Having recently acquired a Sugden Headmaster and a Quad 909, I fitted new drivers - new supplied by Spendor in 1997 but never fitted. I am absolutely delighted with the way everything performs. However, I am concerned about overdriving the Spendors and want the main drivers to last.
So, I got to thinking about taking some of the power away from them with a supplementary woofer/mid-range unit. This led to reading as much as I could about various projects and one in particular was the modification to the B&W DM601 S3 cross over. I subsequently bought a pair from eBay, plus a few other bits - good quality and cheap.
However, the more I thought about, the more I realised - whilst it may keep me entertained, it is not an area where I am likely to produce successful results. So I came to the conclusion that I should leave the Spendors alone and go for creating/making a L.S. of my own.
I became intrigued with a full range speaker, vis a vis centred around Fostex units, in particular their FE208 E Sigma. This unit is recommended for Horn enclosures, but as an intermediary stage, want to use a conventional Ported Enclosure.
Fortuitously, a pair of CM7 crossovers arrived today, which are a joy - given the quality I got for peanuts.
The question is now however; before I lay out some serious cash on drivers - does anyone have any experience with Fostex units and the particular one I am interested in is FE208E Sigma. This is recommended for horn enclosures. However, this is going to be a two stage project. The intention is to couple this with a Monacor RBT - 95SR. It may well be it ends up with the Fostex T900A.
However, this is a serious project to keep me occupied through till spring so some serious advice is needed before splashing the cash.
Any help - no matter how trivial the contributor may feel it is, would be gratefully appreciated. - Kicking ideas around gets one closer to a solution, so everyone's contribution is valuable.
As a base line, ultimately I would like to go for a horn enclosure, so this limits the type of drivers I need to employ.
So, I got to thinking about taking some of the power away from them with a supplementary woofer/mid-range unit. This led to reading as much as I could about various projects and one in particular was the modification to the B&W DM601 S3 cross over. I subsequently bought a pair from eBay, plus a few other bits - good quality and cheap.
However, the more I thought about, the more I realised - whilst it may keep me entertained, it is not an area where I am likely to produce successful results. So I came to the conclusion that I should leave the Spendors alone and go for creating/making a L.S. of my own.
I became intrigued with a full range speaker, vis a vis centred around Fostex units, in particular their FE208 E Sigma. This unit is recommended for Horn enclosures, but as an intermediary stage, want to use a conventional Ported Enclosure.
Fortuitously, a pair of CM7 crossovers arrived today, which are a joy - given the quality I got for peanuts.
The question is now however; before I lay out some serious cash on drivers - does anyone have any experience with Fostex units and the particular one I am interested in is FE208E Sigma. This is recommended for horn enclosures. However, this is going to be a two stage project. The intention is to couple this with a Monacor RBT - 95SR. It may well be it ends up with the Fostex T900A.
However, this is a serious project to keep me occupied through till spring so some serious advice is needed before splashing the cash.
Any help - no matter how trivial the contributor may feel it is, would be gratefully appreciated. - Kicking ideas around gets one closer to a solution, so everyone's contribution is valuable.
As a base line, ultimately I would like to go for a horn enclosure, so this limits the type of drivers I need to employ.
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Here is a backloaded horn with a helmholtz resonator (to tame a dip in frequency response)
https://variant-hifi.com/lautsprech...tsprecher/7810/jericho-23-lautsprecherbausatz
https://variant-hifi.com/lautsprech...tsprecher/7810/jericho-23-lautsprecherbausatz
It really, really needs to be in a horn… and preferably driven by a high output impedance amplifier. Which your amps are not.
FF165wk or FF225wk are closer to your goals. The latter, like the FGE208e∑ is not really a FR, both are lacking the top 2 octaves.
But i would suggest looking at the Markaudio (my goto) or someof the other brands given your target.
I have a buddy withthe BC1 he bought new fromme in 1976, my favouirite of the BBC derived loudspeakers… he uses a QUAD 405 with them.
I just recently sent Scott some drivers i thot would make anintersting BC1 insopired reflex.
From what i have experienced, your target of making something a long bthe lines the BC1, and given this is your first diy build, and the recommendation is always to not go overboard on the first one, i’d piut Markaudio CHN-110 in the biggest reflex box they support. Scott has a few sketches on the MA site.
Or maybe something a bit more exoctic like a Classic Golden Ratio box.
dave
Thanks for all replies guys. Currently using my phone as it looks like my PC has been got at - was looking at news about Trump this morning when it just locked up and cannot complete re - initialisation/re boot.
So beware - there may be a few viruses floating about, behind all these news flashes - I should have been more careful.
So beware - there may be a few viruses floating about, behind all these news flashes - I should have been more careful.
Dug out my last coffee soaked PC and tore it apart. The ribbon connector from the keyboard was caked with dried decaf and the ribbon itself corroded and tarnished. Tried cleaning everything with surgical spirits - but no luck. So, I left the ribbon out and connected in an external keyboard - bingo.
Heavens - there are a lot of screws to take out and the interconnects are really delicate. However, a bit of patience and slowing down helped - quite surprised, myself.
No where near as daunting as this Loudspeaker Project. I have read quite a few historical posts about all this and it seems, it will probably turn out a disaster. But I still need to occasionally play my music at a level I would not want to subject the Spendors to.
I am very impressed with Rutcho's Mod to the DM601 S3 so I bought the caps and resistors to modify them to his spec. Then, I acquired a pair of back - plates from CM7's. They have both the moulded port and the LF section of the crossovers attached. So, if I am going to get something akin to a half decent pair of home - made speakers, I am currently thinking along the lines of the 601 S3's LF/Midrange unit + a pair of Monacor RBT - 95SR's.
Given that Rutcho's rework addressed the area where the LF section rolls - off and the HF picks up, it is clear from his plots the response around the crossover wasn't very clean. For this reason, the Monacor looked considerably better than B&W's Tweeter.
So current thinking is to build an enclosure to house both the B&W mid range unit and the Monacor. However, with the CM7 terminal plate + port + LF portion of the CM7's crossover, this could provide the opportunity to fit a driver to cater for frequencies below the B&W Midrange driver.
Building an enclosure with the same footprint as the BC1, but benefiting from increasing the height to that of the BC1, inclusive of their trollies, doesn't seem too ambitious - with plenty of research and the kind of expert knowledge on this forum, will greatly reduce the potential for disaster - would it not?
In adopting this approach, given I am almost there wrt components, It could considerably shorten timescales, with the exception of how best to employ the Low frequency element of the CM7 and a suitable woofer - if not B&W's own from a pucker CM7.
Nothing is set in stone and if there are glaring issues - unbeknown to me, then at this stage, it won't be too costly.
Start with an easy project is the advice I have seen given on this forum. Well, most of the components are already tried and tested. The enclosure and marrying the CM7 crossover to that of the DM601 S3 are issues. That should prove to be the fun bit. Then I can get my Quad 909 to stretch its legs.
Heavens - there are a lot of screws to take out and the interconnects are really delicate. However, a bit of patience and slowing down helped - quite surprised, myself.
No where near as daunting as this Loudspeaker Project. I have read quite a few historical posts about all this and it seems, it will probably turn out a disaster. But I still need to occasionally play my music at a level I would not want to subject the Spendors to.
I am very impressed with Rutcho's Mod to the DM601 S3 so I bought the caps and resistors to modify them to his spec. Then, I acquired a pair of back - plates from CM7's. They have both the moulded port and the LF section of the crossovers attached. So, if I am going to get something akin to a half decent pair of home - made speakers, I am currently thinking along the lines of the 601 S3's LF/Midrange unit + a pair of Monacor RBT - 95SR's.
Given that Rutcho's rework addressed the area where the LF section rolls - off and the HF picks up, it is clear from his plots the response around the crossover wasn't very clean. For this reason, the Monacor looked considerably better than B&W's Tweeter.
So current thinking is to build an enclosure to house both the B&W mid range unit and the Monacor. However, with the CM7 terminal plate + port + LF portion of the CM7's crossover, this could provide the opportunity to fit a driver to cater for frequencies below the B&W Midrange driver.
Building an enclosure with the same footprint as the BC1, but benefiting from increasing the height to that of the BC1, inclusive of their trollies, doesn't seem too ambitious - with plenty of research and the kind of expert knowledge on this forum, will greatly reduce the potential for disaster - would it not?
In adopting this approach, given I am almost there wrt components, It could considerably shorten timescales, with the exception of how best to employ the Low frequency element of the CM7 and a suitable woofer - if not B&W's own from a pucker CM7.
Nothing is set in stone and if there are glaring issues - unbeknown to me, then at this stage, it won't be too costly.
Start with an easy project is the advice I have seen given on this forum. Well, most of the components are already tried and tested. The enclosure and marrying the CM7 crossover to that of the DM601 S3 are issues. That should prove to be the fun bit. Then I can get my Quad 909 to stretch its legs.
Attachments
The BC1 is a brilliant design for its purpose and time. The bextrene plastic driver is more consistent than paper cones and the crossover is of very high qulaity. All cudos to Hugh and Dorothy Spencer! However, there are some design quirks
- The damped thinwalled cabinet reduces resonances in the critical midrange at the cost at some muddling of the bass.
- There are better bass/midrange drivers at the market now than 45 years ago
- There are current dome tweeters that all the way up to 20 kHz so the need for 1" dome +supertweeter on top of that is really not there any more
Got that! However, I have decided not to touch the BC1's, for fear of ending up with a whole bundle of bits on the carpet and nothing to play in the mean time - and importantly, nothing to do A-B comparisons with. Otherwise, makes perfect sense.
However, the recommended crossover frequency for the Monacor is 5khz, the same as B&W Tweeter. But its rating is 40W continuous, which sways the argument. I could not believe how dirty the B&W tweeter's leading edge was, and Rutcho's modification addresses that nicely. However, the RBT - 95SR is as clean as a whistle, which will make for further improvements in the transition area.
It remains a two element loudspeaker, albeit with the extension below midrange being an option with the CD7 crossover. However, with regard to the drivers - I am unwilling to pay for second hand units on eBay, where what kind of life/abuse is unknown to me - for silly money in some instances. The number of damaged Nautilus' is staggering, so it doesn't inspire confidence in those that appear ok!
£84 for a new Monacor is a good base - line. I will have to source woofer/mid-range and am open to suggestions. Provisionally, I could go for a second hand unit, which coupled with new tweeters will give me more confidence in what it all sounds like, but ultimately they too will be new units. That way, there is only one variable - assuming everything else is close. I have absolutely no worries about the modified 601 S3 crossovers. So setting these elements up first, before any experimentation with the lower register driver, should allow for better understanding how the third driver dovetails into all this.
It all sounds so simple - yet I really don't know just how well it will turn out. But if I keep my BC1's in tact - then there is at least a reference point.
Thankyou for the input - much needed, to maintain focus on what I am trying to achieve.
Brian.
However, the recommended crossover frequency for the Monacor is 5khz, the same as B&W Tweeter. But its rating is 40W continuous, which sways the argument. I could not believe how dirty the B&W tweeter's leading edge was, and Rutcho's modification addresses that nicely. However, the RBT - 95SR is as clean as a whistle, which will make for further improvements in the transition area.
It remains a two element loudspeaker, albeit with the extension below midrange being an option with the CD7 crossover. However, with regard to the drivers - I am unwilling to pay for second hand units on eBay, where what kind of life/abuse is unknown to me - for silly money in some instances. The number of damaged Nautilus' is staggering, so it doesn't inspire confidence in those that appear ok!
£84 for a new Monacor is a good base - line. I will have to source woofer/mid-range and am open to suggestions. Provisionally, I could go for a second hand unit, which coupled with new tweeters will give me more confidence in what it all sounds like, but ultimately they too will be new units. That way, there is only one variable - assuming everything else is close. I have absolutely no worries about the modified 601 S3 crossovers. So setting these elements up first, before any experimentation with the lower register driver, should allow for better understanding how the third driver dovetails into all this.
It all sounds so simple - yet I really don't know just how well it will turn out. But if I keep my BC1's in tact - then there is at least a reference point.
Thankyou for the input - much needed, to maintain focus on what I am trying to achieve.
Brian.
"If you have original BC1, add a subwoofer or two to offload stuff below 80 Hz!"
That was my original intention, before investigating what is on the market by way of components. It was also before I fell over the CM7 Crossovers, which started the old cogs churning.
That was my original intention, before investigating what is on the market by way of components. It was also before I fell over the CM7 Crossovers, which started the old cogs churning.
I wonder if anyone has a copy of the CM7 crossover diagram. I have seen an article for modifying for the Mid/Hi frequency section of the crossover, where the author left the Lo Frequency element untouched. That - naïvely says I - bodes well for using the stock LF section in conjunction with the Rutcho DM601 S3 modified crossover. However, it would be interesting to be able to compare the two and although the individual clearly understands the process, it reads Double-Dutch to me without a diagram. He has changed some values, much as Rutcho did, but does not provide the kind of detail that Rutcho has - which kind of spoils an otherwise excellent article.
I have also read of the rule of thumb ''80hz.'', which DrBoar suggests would help the BC1's out - presumably in terms of power handling. But will that really remove much loading from the audio above 80hz.? I would have thought, there still would be considerable power above 80hz., or is it principally to limit the excursions and reduce the problem associated with the Spendors thin cabinet walls?
I see too, the LCR60 S3 and the DM601 S3 have inductors where their fields are on the same axis, whereas, the CM7's crossover inductors are at 90deg!
I have also read of the rule of thumb ''80hz.'', which DrBoar suggests would help the BC1's out - presumably in terms of power handling. But will that really remove much loading from the audio above 80hz.? I would have thought, there still would be considerable power above 80hz., or is it principally to limit the excursions and reduce the problem associated with the Spendors thin cabinet walls?
I see too, the LCR60 S3 and the DM601 S3 have inductors where their fields are on the same axis, whereas, the CM7's crossover inductors are at 90deg!
Re vintage Spendors, is the BC1 the one to get or were any of the subsequent models (eg SP1) superior?
I couldn't say. However, if I were to replace my BC1's, I would be thinking of something where the differences would be somewhat more than just marginal. Edging towards QELS's really.
Studley - bear in mind the drivers are no longer available for the BC1's. Their compliance is such that they won't tolerate high drive levels for too long, before the suspension collapses and the voice coil grates against the magnet.
I have heard of some suitable replacement cones/drivers, but have no experience with them myself. I am lucky because I have had a new pair of spares for quite a while now: just fitted.
Whether the SP1's are comparable, I can't say. But I can't for the life of me think they are in anyway "Inferior" - just different. Loudspeakers are subjective in any case and don't think Spendor would have sold many loudspeakers - not just SP1's - if they weren't of a comparable high standard.
However, given the money, I would need to see a distinct difference between what I have and what I would replace them with.
Had I not owned Spendors, their speakers would still be on my list for consideration.
I have heard of some suitable replacement cones/drivers, but have no experience with them myself. I am lucky because I have had a new pair of spares for quite a while now: just fitted.
Whether the SP1's are comparable, I can't say. But I can't for the life of me think they are in anyway "Inferior" - just different. Loudspeakers are subjective in any case and don't think Spendor would have sold many loudspeakers - not just SP1's - if they weren't of a comparable high standard.
However, given the money, I would need to see a distinct difference between what I have and what I would replace them with.
Had I not owned Spendors, their speakers would still be on my list for consideration.
Hello,
I have a pair of cm7 speakers, and I'm wondering if you have a link to the article you mentioned?
Thanks in advance,
Nathan
Hi Nathan,
Search for DM601 -S3 crossover upgrade design by Rutcho.
I have bought the components to make the changes as I intended to use the cross - overs as a start point for this project. I haven't got very far as we have just moved house, so everything is on hold. I am also considering filtering at pre - amp level and driving a separate LF enclosures with my 405, whilst the 909 drives my BC1's, the low end being filtered off, also at pre - amp level.
Until we are settled, nothing more can be done. However, the plan is firmly in place as I really want to ensure the BC1's are protected. But then again, I won't rule out the possibility of another pair of loudspeakers for higher levels and leave the BC1's to handle low level listening. I have also seen some Harrison in - line LF/HF filters, with various roll - off frequencies which I will probably buy just to give me some idea of the direction I want to take.
Search for DM601 -S3 crossover upgrade design by Rutcho.
I have bought the components to make the changes as I intended to use the cross - overs as a start point for this project. I haven't got very far as we have just moved house, so everything is on hold. I am also considering filtering at pre - amp level and driving a separate LF enclosures with my 405, whilst the 909 drives my BC1's, the low end being filtered off, also at pre - amp level.
Until we are settled, nothing more can be done. However, the plan is firmly in place as I really want to ensure the BC1's are protected. But then again, I won't rule out the possibility of another pair of loudspeakers for higher levels and leave the BC1's to handle low level listening. I have also seen some Harrison in - line LF/HF filters, with various roll - off frequencies which I will probably buy just to give me some idea of the direction I want to take.
In 1988/89 I returned to Libya where a year earlier I was involved with a HF Radio project. The problem this time related to the Antenna Farms, vast arrays of HF Logs, Rhombic and Omni's, one farm being at Benghazi, the other at Tripoli. Unfortunately, as it transpired, off - air broadcasts where making it impossible to check the performance of the arrays.
The solution I came up with was, after checking the stations which were the biggest culprits, I designed a high pass filter, cutting dramatically anything below 1.9 MHz. I submitted the details to the company, only to find they supplied the components and told me to get on with it. "And when they are finished, send them back to us for calibration"!!!!!!!
The point, I suppose of all this prattle is, I had to shroud the capacitors inside sections of copper tubing, bonded to a copper earth plate.
Also, to get the precise value of inductors, elements had to be connected in series. Whilst the response of the filter was pretty text book, the return loss was appalling. That was until I fitted the capacitors snuggly into the copper tubes.
However, the most dramatic effect which gave exceptional return loss performance across the band was achieved by "Dog - legging" the inductors, i.e., where two inductors were connected in series, the second inductor was off - set by 90 degrees. Thus reducing mutual induction considerably.
So, I was rather surprised to see a B&W crossover networks, where inductors shared the same axis and the effect that had on the response of the loudspeaker at the crossover frequency.
I bit of a debate had developed on another forum, when I stated there were no return - loss figures given for crossover designs. Indeed some individuals seemed to believe return loss related only to radio frequencies. Strangely enough, some weeks later, while researching crossover designs, I came across an article which clearly stated return loss figures were both important and were measured. I have since been unable to find that article.
However, whatever design I cobble together, the crossover networks will be checked for return loss. Indeed, many years ago, I would tune both filters and transmitter output networks, and Klystron Amplifiers/Cavity Resonators, by initially doing a coarse tune for frequency response and then substantially align them working only with the return loss figure.
If anyone know of such an article, I would appreciate them posting it. I have hunted high and low, but just cannot find it.
https://techtalk.parts-express.com/...tonight-and-found-something-interesting/page2
Is this what you're after Nathan?