Seeking (wiring) expert knowledge

[copperhed]

I know these places are filled with 'experts' of all kinds- I myself am no stranger to audio setups/wiring. I'm seeking some real expert knowledge that eclipses my own. Thank you in advance to whomever helps.

My questions regard wiring and impedence loads, specifically as it pertains to my application. I have a few questions all in the same arena; please bear with me.
1. How is a typical center channel with 2 woofers and 1 tweeter wired internally? Center channels are often made to match their respective single-woofer bookshelf counterparts (as is the case with my setup), but contain an extra woofer. It appears my bookshelf seperates have a 4 ohm woofer and the matching center channel contains 2 8 ohm versions of the same woofer. There is no crossover so it also appears that the 2 woofers in the center channel are simply split from the input terminal to each driver.
2. If the above descrption is the typical wiring setup for a center channel, what does that do impedence-wise with the speaker? I'm guessing this wiring layout makes the center channel see a 4 ohm load by wiring two 8 ohm woofers in this way, thus matching the 4 ohm load to each bookshelf single... therefor the center channel drivers are wired in parallel. Is that correct?
3. Finally, I have a crossover board specifically designed for each of the single-woofer bookshelf seperates. I'm wondering if I can purchase/install the same exact crossover into the center channel and achieve a matching soundstage. Also, I want to make sure there isn't some different ohm load being seen in this center channel crossover than is being shown in the bookshelf seperates; damaging the crossover or rendering it to react differently in the center channel setup. If I can use the same crossover in the center channel, I'm assuming I would just wire the 2 drivers off of the crossover as they were wired prior to the terminal/just as I wire the single driver off of the crossover on the bookshelf seperates. Help? Comments?

I hope this was comprehesible. Thank you (any/all) for your help on this matter.

 

[j_garcia]

That speaker will likely end up a 4 Ohm speaker and is why they selected 8 Ohm woofers for the center, because there are two. The fact that there is no crossover is a bad sign though. Theoretically you could use the same x-over in the center on a speaker like this since it did not have one at all, but generally speaking it is usually more complicated than that due to the dual drivers and I would not expect it to work well without tweaking the x-over design from a straight 2-way speaker.

 

[Swerd]

How is a typical center channel with 2 woofers and 1 tweeter wired internally? Center channels are often made to match their respective single-woofer bookshelf counterparts (as is the case with my setup), but contain an extra woofer. It appears my bookshelf seperates have a 4 ohm woofer and the matching center channel contains 2 8 ohm versions of the same woofer. There is no crossover so it also appears that the 2 woofers in the center channel are simply split from the input terminal to each driver.

Before I try to answer you, please clarify this: You have a center channel speaker with two woofers, 1 tweeter, and NO crossover?

Typically (but not always) such a speaker with two woofers has them wired in parallel as these wires come off the crossover board, making their impedance half of their rated impedance. There are also speakers with two woofers that deliberately use series wiring, or a 2½ way crossover design. But all such speakers would use a crossover between the woofers and the tweeter. I'm confused about what you are asking.

I have a crossover board specifically designed for each of the single-woofer bookshelf seperates. I'm wondering if I can purchase/install the same exact crossover into the center channel and achieve a matching soundstage.

Yes. The same crossover circuit should generate the same crossover frequency for a single 4 ohm woofer or two 8 ohm woofers wired in parallel. But, the cabinets probably have different widths and different driver placements on the front baffle, so the crossover for the single woofer 2-way might not work exactly as planned in your center speaker.

Don't do anything until you are sure I correctly understand your questions. And I'm not sure I do.

 

[copperhed]

That speaker will likely end up a 4 Ohm speaker and is why they selected 8 Ohm woofers for the center, because there are two. The fact that there is no crossover is a bad sign though. Theoretically you could use the same x-over in the center on a speaker like this since it did not have one at all, but generally speaking it is usually more complicated than that due to the dual drivers and I would not expect it to work well without tweaking the x-over design from a straight 2-way speaker.

Thank you for your response.
It seems we're on the same page; you understood my query.
That was the same conclusion I came to- that the two 8 ohm drivers essentially act as one 4 ohm driver through parallel wiring in the center channel... thus making it (essentially) match the 4 ohm single-diver bookshelf counterparts. There IS however a single tweeter in all of the speakers as well (not sure how that affects the equation in the single woofer vs dual woofer setups).
I like that it theoretically would work- that's what I was hoping for. I'm disappointed that you would not expect it to work well because of the straight 2-way design- that's what I was afraid of.
The center channel is rated @ 100 watts, where as the bookshelfs are 75 each. Can you give more thoughts on what might be problematic if I use the same x-over in the center dual-woofer design as the bookshelf single-woofer design?
Thanks again.

 

[copperhed]

Before I try to answer you, please clarify this: You have a center channel speaker with two woofers, 1 tweeter, and NO crossover?

Typically (but not always) such a speaker with two woofers has them wired in parallel as these wires come off the crossover board, making their impedance half of their rated impedance. There are also speakers with two woofers that deliberately use series wiring, or a 2½ way crossover design. But all such speakers would use a crossover between the woofers and the tweeter. I'm confused about what you are asking.

Correct. I have a center channel with 2 woofers, 1 tweeter and NO crossover.

It appears all 3 (8 ohm) drivers are simply wired off of the input terminal... so I'm assuming that's parallel. The single-woofer counterparts (for which the crossover in discussion was designed) has 1 woofer and 1 tweeter, each. In those it appears the 2 drivers are simply wired off of the terminal as well. They also contain a 4 ohm woofer- not sure what ohm the tweeter is but I'm guessing it;s the same in the bookshelves as the center channel. The new crossover is attached to an input terminal with one line out for the woofer and one line out for the tweeter, so I'm just swapping out the current terminal for the new x-over one. What I'd like to do (to know if it is safe/equally effective) is add one of the same crossovers to the center channel, and simply wire the second (8 ohm) woofer off of the woofer line on the x-over, and achieve a closely matched soundstage for ALL speakers.

Yes. The same crossover circuit should generate the same crossover frequency for a single 4 ohm woofer or two 8 ohm woofers wired in parallel. But, the cabinets probably have different widths and different driver placements on the front baffle, so the crossover for the single woofer 2-way might not work exactly as planned in your center speaker.

Don't do anything until you are sure I correctly understand your questions. And I'm not sure I do.

It seems you do understand me here. Thank you for your response. I understand that the cabinets, driver placement, etc. are different and thus may not be an exact match. My main concern is the crossover and it's affect on the two drivers as opposed to one- will the crossover operate in a safe and similar manner to the one 4 ohm woofer setup in a two (parallel) 8 ohm woofer setup? (assuming the two 8 ohm woofers are wired in parallel after the crossover)
Thanks again for your help here.

 

[slipperybidness]

Geez, copperhead.

What brand and model speakers do you have?

Is this a DIY project or did you inherit something from someone?

Post some pics!

I have confidence that the guys on here can set you straight on whatever you want to accomplish. Just be aware that the answer that you get might be "That won't work, don't do that!"

I think you need to post your exact model #s and your final goals and get help.

 

[Nestor]

Correct. I have a center channel with 2 woofers, 1 tweeter and NO crossover.

It appears all 3 (8 ohm) drivers are simply wired off of the input terminal... so I'm assuming that's parallel. The single-woofer counterparts (for which the crossover in discussion was designed) has 1 woofer and 1 tweeter, each. In those it appears the 2 drivers are simply wired off of the terminal as well. They also contain a 4 ohm woofer- not sure what ohm the tweeter is but I'm guessing it;s the same in the bookshelves as the center channel. The new crossover is attached to an input terminal with one line out for the woofer and one line out for the tweeter, so I'm just swapping out the current terminal for the new x-over one. What I'd like to do (to know if it is safe/equally effective) is add one of the same crossovers to the center channel, and simply wire the second (8 ohm) woofer off of the woofer line on the x-over, and achieve a closely matched soundstage for ALL speakers.



It seems you do understand me here. Thank you for your response. I understand that the cabinets, driver placement, etc. are different and thus may not be an exact match. My main concern is the crossover and it's affect on the two drivers as opposed to one- will the crossover operate in a safe and similar manner to the one 4 ohm woofer setup in a two (parallel) 8 ohm woofer setup? (assuming the two 8 ohm woofers are wired in parallel after the crossover)
Thanks again for your help here.

The x-over could be as simple as a cap tied to the terminals of one or more driver. Are you sure there isn't anything tied to each driver terminal?

 

[copperhed]

The x-over could be as simple as a cap tied to the terminals of one or more driver. Are you sure there isn't anything tied to each driver terminal?

There is a cap tied in line with the tweeter at the box terminal input. However, the new crossovers replace the terminal plate and thus the entire wiring system inside.

 

[copperhed]

What brand and model speakers do you have?

Is this a DIY project or did you inherit something from someone?

Post some pics!

I have confidence that the guys on here can set you straight on whatever you want to accomplish. Just be aware that the answer that you get might be "That won't work, don't do that!"

I think you need to post your exact model #s and your final goals and get help.

The bookshelfs are MICCA MB42 speakers. (1 4" 4 ohm woofer, 1 3/4" tweeter [impedence unknown], each)
The center channel is a MICCA MB42-C. (2 4" 8 ohm woofers, 1 3/4" 8 ohm tweeter)

The MICCA MB42 was upgraded to the MB42X with the addition of a quality crossover (among some other tweaks in styling).
Said crossovers are available for purchase from the company to upgrade the MB42 to the sound output of the MB42X.
The crossovers come fully assembled to a matching terminal plate which one simply swaps out with the previous.
The MB42-C does not come with a crossover.
I would like to know if I can install the same crossover built for the MB42 (single 4 ohm woofer with tweeter) in the MB42-C (dual 8 ohm woofers with tweeter) and achieve a closer matching soundstage across all speakers...
I've emailed the company multiple times with no response-
the crossover addition to the MB42's is a significant and impressive improvement. The MB42-C is left sounding flat & warm by comparison; the way the MB42's did before x-over upgrade.

 

[j_garcia]

So there's just no control on the woofers; they are just running at their natural roll off. I agree with Slipperybidness, what's the goal here? Just trying to improve these speakers? X-over is one that was designed for this speaker or is an out of the box 2-way x-over? What's the x-over point for that x-over?

 

[TLS Guy]

The bookshelfs are MICCA MB42 speakers. (1 4" 4 ohm woofer, 1 3/4" tweeter [impedence unknown], each)
The center channel is a MICCA MB42-C. (2 4" 8 ohm woofers, 1 3/4" 8 ohm tweeter)

The MICCA MB42 was upgraded to the MB42X with the addition of a quality crossover (among some other tweaks in styling).
Said crossovers are available for purchase from the company to upgrade the MB42 to the sound output of the MB42X.
The crossovers come fully assembled to a matching terminal plate which one simply swaps out with the previous.
The MB42-C does not come with a crossover.
I would like to know if I can install the same crossover built for the MB42 (single 4 ohm woofer with tweeter) in the MB42-C (dual 8 ohm woofers with tweeter) and achieve a closer matching soundstage across all speakers...
I've emailed the company multiple times with no response-
the crossover addition to the MB42's is a significant and impressive improvement. The MB42-C is left sounding flat & warm by comparison; the way the MB42's did before x-over upgrade.

We are talking about bookshelves at $79 per pair!

Now according to Micca the MB42 and the MB 42C do have crossovers.

The MB42X is stated to have a second order 12 db per octave crossover.

Now the only way your speakers could work without a crossover is if the tweeter was a piezo tweeter. However from the pictures it is highly unlikely the tweeter is a piezo, but it is just possible. I suspect you are missing something. Any moving coil tweeter connected full range will burn out even at very low volume, so that is an impossibility.

The manufacturer says that the speakers are second order ported. That is impossible, so we are talking about the red neck of the red neck speaker company here.

To answer your question though, the center having two woofers will have 3 db of gain compared to the bookshelf speakers. So the same crossover will not work. However I doubt the red necks at MICCA know that, so probably anything you do just might be an improvement.

You can't build anything any good for the price of those units. If you are serious bout good sound ditch those and don't waste anymore time on them. Do yourself a favor and get some decent speakers.

 

[Nestor]

There is a cap tied in line with the tweeter at the box terminal input. However, the new crossovers replace the terminal plate and thus the entire wiring system inside.

There's your x-over.

 

[j_garcia]

You can't build anything any good for the price of those units.

I beg to differ, and I think so would Andrew Jones. The BS22LR is in that price range and they are quite decent for that money.

I would like to know if I can install the same crossover built for the MB42 (single 4 ohm woofer with tweeter) in the MB42-C (dual 8 ohm woofers with tweeter) and achieve a closer matching soundstage across all speakers...
I've emailed the company multiple times with no response-
the crossover addition to the MB42's is a significant and impressive improvement. The MB42-C is left sounding flat & warm by comparison; the way the MB42's did before x-over upgrade.

While the woofers will exhibit the proper impedance, that does not mean the x-over will work equally as well as the bookshelf version. It might work and it might not, depending on the type of x-over they designed. Did you already buy another x-over? My advice would actually be to pick up a third MB42 and use that as a center before looking to mod the other center - sell the old MB42-C. If the company didn't reply and haven't released a x-over for the C, it probably won't work.

 

[copperhed]

Just received the following response to my email query from the company:

The crossover upgrade for the MB42 will not work well for the MB42-C. The tweeter output will be about 2-3dB too low. However, the MB42X-C will be available in about a month that should work well in combination with the MB42X. The MB42X-C has the appropriate crossover that is optimized for center channel use.

 

[j_garcia]

Well, there you go then

 

[copperhed]

We are talking about bookshelves at $79 per pair!

Now according to Micca the MB42 and the MB 42C do have crossovers.

The MB42X is stated to have a second order 12 db per octave crossover.

Now the only way your speakers could work without a crossover is if the tweeter was a piezo tweeter. However from the pictures it is highly unlikely the tweeter is a piezo, but it is just possible. I suspect you are missing something. Any moving coil tweeter connected full range will burn out even at very low volume, so that is an impossibility.

The manufacturer says that the speakers are second order ported. That is impossible, so we are talking about the red neck of the red neck speaker company here.

To answer your question though, the center having two woofers will have 3 db of gain compared to the bookshelf speakers. So the same crossover will not work. However I doubt the red necks at MICCA know that, so probably anything you do just might be an improvement.

You can't build anything any good for the price of those units. If you are serious bout good sound ditch those and don't waste anymore time on them. Do yourself a favor and get some decent speakers.

This is why I didn't mention the speakers in discussion up front- too many folks are distracted by price/brand and feel the need to offer their (unrequested) advice/criticism on what products one should buy. This is a learning process and principle of electronics query that can be applied across the board to any price speaker setup or build- the understanding of x-over wiring and how drivers of different configurations respond to it.

I'm actually quite pleased with the 80$ speakers, if not amazed, and the $50 center channel is impressive too. Especially given the price. The build quality on these units is remarkable. There are gaskets between all the components and enclosure. There is internal rigid bracing to the box. Hex scews are used throughout. The internal wiring is wrapped in foam. I've seen less, sometimes far less, quality on products costing 2, 3 ,4 times a s much.
The sound is quite good for such small, inexpensive speakers. After the x--over upgrade, the bookshelfs sound actually incredible for what they are. The purpose behind the purchase is my preference for small, simple- and affordable- setup. Hope you aren't one of those folks who thinks paying more always means getting more. Or that 3000 watts = a decent home theater. I'm not out to impress anyone here; intending to satisfy my needs (and hopefully learn something in the process)- nothing more.

 

[copperhed]

Well, there you go then

Yea, not what I wanted to hear exactly... but maybe... if they can make the center channel crossover upgrade available for my unit (at least for me ) as they have for the seperates. These speakers really are quite nice.

 

[j_garcia]

I don't recall if the drivers were different between the two, but I'd suspect if the x-over for the bookshelf works, the one for the center will be backwards compatible as well and hopefully they will offer it separate.

 

[copperhed]

I don't recall if the drivers were different between the two, but I'd suspect if the x-over for the bookshelf works, the one for the center will be backwards compatible as well and hopefully they will offer it separate.

The drivers are the same in the new and old bookshelfs. The drivers are (presumably) the same in the new and old center channel. The drivers are not the same in the bookshelfs and the center channel (4 ohm vs dual 8 ohm, respectively). Hopefully it will be backwards compatible as it was on the bookshelfs, but my concern is that not many of the old center channel seemed to have sold. So the demand for the individual x-over upgrade is less. I'm going to beg them to sell/send me the correct x-over from the new model.

 

[Swerd]

copperhed

What makes or breaks a speaker is the crossover. It is equally, if not more, important than the drivers. I've heard DIY speakers made with cheap drivers, but had a carefully designed crossover, that sounded rather good. Many inexpensive, and some not inexpensive, commercial speakers suffer because the manufacturer skimped on crossover design.

That's why I (and others) couldn't believe that Micca sold speakers without any crossover. The capacitor in series with the tweeter, to keep the tweeter from rapid failure, doesn't quite qualify as a crossover. It is highly unlikely that two drivers will sound balanced, and make no unwanted distortion or noise, without some help from a crossover. At least you didn't pay much for them .

A crossover circuit does more than provide low-pass filtering to the woofer and high-pass to the tweeter. It should evenly balance the sound across the all important mid-range where the crossover operates. And, it should equalize, as much as possible, any imbalances that come with the particular drivers and cabinet design. Beyond that, a really good crossover will allow a speaker to create a realistic spatial image that allows recorded music to sound more like real musicians and less like sound coming out of a small box.

To address your original question, a 2-way speaker with a woofer, tweeter, and crossover, really operates more like two separate drivers and not like two drivers in parallel. The low-pass filter keeps the woofer from operating above a certain frequency, and the high-pass filter keeps the tweeter from operating below it. If a crossover is at 2000 Hz, below 1000 Hz you hear only the woofer and above 4000 Hz you hear only the tweeter. At the crossover frequency ± an octave, roughly 1000 Hz to 4000 Hz, both speakers can operate at the same time, but at varying levels. At the crossover frequency of 2000 Hz, they will each make 50% of the sound. But they are not considered the same as two drivers in parallel.

The impedance of a speaker is never a simple constant value. It varies widely across the audio spectrum. It's measured by a full frequency sweep. The individual drivers, the crossover, and the cabinet design all affect the resulting frequency vs. impedance curve.