Rogers BBC Studio Monitor Find - Help
- Thread starter Wolverine
- Start date
Resurrecting this thread to mention that I just bought a pair of Dalesford woofers for my Monitors. I'm excited to see I will be a little closer to something that resembles the original driver configuration.
Any idea which Dalesford woofers you bought?
It looks like it's a pair of D50/200's. Seller said one of them may have a issue. I didn't pay too much so I'm wondering if it might be worth it to try and get it repaired depending on if/what the issue might be. Do you have any experience with those woofers?
Only to the general extent of collecting a few of them for various trials vs. the similar KEF B200 bextrene drivers and for use in my Rogers Monitor 2 (very similar to the Export Monitor if not identical) and maybe as a spare in the IMF TLS50 mk. II. Hope you can figure out what might be wrong with the driver - most common are damaged tinsel wires and attachments to the voice coil, assuming the coil itself is ok.
Another update. So the one Dalesford woofer was bad and I couldn't find the problem just from a visual inspection. I dropped in the solo driver and liked the sound so I have been on the lookout for a match. Found a pair on eBay and they are now headed my way. Excited about the prospect of having these close to original! Hope to have them installed next week.
Radfordman
Super Member
Excellent, I'll be interested to know what you think.
Radfordman
Super Member
They look good, same as the ones I have.
See how they perform with crossover as is. I have done a small crossover mod. The reason for this is that the original drivers had a stated nominal impedance of 15 Ohms, the Dalesfords are 8 Ohm, although I suspect that the original drivers may be somewhat less than 15 Ohms. My mod will ever so slightly boost the mid. Details available, I can't remember if I supplied them before.
See how they perform with crossover as is. I have done a small crossover mod. The reason for this is that the original drivers had a stated nominal impedance of 15 Ohms, the Dalesfords are 8 Ohm, although I suspect that the original drivers may be somewhat less than 15 Ohms. My mod will ever so slightly boost the mid. Details available, I can't remember if I supplied them before.
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Radfordman
Super Member
We don't know if the sensitivity of the Dalesford is the same, or different to the original unit. I suspect that it is similar. However, one could try different tappings on the autotransformer for the feed to the HF1300. Mine seems about right with the tapping that was set for the original bass unit.
Sorry, I meant to edit my post, not reply to my own post. It's a bit early in the morning here!!
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Thanks for the info! Any mods to the crossover are beyond my skill level especially one as complicated as this crossover. At some point I would like to see about a recap and possibly see if it makes sense to convert them from 15 ohm to 8 ohm due to these woofers. In the meantime I am enjoying them as they are. I have listened to a couple of SACD's on them and the Dalesford's have taken them up a notch with a more robust Bass and vocals which were already a high point that are now just liquid smooth and extremely detailed. I have them paired with my Pioneer Elite system and there is definite synergy going on there between the source and the speakers!
Radfordman
Super Member
Actually, the basic crossover circuit is quite simple, apart from the large autotransformer, it's pretty similar to the Spendor BC1 crossover. The slight modification that I have done would be very easy to implement.
A recap should not be necessary, all capacitors are non electrolytic and will most likely still be absolutely fine.
It not possible to "convert them from 15 ohm to 8 ohm". If you are taking about adjustment to compensate for the difference in impedance of the Dalesfords. This compensation would be adjustment of the tweeters sensitivities and inductors/ capacitors in the bass unit feed. You can adjust the impedance of the whole speaker by means of the autotransformer. Yours may be set to 8 or 15 Ohms, the most commonly used settings. The label on the back of the speakers should tell you how it was set at the factory.
So, it's great, you have working speakers, and a spare bass unit. Your speakers are now effectively early Rogers Export Monitors. The early Export Monitors had the exact LS3/6 cabinets and exact LS3/6 crossovers, my friend has a pair. Later production changes with cheaper cabinets, cheaper crossover, square front HF1300's and a KEF T27 instead of the HF2000.
A recap should not be necessary, all capacitors are non electrolytic and will most likely still be absolutely fine.
It not possible to "convert them from 15 ohm to 8 ohm". If you are taking about adjustment to compensate for the difference in impedance of the Dalesfords. This compensation would be adjustment of the tweeters sensitivities and inductors/ capacitors in the bass unit feed. You can adjust the impedance of the whole speaker by means of the autotransformer. Yours may be set to 8 or 15 Ohms, the most commonly used settings. The label on the back of the speakers should tell you how it was set at the factory.
So, it's great, you have working speakers, and a spare bass unit. Your speakers are now effectively early Rogers Export Monitors. The early Export Monitors had the exact LS3/6 cabinets and exact LS3/6 crossovers, my friend has a pair. Later production changes with cheaper cabinets, cheaper crossover, square front HF1300's and a KEF T27 instead of the HF2000.
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Radfordman
Super Member
I have edited my previous post, worth a look again.
The speaker is still a highish impedance system, compared with say, 4 Ohm or 6 Ohm speakers, so copper conductors can be thinner. I have not changed the internal wiring, I do not consider it necessary. In fact connecting thick wires to both the HF2000 and HF1300 would be a little difficult, and a waste of time in my view.
I will look for my mod.
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Radfordman
Super Member
View attachment 1143622 Here is the
mod, 39 Ohm resistors may not be easily available, I just had some, the nearest standard value to them should do.
View attachment 114362 View attachment 1143622 2[/ATTACH]
mod, 39 Ohm resistors may not be easily available, I just had some, the nearest standard value to them should do.
View attachment 114362 View attachment 1143622 2[/ATTACH]
Radfordman
Super Member
Glad to be of help. I have not increased the thickness of the bass unit wiring, it looks a bit thin, but suspect that its about 5A rating, should be fine. I have seen very thick wire used in speakers, so thick and heavy that it strains the unit terminals which were not designed for this.
Radfordman
Super Member
Radfordman
Super Member
No problem, enjoy the music.
I'm pretty sure that we've communicated in the past about speakers on this forum.
Just out of interest, what amplifier are you using? My speakers run all day, and some of the night too, so I'm not using a tube amplifier although I have several, a Quad 303 is working quite well with them.
A point to remember, the speaker is almost a short circuit to the amp at DC. This is due to the large auto-transformer on the input. This is no problem to direct coupled amps, provided that they do not have a large DC offset. Some amps may have protection built in, but some may not.
I'm pretty sure that we've communicated in the past about speakers on this forum.
Just out of interest, what amplifier are you using? My speakers run all day, and some of the night too, so I'm not using a tube amplifier although I have several, a Quad 303 is working quite well with them.
A point to remember, the speaker is almost a short circuit to the amp at DC. This is due to the large auto-transformer on the input. This is no problem to direct coupled amps, provided that they do not have a large DC offset. Some amps may have protection built in, but some may not.
