Large studio monitor clone take two

[Amnes]

It's taken me about 9 months this time around from buying the first pair of drivers till completion. There ar no longer any loose ends when it comes to the loudspeakers themselves. I plan on upgrading the active crossover to 24db, and changing the Carver amp in favor of a Marantz SM17. I've already started making arrangements to build a second pair since I have a full second set of speakers again consisting of all the clone goodies + more: blue baffle, walnut, grill pegs, foilcals, grill emblems, lpad knobs, rockwool, sheepwool, aircore inductors, CC'ed xovers and there seems not to be anything more to add.

Many, many thanks to all of you wonderful people on this forum - I would still be dreaming if not your guidance. Some teaser pics of the finished stuff since light was bad:

[Mr. Widget]

Well done! They look great.


Widget

[Guido]

Again

O U T S T A N D I N G

[speakerdave]

Impressive indeed!

[1audiohack]

Very nice indeed friend.

All the best,
Barry.

[Amnes]

Thanks for the appreciation guys. It means alot from this crowd. Now I shall upload the promised pics to the forum so they don't get lost.











Tada!

[Earl K]

Wow, beautiful work !

[just4kinks]

They look original to me! Nice.

Did you chamfer the port openings?

[4313B]

Wonderful work!

[Amnes]

Did you chamfer the port openings?

Had to google the word - yes, they are chamfered. I was indeed aiming towards making an indistinguishable for the untrained eye reproduction. If you're only after the sound no reason to do that, but I'm also a sucker for the blue baffle, foilcals, grilles and what not. Hopefully this will also contribute when selling these as I imagine a frivolous interpretation would be less likely to catch the eye. Need to post these in the classifieds . Already made a payment for a second set of ebay seller rjtimmermann's repros so the games shall begin all over again. Nice.

[Amnes]

Managed to fire up the 24db diy crossover cut at 340Hz with 0.1% 10k vishay and 2.5% 33nf mkp 1837 (pcb designed and distributed by p.f.pawlikowski of audiostereo.pl) So far I found the left channel hi out to be flawed somehow thus I was not able to perform full stereo listening tests. I can only say it generally works. At this early stage of testing it I was astonished by the dead silence coming out of the right channel compression driver when no input was being provided. That must be a good sign. On the LF there still is a hum to be heard which means my Carver amp is on it's way out. Not on par with the rest of my system and hearing the transformer buzz from 12ft away must be the source of the hum. Not a high fidelity amp at all. It is fairly old and has a THX certification badge so I shouldn't have expcted too much.

Hopefully I'll figure out what have I messed up tomorrow and proper tests will prove the design superior to the 12db nakamichi crossover I've been using so far.



EDIT:

And done! I cleaned up the underside of the bad board even more thoroughly - problem solved. I have been performing listening tests for the last half hour and all I have to say is WOW! I knew the nak unit was stealing some clarity on the top end but I would never have suspected it of being such a piece of crap. Now the sound is back on par with the mids and highs of my 250Ti. I though that was some sort of a tradeoff from the horn/lens assembly plus driver spacement, but it appears the crossover quality was the source of the tradeoff. I'm pretty astonished and it will take me about a week to get fairly accustomed to the new sound. All that from 100$ worth of electrical engineering. I still have the option to upgrade the opamps to audiophile grade low THD kind and the total $ spent will still be over 50% less than what I've payed for the nak. I have been officialy converted to become a diy audio believer. The opportunities of free exchange of ideas over the internet have opened doors to infinite possibilities when the knowledge of people is being combined to an end result. Fuck patents. That shit is obsolete. Thank God most electronic circuit topologies have been around long enough.

[just4kinks]

Very nice! What opamps are you using? 5532's get a lot of crap, but according to Self and others they are pretty hard to beat. And Self makes the point that most recordings have passed through dozens of them before even reaching the cd.

I'm glad you like it. My previous xo was the m552, which is also 24db linkwitz Riley, and I noticed a big improvement anyways. I think the fixed value precision resistors and high quality polypropylene caps make the biggest difference. My next experiment is to eliminate the electrolytics. Also I have a handful of vintage film caps I want to try out in the filters.

What are you using for an enclosure?

[Amnes]

Opamps are NE5534. I might try some "audiophile" grade opamps + swap out the caps for 1% if I can find some for a reasonable price... I have a small aluminum box for the enclosure. Its steel backplate with RCA sockets can be seen in the picture. It's going to be crowded inside it although I'll be able to separate the PSU from the electronics with a metal plate. I can't afford a standard size enclosure since it would simply not fit on the gear shelf. The box sits firmly on the top amp behind the CD player so cables are short and everything looks tidy. BTW I plan on unifying all my signal cables with one kind of high quality and shortest possible length.

I've done some more listening and this simple crossover keeps impresing me. What an essential piece of equipment to compliment the speakers.

[Ian Mackenzie]

If you care to upgrate discrete might be the way to go.

The problem with the chips is they can generally not be biased sufficiently into class A without overheating.

You can try class A biasing with a pull down resister on the output from the negative rail just for grins just be careful of overall power dissipation.

Some of the best big hi end names used this trick to up the hifi Uber of their solid state offerings

Here is a ready made discrete pcb kit from a guy who previously worked for Mark Levisnon.

The actual circuit you buy with the kit. It is not unlike the buffers used in the Bryston and the DX1

Scroll down and there is a xover kit. I have bought the kit but not had time to put it into service on my diy 4345

http://www.ska-audio.com/

[bstleve]

I'm using LME49860 in my Yamaha D2040 crossover. They sound much much better than the former AOP (5532). There is no DC offset at their output, so you don't need any capacitor in the signal path.
I've bought mine on the bay.

Bertrand.