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Old 13th July 2009, 02:30 PM   #1
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Default Parallel/Series/Active or PCXO for OB?

Coaching required please?

I've looked at passive crossovers, parallel and the more difficult series (see Elliot and Graddon),
both costly for woofer inductors, (except for 2 woofers in parallel, thanks Pano!)

OR, .. active xo's. very expensive to setup. but a relativley low cost Behringer might be ok
for a 15" woofer and a Full Range in a 2way?

Then, I would still need a good/cheap preamp and 2 power amps with XLR inputs and cables.
Any ideas please?

A basic Rotel preamp begins at $800? whoa. Then I need 2 monoblocks as well.
This is becoming a very expensive hobby. haha Cheap Pre/Power Amp suggestions most welcome.

OR, a dedicated PCXO, it seems a SoundBlaster soundcard has an XO on board. True?
Other options are Convolver, Allocator etc. Would a good soundcard be the cheapest option?

I've probably made many mistakes here, but my intent is to ask which option would be the best
and most cost effective solution , ie 'bang-for-buck' for a beginner. Thanks.
Please excuse my dumb questions, I'm still trying to figure it all out!
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Old 13th July 2009, 04:09 PM   #2
pos is offline pos  Europe
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I would say a dcx2496 could be your best bet
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Old 13th July 2009, 05:36 PM   #3
Pano is offline Pano  United States
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Hey Grant - I don't know how much the inductors cost down there, but they are spendy here in the US. Copper prices are high. You might be looking at $20US each for the bass.

But really, it's still the cheapest way to go. Get a good iron core coil like the Erse for your 15". That will be the major outlay for the x-over. You won't have to spend much for the mid section. Cap, coil resistor.

I always get cold feet when I total up the cost of passive x-over parts, but the crossover is just as important as drivers. It can make or break a speaker.

The nice thing about a passive x-over is - connect it and forget it! No worrying with multi amps, levels, PC buggy software, etc. And the results can be very good indeed.
Easy to connect any amp or source you want, too.

I have the DCX2496, but must admit that passive x-overs have many advantages.
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Old 13th July 2009, 11:23 PM   #4
ChrisA is offline ChrisA  United States
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Default Re: Parallel/Series/Active or PCXO for OB?

Quote:
A basic Rotel preamp begins at $800? whoa. Then I need 2 monoblocks as well.
This is becoming a very expensive hobby. haha Cheap Pre/Power Amp suggestions most welcome.
Have you thought about building one. This is after all a "DIY Audio" forum. The trick to building a low cost, high quality amp is finding the parts at a good price. The best way to do that is salvage. Seriously. Keep an eye out for broken gear with good parts inside.

Based on the "junk" I've collected, my next stereo project is going to be a small amp based on 6L6 tubes. The last thing I bought was a broken Hammond organ amp. Tons of good parts inside. Very high quality 50 year old transformers.
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Old 14th July 2009, 03:46 AM   #5
Francec is offline Francec  Australia
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Quote:
OR, .. active xo's. very expensive to setup.
Not really when you consider the benefits and the cost of large inductors. I think it is well worth it.
Quote:
but a relativley low cost Behringer might be ok for a 15" woofer and a Full Range in a 2way?
Interesting combination. Not something that I find attractive but who knows?
Quote:
Then, I would still need a good/cheap preamp and 2 power amps with XLR inputs and cables. Any ideas please?
Why XLR? Silicon Chip magazine did a pre-amp a couple of years ago which I have built for less than $250 including digitally controlled PGA2310. Having said that, I will add mini-XLR conecttors for balanced outputs.
Quote:
A basic Rotel preamp begins at $800? whoa.
Choke! Gasp! Why a Rotel? Something off eBay would do it. An integrated amp with a pre-amp output would be OK.
Quote:
I've probably made many mistakes here, but my intent is to ask which option would be the best and most cost effective solution , ie 'bang-for-buck' for a beginner. Thanks.
I've built active speakers using Rod Elliott boards and Peerless drivers. The drivers cost about $420 and the rest about $400. I'm happy (for the moment.)
My speakers are 8" 830868 with F3 around 45Hz, 5 1/4" 832873 and 1" tweeter. In my smallish environment, it sounds great. One caveat though; badly produced CDs sound as awful as they really are.

The benefits, as I see it for active for the beginner, are the choice of drivers is more open because interdependency ceases to be an issue. As long as the of drivers cover the spectrum you want, 24dB crossovers roll off faster than the drivers. Inductances and sensitivity issues are consigned to the rubbish bin.
PLUS, you get all of the benefits of active; dynamism, active damping, great bass.

Frank
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Old 14th July 2009, 01:54 PM   #6
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pos,

yes the DCX2496 looks good but $450AU ouch. CX3400 is cheaper but:
Modifying Behringer CX3400 crossover
its noisy?

Pano,
great stuff indeed, yeah I have to get this in perspective. I can import Erse from say Parts XPress etc.

.. ditto re connect and forget..that is a big advantage. Is your DCX2496 noisy?

I'm still kinda tempted to buy a CX3400 (if still available 2nd-hand) but some 'issues' about Behringer seem an annoyance for HiFi. That is trying to modify DJ/PA gear.

I've been offered 2 12inch high Qts drivers freebies from PeteMcK, thanks Pete!, so my OB might get started after all.

If they sound ok, I think I can buy 2 more for more bass 'grunt'. and maybe xo around 100-200 to a FR.

But which Full Range driver? I guess I'll try one 15" woofer per side first. Or go back to a 3way. Arrgh!

re: quote " but must admit that passive x-overs have many advantages." sure, but Rod Elliot at ESP has such compelling arguments for active. A good read as you know.

ChrisA,
great idea to build. I built a basic hifi integrated amp 20 years ago. It still works! Salvage is an even better idea. BRILLIANT! Never thought of that. This is just such an amazing forum. You re-incarnating old amps and PeteMcK is using drivers from the side of the road. Unbelievably inspiring.

Frank, gday!
wow, what a reply! spot on the money. thanks. I'm a Libran so I seem to swing between decisions.haha

OK, I can't afford a DCX2496, I can afford a CX3400, (when the car is fixed!) but like I said I have noise 'issues', interconnect cables, and I need a new pre and amps.

Silicon chip preamp sounds great I assume. Price is right. I could possibly build that, eyesight permitting! ( I'm an old bas**rd!) Why XLR? well isn't that a requirement? Excuse my ignorance!

What is quote" digitally controlled PGA2310 " no idea.
" An integrated amp with a pre-amp output would be OK". As 'Pauline' (haha) would say: please explain? Only quoting her for the statement, thats all.

Any help re Rod's projects applicable to my intended 2way with 15" and FR...most appreciated please.

re: quote: "The benefits, as I see it for active for the beginner..." sounds great to me! smooth SPL response is very important, no nasty breakup mode to counteract. Andy G taught me that!

thanks very much for your input, may I email? cheers, grant
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Old 14th July 2009, 02:04 PM   #7
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I guess I'll try one 15" woofer per side first.... oops 12 inch
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Old 14th July 2009, 03:00 PM   #8
Pano is offline Pano  United States
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The DCX is not noisy if you use it right. A lot of guys don't. (hint - gain structure) But stock it just does not sound good. Harsh and muddy at the same time - an odd and unpleasant combo. Modified it is very nice.

I was an active crossover snob for 25 years. But some of the very best rigs I've ever heard were passive. Done right it has many advantages, the first being practicality!

Doing a 12 or dual 12 + fullrange should not be hard. But don't get stuck on the idea of a low crossover point. My guess is you'll be up at 300Hz at least. Maybe even 600+. Don't do what you think is best - do what sounds best! Easy to say, but a hard lesson to learn.
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Old 14th July 2009, 09:47 PM   #9
Francec is offline Francec  Australia
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Quote:
thanks very much for your input, may I email? cheers, grant
Sure.
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Old 14th July 2009, 10:22 PM   #10
Theo404 is offline Theo404  United Kingdom
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Default Re: Parallel/Series/Active or PCXO for OB?

Quote:
Originally posted by grantnsw
OR, a dedicated PCXO, it seems a SoundBlaster soundcard has an XO on board. True?
Other options are Convolver, Allocator etc. Would a good soundcard be the cheapest option?

I've probably made many mistakes here, but my intent is to ask which option would be the best
and most cost effective solution , ie 'bang-for-buck' for a beginner. Thanks.
Please excuse my dumb questions, I'm still trying to figure it all out!
My humble opinion

Beginner bang for buck has to lie with this solution. If the idea of active crossovers even slightly interests you than you can experiment with it for nearly nothing! Got a redundant old PC lying around somewhere (or friends/family have one)? As long as it isnt a 486 its probably good enough (processing power wise) to perform crossover/eq duty... Audigy 4 cards (with rather nice dacs and more outputs than you need) are available on ebay for dollars. With kx drivers you can get an instant taste of active crossovers + eq right in comfortable windows.... like it then move on to linux for proper lin phase filters, incredible playback software and proper drivers (no where near as steep a learning curve as it used to be with distributions like ubuntu around now).... A couple of cheap amps (for testing)... and your away. Infinitely customisable within seconds, brick wall 60/oct filters, 100+ band linear phase transparent eq, easy measurement etc.... there are lots of advantages, and with first endeavours being so cheap as long as your fairly computer literate, its a nice place to start. Not to mention lossless formats and EAC bit perfect CD ripping....
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