the same size or have had new connectors spliced on to them, you may need to dig a little deeper. Is this car running the stock deck as well, or is it an aftermarket deck? >> Ultimately, you want a separate sub and amp to get >> any sort of decent bass - 6" speakers like that [quoted text clipped - 4 lines] > I thought as much, but all he really wants is a nice > clean sound without the rumbling. A basic sealed box with an 8" sub will give him nice clean bottom end without need of massive amounts of amp power. The bass can then be filtered out of the 6s. >>>>>> Hi all >>>>>> My son bought some 6" Kenwood speakers from a [quoted text clipped - 58 lines] > doesn't help the problem, as you still get the > "leakage" through other cutouts in the metal. I follow. >>> The problem you have is that there are probably >>> other cutouts in that steel deck, and the [quoted text clipped - 14 lines] > remember, the ultimate goal is no places for air > movement between the top and bottom of the shelf. A job for the weekend, thanks for the advice. >>> One other thing you want to check is the speaker >>> phase - make sure both + terminals in the wiring [quoted text clipped - 7 lines] > > A meter won't tell you if the polarity is right. Mine does. A minus sign displays if the polarity is wrong as you measure the voltage. All OK. <The speakers will be > labeled, the positive terminal probably marked with > red and maybe wider than the other. If you're using [quoted text clipped - 6 lines] > Is this car running the stock deck as well, or is it > an aftermarket deck? The stock deck was a cassette player (it's a '92 model car). We put a Pioneer head unit in, can't remember the model but all the reviews were good. >>> Ultimately, you want a separate sub and amp to get >>> any sort of decent bass - 6" speakers like that [quoted text clipped - 9 lines] > amp power. The bass can then be filtered out of the > 6s. No room for a sub I'm afraid, he'll have to live with less bass or maybe beef up the 7 x 5's in the front doors and fade more to the front. Either way he'll have to live with the limitations of the system. Thanks very much for your time. >>>> One other thing you want to check is the speaker >>>> phase - make sure both + terminals in the wiring [quoted text clipped - 10 lines] > measure the voltage. > All OK. Umm... what voltage are you measuring? The signal coming out of the deck is AC; the signal phase has to be the same in both speakers. There is no "right" or "wrong" polarity as such, they just have to be the same. A DC meter won't give you a meaningful reading. >> Is this car running the stock deck as well, or is it >> an aftermarket deck? [quoted text clipped - 3 lines] > We put a Pioneer head unit in, can't remember the > model but all the reviews were good. That makes it a little easier then, because you can check the polarity of the connections to the deck, then confirm them at the speaker end. If you used the factory speaker wiring, just follow the wiring color codes and make sure the + and - outputs on the deck properly match the terminals on the speakers. >> A basic sealed box with an 8" sub will give him nice >> clean bottom end without need of massive amounts of [quoted text clipped - 7 lines] > the system. > Thanks very much for your time. There's always room for a sub :) Build a baffle out of 3/4" MDF, put it behind the back seat, and mount a freeair sub in it, no box required :) 5x7s won't give you significantly more bass than 6" rounds, BTW. Bass response is a factor of the amount of air moved, and that has two factors when it comes to the speakers: cone surface area, and excursion. Not accounting for the tapered shape of the cone itself or differences in surround width, a 5x7 speaker nominally has about 27.5 sq. in. of surface area; a 6.5" round speaker has 44 sq. in. of surface area. In other words, excursion notwithstanding, a 6.5" round speaker moves almost twice as much as a 5x7. >>>>> One other thing you want to check is the speaker >>>>> phase - make sure both + terminals in the wiring [quoted text clipped - 18 lines] > have to be the same. A DC meter won't give you a > meaningful reading. The AC bit is news to me, I was under the impression that the current to the speakers was DC, but as you can probably tell I'm more or less ignorant in these matters. Anyway, the meter showed a minus sign one way and not the other, and I connected the two speakers accordingly. (The connectors on the loom of the car were both the same size so that was no help, replaced one of them at each speaker with a smaller one) >>> Is this car running the stock deck as well, or is >>> it an aftermarket deck? [quoted text clipped - 10 lines] > color codes and make sure the + and - outputs on the > deck properly match the terminals on the speakers. My son actually had them written down (good boy!) and they tallied with how we had the speakers wired so it's all good as far as that goes. >>> A basic sealed box with an 8" sub will give him >>> nice clean bottom end without need of massive [quoted text clipped - 11 lines] > of 3/4" MDF, put it behind the back seat, and mount > a freeair sub in it, no box required :) The rear seats fold forward so there's nothing to mount a sub on, and my son needs the folding seats to stow golf clubs.. > 5x7s won't give you significantly more bass than 6" > rounds, BTW. Bass response is a factor of the [quoted text clipped - 7 lines] > notwithstanding, a 6.5" round speaker moves almost > twice as much as a 5x7. OK, so we make up an MDF parcel shelf and kill a little of the bass, that's OK. The system sounds fine apart from the bass distortion so I'll tell him to go easy. Once again, thanks very much for your time and patience. >> The signal coming out of the deck is AC; the signal >> phase has to be the same in both speakers. There is [quoted text clipped - 6 lines] > can probably tell I'm more or less ignorant in these > matters. Not really... just a little n00bish. That's okay, it's always good to learn something new! If you feel inspired to understand it a little better, take a browse of http://www.bcae1.com ("Basic Car Audio Electronics"), specifically section 21 on "Audio Output". > Anyway, the meter showed a minus sign one way and not > the other, and I connected the two speakers > accordingly. It's not unusual for an amplifier's output to have a slight DC offset, which is probably what you were measuring, but there's no guarantee it will be the same offset on both channels and thus not a valid indicator of phase. (Hmm, it's strange there's not actually a section on "phase" on BCAE... it's a little crude, but there's a diagram and brief explanation at http://www.classictruckshop.com/clubs/earlyburbs/projects/stereo/systems.htm - scroll down to "speaker phase") >> That makes it a little easier then, because you can >> check the polarity of the connections to the deck, [quoted text clipped - 6 lines] > they tallied with how we had the speakers wired so > it's all good as far as that goes. Excellent! > The rear seats fold forward so there's nothing to > mount a sub on, and my son needs the folding seats to > stow golf clubs.. Ah. Of course, folding the seats down also introduces the acoustic leakage problem we've been battling thus far, though hopefully not as severely. He'll have to remember that he'll probably see reduced bass output from the rear speakers with the seats down, and remember NOT to try to compensate by cranking the bass control. > OK, so we make up an MDF parcel shelf and kill a > little of the bass, that's OK. > The system sounds fine apart from the bass distortion > so I'll tell him to go easy. Turning down the bass control is the actual "fix" for the problem... the rest of the exercise is intended to improve the speakers' own bass response, so he doesn't NEED to turn up the knob. > Once again, thanks very much for your time and > patience. No worries! >>> The signal coming out of the deck is AC; the >>> signal phase has to be the same in both speakers. [quoted text clipped - 9 lines] > Not really... just a little n00bish. That's okay, > it's always good to learn something new! I try to do that at least once a day. So far so good. > If you feel inspired to understand it a little > better, take a browse of http://www.bcae1.com > ("Basic Car Audio Electronics"), specifically > section 21 on "Audio Output". Will do. >> Anyway, the meter showed a minus sign one way and >> not the other, and I connected the two speakers [quoted text clipped - 5 lines] > same offset on both channels and thus not a valid > indicator of phase. Looks like we fluked it then. 1 in 4 chance I guess. > (Hmm, it's strange there's not actually a section on > "phase" on BCAE... it's a little crude, but there's [quoted text clipped - 15 lines] > > Excellent! He's a good lad. A chemist by profession, so very thorough and everything gets documented. >> The rear seats fold forward so there's nothing to >> mount a sub on, and my son needs the folding seats [quoted text clipped - 22 lines] > > No worries! The internet is indeed a wonderful place, people willing to help just because they can. I'm a carpenter by trade, and a year or so ago needed to cut some radius rafters for an old fashioned house. The common rafters weren't a problem but the two hips had me stumped so I left a message on a mathematics newsgroup and had the answer within a day. Emailed the guy some pictures of the finished article, he was very happy to see a practical application for his theoretical knowledge. So thanks again, and if you need any advice on building feel free to ask. Neil. first the rear speakers are for the rear passengers. if you trying to get them to sound great for the front drivers...lol next a box will only improve the bass....nothing else. next 6'' isnt suppose to give good bass. this is only the tip. but i am alil tired. ******all the other people are salesmen.***** trying to sell services or equipment. i am not. > My son bought some 6" Kenwood speakers from a local > shop, not cheapies, and we installed them on the rear > parcel shelf of his car on Sunday. A sort of a classic kind of installation. > If we crank the volume (to around 75%) and bass up the > distortion is really severe. Either the amplifier is clipping or the speakers are running out of stroke, or there is some kind of parasitic vibration. What can you tell us that will help us decide which one it is? > You can see the cones bouncing up and down That's normal, to a point. > and they > make a vibrating sound which is very unpleasant so he > has to either lower the volume of reduce the bass to > eliminate this noise. Sounds like a parasitic vibration, possibly caused by bad mechanical installation. > What I'd like to know is if this effect is just a > limitation of 6" speakers While 6" speakers are not the be-all or end-all, a pair of good ones can be pretty impressive in the small confines of a car. BTW, they are probably 6 1/2", as that is a near standard size. > or whether the speakers themselves aren't up to par Without more details, how would anybody know? Model number???? > or if there's any way of > reducing this distortion to acceptable levels. Turn them down. ;-) > Would housing the speakers in boxes placed above the > shelf help? Probably not. The trunk makes up a wonderful large enclosure for trapping the back wave of the right speaker drivers. With the right speakers, it can work very well. >> My son bought some 6" Kenwood speakers from a local >> shop, not cheapies, and we installed them on the [quoted text clipped - 13 lines] > What can you tell us that will help us decide which > one it is? Nothing really, I have little knowledge of these things, but the distortion is coming from the speakers themselves in the form of a coarse vibration so I doubt it has anything to do with the amplifier. >> You can see the cones bouncing up and down > [quoted text clipped - 9 lines] > Sounds like a parasitic vibration, possibly caused > by bad mechanical installation. They are screwed down tight to the steel parcel shelf using a small amount of 1.6mm double sided tape at each fixing point, or which there are four for each speaker. I can't see how they could vibrate against the body. >> What I'd like to know is if this effect is just a >> limitation of 6" speakers [quoted text clipped - 8 lines] > Without more details, how would anybody know? Model > number???? Kenwood KFC - M1628A Not top of the range, but not rubbish, or so the salesman assured my son. >> or if there's any way of >> reducing this distortion to acceptable levels. > > Turn them down. ;-) Looks like he will. >> Would housing the speakers in boxes placed above >> the [quoted text clipped - 4 lines] > speaker drivers. With the right speakers, it can > work very well. >>> My son bought some 6" Kenwood speakers from a local >>> shop, not cheapies, and we installed them on the [quoted text clipped - 37 lines] > each fixing point, or which there are four for each > speaker. You mean screw + tape, right? > I can't see how they could vibrate against the body. Maybe the shelf itself, or a stiff covering... >>> What I'd like to know is if this effect is just a >>> limitation of 6" speakers >> While 6" speakers are not the be-all or end-all, a >> pair of good ones can be pretty impressive in the [quoted text clipped - 5 lines] >> Without more details, how would anybody know? Model >> number???? > Kenwood KFC - M1628A I get 6.25 inch nominal diameter. They are a $50/pair class 3-way, which I would not expect too much of. > Not top of the range, but not rubbish, or so the > salesman assured my son. I would say, towards the bottom of the market segment. >>> or if there's any way of >>> reducing this distortion to acceptable levels. >> >> Turn them down. ;-) > Looks like he will. Rarely fails! ;-) >>> Would housing the speakers in boxes placed above >>> the >>> shelf help? >> Probably not. The trunk makes up a wonderful large >> enclosure for trapping the back wave of the right >> speaker drivers. With the right speakers, it can >> work very well. I notice that Kenwood recommends using an angled adaptor with these speakers, in a rear parcel shelf application: http://india.kenwood.com/products/car/speakers/kfc-m1628a/features.html >> They are screwed down tight to the steel parcel shelf >> using a small amount of 1.6mm double sided tape at >> each fixing point, or which there are four for each >> speaker. > > You mean screw + tape, right? Ugh... there's half the problem there as well... the tape will be creating a gap between the speaker frame and the mounting points, which only serves to exacerbate the "leakage" problem. If you have to use something to physically isolate the speaker from the deck, use a "solid" foam, and use it all the way around. I've used "RV foam" before, a stick-on strip that seals up nicely (aka "weatherstripping tape"), when such a tactic is required. See an example here: http://tinyurl.com/4mddxs Building a solid wood deck and just attaching the speakers directly to that will be more effective, though. > I notice that Kenwood recommends using an angled adaptor with these > speakers, in a rear parcel shelf application: > > http://india.kenwood.com/products/car/speakers/kfc-m1628a/features.html That's just to "aim" the mids and highs. Won't help this issue at all. >>> They are screwed down tight to the steel parcel >>> shelf [quoted text clipped - 15 lines] > tape"), when such a tactic is required. See an > example here: http://tinyurl.com/4mddxs I know the stuff, use it in my work from time to time, but it sounds like I could dispense with the tape altogether. > Building a solid wood deck and just attaching the > speakers directly to that will be more effective, > though. That's for Sunday. I've scored some 12mm particle board from a cabinet maker mate. >> I notice that Kenwood recommends using an angled >> adaptor with these speakers, in a rear parcel shelf [quoted text clipped - 4 lines] > That's just to "aim" the mids and highs. Won't help > this issue at all. > I know the stuff, use it in my work from time to time, > but it sounds like I could dispense with the tape > altogether. Yeah, unless you need to seal tight against an uneven surface, you really don't need any kind of foam. >> Building a solid wood deck and just attaching the >> speakers directly to that will be more effective, [quoted text clipped - 3 lines] > I've scored some 12mm particle board from a cabinet > maker mate. That should do the trick, and it'll be a little more flexible than MDF, which should make it a little easier to fit. It'll work alright for this purpose, but just for future reference, particle board is NOT recommended for speaker enclosures, especially sub boxes, because it's not dense enough; MDF is usually the material of choice. >>>> My son bought some 6" Kenwood speakers from a >>>> local [quoted text clipped - 46 lines] > > You mean screw + tape, right? Yes. >> I can't see how they could vibrate against the >> body. > > Maybe the shelf itself, or a stiff covering... The distortion is definately coming from the speaker itself. >>>> What I'd like to know is if this effect is just a >>>> limitation of 6" speakers [quoted text clipped - 17 lines] > They are a $50/pair class 3-way, which I would not > expect too much of. $150 in Oz. >> Not top of the range, but not rubbish, or so the >> salesman assured my son. > > I would say, towards the bottom of the market > segment. Maybe. It wouldn't be the first time a salesman has ripped someone off. >>>> or if there's any way of >>>> reducing this distortion to acceptable levels. [quoted text clipped - 19 lines] > > http://india.kenwood.com/products/car/speakers/kfc-m1628a/features.html I can easily make such a beast, but I doubt it will reduce the distortion. >>>>> My son bought some 6" Kenwood speakers from a local >>>>> shop, not cheapies, and we installed them on the [quoted text clipped - 101 lines] > > I can easily make such a beast, but I doubt it will reduce the distortion. It could provide additional stiffness and mass, as well as better distribution of the highs. >>>>> "Neil Green" <nrgreenNOT@optusnet.com.au> wrote >>>>> in [quoted text clipped - 137 lines] > It could provide additional stiffness and mass, as > well as better distribution of the highs. Maybe, and it'll give me something to do as well. On Matt's advice I'm going to make an insert for the parcel shelf, and a couple of angled enclosures won't take long. Thanks for the tips. > Maybe, and it'll give me something to do as well. > On Matt's advice I'm going to make an insert for the > parcel shelf, and a couple of angled enclosures won't > take long. > Thanks for the tips. Well, we'll look forward to seeing some pictures of your creation. Main thing to remember through this is that the purpose of it all is to keep the front and back of the speaker cones separated as much as possible, so make sure the angled pieces, if you make them, seal well against the shelf, and that the speakers seal against them. Don't need to use silicone or anything, just make sure they're smooth and the speakers are snug. >> Maybe, and it'll give me something to do as well. >> On Matt's advice I'm going to make an insert for [quoted text clipped - 13 lines] > anything, just make sure they're smooth and the > speakers are snug. Yep. If I make them I'll post the pics, along with an appraisal of how it all works. >> Maybe, and it'll give me something to do as well. >> On Matt's advice I'm going to make an insert for [quoted text clipped - 13 lines] > anything, just make sure they're smooth and the > speakers are snug. Made the angled enclosures today, but couldn't cut the shelf insert as the car was at the mechanics for most of the day getting serviced and Boy Wonder went straight from the garage to pick up his girlfriend. Tomorrow's Mothers Day in this part of the world so project "improve the bass in the Nissan" will have to wait till next weekend. Keep you posted Matt. Cheers Neil. |
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