Neo8 line array, mounting.

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aceinc

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Neo8 line array, mounting.
« on: 30 Jul 2019, 03:00 am »
I am contemplating building a line array using 8 Neo8s per side.

My question is how to mount the Neo8s.

My baffle will be between 1" & 1.5" depending on feed back.

My conflicting train of thoughts are;

  • Surface mount.
  • Rear mount with some form of wave guide.

Even if the drivers are surface mounted you need to deal with the sound from the rear anyway, requiring a chamfer or something.

Rear mounting has at least one downside, the heads of the screws that hold them together would interfere without rear mounting.

Otherwise, rear mounting seems like it would be easier. Just cut a single ~64" rectangle and butt the Neo8s against one another vertically.

Rear mounting also seems to get the Neo8 closer to the plane of the voice coil in the mid-bass driver as well.

So, if I rear mount these puppies, and I have 1" to 1-1/2" of baffle thickness to work with, what should the area surrounding the Neo8s look like? Chamfer, concave, convex...? Is there a way of identifying the best shape, before making sawdust?

The goal of course is to provide the most even freq response over the widest horizontal plane.

So what are some thoughts on a Neo8 array in general and how best to mount them specifically?

Danny Richie

Re: Neo8 line array, mounting.
« Reply #1 on: 31 Jul 2019, 12:41 pm »
For the line arrays that we used them in we front mounted them and we added a large radius on the back side of the through hole.

And you can adjust the time alignment to your other drivers by slight toe in or toe out.

AKLegal

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Re: Neo8 line array, mounting.
« Reply #2 on: 31 Jul 2019, 02:19 pm »
Hey Danny, how many Neo 8s do you think it would take to reach 200 hz or lower in a open baffle?

aceinc

  • Jr. Member
  • Posts: 284
Re: Neo8 line array, mounting.
« Reply #3 on: 31 Jul 2019, 02:54 pm »
Danny,

When mounting from the front, did you (and would you recommend)

  • Surface mount or recess mount the depth of Neo8 frame?
  • Cut a single long rectangle, or cut a Neo8 size rectangle for each driver?

The drivers I am looking at mating it with, Peerless SDS-135F25CP05-04, seem to be capable of up to about 2khz fairly flat. My thought is 12 of these and 8 of the Neo8s on a 9"-10" baffle. The overlap of usable frequencies seems to be fairly broad, so it appears there are a lot of choices for crossover points & slopes in the 300hz-1khz range. What are your thoughts on the general parameters of the crossover?

Danny Richie

Re: Neo8 line array, mounting.
« Reply #4 on: 31 Jul 2019, 04:35 pm »
Hey Danny, how many Neo 8s do you think it would take to reach 200 hz or lower in a open baffle?

Neo 8's are just not going to play that low. In the LS-9 I crossed them at 850Hz. And that was at the top of the mid-range (vocal range). You either need to stay just above it or use Neo 10's to get just below it. They can reach down into the mid 100's to 200Hz range pretty well.

Danny Richie

Re: Neo8 line array, mounting.
« Reply #5 on: 31 Jul 2019, 04:45 pm »
Danny,

When mounting from the front, did you (and would you recommend)

  • Surface mount or recess mount the depth of Neo8 frame?
  • Cut a single long rectangle, or cut a Neo8 size rectangle for each driver?

The drivers I am looking at mating it with, Peerless SDS-135F25CP05-04, seem to be capable of up to about 2khz fairly flat. My thought is 12 of these and 8 of the Neo8s on a 9"-10" baffle. The overlap of usable frequencies seems to be fairly broad, so it appears there are a lot of choices for crossover points & slopes in the 300hz-1khz range. What are your thoughts on the general parameters of the crossover?


I would flush mount them. And if they are sealed and have a rear chamber behind them then you can get by with a long slot. However, for an open baffle application that is not going to be structurally strong enough unless the MDF is 1.5" thick or more. You'll need to cut out a section for each one or leave some cross section for support.

Those woofers look like good candidates for what you are doing.

The trick is to match the sensitivity of each group and the output levels. The sensitivity of the tweeters is still limited to the output level of one tweeter in the top octave. So the filter needs to pull everything else down to that level in the lower ranges. So you will be about 91db or so. To match that you might need to run the woofers in two groups of five. If you parallel more than one group then you might exceed the sensitivity level of the tweeters. And you can't add inline resistors to the woofer circuit.

aceinc

  • Jr. Member
  • Posts: 284
Re: Neo8 line array, mounting.
« Reply #6 on: 31 Jul 2019, 08:03 pm »
Yes I am thinking OB on the Neo8s. When last I worked with them, the cutouts were a PITA because of the notch for the connectors. I am considering making the baffle out of a combination of two types of wood with a permanently flexible glue between the layers. The thickness would be 1-1/4"-1-1/2" depending on what I use.

Regarding the woofers, I was thinking about 3 parallel groups of 4 series. In other words 4 woofers hooked in series yielding 12 ohms, each of those groups hooked up in parallel, yielding an overall 4 ohms per cabinet. I'm thinking that might yield about 95DB at 1 watt.

Quote
The sensitivity of the tweeters is still limited to the output level of one tweeter in the top octave.

The response curve of the Neo8 shows 91 DB average in the 300hz-10khz range with a hump centered around 12khz. Does placing them in a line array raise the level below 10khz up to the level of the 12khz hump?  More simply put, what can I expect as the efficiency of 8 - Neo8s in an array?

Danny Richie

Re: Neo8 line array, mounting.
« Reply #7 on: 31 Jul 2019, 08:25 pm »
Yes I am thinking OB on the Neo8s. When last I worked with them, the cutouts were a PITA because of the notch for the connectors. I am considering making the baffle out of a combination of two types of wood with a permanently flexible glue between the layers. The thickness would be 1-1/4"-1-1/2" depending on what I use.

You should be about to add a little connection from side to side at the top of each driver.

Quote
Regarding the woofers, I was thinking about 3 parallel groups of 4 series. In other words 4 woofers hooked in series yielding 12 ohms, each of those groups hooked up in parallel, yielding an overall 4 ohms per cabinet. I'm thinking that might yield about 95DB at 1 watt.

Your impedance will be low and your sensitivity too high that way.

Quote
The response curve of the Neo8 shows 91 DB average in the 300hz-10khz range with a hump centered around 12khz. Does placing them in a line array raise the level below 10khz up to the level of the 12khz hump?  More simply put, what can I expect as the efficiency of 8 - Neo8s in an array?

At the top end you'll still just have 91db sensitivity. The output will not couple with the other drivers up there. And you will still need to add a little notch filter to knock the peak down a little. The rest of the filter will be dealing with how the output increases as frequency decreases from all of them coupling with each other. You'll have a lot of gain down low.

aceinc

  • Jr. Member
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Re: Neo8 line array, mounting.
« Reply #8 on: 31 Jul 2019, 08:55 pm »
I just realized I did my math wrong, I was hoping nobody caught it and I could fix it.

3 parallel groups of 4 in series would be 4 x 4 = 16 ohms / 3 = ~5.3 ohms, not 4 ohms.

I caught my problem while trying to calculate the impedance of the Neo8s.  With 8 Neo8s, it appears the impedance choices are .5, 2, 8 or 32.

So perhaps the Neo8s should be 2 parallel groups of 4 in series yielding 8 ohms, and the woofers should be 2 parallel groups of 6 in series for 12 ohms. This would knock down the relative sensitivity of the woofer section.

Danny Richie

Re: Neo8 line array, mounting.
« Reply #9 on: 31 Jul 2019, 09:31 pm »
I just realized I did my math wrong, I was hoping nobody caught it and I could fix it.

3 parallel groups of 4 in series would be 4 x 4 = 16 ohms / 3 = ~5.3 ohms, not 4 ohms.

I caught my problem while trying to calculate the impedance of the Neo8s.  With 8 Neo8s, it appears the impedance choices are .5, 2, 8 or 32.

So perhaps the Neo8s should be 2 parallel groups of 4 in series yielding 8 ohms, and the woofers should be 2 parallel groups of 6 in series for 12 ohms. This would knock down the relative sensitivity of the woofer section.

When figuring the impedance's go by the dcr and not advertised impedance.

And yes, do two groups of four tweeters. The woofers can be two groups of five or two groups of six. You might check the width of the frames to see how long each line is getting.

Mike 1960

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Re: Neo8 line array, mounting.
« Reply #10 on: 8 Dec 2021, 09:45 pm »
When figuring the impedance's go by the dcr and not advertised impedance.

And yes, do two groups of four tweeters. The woofers can be two groups of five or two groups of six. You might check the width of the frames to see how long each line is getting.

Wow I wondered about that! (When figuring the impedance's go by the dcr and not advertised impedance.) Glad I continue to look for info. I was actually going to ask about that.