I had to replace the rear sub-woofers on my '99 since they had deteriorated to the point that they produced more banging and clanging than anything resembling music. Before doing it I found invaluable and both money and time saving information on the forum for which I'm very thankful.


I also ran across a lot of comments referring to the ohms rating of the speakers and their effects on performance and longevity. I am definitely NOT a serious audiophile so bear with me on this.

I installed a set of 6.5" Kicker DSC65's which have definitely improved the quality to a level I can accept without making me a pauper. In any case the installation instructions make the following statement.

" Two DSC speakers wired in series to a single channel total impedance is 8 ohms (2 x 4). Two DSC speakers wired in parallel to a single channel total impedance is only 2 ohms (4 / 2)"

It appears to me that the manner in which they are wired into the Power Amplifier without any sign of a serial connection between the positive terminal on one of them to the negative input of the other one. If thy had done that the two speakers would only need a wire running from one to the other under the rear seat. Does that make any sense? Of course I guess they could do so within the power amp but that would be the long way around the barn wouldn't it?

 

The Woofers are connected directly to the Amplifier. Since they are not (externally at least) connected in Series OR Parallel, Each one presents a 4 Ohm impedance to the Amp.

 

I thought the woofers were 2 ohms each. I installed 4-ohm woofers and they produce terrible sound when the bass is turned up to 1 or 2. Can't turn the bass up past that because of the resonance. I'm in the process of buying 2-ohm speakers to replace them.

Is there a way of installing a resistor to calm them down?

 

AFAIK, they're full-range speakers, not woofers or sub-woofers exclusively.

 

The speakers I used to replace my rear sub-woofers are not strictly sub-woofers. They are a set of two way speakers with a 6.5" woofer and a 1/2" tweeter that cover the frequency spectrum from 40-20k. They do a good enough job for me.


My question was basically about whether or not the sub-woofers are run in serial or parallel, or as Paul Pavlik believes they are separately circuited from separate woofer outs from the amp to each speaker. That would require two separate power circuits which I think is overkill especially for an amplifier set-up with such a low total power output.


I have no reason to think Mr. Pavlik is wrong however, and I only posted my comment to perhaps shed some light on the 2ohm vs. 4ohm debate

 

This refers to the (Replacement) Speakers as described (6.5" Kicker DSC65's).

I don't know whether the Factory Speakers are 2 or 4 ohm.

The Speaker Configuration has changed through the years and also depends on whether the Standard or Premium System is installed.

The Rear Speakers in the Later Convertibles are Woofers only. Initially, Convertibles had Full Range Speakers in the Rear.

The Rear Side Speakers in the Coupe are Full Range and (with premium sound) a separate Dual Voice Coil Sub-Woofer in the Package Shelf.

And note that you can't use the DC Resistance (only) of the Speaker to determine the Impedance.

 

My '99 convertible came with the upgraded Harmon Kardon system and the rears were subwoofers only and marked as 2ohm. In actuality there were no markings on them that would designate that they were manufactured by Harmon Kardon so Jaguar could have been using some generic subs for all we know. The only visible call out in the whole car is the Harmon Kardon name plate on the tweeter enclosures so who knows.

The schematics in JTIS are difficult to decipher for a number of reasons. First we're not shown the internal wiring of the amp. Second is the almost unnoticeable notation as to what range of serial numbers is covered by what ever particular schematic you're looking at.


In my case the range is from # 031303 onward but even then it shows two different rear speaker configurations. One that looks to include a two additional and separate rear speakers in addition to the subs and one without those additional speakers and both are in the same schematic.


To add to the confusion the wire colors don't appear to be consistent with what actually appears in the car and chaos can ensue. <G><G>

Ain't we got fun. For me this all started back in about 1968 with a backyard rebuild of a real basket case of a 1956 MGA 1600 that had been ridden until it dropped dead somewhere in Daytona Beach, FL.


The only fragment of the electrical system that still operated (the rest was nothing but carbon traces where the wires had once been) was the starter circuit. I paid $164.00 for the whole mess including taxes and tag !!!!

 

My '97 has the upgraded Kommon Hardon system. the 2 "woofers" are wired independently to the power amp. The power amp for my car is shorted and wont shut off so it kills the battery.
My amp also says "Kommon Hardon" on it and its p/n is LJA4170BA. The non-upgraded cars use p/n LJA4170AA. I am a electronics engineer and rabid audiophool so I took the amp apart to see how hard it would be to fix it. It only has 5 channels of actual amplification so even though the woofers run to it separately they are likely in series or parallel connection inside. The amp also has the crossovers built into it.
As my speakers are mostly shot also I decided it time to just rip it all out including the head and start over with something I can use usb memory cards with instead of cassettes/CD's. I will keep all the old stuff in case someone wants to put ti back original. Thats what the last owner did to me. It was obvious it had a newer stereo in it and then they put the old broken stuff back in when they sold it.

Dave

 

My admittedly limited understanding of speakers and the various ways to connect them has me believing that if you wire speakers in series you double the ohms as rated on each speaker and if they are hooked up in parallel you divide the ohms rating of each speaker by 2.

If you're driving two 4 ohm woofers, for instance, with an amp best coupled with 2 ohm speakers you would wire them in parallel, and if you had an amp best coupled with 8 ohm speakers you'd wire your 4 ohm speakers in series. Is that not correct?

Knowing exactly how the internal wiring for a set of speakers is accomplished in the amp would be a great help when it comes to fitting speakers to get the most correct ohms match.

 

It's Correct.

 

LJA4170BA is the amplifier only for the convertible,
LJA4170AA is the one only for the coupe.
They have different frequencies for the rear channels.

 

This would be applicable if the two speakers were to be on the same circuit but they are not. Each stereo channel is a separate circuit. Series/parallel wiring of speakers just does not come in to play here. Each channel sees a load = the impedance of one speaker.

I would not worry much about matching amp to speaker impedance except maybe if the impedance of each speaker were lower than that of the amp, and you were going to drive it pretty hard.

 

The info I have shows differently and shows either amp for coupe or convertible depending on whether its the upgraded system or not the only difference is the coupe's single woofer is connected to both channels but it doesn't show if the coupe woofer is single or dual voice coil. I'm guessing it's dual VC or it wouldn't have both channels going ti it.



Dave

 

http://galleryplus.ebayimg.com/ws/we.../1000x1000.jpg

 

Are you describing a situation where the woofer box has two pairs of terminals on it, rather than one? If so, there are two separate loads internal to the box.

It would never be suitable to take two outputs from an amp carrying two different signals and in effect short them together by connecting them both to a single pair of terminals on a load.

 

it would not be a good idea to tie 2 amplifier's outputs together though some amps can be bridged using 2 channels as one.

The schematic for the coupe woofer wiring shows one woofer and 2 channels of output going to the one woofer but it doesn't show how they are hooked to the woofer. Thats why I suspect the coupe's woofer to have DUAL voice coils which some woofers do have. This way 2 channels of amplification can be sent to a "mono" woofer but the amp sees it as 2 separate loads as the 2 voice coils are isolated from each other. Another use for dual voice coil woofers is that they can be used as difference impedance loads. If it has two 4 ohm coils it can be used as one driven as a 4 ohm load, both in parallel as a 2 ohm load or both coils in series to make an 8 ohm load.

I need to look up the output chips on my dead amp and see what their specs are as see how they are doing the crossover circuitry. If they are using passive circuitry on the output then using a different impedance speaker than original will change the frequency setup by those components. if they are using active circuitry ahead of the output circuits like I suspect it wont matter. But its still a good idea to use the correct impedance speaker. Most amps are ok driving 4 and 8 ohm speakers but these seem to use 2 ohm woofers so the amp obviously must be spec'd to be ok at 2 ohms. Using a higher impedance driver should still work but depending on its efficiency it may not play as loud. The Qts is also important with a replacement speaker as some speakers like closed boxes better than the more or less "infinite" baffle the non upgraded cars have.


Dave

 

Dave,

You certainly have this well in hand and as I am currently trying to fry other fish, I'll move on.

My reason for posting here was that it seemed some of the guys were getting stuck in thinking about the wiring to the rear speakers as though it was all for a single channel ... permitting simple series/parallel connections between the speakers. There be dragons there, as I know you know.

Good luck to all here with their projects.

 

I just read this post and posted a new thread about my rear speaker issues but you sound like you may have the exact answer I need.

2000 XK8 convertible without premium sound. Do you know the type of rear pillar units (SW or speaker), the diameter, the ohm and amp rating of my units. I just want to shop for the right pieces and I know nothing about audio other than you turn it on and sound comes out.

 

Dennis07 "This would be applicable if the two speakers were to be on the same circuit but they are not. Each stereo channel is a separate circuit. Series/parallel wiring of speakers just does not come in to play here. Each channel sees a load = the impedance of one speaker."


True IF in fact the amps outputs to the two rear subs in the convertible are separate circuits. If they are not separate circuits then they must be either parallel or in series within the amp.


If they are indeed separate circuits then it would seem to follow that one sub is handling the right channel output and the other is handling the left channel.

I guess I'll try to get a look at the amp in mine to see exactly how many separate outputs it has and then try to track down the specs for that model of amp.


The schematics for the 1999 convertible with an upgraded system show a total of 9 outputs with a total of 18 wires representing - & + for the 10 speakers illustrated. That includes on pair that goes to ground and also that the tweeters each share a connector with the dash/ fascia mounted spkrs. As an aside the above connections indicate that the fascia and tweeter speakers are wired in parallel which would reduce 4 ohm speakers to 2 ohm and 8 ohm speakers to 4 ohm.


Very confusing since that schematic also shows a PAIR of rear quarter speakers on each side which would indicate a separate tweeter or mid-range in the same location as the sub. My particular car doesn't have those extra speakers.

In addition the schematic also shows the coupe's SINGLE rear sub as having four wires going to it which would support the post that it was a dual voice coil sub with perhaps a full range ability or it being split to accommodate both the right and left channels.

What I haven't seen yet is a positive description of the internal wiring of the upgraded systems amp and just how the various channels are handled internally. Are they indeed each a separate output or are they wired internally in a parallel or serial set-up in such a way as to call for 2 ohm subs to compensate for the now multiplied or reduced resistance.

 

RDM,

I think you can rely on this check: each separate pair of terminals at the output of the amp represents a separate circuit. Most likely you will find there are two pairs of terminals for the rears: one pair wired to one of your rear speakers, another pair to the other speaker.

If that's what you've got then I would not consider making the rear speakers onto a single circuit by connecting them together, in parallel or in series. If they wanted you to do such a series or parallel connection, they would present you with a single pair of terminals on the amp, not two, for the rear speakers.

Also, if you do have two pairs of terminals for the rears, but you combine those speakers together, then (unless you add more components) you would have to drive those speakers from one of the two terminal pairs, and abandon the other pair (it's not OK to connect two terminal pairs, two output signals, together). This can't be what they had in mind.

If you find only one pair of terminals, not two, on the amp for rear speakers then none of this applies of course.

Or so it seems to me ...

Good luck.