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I would like some opinions on this idea I have.
I use a fairly stout Class D Audio amp that puts out 300 watts 8 ohms and 600 watts 4 ohms.
I`d like to use it to power the woofers in the low section and add a tube amp to power up the Mid/Top section.
The Class D Audio has volume controls to help level match the two amps.
I really don`t listen all that loudly..so I`m thinking maybe a tube amp for the top end in the 45-70 Watt range ??
Any thoughts/suggestions ?
Thanks
Steve
Follow Ups:
What is the crossover frequency?
Too much is never enough
Still fiddling around with crossover point. Right now the subwoofer is set right about 80hz with the level set low.
Next experiment: Take the Class D out of the mix completely and use the Rogue Atlas with the high pass out from the sub amp.
Crossover point grossly indicates power needs.
If full band signal is 100% than the 50:50 point is around 350hz.
My sub LP is about 45hz while the HP to the mains maybe 55hz or so. Since filters are not brick-wall, the output falls at 24db/oct in one case and 12db/oct in the other. My goal is for the region between crossover points to SUM FLAT.
One way to check for bass 'fill' from the sub is to have someone SHUT IT OFF mid-play. the stage/image should change for the worse and the lowest notes simply disappear.
IMO? 80hz is to high but I don't know enough about your system or main speaker capabilities.
Too much is never enough
Sorry,I honestly don`t know what this means.."Crossover point grossly indicates power needs.
If full band signal is 100% than the 50:50 point is around 350hz."
Or this.."If full band signal is 100% than the 50:50 point is around 350hz"
I read a review somewhere of the Revel f52 speakers and I seem to recall him using a 80hz high pass filter and that it made for a nice improvement overall.
My power remark is mainly aimed at the biamp crowd.
Somebody uses a large SS amp on the bottom end and crosses over to a much lower powered Tube amp.
Let's just assume the gain is +-1db between amps or a means of adjusting gain is available.
If the crossover point is the mythical 350hz, then putting a 250watt SS amp with 50 tube watts, the tube amp will redline FAR earlier than the SS amp. Wasteful, IMO.
Balance of power in a biamp system is one consideration. I use a pair of identical stereo amps and cross at 600hz. Not ideal, but the low-pass to the mains helps restore the balance of power.
Too much is never enough
Keep in mind the F52's have the "contour" controls for highs & bass, this would be integrated into the crossover networks. So I wouldn't do anything to the internal crossover. What you are planning to do should work fine. My only concern would be how low the impedance might drop on the top end of the speaker and how tubes would do with that.
The F52s seem to love the more current you can feed them. I originally drove F52's with Conrad Johnson monoblocks but they really came to life with a Pass X250. I never played with biamping them. I'd be interested to see how the biamping works for you.
With the 470C doing the grunt work, it would seem that a good tube amp should be able keep up with a much lighter chore.
I looked around and I`m thinking the top is basically an M22 and there was a review here on the M22`s where he ran them with 25w Mini Mites with satisfying results though admitting that more power would probably work better.
So I`m still thinking 45-70 tube watts could do it.
A Rogue Atlas would do it no doubt, but a lower power (less expensive) Jolida, PrimaLuna, QuickSilver and the like may do it as well.
I can always have my buddy drag the Rogue ST 90 back over too :)
I am a big fan of the F52, I especially enjoyed the very low response and detail.
I think biamping them could be interesting, for nothing else a bit more control over the balance of high to low end. Sometimes I wished I could get more power to the bass without boosting the highs any more, which is odd considering how many bass drivers those things have.
I agree and using the 470C for the woofers I can dial up on the bass too.
I`m also cheating in a sense..I`m using a Revel Ultimate Sub 15 with a 900 watt amp that fills in the bottom.
It`s been 3 months and just recently added a Rogue Atlas Magnum to power the top end of the Revels.
For the bottom section of the Revels I have the SDS 470 amps volume controls set at about 3/4 open using a 80hz high pass from the subwoofer amp.
Still tweeking the subwoofer crossover but so far it sounds pretty nice.
Ignoring the gain issue for the moment, what is the proposed crossover frequency?
Since you are not a loud listener, what are you intending to GAIN from this experiment?
Any chance of going DSP? Remove the speaker crossovers and give them to goodwill.
Too much is never enough
But with two amps from the same company with the same gain and input z and sensitivity.
By having volume controls on the D you can compensate for differences but the volume on that amp will likely have to be changed with different system volume settings due to it having different gain and input z and sensitivity.
Then there is the sound issue. I'm not a fan of any class D I've heard. I don't know what you are planning to invest but maybe two of the same amp since you are not a loud listener would work.
Knowing what speakers you are driving would help. Also knowing your general sound preferences would be good.
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
I had a Rogue ST 90 with KT120`s set up with the F52`s and I absolutely loved the sound. On a whim I sold it thinking I would look for another tube amp but with more power.
Meanwhile I bought the Class D Audio 470C to hold me over and it`s been shocking just how good it sounds ! It`s hefty @ 22 lbs and that`s decent weight for a class d amp.
It does some things better and some, not so much.
I think/hope the right tube amp will cover the "not so much" part and the 470C can do what it seems to do well..supply the needed power for the woofers.
It makes sense that Revel spent a good effort to design the crossovers to work as deigned for these speakers.
They don`t mention a degrading of sound when horizontal biamping. They simply state that at least one of the amps has to be adjustable.
So I`ll now look to see what all is needed as far as component compatibility and all that, plus connectors and what ever else.
So a 40-70 watt Tube amp or a set of smallish tube mono blocks in the same range should hold up the top end right ?
Thanks for all the reply's..Much appreciated !!
Steve
I would think. I looked up the speakers but there were no specs on sensitivity. Good luck!
ET
"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936
would be more advantageous to get 1 good stereo amp and biwire.
I would use the passive crossovers for biamping. Crossovers in well designed speakers do more than just act as crossovers. They equalize small problems in the driver responses and these corrections are specific to each speaker design. An electronic crossover is generic and isn't designed to do this compensation in many cases. If you're lucky and the electronic crossover is adjustable for crossover point and slope you may be OK but you would have to test it first.
This doesn't mean electronic crossovers don't work. They do very well but they must be designed for each speaker just like a good passive crossover to do the same compensations.
Some of those complexities are dependent on the variable impedance of the drivers and are eliminated when going to a line-level crossover. The speaker impedance becomes irrelevant as the amplifier presents a constant impedance to the crossover.
Other advantages include 1) protecting the tweeter from clipping as it is isolated from the power draw of the woofer; 2) There is better bass control as the DCR (power loss) from the LP inductors is eliminated 3) The efffective delivery of watts to the drivers is quadrupled not doubled - that is two 100 WPC stereo amps act like a 400 WPC amp not a 200; 4) Finally, separating the signals before amplification reduces IM resulting in a cleaner and more resolved sound.
All this is achieved at a cost -- proper line-level biamping requires a lot of thought and attention so that the crossover closely simulates the OEM XO with regards to order, frequency and slope.
I married the perfect woman. The downside is everything that goes wrong is my fault.
Edits: 09/15/16
I agree with all your points. I am an advocate of active crossovers. But what I said still stands. Modern crossover compensate for driver problems and a generic active crossover may not work. Plus most of us would be tuning the crossover by ear and then you will get what sounds good but that may not be maximum fidelity. Otherwise passive crossovers would be easy to design. We'd just look up simple formulas in books.
Note I did say to try it and the best way is to do one active and try to make it 'sound' like the other speaker. It may or may not work.
Thanks guy`s. I`m not all up to speed on bi-amping trust me.
I thought though, that horizontal bi-amping was actually passive, being you take the straps off and use the two amps once you adjust the output levels and you leave the crossovers in the speakers alone ??
I do have an electronic X-over but it`s for sale in the classifieds here. I`m not too sure I want to go that route.
Using the speaker level crossover to biamp is not exactly a crossover in the pure sense. What it actually is, is two parallel filters (one HP and one LP) with no crossing over of the signal. In other words the HP filter dumps the low frequency signal to ground and the LP filter does the same with the high frequency whereas in a line-level crossover the "rejected" low frequency signal from the HP is directed to the woofer and vv for the high frequency signal from the LP.
Just for clarification, a speaker-level crossover is passive but a line-level crossover can be either active (ALLXO) or passive (PLLXO). The term passive crossover is often taken to mean speaker-level but that is not correct.
While there is nothing wrong with using the speaker-level crossover, it does not have the same performance and advantage of an line-level crossover. It is much simpler to implement. Rod Elliott has a nice article which explains the niceties and complexities of line-level biamping.
I married the perfect woman. The downside is everything that goes wrong is my fault.
an off the shelf active crossover would NOT be an improvement.
Yes / no?
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
I used a Marchand XM-44 and designed the filters myself for my Magnepan IIIa. A much cheaper approach would be to DIY the crossover using modules and ps from Rod Elliott. A third approach might be to use a miniDSP which has a lot of flexibility and doesn't require a knowledge of filter design.
I married the perfect woman. The downside is everything that goes wrong is my fault.
If it is much above 200Hz the tonal character of the bass amp may become audible and not match.Taking the 87.5db spec at face value, you would need 22.5db of power (> 150 watts pc) in a single stereo power amp to play loud orchestral music at concert levels. 40 - 80 watts RMS pc AB1 from a PP valve amp, given the typical 3db headroom of valve amps, should be plenty. A triode option would be good for smaller scale intimate works.
It would be a good idea to find out the range of gain (x to y volts in for output of 1 watt OR in dB ) on the bass amp.
Then check that the prospective valve amp's gains are within that range.
If you have AC for Summer you'll be fine, if not, consider a good sounding AB1 SS 80wpc amp for the hot months.
In the longer term a bespoke or adjustable xover that matches the slopes and Eq of the original passive circuit just might sound a teeny bit better, and give you a bit more loudness, though I doubt that would be significant.
I'd also recommend that you consider picking up a stereo 1/3rd octave equalizer to Eq the bass range to 200hz. That's assuming you haven't gone all-digital, when a room-DSP box becomes an option. eg. Dspeaker or Mini-DSP. I believe Mini-Dsp's range of boxes are flexible re crossover slopes and frequency.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Edits: 09/13/16 09/13/16
I hope you are considering an active crossover -- that would allow you to match the gains of the amplifiers. IMO, using the speaker level passive crossover is not worth it but others will disagree. OTOH using an active crossover is more complicated than it might seem - you need to decide slopes, orders and frequency of the filters. How much power you need on the top end sort of depends on the crossover frequency (at 300 hz it's about 50-50). As a rule I would use an amplifier for the top end that is capable of driving your speakers as a "mono-amp". Do you really need all that power (Magnepans just love it) - what is the sensitivity of your speakers? Regardless consideration of the voicing of your amplifiers is also a factor and biamping with two amps that you just have lying around is not a great idea. Personallly, I prefer vertical biamping with identical amps.
I married the perfect woman. The downside is everything that goes wrong is my fault.
IMO, as long as the crossover from the woofers is not to high, the solid state amp powering the bass is not nearly as critical as the tubes on top. The solid state amp needs to be at least twice as powerful as the tube amp, which you have covered. I use some older Harman Kardons under ARC VT50. So 45 over 100. To me it's the best of both worlds. My woofer to mid cross at 125hz.
bigshow
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