5W Zen for biamp tweeter

[GRollins]

Pixie,
Yeah, there's absolutely no question that film caps are expensive...
Just for fun, and since you've already got them, leave them on for a month or so, then take them off and see if you notice them by their absence. And, yes, even .1 uF can help. I've known people who claimed that even a .01 uF was a big difference (across 20,000 uF electrolytics), although I prefer to shoot for at least 1 uF, myself.
Anyway, back to the original question--Kanga, can you give some specifics on your speakers (drivers and effiencies, if known) and what your listening tastes are (type of music and how loud you listen)? We can speculate and toss generalities about until the cows come home, but if there are facts to be had, this will be more productive.

Grey

[Kanga]

Thanks for all the responses so far.

I calculated the 5W based on the table in the ESP article at http://www.sound.au.com/bi-amp.htm (which contains plenty of good info on biamping). The table says frequencies above 3000 Hz represent about 15% of the sound energy in music. Calculating 15/85 x 60W / 2 (to cater for tweeter efficiency) gave me the 5W. What I forgot about is that my speaker (mini monitors) runs out of puff around 50 Hz, and so there’s another 1 ½ octaves that the woofer isn’t reproducing, which messes up the calculations a bit (all those boom booms and organ pedal notes I’ve been missing).
Anyway, 10W is probably a better power to choose as it will allow for power upgrade in the bass if I need to later on.

I was hoping not to use a capacitor to protect the tweeter, so the suggestions about using relays are comforting. Are there power on/off protective relays that you can buy or would I have to build one that would ground the outputs somehow?

For the active crossovers I’m planning to be lazy and to buy a couple of Marchand electronics XM-9 crossovers kits, which have plenty of nice features (eg variable damping and easy to change XO frequency) as well as 24dB/octave slope. Thanks for the offers on the circuits anyway.

Grey, the speakers I’m using are the original series 1 Acoustic Energy AE1s. The overall efficiency is about 87 dB/W/m, and nominal impedence is 8 ohms. The tweeters currently have a 5W 6.8 ohm resistor in the crossover (they’re not biamped yet) so I figure that this makes them almost 3dB more efficient than the woofer.
My musical tastes are mainly classical and jazz, but Pink Floyd and few other rockers sometimes get to perform too. Listening levels are probably medium – I have a pretty large but live room and reasonably uncomplaining neighbours.
The AE1s are capable of fantastic transparency and imaging when they are set up right, and so the tweeter amp needs to hopefully enhance this, plus maybe warming up the sound a little (sounds like maybe I’m after a valve amp, but I’d rather steer clear of these).

Any more suggestions for tweeter nirvana welcome!

Kanga

[GRollins]

Kanga,
A few more questions:
1) Is it safe to assume that you've been living with these same speakers and the 60W amp for a while? To rephrase--do you already have a gut feeling that the 60W will play what you want to play, and play it (more or less) loud enough?
2) You said in your original post "a small Zen," and later mentioned 5W output. Is this a Son of Zen that you're planning, or an original/revised Zen? The original Zen was, I think, 10W, which would be a welcome increase in power.
3) Would you consider a rolloff filter at, say, 30 or 40Hz to conserve power for the upper bass and midrange?
4) Is there any frequency tailoring going on in the passive crossover that you're aware of? Notch filters and such *can* be implemented at the line level, but you need to plan ahead.

Grey

[Kanga]

Grey

The 60W seems to be plenty enough at the moment, but the AE1s are supposed to work better with a bit more power. The current amp (Cyrus III) has an external fully regulated 500 VA power supply which provides plenty of current.

I was thinking an original Zen, but I'm not really in a position where I'm able to judge whether Son of Zen might be better. I don't have balanced gear up stream. That one of the problems (or maybe benefits) of DIY - you can't go into the store and have a listen to which you prefer, instead there's endless tweaking and trying different things. I suppose I need to rely on people like you who have tried both and may be in a position to recommend.

A rolloff filter at 30-40 Hz is a possibility, but the speaker naturally rolls of from maybe around 70-80 Hz, and so much below 50 Hz there's not much happening anyway. I have been thinking that I may add a sub later on, and possibly put in another active filter to start rolling off from say 100 Hz. I'm not all that keen on rolling off if I don't have to because of the adverse phase changes that result.

I pulled out the crossovers to see what they were doing now, and the only non-crossover type work that they are doing now is partial impedence correction using a Zobel network on the woofer. I plan to delete this when going active because I've been told that this is only there to stop the passive crossover getting confused. There's no other filtering happening, just a 3rd order filter on the tweeter and 4th order on the woofer.

I'm going to be incommunicado for a few days, so thanks for the help so far and hope you don't think I'm rude for not answering for a bit.

Kanga

[GRollins]

Kanga,
There ain't no speaker made that wouldn't benefit from having 'a little more power.' Me...I'm a firm believer in having plenty on hand. Or, as my mother used to say, "Better to have it and not need it, than need it and not have it."
If you feel that 5W will do you, then the original/revised Zen (with 10W) should do a good job. I personally would have reservations about that small an amp, but as we were saying above, your circumstances may be such that you'll be cutting flips over the sound quality.
Use a little feedback if you like, to extend the frequency response. (It will also improve the damping factor--not as important with tweeters as with woofers, but not to be ignored, either. No one has, to my knowledge, made a massless tweeter, although the plasma ones come close.)
Your reservations regarding low pass filter phase shifts are noted. That's why I phrased it as a question. As far as subs go--I'm a believer. Take it from me, though, it's a slippery slope. First, there's the little mono sub. Then you discover that you've been lied to and that stereo subs really do sound better, so then you buy another. Then you want either deeper bass than the little subs will do or higher SPLs or, worse yet, both. *Sigh.* There's no end to it.
Oh yeah, I forgot to mention--yes, time delay relays are commercially available in a wide range of time constants. It's been a bit since I've used them, but Potter Brumfeld used to have a nice line of sealed delay relays. I used to use them when people would want me to build a tidy slow-start circuit for their amps. I assume they are still available. You can, of course, roll your own.

Grey

[tiefbassuebertr]

Originally Posted by Kanga

I'm just about to enter the world of biamping, and I'm wondering about the suitability of a small Zen amp for powering the tweeter. The woofer will be powered by my current commercial 60W amp, and with a crossover frequency of about 3200 Hz and an efficiency of the tweeter about 3dB higher than for the woofer, I figure about a 5W amp will do the tweeter.

Has anyone tried a small Zen for powering a tweeter, or have any other ideas for a suitable amp?

Another consideration is avoiding power-on thumps, which will destroy the tweeter pronto. I am planning to put a protective capacitor in series with the tweeter with a crossover frequency around the 1000 Hz mark.

Any experiences with biamping would also be of interest. Am I wasting my time?

Basiclly this is a very interesting approach. But you will need additional to your passive crossover network an active crossover. The royal way is to work without additional OP AMP's. Because the ZEN isn't a source follower, you cannot use the good known sallen-key topology. Instead this you must use the so called MFB topology (MFB = multiple feed back)
In this case I have opened a thread with some schematics:
ZEN include active crossover without additional OP AMP for ultimate sounding PHL1230

[moe29]

"I remember... doing the Time Warp...!!!"