Since hearing some harbeth monitor 20's in work, i fancied building some of these but obviously not the proper job as they are far too expensive. Falcon acoustics used to sell a mini monitor kit based on the bbc design that used their own crossovers, monacor SPH-135AD woofers and scanspeak classic tweeters (D2008/851100 i believe) They seem to have disappeared off their website recently though. I have a fair amount of spare plywood and the drawings from the LS3/5a site to help construct the cabinets. Can't really find any information on the harbeths though.
Question is what drivers do i use? Kef B110/T27's are out as they are way too expensive for what they are. I can buy some pre-made stirling crossovers which are designed with the monacor driver in mind here. The price isn't too bad considering it'd cost near that much for a pair of falcon crossover kits and a pair of woofers. For the tweeters, I've been looking at the morel CAT298's as they are considered a drop in replacement for the T27, but i've also seen people suggest Scanspeak D2905 9500 and SEAS Prestige 27TFFC H881 too. (with suitable L-pad arrangements)
Question is what drivers do i use? Kef B110/T27's are out as they are way too expensive for what they are. I can buy some pre-made stirling crossovers which are designed with the monacor driver in mind here. The price isn't too bad considering it'd cost near that much for a pair of falcon crossover kits and a pair of woofers. For the tweeters, I've been looking at the morel CAT298's as they are considered a drop in replacement for the T27, but i've also seen people suggest Scanspeak D2905 9500 and SEAS Prestige 27TFFC H881 too. (with suitable L-pad arrangements)
The Eekels' Mini is well beyond my budget as the SEAS excel woofers are £130 each. I reckon i can build a pair of the stirling based LS3/5a for less than £250.
The continuum was an option i looked at but as it's only available in the US, i'd end up suffering import duty which is prohibitively expensive. I'm happy to stick to the old fashioned BBC design even if they aren't quite as good as others. I really need the compact size anyhow.
The continuum was an option i looked at but as it's only available in the US, i'd end up suffering import duty which is prohibitively expensive. I'm happy to stick to the old fashioned BBC design even if they aren't quite as good as others. I really need the compact size anyhow.
Seas 19TAF/G H0414-08 Tweeter - Prestige Series
Seas 22TFF H1280-06 Tweeter - Prestige Series
Hi,
Consider the above. The drop in replacements seem to be
more about the flange size than being similar to the T27.
rgds, sreten.
Seas 22TFF H1280-06 Tweeter - Prestige Series
Hi,
Consider the above. The drop in replacements seem to be
more about the flange size than being similar to the T27.
rgds, sreten.
I've used the 22TFF in place of T27's in my chorale clones (goodmans minister thread) Required a 3.5dB L pad to get it to integrate nicely.
Going active would require more amplifier channels than i presently possess, plus obviously the miniDSP too.
Going active would require more amplifier channels than i presently possess, plus obviously the miniDSP too.
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The two most promising 5" Polycone mid/woofers I've looked at are the Vifa P13WH-00-08 and the low inductance Morel CAW 538, both good enough to run filterless:
Vifa P13WH-00-08 Mid Woofer
Morel CAW 538 Woofer
Available crossover design is not quite LS3/5A territory, but Lynn Olson's Ariel and the Eltim CA 620 give you enough to work with:
ELTIM CA 620
You need to know how to calculate the Zobel values to adjust the crossovers, but I think it's doable:
Impedance Equalization (L-Pad) Circuit Designer / Calculator
Cabinet shape is your choice really. Golden ratio 0.618:1:1.618 and damped port (aperiodic) would be my preference. These drivers justify their cost with vented pole pieces which are a good thing. The CAT 298 tweeter looks good for a soft dome, and is a different animal from metal cones with plastic fascia. I am always quite amazed people use metal domes in monitors. They just don't sound right IMO.
Vifa P13WH-00-08 Mid Woofer
Morel CAW 538 Woofer
Available crossover design is not quite LS3/5A territory, but Lynn Olson's Ariel and the Eltim CA 620 give you enough to work with:
ELTIM CA 620
You need to know how to calculate the Zobel values to adjust the crossovers, but I think it's doable:
Impedance Equalization (L-Pad) Circuit Designer / Calculator
Cabinet shape is your choice really. Golden ratio 0.618:1:1.618 and damped port (aperiodic) would be my preference. These drivers justify their cost with vented pole pieces which are a good thing. The CAT 298 tweeter looks good for a soft dome, and is a different animal from metal cones with plastic fascia. I am always quite amazed people use metal domes in monitors. They just don't sound right IMO.
I'm very happy with my Morel MW144's The CAW 538 looks like a refined version. If morel have done what they did with the MW144 and the DMS37, then I would think that a better match for the CAW538's would be the CAT378.
The DMS37 when flush mounted, is almost perfectly time aligned with the MW144's when surface mounted. It may well be the case with the CAW538 / CAT378 combo as well.
You should be able to go without a zobel with these drivers as well I didn't use any with the MW144/DMS37 combo.
Tony.
The DMS37 when flush mounted, is almost perfectly time aligned with the MW144's when surface mounted. It may well be the case with the CAW538 / CAT378 combo as well.
You should be able to go without a zobel with these drivers as well I didn't use any with the MW144/DMS37 combo.
Tony.
Cost is the biggest problem for me here as i want to keep the costs around £250 total for everything. (sealing strips, terminals, crossovers, drivers, grilles etc) The 5" monacor woofer is already decided as it is a close match to the old B110 and it doesn't cost the earth. The cabinets will remain as per the BBC design so 304 x 190 x 165mm. I've seen that falcon acoustics suggested extending the depth of the cabinet to 230mm but i'd rather keep the cabinets compact. I've already got some spare plywood from liberated shelving which i'll be using to construct the cabinets.
Out of the many tweeters i could use, which is the best choice within my budget? I'd rather not be spending above £80 in total for both tweeters so a maximum cost of £40 each. (means that scanspeak are out)
Out of the many tweeters i could use, which is the best choice within my budget? I'd rather not be spending above £80 in total for both tweeters so a maximum cost of £40 each. (means that scanspeak are out)
to get something akin to a T27 isnt easy, dont seem to be many mylar domes worth mentioning any more. I use the fabric dome visaton g20sc, and its rather good and around 30 quid each, very flat impedance AND response, and 20mm diameter like the T27, but it doesnt sound like a T27. Some of the Morels look ok, but theyre probably a touch over budget.
I'm very satisfied with the sound i get from my home made kef chorales which use Kef B200's and SEAS 22TFF H1280 tweeters. (with a falcon aB crossover designed for the T27 + a -3.5dB L-pad added) If the seas tweeters work in this case, would they still work when used with the monacor woofer?
Also, are the tweeters connected in anti-phase in the LS3/5a like my chorales?
Also, are the tweeters connected in anti-phase in the LS3/5a like my chorales?
Not certain on it, but i think that the stirling crossovers are similar to the image attached. Would the 6 ohm impedance of the seas tweeter and the addition of an L pad cause any problems? Another thing i'm not certain on is whether i'd need to attenuate the tweeter more in this design vs my chorales. (-3.5dB in the chorale using a 2R in series and 12R in parallel)
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I couldnt say. And that is my point. Without simulating the the driver response with the filter, i couldnt possibly say with much certainty. Some one may know otherwise, if they have used those drivers with that crossover. If the crossover is made for the SPH 135 then id probably use the low pass and modify the Highpass to suit the Seas tweeter. Id imagine, unless youre very fortunate, that you would need to experiment with different capacitor and or inductor and resistor values, so much of the tweeter circuit may need to be altered. At least the low pass should deal with rolling off the woofer breakup, if its designed for the monacor. With out frd file etc and circuit simulation its hard to predict the outcome. Its either trial and error, or learn a bit about simulating using the excellent frd tools out there for free. If you dont already that is. I have used frd tracer, and used files ive found at Zaphs, or from other DIYers, and together with Boxsim (also free) to simulate the frequency response, phase etc. Its a powerful too, and there others, some free, some not.
The other thing to consider is this; do you want an LS3 replacement of just a good small 2-way. Plenty of good small affordable 2-way designs. If the BBC had of had access to better drivers ( such as the Vifa P-13, Scanspeak etc ) they may have used them and spent less time and money on cross-over design.
I am beginning to think the prices being paid for the KEF drivers ( and LS3s ) are more nostalgia than anything
I am beginning to think the prices being paid for the KEF drivers ( and LS3s ) are more nostalgia than anything
Going active
Doug (brisso57),
Interesting option to go active
. I have build the linkwitz system some odd 25-30 years ago. The ubits are still in good condition and I always want to try a LS5/3A copy. Do you have crossover files available for the miniDSP? I have one in use for a different setup, but I am very much interested in the LS5/3A Clone.
Thanks in advance
Regards,
Michiel
Doug (brisso57),
Interesting option to go active
. I have build the linkwitz system some odd 25-30 years ago. The ubits are still in good condition and I always want to try a LS5/3A copy. Do you have crossover files available for the miniDSP? I have one in use for a different setup, but I am very much interested in the LS5/3A Clone.Thanks in advance
Regards,
Michiel
I really wouldn't fancy trying to clone a LS3/5A using entirely different drivers like the Monacor 5" polycone, similar as it might be to a KEF B110. You have to understand what was very precisely good about the LS3/5A. It was the notch filter on the bass along with great phase alignment and very flat frequency response.
Let's look at Samadhi's WLM Stella clone, pictured below. The problem is the familiar bass hump at 1.3 kHz. You need a RLC notch to cure that accurately. That varies with the driver, in this case a Visaton W130S.
The next 3 images show the modelled response of a wallmounting bookshelf with a top class filter and a Visaton TW70. The last image shows axis dispersion using the smaller Visaton TW6 tweeter, which is my surprising current weapon of choice here. Thing that is good about Visaton is the modelling software.
Let's look at Samadhi's WLM Stella clone, pictured below. The problem is the familiar bass hump at 1.3 kHz. You need a RLC notch to cure that accurately. That varies with the driver, in this case a Visaton W130S.
The next 3 images show the modelled response of a wallmounting bookshelf with a top class filter and a Visaton TW70. The last image shows axis dispersion using the smaller Visaton TW6 tweeter, which is my surprising current weapon of choice here. Thing that is good about Visaton is the modelling software.
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