DIY Open Baffle Mid Bass Line Array

[IWalker]

Well, here it is...pictures only to begin, as the gear to test them out (extra amps, external crossover) isn't here as of yet. But, I think they turned out fairly well. They look good (to me at least) from the front, but a tad sloppy from the back (notice how there are no pictures from the back yet ) I'll post impressions, and try to get a second opinion from jtwrace once I get all the gear.

I also need to build some stands to get the arrays up to the height of the QuestZ panels!

 

[Dominick22]

Can you post a link to the drivers that you chose to use?

Looks like a clean job from the front!

Dominick

 

[IWalker]

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-374

There you go. I have them wired to be a 6 ohm load per speaker. I'll post pictures of the wiring tonight. I'm very happy with how the front turned out. I was planning all along to just go with a flat black, but I very much like the way the colors worked out. A little more modern looking. It's hard to tell from the picture I took..but the phase plugs make these things look really cool.

 

[Jeff Zaret]

Personally,
I like the teddy bear.

The do look nice and I am sure they will sound and blend exactly how you had planned.

Jeff

 

[jtwrace]

I'm in overload not only looking forward to hearing these but waiting for my Summits

 

[IWalker]

These things are 4ft tall and weigh an easy 50lbs...but are still dwarfed by the Quests! I love it. Should only be another day or two before I can do some prelim testing (the crossover should be arriving)

 

[IWalker]

Here's a picture of them from the side. Tried to limit the back wave reflections as much as possible without reducing strength.

 

[JonFo]

Looking good Iain!

Now, make a mount and get them parallel to the panels for a more balanced presentation.

When will the measuring rig be in?

 

[IWalker]

Take a look at my member system...I have em up off the ground.

The crossover has only XLR inputs, so I ordered some XLR/rca adapters...

Once those come in, I'm going to borrow a second amp from jtwrace, and can test from 100Hz and up...or I can buy another pro-amp or sub and test the whole range. I'm thinking the funds to buy the pro-amp or sub is going to be the main limitation on testing. I don't really want to buy another pro-amp if I'm going to eventually get a sub, but the sub I want is going to be more expensive...blah blah....

I did already test JUST the panel. It's definitely not completely flat, but a few filters in place, I managed to get it +- 2 db across the board with iirc 1/12 octave smoothing.

I'll try to get the 100HZ+ measurements (ML panel + array) done before Xmas, and get them up. No telling on when I can actually integrate it all!

I still have it in my head that I may have to build a closed box for this, if I don't get the "punch" I'm aiming for in the lower midrange/upper bass even with EQ. I have a feeling that some of that may have to do with the way dipolar designs don't change the pressure in a room (velocity source) as opposed to closed box systems which do change it (pressure source) Only time will tell.

 

[JonFo]

... The crossover has only XLR inputs, so I ordered some XLR/rca adapters...

Isn't that what the Art CleanBox does for you?
It has RCA in and XLR outs that only match the connector types, but does the level adjustment between pro-sound and Consumer levels.
You still need XLR to XLR between the Clean box, the Crossover / EQ and then again to the Pro-amp.

... Once those come in, I'm going to borrow a second amp from jtwrace, and can test from 100Hz and up...or I can buy another pro-amp or sub and test the whole range. I'm thinking the funds to buy the pro-amp or sub is going to be the main limitation on testing. I don't really want to buy another pro-amp if I'm going to eventually get a sub, but the sub I want is going to be more expensive...blah blah.....

Yeah, the current Crown 602 should do fine powering the line array once you upgrade the amps for the panels. But a used pro-sound amp could tide you over until then. Re-sale on a used amp is generally not as big a hit to the wallet as new unit.

...I did already test JUST the panel. It's definitely not completely flat, but a few filters in place, I managed to get it +- 2 db across the board with iirc 1/12 octave smoothing.

I'll try to get the 100HZ+ measurements (ML panel + array) done before Xmas, and get them up. No telling on when I can actually integrate it all!.

It is definitely worth the time to measure, tweak, measure, tweak, …. Ad-infinitum.
I find it’s also a great way to learn what works and what does not. Sometimes one tries things that go the wrong way (like certain crossover types or slopes) and then have to go back to that fork in the road and try another path.

... I still have it in my head that I may have to build a closed box for this, if I don't get the "punch" I'm aiming for in the lower midrange/upper bass even with EQ. I have a feeling that some of that may have to do with the way dipolar designs don't change the pressure in a room (velocity source) as opposed to closed box systems which do change it (pressure source) Only time will tell.

It’s been my thought that a dipole was going to be a challenge in terms of ‘slam’ or ‘punch’, as energizing 160 Hz at >100 DB SPL in an average room requires moving some air. And more important than what’s happening at 1m is what’s happening in-room at the listening position. A dipole will engage many more room effects, and in some rooms they might work, but other they will not. So make sure you measure there. Of course, near-field on a line array is pretty large, so anything under 2m for measurements is probably too close.
It should be easy to build an enclosure to turn the LA into a closed system and test that on one of the units. Nothing like direct comparisons of your own LA in your own room as either a dipole or a closed box to tell you which is right for you.

 

[IWalker]

Finally an update!

JonFo, thanks as always for the great advice.

I finally got in everything (an amp on loan), all the appropriate cords, etc. and set this up. I have it crossed at just 250 Hz right now, and down low at 80Hz. (which until I get a sub, means the low end is lacking). I measured FR using A computer based program with my External Sound Card (M-Audio Sonica) and a RatShack Meter. I adjusted the EQ in the crossover box to make it flat down to 80Hz. (I also eq'd the panels a little bit...but decided against that after the fact, so removed it...I may go back and do it later, but I'm going to leave it alone for now.)

My impressions (besides the DEEP bass lacking a little bit) is that I do get that extra punch...a little "kick" in the chest that I was looking for, and that really fills out a lot of the music I used to not listen to on my logans, and gives it a lot more substance. At the same time, it doesn't sound sloppy at all to me. I was going to go the closed route, as I figured it would better achieve my goals (after a prelim test) but I just don't know how I could be happier with the results than I am now, and would hate to take the time/money/energy to change it, just to find I like how it is now better.

I will probably do that at some point, but it's WAY back on the priority list now.

You're right about dipoles rolling off in the deep bass, and I'm not going to get nearly the output below drop off point that you'll get with your extremis (jealous of those drivers, btw...always wanted to build something with them) but with 6 drivers, 91spl/w/1m and 60w per driver handling, I am pretty sure I'll get way beyond where I want to be (as long as I don't try to cross lower than 80Hz) especially since I don't like listening at particularly loud levels.

I am planning to build a rythmik audio servo 12 kit to match in the low bass, when I get around to it. (2 of em eventually)

Also VERY jealous of your IB sub. That's eventually the direction I want to go...but I don't think my neighbors above or below would like if I cut a hole in their floor/ceiling and vented my IB into their living room!! Even once I get a house...there's no promise that I'll have a set up that will allow for IB setup. That's why they call it a dream, though...right?

So, "final" word on them...I'm VERY happy! Will continue to EQ (and need to get real stands for them) but am at the point I can just sit back and relax too! Finally!!

 

[Tj Bassi]

Iwalker-
Any improvements since your last post? It would be great to keep this thread going, at least from a reference standpoint, since this is a project that others might want to take on.
Are the drivers you chose inherently 'dipolar' or specific to open baffle use? It was my understanding (probably incorrect) that if you allow the rear waves from a driver to meet at the front, the output would be sonically nulled, which is why a bare speaker driver playing on the benchtop makes nowheres the volume it does when it is mounted in an enclosure.

Tj

 

[IWalker]

The main update to this is the addition of the rythmik sub I just finished. it crosses over at just the right point where the arrays start dropping off, and mates very well. The whole system covers the bass range beautifully, and creates the punch I was looking for all along.

Yes, the rear waves do cancel the front wave on the sides, and as the wavelength lengthens, they begin to cancel in the front as well (that is the point of creating the baffle...to seperate the waves). So, generally to play low bass you need to have a GIANT baffle/wings. I chose instead to eq the lower end a little bit to make up for the drop off, to keep the size manageable.

I have no sealed back array to compare the sound to, but am very happy with my results. I also tend to trust JonFo's experience more than my own, and he seems happy with his closed box arrays, so it's really up to what you want to do.

The drivers aren't designed specifically for OB application. In fact, they probably aren't ideal. I think a higher QTS is preferable from waht I've read, but I had already purchased the drivers at that point...and I'm happy with the result (especially at the price point) ... but that could be another argument for a closed box array.