[bladesmith]

There are those over on the AVS forum who say that all amps sound the same.   You might as well go with the cheapest amp because the only important spec. is the power output. Pro amps like the iNuke are the favorite over there. Many also claim that tubes just add distortion so SS is the only way to go.

X2....

[Roger A. Modjeski]

I can't provide a specific link without devoting more time than I want. However, at least in this thread, http://www.avsforum.com/forum/155-diy-speakers-subs/1291022-hey-guys-we-need-little-rallying-here.html, there have been many posts that imply that amps aren't that important as long as they have enough power. Definitely, the very inexpensive iNuke is a favorite there. $150 gets you 2 x 300 Watts into 4 Ohms. http://www.behringer.com/EN/Products/NU1000.aspx.

I'm not saying I agree with this, to my thinking an extreme position, but it's a highly prevalent opinion among those in the home theater crowd. They tend to think that the speaker is by far the most important component.

Thanks that's all I needed to get started. This is a forum I have never seen. I will study it.

I have played with some of these inexpensive high power amps and some of them put our their rated power and some just plain lie. I had a Pyramid amp that was supposed to be 200 watts and it as 40. http://www.sonicelectronix.com/item_30279_Pyramid-ZPA150.html?utm_source=google&utm_medium=cpc&utm_campaign=sc&scpid=2&scid=scsho3605219&gclid=Cj0KEQjwlv6dBRDC7rGfrvidmJgBEiQAjd3hMD9t8hd_h7HC7iAuD2XSf-SaxUNL6M3ivr

But that is not the main problem. These high power amps have very little tolerance for difficult loads due to the aggressive short circuit (over current) protection. They cant drive electrostatics to any appreciable level before the limiter cut in. They do fine with resistive loads.

The iNuke amp is a class D. I have no idea how it is protected.

[Freo-1]

I can't provide a specific link without devoting more time than I want. However, at least in this thread, http://www.avsforum.com/forum/155-diy-speakers-subs/1291022-hey-guys-we-need-little-rallying-here.html, there have been many posts that imply that amps aren't that important as long as they have enough power. Definitely, the very inexpensive iNuke is a favorite there. $150 gets you 2 x 300 Watts into 4 Ohms. http://www.behringer.com/EN/Products/NU1000.aspx.

I'm not saying I agree with this, to my thinking an extreme position, but it's a highly prevalent opinion among those in the home theater crowd. They tend to think that the speaker is by far the most important component.

I tend to agree that the speakers by far are the most important component in getting good sound.  Having said that, its not possible to get the best sound from the speakers without quality electronics supplying the signal.  The AVS guys are more concerned about movies than music, so to some extent, their agenda is not the same as folks who are after the highest quality stereo reproduction.  I don't think they are as obsessive about music as we are. 


Case in point:  For a vacation home, I've got a basic setup that uses a Yamaha RX-A1030 receiver with a pair of T + A Criteron 160 floor standing speakers.  They are all Dynaudio drivers (with 2 10" LF drivers in each cabinet).  The speakers are so good, they sound great with the basic Yamaha.  Can hardly wait to hook up the good electronics consistently to them.

 
 

[bdp24]

I can't provide a specific link without devoting more time than I want. However, at least in this thread, http://www.avsforum.com/forum/155-diy-speakers-subs/1291022-hey-guys-we-need-little-rallying-here.html, there have been many posts that imply that amps aren't that important as long as they have enough power. Definitely, the very inexpensive iNuke is a favorite there. $150 gets you 2 x 300 Watts into 4 Ohms. http://www.behringer.com/EN/Products/NU1000.aspx.

I'm not saying I agree with this, to my thinking an extreme position, but it's a highly prevalent opinion among those in the home theater crowd. They tend to think that the speaker is by far the most important component.

The DIY Subwoofer guys use Pro Sound Amps (Crown etc.). For subs they're fine (assuming high damping factor), except for the fan noise.

[Roger A. Modjeski]

The DIY Subwoofer guys use Pro Sound Amps (Crown etc.). For subs they're fine (assuming high damping factor), except for the fan noise.

I agree that some these pro sound amps are great for subs and I recommend them in my Resistance Loaded Sub system for ESLs. There are some that do not have fans which is preferable. Note that these new small, high powered amps with fans (now that a fan is cheaper than a big heatsink the manufacturers have moved more toward fans) do not always put out their stated power and may have severly sensitive load line limiting causing clipping into a difficult load. A woofer generates a lot of back EMF which will cause amps with fewer output transistors to limit.

As an alternative I suggest buying a good quality used amp on eBay. There are many. I have several available for my system.

[bdp24]

Older, fairly high-powered SS amps from the 80's, like JGH's favorite the Eagle 2A by Electron Kinetics, can be had for $300-400 on AudioGon and eBay. Whatever you do, do NOT buy, or even hook-up to your subs, the Adcom 555. They're notorious for their leaky power supply capacitors, and will fry a driver in an instant. If not today, tomorrow.

[Roger A. Modjeski]

Of course any older amp should be checked out by a technician or the new owner on a speaker of low value.

One can very safely use a 1 or 2 amp fast blow fuse in series with the woofer to test the amp and I advise you leave it there. Although the fuse has a little resistance it will not harm the sound of your sub. If you play the woofer loud you might need a larger fuse. The power rating of the woofer will help you figure the maximum fuse by the formula

Watts= fuse current squared x speaker impedance. Here are a few examples for an eight ohm speaker.

Use a 1 amp fuse for a 10 watt speaker, 2 amps for 32 watts, 3 amps for 76 watts. Work your way up and blow a few to see where you need to be.   Since most subs are high powered 1 amp is a bit low to start. The fuse will actually blow at about 1.5 times its rating, which actually doubles the power but the time is short.

Fusing for amplifier faults is actually easier than using a fuse to limit signal power. Most amps put out DC when they fail and that will blow the fuse quickly. I usually end up with a 2 or 3 amp fast fuse. You can get a nice in-line fuse holder with heavy wires from most electronic or auto parts stores.

[poseidonsvoice]

I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.

by Abraham Maslow, The Psychology of Science, 1966.

http://positive-feedback.com/Issue74/duelund.htm



Best,
Anand.

[Roger A. Modjeski]

I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.

by Abraham Maslow, The Psychology of Science, 1966.

http://positive-feedback.com/Issue74/duelund.htm



Best,
Anand.

That PF article is really long and a lot of money and effort went into it $ 18,621 to be exact. The autoformers were $6,219. What the actual improvement is, who knows.

It is interesting that they compared the weight of the original autoformer to the Duelund which is much heavier due to the casting compound and case. What is important is what is in inside. Some measurements of the two transformers would be interesting.

In reading this article I learned something new, I had not known that silver will migrate over an insulator over time and degrade that insulator.
Here is the my post concerning that and what I learned from the Bell Telephone article.  http://www.audiocircle.com/index.php?topic=127381.0

[BobRex]

Considering the dollar value of that "upgrade", I would think the next step would be to compare the change to fully active bi-amp with an external xover.  That should be a plug and play exchange with just minor tweaking.

[Freo-1]

Considering the dollar value of that "upgrade", I would think the next step would be to compare the change to fully active bi-amp with an external xover.  That should be a plug and play exchange with just minor tweaking.

That just opens up another entire can of worms with the parts, design, etc. of the active crossover.  Once one dives into these rabbit holes, it gets hard to climb out of them. 

[steve f]

Wow. I just breezed through the article. I can't imagine why anyone would want to spend that kind of money to build a passive crossover. Two quality amps like Music Reference and an active crossover just makes a lot more sense. I don't know why audiophiles are so hung up on passive crossovers.

[Roger A. Modjeski]

Wow. I just breezed through the article. I can't imagine why anyone would want to spend that kind of money to build a passive crossover. Two quality amps like Music Reference and an active crossover just makes a lot more sense. I don't know why audiophiles are so hung up on passive crossovers.

Considering the dollar value of that "upgrade", I would think the next step would be to compare the change to fully active bi-amp with an external xover.  That should be a plug and play exchange with just minor tweaking.

I agree that an active crossover is a far better solution and requires less money and less effort, though a different kind of effort. My take on it is that people dont really understand active crossovers. The main concern I hear is that they fear the electronics in the crossover will add coloration, that they will not be as good as a neutral line amp. What people don't understand is that the electronics in a crossover are more neutral than a line amp as they usually have no gain at all.

It is well established that speaker crossover components have serious drawbacks by their nature. Coils have resistance which reduces woofer damping. If they are wound on iron they have hysteresis and saturation problems. Capacitors have dialectical absorption and ESR problems. All these problems are eliminated by the electronic crossover.

A further advantage of electronic crossovers is that they have level controls for the individual drivers which allow one to tune the system to his room and preferences. I trim my levels at will just a bit for different recordings. If something is too bright I turn down the tweeter. If I want more bass I turn up the woofer. Inter-modulation distortion is almost eliminated and one can now choose amplifiers for their characteristics to please the individual drivers. The woofer amp should have high damping and more power than the tweeter amp which can now be something single ended if that is desired. Single ended amps have certain virtues in the mid range and highs. They are generally not preferable for woofers.

I think the main reason is laziness. It is easier to replace a few crossover parts than buy and wire up a bi-amp system. However in the case of the PF article over $18,000 and considerable effort was expended for a less than perfect solution.

I would love to hear from others who modify speaker crossovers what keeps them from going to active crossovers.

[Freo-1]

I agree that an active crossover is a far better solution and requires less money and less effort, though a different kind of effort. My take on it is that people dont really understand active crossovers. The main concern I hear is that they fear the electronics in the crossover will add coloration, that they will not be as good as a neutral line amp. What people don't understand is that the electronics in a crossover are more neutral than a line amp as they usually have no gain at all.

It is well established that speaker crossover components have serious drawbacks by their nature. Coils have resistance which reduces woofer damping. If they are wound on iron they have hysteresis and saturation problems. Capacitors have dialectical absorption and ESR problems. All these problems are eliminated by the electronic crossover.

A further advantage of electronic crossovers is that they have level controls for the individual drivers which allow one to tune the system to his room and preferences. I trim my levels at will just a bit for different recordings. If something is too bright I turn down the tweeter. If I want more bass I turn up the woofer. Inter-modulation distortion is almost eliminated and one can now choose amplifiers for their characteristics to please the individual drivers. The woofer amp should have high damping and more power than the tweeter amp which can now be something single ended if that is desired. Single ended amps have certain virtues in the mid range and highs. They are generally not preferable for woofers.

I think the main reason is laziness. It is easier to replace a few crossover parts than buy and wire up a bi-amp system. However in the case of the PF article over $18,000 and considerable effort was expended for a less than perfect solution.

I would love to hear from others who modify speaker crossovers what keeps them from going to active crossovers.

OK.  In theory, active crossovers make a lot of sense.  Speakers such as those by Meridian and ATC have active powered models, and are widely recognized as some of the best sounding speakers available.  So, it makes me wonder:  Why is it speaker companies do not offer a active crossover to go with their speakers?

I am interested in making a quality two way crossover (at 80 Hz) for my tube setup.  I would then have a lower powered tube amp  made for the HF to go with the ATC SCM 19 speakers. There really isn't many available on the commercial market.  The only one I can think of that is reasonably priced is this one:

http://www.hsuresearch.com/products/high-end-crossover.html

Guess I should look for a good schematic for a tube crossover.

[Roger A. Modjeski]

OK.  In theory, active crossovers make a lot of sense.  Speakers such as those by Meridian and ATC have active powered models, and are widely recognized as some of the best sounding speakers available.  So, it makes me wonder:  Why is it speaker companies do not offer a active crossover to go with their speakers?

I am interested in making a quality two way crossover (at 80 Hz) for my tube setup.  I would then have a lower powered tube amp  made for the HF to go with the ATC SCM 19 speakers. There really isn't many available on the commercial market.  The only one I can think of that is reasonably priced is this one:

http://www.hsuresearch.com/products/high-end-crossover.html

Guess I should look for a good schematic for a tube crossover.

I have the RM-3 which is a good SS crossover capable of slopes up to 24 dB/octave, any alignment as the crossover components are on plug in cards. The high pass is all discrete push pull transistor and the low pass is IC.

If you are sold on tube crossovers you should check our Marchand Electronics. His crossover is modular and you can buy just the boards or kits for less. It is a good unit, I have worked on one.

For simple 6 dB per octave you can just put caps and resistors at the input jacks of the amps.

A tube active crossover is easy to build. You just need a few cathode followers and appropriate filter components.

As to your question: Speaker companies are not electronics companies. They really don't know much about active circuits, they live in a passive world. If one approached me I would be happy to make what they needed.

[Freo-1]

I have the RM-3 which is a good SS crossover capable of slopes up to 24 dB/octave, any alignment as the crossover components are on plug in cards. The high pass is all discrete push pull transistor and the low pass is IC.

If you are sold on tube crossovers you should check our Marchand Electronics. His crossover is modular and you can buy just the boards or kits for less. It is a good unit, I have worked on one.

For simple 6 dB per octave you can just put caps and resistors at the input jacks of the amps.

A tube active crossover is easy to build. You just need a few cathode followers and appropriate filter components.

As to your question: Speaker companies are not electronics companies. They really don't know much about active circuits, they live in a passive world. If one approached me I would be happy to make what they needed.

I'm not necessarily hard over on a tube vs SS crossover.  Wouldn't a second order crossover be in order for the SCM-19?

[bdp24]

A 1st order passive high-pass filter with active low-pass for subs has long been the way for Electrostatic owners, especially Quads. With a lot of subs now being active, it's easier than ever. It's bi-amping without having to buy an amp or separate x/o, if the ones built into the sub are good enough. For a steeper high-pass, the Marchand tube x/o's have a great reputation amongst finicky enthusiasts. Harvey Rosenberg used them with his Quads and horns. When I was using a Bedini 25/25 on my Quads I had Tom at Brooks Berdan's place install a cap and resistor (I think it was both, though it may have been only a resistor) filter on the backside of it's RCA input jacks, and ran subs with the active section of the Dahlquist bi-amping unit (John didn't call it a cross-over)---2nd order to the sub amp. That route avoided the extra cable and connections going through the Dahlquist to the Bedini would necessitate. Tom just took the amp's input impedance and the x/o frequency I requested, and calculated the values required. It's great to have a tech in the neighborhood! I'm about to do the same with my RM200, but without the Dahlquist in the system (the current subs are powered and have their own adjustable---2nd or 4th order, 40Hz to 240Hz---low-pass filters).

[BobRex]

For simple 6 dB per octave you can just put caps and resistors at the input jacks of the amps.

I think I know the answer to this, but just for confirmation:

Suppose I wanted to put the highpass (6 dB) on one of the outputs of the pre-amp, instead of inside the amp.  Do I need to consider the characteristics of the interconnect as part of the calculation, or is that just noise.  Also, since the pre outputs are just a parallel circuit, will the change in the aggregate load at low freqs affect the other output?

[Roger A. Modjeski]

I think I know the answer to this, but just for confirmation:

Suppose I wanted to put the highpass (6 dB) on one of the outputs of the pre-amp, instead of inside the amp.  Do I need to consider the characteristics of the interconnect as part of the calculation, or is that just noise.  Also, since the pre outputs are just a parallel circuit, will the change in the aggregate load at low freqs affect the other output?

The high pass is the easiest to do. Cable capacitance is no more an issue with or without the high pass. You need to know the output impedance of your preamp and input input impedance of your power amp, the latter will probably dominate when they are added together.

Here is a good calculator I have recommended before. http://www.sengpielaudio.com/calculator-XLC.htm

I worked out a typical example for you. If the preamp output impedance is 1 Kohm and the power amp input is 47 K add those together and put 48K into the calculator. For 80 Hz crossover the series cap is 0.414 uF. As you can see the output impedance doesn't matter much adding 1 k to 47 K wont change the answer appreciably. If you don't know the output impedance of your preamp you can likely ignore it as it should be small compared to the input impedance of your power amp.

The cap value is not critical. The closest standard value it .039 and even .047 would not be bad as the roll-off is so gradual. The main advantage of doing this is to relieve the amp and main speaker from having to play deep bass which robs power and causes intermodulation. I would go for the smaller cap and help the speaker/amp more. Using a 0.033 uF would be a good choice.

The cap goes in series with the hot lead either at the output of the preamp or input of the power amp. The power amp input is preferred.

This is a really simple but very valuable thing to do. A big improvement for little cost and effort. There are many things like this we can do to improve our systems without buying into some pricey, doubtful modification that we read about in the magazines.

[bdp24]

I just looked, and found my receipt for the caps Tom installed in my amp, one on each channels input jack; 00.0033 MFD +/-10% 200V Siderealkap (matched). With an input impedance of 50K Ohms, does the frequency end up around 80-100Hz? I think that's what I was shooting for.