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.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.
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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