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Old 27th July 2012, 12:20 AM   #1
Kei is offline Kei  Wales
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Default LS3/5a mini monitor clones

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)
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Old 27th July 2012, 12:34 AM   #2
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a possible alternative: Eekels' Mini
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 27th July 2012, 02:15 AM   #3
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Old 27th July 2012, 08:31 AM   #4
Kei is offline Kei  Wales
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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.
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Old 27th July 2012, 09:13 AM   #5
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Default Active?

If you're prepared to go active, you could replace the XO with a miniDSP.
Perhaps that would widen your choice of drivers?

Doug
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Old 27th July 2012, 09:20 AM   #6
sreten is offline sreten  United Kingdom
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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.
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Old 27th July 2012, 09:28 AM   #7
Kei is offline Kei  Wales
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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.

Last edited by Kei; 27th July 2012 at 09:31 AM.
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Old 27th July 2012, 01:41 PM   #8
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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.
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Old 27th July 2012, 02:03 PM   #9
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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.
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Old 27th July 2012, 02:48 PM   #10
Kei is offline Kei  Wales
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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)
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