This active crossover will be good for my speakers?

[CosmicJazz]

Hm.. so if the output voltage is just equal to power amp input sensitivity, it's already okay?

I was thinking that the output voltage must 2 times greater, because if not, depending on how how loud you listen and how large is your room, you would end up with the volume knob all the way up to achieve the desired volume level..

No?

 

[Julf]

Hm.. so if the output voltage is just equal to power amp input sensitivity, it's already okay?

Yes.

I was thinking that the output voltage must 2 times greater, because if not, depending on how how loud you listen and how large is your room, you would end up with the volume knob all the way up to achieve the desired volume level..

Nothing wrong in your thinking, but what's wrong with having to turn the knob all the way to get full volume?

 

[CosmicJazz]

I was thinking that is just a way to prevent you need more volume, and not be able to achieve, or have to work all time with the knob close to maximum could somehow put the preamp in "stress"...

Anyway, in resume, the vital specs to consider when checking the compatibility between preamp and active crossover and active crossover with power amps are?

Thanks!

 

[Julf]

I was thinking that is just a way to prevent you need more volume, and not be able to achieve, or have to work all time with the knob close to maximum could somehow put the preamp in "stress"...

No, the knob position as such has no effect on the "stress" on the amp, what matters is the actual level.

Anyway, in resume, the vital specs to consider when checking the compatibility between preamp and active crossover and active crossover with power amps are?

Pretty much just signal level.

 

[CosmicJazz]

hm... can you give a example about the verification of signal level? just this is somehow vague for me...

Many thanks...

 

[Julf]

hm... can you give a example about the verification of signal level? just this is somehow vague for me...

In your case it mostly doesn't matter, as the crossover has adjustable levels.

 

[gene_stl]

You are worrying about a lot of things you shouldn't worry about.

Active crossovers will ALL drive any power amp. Stop worrying about that. The only unusable (MAYBE) combo would be if you were able to find some old tube powered active crossovers from the 1960s (Marantz made some and I think Audio research may have built some in the 70s and there were probably others) and then try to make it drive a transistor amp. that was the only headache we had when tubes and transistors were around simultaneously. Even then it would probably work.

All you have to worry about is whether your power amps are balanced or unbalanced and whether you active crossover matches that.

As far as amplifier "sound signature" back in the day the goal was for amplifiers to be a "straight wire with gain" It should add no sound and in a tri amp set up most don't. The tube sound many tubophiles are so proud of is usually distortion. I use Pioneer M22 class A amps on the top two channels. But I have been considering selling them for something more modern and energy efficient. They put out about 300 watts of heat for one tenth that much audio power.

Regarding power, I would like to mention one SLIGHT disagreement with the above or more of a concern regarding power. If you have too powerful a tweeter amp(and mid range too actually) and don't have tweeter protection. (Capacitors and fuses) one day you will drop your tone arm and the tweeter diaphragms will come flying out of the front of the tweeters. I am sure Fostex will be very pleased to rebuild them for a significant fraction of the cost of a new one. But the Midrange and tweeter amps should be no more than about double the music power rating of the transducers. I had my Beryllium tweeters (a square of four of them) fused at 250 milliamps. When I did that I was sure the fuse would blow and I would need to go up to 500 milliamps. I had the 500s at the ready. But the 250s never blew. You don't want to go too big on the fuse and have the voice coil protect the fuse.

One of the GREAT advantages of new modern digital equipment (such as the four Crown CTi series power amps I just picked up for 100 each) is that they have digital limiters. You can set in a way not possible before the limit of power fed to the speaker. In other words ACTUALLY protecting the voice coil. No analog unit does that . Until it limits it does nothing. Would also protect against the aforementioned tone arm drop.

I have been using a 12 db /octave slope for 45 years. I dream of 48 db /octave.

You will want to have an accurate sound measuring microphone and software. I have been using for ages a 1/3 octave spectrum analyzer. Now there is software that can do it with a sound card. You use these to set your tweeter and mid range levels. It is sometimes called a "shelving" adjustment, because of the presumption that the drivers have somewhat flat response. You will also want to consider whether your horn is constant directivity or not depending on how old the design is. I have some PA active crossovers that have a CD switch which you can throw if you are using CD horns and it changes the in band slope.

I don't believe you can hear voice coil alignment. This was first hyped by Technics in the early seventies. I also don't believe you can do it without DSP which Technics claimed they did as did many many other speaker makers. Some of the solid gilt that Paul Klipsch mentioned in 1953. I met him once in the the seventies. He was cranky. "the Dope from Hope"

 

[gene_stl]

When the Behringer does its A/D and D/A conversion it probably does so at 32 bits which is , as has already been noted, so much better than the
10 to 12 bits of your vinyl analog signal (if you are lucky) that you will never hear it.

 

[sergeauckland]

When the Behringer does its A/D and D/A conversion it probably does so at 32 bits which is , as has already been noted, so much better than the
10 to 12 bits of your vinyl analog signal (if you are lucky) that you will never hear it.

The Behringer DCX uses a SHARC processor which works at 32 bit.. https://www.analog.com/media/en/new...uct-highlight/SHARC_Proc_Family_(C)_Final.pdf

Many pro products use SHARC processors as they come with a very well sorted library of applications, so generally can be relied upon to be as good as they can be. I have confidence in any product using SHARC.

S

 

[Julf]

When the Behringer does its A/D and D/A conversion it probably does so at 32 bits which is , as has already been noted, so much better than the 10 to 12 bits of your vinyl analog signal (if you are lucky) that you will never hear it.

It might process in 32 (or more) bits, but the actual A/D and D/A conversions won't be more than 20 bits or so - still way more than you need...

 

[CosmicJazz]

Hello guys,

Thank you very much for all the explanations, very grateful about that.

Everything is clear, besides two topics that I will tell here to see if I understood, appreciate more clarification about.

I understood the relation between low power for the horns and tweeters, to prevent damage of a tone arm drop accident situation for example, but I think no quite understood the other assumption about why the low power (just what this very sensitive drivers need) it will be better, so even if I not push the super tweeters and horns beyond their limits, the damage still can occur? this was not clear for me...

Gene, if you try to elaborate again this situation for me, why low power for this drivers are more recommended, I really appreciate... can you try in a more simple way for me to understand?

The rest of the discussion I understood, thanks guys!

 

[gene_stl]

The tweeter amplifier should be sized so that it can deliver the maximum power that the tweeter can accept without "clipping" (flattening the tops of the sine waves). This is so your tweeters won't get burned out or exceed their mechanical displacement limits. As mentioned this can occur if a tone arm gets dropped. But also if some other component upstream puts out a sudden unexpected noisy signal that makes to the input of the tweeter amp by whatever unintentional or accidental occurence have a large amplitude input exceeding the power handling capacity of the tweeter..

If you put a 300 watts per channel amplifier on the input of your tweeter it will have the ability to kill your tweeter. It may never do it and the signal will be very clean. But it won't sound different than a smaller amp because it would be the tweeter that would end up limiting the sound. It would run out of headroom its own headroom first. But the amp could keep going and unwind the voice coil or burn it up or tear the tweeter suspension surround.

The 50 watt "music power" rating already includes some headroom.

Crown amps (and some other pro amps) have sophisticated limiters that actually pay attention to the recent history and can limit or not limit according to a computerized (in the DSP processor) estimate of the channels history. Also with three similar stereo amps you would not need the separate crossover because the DSP input modules can do the crossover too. The limiter does not cause distortion if overdriven. It simply automatically and instantly reduces gain to protect the tweeter and other drivers. Behringer , Drive Rack, and miniDSP also have limiters but I don't think they are as sophisticated as the Crowns. But they would be enough to protect your system.

This seems complicated but another "fact" you should know is this. Picture a party and you have your system playing. (not triamped but using a high level passive crossover after an amp). A drunken guest says "YEAH ,TURN IT UP!!" or drops the tone arm. At that point the crossover will send all the electrical energy to the tweeter and blow it up. This is a complete and total classic occurence if you work at a stereo repair shop (as I used to)

 

[CosmicJazz]

oooh I understood now, I was thinking that the recommendation for lower power amps according to the tweeter had some to do with sound quality, some technical parameter about synergy and signature sound of a low power amp, stuff like that... but no, the whole concept is based to prevent an accident, interesting, because as you said, this accidents are more common than most people think hehehe, thank for the advice!

 

[Trdat]

Let me describe my experience. I chose analogue active crossover for the main reason that I didn't want another Digital to Analogue conversion in the pathway or for the DAC in the digital crossover to be used instead of the amp that I bought for that purpose. I think there is way to bypass the internal DAC of D/DSP's with AES/EBU on the more expensive models. And yes, most of the descent ones are apparently transparent but perhaps some of the others can let us know about their experiences with D/DSP. In saying that I will upgrade to a D/DSP probably a Chinese option but apparently the JSL DS model uses a Sharc processor and according to a previous post they are pretty reliable. Why am I upgrading? So I can tune my sub directly and on tap.

Taking a step back, I use a Marchand XM66 crossover(variable crossover), its meant to be high end and unfortunately it did add some noise a slight hum to my disappointment and I had to send it back from overseas which cost me an arm and a leg. Upon its return there was absolutely no noise in the pathway and it works like a dream to crossover my 2 12'' inch subs. I use Audiolense to correct time alignment and to give me that flat frequency response but lets not forget my room is treated with over 30 traps. The only thing I can say that could be a problem is the damping factor by adding the crossover but this is all circumstantial and have no evidence to support this theory.

If you go with an active crossover you need something to correct timing issues so you must go for a software option of a DSP package, Audiolense or Accurate plenty out there. If you choose digital DSP then the experts on the forum can guide us to what is affordable and noise free and has enough processing power for sub duties or even digital crossover duties for that matter(which is my ultimate goal). There are analogue crossovers that have delay as an option but high end ones are expensive I think JL audio has product and its 3k.

Ill be honest, even without Audiolense correction music from youtube or even without the convolusion in JRiver there is no lag with the sub woofer and considering there is no delay option on the XM66 it is impressive. I am presuming the 4th order crossover switches the phase to time align the lower frequencies with the mains. With the convolusion on the bass is tighter and you can feel al tighter sound-stage and significantly better bass.

You must have a crossover for sub duties it is a must, and I can never do without a sub. Which option you use, active crossover you need a software DSP, D/DSP seperate or on an amp is all possible but you just need to consider what works for you.

 

[CosmicJazz]

Nice, thanks for share your experience...

I'm wondering if the possibility to align the voice coils manually, in order to adjust the phase will not bring ay benefit at all? Nothing?

 

[gene_stl]

It is very unlikely you will be able to hear the alignment of voice coils. Stop worrying about aligning voice coils. It also would be difficult mechanically to do so and would make a baffle that looked ridiculous and had an even more ridiculous dispersion pattern. You are NOT the first person to try this. VC alignment is not important.

Also remember you are just starting out. If you tri amp with three Fostex drivers , even with "merely" one 12 inch woofer, your sound is going to be better than 99.9 % of the stereo systems in the world.

Before you will be able to appreciate the differences of room correction and time alignment you have to get used to what the system and your program material sounds like in the first place. If you build the system you are talking about you will love it. Even without VC alignment , and dsp time alignment. You can always add those later. Nothing we are talking about here would prevent that.

A three way with a subwoofer(actually a four way) is a grand thing, but even before you add the sub it is going to kick ass. Getting good performance in the bottom two octaves is expensive and can be tricky and many recordings don't have much down there anyway (at least in the bottom most one). Depending on what you listen to.

The same applies to room correction. A lot of people have tried some of these room correction schemes and don't care for them. They are not easy and really not for beginners. They are also completely and inherently digital, only made possible by DSP. And they actually are more complex than tri amping. This is another area where I would suggest you stop worrying about it and just build a system so that you can listen to music.

You are not building a cathedral , yet. Walk before you try to run. Very few people hit the mark on their first try.

 

[CosmicJazz]

Thanks Gene! yes, makes totally sense, step by step..

 

[CosmicJazz]

Hello guys, let me ask you.

When considering a vintage crossover, like the Fostex that I mentioned earlier, that was produced in early 90's, what I must check in order to know if the unit must be revised, change components and etc, in order to work with full potential? I'm talking about more or less when you buy a vintage power amp for example, that is mandatory recap the unit and etc, this also applies to crossovers units? I'm sure that are very different designs with different components, so I'm taking this one for example:

Let me know what you see here, this equipment for early 90's, in this condition, probably still working as factory specs? or due to the age, it's vital to change some components? if yes, what components? it's complicated? Need a very experienced technician?

Many thanks!

 

[gene_stl]

Using the crossover illustrated in you pictures, the only thing likely to need repair or replacement is the electrolytic filter capacitors (the little cans)

But you only do this if A) the cans have swell or ruptured, splurping electrolyte onto the circuit board or B) You have hooked the unit up to test equipment and determined that there is AC noise or signal crosstalk between channels that can be blamed on dried up filters caps. When they design gear the engineers know that electrolytics gradually dry up and over specify them a bit.

Replacing electrolytic caps is pretty easy. You should have a power solder sucker. You need to exercise caution to not damage circuit board traces.

I suspect that a large fraction of recapping done on the order of audiophiles is unnecessary. Audiophiles like to buy presents for their systems and on of the presents they buy, is rebuild and overhaul services. Kind of like buying flowers for your wife, or maybe paying for her to get plastic surgery.

The only way to check any of this is on the test bench. There are lots of non vintage active crossovers that would not need recapping. Vintage offers no adavantage. I notice eight op amps in the above pix. For a stereo unit that is not very many. Buy yourself a Behringer or a Drive Rack or a miniDSP.
Or buy three amps with built in DSP and you won't need a separate Crossover. (Crown's current slogan is "Installs Anywhere , Outperforms Everything!" Looks pretty close to true to me.)
The Fostex will NOT sound better. I know you are in love with it but I can show you a McClelland I have that looks just the same only more elaborate. It is essentially a Taiwanese no name. Same phenolic board, same op amps (OH NO! Chip op amps , lets' replace them all with discrete components oh my!!! Or do some OP AMP ROLLING)

Buying the Fostex would be a newb misteak. I sense it isn't what you want to hear. But you asked for advice. It will sound fine but the alternatives are better (the difference may be below audibility), more versatile and newer or brand new.

 

[CosmicJazz]

Many thanks for the infos and advice Gene.