Active crossovers and speakers - amplification? - Page 4 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #31 of 41 Old 02-13-11, 09:52 PM Thread Starter
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Re: Active crossovers and speakers - amplification?

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Bear, is that the brand?

So is the mid/HF coax driver able to be powered separately or does the HF driver leach power off the Mid's amp and use passive components for for the Tweeter's LP and Mids HP?

In my system, I have a 70 watt amp and a 30 watt amp. The 30 watt Amp drives the three tweeters with signal from 2K and up. I had to add resistance in series to the tweeters to bring the load back up to 4 ohm from 1.3ohm. These amp modules are actually designed around an 8ohm load (as are most AVRs), however I've been running 4 ohm loads now for 11 years and not fried anything yet.
Sorry! Meant bear as in tough!!

Crossover temporarily is JBL M553. Going to upgrade to DBX Driverack PA+ or DCX2496. The JBL is very limited. You pick crossover frequencies - and you can change gain for low/mid/high - but that's it.

I'm actually planning on going entirely active. Yes, it means more amps and more cabling...

The coax mid/HF drivers are completely separate and require a crossover.. I forget what the efficiencies are - but it's a few db.. Enough that I've not given a whole lot of thought to trying passive. The HF driver actually radiates through the fabric dust cap of the midrange.


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post #32 of 41 Old 02-14-11, 03:16 AM
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Re: Active crossovers and speakers - amplification?

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So with my mids and tweeters being 4ohms and the bass units being 8 do you think i'll have to add anything to attentuate the volume of the drivers or to get all the impedances to match?If so what would i use?
I am not familiar with your design, but if it were my own, I'd be using two 8 ohm woofers in parallel which is then a 4 ohm load and up to 6dB more efficient than the single 8 ohm driver - basically, the amp does not have to work as hard to achieve the same SPL. Because you are going active, each band is managed independently, so you can run 4 and 8 ohm loads without incident. There should be trims on the HP to allow you pull down the level if it is too high. Drivers pending, you may need to install a passive L pad network to attenuate the HFs. In the case of my 2CH amps, they rely on this and why the HP section is just 30W. It needs the tweeter to be louder then the woofer. In my case, I made up that extra gain by wiring three XTs (they are only about 91dB, most tweeters are 94dB) and the three have given me some 8dB gain. Because I have used series resisters to bring the 1.3ohm load up to 4 ohm, I got a loss which has worked out to be pretty much right.

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Sorry! Meant bear as in tough!!

Crossover temporarily is JBL M553. Going to upgrade to DBX Driverack PA+ or DCX2496. The JBL is very limited. You pick crossover frequencies - and you can change gain for low/mid/high - but that's it.

I'm actually planning on going entirely active. Yes, it means more amps and more cabling...

The coax mid/HF drivers are completely separate and require a crossover.. I forget what the efficiencies are - but it's a few db.. Enough that I've not given a whole lot of thought to trying passive. The HF driver actually radiates through the fabric dust cap of the midrange.
If you can wing going fully active, don't bother with passive - phase changing, power robbing etc etc etc. The only reason most speakers are passive is cost. It is not even case of simplified wiring as mine have a single RCA in only, so provided the AVR has full pre-outs (all THX certified AVS do), it is all good.
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post #33 of 41 Old 02-14-11, 07:28 AM Thread Starter
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Re: Active crossovers and speakers - amplification?

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If you can wing going fully active, don't bother with passive - phase changing, power robbing etc etc etc. The only reason most speakers are passive is cost. It is not even case of simplified wiring as mine have a single RCA in only, so provided the AVR has full pre-outs (all THX certified AVS do), it is all good.
I have an Onkyo PR-SC886 w/RCA and XLR pre-outs... so I feel like I'm in pretty good shape to "play".

It was fun bundling 450 feet of speaker wire into 3 bundles of 3 runs each (Low/Mid/high cables in each bundle, and 3 bundles because of L, C, R). I did 50 feet runs so I have plenty of distance - even though it's way overkill. I wanted excess so I can figure out where I'm putting everything! So.. you talk of simplicity in wiring with your modules.. Yep.... That's for sure.


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post #34 of 41 Old 02-14-11, 05:43 PM
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Re: Active crossovers and speakers - amplification?

My original plan was to mount the 2CH amp modules in the EQ Rack and run extra cables to the speakers. I figured this might be OK, however as I went along, it was more of a pain than anything and I figured that since the SUB runs an RCA to its built in plate amp, why not do the same for the LCRs? And so that is what I did. All I had to change in my room was the RCA terminal plate (from single to multi) at each end of the room and run the 3RCA leads. I already had filtered power at that end of the room for the SUB, so that was a non issue as well.

The bonus is that should I upgrade my AVR (and I will for 3D at some point soon) to have Z or height channels, the speaker cables are already in place. And I have over 200mm (8") of space above the screen, so a perfect place to mount them too.
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post #35 of 41 Old 02-21-11, 08:55 AM
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Re: Active crossovers and speakers - amplification?

I use active crossovers (miniDSPs) for all front channels. I have ten channels of amplification for my 5.1 surround setup. My amps are Emotiva and deliver anywhere from 140 watts RMS to 300. Getting it wired up was very complicated for me, I burnt out a tweeter while doing it. But even with the challenge of getting every driver hooked up with the same polarity and correct channel the sound benefits are tremendous. With the same brand of amplifier getting the levels correct is easier.
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post #36 of 41 Old 02-21-11, 10:06 AM Thread Starter
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Re: Active crossovers and speakers - amplification?

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I use active crossovers (miniDSPs) for all front channels. I have ten channels of amplification for my 5.1 surround setup. My amps are Emotiva and deliver anywhere from 140 watts RMS to 300. Getting it wired up was very complicated for me, I burnt out a tweeter while doing it. But even with the challenge of getting every driver hooked up with the same polarity and correct channel the sound benefits are tremendous. With the same brand of amplifier getting the levels correct is easier.
Since Emotivas don't have a gain knob for individual channels.. I assume the miniDSPs allow you to change the level of the signal enough - to level match the individual drivers?


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post #37 of 41 Old 02-21-11, 04:04 PM
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Re: Active crossovers and speakers - amplification?

What is the model # for the miniDSP's that you are using? Thanks.
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post #38 of 41 Old 03-07-11, 03:59 AM
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Re: Active crossovers and speakers - amplification?

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Since Emotivas don't have a gain knob for individual channels.. I assume the miniDSPs allow you to change the level of the signal enough - to level match the individual drivers?
Yes of course. The miniDSPs have both input and output level controls. The output at max matches the Emos perfectly.
The one problem I''m having right now is that the output voltage is only .9 volts, just right for the Emos but too low to use a pro amp on the subs.
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post #39 of 41 Old 03-07-11, 04:02 AM
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Re: Active crossovers and speakers - amplification?

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What is the model # for the miniDSP's that you are using? Thanks.
I use a miniDSP In A Box type a (http://www.minidsp.com/minibox/minidsp-2x4, unbalanced). There are balanced versions too.
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post #40 of 41 Old 03-07-11, 09:10 AM Thread Starter
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Re: Active crossovers and speakers - amplification?

Cool. Thanks for the feedback.

My concern wasn't just changing the gain.. but changing it ENOUGH to match the drivers... Since some drivers can be quite different in terms of efficiency.

Thanks!


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