[jrebman]

Now that I have my V-2 kit sitting in boxes in the living room, and based on what I heard at RMAF last year, I have an idea brewing that I have some questions about, but basically it's a potential project to integrate a OB sub into  an existing speaker by adding a box underneath in a similar configuration to the v series speakers.

Actually, I suppose the first question is whether this is necessary or not, or can the OB sub be placed anywhere else and get the same results?

In this application I will be limited to 8" or maybe a 10" driver or drivers per side, so another question would be if there's a suitable 8 ob sub driver available that will work acceptably with the SA-1 amp, and likewise, would thee hawthorne augie 10" also work with this amp?

A couple more basic questions:

- does the direction the driver is pointing in make any real difference in an OB design -- in other words, would it be ok to point it so that the cone is pointing left and right insted of foreward and backward?  Also, is the 3 foot rule also applicable to subs?

That should get me started and/or give me enough information as to whether this is even worth pursuing any further.

Thanks,

Jim

[TRADERXFAN]

The direction is very important. The sides of the sub are in nulls. So dead on pointed towards the listener is best, and as you stray from that you are going to lose output.

The location is not required to be right next to the mains (unless you are using it up into the "directional" perception range said to be around >80hz)

3 foot rule is definitely applicable to the subs... and that is actually a minimum.

[nickd]

The location of the sub is important depending on crossover slope and frequency, upper bass harmonics will smear the soundstage if placed too far from the "monitor"

I think Danny is working on a 8" OB servo sub. They will be more expensive than the drivers and amp you mentioned but worth the extra dollars. The servo is a big leap foward in OB sub design. it is almost electrostat or planar fast with conventional driver impact. But 3' from the wall is the price we have to pay for life like kick drum.

You will be happy with the V-2 until the 8" OB subs come to market. then you'll get the upgrade bug again.

[jrebman]

Thanks, gentlemen.  Unfortunately this pretty much kills my idea since 3 feet away from a wall in this room is not really practical.

Only other possible solution may be if anybody knows of a decent 8" non-ob sub, or if the servo sub Danny is developing will also work in a sealed or ported box, though sealed is my preference for now.

Thanks,

Jim

[django11]

I didn't even know my ob sub should be 3 feet from the wall.  I was really happy with it ... until I read this thread...

[persisting1]

I didn't even know my ob sub should be 3 feet from the wall.  I was really happy with it ... until I read this thread...

If they sound good to you and you like them, then don't worry 

[TRADERXFAN]

I didn't even know my ob sub should be 3 feet from the wall.  I was really happy with it ... until I read this thread...

Well the good news is experimenting with moving it out can't hurt... and might be a pleasant surprise. I shouldn't have said minimum, what I meant was it can be better, farther away, than just 3 feet.

How close did you have it? Just to make sure people understand. We are talking about rear wall. Due to the nulls it can be up against alongside a wall. Linkwitz actually recommended that.

[TRADERXFAN]

Thanks, gentlemen.  Unfortunately this pretty much kills my idea since 3 feet away from a wall in this room is not really practical.

Only other possible solution may be if anybody knows of a decent 8" non-ob sub, or if the servo sub Danny is developing will also work in a sealed or ported box, though sealed is my preference for now.

Thanks,

Jim

You know Danny does have a the sealed servo 12" driver, correct? That is only a 1.5 cubic foot box.  I have one of those too and it is great.  Still like the dual ob subs better on music.

[HT cOz]

3 ft from the back wall. The sides are nulls so they don't matter as much??? 

I can tell you somewhat unconventional placement works best in my room. Although I have 6" of Rockwool and 2" acoustical foam on the walls right next to my speakers. So unconventional rules the day.

[Tyson]

Sealed, NOT ported is the way to go, IMO.  Sealed subs match room gain much better than ported ones do.  Plus, subjectively, they just sound better.  Danny said the 8 inch servo driver is already in production... Personally I'd try to use 2, in different locations, to smooth out the room response even more.

[TRADERXFAN]

Here is a link to some of Linkwitz's comments about dipoles and placement...
http://www.linkwitzlab.com/faq.htm#Q30

[jrebman]

Sorry for not responding sooner -- had to go to my nephew's b-day party yesterday.

Anyway, lots of interesting comments and experiences to ponder here.  Maybe a somewhat better explanatiion of what I plan to try is in order...  So, the main speaker has a bottom that is approx 9" - 10" wide and about 15" deep.  I intended to steal Danny's idea of the 45 degree angled sub driver (only 1 though in a frame of some sort built onto the bottom of the main speaker such that the front is open and the dri ver edge close to the front opening.  I'd also probably have the drivers angled opposite to each other from one speaker to the next and then by swapping positions of the two speakers, you could get more direct bass or more "oblique" (though I have no idea if this will matter aat all at these frequecies (probably 100 hz or lower and below).  The front of the speakers will be approximately 2 feet out from the front wall, and there is already a heavy, coarse wool/cotton/jute rug/wall hanging behind the speakers, but I'd probably also add diffuser panels bewlow this.

So, in a sense, with the angled drivers, the extra distance to the wall, perpendicular to the plane of the sub driver, would be 2.8 feet approximately.  Plus there may be some wiggle room for pulling it out a bit further or back, for tuning.

So, seeing what some have said here, I'm a bit more encouraged that this would work, but I have to say that I don't fully understand what happens when you angle the sub dri ver and/or if you need two of them perpendicular to each other in the same enclosure, or if two of them perpendicular in different cabinets and approximately 6 feet apart, will be sufficient.

Danny, any comments?

Thanks so far to everybody for their thoughts and links. I'm taking it all in.  The good thing here is that I can easily built the main speakers now and then build the box/riser for the subs later on and make them so they bolt to the main cabinets.  The other benefit of this is that the driver in the main speaker will be at a very good height when on the riser.

Thanks,

Jim

[TRADERXFAN]

The "front" is the opening to the enclosure frame  (could be a flat baffle, but I think we are talking about something like a "W" frame,  "H" frame, etc. ) around the woofer. The depth of that enclosure that separates the front of the wave from the rear radiating wave, relative to the frequency, and that length, is going to be what boosts the low end by putting it in this frame instead of just on a baffle. The way this opening is facing is the directional component. The orientation of the driver doesn't matter too much. A ripole is completely sideways, for example. The polarity must be that both speakers are pushing forward and backward at the same time in the different speakers. It should not be detectable which way you oriented the driver in the baffle.

If you have the output into the >80hz you will want to co-locate this with the mains. However, below that the wavelengths are so long they will be essentially omnidirectional in a normal residential room.

The output on the low end will be about a 1/4 of what a boxed driver will due.  Also the upper end will have a rising output, up until some frequency. Danny has a shelving filter built into the amps, I believe, to help correct this behavior.  You usually are going to need multiple subwoofer drivers, per side, in order to keep up with a normal sensitivity mains speaker.  This depends on the displacement area of the driver.  That is why he uses 2 in each speaker for the v series. If you get an 8" servo you are going to need more, but the baffle can be thinner to match the upper section.

How big of a room? How close will you be to the speakers?

[TRADERXFAN]

One other thought; I've been using "glop," (Aleen's glue mixed with sand) to dampen the rear of the open baffle sub panels and followed Danny's suggestion on one of the forum pages by adding vinyl floor tile to the front.  No particular reason for using different methods for front and rear just playing around with the two methods.  I used 3/4" sandeply from Home Depot.  It's lighter than 3/4" birch so I have no doubt that the damping is important for the plywood.  I also have some spikes that I'll use as well.

Is Aleens glue non-hardening?  That is what you need for damping. Some types of liquid nails work for this too. I think it is the polyurethanes.  Ideally this would be used between panels for constrained layer damping.

-Or are you just adding mass?

[Poultrygeist]

I'm loving the sound I get from these OB H frame bass speakers.

[jrebman]

Tony,

Thanks for more good info.  The driver in question will be a Lowther DX-55, so fairly sensitive.  The room is 10.5 x 16.5 wit a 3' x 6' closet out of one corner, and with a long wall setup offset into the area where the closet is not in the way.  Listening distance is approx 7 feet.

I can run the drivers down to something like 45-50 hz if need be, but I'd rather they be about an octave above that if possible, so 80 is probably a good compromise.

Also, I'm pretty new to subs, certainly OB ones, and I honestly have no idea of what an H or W frame is or what it looks like.  I'd look it up, but pictures don't do me any good.

I'm sure all of this will make more sense when I head over to Ruben's place and pick up my V-2s when he's done with them.

Also, I obviously don't do any HT stuff, this is strictly 2-channel music in my man cave and looking to fill in the bottom end a bit and add more dynamic punch in the process.  In a lot of ways, this will be a similar concept to the v-series speakers.

[TRADERXFAN]

To help you understand the W and H types, I will attempt to describe them in words. However when you go to Reubens he can probably explain the differences from what you are getting in your v-2s.

For the W frame, imagine the drivers start on a flat baffle, one directly below the other. Then imagine if the bottom of the top driver, and the top of the bottom driver were on a hinge. Then you were able to push those edges of the drivers inward about 10" from where then started.  The design is for a 90 degree angle between them. Then to support them you attach panels on the sides. The total height would be decreased. Now there is an air space "pocket" in front of the drivers, in the middle. Also on the back there is another pocket of air near the top and bottom. These pockets are equal in volume, relative to the front to back of this open faced enclosure.

The H frame is similar in that there are 2 vertically aligned drivers on a baffle that is set back into an open faced "box".  So there is equal air pocket in front of the driver and behind again, like above. There is a divider between the top and bottom drivers. And it is just a bit taller now because he has shifted the mounting point closer together, vertically than it woud be possible on a flat baffle.

The key is that the acoustic centers remain in the same vertical plane. If you change that, then I think that would be called a bipole and it gives a very different pattern of output and cancelations.

Danny has modified this 2nd concept of the H frame in the V-2 by bringing one side of each driver forward and the other side back, in order to narrow the width. If you had a top view, it would form an X.

Danny has one of the drivers reversed in both of these designs, in order to have the weight distribution of the magnets balanced, and to offset some of the driver motion (as I understand, could be mistaken).

I think that your room is a good sized space for this, except the depth is a challenge.  This rear wall distance combined with your listening distance would put you right up against the wall for your listening position. Do you have absorption there, behind you?

If you can keep this ob sub below about 80hz that gives you more placement freedom. 
Would you be putting a high pass filter on the mains, or doing something to the enclosure design?   

[jrebman]

Tony,

Thanks, that makes much more sense, but I'll still have to ponder it a bit, though I get the general idea.

As for the room, there are other complicating factors such as location of doors and closets, and the fact that my desk/workbench is in there too.  I have a big La-z-Bioy recliner covered with textured fabric that goes up to the top of my head, and then another 6 or so inches behind that before the wall, which is currently untreated, but which I ave some gik panels and some gridfusers for, or I may just get another similar wall hanging to the one I have on the front wall, which made a huge difference.

As for how ultimately I will work the crossovers/amplification, I don't know, but this system is one source -- mac mini/tranquility SE and puremusic, and I may look into configuring a second dac and using the multi-channel capabilities in PM to do the crossing over and active parameter adjustments.  I've not tried this yet, so I'm not sure how it will effect sonics, but as the system is now, even just turning off the dithered volume control in PM makes a noticeable difference so I'm not sure this will ultimately be the way to go.  Ideally, I'd ilike to offload the lower bass from the lowther to get more mileage out of the 2a3 monos, but again, I'm not sure that will be necessary/worth it.  It's an experiment of sorts and thus will require a lot of futzing around with various approaches and tuning until I get it dialed in.

With my tonian speakers, they sounded great with just rough placement, but after a couple of weeks of fine tuning, I was treated to some of the best sound I've ever experienced where the speakers were absolutely invisible and there was a soundstage that was huge but realistic in proportion.  And given that the speakers were only about 7 inches from the front wall, that was not what I would have expected.

Anyway, thanks again, and I'll just keep opondering this -- though the flat packs for the cabinets for the lowthers ar supposed to arrive on monday, so it won't be too long before I get to start trying some things out as well as racking up some hours on the drivers.

-- Jim

[jrebman]

Ok, now don't take this too seriously folks, but did the mention of lowther and 2a3 send all you guys away .

I realize it's not the typical thing most of you would give a second thought but I am building a V-2, doesn't that redeem me in some small measure?

Just kidding, but I find it somewhat amusing nonetheless.

-- Jim

[TRADERXFAN]

From your last post, I thought you were just going to be reviewing your options... was there some more info you were looking for?