I've been using a pair of B&G RD-75 for quite a while. They are used as dipoles with no baffle at all - just the bare driver. This works very well, and there is usable response to 150 Hz.
The frequency response of the driver itself shows a peak around 5 kHz of approx 7 dB. Apart from that, the response is more or less flat. I wanted to find out if this peak could be affected by changing the baffle size or shape.
1. Making a wide flat baffle: did not change anything apart from more level below 1 kHz.
2. "Waveguide" type of baffle: only increased the 5 kHz peak.
3. Smoothing the edges of the driver: this actually reduced the peak by 3-4 dB. In addition, this very small extension of the effective baffle width increased the level below 1 kHz by as much as 3 dB.
The modification I did was quite simple, its just round plumbing foam insulators and duct tape... Se pics below.
Anyone with similar experience or suggestions?
The frequency response of the driver itself shows a peak around 5 kHz of approx 7 dB. Apart from that, the response is more or less flat. I wanted to find out if this peak could be affected by changing the baffle size or shape.
1. Making a wide flat baffle: did not change anything apart from more level below 1 kHz.
2. "Waveguide" type of baffle: only increased the 5 kHz peak.
3. Smoothing the edges of the driver: this actually reduced the peak by 3-4 dB. In addition, this very small extension of the effective baffle width increased the level below 1 kHz by as much as 3 dB.
The modification I did was quite simple, its just round plumbing foam insulators and duct tape... Se pics below.
Anyone with similar experience or suggestions?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I've been meaning to try very similar roundover geometries on my Neo3s and Neo10s--still working on my electronics and haven't got back to the acoustic side of things yet.
Adding a baffle should lower the onset of beaming in frequency so I assume the measurements of post 1 are on axis only. It'd be interesting to see the waveguide shape (I'd default to a Le Cleach profile) and how the polars compare between nude and configurations 1, 2, and 3.
Adding a baffle should lower the onset of beaming in frequency so I assume the measurements of post 1 are on axis only. It'd be interesting to see the waveguide shape (I'd default to a Le Cleach profile) and how the polars compare between nude and configurations 1, 2, and 3.
300 Hz / 12 dB should be fine.
I use digital PC-based crossover at 180 Hz with approx 24 dB slope.
You will need EQ as well. First, there is the rather large peak at 5 kHz that you must do something about. Next, the driver will probably need EQ below 1 kHz, depending of baffle size and listening distance. I also think its a good idea to EQ the top end, the driver is more than 10 dB down at 20 kHz.
True - all my measurements were taken on axis.
I didnt keep the baffle or waveguide, they were just experimental anyway. The waveguide was not far from a Le Cleach profile actually.
Will look into doing off-axis measurements of the current solution with the rounded edges (#3 on my list there, and shown on the pics)
Hi StigErik,
I posted two days ago on the older thread, did not notice you started a new one. Your experiments are really interesting, I am myself the proud owner of a pair of Orions. If you have listened to them, how would you compare the B&G+dipole subs?
Cheers
Laurent
PS: I lived in norway for nearly 3 years!
I posted two days ago on the older thread, did not notice you started a new one. Your experiments are really interesting, I am myself the proud owner of a pair of Orions. If you have listened to them, how would you compare the B&G+dipole subs?
Cheers
Laurent
PS: I lived in norway for nearly 3 years!
View attachment RD 75 Crossover 1.pdf
View attachment RD 75 Crossover.pdf Here is the recommendation from B&G to take out the peak around 5K (Notch filter)
View attachment RD 75 Crossover.pdf Here is the recommendation from B&G to take out the peak around 5K (Notch filter)
Don't know if the website still exists, and I do not recall the name of the person who put it up, but he had done extensive baffle tests on the RD75 ribbons when they first appeared on the market.
Iirc, he came up with an asymmetrical tapered and somewhat fat rounded "aircraft wing" profile as providing the best combination of flatness and extension... he tried a LOT of different methods... very good testing location (hung from a gym truss, iirc)
_-_-bear
Perhaps a search will show that it still exists... or someone may remember it.
Iirc, he came up with an asymmetrical tapered and somewhat fat rounded "aircraft wing" profile as providing the best combination of flatness and extension... he tried a LOT of different methods... very good testing location (hung from a gym truss, iirc)
_-_-bear
Perhaps a search will show that it still exists... or someone may remember it.
Dunno, but maybe http://www.archives.org will have it? (not sure if it is archive or archives...)
_-_-bear
_-_-bear
It is Internet Archive: Digital Library of Free Books, Movies, Music & Wayback Machine
The homepage was located at www.snipets.org
The homepage was located at www.snipets.org
Thanks guys, I found the link:
ALSR - The RD75 Dipole Baffle Study - Table of Contents
Quite some reading
ALSR - The RD75 Dipole Baffle Study - Table of Contents
Quite some reading
Intresting reading! Then again, I'm more looking into using the RD-75 as monopoles for better room integration (WAF). As it seems, most people seem to use the RD-75 as dipoles so I can not find much on monopole use.
This was one of the more interesting posts I have read in along time. I am building my own full ribbon planar speaker. Bass ribbon ( apogee like) hand cut. I have one question regarding the DC offset of the amplifier you are using on the BG ribbon. What kind of amplifier are you using to drive the BG ? Even the smallest DC offset on the output when turning on or off the amplifier could destroy the ribbon totally, so be aware. Just curious.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.