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Old 4th December 2003, 12:08 AM   #21
sreten is offline sreten  United Kingdom
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Coated M18's if I'm not mistaken >>>

Apologies for misinterpreting your 55 litre quote
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Old 4th December 2003, 02:47 AM   #22
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Sure looks like M18s.

Here's it's big brother:

http://www.ruark.net/products/Sterling/excalibur.shtml

Looks like they're talking about M22s but with an inverted dustcap. Certainly looks like a Vifa driver.

M22s are the other option for a Vifa 3 way: 2 x M22, P13, XT25. Deep, potentially loud and with a decent vb.

Mos
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Old 4th December 2003, 04:07 AM   #23
Ap is offline Ap
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Default Vifa M18

Am about to finish (well one day) my boxes - originally were going to be 2 x scan 8545k (I had bought 1 pair but now cant afford another) , mid is the Vifa m13mi, hf planar.
Have changed the bass to Vifa m18 due to cost - they are excellent value!

Was going to be a straight forward 3way but have had a re-think & will probably do a 2.5way with the single m18 on the bass end - will try the Vifa m13mi (alnico) for mid but if its getting over extended down low will switch to either the Seas cb17rcyp or if I can find a pair of scan 8543s cheaply, or someone willing to swap for my 8545ks, - will have to wait & see on that one...

Anyway nice choice on the woofer - I wouldnt go with the d75mx - most mid-domes arent very good (except the ATCs, which ruark use but cost a fortune).

Have heard the p13 & its nice, not the last word on detail but nice.
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Old 4th December 2003, 04:11 AM   #24
Ap is offline Ap
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Default The xt25

Forgot to mention this tweeter looks like a real handful when it comes to xover, my guess is very high qms, not sure about getting down to 3k - I would opt for the Scanspeak d2905 or the revelator if you can stretch the budget.
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Old 4th December 2003, 07:31 AM   #25
navin is offline navin  India
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my 2 cents...

a M18-xt25 combo (whatever the config, 2.5 way MMT or 2 way MTM or whatever) would require high order slopes on both sides. 3rd order i guess would be what you'd be looking at.

favouring lower order slopes why dont you use a classic midrange like the M10MD or MG10 MD from say 300 - 3k.

this way you could use second order slopes on the M18 or even use the M22 instead and also on the XT if you so desire. while i have not heard the xt25 i'd suggest the SS9500 as an alternate. i dont know if they are the same price.

the 75mm vifa dome mid is not really useable till about 600Hz or so even higher by some accounts.

if were set on a 3 way using the M18 and XT I'd go for a W MT W config or WW MT config using the M18, M10, and XT.

the cones are better matched. with 2 m18s u dont need the bass of the P13 and by the way I really prefer vifa low damping surrounds to the high damping surrounds.
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Old 5th December 2003, 01:08 AM   #26
Thomas is offline Thomas  Denmark
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I'll add 2 cents as well

I have buildt a 2-way mtm with the M18 & xt25 about one year ago. I buldt the cabinets of 30 mm MDF with 20 mm birch plywood panels on all sides. A good 50 mm wall thickness, I might add!

I made them 55 litres tuned to 32Hz. - Just as predicted by you guys. I must say I'm most impressed by the bass capability of these babies. The xt's are exelent too. Imageing is stunning as well.

I have some troubble (still) with the cross over though. I use a 24dB with impedance correction for the xt's and a 12dB for the M18's. I find the highs to be a little to 'bright'. Maby because I cross over just below 2000Hz. Also, the mid bass is very dominant. I tried to 'simulate' baffle step compensation by turning up frequencys below 500 Hz, using my computer, and this seemed to solve the problem. Considering that, I think baffle step compensation should be used in the cross over.

The xt's should be good down to 1500 Hz according to the data sheet. But, I'm not shure I would go just that low. I would stay clear of the 3000 Hz region vital for voice reproduction, if possible. What do you think of this? How low can I go?
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Old 5th December 2003, 02:40 AM   #27
sreten is offline sreten  United Kingdom
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Default To thomas

You could convert your MTM to a 2.5 way.

Basically crossover the top M18 to the tweeter, you'll need to
pad down the tweeter and new components for the top M18.

The other M18 is rolled off much lower with a single inductor,
around 300hz ? This will give you full baffle step correction.

JMO but i think MTM's suffer from midrange glare due to the
double sources of upper midrange creating a line source effect.
Lack of baffle step correction certainly won't help.

Another advantage of a 2.5 way is that the unit handling
the midrange is not 'slugged' by the BSD correction inductor
or end up with a resistor in series with it (the bypass resistor
of the BSD inductor). Only disavantage is that your forced to
go with full as opposed to partial, baffle step correction.

I don't think its a good idea to go any lower with the tweeter.

/sreten.
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Old 5th December 2003, 03:03 AM   #28
navin is offline navin  India
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ok 2 more cents...man this will soon add to a full dollar! :-)

i agree with sreten. the large inductor in the LR BSC is a heaache for midrange. go 2.5 way. your net sens will be the same.

the XT would prefer a XO above 3k but given that you have M18 what i'd do is roll one m18 at 2.2k-2.5k (also have impedance comp) or there abouts at 12db. let the XT roll at about 3k 12db too. should be ok. use LSP cad to siumulate XO.

the second M18 at 300hz 6db wil only require one single resistor (as well as impednace comp).

i find impedance comp on woofers makes a lots of sense.

not liking part count...

the lower M18 will have only 3 passive parts, the upper M18 4, and the XT 4-6

every part adds a bit to the music and takes some music away souse as few parts as possible. in fact the imp comp and parallel cap in the upper M18s ckt can be replaced by a simple RC combo. LSPcad lite will help with this.

use google do find LSPcad lite.
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Old 5th December 2003, 04:09 AM   #29
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Hi, Thomas

That seems like a pretty good tuning/vb for those M18s.

Tell me, how does the bass output/tunefulness sound when you give them a bit of power? Would you say the bass seems to sound, um, constrained, compressed? At high inputs does the bass still seem tuneful or do things get a bit mixed up?

For what it's worth, I agree with Navin and Sreten, a 2.5 makes sense. I really like the idea of a .5 way speaker config being used for BSC.

Navin:

Can I have your opnion of the Vifa M22? You've mentioned it in several posts. You see, an alternative to 2 x M18, P13 and XT25 is 2 x M22.

Mos
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Old 5th December 2003, 06:16 AM   #30
sreten is offline sreten  United Kingdom
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Default for Mos

this may give you some ideas regarding twin 8's :

http://www.deadwaxcafe.com/vzone/david/david.htm

/sreten.
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