Help needed in cloning the XRT22 from McIntosh

[tool49]

Hi everyone,

One of my relative is very impressed with my previous DIY speakers and asked me to evaluate what would be the best drivers/crossover to clone the XRT22 speaker. You can find more info about the speakers at the following page. http://www.roger-russell.com/xrt22pg.htm

Now I've done some preliminary research and I have not found a way to clone these speakers with my little knowledge. I figured that some here might have better ideas than mine.

The cost should be under $3000 for the whole set of drivers and crossover parts but excluding the wood.

My first idea would be to ditch the whole passive crossover and go strictly active with a system such as the ongoing group buy. This would clearly simplify the building but would still require 4 stereo amps to drive the whole set. Four chipamps based on the LM4780 might be appropriate, keeping the cost and size down. The woofers might need to be driven by a pair of bridge/parrallel chips.

Now comes the tough part. Which driver to choose? Forty six tweeters isn't going to be cheap if quality parts are chosen.

The tweeter should have a very flat response curve, be of reasonable quality and preferably cheap (isn't that what we're all looking for?) After looking at the cheapies available at Parts Express, I think he will need to invest a little more and get a decent tweeter such as this one: http://www.d-s-t.com/peerless/data/811815.htm

What do you guys think? Will this tweeter be appropriate in a line array? How would I go around wiring 23 tweeters per side to get a driveable impedance?

The woofer choice turns out to be quite complicated too. I suggested this one for the mid bass: http://www.d-s-t.com/peerless/data/831709.htm

The sensitivity of this woofer might be a bit low to match the tweeters though. In an active system, this isn't a big deal but in a passive system it might be. Do you guys know of a better choice similarly priced?

The two woofers are also from Peerless: http://www.d-s-t.com/peerless/data/831857.htm

Now these require a HUGE box to play down low (around 6 ft^3) But would they do a decent job?

I'm awaiting opinions on the driver choices and the feasibility of this project. Any input will be greatly appreciated.

Thanks,
Sébastien

[GM]

>One of my relative is very impressed with my previous DIY speakers and asked me to evaluate what would be the best drivers/crossover to clone the XRT22 speaker.
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Don't want much, do ya?

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>My first idea would be to ditch the whole passive crossover and go strictly active......

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But then it wouldn't sound 'right'.

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>Now comes the tough part. Which driver to choose? Forty six tweeters isn't going to be cheap if quality parts are chosen.

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Yeah, trying to find acceptable subs for custom units can be tough, especially when you don't have them to measure or a factory spec sheet.

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>The tweeter.......decent tweeter such as this one: http://www.d-s-t.com/peerless/data/811815.htm

What do you guys think? Will this tweeter be appropriate in a line array?

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What you need is this one, but it's discontinued, though maybe there's still some NOS 'out there': http://www.d-s-t.com.au/Data/Peerless/810665.pdf

If not, then if your choice has a plastic faceplate, cutting them down on two sides to get down to <80mm is an option. If not, then raise the XO point and choose an appropriate BW lower mids driver and if need be, wider BW LF/midbass drivers. You're 'close enough' if the XO point is <1/3WL of the c-t-c spacing, or ~13560"/pi/XO point.

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>How would I go around wiring 23 tweeters per side to get a driveable impedance?

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Same way they did, series/parallel and use series resistance to dial it in/flatten it out to extend its effective BW like they did.

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>The woofer choice turns out to be quite complicated too. I suggested this one for the mid bass: http://www.d-s-t.com/peerless/data/831709.htm

The sensitivity of this woofer might be a bit low to match the tweeters though. In an active system, this isn't a big deal but in a passive system it might be. Do you guys know of a better choice similarly priced?

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Not really, I don't keep up with what's available. Anyway, the system sens. is only 87dB/2.83V so its tweeter array is padded down. Frankly, I wouldn't try to match what they did beyond the basic concept, so choose what works BW wise, preferably with more sensitivity so you don't have to shelve the tweeters, and let the bass cabs be however big they need to be to get the desired response. You can always make them taller to shrink the footprint. The only criteria being that the lower mids driver be at ~face height when seated.

GM

[sreten]

I'd seriously advise against the whole project.

There will be a phenomenal dispersion discontinuity at 1.5KHz
that you will be utterly unable to do anything about, I'm talking
from experience of a 2ft ribbon crossed over at 600Hz to an
eight inch unit, here it will be much worse.

I suggest you investigate other line array designs that maintain
the line array dispersion down to much lower frequencies.

sreten.

[JonMarsh]

Like cloning the Macintosh XR290 system. This was a 3 way line array, with 12" woofers, a line array of 5" mids, and line array of tweeters.

OTOH, cloning a "Pipe Dream" system would be more contemporary.


Let's face it, the concept "cheap, small good line array" is an oxymoron!

A choice that might work better for the tweeters is one of the LPG neodymium magnet tweeters; such as the 25NFA, 26NA, and 26NAFM. The flange diameter is only 48 mm, and the cutout hole 46 mm.

I prefer the LPT 26T, but it's a more conventional sized part, 110 mm flange, 74 mm cutout. Nice aluminum plate, too; none of that cheap plastic stuff! But it would be a bear to squeeze them together...

[5th element]

Id agree with sreten on this, although im not as technically minded as he, yet! , this is going to be quite difficult to get right. Other then that another tweet to consider might be these from vifa.

http://www.d-s-t.com/vifa/data/d26nc-55-06c.htm

Very small faceplace and rectangular to allow mounting close together more easily.

ATC seem to like these tweeters very much, if they use a modified version I do not know, but still they must do something right.
$22.2 ea. This is going to be $1000 just on tweeters.

Thinking about this it might be worth talking to your friend and saying to them the idea is nice but you'd be better off with something else. This is a lot of money for it to go wrong. If they want line array Id suggest a tangband line array cause its not going to break the bank as much and will go much lower then tweeters.

Thing is I cant see that many cheap drive units is going to sound any better then a smaller amount of high quality ones, if not worse. Either way good luck.

Matt

[navin]

Originally posted by sreten
I'd seriously advise against the whole project.

I agree.

however you could make a system that could sound just as good and even look similar.

The Audax PR17 will do nicely for the mid. drop the 12" in favour of a JBL 2226. and top it off with newform or gold ribbon or something similar.

[sreten]

Originally posted by 5th element
Thing is I cant see that many cheap drive units is going to sound any better then a smaller amount of high quality ones, if not worse. Either way good luck.

Matt

Well I agree for most cases.

However you do get phenomenal efficiency so only smallish
high quality ampliifiers are required so by definition distortion
should be much below the norm at high levels.

You also get the effect of line source dispersion - which is
hard to describe - and an even more unusual presentatation
if the array is open baffle - I for one won't knock it for flea
power valve amplifiers - using some thing more substantial
for the bass end proper of course.

But as you say cost effectiveness is dubious, but IMO a mid line
array is the only way to get the best out of the long ribbons.

sreten.

[Mudge]

I have a design for an active clone of the Infinity IRS V saved on my HD somewhere. Not cheap by any means, but IMHO the original is a superior design to that McIntosh, which as Sreten points out, has a horrible discontinuity in the response at the crossover between line array and woofers. The IRS avoids that to some extent by having a ~6ft woofer line, so almost the entire frequency range will be within the nearfield, as opposed to that transition between nearfield and far field in the most sensitive region of human hearing

[Hybrid fourdoor]

Well, someones got to give some positivness.

The reviews for the XRT18,20, & 22's all have been great on Audioreview.

I say maybe cutting back on the tweeters might help though, as you simply don't need 23 per side. I'd say 10-12 about 24" off the ground would probably be plenty.

And maybe flanking them with smallish woofers (like 3"-4") to make the panels more fullrange.

[HiSPL]

What if you ditched the tweeter line altogether and used a B&G ribbon? You keep the overall "look" of the system without any of the complexity. You could easily cross from a woofer cabinet to the ribbon at anywhere under 500 hz. This would cost less than a bucket full of nice tweeters too.

-=Tim=-