Multi-channel amps for active speakers?

[tcpip]

I am building a 3-way speaker system with active crossovers, and I need a multi-channel amp -- six channels to be precise.

In a more generic context, the advent of MiniDSP (and earlier products like the Behringer digital crossover) allows us to build sophisticated and high quality active crossovers with relatively little time and effort. This makes multi-way speakers easier to design and build, and all the advantages of active crossovers which we had read about now have come within reach. This means that more of us may go looking for multi-channel power amps. I was wondering what one can do to tackle this need.

I found the following:

• good home theatre amps and receivers which support 6.1 and 7.1 channel surround sound
• proper multi-channel power amps

In the home theatre arena, one needs to look for slightly older models. Newer models very rarely have a multi-channel analog input cluster. My Yamaha RX-V800 is a 5.1 channel amp, and has five power amp channels and a six-channel analog input option. A Marantz SR4300, SR5200, or SR7200 is a 6.1 channel receiver. It has seven channels of analog input and six channels of power amplifier. It's perfect for my Darbari. As a bonus, it (like all HT receivers) even has a multi-channel volume control with a remote. And since it does not have HDMI support, no one wants such models now and the prices in the used market have dropped.

In the proper multi-channel power amp space, there are many models from Rotel and Parasound. The Rotel models include their RMB series (RMB 1048, 1066, etc) and Parasound has the HCA 1206, HCA 806, and others. One nicety these amplifiers omit is a multi-channel volume control.

I am aware that there is a general belief among audiophiles that HT amps are of poorer quality. I wonder how true this is, if I bypass all the DSP circuitry and simply use the receiver as a multi-channel analog power amp? Well, I have arranged to get a Marantz SR5200, so I will soon find out.

What do you think about options for multi-channel amplification for active crossover driven speakers?

 

[Santy]

I am building a 3-way speaker system with active crossovers, and I need a multi-channel amp -- six channels to be precise.

I found the following:

• good home theatre amps and receivers which support 6.1 and 7.1 channel surround sound
• proper multi-channel power amps

But how will you use a multi channel power amp alone with your speaker system? You either need an AVR or pre-processor and power amp.

I think FM @kapvin is using DIY 5.2 speakers with active XOs driven by Emotiva prepro + power amp.

 

[Santy]

Also, if I have understood it correctly, for a 3-way active XO speaker system, you would need 15 channel power amp.
5+5+5 for the LF/MF/HF drivers in each speaker considering you will add an active sub.
For a 2-way active XO system, there would be a need for 10 channel power amp.
I am not sure if I am confused?

 

[tiger0691]

It is easy to use Receivers since it has multi channels.
But the sound quality is not at all good enough. (flat sound and lack of musical nuance)

Why don't you go for 2 ways system with HiFI amp.

1. Channel Divider(active crossover) - Small D-Class amp or Tube amp for twitter/mid range(passive network)
2. Channel Divider(active crossover) - Very good and powerful solid amp for bass.

I don't recommend AV Receiver amp.

 

[kanwar]

Also, if I have understood it correctly, for a 3-way active XO speaker system, you would need 15 channel power amp.
5+5+5 for the LF/MF/HF drivers in each speaker considering you will add an active sub.
For a 2-way active XO system, there would be a need for 10 channel power amp.
I am not sure if I am confused?

A Stereo 3-way Active needs total Six channels.

 

[Santy]

A Stereo 3-way Active needs total Six channels.

Sorry I had been thinking that he wants to build a HT system...

 

[goldyrathore]

I am doing something similar for my active Synergy horn project. Once my prototype is ready I plan to go for minidsp 2x8 for its immense flexibility in choosing arbitrary xover points/slope and its EQ capability. For amps, I have MyRef kits powered by SMPS.

Also if EQ is not needed you could consider an analogue active xover at
3-Way Active Crossover-DIY Kit.

Even in modern AVRs which dont have 5.1 analogue in, the amp section is separate from the processing part. You may be able to isolate the analogue inputs in the unit.

The pro audio stuff that you ve mentioned (Behringer ultradrive, DBX stagdrive etc) is too costly in a home situation.

 

[tcpip]

I am doing something similar for my active Synergy horn project. Once my prototype is ready I plan to go for minidsp 2x8 for its immense flexibility in choosing arbitrary xover points/slope and its EQ capability. For amps, I have MyRef kits powered by SMPS.

Fantastic.

You will also need a DIGI-FP and VolFP, right? A raw MiniDSP 2x8 is hard to use in a system by itself. What will you do for chassis?

Also if EQ is not needed you could consider an analogue active xover at 3-Way Active Crossover-DIY Kit.

Hard to use. Can't imagine a crossover where you're lucky enough to completely do without any eq. In my case, I will need heavy eq to take care of the cone breakup region of my Dayton RS midrange. The kit is extremely inexpensive, though, and may be good for beginner experimentation. For instance, the documentation talks of LR4, but not about arbitrary Q. In the real world, it's hard to build a good crossover with just LR or Bessel or any of those other "official" curves -- you need to model the measured SPL curve with arbitrary slopes, Q and Fc, and then arrive at the R and C values you need. Someone who can understand all this will probably become impatient with this kit.

For active speaker design, I find this kit hard to use. However, what I am attracted to is their LM3886 kits -- extremely attractively priced and easy to use. You can even put them on the rear wall of the speaker enclosures, and will probably get excellent performance.

The pro audio stuff that you ve mentioned (Behringer ultradrive, DBX stagdrive etc) is too costly in a home situation.

The Ultradrive costs $299 on Amazon. The MiniDSP 2x8 alone is $299. Add the digiFP and VolFP, and it becomes about $370. Add a chassis, and you spend some more. How is the Ultradrive more expensive? And it even has a 32-bit SHARC DSP, which the more expensive MiniDSP 2x8 does not have.

Even the Driverack seems to be less expensive than a full MiniDSP stack -- assuming that I have got the model right.

I decided to go for the MiniDSP 4x10HD. Saved me some headache in integration, and gives me the flexibility to program arbitrary IIR filters from a modelling tool.

 

[tcpip]

It is easy to use Receivers since it has multi channels.
But the sound quality is not at all good enough. (flat sound and lack of musical nuance)

I am unable to understand why the poweramps in a Marantz receiver will be any worse than even an entry-level Marantz stereo amp. What is the commercial motivation for the manufacturer to do this? How much difference in costs will there be? As it is, there will be opportunities for cost-cutting because of the single shared transformer and power supply... what else will they do to cut costs and drop quality?

I'll try some receivers and see if I can see any quality issues. The Yamaha receiver I am using right now does not seem any worse than any entry-level stereo amp.

In one area, I expect almost any multi-channel amp (including receivers and boutique power amps) will be worse than typical stereo amps will be crosstalk. I will have to live with that, till I build my own power amps.

 

[goldyrathore]

Fantastic.

You will also need a DIGI-FP and VolFP, right? A raw MiniDSP 2x8 is hard to use in a system by itself. What will you do for chassis?

I only plan to use the analogue in/out and so DIGI-FP is not needed. diyaudiocart also has good Acrylic faced enclosures. Also my unit will be out of sight so enclosure is not a priority.

 

[goldyrathore]

Hard to use. Can't imagine a crossover where you're lucky enough to completely do without any eq. In my case, I will need heavy eq to take care of the cone breakup region of my Dayton RS midrange. The kit is extremely inexpensive, though, and may be good for beginner experimentation. For instance, the documentation talks of LR4, but not about arbitrary Q. In the real world, it's hard to build a good crossover with just LR or Bessel or any of those other "official" curves -- you need to model the measured SPL curve with arbitrary slopes, Q and Fc, and then arrive at the R and C values you need. Someone who can understand all this will probably become impatient with this kit.

I agree. However if you do all the measurement and tweak cycle using a PC and 5.1 sound card then you can use the final xover values with the diyaudiocart xover. Of course, it cannot do EQ. This is what I am doing as well. I already have a XonarD2X for the job.

 

[goldyrathore]

The Ultradrive costs $299 on Amazon. The MiniDSP 2x8 alone is $299. Add the digiFP and VolFP, and it becomes about $370. Add a chassis, and you spend some more. How is the Ultradrive more expensive? And it even has a 32-bit SHARC DSP, which the more expensive MiniDSP 2x8 does not have.

Even the Driverack seems to be less expensive than a full MiniDSP stack -- assuming that I have got the model right.

I decided to go for the MiniDSP 4x10HD. Saved me some headache in integration, and gives me the flexibility to program arbitrary IIR filters from a modelling tool.

I compared the two a bit differently. Both the pro audio units mentioned here are available locally and are above 33K. The minidsp unit is smaller and can be carried by someone coming from US and so I assumed 299$ as the only cost. Plus the minidsp has 4 pair of outputs out of which I plan to use 1 pair for stereo subs. On the other hand the Behringer is 3 way stereo so an analogue xover is still needed for the sub.

 

[goldyrathore]

I am unable to understand why the poweramps in a Marantz receiver will be any worse than even an entry-level Marantz stereo amp. What is the commercial motivation for the manufacturer to do this? How much difference in costs will there be? As it is, there will be opportunities for cost-cutting because of the single shared transformer and power supply... what else will they do to cut costs and drop quality?

The electronics are more or less saturated in terms of sonic fidelity. Two good amps sound very much alike, of course this is assuming that amps being considered are of good designs. There is no point in comparing a good design with a mediocre one. The sonic differences in amps are very trivial and exaggerated, IMHO. Further improvements just result in diminishing returns. The weakest link in the audio chain still is the speaker. The difference in amps is easily shadowed by the speakers.

So, I would suggest to try the amps in receivers, if you leave the bass out then the common trafo should not be an issue. Also is the crosstsalk perceivable? A simple experiment can reveal it. Feed input in one channel and listen to the others.

 

[tcpip]

I compared the two a bit differently. Both the pro audio units mentioned here are available locally and are above 33K. The minidsp unit is smaller and can be carried by someone coming from US and so I assumed 299$ as the only cost. Plus the minidsp has 4 pair of outputs out of which I plan to use 1 pair for stereo subs. On the other hand the Behringer is 3 way stereo so an analogue xover is still needed for the sub.

I can see what you mean about the fourth output. If you need it, then it is a mandatory feature.

About size -- the MiniDSP 4x10HD is a full-size 1U rack-mount box. The Behringer is a 2U, I think. Both can be brought in as accompanied luggage by someone travelling to India. (My MiniDSP was brought in that way, from Singapore. The Customs guys casually asked what it is, and the person said "Oh, a cheap Chinese amplifier for a friend." The Customs guy waved him through.)

Of course, you're getting the raw board, which will be much smaller.

 

[tcpip]

The electronics are more or less saturated in terms of sonic fidelity. Two good amps sound very much alike, of course this is assuming that amps being considered are of good designs. There is no point in comparing a good design with a mediocre one. The sonic differences in amps are very trivial and exaggerated, IMHO. Further improvements just result in diminishing returns. The weakest link in the audio chain still is the speaker. The difference in amps is easily shadowed by the speakers.

It's a real relief for me to read your opinions, after seeing so much of subjective opinions from the audiophile community everywhere who claim to hear things none of which will stand up to blind testing .

So, I would suggest to try the amps in receivers, if you leave the bass out then the common trafo should not be an issue. Also is the crosstsalk perceivable? A simple experiment can reveal it. Feed input in one channel and listen to the others.

Yes, I'm going with the receiver for now, and will worry about the crosstalk. Eventually, my aim is to build my own pair of 4-channel amps anyway, which should have a bit less crosstalk.

 

[omishra]

I feel you should look at 41hz.com for few class T amp kits. There are many amp kits with range of power outputs. Properly implemented class T or class D could be better efficient and robust multichannel solution.

 

[tcpip]

I feel you should look at 41hz.com for few class T amp kits. There are many amp kits with range of power outputs. Properly implemented class T or class D could be better efficient and robust multichannel solution.

Will definitely look, thanks. The space and power savings of Class D definitely make them super-attractive for multi-channel chassis, just like Class A is super-unattractive for such designs. But a lot of the work in Class D till now has been to attract the PA sound reinforcement crowd, not the discerning home audio customer. Distortion of 0.5% is often considered perfectly okay for this class of Class D designers. Need to avoid those designs. The Hypex amp modules are of course excellent for my kind of requirements, but they're quite expensive -- I'd rather go with an LM3886 or LME498xx family of designs, just to fit a tighter budget.

 

[tcpip]

On the 41Hz site, this one seems to have fantastic paper specs. Will read in more detail.

The Chinese designer Cristy has some Class D amps on his Website but I found it so difficult to communicate with him (his erratic email habits) that I gave up after more than a month of trying.

 

[kapvin]

I just saw this thread.

1. I am running a 3 way active mains using a UPA-7 multichannel amp. 6 channels are used for WMTTMW(123-567) and the centre channel (4) is used for the passive centre channel. another stereo amp for the surrounds. and yet another for the subs.

2. I own both the minidsp 4x10 as well as behringer stack (DEQ2496 and DCX2496). with the same filters applied, both sound a more than a bit different. they shouldn't.. but the only time I compared them, they did.

if you ever use a DCX with Non pro amps, you will have to work with the gain structure.. 0dBFS into the digital inputs will give you 10v at the output. Great for car audio, though. I used the MVC multichannel volume control to tame the DCX

the Minidsp is far more flexible and useful if you have unruly speakers (read metal drivers). but for well behaved speakers the DCX is much simpler to setup) (and allows multiple configurations) (and if you do some of the well documented DCX mods - it is supposed to sound really good too)

@TCPIP - i would look for some of the 2nd hand old school AVR tanks. (prefererably from the pre-hdmi days - they'll be cheaper) (though you really do not need 200w each for the tweeters). of course class d kits are also a nice options.



best wishes

 

[tcpip]

@kapvin,

Impressive surround system you have there. Active mains L-R, passive xo for the rest, if I understood you right. Good combination of active and passive.

About the idea of the old AVR, that's exactly what I've done. I've gotten myself a Marantz SR-5200 6.1-channel receiver which I intend to use for my Darbari. I am currently using the amp on a trial basis with my old speakers, and they do not appear to be one bit worse than most of the entry-level 2-channel stereo amps I have heard. (No blind testing here, just overall impressions.) You're absolutely right about the pre-HDMI era of these amps. On eBay UK, they are really affordable. They work with 220V and have multi-channel volume controls to boot.