Actively wondering.
Posted by: Richard F on 07 April 2001
I would one day very much like to go active with Naim gear. As I have three way speakers I am seeking advice about the path I would have to take. Am I being stupid by wondering if I can mix the power amps. I.e, maybe 250 for the bass & 2x140's for the mid & treble? 
I have also wondered how easy it would be to configure the Naxo 3-6 for my speakers. Would it be better to stick with Naim speakers?
Any idea's or warnings welcomed 
If you mix amps in an active system, it's recommended that you use the better amp on the tweeters.
However, many will claim than a pair of passive 135s will beat an active system comprised of 140s, 250s, etc. For example, the new 500 purportedly sounds better than a six-pack of 135s driven by a SNAXO 3-6 with a Super-Cap.
As far as using non-Naim speakers goes, the problem is the crossover frequency. You may have to get the SNAXO adjusted to crossover at the same frequency as your speaker's internal crossover. Or you might be lucky and it already matches. The next issue is getting them hooked up. Considering most speakers have internal crossovers, you have to get inside the speaker to unattach the outside binding posts from the crossover, then reattach the wires directly to the speaker driers.
It's not impossible, though.
-=> Mike Hanson <=-
quote:
There has been some discussion that 135 sound different from 250 and in some cases are worse to certain speakers.
Aha, I've just done the reverse! I have recently swapped out my 135s for a 250 and some cash for my flat fund. My 135s were 1987, and my "new" 250 is still old style, but dates from 1989. Both the 250 and the 135s were recapped by Naim within the last two years. My experience is obviously based entirely on my vintage flat earth system, which when viewed in the context of current Naim system hierarchy is very preamp light being based on a 72 upgraded 32.5. I am sure the result would be very different if I had a more recent wide bandwidth pre such as a 52.
Ok so what's different then? Well, the 250 is quite a bit fatter and more meaty sounding in my system, it lacks a little of the dynamic punch of the 135s, and possibly resolves a little less acoustic space / reverb effects around instruments. I listen at quite low levels, so running out of steam is something I have not experienced with either amp.
The strange thing for me is that in the context of my system I actually prefer the 250, the extra weight suits my Kans nicely, as does the slightly warmer and less forward balance. This downgrade has proved totally painless, and whacked a useful 750 quid in the flat fund.
My 135s went to a very good home, and are driving IBLs on the end of a CDS2 / 52. I want to hear that system at some point. The 250 has got the later LED light, so expect Naim stocks to crash soon as I will no longer be buying an endless supply of bloody bulbs.
Tony.
I acquired a cheap NAC42XO at the weekend, I intend to service the preamp and XO, add suitable PSU's and use it in an experimental 2nd active system. The crossover frequency seems to be about 2.5kHz for the NAC42 at present.
I remember JV saying crossover point wasn't too critical in the past, but it would make sense to emulate the internal XO if possible.
Andy.
Andrew L. Weekes
alweekes@audiophile.com
I remember reading that the correct kan frequency was 3kHz, but also, like you recall a Naim statement that the actual frequency wasn't that critical, the slope of the bands was more critical. I picked up an SBL naxo and had read that, because SBLs used the same tweeter as kans it was also fine for kans. After much huffing & puffing pulling out the crossovers my kans seem to work fine with the SBL naxo. The plot for the naxo also indicates a crossover freq. of 3k.
Was it you that got the NAC42XO that was on Loot? I spotted it at the end of last week and thought it looked seriosly interesting - even though I don't need it I was sorely tempted. I was thinking that paired with say a couple of 110s or 160s it would be a very cheap solution for driving something tricky like Saras.
Phil
It's in perfect working order, but could do with a service. Naim amps of this vintage used lower tolerance carbon film resistors in place of the current metal film ones currrently used. It could do with a recap as well I reckon.
I have the technology and I shall rebuild it. I originally intended to throw the pre-amp section and add a PSU into the box (a sort of mini-IXO), but initially I'll try it as is, for experimentation purposes within a second system. I don't think a 42 of this age is going to compete with my 112.
Now to scour Loot for some really cheap 110's!
I'm going to use it with some Goodmans Maxim 3's that are already modded for active use, and that I know the crossover characteristics of.
I shall mod the NAC42XO to emulate these crossover points first, before venturing into Kan-land.
Andy.
Andrew L. Weekes
alweekes@audiophile.com
The active/passive argument is not as compelling as it used to be. I can understand your desire to go active especially in view of the spare 140 lying around. Linn make a big play on mixing and matching their amplifiers to build up an active system and deliberately designed their equipment with equal gain to facilitate this. I listened to Naim and Linn and decided that my route would be Naim since I liked the dynamics (referred to as PRaT) which was something that the very competent Linn could not pull off. So I went for the 250 (which I personally like compared to the 135's) and focussed on the source first. Then came the Nautilus 804's and the realisation that I could get more from these and the 52/CDS-II so I looked at possibilities. Now I am one of the lucky (or unlucky!) people that has heard the 500. This is one hell of an amp which really takes power and speed into a new paradigm! My game plan, then, was to stick with the 804's with a 250 and then upgrade to a 500 sometime soon. I would keep the 250 and buy a second to go active with the NBL. Someone here made a point that the better amp should be on the high frequency unit and the lesser amps on the midrange and bass - that is good advice. The trouble is not in the gain but in the timing. I asked Naim to tell me what they though about my cunning plan and they told me that the 500's timing would be an issue when compared to the 250. I'm not at all familiar with the 140 and 180 but I would imagine that similar issues exist. The gain is the same and hence comparitive magnitude of volumes is not an issue but what of the timing? My decision? I bought a second very new 250 for a very good price and bi-amped the 804. The PRaT is stunning and keeps getting better as the amps converge in their timing and the speakers get run in. The 500 will have to wait until I can get it past the wife without her noticing! Good luck with your quest.
I'm sure I recall the same thing being advertised on Loot a few months ago (for a higher price!) - did the seller indicate that he'd had it up for sale for a while?
Phil
quote:
Andrew, just idly thinking about that interesting NAC42XO - how is it powered? Does it need a snaps/hicap or can it be run from one of the power amps? What if you plug 2 power amps in - does it tap the power from each (nah, can't imagine this is a sensible option), if the better amp is supposed to work on the tweeters presumably it taps into the bass power amp.
It actually takes the single 24V rail from each PA and uses them both.
It's configured 1 amp per speaker, not 1 per frequency. One of the 24V rails feeds the preamp section, the other the Active XO section.
Obvious areas for improvement are PSU's, the pre could have .5 mods to split L+R psu's and there's three muting relays inside, 1 per XO channel + 1 for the pre. These run from the existing supplies, and I'm sure a dedicated supply just to feed these would be beneficial, even though they are likely to be fairly malign once in a steady state.
My long term intention is to seperate the XO and build a dedicated supply (L+R 24V, relays) it may be beneficial to split the supplies to the various gain stages within the XO as well, subject to the board layout alowing this easily.
I'll model the XO section in SPICE so that I can easily change and test different configurations to move crossover points and levels to suit different speakers.
quote:
I'm sure I recall the same thing being advertised on Loot a few months ago (for a higher price!) - did the seller indicate that he'd had it up for sale for a while?
He didn't mention it - he'd had it for a couple of years, but hadn't used it - his intention was to go active with Kans or similar, but never got round to it. The price was aimed at a quick sale!
It's very dated, although even the volume / balance pots seem quiet quiet after all these years. The reality is it would benefit, I'm sure, froma complete rebuild, which I'll probably do since it's a fairly simple job requiring only my time and some relatively inexpensive components. I've ordered new DIN sockets (in the twist lock style) as they're all very tarnished looking, and I may change the volume pot for the ALPS type used on later equipment - this will be the most expensive part, the rest of the components I have access to.
At least I can hack it around as an educational exercise, without worrying too much, something I'd never do to the main system!
Andy.
Andrew L. Weekes
alweekes@audiophile.com
quote:
even though they are likely to be fairly malign once in a steady state
er, Andrew, did you really mean that or should it be 'fairly benign'??? 
cheers, Martin
Andy.
Andrew L. Weekes
alweekes@audiophile.com
quote:
However, many will claim than a pair of passive 135s will beat an active system comprised of 140s, 250s, etc. For example, the new 500 purportedly sounds better than a six-pack of 135s driven by a SNAXO 3-6 with a Super-Cap.
i am not one of those making that claim. for my ears there was absolutely no contest between 2x250 active and 2x135 passive with 52/supercap and cdsii. to me, the active system had more of what i like in a naim system -- involvement and emotion, bags of that.
however, i wait to actually hear a passive 1x500 system in comparison with an active system with 135's -- since i have heard that 500 wins hands down... hmmm... here is me confused at a higher level
apologies this thread isnt really about active vs passive as such ...
enjoy...
ken
- GregB
Insert Witty Signature Line Here
enjoy...
ken
quote:
How much is a 'really cheap 110'?
To be honest I haven't decided yet! I'm sure the amount I'm willing to pay will directly relate to the spare funds I have available for my tinkering and the condition of the amps.
Others on this forum will give you a better idea of the price ranges they sell for, I'm unusually patient and am prepared to wait / haggle until I find some at the right price.
I guess somewhere around £100 for an old one would be in order, maybe less if one finds an uninformed seller.
In the meantime I'll cobble together what bits I can for experimentation (e.g. an old Nait or two I have kicking around the house) which will allow me to integrate the crossover design, before spending any real money.
Andy.
Andrew L. Weekes
alweekes@audiophile.com