OB and deflectors

[mashaffer]

I am working on an idea that would incorporate relatively large (8"-10") OB widerange drivers suplemented with a hairy chested sub and super tweeters. For incorporating into the total design I would like to be able to put the OBs fairly close to the rear wall and was considering using a deflector panel to bounce the rear wave toward the ceiling or side walls in order to lengthen the path before the sound is reflected back toward the listening possition. Has anyone tried something like this? How did it work?

Also I would like some input on nice drivers of that size that would minimize the shoutiness that some WR speakers have. Cost doesn't need to be a major factor in this project but neither are we intentionally trying to use ungodly expensive drivers. I have heard that the Fostex F200A is a good possibility so I am searching for info on it right now. I would appreciate other suggestions.

mike

 

[Bob Brines]

I really like the F200A. It has a big, warm sound and is in no way shouty. However, it is not terribly efficient and only has a 1mm Xmax. You will have to cross it to the sub fairly high to get any SPL out of it on an OB. Of course I could be wrong, but if it doesn't work out for you on an OB, it will work great in a BR or TL.

Bob

 

[mashaffer]

Thanks Bob. It does indeed appear that the Qes is a bit on the low side. I am having a hard time finding the params for the Visaton B200 which seems to be another possibility.

mike

 

[Bob Brines]

Mike,

go to B200. The B200 is dead on for OB. I keep getting questions about putting the B200 in an MLTL, which won't work. Now, getting a pair in the good ol' U.S. of A. may be another problem.

Bob

 

[planet10]

The B200 is a excellent OB speaker. Really good bang for the buck. Fairly beamy until you get phase plugs into them. You can buy them directly from Solen or from any Solen dealer (like me -- i'm mostly selling them modded thou)

dave

 

[MJK]

How do these reflectors work and for what frequency range?

 

[Paul Ebert]

Another OB candidate is the Hempacoustics FR8.0. Their website indicates an OB version being under development, but the regular version is supposed to be excellent (and cheaper than the B200).

BTW, both are available in the US from:

http://www.e-speakers.com

No affiliation, etc.

If you can spend more, the Veravox 7X is supposed to be excellent as well. Check with Solen as to availability.

If you can wait a bit, the 10" Hawthorne coax might be a good option (and you probably will not need the supertweeter).

Good luck.

Paul

 

[Corloc]

You can get B200's in U.S. here.

http://gallery.bcentral.com/GID4956567DD509576-VISATON-Full-Range.aspx

Got mine there, Good people.

Chris

 

[tade]

anyone thought of putting a helmholtz resonator tuned below the low cut off of the woofer behind an OB to absorb the rear wave and allow the front wave to propogate like a monopole woofer? I should think this would be like a bit of bass boost like in a bass reflex but allowing the seaker to remain OB.
What are your thoughts?
Also, that sounds like a fine idea. Wont gain you any extention of course but I think it would allow you to push the speakers back and may even add to the soundstage.

 

[Corloc]

Yes, Johnincr, has been working on that. search the forum for "rlh"

 

[tade]

Groovey, thanks

 

[mashaffer]

Thanks for all the useful replies. I haven't built deflectors yet. I am asking to see if it is worth trying. The idea is to deflect the backwave away from the back wall which would otherwise be to close (early reflection issues). My thought is that if the backwave is redirected up or to the outside I can get 3+' of travel before reflecting back into the listening area. What I don't know is if this will cause other problems with the imaging.

The B200 looks very nice on the low end (though a bit weak in maximum SPL) but the upper mids look a bit shouty on the response plot which is what I would like to avoid.

This project includes a twin driver sub so maybe I ought to go with the F200A and orient the sub drivers for stereo operation so that I can cross up around 80Hz or so.

mike

 

[mashaffer]

PS

I didn't know Hawthorn was doing a 10". I was in fact thinking of sending them a note suggesting just such a thing. If they could get the xover up around 5K that might be ideal for this application!

mike

 

[Paul Ebert]

Here's some info on the 10" coax:

Hawthorne 10" Coax

I do not know where the xo will be set, but 6k seems high to me. Depends on how much beaming you can tolerate, I guess.

Availability is supposed to be soon.

Paul

 

[planet10]

The B200 looks very nice on the low end (though a bit weak in maximum SPL) but the upper mids look a bit shouty on the response plot which is what I would like to avoid.

I don't know what is with that plot... the driver does not sound like you think it would given that plot. The top is very good, if quite beamy (that is remedied by phase plugs -- the top then is very good -- actually better than the top on the Hawthorne Silver Iris 15" (with the obselete XO)

dave

 

[johninCR]

MAShaffer,

Using absorbant behind the driver is also a good way to resolve near wall placement issues. I also use a triangular column as a deflector in the way you mention. I doesn't add rear wave pathway length, but it does improve the coherency of the rear wave content instead of just bouncing off of a flat wall back to the baffle and all around a jumbled mess. With near wall placement though, I believe rear wave attenuation is mandatory because of the insufficient time lag for rear wave reflections. Absorbing the higher frequency content of the rear wave works well. You lose some of the openess that a further from the wall placement allows, but it's still far more open sounding than any boxed speaker and you retain the naturalness of OB.

Regarding Tade's idea of a helmholtz absorber (not resonator which sounds terrible) on the backside, you really can't absorb enough of the output to make much difference. I have had success using the Helmholtz principle to shunt off some of the rear wave bass output and send it on a longer expanding pathway.

 

[mashaffer]

Those Baby Hawthornes look sweet! The 15s are probably best for really big HT setup but I bet the 10s will be nearly ideal for average size systems. They have the advantage of allowing a higher tweeter cross which will be good for music.

So John I take it that you feel that absorbing part of the rear wave would be more productive than trying to channel it. That reminds me... I have been meaning to drape some fiberglass behind my OBs to moderate the shout but have been having too much time enjoying the music.

mike

 

[johninCR]

Those Baby Hawthornes look sweet! The 15s are probably best for really big HT setup but I bet the 10s will be nearly ideal for average size systems. They have the advantage of allowing a higher tweeter cross which will be good for music.

So John I take it that you feel that absorbing part of the rear wave would be more productive than trying to channel it. That reminds me... I have been meaning to drape some fiberglass behind my OBs to moderate the shout but have been having too much time enjoying the music.

mike

In my experience, near wall place requires rear wave attenuation, so I'd do that before experimenting with a deflector. I like the effects of both, and fine tune the overall sound with attenuation. Then the deflector brings the image into sharper focus by helping control the rear wave flow. In each case I've used a deflector it brings the midrange forward, so if your midrange is already hot, like with B200's, the deflector may not be a good thing. The deflectors have been most beneficial for corner placement, where an OB struggles due to the congested reflections.

I wouldn't use fiberglass (bad for the lungs), instead polyfill batting and thin open cell foam.

 

[planet10]

for average size systems.

keep in mind that given that they are OB speakers, and that the reach in the bass is largely determined by the baffle size, the resulting speaker size won't necessarily be smaller... i do think a 10" has a better chance in the midrange and am very interesting in the SI 10"

dave

 

[Paul Ebert]

Dave,

Did you have an opportunity to evaluate the new SI crossover? If so, I'd be interested in your thoughts. In particular, if it impacted your comparison of the SI to the B200.

My issue with the B200 is that, in my frequency range of interest (below 2K or, perhaps even, 600) it's sensitivity is too low. I'm looking for >93 dB/watt. If I could find a driver that could cover 100 hz to 2K with 95 dB/watt, good linearity, and low distortion, I'd be delighted. Hence, I too am very interested in the SI 10".

Paul