# Figuring out tri-amped LCR speakers



## erwinbel (Mar 23, 2010)

Hi, 

First time on this side of the HTS!

I am creating a HT with the 3 front speakers DIY using SEOS 24 + BMS 4594ND coaxial + dual Beyma 18P80Nd woofers. For the moment, I will have a go at a triple active digital crossover using the *miniDSP 4x10HD* [2]. For the moment, since I have learned some people experience issues with hiss due to the combination of very sensitive horn speakers and the noise floor of the miniDSP. We will see how it goes.

The center speaker box is done and the drivers mounted. The 3 fronts have the same parts, but the boxes are shaped different since the center is behind a AT screen and the left and right front aren't. The center will be my learning device. 

I have both miniDSP 4x10HD boxes which allow for 24/96 processing and balanced connections. Also have the *UMIK-1* with calibration file. I used the mic before with Dirac in my stereo with Amarra. 

I have enough amps for a full blown Atmos 9.1.6 system, although my current processor is the XMC-1, hence no Atmos yet. I have a XPR-5 of which 3 channels are for the low end of the LCR. Then I have 2 Marantz MM8003 (8ch) of which I will use 6 channels for the mids and highs.

First I want to measure the drivers of the center outdoors. This will be a real pain, since I went OTT using very thick MDF resulting in a speaker weighing about a ton, so it feels!

My son has a 2yo Macbook pro which we will use to work with. I reckon I can connect the Macbook to the processor using HDMI, right? 

I was wondering if I needed REW already to do the outdoor measurements? I have been dry-fiddling with the miniDSP plug-in but it's not clear yet how to actually generate the test sounds. 

Also, do I need anymore outdoor measurements after the first one? I mean, it seems I need to sum the tweeter + the midrange before adding the woofer? 

Thanks for any tips!


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## Lumen (May 17, 2014)

Hello Erwin, and welcome! I moved your post to the DIY Speaker forum to help get more exposure. Somebody over there will surely be able to help.


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## NBPk402 (Feb 21, 2012)

I believe if you place the mic close to the speaker you can run REW, and take the room out of the equation.


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## erwinbel (Mar 23, 2010)

*The center*

Here is the big bugger. It weighs about 2 ton.


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## NBPk402 (Feb 21, 2012)

I would just put your mic maybe a foot away, and measure. When we did my setup we actually did it from the MLP, and then looked at REW to see where to cross over the speakers. My reason was that it made more sense (to me) to measure in the room that they will be in, and from the MLP (since that is where you want the best sound).


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## erwinbel (Mar 23, 2010)

Do you mean crossing over a whole speaker to the sub or the crossover of the drivers in the speaker? I thought it was best to get an outside measurement first so the room does not mudden things up.


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## NBPk402 (Feb 21, 2012)

erwinbel said:


> Do you mean crossing over a whole speaker to the sub or the crossover of the drivers in the speaker? I thought it was best to get an outside measurement first so the room does not mudden things up.


When we did my 2 way setup... I only turned on the amp for the driver I wanted to measure with REW. I then overlaid the results to determine where the crossover should be. Outside would be best, but I don't think it is necessary. Once you have the crossover set where it should be (for the speaker), then I would run the sub by itself to see how it reacts in your room, and overlay the results with an overlay of the complete 3 way speaker. :T


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## jtalden (Mar 12, 2009)

Nice speakers.

I also think that the XO can be properly setup using indoor measurements. The lower the XO frequency the more the room can impact the measurements, but we can usually do it even with mic at the LP for a SW XO. For your speakers a 1-2m mic distance should provide a relative clean measurements for this purpose so it should be no problem. 

The more complicated part is determining the amount of delay needed when using a USB mic and REW. An option may be to use HolmImpulse. I use only XLR mics so I am not 100% sure, but would expect that the timing lock in Holm would work just fine with that mic. That would make it much easier.

Given the proper measurements, I can assist with determining the best timing using either REW or Holm if you are unsure how to do that. I recommend that the target should be to have close phase tracking between the drivers throughout the entire XO range.

Most DIY builders probably want the see what the speaker response is after the XO is finalized and that would be the better time to take them outside for measurement. They can then be EQed there to provide a flat response. Most speaker designers maintain that a flat near-field response above the Schroeder frequency is very important. That is very difficult to determine indoors for the midrange frequencies (~300-800Hz). So if you want to EQ them flat, outside is probably better. I didn't bother to do that as I intended to EQ my setup just using LP measurements. Outside would be very problematic in my situation anyway. I am very satisfied with the sound quality just doing it all indoors.


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