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post #21 of 41 Old 02-13-11, 01:20 AM
Mark Techer
 
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Re: Active crossovers and speakers - amplification?

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Zeitgeist wrote: View Post
I've seen some interesting plans for 2-3 way speakers that use active crossovers.. By active crossovers, I mean Behringer DCX2496 or some of the cheaper models.

However, with active crossovers and separate line level outputs - with a pair of 3 way speakers, you're looking at having 6 sources to amplify. What do most DIY builders do - when they need to amplify 4-6 channels for a pair of speakers?

Multiple pairs of amps? Or a multichannel HT amp?

Or...... are active crossover arrangements that uncommon because of the issues with number of amp channels needed.
Last year I upgrades from passive to active. My project was to convert my LCRs from a 2 way passive system to a 2 way Active system. Because I have 3 identical LCRs, I would need 6CH of amplification. The challenge I faced was finding a suitable crossover to match my driver layout. These speakers have to fit into cutouts that are part of my baffle wall behind my AT screen, so it wasn't going to a case or a complete redesign unless I changed the baffle wall as well. I needed to find an active crossover close to the frequency I was using in the passive system in order to maintain the same driver spacing that controls the vertical dispersion of the speaker. The passive system uses 1550Hz which was proving to be a challenge as all the products I saw used higher crossovers.

Basically, as I searched the net for active crossover, I found a few products that would do the job, however hideously expensive by the time one added amplification. I even turned to JANDS who make active modules for JBL powered speakers and no luck on anything "affordable" as the cheapest units they had were over $1000 each.

I contacted the speaker company I buy my drivers from and asked what solutions they could offer. As it turns out, they were testing a small 2CH module with a 2K 4th order LR crossover and they seemed impressed with what they had. These modules have 70W LP and 30W HP and a 2K crossover. They praised the product, so I took a leap of faith and bought 3 units.

To convert my speakers from 1550Hz to 2000Hz meant I had to reduce the centre to centre spacing of the tweeters. I elected to have a new set of baffles made out of ABS plastic as opposed to the making new baffles from 25mm MDF. I also made myself some new trapezoid enclosures. Doing this added a few liters to compensate for what the 2CH amp module would take up as well as giving me the proven benefits of such a shaped enclosure - IE the two side walls are no longer parallel.

The key being that in order to reduce the spacing, I had to over lap the drivers, so counter sinking the centre driver. I built my first speakers with controlled vertical directivity in 1998 and this is actually set 5 for me. Because those designs worked so well, I've continued to do the same thing for the different designs including these current speakers.

Because my drivers are wired in parallel and the VIFA XTs I use a 4ohm, I had to make impedance matching for the HP section. The two woofers were 8ohm, so no problems there. Even though I use an 80Hz crossover to the LCRs, I still used a simple impedance network on the LP section.

The modules are basic. They have a single RCA as the input and they have an IEC (jug cord) power socket. There is HP/LP trims and a power switch. The end result is they work well. They play loud and deliver greater dynamics than the previous passive speakers could offer.

Image 1: A simple diagram showing amplification after the crossover.
Image 2: The back of the Amp module.
Image 3: I used a double binding post terminal plate to connect the four wired from the AMP modules. Notice the bridging straps are removed. I then mounted the other components needed to back of the plate and this then was attached to the inside of the enclosure.
Image 4: New and Old side by side.
Image 5: The back of the L and C speakers once the LCRs were installed back in the baffle wall.
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post #22 of 41 Old 02-13-11, 10:13 AM Thread Starter
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Very interesting Mark. I recall seeing that you had to change the spacing of your tweeters but didn't fully understand that it was due to a change in your crossover frequency.

I am going to post a build thread....but I'm working on a 3 way build.. I have a few Crown Microtech amps and for the short term going to use a JBL M553 (a 3 way stereo crossover). I plan on upgrading to a DCX2496 or DBX Driver PA+ and maybe QSC DCA amps to replace the Crowns.

Your setup looks great - especially with the modules. I'd love to buy some Digmoda modules....but they're not cheap and unfortunately Speakerpower is OEM only.

You said Vifa treaters...what did you use for woofers?


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post #23 of 41 Old 02-13-11, 08:20 PM
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Re: Active crossovers and speakers - amplification?

The drivers are all VIFA (XT super tweeters and P17 woofers) and infact the tweeters actually have "MADE IN DENMARK" on the magnetic shielding cups (yes I used shielded drivers as well).

Late 2009/early 2010, I built two sets of the older passive design and the same model speakers have now "DESIGNED IN DENMARK". I am therefore left to assume that means made in China. Even so, China can produce some very high quality products and these drivers looked exactly the same and sounded beautiful once the systems were completed.

As I understand it, VIFA and Peerless combined to produce PEERLESS AUDIO ENGINEERING (AKA PAE) and all the line are made in China, yet they perform well.

Yes the 2CH amp modules are neat and take out the excess cable mess that I had when I ran a car electronic crossover for bass management a few years ago. This is very PLUG N PLAY now.

I've always been a fan of vertical directivity and thinking back, I've had some form of that for every speaker I've owned (hmm interesting). So it was just a case of working out what I needed to do to make it happen.

So a three way? Single W M T or something like W MTM W? And yes, having heard the same drivers in a passive system, then active, the active is the way to go. Clean, powerful. I think I might have to go out and listen to them now
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post #24 of 41 Old 02-13-11, 08:49 PM
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Re: Active crossovers and speakers - amplification?

With all the talk of the extra amp channels needed it got me thinking of how many i'll need, after the math i should have more then enough: 2 UPA-5's 1 XPA-5's and 2 XPA-1's that should be plenty enough to do 3 amp channels per speaker (L-C-R). One thing after reading a couple posts here is that i relized my tweeter is 4ohms as well as my mids, will that present a problem i'll need to over come or will i be good to go? my active crossover is a DCX2496.
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post #25 of 41 Old 02-13-11, 09:10 PM Thread Starter
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Re: Active crossovers and speakers - amplification?

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With all the talk of the extra amp channels needed it got me thinking of how many i'll need, after the math i should have more then enough: 2 UPA-5's 1 XPA-5's and 2 XPA-1's that should be plenty enough to do 3 amp channels per speaker (L-C-R). One thing after reading a couple posts here is that i relized my tweeter is 4ohms as well as my mids, will that present a problem i'll need to over come or will i be good to go? my active crossover is a DCX2496.
Do you really have that much Emotiva gear? If so - I'm jealous! I have a UPA-7 which I love.

I think that almost any Emotiva gear can handle 4 ohms without a problem.

I think the one thing that you might run into - is whether you can cut the 4 ohm drivers enough to drive them at a similar level as the 8 ohm ones --- or boost the 8 ohms enough to get them to match. I think unfortunately, you can't adjust the gain on each channel of the Emotivas.

You thinking 2 or 3 ways? You'll need at least a couple more DCX2496s, I think.


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post #26 of 41 Old 02-13-11, 09:12 PM Thread Starter
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Re: Active crossovers and speakers - amplification?

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Mark Techer wrote: View Post
As I understand it, VIFA and Peerless combined to produce PEERLESS AUDIO ENGINEERING (AKA PAE) and all the line are made in China, yet they perform well.

So a three way? Single W M T or something like W MTM W? And yes, having heard the same drivers in a passive system, then active, the active is the way to go. Clean, powerful. I think I might have to go out and listen to them now
That's interesting aboue PAE. I recall reading about some recent(ish) changes that have occurred - regarding where they are actually made.

Yup........ a WCW
AE TD12S - Coax (B&C 8CXT) - AE TD12S

Crossover and EQ will be a bear, but should sound great!


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post #27 of 41 Old 02-13-11, 09:14 PM Thread Starter
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Re: Active crossovers and speakers - amplification?

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As I understand it, VIFA and Peerless combined to produce PEERLESS AUDIO ENGINEERING (AKA PAE) and all the line are made in China, yet they perform well.

So a three way? Single W M T or something like W MTM W? And yes, having heard the same drivers in a passive system, then active, the active is the way to go. Clean, powerful. I think I might have to go out and listen to them now
That's interesting about PAE. I recall reading about some recent(ish) changes that have occurred - regarding where they are actually made.

Yup........ a WCW
AE TD12S - Coax (B&C 8CXT) - AE TD12S

Crossover and EQ will be a bear, but should sound great!


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post #28 of 41 Old 02-13-11, 09:29 PM
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Re: Active crossovers and speakers - amplification?

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Do you really have that much Emotiva gear? If so - I'm jealous! I have a UPA-7 which I love.

I think that almost any Emotiva gear can handle 4 ohms without a problem.

I think the one thing that you might run into - is whether you can cut the 4 ohm drivers enough to drive them at a similar level as the 8 ohm ones --- or boost the 8 ohms enough to get them to match. I think unfortunately, you can't adjust the gain on each channel of the Emotivas.

You thinking 2 or 3 ways? You'll need at least a couple more DCX2496s, I think.
Emotiva certainly makes some good amps and with there sales they have had lately it makes them hard to pass up (I think it's OCD,LOL). I'm not so worried about the amps being able to deliver as i am the level matching, i'm doing 3-ways with the center possibly being passive but haven't set that one in stone yet. I too wish there was some sort of gain control on the amps, who knows maybe the DCX will have some sort of feature like that i haven't had a chance to play with it yet and it will probly be a few months before i am able to actually sit down and mess with it as i like you have 200 projects going on top of hanging with the twins.
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post #29 of 41 Old 02-13-11, 09:41 PM
Mark Techer
 
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Re: Active crossovers and speakers - amplification?

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bambino wrote: View Post
With all the talk of the extra amp channels needed it got me thinking of how many i'll need, after the math i should have more then enough: 2 UPA-5's 1 XPA-5's and 2 XPA-1's that should be plenty enough to do 3 amp channels per speaker (L-C-R). One thing after reading a couple posts here is that i relized my tweeter is 4ohms as well as my mids, will that present a problem i'll need to over come or will i be good to go? my active crossover is a DCX2496.
For a 3 way active system, you will need 9 channels of amplification or three per speaker.
I run 2 way LCRs, so I use 6. Some day, I'd like to extend that level of performance to the surrounds as well. I can only imagine what a active 3 way LCR array sounds (or is that pounds?) like My 2 way LCR array lets you know it is running I can tell you.

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That's interesting aboue PAE. I recall reading about some recent(ish) changes that have occurred - regarding where they are actually made.
Looking at the WES catalogue, it does appear that PAE is made in China. I am assuming the other VIFA and Peerless drivers are made there as well now. I choose VIFA because they were (at the time I started buying them anyway) made in Denmark. I'm sure the XLS woofers I use in my SUBs also have a place of manufacture as Denmark as well. I didn't see that on the last two sets I made.

Quote:
Yup........ a WCW
AE TD12S - Coax (B&C 8CXT) - AE TD12S

Crossover and EQ will be a bear, but should sound great!
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.
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post #30 of 41 Old 02-13-11, 09:51 PM
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Re: Active crossovers and speakers - amplification?

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?




Thanks Jim for letting me Hijack your thread by the way. LOL.

Last edited by bambino; 02-13-11 at 09:52 PM. Reason: added comment
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