# DIY LCR, THX ULTRA2 Projects



## Guest (Nov 28, 2008)

Anyone working on THX type LCR speakers. I am looking at building some LCR's modeled on the M&K 150's, Klispch 650's, Snell XA2900's. As far as i can tell M&K used allot of Vifa drivers, Klispch used OEM /Hifi drivers, any one know what drivers Snell used?

THX, EC


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## Aaron Gilbert (Nov 12, 2008)

Actually, most of the M & K satellite drivers were Peerless, including those in the S150, S125, and S85, just to name a few. The S150 were/are awesome speakers. 

Good luck with your project! The crossovers on the S150 are rather complex.


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## looneybomber (Sep 20, 2006)

ecronbach said:


> Anyone working on THX type LCR speakers. I am looking at building some LCR's modeled on the M&K 150's, Klispch 650's, Snell XA2900's. As far as i can tell M&K used allot of Vifa drivers, Klispch used OEM /Hifi drivers, any one know what drivers Snell used?
> 
> THX, EC


What are the THX specs again?

Off the top of my head I was thinking something along these lines.
90db 1w/1m
80-20khz

Is there anything else I'm missing, because if not, it won't take much to achieve those results.:huh:


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## thxgoon (Feb 23, 2007)

looneybomber said:


> What are the THX specs again?
> 
> Off the top of my head I was thinking something along these lines.
> 90db 1w/1m
> ...


The specs are not all made public, but wide horizontal dispersion with minimized virticle dispersion, high power halding and 12db/octave natural roll off below 80hz should get your sufficiently close in terms of design. Meeting those specs and building something that sounds good is the challenge :R


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## looneybomber (Sep 20, 2006)

thxgoon said:


> The specs are not all made public, but wide horizontal dispersion with minimized virticle dispersion,


Hmm, ribbon tweeters.

*high power halding*
With a high sensitivity, would the high power handling be necessary?


*and 12db/octave natural roll off below 80hz should get your sufficiently close in terms of design. Meeting those specs and building something that sounds good is the challenge*
So, some sealed 6's could accomplish a 2nd order rolloff at 80hz. Mini line array style?


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## Aaron Gilbert (Nov 12, 2008)

looneybomber said:


> Hmm, ribbon tweeters.
> 
> *high power halding*
> With a high sensitivity, would the high power handling be necessary?
> ...


Yes, two sealed 6" woofers could easily get the job done. M&K's S150 used two sealed 5.25" woofers. Certainly, if you have higher sensitivity, you won't need as much power to reach the same level. That said, most high efficiency drivers I'm aware of tend to have equal or higher power handling than less efficient drivers. So it's a win-win.


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## Guest (Dec 8, 2008)

Your going down the exact path I was thinking/ mini line array. Say 2 paralell rows of 4 drivers each. That is to say (4) 1" domes or ribbons aligned next to (4) 5"-6" drivers. I have a 130W ch. 7.1 to drive them with.

Does anyn have ideas on placement of acoustical foam (aka M&K) to better focus the highs?


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## thxgoon (Feb 23, 2007)

ecronbach said:


> Does anyn have ideas on placement of acoustical foam (aka M&K) to better focus the highs?


I believe the foam is used to minimizes edge diffractions... but somebody here knows more about this stuff than me. Using a line array as you are suggesting will help to focus the highs.


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## Aaron Gilbert (Nov 12, 2008)

ecronbach said:


> Your going down the exact path I was thinking/ mini line array. Say 2 paralell rows of 4 drivers each. That is to say (4) 1" domes or ribbons aligned next to (4) 5"-6" drivers. I have a 130W ch. 7.1 to drive them with.
> 
> Does anyn have ideas on placement of acoustical foam (aka M&K) to better focus the highs?


Well, if you're using an array of three tweeters vertically stacked, as in the S150, they use a piece of foam roughly 1" x 4" x 0.75" thick, placed horizontally across the bottom and top tweeters at the upper and lower edges of their faceplates. Although, I have a photo of a high end studio (might be Skywalker Sound - will have to check tomorrow) using S150, and just one of the front three has a different foam arrangement. It may be that they came as accessories, and the manual explains how to position them depending on your particular application. 

Also note that that S150 used a different tweeter in the center of it's three tweeter array, which received a different output from the crossover. So it's not strictly a line array where every driver has the same signal. The top and bottom tweeters do receive identical signals.


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## thxgoon (Feb 23, 2007)

Aaron Gilbert said:


> Also note that that S150 used a different tweeter in the center of it's three tweeter array, which received a different output from the crossover. So it's not strictly a line array where every driver has the same signal. The top and bottom tweeters do receive identical signals.


It depends on which model of the S150. In the powered professional version the center tweeter is open back transmission line, otherwise they are all the same. The center tweeter does get a different signal than the outer two but I'm not sure how this works. In the newer models you can select the vertical dispersion pattern of the speaker and I think this works by attenuating the outer tweets.


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## thewire (Jun 28, 2007)

thxgoon said:


> The specs are not all made public, but wide horizontal dispersion with minimized virticle dispersion, high power halding and 12db/octave natural roll off below 80hz should get your sufficiently close in terms of design. Meeting those specs and building something that sounds good is the challenge :R


The focused verticle directivity is no longer spec as that is left to the manufactor to have some freedom in their design philosophy. :whistling:


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## Aaron Gilbert (Nov 12, 2008)

thxgoon said:


> It depends on which model of the S150. In the powered professional version the center tweeter is open back transmission line, otherwise they are all the same. The center tweeter does get a different signal than the outer two but I'm not sure how this works. In the newer models you can select the vertical dispersion pattern of the speaker and I think this works by attenuating the outer tweets.


Well then there must be at least three versions. All the passive S150 I have seen use a different tweeter in the center - transmission line, as you say. It makes sense that adjusting the level of the outer tweeters would change dispersion, if we think of it as an MTM speaker, which inherently has somewhat restricted vertical dispersion when drivers are oriented vertically. Biasing the output towards the center driver will tend to give greater dispersion, because it's operating more as a point source, rather than as three independent sources, the two farthest apart being separated by about 8".


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## Aaron Gilbert (Nov 12, 2008)

thewire said:


> The focused verticle directivity is no longer spec as that is left to the manufactor to have some freedom in their design philosophy. :whistling:


Well that's very interesting, and good to know, thanks! I suppose THX decided that vertical dispersion wasn't as critical as they originally thought? Or, perhaps they were seeing a large decline in companies producing THX loudspeakers, so decided to relax the standards a bit to get more manufacturers back in the game? After all, THX is supposed to be a cohesive system, but if there aren't any speakers available to go with your fancy receiver or DVD player, that's not so good. I do wonder if it had anything to do with the actual sound. Way back when, I used to read criticisms of THX speakers as not sounding good with music, and much of this seemed to blame the unusual tweeter arrays and dispersion patterns.

That said, I've never met an M & K whose sound I didn't like for music, THX certified or otherwise.


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## BrianAbington (Mar 19, 2008)

Don't they also have to be able to play peaks up to 130DB with no distortion? Or was that just for movie theaters?

Not saying play movies at a constant 130 DB just have that ability.


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## Aaron Gilbert (Nov 12, 2008)

SQCherokee said:


> Don't they also have to be able to play peaks up to 130DB with no distortion? Or was that just for movie theaters?
> 
> Not saying play movies at a constant 130 DB just have that ability.


I'm not sure from where you obtained the 130dB figure. I don't even recall hearing that mentioned when reading about professional THX cinemas. It certainly does not apply to home THX, which specifies undistorted peaks of 105dB at the listening position from the satellite speakers. 

Moreover, 130dB in either case would be rather irresponsible and dangerous for higher frequencies. While our ears are able to withstand very high sound pressures at low frequencies for relatively long periods of time, even short durations at 130dB+ for mid and high frequencies can produce hearing damage. Just for reference, 130dB is considered the threshhold of pain. Short exposure to even 120dB+ can cause hearing damage.

In any case, the type of speakers under discussion don't have anywhere near the capabilities to produce those kind of SPLs.


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## thewire (Jun 28, 2007)

It's 105dB with Select, Select2, Ultra, Ultra2, and so on until they ever decide to change it. It is dependent on which size room it is meant to go into how loud the speaker will go. All THX certified subwoofers go to 115dB and feature less than 2% distortion. I have four in a 2300 cubic foot room. The idea is to have 20dB headroom and since I run mine without the plate amps they came with there is no limiters. This eats my 16dB or so headroom right off at the subs so I keep it about the same level they would otherwise be as a single sub.

Select and Select2 speakers can be 100Hz crossover and can feature monopole surrounds in Select. The front speakers do not have to be the same speaker also. Ultra 2 has 2 monopole rear surrounds next to one another in a THX setup. A THX setup has four surrounds, and these can also be on the side walls. Typical listening level is -10 with 105dB peaks distortion free and the room must meet THX requirements as well. Everything else is recommended to be THX certified in a THX setup also. THX even recommends THX certified wire and cables. Typical cost for a THX certified home theaters are from 40K to 200K. There is a proccess to setup or design the room and postion speakers and the screen also but you probobly knew that already.


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## DrWho (Sep 27, 2006)

Aaron Gilbert said:


> In any case, the type of speakers under discussion don't have anywhere near the capabilities to produce those kind of SPLs.


http://www.klipsch.com/products/details/kw-120-thx.aspx



Btw, the threshold of pain is dependant on frequency. I'd say it was closer to 120dB in the midrange, but really you shouldn't be above 110dB if you value your hearing (again, in the midrange). With low frequencies, the concern actually turns into a respiratory system issue - not so much your ears. We're exposed to very high SPL's at low frequencies all the time...we just don't notice it because we don't perceive low frequencies very well (like car doors slamming, wind, etc...)


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## Aaron Gilbert (Nov 12, 2008)

DrWho said:


> http://www.klipsch.com/products/details/kw-120-thx.aspx
> 
> 
> 
> Btw, the threshold of pain is dependant on frequency. I'd say it was closer to 120dB in the midrange, but really you shouldn't be above 110dB if you value your hearing (again, in the midrange). With low frequencies, the concern actually turns into a respiratory system issue - not so much your ears. We're exposed to very high SPL's at low frequencies all the time...we just don't notice it because we don't perceive low frequencies very well (like car doors slamming, wind, etc...)


We're talking about satellite speakers here, not a subwoofer - and dynamic satellite speakers at that, not horn loaded. I certainly agree with everything else, though.  

130dB at 30Hz from a pair of 12" subwoofers is pretty impressive, as is 122 dB at 20Hz. Sure, they're using 2000 watts to get there, but that still gives you 97dB at one watt for 30Hz, nothing to sneeze at.


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## DrWho (Sep 27, 2006)

My bad. Well there's always the KL-650 that goes with those subs...600W into 97dB is about 124dB-ish?

It's my understanding the Klipsch was heavily involved with the writing of the THX spec - and collapsing verticals was a favorite trick of Paul Klipsch. Roy Delgado has since moved towards constant directivity in both the horizonal and vertical. I can't help but wonder if that wasn't around the time when the THX spec "loosened up"?

I believe it was Roy who mentioned that the major criteria was low distortion, controlled polars, with low levels of power compression...something Klipsch has been doing for years and is why they stick to horns. The downside with DIY is that these specs are rarely if ever published.

Can you tell I'm a Klipsch fan?


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## thewire (Jun 28, 2007)

DrWho said:


> My bad. Well there's always the KL-650 that goes with those subs...600W into 97dB is about 124dB-ish?
> 
> It's my understanding the Klipsch was heavily involved with the writing of the THX spec - and collapsing verticals was a favorite trick of Paul Klipsch. Roy Delgado has since moved towards constant directivity in both the horizonal and vertical. I can't help but wonder if that wasn't around the time when the THX spec "loosened up"?
> 
> ...


I beleave that the vertical dispertion characteristics were loosened about the time Snell started releasing Ultra2, but I will see if I can find exactly when.


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## thewire (Jun 28, 2007)

I was not able to find it with the THX website, but the Atlantic Technology 8200 THX Ultra2 Speaker System in October, 2003 had relaxed the vertical focused verticle directivity. This was the same year that Snell released some Ultra2 so it might be safe to say 2003.


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## looneybomber (Sep 20, 2006)

Aaron Gilbert said:


> Although, I have a photo of a high end studio (might be Skywalker Sound - will have to check tomorrow) using S150, and just one of the front three has a different foam arrangement.


My sister's good friend, Sascha from http://www.sonicmayhem.com/ took a few pictures while he was at Skywalker. The studio monitors in the pictures I saw were B&W 802's. I'm sure they have more than one studio though.


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