Cross-over in specs?

Talon_Sr

Hi, I'm still a newb here at this forum, but have been an audiophile for some time. Question: Do speakers themselves come with active cross-overs, or they always passive until you use an external cross-over? And if so, are all Polks (specifically Monitor 75 T) employing active cross-overs? And how do you know if a speaker uses an active x-over? Is it that rare that it would definitely be listed as one of the speaker's features? I hardly ever see this listed as a spec in the advertisement for a particular speaker. Do you have to dig deeper and find the product sheet?

pitdogg2

Talon_Sr wrote: »

Hi, I'm still a newb here at this forum, but have been an audiophile for some time. Question: Do speakers themselves come with active cross-overs, or they always passive until you use an external cross-over? And if so, are all Polks (specifically Monitor 75 T) employing active cross-overs? And how do you know if a speaker uses an active x-over? Is it that rare that it would definitely be listed as one of the speaker's features? I hardly ever see this listed as a spec in the advertisement for a particular speaker. Do you have to dig deeper and find the product sheet?

I do not think anything as cheap as a monitor75T will ever have a active XO. Most were very expensive like these https://www.meridian-audio.com/en/

Talon_Sr

Yeah, I was afraid of that. Well, then, when you bi-amp a speaker, such as the 75s, how do you know if the amp is providing power to the correct driver at the correct frequency range? Or don't you really know that with either active or passive x-over for 100% certainty? You sorta have to hope that it is according to spec? Thanks for the response.

pitdogg2

Well to do it right (bi-amp) you will need active XO plain and simple. IF you bi-wire then you are using the internal XO and just losing the inferior strap that connects both sets of posts. Most will bi-wire anything in that price range I see nothing extra by bi-amping such a speaker as M75T...YMMV

Talon_Sr

I'm using the bi-amping ability of my Receiver (it's not bi-wiring). And, yes, I know that doing so the "right" way would be utilizing a separate exterior amp, but that's besides the point.

Dennis Gardner

Talon_Sr wrote: »

Yeah, I was afraid of that. Well, then, when you bi-amp a speaker, such as the 75s, how do you know if the amp is providing power to the correct driver at the correct frequency range? Or don't you really know that with either active or passive x-over for 100% certainty? You sorta have to hope that it is according to spec? Thanks for the response.

When you separate the signal by using 2 sets of posts on a speaker, you are sending the same full range signal to each set of speaker posts. The internal crossover separates out what it needs and absorbs the other frequencies that it doesn't need. This is a passive system since the crossover is not electronically controlled.

Active (electronic) crossovers are used on a low level (preamp) signal to separate the frequencies out prior to a channel of amplification for each frequency and then sent to raw drivers that don't have a passive crossover attached.

Active crossovers require an amp for every frequency if no passive components are to be used. A 3 way speaker system Woofer/Mid/Tweeter would require 6 channels of power amp and a 3 way active stereo crossover or 2-3 way active mono crossovers.

tonyb

Is there something your unhappy with about the sound that's got you questioning crossover points ?

rooftop59

Bi-amping using a receiver has been discussed ad nauseam on this forum. It doesn't do anything, its simply a marketing gimmick. You have one power source, so giving it two wires from the same source won't increase the power. Good luck!

F1nut

Talon_Sr wrote: »

I'm using the bi-amping ability of my Receiver (it's not bi-wiring). And, yes, I know that doing so the "right" way would be utilizing a separate exterior amp, but that's besides the point.

No sir, that is exactly the point. Without separate amps/power supplies and active crossovers, you're not bi-amping.

Talon_Sr

Ok, that's what I really wanted Dennis. The science behind it. I don't want to stir up a flame post here, but my receiver has 9 discrete channels of power. If two are used for bi-amping, then it is not a shared source. The 7.2 is retained while both fronts are bi-amped, not bi-wired, not shared power.

Hermitism

Different discrete channels, but same shared power supply. That's the problem.

F1nut

As noted, all the channels share the same power supply, which is why when more than 2 channels are driven, the less wpc the AVR can provide.

Talon_Sr

Ok, but if the receiver is rated for 9 channels at 135 WPC into 8 ohms at 1% THD across the 20-20k, then my fronts are actually split into four speakers with 135wpc going to two physical enclosures. Now that's what makes sense to me. How is that incorrect? This is good, keep it coming. I'm learning.

Talon_Sr

But even if it's less than 135wpc because all channels (not just two) are driven, would it still not be better than just using seven channels and letting two just sit there doing nothing? I mean, it's not like the extra two channels' power is redistributed to the other seven channels if you don't have a load on them, correct? And even if it is a marketing ploy, it certainly would not be detrimental in nature to use the bi-amping oprion. It should be at least marginally better than NOT using the option acoustically speaking.

Dennis Gardner

If your receiver is the 1523 in your signature........In theory, it works. In reality your power supply admittedly is only rated on the back of your amp to pull 330 watts of electricity, so it can't produce the 9x135 unless it is pulling at least 1215 watts from the electrical service at the wall.

Magic is the only way for a power supply to produce 4 times as much power as it takes as no power supply is 400% efficient.

rooftop59

If u look at bench tests for almost any receiver- even high end ones - 1 channel driven meets or exceeds specs, 2 channels driven meets spec so a good, higher end receiver, and 5-7 channels driven has a considerable drop, sometimes as much as a third. You want to look at bench tests by mags such as sound and vision and u will quickly notice the trend. So many receivers will drop from 100 to 30-40 watts 5 channels driven. So I ask u, what do u think "bi-amping" will do at that point?

rooftop59

Talon_Sr wrote: »

But even if it's less than 135wpc because all channels (not just two) are driven, would it still not be better than just using seven channels and letting two just sit there doing nothing? I mean, it's not like the extra two channels' power is redistributed to the other seven channels if you don't have a load on them, correct?

Actually it kinda is. Less channels equals more power per channel on most receivers.

F1nut

For starters, it's rated at 135 wpc with 2 channels driven. The more channels driven, the less wpc.

So, let's say it delivers 100 wpc with 7 channels driven and 80 wpc with 9 channels driven when you ghetto bi-amp. You now have 80 watts going to the woofers of your ghetto bi-amped speakers and 80 watts going to the tweeters, of which almost all of that going to the tweeters is wasted. Bottom line, the woofers are likely to get less power by ghetto bi-amping.

This is besides the fact that to bi-amp, you must use active crossovers.

Talon_Sr

Well if it comes down to more clarity vs. more SPL, I'll take the former. And I thought that was what bi-amping was all about.

Dennis Gardner

No one is bashing your idea. Receivers have used a number of fancy features that are "hooks" for the buyers to think they are getting much more for their value in their lineup. Assignable amp channels are necessary to have a second or third zone in a receiver and they just figured that for basically no extra $$$ they could advertise biamping as a feature because they already built in the assignable channels for the other zones.

Again, in theory it works, in reality though it just works okay.

Talon_Sr

rooftop59 wrote: »

Actually it kinda is. Less channels equals more power per channel on most receivers.

Is this true even for the D3 amps?

Talon_Sr

Dennis Gardner wrote: »

No one is bashing your idea. Receivers have used a number of fancy features that are "hooks" for the buyers to think they are getting much more for their value in their lineup. Assignable amp channels are necessary to have a second or third zone in a receiver and they just figured that for basically no extra $$$ they could advertise biamping as a feature because they already built in the assignable channels for the other zones.

Again, in theory it works, in reality though it just works okay.

Well, that's what I would like to compare. Is it still better to bi-amp these extra trwo channels, or just let them sit there as I have no plans to go 9.2 ever?

Talon_Sr

F1nut wrote: »

For starters, it's rated at 135 wpc with 2 channels driven. The more channels driven, the less wpc.

So, let's say it delivers 100 wpc with 7 channels driven and 80 wpc with 9 channels driven when you ghetto bi-amp. You now have 80 watts going to the woofers of your ghetto bi-amped speakers and 80 watts going to the tweeters, of which almost all of that going to the tweeters is wasted. Bottom line, the woofers are likely to get less power by ghetto bi-amping.

This is besides the fact that to bi-amp, you must use active crossovers.

Why are any amps going to the SWs? Both SWs are line level outs to powered subwoofers. So the SWs are not in the picture.

Dennis Gardner

No one has mentioned that most tweeters are only rated for around 30 watts, so even if you put 135 watts into the tweeter, the crossover will slough off the extra power and only allow the rated power through to the tweeter. 135 watts actually pumped into any of Polks tweeters will melt them.........this is why most of the time, using the designed crossover with a nice stout amplifier rated for good high current power is the best choice for speakers, unless they are of extreme design and build perimeters.

Hermitism

I asked the same questions a year ago. My problem was I didn't understand exactly what bi-amping was. I thought it just meant the use of two amps. And I saw so many people here using a separate amp with their AVR, so I figured that they were bi-amping. I thought using a separate amp for the front two or three speakers and using the AVR for the surrounds was bi-amping. I didn't realize both amps had to be going to the same speaker. Sometimes you just don't know stuff until you ask. If I had to pay a dollar for every question I've asked in the last year, I'd owe the forum members more money than I paid for my system.

Hermitism

Talon_Sr wrote: »

Why are any amps going to the SWs? Both SWs are line level outs to powered subwoofers. So the SWs are not in the picture.

He is referring to the woofers in the speakers, not a separate powered subwoofer.

F1nut

This what bi-amping is and is not. It references 2 channel, but the same applies to multi-channel.

http://sound.westhost.com/bi-amp.htm

From the article,

The most common question I get is ...

"Do I need to disconnect the passive crossover in my speakers?"
The answer is ... Yes, otherwise you are not really biamping at all.

F1nut

Well, that's what I would like to compare. Is it still better to bi-amp these extra trwo channels, or just let them sit there as I have no plans to go 9.2 ever?

What does work and work well is replacing the stock brass plate jumpers on your speakers with high quality speaker cable.

Talon_Sr

Hermitism wrote: »

I asked the same questions a year ago. My problem was I didn't understand exactly what bi-amping was. I thought it just meant the use of two amps. And I saw so many people here using a separate amp with their AVR, so I figured that they were bi-amping. I thought using a separate amp for the front two or three speakers and using the AVR for the surrounds was bi-amping. I didn't realize both amps had to be going to the same speaker. Sometimes you just don't know stuff until you ask. If I had to pay a dollar for every question I've asked in the last year, I'd owe the forum members more money than I paid for my system.

No, I understand that I'm not bi-amping by using individual amps for fronts, rears, etc. I am specifically splitting my two fronts into virtually four speakers with the duties of mid to high (probably 2.5KHz and up) taken care of by one amplified channel and the mid to lows (everything below 2.5KHz) taken care of by another separate amplified channel. One speaker effectively becomes two within the same enclosure. Is this not correct?

Talon_Sr

F1nut wrote: »

What does work and work well is replacing the stock brass plate jumpers on your speakers with high quality speaker cable.

Like oxygen-free?

Talon_Sr

F1nut wrote: »

This what bi-amping is and is not. It references 2 channel, but the same applies to multi-channel.

http://sound.westhost.com/bi-amp.htm

From the article,

Question about the block diagram of that link: What if the signal source is sent through hi and lo pass filters that were in the receiver and then amplified discretely and separately by the amplifier prior to being sent to the speakers hi inputs and low inputs. Would this not qualify as biamping? IOW, the receiver has its own electrical XO which is enabled only when the Bi-amp option is selected. Is this plausible?