does a line array need a sub?

[scone]

I am planning on building some speakers for a home audio system over winter break. This will be my first diy speaker project (ok so not exactly, my roomie and I converted our living room closet into a subwoofer, but that wasn't very complicated) and I'm still trying to figure out what I want to build.

I've seen plenty of designs for 2-way line arrays, and from what I've read about them they sound very attractive. However, would I need to build a subwoofer to go along with them, or can a 2-way line array produce an ample low end by itself (assuming a judicious choice of driver)?

Also, assuming I didn't build a sub, would I then have to build a 3-way line array instead so I could add a couple of small woofers to it? I assume this would be quite a bit more complicated since I posted earlier about building a 3-way speaker using 5 drivers and most people suggested I not do that because it would be hard to get it right.

Oh, the primary use of the audio system would be for listening to music. I will use it for movies as well, but I'm not particularly interested in building a serious HT system at this point in time. (I'm in college, there is absolutly no room to house such a thing)

-tony

[cjd]

Yes. Or no.

You can't extract response out of thin air (Ok, a horn might come close). Driver choice will answer your question. Not to mention what your target bass response is.

Me, I'm happy with good response to 40hz for many things. But enough of my music collection (lots of classical) includes judicious use of the pedal tones on the organ, which can go to ~16hz, such that I'm not happy with 40hz.

C

[5th element]

If you have one 5" driver in a box which produces and f3 of 50hz, 10 drivers in a box 10 times the volume tuned the same frequency will still only give you an f3 of 50hz.

So in other words yes you will still need a sub. My speakers extend to 20hz and you dont really miss bass from 20-40, if you have never had it before this is. If you are used to 20hz extension you miss it when its not there. BUT most music doesnt have anything down there anyway so its only noticable on tracks which have bass down that low.

[andrikos]

My line arrays use 8 18cm midwoofers on each side (Vifa PL18W09-04) and they definitely need a subwoofer (3 x Tempest 16ft^3 sealed).
Even though I chose a sealed design for my line arrays (for many reasons) I still get -3dB IN ROOM response of 38Hz. This makes them great for music but for HT a sub is absolutely essential...

[RJ]

{If you have one 5" driver in a box which produces and f3 of 50hz, 10 drivers in a box 10 times the volume tuned the same frequency will still only give you an f3 of 50hz.}

I get an F3 of 40 hz. on my line array of 10 5' woofers.
http://www.partsexpress.com/pe/showd...Number=295-330

At 30 hz. it's down by 8 db.
At 25 hz. it's down by 10 db

I think the Qtc. is about .59 Closed Box. Unstuffed, walls lined with foam over two sheets of roofing felt. Box is an 1 1/2" thick MDF.
Measured with a Radio Shack SPL meter without compensating for meter inaccuracy below 100 hz.
Awesome sound and very detailed. Using 6 Planar Tweeters;
http://www.partsexpress.com/pe/showd...Number=275-085

I've listened to Terminator 2 just lately. Very moving, very clear.
Metal to metal sounds like the shotgun barrel closing are very real.

I'm sold on line arrays. I'm building a WWWWMTM so I can compare the two.

[Timn8ter]

It depends on what you're listening to. Most music occurs above 40 Hz. If you're listening to pianos and guitars that usually fine. If you're listening to bass drums and pedal organs or synth bass 40 Hz is not going to cut it. I like how 5th Element put it. It's a common misconception that if you keep adding drivers somehow the system magically develops more bass.

[RJ]

Really nice job andrikos. I've got 2 brothers in the Marana Area.
18 cm. = 7 1/4" Woof's. Is that about right????
What are you amping with theses babies. I'm using 300 watts/channel.
Oh, yeah. A heap of thanks on your SPL chart. Hope you don't mind if I print a copy for me.....
L8'er Rudy

[RJ]

{Also, assuming I didn't build a sub, would I then have to build a 3-way line array instead so I could add a couple of small woofers to it? I assume this would be quite a bit more complicated since I posted earlier about building a 3-way speaker using 5 drivers and most people suggested I not do that because it would be hard to get it right.}

A two way line array with a sub would make it a 2.1, not a three way.
You could build a line array with 4 1/2" woofs in a closed box. The 4 1/2" would have a natural roll-off about 150 hz. You could than adjust the sub to roll-off at about 125 hz. The sub would have to have a plate amp to accomplish this. It would be a whole lot better than trying to do it with a passive crossover.
It's - do you want musical bass (2-way) or theatrical, floor shaking bass (2.1) ????

[scone]

I know lots of people have special subwoofer line outs on their recievers so they can plug directly in to the sub amp. Would it be a problem if I had a subwoofer amp in parallel with the 2-channel amp driving the line arrays? I only have two analogue channels to play with (the output of a cd-player) and it would have to be plugged directly into both amps. I would assume that this is not a problem, but I only have a vague idea of how amps really work so I don't trust myself.

-tony

[RJ]

"Bass is super-clean and well-extended. In room response -3db levels reach down into the mid 20's."

"It has been noted that many Alpha LS owners are using these speakers in somewhat smaller rooms than they were designed to be used in. In most small to meduim sized rooms they do tend to load the room with bottom end re-inforcement. For this reason a bass management system has been designed to allow the end user to tailor the low end response for their room."

Quotes taken from;
http://www.gr-research.com/AlphaLS/Alpha.htm

Hope they don't mind....

I'll find out soon enough when I take these speakers to my son's house (small sized room).... The speakers right now are in my screened porch. Where I'm doing the SPL measurements.

As for the reciever. I don't have one with sub-out, but I've read on numerous posts other people have used it that way.

I think there was a Jurassic Park movie where t-rex was felt walking through the forest before you could see him.
I'm trying to find which one now. I'd like to see if my line-array could pick that up!!!!!