Need Component Selection Advice Re: Loudspeakers

[petrolSpice]

I have two old Wharfedale loudspeakers, each with a tweeter, mid, and 12" subwoofer. The original subs fell apart a couple years ago so I replaced them with JL 12w1v2-8 ohm subs using the original wiring/crossovers. These subs are rated around 100Wrms for "optimum" and 200Wrms "maximum". They worked great, sounded great. But I have since fried two receivers using these speakers, the most recent of which was a Sony STR-DE197 that has 100W per channel, two channels. It also had auto-protect built it but I fried it anyways. The speaker inputs indicate 8 ohms. Will one of these work for powering these speakers? Or is this completely the wrong type of device?

Second question... I tested the resistance of the speaker inputs today, one was at 8 ohms and the other was 1 ohm. Does this mean that the crossover in this speaker is toast? Could this damage a amp/receiver? Perhaps this is why I fried the Sony receiver. I have a rough idea of what the crossover specs mean, but I am not sure exactly what I need, especially in terms of the frequency ranges.

Last question... I am going to also replace the tweeter and mids in these speakers. Do all the components, tweeter, mid, sub, and crossover need to be the same impedance? The subs are really the only component I'd like to keep, and they are 8 ohms.

These speakers are for parties mostly and will only play music from an iPod or computer. I am not looking to spend much money. Sound quality is important but not thousands of dollars important. Thanks!

[Chris Roemer]

Re: Need Component Selection Advice Re: Loudspeakers

I have two old Wharfedale loudspeakers, each with a tweeter, mid, and 12" subwoofer. The original subs fell apart a couple years ago so I replaced them with JL 12w1v2-8 ohm subs using the original wiring/crossovers. These subs are rated around 100Wrms for "optimum" and 200Wrms "maximum". They worked great, sounded great. But I have since fried two receivers using these speakers, the most recent of which was a Sony STR-DE197 that has 100W per channel, two channels. It also had auto-protect built it but I fried it anyways. The speaker inputs indicate 8 ohms. Will one of these work for powering these speakers? Or is this completely the wrong type of device?

Second question... I tested the resistance of the speaker inputs today, one was at 8 ohms and the other was 1 ohm. Does this mean that the crossover in this speaker is toast? Could this damage a amp/receiver? Perhaps this is why I fried the Sony receiver. I have a rough idea of what the crossover specs mean, but I am not sure exactly what I need, especially in terms of the frequency ranges.

Last question... I am going to also replace the tweeter and mids in these speakers. Do all the components, tweeter, mid, sub, and crossover need to be the same impedance? The subs are really the only component I'd like to keep, and they are 8 ohms.

These speakers are for parties mostly and will only play music from an iPod or computer. I am not looking to spend much money. Sound quality is important but not thousands of dollars important. Thanks!

You need to get inside both cabs, disconnect all 3 drivers (mark the leads FIRST), and measure each one. Typically, a driver that's rated at 8 ohms impedance will read about 6 ohms DC resistance (which is actually what you're measuring here). I think you'll find that one of the 6 drivers is a near short, 1 ohm or less.

Chris

[petrolSpice]

Re: Need Component Selection Advice Re: Loudspeakers

You need to get inside both cabs, disconnect all 3 drivers (mark the leads FIRST), and measure each one. Typically, a driver that's rated at 8 ohms impedance will read about 6 ohms DC resistance (which is actually what you're measuring here). I think you'll find that one of the 6 drivers is a near short, 1 ohm or less.

Chris

Thanks Chris! So you think one of the drivers is shot then? It's pretty simple to get inside these by unbolting the sub. I will give it a shot.

Would having an impedance of just 1 ohm at the input posts fry a receiver?

[Leroy R]

Re: Need Component Selection Advice Re: Loudspeakers

Anything less than 4 Ohms is hard on most amps and 1 Ohm will definitely damage most amps.

[petrolSpice]

Re: Need Component Selection Advice Re: Loudspeakers

I pulled apart the loudspeaker and tested the impedance of each driver:

Sub 8ohm: 6.9ohms
Mid ?ohm: 6.8ohms
Tweeter 4ohm: 4.4ohms

With all the drivers disconnected the crossover input posts still gave 0.9-1.1ohms. Does this mean the crossover is bad? The label on one of the coils burned off.

No matter what, I would like to replace the crossovers, tweeters and mids with more modern pieces. Do the mid and tweeter still need to be 8 and 4 ohms, respectively? Or does it depend on the crossover? The sub is 8ohms and will not change.

[Leroy R]

Re: Need Component Selection Advice Re: Loudspeakers

Sounds like you have at least one component shorted in that crossover. There is a good chance that inductor is the culprit, but it could also just be the victim of another bad component.

Sounds like you want to just reuse the cabinets and replace all of the drivers and crossovers. If that is the case, you need to calculate the internal volume of your cabinet. Once you know that, I would search here for someones design that uses a cabinet with the same volume and use the drivers and crossover for that design. That still won't be a perfect solution, because a lot of other factors will not be considered like baffle width and placement of the drivers on the baffle. Your best bet would be to build one of the designs as they were intended, cabinets and all. If you don't have the capability to build your own cabinets, there are a couple options here. There is a thread going currently for flat packs of current designs, all you have to do is assemble the already cut pieces finish them however you want, assemble the crossovers and install everything in the cabinets. There is also another gentleman that has a CNC router that will machine the panels for any cabinet you want for a very reasonable price.

If you were just planning on throwing a bunch of drivers and a generic crossover in your current cabinets, you might just as well keep what you have and fix the current crossover. The current cabinet, drivers and crossover were designed to work together.

[Chris Roemer]

Re: Need Component Selection Advice Re: Loudspeakers

[QUOTE=petrolSpice;1759659]I pulled apart the loudspeaker and tested the impedance of each driver:

Sub 8ohm: 6.9ohms
Mid ?ohm: 6.8ohms
Tweeter 4ohm: 4.4ohms

With all the drivers disconnected the crossover input posts still gave 0.9-1.1ohms. Does this mean the crossover is bad? The label on one of the coils burned off.

No matter what, I would like to replace the crossovers, tweeters and mids with more modern pieces. Do the mid and tweeter still need to be 8 and 4 ohms, respectively? Or does it depend on the crossover? The sub is 8ohms and will not change.

Are the "posts" the two (powdery looking) solder tabs past the end of the 2 pots in the 1st picture? Is the upper one ground (black?) and the bottom one positive (red?)?

At 1st look, it SEEMS like one of the caps would have to be shorted to get an impedance that low, but they look a LOT more like a poly type rather than an electrolytic. Doesn' seem like a poly would be very prone to shorting on aging like an npe would.

Chris

[rom]

Re: Need Component Selection Advice Re: Loudspeakers

Dear All,

Look at the two parallel poly cap on the first picture bottom right corner. One on them seems burnt. if that is short, only the 0.25mH coil will be connected directly to the two speaker terminal input which would make sense to read around 0.9 ohms and I would guess this reading may include the off set of non zeroed in meter reading with the shorting of the test lead.

Just my guess.

Regards,
Rom

[rom]

Re: Need Component Selection Advice Re: Loudspeakers

The poly connected to the burnt coil by looking at the terminal is also looks suspicious, the encapsulation seems gone. This in on the second picture where the cap leads are shielded and curved around the potentiometer.

Better check each component to very if they are good or bad.

Regards,
Rom

[petrolSpice]

Re: Need Component Selection Advice Re: Loudspeakers

In the first picture look at the two caps in the bottom left corner. The higher one looks as if it popped, and you can see it spilled its guts onto the lower cap. One end of this cap is connected to the burnt coil. All of the other parts minus the burnt coil look visually fine.

The negative input post is where the two yellow wires are going, and the positive is the post about 1" below the negative on in the first pic. The positive post has leads going to the popped cap, the large coil, and the parallel caps in the lower right. Sounds like we've found the problem!

I want to keep the cabinets and subs, replace the crossovers, mids, and tweeters. The mids are about the fall apart, one of the tweeters is already broken, and as you can see one of the crossovers has gone out. I am perfectly fine spending the money to upgrade the drivers and crossovers, I would like to avoid building a new box. Sound quality is not a huge concern.

I have already found some drop-in mids with the same volume requirements (the loudspeakers have a separate built-in mid driver box). I am still looking at crossovers and tweeters. Most tweeters appear to be 8ohm, will these work with an 8ohm crossover, sub, and mid? I basically want to know what components will be electrically compatible.

And then I have no idea what kind of crossover to get...

[Chris Roemer]

Re: Need Component Selection Advice Re: Loudspeakers

In the first picture look at the two caps in the bottom left corner. The higher one looks as if it popped, and you can see it spilled its guts onto the lower cap. One end of this cap is connected to the burnt coil. All of the other parts minus the burnt coil look visually fine.

The negative input post is where the two yellow wires are going, and the positive is the post about 1" below the negative on in the first pic. The positive post has leads going to the popped cap, the large coil, and the parallel caps in the lower right. Sounds like we've found the problem!

I want to keep the cabinets and subs, replace the crossovers, mids, and tweeters. The mids are about the fall apart, one of the tweeters is already broken, and as you can see one of the crossovers has gone out. I am perfectly fine spending the money to upgrade the drivers and crossovers, I would like to avoid building a new box. Sound quality is not a huge concern.

I have already found some drop-in mids with the same volume requirements (the loudspeakers have a separate built-in mid driver box). I am still looking at crossovers and tweeters. Most tweeters appear to be 8ohm, will these work with an 8ohm crossover, sub, and mid? I basically want to know what components will be electrically compatible.

And then I have no idea what kind of crossover to get...

Tell me what you've got there.

I see a 4.0mH coil (big, for the sub), a 0.25mH coil, and the tweeter coil (maybe see if you can read the non-burnt one in the other cab)?

The resistor LOOKS like 5w 25 ohms?

Can't read the uF on the caps at all, help us out here, are all 4 the same?

It would be really great if you could post a drawing showing how the XO parts are wired together. I've made one, but really can't tell where the resistor is wired in. Also, it SEEMS like the mid is "cascaded" off the sub coil?

Chris