Mid-bass line array -extremis

[JonFo]

I’m designing a mid-bass array to augment an ESL panel with. This line array will be 4’ long and should handle the frequency ranges of 85 to 450hz.

I’m looking to get good near-field coverage of distances of up to 14’ away from the drivers.

I’m currently thinking of stacking 6 Adire Extermis as closely as possible into the 4’ height.

I’ll be using power tapering of the two outer speakers to maintain focus.

My biggest question is will this give me the kind of SPL at 12’ to 14’ to keep up with a 4’ by 12” ESL panel?

Are there other designs of line arrays with the extremis out there?

 

[FourDegrees11]

A pro sound midbass might be better suited to your needs. Something like the B&C 10PLB76 10" woofer.

http://www.partsexpress.com/pdf/294-659.pdf

You would only need 4 of them for your array.

 

[nate]

I think that the Extremis drivers would be really great. If you wanted you could push that 85HZ high pass down quite a ways and eliminate the need for a sub.

nate

 

[nate]

I would also not recommend power tapering of the woofers. Do some searches on line array theory and driver spacing. Read Griffin's line array white paper too. Most of the information that you need will be found there.

With the upper frequency that you are working with, you might be able to space the drivers out a little more and create a taller line source without any lobing. There are many benefits to this and at your listening distance, you will take advantage of many of them. You will be loading the room (with bass) vertically. This will help a great deal with bass nulls.

Sounds like a great project. Which stat panel are you using?
Nate

 

[planet10]

Typically ESL panels are even less efficient than the Extremis (and that is before factoring in 6 of them). As long as you supply them with a baffle that supports them down to their cutoff they will be fine i'd guess. If the ESL isn't power tapered i wouldn't bother doing that with the extremis.

And i assume you are multi-amping?

dave

 

[JonFo]

I think that the Extremis drivers would be really great. If you wanted you could push that 85HZ high pass down quite a ways and eliminate the need for a sub.

nate

Well, my IB sub goes to 10Hz pretty cleanly, and very , very loudly. A must to keep up with the big ESL L/R’s. Those are Martin Logan Monolith III’s.
The Sub stays, plus, it’s part of the room now

I would also not recommend power tapering of the woofers. Do some searches on line array theory and driver spacing. Read Griffin's line array white paper too. Most of the information that you need will be found there.

With the upper frequency that you are working with, you might be able to space the drivers out a little more and create a taller line source without any lobing. There are many benefits to this and at your listening distance, you will take advantage of many of them. You will be loading the room (with bass) vertically. This will help a great deal with bass nulls.

Sounds like a great project. Which stat panel are you using?
Nate

Thanks Nate, I read the Griffin Doc and many of the LA posting on this forum for a few weeks. I wondered about just how applicable any form of tapering might be at these frequencies. I was being cautious.
While I would like to have a longer array, I’m constrained by the height of the screen and the fact that this will mount to the top of the IB Sub manifold (my sub is the first ‘Outie’ inverse manifold IB). As you can see from the pics in my IB Build story, the array would sit on top of that Sub box, which is a 22” cube. So the top of the array is at 22+48+2 = 72”.

The stat panel comes from a Martin Logan SL-3, as will the associated electronics. The housing from the original SL-3 will be ‘modified’ (i.e. the woofer cut off) to build this.

Typically ESL panels are even less efficient than the Extremis (and that is before factoring in 6 of them). As long as you supply them with a baffle that supports them down to their cutoff they will be fine i'd guess. If the ESL isn't power tapered i wouldn't bother doing that with the extremis.

And i assume you are multi-amping?

dave

Yes, I’ll be using a DBX DriveRack 260 speaker processor in a 1x3 or 1 x4 config. My original concept for this involved a 1x4 crossover as follows:

Bass – 85Hz crossover to Infinite Baffle sub, 24db / octave LR
MidBass1 – 85Hz highpass, 24db / octave LR, 450 low-pass 12db / octave
MidBass2 – 85Hz highpass, 24db / octave LR, 250 low-pass 6db / octave, delay, limiters
Highs – 450Hz highpass, 12db /octave

However, based on what Nate said, it sounds like that’s overkill for these frequencies. I do have a 800 w (4 ohm) Sunfire amp channel dedicated to the ESL panel, and still have another 3x200 w (8 ohm) Sunfire amp channels to play with for this project. So splitting the array up is easy, but if not necessary, then I won’t.

Thanks for the feedback and keep it coming.

 

[JonFo]

Enclosure design

One more thing: Enclosure design

Adire’s guidelines are for roughly 9.5L per driver in a sealed alignment, therefore the line array box is a simple tower that measures 48”x10”x12.5” to yield an internal volume of roughly 60 Liters in a sealed alignment.
Using six internal braces for reinforcement, the box is pretty simple to construct. All sides are 1” MDF. As the speaker is never really visible, the finish will be flat black paint.

Any opinions on the use of sealed vs vented for this application?
Sealed would be simpler (and smaller).

Thanks,

 

[planet10]

I'd think you'd want to maintain the dipole as far down as possible (ie extremis in an open baffle)

dave

 

[JonFo]

I'd think you'd want to maintain the dipole as far down as possible (ie extremis in an open baffle)

dave

Dave, I’m, precisely trying to avoid dipoles at these frequencies due to rear wave cancellations. The ESL panel will readily play down to 250Hz, but the cancellations are severe and cause a noticeable suck-out.

I’m looking to get clean, high SPL’s from 85 to 500Hz out of the line array. Power is not a problem (I can do 2x200w into the array), so a sealed design seemed like the best way to achieve this.

Again, as the center channel, the music and vocal ranges are often concentrated there, and I’m looking for a strong mid-bass foundation that will keep up with the ESL and the IB sub in terms of clarity and ultimate SPL.

 

[JonFo]

Drawings for Array

Here is the rendering for this project.

Again, a sealed box with six series/ parallel connected Extremis:

Opinions or constructive criticism are all welcome.

 

[JonFo]

Rendering of proposal

Here is rendering of what the combined center speaker would look like:

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

It will sit on top of the IB sub in this picture (replacing the Logos center shown here):

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

This all sits behind a microperfed acoustically transparent screen.

 

[DeonC]

Hi Jon

I would strongly suggest that you build two woofer line-arrays, one for each side, especially at the frequencies that you will be driving then at.

Also, as much as I like the Extremis, I second the idea of maybe using pro mid-bass drivers, as I think that they will better match the electrostats ITO speed and dynamics.

Next, looking at the drawing of the proposed line-array it looks like you will be using open-baffle, but if the side-walls stretch so far back, you will be creating a short TL, not an open baffle, so be careful.

Consider this- if you make the baffle 9.12" wide, then the baffle-step point will be at 500Hz, your upper XO point. Considering this, I did a search on the Parts Express website for possible candidates. I settled on the following drivers:

SELENIUM 8PW3-SLF 8" DRIVER

STUDIO PRO WH8 8" WOOFER ACCORDIAN SURROUND 8 OHM

PYLE PRO PPA8 8" P.A. SPEAKER

EMINENCE ALPHA-8A 8" P.A. DRIVER

This is the results I got:

 

[DeonC]

Let me try again:

 

[DeonC]

Part 2:

 

[DeonC]

Part 3:

 

[DeonC]

Of these, the Pyle Pro PPA8 or the Studio Pro WH8 seem the be the best candidates, so I modelled them on their own, just differing the height that they are mounted on the baffle. Let's start with the Pyle Pro PPA8. I could only model up to a four-driver array, but the baffle height is speced for a six-driver array.

Part 1:

 

[DeonC]

Part 2:

 

[DeonC]

Part 3:

 

[DeonC]

Now the Studio Pro WH8. Note that the lower end will be a lot stronger due to there being 6 drivers rather than one, but it will still not be as powerful as the Pyle Pro PPA*.

Part 1:

 

[DeonC]

I hope this does not come out as a multiple post, because this one does not seem to want to go through, but let's try again.

Part 2: