Does anyone make a crossover to be used on an INPUT?

I want to rig up a subwoofer, but I know that crossovers are expensive, and since I am running high powered commercial amps, I'd need a hefty setup. Then comes the need to combine the left and right channels without loosing stereo separation.

I decided to go another route, My power amp was 600W (RMS). stereo. I got a good deal on another amp that is also a stereo commercial amp, rated at 500W RMS. Both amps are bridgable. The plan is to run the outputs from my preamp into Y adaptors and feed the left and right channels to BOTH amps. One of these amps I'll bridge and use that to power a single subwoofer speaker.

However, I need a means to send only the bass to the amp that powers the Subwoofer. Is there any sort of crossover made that goes in the input of the power amps, after the preamp?

I have also thought about just putting an equalizer into the input of the amp that feeds the subwoofer and raise the low end of the frequency and cut the highs. I'm not sure if that will adaquately work or not. I'll probably try it, but I have not yet built my subwoofer cabinet.

Either way, I know that 1100 watts rms is more than enough for a home stereo...

Reply to
oldschool
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Lookup "low pass filter."

I think they only had 1000W in total at Woodstock...

Reply to
Fred Smith

Commonly done, even in my son's old Altec computer speakers.

The advertising for Deep Purple's Australian tour around 1975 focussed on "the world's most powerful PA - 10,000W!". They always were more about quantity than quality.

Clifford Heath.

Reply to
Clifford Heath

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Come in quite a range. 200hz is one of many. You could do it all with passive filters.

Most sub-woofers are configured as pass-through devices. Feed the full signal to the SW, and the filtered signal from the SW to the rest of the drivers. If you have separate amps, similarly, but the output from the SW is filtered line-level.

Peter Wieck Melrose Park, PA

Reply to
pfjw

I can make my ears bleed with Maggie speakers and a 200-watt amp in the one system, and AR speakers and also a 200 watt amp in another.

The difference between 200A and 1,100A is only a bit over 5dB anyway, so th e question becomes "why"? And unless you enjoy flaming drivers, what sort o f speakers are capable of handling that level of power for any sustained pe riod of time? Sure, transients are a bitch, but a reasonable power-supply at 200 watts will handle them as well as 1,000+ amp.

Peter Wieck Melrose Park, PA

Reply to
pfjw

Sure.

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for one.

I use an XM9 in my own speaker system. Each side has a midrange/tweeter/midrange array with a passive crossover, powered by one amplifier, and a side-mounted subwoofer powered by a second amplifier. The XM9 divides the signal, after the preamp and before the amplifiers, crossing over at 200 Hz.

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20+ years since I build it, and I'm still thoroughly satisfied with the results.
Reply to
Dave Platt

First of all, combining the channels by definition means losing all the sep aration. Also do not try to combine outputs of amplifiers, it has a very ba d effect on some. It has to do with DC and is insidious, sits there dissipa ting power uselessly. It can actually fry the amp in certain cases.

They make what you want for cars. Those ones that drive around "BOOM mufuka BOOM mufuka BOOM mufuka...". This is exactly what you want. It is active s o it needs power, if 12 volts that is a simple matter because it does not p ull much current. A spare wall wart in your junk drawer should do just fine . Most of them also have a continuously variable crossover frequency as wel l. That comes in handy. Crossover too high and the subs might be too boomy, too low and the highs are taking too much power which they frequently can' t use. Some have the option of combining the two channels, but at line leve l you can do it with two resistors and have practically no loss.

If you want it really loud, you might want a low pass passive filter on the woofers, such as in a regular crossover. This way if the bass amp clips it does not screw up the sound as much. But you probably won't need it. You a re not really likely to clip anything with that power unless you have a hug e outdoor party. In fact, with some exceptions people go to a party to ming le. For me, I like loud good sounding music, but not the whole time. People who just crank up the radio bug me. When I listen, everybody shuts up whil e it is playing and then there is an intermission between songs. Then there is time to talk, or maybe take requests, or whatever.

But seriously, go with the active (line level) crossover, you'll be glad y ou did. Most of them even have level controls, some power amps do not. Solv es that, that is burns that bridge if you come to it.

There is a way to combine to a woofer on the output side but it loses a bun ch of power and is totally unsuitable for bi-amping. Actually if you want t o change your mind and go with four really full range channels, I can build you a little box that is like quad which is almost the same as Dolby surro und.I mean native Dolby surround that they should never have been allowed t o put their name on because it was so common in the 1970s+. I used the tech nique for movies with my Advent five foot TV, which BTW was the only one in town with really hot tubes and near perfect geometry and convergence. But like on Days of Thunder you heard the cards actually go around you when the camera angle was that way. The Enterprise would take off and seem to go a bove you on the screen and the speakers sounded like it. It is good for som e music, but not all. Some is mixed funny, like all the bass in one channel , like The Swinging Medallions - Double Shot Of My Bsby's Love or Beatles - Taxman. Those are not suited well for such a system.

It sounds like Dolby without any delay or anything like that. In that respe ct it is true high fidelity because it only puts out what goes in. With all the effects, Dolby surround is not high fidelity, it bastardises the sound with.

Actually with speaker that have really good imaging it almost sounds like t here are rear speakers. But you'll probably not find them with that kind of power handling without mucho dinero, and very low efficiency.

So really, just go to one of those car audio places and tell them what you want, most likely they have it on the shelf already. You don't need an ultr a high fidelity one,just low distortion, and very importantly, LOW NOISE. W hile the levels are line level, you are dealing with it after the volume co ntrol. So any noise introduced by the unit will still be there.

Reply to
jurb6006

resistor capacitor (RC) low pass filter.

NT

Reply to
tabbypurr

Yep, this looks just what I want. I've seen these but never knew what they were for....

Thanks

Reply to
oldschool

There no need to sum bass in stereo, just use one channel. That can cause that channel to be different with loading. You make easy line level passive, but what order, and how is that going to mix with upper, phase and frequency. Seems like a full active crossover of all three speakers will work best, but you still have to determine order of filter and frequency for combining.

Greg

Reply to
gregz

That depends on what you listen to. Some music is mixed differently.

Reply to
jurb6006

When I built my tube stereo around 1968 to 71, I had an idea that was ahead of it's time, and that was to create a 3 channel system. I had 3 mono power amps so why not.... Back then, Quad sound did not exist yet, at least not in consumer electronics. But my idea was to create a system that not only had 3 channels, but the rear channel was to have a delay, so it sounded like a huge auditorium. I got my hands on both a tape loop delay unit, which was quite a neat sounding device, but needed constant attention because I had to make my own tape loops using some reel-to-reel tape and splicing it to form a loop. Eventually I got tired of the constant hassle of making and replacing the tape (which did not last long), and switched over to a spring reverb tank device, modified from a guitar amp circuit.

Anyhow, to get that 3rd channel, I simply added a 3rd RCA jack to the preamp, and put an equal value resistor from the Left and from the Right channel to that 3rd jack. That worked, but I lost some stereo separation. That lead to adding a switch for those resistors, so I could switch off the 3rd channel but regain the true stereo sound. A year or two later I found a better solution. I used a second stereo preamp with the resistors in place but had all the inputs with Y adaptors feeding each preamp. Eventually that too was replaced by an equalizer, which had it's own preamp circuits and that became the final solution to achieve the 3rd channel.

Back then, there was no such thing as a sub woofer, at least not for home electronics. However I believe they had subs in use for theaters and such.

But the Subs bring back the 3rd channel requirement (combined L + R). So, I learned by my past trial and error that achieving a 3rd channel is not all that difficult, as long as there is some sort of preamp circuit in place, rather than just using resistors.

Since posting this message, I have looked at some schematics for these low pass filters, as well as reading articles about them. They are basically a preamp circuit combined with the filters to separate the frequencies. Now that I have looked at these devices and understand how they work, it's not all that difficult to achieve what I want. The only drawback now, is the price of these filtering units. ($600 and Up). Of course I'll have to see what I can find in the USED market, and I am also wondering if they sell just the pre-assembled circuit boards on ebay or other places. From what I'm seeing, these are just small circuit boards, with a few Op-Amps and the passive components to achieve the filtering. One board for each channel, a power supply, and a few potentiometers to "tune" them....

These pre-assembled circuit boards seem to be the "kits" in this day and age. You buy the boards, mount them in a box, add a power supply and some pots, switches, jacks and you have a complete device. They are made for amps, pre-amps, test equipment and lots of other stuff. So I wonder if they are made for pass filters????

Reply to
oldschool

Huh, what? If by 200A and 1100A you mean 200 watts and 1100 watts, then 5 dB is not accurate. It is more like 7.4 dB. I expect you did this in your head and with a factor of 2 twice (6 dB) and accounted for the remainder in the wrong direction.

I find oldschool amusing. I've read articles about using a 10 watt amplifier (per channel) to fill a room with sound. So using a 50 or 100 watt amp to keep it far away from the slightly increased distortion from running near the limit would be somewhat reasonable. But 1100 watts in a home is pretty pointless. I guess you could get a volume control that goes to 11 and keep it set below 1. Even then you might need a vernier adjustment to be able to actually control the volume to a reasonable level. lol

Think of it this way... In college I worked on a chemical instrument to measure light absorption of solid samples by shining an intense monochromatic, pulsed light source on the sample and then using a microphone to detect the sound vibrations this produced. In that setup we used a light source that produced around 10 watts of white light. If we had used 1100 watts we would have burnt up the sample we were working with... I'm just sayin'

--
Rick C 

Viewed the eclipse at Wintercrest Farms, 
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Reply to
rickman

Absolute Chinese crap amplifier.

--
Jeff-1.0 
wa6fwi 
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Reply to
Foxs Mercantile

I read this twice today, and laughed both times... I guess this must be a nearly universal occurrence nowadays.

Reply to
John-Del

I've built boards to high/low pass, etc. Not much to it. Look around, I think Marchand was mentioned.

Greg

Reply to
gregz

Marchand has a lot of them, but the cheapest one was well over $600. Thats out of my price range.

I found some boards on ebay, they look to be complete two channel in, one out, with all the filtering. They need to be put into a box and a power supply added, as well as in/out jacks. They cost $10 or less. I'm thinking about ordering one of them. I can easily build a power supply or maybe just use a wall wart. They are pretty simple, one op amp IC for each channel and some passive parts. One model only had 2 pots, (volume in, volume out). The other model has 3 pots, the third one is to adjust the cutoff. If I get one, I'll probably choose the 3 pot one.

Reply to
oldschool

sounds crazy

NT

Reply to
tabbypurr

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I've used one of these and it seems to work fine. For $5 delivered it's hard to not try it.

--
Shaun. 

"Humans will have advanced a long, long way when religious belief has a cozy  
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Reply to
~misfit~

8<

What's the point of it? A couple of RCs does the job without waiting for delivery or paying a thing. Or using a psu, or adding noise to your signal.

NT

Reply to
tabbypurr

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