My intial experiments w/ OB bass

drphoto · « **on:** 13 Mar 2009, 05:03 pm »

I finally got the GR version of the Rythmik OB servo subs up and running I have 2 of them, one each in a simple L shaped baffle postitioned near the monitor stands.(Similar to ones St. Louis Bob showed in a previous post)

My initial impression is they get the really low frequencies fine. It's the first time I've heard the opening track on Sting's "Brand New Day" sound right. (some nearly subsonic stuff there)

However, I'm not really getting much of the low-mid/upper bass punch I was hoping for. Is it that 2 drivers are just not enough? I've noticed most of the OB setups I've seen have at least four.

If I get another pair, do I simply parallel them off the exiting drivers?

So far it sounds best w/ the lest one aimed at the listener, and the right one turned 90º to the left so that it fires across the room.

OH, BTW: I've got the crossover on the Rythmik amp set @ 100hz. Right now the baffles are just sitting on the floor. I intend to add spikes to the bases, which might help tighten things up a bit.

I'm going to takes some pics an post them over the weekend.

drphoto · « **Reply #1 on:** 13 Mar 2009, 05:24 pm »

Just pulled out my old Odyssey test tones CD and did a bit a fiddling w/ the phase. Definite improvement in punch.

richidoo · « **Reply #2 on:** 13 Mar 2009, 05:25 pm »

If the lowest notes sound good and loud enough, then you have enough driver area for your listening style.

I think the sub is out of phase within the crossover region. You can fix it with the phase control on the sub.
http://www.avguide.com/forums/subwoofer-placement-and-phase

OB bass is easier on room modes, but that could still be a part of the problem. See if moving things around or even walking around helps clean it up. Getting them away from the front wall is pretty important for OB because your are more susceptible to SBIR. When I had Quad 2905s they wanted to be out 8 feet, any further back and I could hear them tighten up. My wife didn't like those speakers.

One other thing, you main speakers may not play as cleanly at the lower freqs as the subs. You might need a high pass filter on them if they are muddying up the subs. Experiment moving the crossover frequency around too. Good luck. Thanks for the quick review, I'm thinking about getting them too.
Rich

EDIT I see you already figured out the phase!

Try the Harley trick, it works pretty good.

drphoto · « **Reply #3 on:** 14 Mar 2009, 04:32 am »

Oh yeah.....this is starting to get good now!

I've gotta get the baffles braced, painted and install the spikes.

Phase seemed to have been the issue.

Some day when I have a spare $400 laying around I'd like to add another pair of drivers for when I want to rock Metallica and the like, but I'm really diggin' the servo controlled OB sound.

Just wondering are there any others running OB bass w/ conventional monitors like I am? I'd love to hear these subs w/ Maggies.

panomaniac · « **Reply #4 on:** 14 Mar 2009, 06:43 am »

Photos! We want photos!

gainphile2 · « **Reply #5 on:** 14 Mar 2009, 09:03 am »

I have yet to hear OB with great "Punch".

Seems like it's not in their nature. SL said:

"Bass from box speakers has more "punch" than from open baffle speakers, but is less airy."

ttan98 · « **Reply #6 on:** 14 Mar 2009, 12:40 pm »

Quote from: gainphile2 on 14 Mar 2009, 09:03 am

I have yet to hear OB with great "Punch".

Seems like it's not in their nature. SL said:

"Bass from box speakers has more "punch" than from open baffle speakers, but is less airy."

If you need/want more punch you will require multiple open baffle drivers, like what Magnetar is doing, at least 4 or even 8 drivers per side and drive them with high powered amplifiers. You will get both punch and slam. Room size plays an important role.

Telstar · « **Reply #7 on:** 14 Mar 2009, 09:50 pm »

I agree, for big rooms multiple woofers are the way to go.

drphoto · « **Reply #8 on:** 15 Mar 2009, 07:00 pm »

Well, I don't if it's a combination of finally getting the phase and crossover correct plus some 'break in' of the drivers, but these sound amazing. I'm seriously diggin' what I'm getting now. Thanks to St. Louis Bob for convincing me the simple, cheap L shaped baffles would do the trick.

I'd love to get 2 more drivers down the road, but I have no beefs at all with what I'm getting now.

Hats off to Danny, and the folks at Rythmik for putting out such an awesome product.

I uploaded a couple of pics to my album and tried a test post, but they display tiny, even though they're 2 MB files (once expanded) What's the trick here? I always seem to have this problem when trying to display images.

cheers,

joe

lonewolfny42 · « **Reply #9 on:** 15 Mar 2009, 07:08 pm »

Here you go....

zybar · « **Reply #10 on:** 15 Mar 2009, 07:11 pm »

Nicely done!

I am very close to ordering 4 of the drivers and building two OB subs per the plans on Danny's website.

I will be using them in a dedicated HT system where I can be very flexible with placement.

George

drphoto · « **Reply #11 on:** 16 Mar 2009, 01:44 am »

Thanks for the help w/ the photos Chris. Sometime this week, I'm going to cut a bit off the length of the base plate. I think 20" instead of 24" should look better. I'll then use that scrap to make some 'footers' where I'll install some spikes. I'm going to brace the baffles w/ a couple of pieces of 1" dowel. Then I'll seal 'em and finish w/ black truck bed liner which will hopefully be a reasonable match for the Merlins.

Zybar, I'd be very curious to hear the difference using the W box (which what I'm assuming you're going to do)

Believe me, these sound pretty great w/ just this simple arrangement.

dvenardos · « **Reply #12 on:** 16 Mar 2009, 02:35 am »

Hey, I would like to use these but can't get 3' from the rear wall unless I drop them from the ceiling. You guys have any idea on how to design a ceiling drop for these (kind of like a ceiling fan)?

edit: found something
http://www.chiefmfg.com/productdetail.aspx?MountID=34
I have cross posted from here:
http://www.audiocircle.com/index.php?topic=65383

ttan98 · « **Reply #13 on:** 16 Mar 2009, 10:47 pm »

This OB will give you slam and punch.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=131941

but you really need a big room.

drphoto · « **Reply #14 on:** 24 Mar 2009, 08:28 pm »

Would I get more impact if I were to put the drivers in the W box as shown on GR's website? Is that rear facing woofer wired in or out of phase? Maybe I just need 2 more drivers period. (2 per side)

The current setup works very well at low volumes, but if I turn it up just above conversation level, the drivers start maxing out.

opnly bafld · « **Reply #15 on:** 24 Mar 2009, 09:05 pm »

Quote from: drphoto on 24 Mar 2009, 08:28 pm

Would I get more impact if I were to put the drivers in the W box as shown on GR's website? Is that rear facing woofer wired in or out of phase? Maybe I just need 2 more drivers period. (2 per side)

Yes, or you can put each driver in a 12" deep H baffle (just add sides and a top to what you now have).
Rear facing driver out of phase in W box.
2 drivers good, 4 drivers better, but I think a lot of your problem is cancellation from a small baffle.

Lin

drphoto · « **Reply #16 on:** 24 Mar 2009, 09:19 pm »

So what I need is a box.....that is open in the back?

Thanks for your feed back on this.

opnly bafld · « **Reply #17 on:** 24 Mar 2009, 09:28 pm »

Quote from: drphoto on 24 Mar 2009, 09:19 pm

So what I need is a box.....that is open in the back?

Thanks for your feed back on this.

Open in the front and in the back, just like looking down on an H (driver mounted here - ) with a top and a bottom.
H and W baffles are basically the same, a W saves space with multiple drivers.

Lin

drphoto · « **Reply #18 on:** 24 Mar 2009, 11:07 pm »

Ok....and feel free to laugh.....I actually took the driver shipping boxes and wrapped them around the L frames to make an "H". It works! Much 'punchier'. However, cardboard does have some crazy resonance!

I've meanwhile contacted Eric about some proper enclosures. I had no idea about this cancellation thing. Somehow I thought these OB speakers were made to overcome that. I mean I knew it happened w/ "regular" drivers, which is why people put them in boxes.

I feel like such an idiot sometimes.

I could post some pics if you want to see the silliness.

dweekie · « **Reply #19 on:** 25 Mar 2009, 12:35 am »

Shipping boxes are some of the best test baffles. Plenty of people have used them in the past, so you're not alone in that department

If you can find some larger boxes (or wood) lying around, I would try out a bigger flat baffle and compare it to the U/H/W/etc aa