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RE: Tweeter difference problem with 3.3Rs and more

Posted by Davy (A) on August 30, 2010 at 16:24:11

In Reply to: RE: Tweeter difference problem with 3.3Rs and more posted by Satie on August 30, 2010 at 10:07:31:

HI Satie,
Thanks for the advice, - you are right on all counts.

I tried the PLLXO out today with the new caps, - a small improvement for sure so it was worth the small expense over the polyester caps so I'm glad I got them.
Just to see I tried my Arcaida tube preamp with the PLLXO/active setup, -= terrible!, - heavy, bad sound, - totally wrong, - I guess you need that extra resistor with the tube preamp!! So I used the flexible Quad 99 most of the time but also at one point tried the Moth passive as the preamp, - which actually sounded pretty good. Not quite got the dynamics of the Quad but the treble was purer, more natural, and less grainy sounding. So I will use that as well as the Quad when playing CDs in the future.

I had better luck today playing around, - I am still finding it hard to get 3rd order LP Butterworth on the Behringer to work well with the PLLXO. 90 and 180 degree normal phase sound too sucked out whereas 0 is too heavy. On reverse phase 0 is too sucked out but 90 and 180 have some potential
But yes it seems I still am finding 2nd order Bessel or Butterworth (but Bessel in particular) blends better with the PLLXO. For the LP, Normal phase 0 is OK, 90 and 180 are too sucked out. and on Reverse phase 180 seems the only one that sounds good. 90 and 0 are not good. For this 2nd order setup I've settled on 180 degree reverse phase for the time being and am playing around with volume levels/crossover freq and trying Bessel and Butterworth, and a sort of in between trying to use the EQ.
3rd order Butterworth really needs work, - I will do what you say and try 15 degree increments in between the two best points I have found so far, which are 90 and 180 reverse phase.

The Bessel 2nd order LP setup seems to get rid of the problem I have with my room (that I had with the 2.7s) of falling FR with frequency. My only complaint is there seems a bit of lack of bass extension and I still don't quite have the mids right.

I know now this will take a lot of tuning. What I think is actually quite likely is that I will also buy the stock crossover boxes (despite the expense), - not necessarily to use them permanently, but to use them as a reference to fine tune my biamping setup with and to try to get my biamping setup sounding as close as possible to to passive drive with one speaker amp in terms of coherency. Or possibly like you suggest I could build my own stock crossover boxes with slightly better components using the same values. But I need to work out the cost difference etc. I also need to double check with Magnepan the crossover schematic of the 3.3Rs, - not that I'm saying the one on the MUG site is wrong, - just want to double check.

The coherence of the sound is very important to me, probably the most important thing, - I am not sure if its going to be possible to beat a single power amp driving the speakers at passive speaker level in terms of coherence. It really will be a challenge to get a biamping setup to sound as good in this regard. I can see the advantages of driving your speakers actively, - each amp is only dealing with one frequency range so you hence get better definition etc and better dynamics too, more headroom etc. The thing is though I am in a small room so I am no doubt not really taking advantage of some of the big advantages of active drive. I will see how it pans out in the end but if single amp drive ends up giving me a more coherent result I might just stick with that, - but I intend to give both types of operation a full chance and see how I end up. Or maybe use both and swap from time to time.

The problem with the stock Behringer driving both sections is two fold - the sound quality is too compromised for me, - you lose too much refinement and I find it it pretty obvious. But worse there is the hiss issue which is really totally unacceptable for me. Possibly in my case as I am in a smaller room and sit closer to the speaker than most people do the hiss is more noticeable? And the L-pads (from my tests so far) are no good at all as they change the sound characteristics a lot (from my first tests anyway) and make blending of the bass setting with the PLLXO even more difficult. There might well be something wrong with the values I've calculated, - it really does change the sound a lot and is not usable at all, - will get the values later and post.

I don't actually think my Behringer is faulty or anything (hiss wise), - I've read on the internet of many people having this hiss problem with them and many of them tried other DCXs too in case theirs were faulty, but to no avail.

To improve the coherence of active or passive line level baimping I think the first thing I will have to do aim to minimise difference between the two sections. There are other things I can do.
One of them is I think I really need to be using the same model power amp for each section to minimise differences there than could cause discrepancies in blending. It would still not be EXACTLY the same power amp driving each section and there still might also be a slight sound difference in two amps of the same model, but the idea is to minimise the differences, - using two of the same model power amps is bound to have better matching than using two entirely different power amps.
The next thing I think need to do it to is possibly avoid this part active/Part PLLXO approach for the time being (apart from for testing) and use an all active line level approach or all PLLXO approach. From listening to the HP PLLXO and its equivalent on the Behrginer through headphones in isolation, I can hear the huge difference in tone and sound quality in general between them. I know I am using the Behringer only for the bass but I am sure this will add to the blending problem.
Obviously going full active using the Behringer for both sections (though the matching is better) is not an option for me due to the hiss and compromised sound quality. So I think I possibly need to aim for going all PLLXO, - maybe starting with a 2nd order LP for the bass if I can find a setup that seems to work (it might take some tuning of course and fiddling changing values), and I need some sort of attenuator device will not degrade the sound heavily like the L-pads I tried. I am sure the blending will be better (than my current part active/part PLLXO approach) with an all PLLXO if I can get to the right LP PLLXO setup. Though obviously I still need keep the Behringer as a tool for testing out new regimes like you say.

So yeah I might buy the stock passive crossover boxes too and see how that compares to my efforts and use it as a guide as well. I know if I choose to stick with passive drive/single speaker amp I will loose the ability to fine tune the bass to my particular room/positioning with this and that could be a huge disadvantage as its a set thing with the external boxes. But I really want to see mainly how much difference in coherence there is between the two methods of drive, and if the one amp approach is indeed ahead in this department, then I can use it as a guide to help fine tune my biamping setup. On option if I make my own crossover boxes would be to put optional biamping connections in (with a swtich), - could be useful if I could alter the volume of one amp to fine tune the sound to my room. I woudl be interested to see too how passive speaker level biamping compares to single amp passive drive in terms of coherency.

As for the Technics decks, - Well I'm now quite happy I got both of them , - as that broken 1700 mk2 on Ebay Germany I saw (that didn't even spin, so no guarantee of getting it to work) just went for £120 with shipping (more if I had bit on it) so I got my working one last night very cheap for £85 all in. And I should be able to repair the 1600Mk2s auto belt with a rubber band and get that working OK.
Its good having these two decks as I will have two headshells too, - good for easy cartridge changes. I know it will not be an option if I go for your foil damping and arm cable scheme though! (which I am likely to try on one deck at least). So yes I'm pretty happy about this, - two of these decks for around £260, and despite one being a a lot cheaper than the other, - I think that's not bad considering they are both MK2s and they seem quite hard to find (in the UK at least). Just got to get cartridges now. I am an MC guy really, - I used to like the cheap Ortofons (MC15, MC10), but the current range are unfortunately too pricey. I will go for a Denon DL103 or DL110 ), - both should work well with the medium.heavy Technics arm. The lack of top end can be a bit of a problem with the 103 at times in my experience, despite its other very goo qualities such as great body and tone etc.
One of my favouite cartridges is the another Denon, - the DL304. Its highly musical yet also very transparent and has a great extended top end. But its too high complaince for the Technics arm. It works well in the Rega arms though, so I might stick a Rega or upgrade Rega arm on one of the decks and use a DL304. The Denons had their first price hikes a couple of years ago for the first time in about 25 years, but they are still pretty good value even so. The DL103 went up the least, - only about £15 or so. There is a UK company called the Expert sylus company that sell upgraded DL103s, - they put their own sapphire cantilever and paratrace diamond tip on the DL103 for a more extended top end. Got to try one of these one day.Price is about £280 I think. Could be a killer cartridge for the money if it addresses the top end problem of the 103 yet retains the other great aspects of the 103 sound.
Look forward to getting these decks, - will let you know how I get on.

Just read the last of your message, - measurements?, - errr NO!!! how do I do that? microphone, test tones and computer I guess? Not sure where to start really, - is it difficult? what setup for this do you recommended for a novice like me?!

All the best,
Colin

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