[jimbones]

Hi Erling,

This looks like a very interesting project.

It looks like you have chosen drivers that are completely open on the back as well as the front.

Most of the speakers I see on this post have a sealed tweeter and no high frequency sound emanating from the back.

How do the high frequencies sound to you when using drivers that are all open on both sides?

Do you like this presentation more or less?

Have you measured the distance from each driver to your listening position and have them all the same distance or do you place the drivers all at different distances?

Thanks for your feedback,

Mark K

Mark,

I just finished building a pair of hybrid OB's with the help of board members (esp Dumptruck, thanks a million times over). They were in design over a year culminating in 3 revisions. The second revision had a rear facing tweeter. I removed it for test purposes during the 3rd revision and I preferred it without the RFT. The localization of images improved greatly. Sounds much clearer and focused. I am not sure but check NOLA speakers if they have a RFT. YMMV.

Jim

[Mmaxed]

Mark,

I just finished building a pair of hybrid OB's with the help of board members (esp Dumptruck, thanks a million times over). They were in design over a year culminating in 3 revisions. The second revision had a rear facing tweeter. I removed it for test purposes during the 3rd revision and I preferred it without the RFT. The localization of images improved greatly. Sounds much clearer and focused. I am not sure but check NOLA speakers if they have a RFT. YMMV.

Jim

Jim, do you have a write up about your speakers somewhere?

[markk]

Hi Jim,

Thanks for your information on the rear facing tweeter and how it sounded for you.

I was also interested on how only one tweeter would sound if it had its back portion open and radiated sound equally from the front and back.

These tweeters would be limited in number and would need to be specifically made to to this. For example an ESS Heil would be able to do this.

Here is a link of the speaker I gave as an example.     

http://www.parts-express.com/pe/showdetl.cfm?partnumber=264-600


Has anyone had any experience on how a system sounds with all of its forward facing drivers from the lowest bass to highest treble are also open in the back.

It seems that this configuration would be the definition of a true full range open baffle loudspeaker.

I can't think of many commercially available Open Baffle loudspeakers  where this the case. 

Thanks for your reply,

Mark K

[doak]

Has anyone had any experience on how a system sounds with all of its forward facing drivers from the lowest bass to highest treble are also open in the back.

It seems that this configuration would be the definition of a true full range open baffle loudspeaker.

I can't think of many commercially available Open Baffle loudspeakers  where this the case. 

Hawthorne Audio Rainier Speaker System


http://www.hawthorneaudio.us/forums/viewtopic.php?f=1&t=4700&hilit=rainier

[Rudolf]

Has anyone had any experience on how a system sounds with all of its forward facing drivers from the lowest bass to highest treble are also open in the back.

It can sound better than a system with no high frequencies radiated to the back, but it depends on the sort of back radiation, the wall distance and the properties of that wall. Just stay at least 3 feet away from the next walls and be prepared to have some absorption or diffusion at the mirror points on that wall.

Don't try to mount common dome tweeters back to back in a dipole fashion. Many people (like me) are happy with the Neo3 as a dipole tweeter. Another option are small cone FR drivers, which will fade out in the back from 4-8 kHz upward. I would never use the Heill AMT the way Hawthorne is doing it. Does he ever show measurements of what his dipoles are doing in the back? 

Rudolf

[studiotech]

I would never use the Heill AMT the way Hawthorne is doing it. Does he ever show measurements of what his dipoles are doing in the back? 

Rudolf

To be fair, it is not a Heil brand driver if that's what you mean.  It's a custom unit.

Greg

[Rudolf]

To be fair, it is not a Heil brand driver if that's what you mean.  It's a custom unit.

Thanks for correcting me, Greg.
I found the official thread for the Reference AMT http://www.hawthorneaudio.com/forums/viewtopic.php?f=2&t=3850 and will try to understand their considerations regarding that configuration. 

Rudolf

[studiotech]

Thanks for correcting me, Greg.
I found the official thread for the Reference AMT http://www.hawthorneaudio.com/forums/viewtopic.php?f=2&t=3850 and will try to understand their considerations regarding that configuration. 

Rudolf

Yes, look for the pictures of the driver.  It is rather large.  I think Hawthorne states that it can be run down to as low as 500Hz IIRC.

[doak]

Yes, look for the pictures of the driver.  It is rather large.  I think Hawthorne states that it can be run down to as low as 500Hz IIRC.

I understand the AMT driver sans synthetic marble horn weighs about 30lb.

[InfernoSTi]

I would definitely give them a listen before you passed judgement on the HA Reference sound quality.  Folks who have heard them seem to really like (love?) the way they sound.  Not your standard Heil AMT at all.

To be clear, I've got a pair in my listening room an a four speaker configuration (mains plus Augie towers).   I've also got diffusion directly behind them on the front wall plus some absorption between them and in the front corners, as well, of course.

Best,
John

Left "speaker"(not the best photo):

[Rudolf]

John,
I would definitely give them a listen before you passed judgement on the HA Reference sound quality. 

I don't want to appear as some criticaster - I didn't talk about sound quality at all.
I'm just curious (not questioning!) how they mastered the limitations set by the 500 Hz crossover frequency, and how the different front/back loading of the AMT worked for them.

Rudolf

[sfdoddsy]

Hi Jim,


Has anyone had any experience on how a system sounds with all of its forward facing drivers from the lowest bass to highest treble are also open in the back.

It seems that this configuration would be the definition of a true full range open baffle loudspeaker.


Mark K

There are a bunch of speakers with drivers that are open at the back in the sense there is no enclosure, but not in the sense that they radiate in a dipole fashion all the way up.

The higher in frequency you go up, the narrower the baffle required to do this, and soon it becomes physically impossible.

So even speakers that have true full-range dipole drivers (ie equal radiation front and back) like planars do not have a dipole pattern when placed in a real baffle.

The exception might be a tweeter with no physical size, like a plasma, or a true omni like MBL.