Aleph 5 for mid/treble and Aleph X for bass

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Hi guys,
Last few days, after reading a Rushmore broschure, I'm thinking about biamping my sistem with Aleph 5 on mid/treble and Aleph X on the bass. I already got an Aleph 5, Aleph P is on it's way, so now I have to build an active crossover and Aleph X. I'll have to do it on a tight budget!
Now sorry for my lack of knowledge, but I would like to ask you a little stupid question. Can I build an ~80W Aleph X circuit just for the bass? Can I make it just to play low frequencies, let's say below 150Hz? :confused: Is that possible, and if it is, is that going to be less expensive? I want to make it as small as possible, but to have a good dissipation. Maybe one day I'll build my own active speakers and just put all the amplifing stuff inside the box.
 
Can you build an 80W Aleph-X?
Yep.
Can you cross it over at 150 Hz?
Yep.
Is it going to be less expensive?
Less expensive than what? In general, biamped speakers are more expensive than passively crossed-over speakers.
Small?
Don't count on it.
Will it sound good?
You betcha!

Grey
 
Funny, I was thinking the same thing, Aleph5 above 150Hz, AlephX below.

However, because my bass speakers are rather inefficient (around 85db/w, sealed system with Lambda's SB12) I need something like a 100 watt.

Therfore I am also thinking if I don't better use a PWM (class D type) amp, e.g. something with an ICE module or a Crown K1.

Saves a lot of electricity, and some have very good bass control (and 250 watt easily).

However, will these 2 diferent amp worlds make a good combination??
 
Duck-Twacy said:


Therfore I am also thinking if I don't better use a PWM (class D type) amp, e.g. something with an ICE module or a Crown K1.

Saves a lot of electricity, and some have very good bass control (and 250 watt easily).

However, will these 2 diferent amp worlds make a good combination??

What is Crown K1? I thought about that also. More power, less heat dissipation, consuming less power. Do you have something particular in mind?
 
bbakota2000 said:


What is Crown K1? I thought about that also. More power, less heat dissipation, consuming less power. Do you have something particular in mind?
I don't know if I'm alowed to advertise Crown stuff in the Pass forum ;)

In the USA a 350watt@8 ohm K1 can be bought for around $1050. In europe prices vary around 2000 euro (cheapest I found is here). There is also a K2, bBut that one has just too much power for me.

The strong point of Crowns is their bass performance, eg check out this review

Because I'm planning to cross at 150 Hz I'm a bit worried if the difference in amps will be noticable in the sound. But than again, there are also different speaker units, so there is always some difference in sound. Still crossing below 100 Hz would be better I think.

Btw because its pro stuff you probably can rent it for a couple of days.

Other options would be Acoustic Reality or some other ICE power based amp. Or maybe LC-Audio?
 
I wonder what would be the minimum bias level for an Aleph type amp for the mid and tweeter sections and not compromise the sound. If the bias levels can be reduced you could maybe put more amps on the same heatsinks? HUMMM, I wonder what bias levels the Rushmores mid bass, mid and tweeters are set to?

BDP
 
The minimum bias levels will be determined by the impedance of the drivers you intend to use and the rails. In other words, how much wattage do you want?
But...
The more you lean out the bias on an Aleph circuit, the more it tends to sound "hi-fi" in the sense that it loses the richness that makes it useful in the first place.
You ought to be asking--not how little bias you can get away with--but how much.

Grey
 
The Rushmore brochure mentions that the upper registers are served by Aleph topologies of no more than about 20W output (for highly efficient speakers, true). So the bias needed for 20W seems to be "enough" for good sound. How much you need for your planned output depends on your speaker impedance. The bias sets your maximum output current before current limitation. For each impedance there is an optimum combination of rail voltage and bias. From Ohm's law you can calculate U=RI. Say, for an 8 Ohm speaker, U=8I. Take I as the bias current, say 2 A. That gives you U=16 Volts *after* the Mosfet voltage drop. If you assume 4 V drop, your rail should be 20V to make a consistent amp spec.
 
If you have fairly efficient speakers lets say 95 dB/watt and around 8 ohms then listening at the "first watt" levels would be pretty loud, at least for what I listen to, then the current requirement would only be about 1/3rd of an amp. Most listening would be below a watt. So if you were to bias the mid and highs for 1 to 1.5 amps would this be enough to not compromise the sound?

I have a couple mono block Alephs each running 6 amps total bias with +/- 33 volt rails and am considering splitting each mono block into two channels for bi-amping. I can half the output devices and half the bias and still keep the same heatsinks and chassis. The total dissapation would be the same but with twice the number of channels.

BDP
 
How will an X150 perform as a bass amp? I like the idea of owning a real Pass amp (over a Crown). Probably matches an Aleph5 better too.

Maybe I'm in the market for a nice secondhand X150. Do these amps have a universal power supply (I'm at 230V50 Hz here), or shoud I buy a EC model only?
 
One plus of the X range amps is that they don't consume as much juice as the Aleph/Aleph-X (and AX of course). X types are highly biased class AB, I understood

To have a 150 watt class A you probably would consume around 1 Kw all the time. The X150 does 200 watt at idle (and more if driven hard of course). 150 watt should be enough for my 85.5 db/w/m Lambda's SB12s I think.

Of course class A is better, but I doubt if I hear that when used below 150 Hz.
Still $4500 is a lot of cash (5900 euro over here), thats why I'm looking for a nice 2-3 year old one (still curious if there is a seperate model for 230V countries btw)
A 300 watt pwm amp consumes 0,0001 watt at idle and can be build for $1000, but doesn't look that good ;)
 
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