| Listening distance [message #23156] |
Tue, 05 September 2006 14:04  |
slinco
Messages: 9
Registered: May 2009
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Esquire |
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Hi guy's. Lot's of great information here, I'm glad I found this forum. I've become confused about something to do with line arrays that maybe you can help me with. I've been reading up on Bohlender Graebener's RD series long ribbon drivers, thinking they might make an excellent mid/tweet driver for an array, or at least a nice wide range midrange driver. The thing I'm wondering about is information BG publishes about the RD series long ribbons that gives "minimum recommended listening distance" - the Rd75 (75 inch ribbon) is 15 feet, the RD50 (50 inch ribbon) is 10 feet. What they say is if you sit closer than these recommendations you'll get reduced high frequency response. The longer the ribbon, the farther you should sit from it. Seems odd. I've read Jim Griffon's paper a few times and see nothing relating to this type of phenomenon. He mentions not being too close, but for the reason of letting indivitual tweeters with gaps between them blend together. With a BG style single continuous ribbon that's obviously not a problem. Am I missing something? Anybody have any thoughts on this? I sit fairly close (8 or 9 feet) due to room constraints, so this type of thing is a concern to me.
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| rd series [message #23161 is a reply to message #23156] |
Wed, 06 September 2006 10:59  |
lcholke
Messages: 73
Registered: May 2009
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Viscount |
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Hi Slinco, I think the main advantage of the rd series is the low xover point. It is like having a full range driver. You could use a first order xover. I heard a pair and they are very good. One issue is the low effency. If you realy like the low xover feature these will be a good choice. You may want to listen to ribbon drivers also before deciding. The xover point will be in th 2k range though. My array gets very quiet when listening closer than 2 ft. -Linc
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| Re: Listening distance [message #23162 is a reply to message #23160] |
Wed, 06 September 2006 11:46 |
Tom R.
Messages: 51
Registered: May 2009
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Baron |
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The only problem is the units sensitivity, which is pretty low at 88db. The woofer line array sensitivy may be higher, depending on how they are wire, and how many drivers are used. Woofer arrays tend to be in the mid 90db range, and if you use a 88db ribbon tweeter you will have to pad down the woofer array to match the tweeters output.
This power will be wasted in a passive crossover.If you have enough amplifier watts to drive the system it may not be an issue, but if you use single ended amps, you may not have enough power to drive them to decent sound pressure levels Newforn research also makes large ribbon drivers. www.newformresearch.com
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| Re: Listening distance [message #23163 is a reply to message #23162] |
Wed, 06 September 2006 12:25 |
slinco
Messages: 9
Registered: May 2009
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Esquire |
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Thanks for the input guys. The low efficiency doesn't concern me too much. I'll be bi-amping with an NAD amp on the woofers. It's plenty beefy and has a variable level control on the back, +/- 6db I think, which should allow for matching up the different efficiency levels. Plus, I'll be using a Behringer 2496 EQ on the bass amp for room correction, as I do now with my bi-amped VR4jr's. Work's beautifully, and will allow another way of balancing loudness between drivers. In fact, if I do decide to buy the BG planar ribbons, the first thing I'll try is sticking them in a panel (or cabinet) on their own and using them with the VR4jr bass cabinets. They put out beautiful bass from 23-250hz - might be a nice match with the ribbons. I know it wouldn't be a true line source and would have some issues, but it'd be an interesting experiment....
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