8ft Line array Build.

[T85matt]

So earlier I posted that I was planning on building a CBT. However I decided to go for something a little simpler. It is coming along great. Cant wait to get it done I have figured out all the tuning with bassbox Pro. I am using 30 Fountek FE87 drivers per array in a 120 liter box tuned to 65hz,

 

[jerryo]

Looks like you're having a lot of quality time working in your garage workshop. Good work. Are the enclosures sealed or ported? Sealed by the look of it. If so, try putting the expected design parameters through a Linkwitz Transform which might allow you to get down to 40Hz without any excursion issues, as each of your drivers will only ever need a watt or two.

 

[T85matt]

They are actually going to be ported. I wanted to get my ports before I put any extra holes in them. Measure 12 times cut once. Do you have a link to show what your referring to. I've heard of linkwitz labs. Are they similar?

 

[T85matt]

getting more and more work done. Feels like progress is relatively good since I cannot work on them on weekdays.



Routed out speaker mounting location. I need help figuring out how to get a good seal on all of the speakers

Mounting hardware chosen.

Beveled bolt edges for a clean look. The box will be done in gloss black vinyl and the face will be painted a color that somehow makes the WAF of the monstrosities tolerable.

Thanks,
Matt

 

[jerryo]

Hi,
if they are to be ported then the Linkwitz Transform does not apply as it only works with sealed boxes. It's normally used for subwoofers but can also be applied to all sealed speakers (with caveats) to modify the response of the drive unit. I've done some modelling of a line array using drivers that are perhaps more suited to a ported box,in a sealed box. Of course the box volume using so many drivers is very large so by using the Linkwitz Transform you can reduce the box volume considerably and still maintain the required frequency response. You can also drop the bottom end of the response to a degree depending on how much driver excursion you have to play with and the amount of power going through each driver, which for a line array will be very low because of the efficiency gains.
Linkwitz Labs 'is' the inventor of the circuit.
This information is what I have found by using the free WinIsd Pro speaker modelling software which has the Linkwitz Transform as a built in option.

 

[T85matt]

Cool. I will have to take a look at that on my next project. . Any idea how to get a good seal on those drivers. I've heard everything from a caulking type compound to petroleum jelly.

 

[T85matt]

mlv like in the TT build?

 

[ondesx]

I suppose that you probably know that you'll experience some comb filtering and limitation in high frequency ? For 8 cm center-to-center spacing of the drivers, taking 340 m/s for sound's speed, first cancellation will appear at 9500 Hz...

 

[T85matt]

Yes. But from what I've heard that effect is less apparent in real life music reproduction as it is in theory. Also, I have a 22ft long room to play with so the effects a certain distance should minimized. We will see. Unfortunately there isn't a hifi shop you can go to to have a listen to a pair. So it a pretty big gamble. But I knew that when I started.

 

[nerdorama]

The Linkwitz Transformer can be done with a miniDSP unit as well. I use one in my subwoofer channel to do both the low pass and the transform.

Looks like a fun project.
John

 

[T85matt]

The Linkwitz Transformer can be done with a miniDSP unit as well. I use one in my subwoofer channel to do both the low pass and the transform.

Looks like a fun project.
John

Thanks. I have the DEQ2496 which has a DSP however I am trying to decide if I should return it for the DCX2496le. Both are similar price points but I am not sure which will be more conducive to tuning arrays. I bouch from Amazon and I have almost thee weeks to return it. Any input there?

It's been a blast so far. My friend has been helping me move them around and doing some of the sanding and routing. They are beastly. Can't wait to listen and tune them.

 

[nerdorama]

I also have a DEQ2496. I would avoid using it in a main channel without modification. It has a lousy sounding analog output section. I bypassed mine with a line matching transformer. It was such a magnificent change that I would never use one with the factory analog circuits.

If you knew the proper EQ for the Linkwitz Transform, the DEQ2496 could be adjusted to do the same EQ.
John

 

[T85matt]

I also have a DEQ2496. I would avoid using it in a main channel without modification. It has a lousy sounding analog output section. I bypassed mine with a line matching transformer. It was such a magnificent change that I would never use one with the factory analog circuits.

If you knew the proper EQ for the Linkwitz Transform, the DEQ2496 could be adjusted to do the same EQ.
John

I am aware of it already. whoa. my rca to xlr connector may be a contributing factor as well. The initial settings had a fair amount of noise. I have tweaked everything so that my signal is as strong as possible going into the EQ and for the time being I am using a small amp that was being used for output to my rear surrounds. It has a volume dial so I can lower the sound on my audiosource 100 to adjust for the higher input signal. I am looking at the kit for improving both analog circuits.

Here is a project I just finished. 4 lines of CAT5 twisted speaker cable. (into a rope that would hold a tractor.) 2 for ground 2 for positive. I had a 1000 feet lying around so why not. Definitely an improvement, smother bass response was the first thing i noticed. Link Speaker Cable Faceoff 3 - The DIY Shootout | Audioholics

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An externally hosted image should be here but it was not working when we last tested it.

Thats 20 feet for some perspective

 

[T85matt]

I also have a DEQ2496. I would avoid using it in a main channel without modification. It has a lousy sounding analog output section. I bypassed mine with a line matching transformer. It was such a magnificent change that I would never use one with the factory analog circuits.

If you knew the proper EQ for the Linkwitz Transform, the DEQ2496 could be adjusted to do the same EQ.
John

Is the line matching transformer different then the other upgrades I have see online?

 

[nerdorama]

Not sure, but likely the same or similar. I bypassed all of the analog output section from the DAC chip and direct connected the line matching transformers. The secondaries are connected directly to the new RCA jacks I installed where the original 1/4" jacks were mounted. The output level went up, which I didn't expect, and the sound is much more dynamic and alive.
John

 

[T85matt]

Not sure, but likely the same or similar. I bypassed all of the analog output section from the DAC chip and direct connected the line matching transformers. The secondaries are connected directly to the new RCA jacks I installed where the original 1/4" jacks were mounted. The output level went up, which I didn't expect, and the sound is much more dynamic and alive.
John

Was it of your own design or do you have a link? Sounds promising.

 

[nerdorama]

I bought the transformers directly from O-netics and worked out the installation on my own. You can see the 10148 part number in the pictures I attached in post 12. They are a PC board mount type of transformer so I mounted them on perfboard and soldered the wires around the legs to hold them. I found the information about the DAC chip and the Behringer board layout mostly here on DIYaudio. If you would like to pursue it I can email to you the files I collected while doing this project. BudP is the DIYaudio handle for the owner of O-netics. Just about any 600ohm:600ohm type line matching transformer would work, but I would try to get some good ones. I've also got a pair of UTC A-20's but haven't tried them on a dac.

 

[T85matt]

Whould you pm those to me. That would be awesome.

Still working on the arrays. I have the damping in and am about ready to get started on mounting and wiring the speakers. I decide that I am going to use a foam seal for Windows to seal the speakers. I wanted to find something easier but alas that is the only simple and cost effective option I could think of. Will post pictues soon

 

[nerdorama]

Sorry matt,
Can't do attachments on PM's. You'll have to give me your email.
John

 

[nerdorama]

Thanks. I have the DEQ2496 which has a DSP however I am trying to decide if I should return it for the DCX2496le. Both are similar price points but I am not sure which will be more conducive to tuning arrays. I bouch from Amazon and I have almost thee weeks to return it. Any input there?

Sorry. I never gave you an answer on this. I've never seen the DCX2496le. It's all analog in/analog out but looks like it would have the EQ functions you might want. It can also act as an active crossover which the DEQ does not do. The DEQ is strictly an EQ but has digital in/out. I feed it digital from my music server which save one analog conversion on the input side. So, if you want an active crossover the DCX is the one. If you just need EQ and want to use it like any other DAC, go the DEQ. I also use a miniDSP 2X4 to do my subwoofer crossover. It has some nice speaker specific EQ functions (particularly for me, subwoofer functions) that would be more difficult to do with either of the Behringers.

John