My new & improved OB speaker

[audiophile36]

Hello I have been running my OB speakers with a single 4.5" fostex 126e without the help of a woofer for a while now because I didn't know how to cut large holes and quite frankly I liked the sound. To cut the holes for my Fostex I simply used a 4" hole cutter,but they only go up to 6" and I had no idea how to "manually" cut large holes...until I got the help of a fellow member who explained to me how to cut larger holes with my jig saw,I now have added an 8" helper woofer to fill in the bass a little.The woofer is salvaged from a pair of old Realistic Nova speakers,the magnet isn't that big so I figured it would do ok in OB. I haven't designed a crossover for them yet,but even without one they sound wonderful.I'm going to take what I learned with these and go OB crazy with larger woofers and different full range drivers...I'll keep everybody posted with pics!

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[Kensai]

Good, I was wondering if anyone had managed to get you some help.

OB all the way, and even with decent sized ones like that and maybe a bit of EQ, 8"ers are really just going to be mid bass drivers in OB. This will be something for you to play with for some time to come, and since you've started with decent FR drivers, it'll pretty much always sound good while you're at it.

Kensai

 

[audiophile36]

Good, I was wondering if anyone had managed to get you some help.

OB all the way, and even with decent sized ones like that and maybe a bit of EQ, 8"ers are really just going to be mid bass drivers in OB. This will be something for you to play with for some time to come, and since you've started with decent FR drivers, it'll pretty much always sound good while you're at it.

Kensai

Thank's Kensai,

You are correct they still don't have super deep bass,but the bass they reproduce is great and actually has some nice impact.I could live with the bass from these 8 inchers for a long time with the music I listen too so I know a 12" or 15" would be icing on the cake.

 

[davidallancole]

Thats what I found too running 8s on my wider baffles. They are not the end all be all, but gives an idea of what is possible.

 

[peterbrorsson]

Hi audiophile36!

Interesting that you have blinds behind your speakers. This is something I have been thinking of, even if there are no windows behind. If larger wooden blinds are hung on the walls behind OB's, there should be some diffusion effect, so a closer positioning to the back wall would be possible?

Wadda'ya think experts?

Peter

 

[audiophile36]

Hi audiophile36!

Interesting that you have blinds behind your speakers. This is something I have been thinking of, even if there are no windows behind. If larger wooden blinds are hung on the walls behind OB's, there should be some diffusion effect, so a closer positioning to the back wall would be possible?

Wadda'ya think experts?

Peter

You are correct about the blinds...I had curtains behind the speakers but the absorbed to much sound,while the blinds diffuse the sound better.

 

[audiophile36]

back of OB speakers

here is the back of the speakers showing the neat wiring and binding posts.You know OB speakers sound better with neat wiring...LOL.

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[planet10]

Re: back of OB speakers

here is the back of the speakers

If you open up the cutouts at the back it should improve things.

dave

 

[Tubamark]

Hi audiophile36!

Interesting that you have blinds behind your speakers. This is something I have been thinking of, even if there are no windows behind. If larger wooden blinds are hung on the walls behind OB's, there should be some diffusion effect, so a closer positioning to the back wall would be possible?

Wadda'ya think experts?

Peter

The rear distance requirement for dipoles has little to do with the nature of the rear wall; it has to do with creating the needed delay of that reflection. 3 feet (6 feet round trip from speaker to wall and back past the speaker again, on to listener) delays the rear reflection (at the listener seat) by about 6.75 miliseconds. It seems that lesser delays result in the brain integrating the reflection with the original/direct sound . . . sound at listening position is percieved as smeared across time.

If sufficient delay of the reflection exists, the brain says "ah-ha"- clear direct signal, and the reflection adds ambience and increased volume/SPL. Any diffusion is icing on the cake, but can't replace the needed delay. Only an anechoic front wall can do that.

Tons of writings and research out there on this topic. Maybe start with LinkwitzLab.com, as super-relevant to dipoles.

-- Mark

 

[peterbrorsson]

The rear distance requirement for dipoles has little to do with the nature of the rear wall; it has to do with creating the needed delay of that reflection. 3 feet (6 feet round trip from speaker to wall and back past the speaker again, on to listener) delays the rear reflection (at the listener seat) by about 6.75 miliseconds. It seems that lesser delays result in the brain integrating the reflection with the original/direct sound . . . sound at listening position is percieved as smeared across time.

If sufficient delay of the reflection exists, the brain says "ah-ha"- clear direct signal, and the reflection adds ambience and increased volume/SPL. Any diffusion is icing on the cake, but can't replace the needed delay. Only an anechoic front wall can do that.

Tons of writings and research out there on this topic. Maybe start with LinkwitzLab.com, as super-relevant to dipoles.

-- Mark

Hello Mark and audiophile36!
Thanks for the replies!

Mark, what I'm thinking is, if blinds are hung a certain distance from back wall, blades angled some degrees, there would be some benefits due to that the sound will be "bouncing" between wall and blinds. Thus causing a delay. Hope you understand my unscientific way of explanation. I shall read more of the links you provided.

audiophile, I've tested my fullrangers on an OB, wish I hadn't done that, now I hear just the boxes in my normal speakers.
The reason I ask about the blinds, is that my room, although large, do not permit OB's one meter from walls.

What the heck, I will try it later in spring!

Regards
Peter

 

[steve shiels]

The reason I ask about the blinds, is that my room, although large, do not permit OB's one meter from walls.

I'm am in the same situation

my baffles sit angled, about 18" from the back wall
i have found that damping the back of the baffle with some thick carpet helps to stop refections and removes any boxy sound.

this does nothing to help the distance from the back wave reflection, but careful angling of the speakers can help, but the listening position then becomes critical...no easy answer

it was sugested to me last week that a circular externally damped pipe, stood upright behind the drivers would break up the refections,
thats something i will be trying out in the next few weeks.
this was to help the sound stage, which is by no means bad
but not quite up to the sweet spot which a pair of well set up quad esl57s can provide...

steve

 

[Scottmoose]

Perhaps not mate, but they're not exactly doing a bad job either...

 

[Kensai]

My OBs are mounted to my desk which is pulled out a bit from a corner. In the corner proper is a 6" fake ficus which seems to do an excellent job back there.

Kensai

 

[peterbrorsson]

In the corner proper is a 6" fake ficus which seems to do an excellent job back there.

Kensai

How long are the nails and how many per inch?

 

[Bluto]

I've been real impressed with the OB sound in experiments with some of my drivers. Clean, natural, impressive staging. Really surprised me.

I see many people using wider baffles with smaller drivers and though I don't own 'Quality' large high QTS FR drivers my OB experiments with my cheapie 8" drivers vs. quality smaller drivers are like night and day even using narrower drivers. BIG seems to work.

My readings thus far have me convinced there are no hard and fast rules regarding OB but more so beyond choosing the proper driver many generalizations and some definite truths. I've seen guys making them all kinds of ways stating they're happy with results.

TubaMarks statements regards time delay reflection are pretty much considered amongst those truths but as with all else I've seen Guys arguing if optimum is 5 milliseconds or 8 milliseconds . Mark - I really like the way you explained that. I'd think simply the room and seating position would determine that as well. I can't see OB as a good nearfield speaker in any situation but that's just my opinion, perhaps small driver configurations for computer speaks in a corner arrangement. I had some real success playing with Pio 4"er's doing that. I'm convinced you're definitely going to get the fullness and ambience OB is capable of more so with correct time delay.

I also have the space problems and can only get 16" to my back wall. I could always pull them further out for listening sessions but guys on other forums have told me they have theirs as close as 6" from wall and are happy.

Someone suggested using reflective material behind OB on wall. Any ideas what a cheap good reflective material could be used?

I really like the idea of the blinds. I had been thinking of building a shallow shadow box of sorts (OB baffle itself takes little space) with convex edges (a wave guide of sorts) to place on wall behind OB and reflect sound back. It wouldn't be as efficient as having the proper distance but should help with backwave. Putting blinds in the box as they also only take a small amount of space could be used to direct air both up over the baffle as well as down under the baffle.

Worth a shot .

Steve - I think I know what you speak of but am not sure. Can you expound on it a bit? I believe I've seen that idea in pics but never saw an explanation as to what it was attempting to accomplish. Please post your results.

Audiophile - have you checked out Hawthorne Audio? They make a 'Silver Iris' in a 10" and 15". I had planned on a Visaton 8" until I read reviews there. Guys who had Visatons loved them but admit the larger driver just does more. Some are combining the 8" Visaton or smaller Fostex with the S.I.'s . 10" is my max unfortunately. My own experiments with an 8" Oakton coax and a 10" Tandy bass driver are pretty much what convinced me OB was going to have to be a definite as part of my front end.

Bluto