Yes, I've been wanting to measure 902s. We'll do that after you get BMS dialed in and run your own comparisons.... :yes:
Drivers for 811b's ?
- Thread starter westend
- Start date
skywave-rider
Slumming in Akihabara
Too late?
Haven't heard back from dgwojo.
Hope I'm not too late for the BMS buy....:tears:
Haven't heard back from dgwojo.
Hope I'm not too late for the BMS buy....:tears:
I was busy at the movie theatre again tonight, I sent you a PM, you'll make the even dozen we need if nobody further bails out, thanks, Dave.
Seeking Infinity
Selenium D220Ti on 811B horn, two units again provided by member Jackgiff, below.
Fairly well matched, a simple R||C compensation filter has them playing flat (+/- 2 dB) to 18 kHz, and largely free of ripple, 20 kHz being down but 2 dB from there. Some additional fixed attenuation may be required.
Crossing at 1.2 kHz sounds O.K., but 1.5 kHz and above per the manufacturer's recommendation is appreciably better. 800 Hz is not acceptible, I would say, from listening.
No, they do not sound as good as BMS.
Caveat: These are thread-on drivers using a throat adapter. I would not expect the response of direct bolt-ons to be different, but that is unverified.
D220Ti vs. D210Ti (bolt-on). This pair of D210Tis is better matched, but the response is not as smooth, and they require 4 - 5 dB more compensation than D220Ti.
The answer is, "Almost."
Selenium D220Ti on 811B horn, two units again provided by member Jackgiff, below.
Fairly well matched, a simple R||C compensation filter has them playing flat (+/- 2 dB) to 18 kHz, and largely free of ripple, 20 kHz being down but 2 dB from there. Some additional fixed attenuation may be required.
Crossing at 1.2 kHz sounds O.K., but 1.5 kHz and above per the manufacturer's recommendation is appreciably better. 800 Hz is not acceptible, I would say, from listening.
No, they do not sound as good as BMS.
Caveat: These are thread-on drivers using a throat adapter. I would not expect the response of direct bolt-ons to be different, but that is unverified.
D220Ti vs. D210Ti (bolt-on). This pair of D210Tis is better matched, but the response is not as smooth, and they require 4 - 5 dB more compensation than D220Ti.
Attachments
spaceman
Registered Lunatic
Aha, thanx for joining up, I wondered who else it was. :thmbsp: I'm hoping they make us all happy campers. :yes: I'm pretty new to this game myself, but I've seen your lengthy thread at LH, & it's helped me to understand things better.
DRAT! I was going to order some extra diaphragms, but forgot.
Why don't we make that YOUR assignment?
:Order a can of this and see if you can put a VERY thin coat on the back of the diaphragm, hardly more than a uniform dusting; you don't want to add much mass:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=268-250
You may have to thin it and brush on. See the manufacturer's specs there.
Some guys on LHF used a turntable (33-1/3 RPM, presumably,) to do a similar sort of application by hand.
westend
Audiopile
That should dampen the heck out of it. Maybe some Modge-podge, if it would stick, would be a better material.Thinning it down and applying one coat at a time for experimental purposes might be beneficial.
The hunt for drivers for the 811b's has ended for me, at present. Through the grace of the AK network, I was able to get ahold of a pair of 802-8g's. I havent had time to hook them up yet and don't know what I have in stock for capacitors, at present. I'll be looking long and hard at Jeff Marquardt's site for inspiration and searching here and at LH for a crossover solution. Somebody had a crossover box that he built with a plexiglass top that held both networks. It was a handsome piece of work and I might emulate that. Thanks to all the contributors to this thread for the work and experimenting. Who knows, I have an orphan 811b so if I come across another I may have another set to play with.
The hunt for drivers for the 811b's has ended for me, at present. Through the grace of the AK network, I was able to get ahold of a pair of 802-8g's. I havent had time to hook them up yet and don't know what I have in stock for capacitors, at present. I'll be looking long and hard at Jeff Marquardt's site for inspiration and searching here and at LH for a crossover solution. Somebody had a crossover box that he built with a plexiglass top that held both networks. It was a handsome piece of work and I might emulate that. Thanks to all the contributors to this thread for the work and experimenting. Who knows, I have an orphan 811b so if I come across another I may have another set to play with.
macaltec
Metal Master
DRAT! I was going to order some extra diaphragms, but forgot.
Why don't we make that YOUR assignment?
Order a can of this and see if you can put a VERY thin coat on the back of the diaphragm, hardly more than a uniform dusting; you don't want to add much mass:
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=268-250
You may have to thin it and brush on. See the manufacturer's specs there.
Some guys on LHF used a turntable (33-1/3 RPM, presumably,) to do a similar sort of application by hand.
I have no way to measure the benefits/detriments of such an experiment. I don't do ir-reversable mods to anything either. I was thinking of a small piece of foam placed under the diaphragm upon re-assembly. Different densities/sizes should yield different results. I have seen this type thing on a few other replaceable diaphragms.
Theory and experience say it's spurious resonances coming from all over the diaphragm, including the surround. I don't think you'll get at that with foam behind the diaphragm.
I don't know how to measure it, but I can tell you there's significant audible differences between damped vs. undamped titanium diaphragms.
The diaphragms are $10 apiece, and if you get it right, there'll be no need to reverse it.... :yes:
How did you pull it apart
How did you pull it apart ? By pulling the studs that hold it to the horn and putting in longer 1/4" bolt and tightening it in there pushing the metal plate out ?
And why does it need to be recharged before use ? Cant we press it all back together ?
I have a couple that have really bad voice coil dust.
I also have one that has a broken off bolt that holds the end cap on. Removing the plate will probably let me grip it and get it out.
Thanks.
Srinath.
From 30 years ago and still produced today, they replace the old metal phase plugs used up until about 1976, Dave.
Metal phase plugs, remember, never take a driver apart like I did, it must be recharged before re-use;
How did you pull it apart ? By pulling the studs that hold it to the horn and putting in longer 1/4" bolt and tightening it in there pushing the metal plate out ?
And why does it need to be recharged before use ? Cant we press it all back together ?
I have a couple that have really bad voice coil dust.
I also have one that has a broken off bolt that holds the end cap on. Removing the plate will probably let me grip it and get it out.
Thanks.
Srinath.
Hi,
I forgot why Bill at GPA told me they need recharging but I know he was correct. After I reassembled the drivers, there was no magnetism to speak of at the phase plug, recharging must have realigned the magnetism lines and set the polarity correct, yes, Bill can actually set the polarity through magnetism, I've had him rephase some 604 drivers. I removed the horn stud bolts, put long nails in, and held the driver body down while pushing evenly on both nails on a hard surface. I'd try using masking tape to clean the throat before taking them apart, just my thoughts, Dave.
Oh cool Nails eh ...
I dont think I can press it out that way, but Bill (GPA) said I can just pry that plate off.
The stuck screw has to come out, then I'll send it to Bill - there is 2 more that gotta go to him, I cant get the voice coil cleaned out with anything, some metal has got in there.
Cool.
Srinath.
I dont think I can press it out that way, but Bill (GPA) said I can just pry that plate off.
The stuck screw has to come out, then I'll send it to Bill - there is 2 more that gotta go to him, I cant get the voice coil cleaned out with anything, some metal has got in there.
Cool.
Srinath.
I opened mine. And cleaned it all out, and put it back together - and notice no cchange in the magnetism, and its actually equal to the ones I have not opened.
I may have some idea about how to open it and what to not do -
The plate can be pried off, and it will come with the 1/2 dome. Do not attempt to take any more of it apart. You can clean the voice coil gap well in that situation because the plate is non magnetic once you pry it off the rest of it. It will clean out well and you can get ait in it and what not.
The main idea is - that is all you remove, and you mark it and bolt it back in the same location it came out from. The voice coil gap will be non magnetic, and you can duct tape it or blow with air or stick a plastic prong in there and clean away.
Yea - do this at your risk - YMMV, and dont blame me if it stops being magnetic ... LOL.
I plann on pulling it apart again tomorow and cleaning it further. Today was a little bit of a quick and dirty job cos I was mainly trying to see ig it will survive. I'm gong to hit it with more air tomorow and do duct tape and other stuff to get it clean clean clean, then I'll put duct tape over it and keep aside till use.
Cool.
Srinath.
I may have some idea about how to open it and what to not do -
The plate can be pried off, and it will come with the 1/2 dome. Do not attempt to take any more of it apart. You can clean the voice coil gap well in that situation because the plate is non magnetic once you pry it off the rest of it. It will clean out well and you can get ait in it and what not.
The main idea is - that is all you remove, and you mark it and bolt it back in the same location it came out from. The voice coil gap will be non magnetic, and you can duct tape it or blow with air or stick a plastic prong in there and clean away.
Yea - do this at your risk - YMMV, and dont blame me if it stops being magnetic ... LOL.
I plann on pulling it apart again tomorow and cleaning it further. Today was a little bit of a quick and dirty job cos I was mainly trying to see ig it will survive. I'm gong to hit it with more air tomorow and do duct tape and other stuff to get it clean clean clean, then I'll put duct tape over it and keep aside till use.
Cool.
Srinath.