ATC SM75-150S Dome Mid Measurement Data

I know what you mean about the driver suiting certain types of music, but from what I've heard so far, and I'd stress that my exposure has been pretty limited, I think the driver is very faithful to the input signal. It can sound less exciting and 'busy' compared to other speakers but that could simply be a function of low distortion - it doesn't seem to congest or 'block up' when played loud or presented with a complex, dense mix.
I've heard it sound warm and full on one track and dryer and more clinical on another - truthful the the music in other words.

Definitely speak to Simon as he must have heard pleny of different tunes through the Mangers.

PS: I think Simon said they go even lower than 300Hz though spl will clearly be limited.

 

Thanks for the honest appraisal Bottleneck.

£1k is a lot of money to dump on a pair of drivers that seem to be going against what I perhaps look for in a loudspeaker.

 

Many thanks again for the input Rob.

Its sounding more and more like this isn't really my cup of tea. I know its tough going trying to read into opinions and often I take away a different impression than what you(or anyone else) was trying to convey.

My impression so far is of a very accurate driver and I Simon did email me some distortion measurements which look to be about average and on a similar sort of level to the ATC. But it seems some of the sparkle and musciality has been perhaps removed, please correct me if I'm wrong?

Simon did say this driver would suit a studio monitor well but perhaps too well for listening with the intent of involvement and through a wide genre?

Hope I'm not over stepping the mark on these tentative assumptions and would love to hear other remarks on these unusual and groundbreaking drivers.

 

Shin,

I've had another look at those photo's and my only question is - how the hell did you get that quality of finish. Has ATC actually seen those things themselves by the way???

I don't really care how they sound to be honest!

 

I'm looking at a whole host of other drivers.

But I'm pretty sure that these next speakers will be featuring a pair of 15" TAD drivers per side (probably the TL-1602 or TL-1601a). I remember hearing these in some speakers(sorry can't remember the name/model) a few years ago now at Bristol. The dynamics and transparancy of the sound was DAZZLING.

I'm really looking to stick to a 2-way so maybe crossing to a wideband ribbon such as the Raven 3.2MMX, Aurum Cantus G1. The Raven would allow to cross at 800hz and paired with the two TAD's would offer a high sensitivity loudspeaker that would, theoretically considering the sum of the parts allow for a pretty special loudspeaker given a good implemention.

 

Thanks for the comments Andy.

I wrote a little article to show how easy it is to do:

You don't need hundreds of pounds worth of kit and product to get a very nice looking finish. I use a Makita palm sander which cost around £45, I know some will look on in horror as I mention I use this to flat back all the orange peel left over after spraying but it works great and does the job in quarter of the time it takes to sand by hand, this is absolutely indispensable if your A. lazy or B. have large cabinets - I fit both of those I find that a decent quality 1/4 sheet palm sander is more preferable to a larger and heavier 1/2 or 1/3 sheet sander, the obvious reasons being more lightweight and you will appreciate that after holding it for a couple of hours! And it also provides more finesse and less vibration both of which make the final finish that bit better.

After the palm sander comes the sanding paper and I'd highly recommend you buy the very best you can find. For me that's 3M silicon carbide 2000grit, this stuff provides a brilliant cutting action but only leaves very light scratching of the surface which makes the rubbing compound and polishing steps that much easier. Its also rather forgiving and only takes off a very small amount of paint material providing you don't do something daft like stand on the sander whilst flating out the finish, so what this means is you can easily control where to take more paint off whilst avoiding going too far and pushing through the paint, which you absolutely don't want because it means you just wrecked all your hardwork and you'll need to re-spray.
Just another quick note, the better the paper the better the cutting action, buy cheap and you'll likely get a naff and scratched to hell finish that takes twice as much rubbing compound to fix. Better sand paper means less work and a better finish. Cheap sand paper also tends to fall apart or becomes ineffectual after a few minutes of sanding. I can't stress enough about the decent sand paper thing, one of the very best there is would have to be 3M 'purple' line, which are easily identified as they're purple.

Here's the sand paper I use: http://www.paints4u.com/ProductDetails.aspx?productID=6030

All sanding is done wet and all I do is use a softish cloth peroidically soaked in water and apply this to the cabinet and then sand with the palm sander. Regularly wet the surface to keep it both clean and also not to allow the removed paint material to start to gather and clog, you'll know when this happens because the sander doesn't glide so easily and starts to dig into the work.



The rest of the stuff that I use is as follows:

Cutting compound - Farecla G3: http://www.paints4u.com/ProductDetails.aspx?productID=2789

Ultra Fine Cutting Polish - National Grade-A: http://www.paints4u.com/ProductDetails.aspx?productID=536

And these: http://www.paints4u.com/ProductDetails.aspx?productID=5577

Be sure to buy/use at least 4 of these finishing cloths. You'll need one for applying the G3 cutting compound, another to rub off the dry residue, one for the ultra fine cutting polish and another to wipe off and buff after using that. Last thing you want is to start using a cloth that has been used to wipe G3 rubbing compound off the work only to use it to 'try' and buff after polishing, all you'll do is scratch the work to hell. Keep them seperate and you'll get a much better finish. Again, be sure to get some decent soft and lint-free finishing cloths, the best ones leave no swirl marks, those linked to above are in this catagory and I recommend them.
Another important note is make sure they're clean with no dried on cr@p, dust or grit before you start, most are machine washable too.

Step1:

You'll start off with something that looks like this:



Notice all that orange peel, it has a decent gloss but the reflection is very distorted by the surface imperfections cause by the orange peel. You can get a *much* better looking finish than this with a little work.

First thing to do is get the palm sander, your decent quality 2000grit sanding paper and wet sand like I mentioned above. Go light with the sander and move in horizontal full length strokes until you've covered the work and then move in vertical strokes, keep alternating between these - the reason for doing this is to keep the surface more uniform as a high gloss finish will highlight even the smallest surface level imperfections. You don't have to get it perfect, or maybe you do but providing you take reasonable care you'll get a better looking piece.

After you've made your first couple of passes you'll notice the dull sanded surface and the glossy untouched pits. Ideally we want rid of every single one of those glossy pits, so keep sanding (carefully!) until all you can see is a dull surface with no gloss pits, when you get to this stage you'll know you have a 'flat' surface and the orange peel has been removed. Be sure to switch to wet sanding by hand on tricky bits like the bevels you see on the example photo's and only use the palm sander for larger surfaces.

Replace your sandpaper when you notice its not really doing much and always take more care with fresh sand paper.

After you've done all that you'll have something that looks like this:



IMPORTANT: Be sure to sand the entire cabinet in this manner before moving onto step2! This ensures that you don't undo work done by rubbing compound etc. with a slip of the sand paper - or in otherwords; you don't mind if you scratch an already scratched surface but if you've spent good time and elbow grease polishing and rubbing a gloss finish, scratching it will matter So complete each step for the entire cabinet first and then move onto the next.

Step2:

Clean down the work using soapy water to remove any sandpaper grit and then wipe dry.

Now its time for the rubbing compound. I use the Farecla G3 stuff and it works well, there are others so choose a good quality one if this isn't available.

The first thing to do here is wet one of the finishing cloths mention above and wring it out so its just damp. Apply a *small* amount of cutting compound and get to work. I use use horizontal and vertical motions but anything works here so do whatever feels most natural to you. When you first start working the compound into the paint you'll notice its quite gritty and then after some rubbing you'll see it turns to a fine paste and it becomes harder to work the surface - this is good! Keep at it until the rubbing compound virtually dissappears from the surface of the paint and is instead, a dry residue on the finishing cloth - this is the correct way to apply rubbing compound and NOT how I and most others did when we first started with all this ie. apply loads of rubbing compound and then just scratch the hell out of the surface because it never really brakes down into the fine paste/dry residue I mentioned above. Remember that rubbing compound starts out coarse but gets finer as you work it more.
Once you get to the point where you're working just the dry residue then apply more rubbing compound to a clean part of the finishing cloth.

IMPORTANT: Cutting compound is quite harsh when freshly applied, be sure to exercise extra care when dealing with corners or sharp angles as you can push through the paint and ruin all the hardwork you've done so far

After the first pass my work looks like this:



You can clearly see a reflection now but the surface is still very scratched leaving a misty reflection that looks pretty poor.



This is after 4 passes:



You can clearly see the reflection now and the scratches remaining are light and only visable up close, its at this stage that the rubbing compound has done its job and we must move onto something with a very fine cutting action such as the Grade-A polish if we want to better the shine and contrast of the reflection and also fully remove the scratches.

Step3:

This is the where we apply the very fine cutting action polish. I use National Grade-A polish and again I highly recommend it but as always there's tons of different brands so just pick something well respect and that is described as having a mild or fine cutting action on the label.

The procedure here is very much the same as with the cutting compound ie. apply in small amount and work in thoroughly - read step 2 for a little more info.

This is the result after 2 passes:



Now its really looking well with lots of contrast to the reflection. Still some very fine swirl marks but these get less and less with each pass.



And finally this is the end result after 6 passes:



The end result is a pretty awesome gloss finish that looks every bit as good as you'd see on an expensive car. Virtually all the swirl marks have gone and there's definitely no scratches.

In the end this is about 95% close to what a proffesional would produce and all it took was some time, care and enthusiasm.

 

Ant, still no sign of that sandpaper :MILD: I can wait... I'm at the orange-peel stage but I think having done it with spray-cans rather than a proper gun and maybe not having a thick enough lacquer coat it might not survive a sanding anyway.

 

A bizarre statement bub given that you choose on the basis of glossy brochures.

 

Shin, have you looked at the raal ribbon as well?

 

Dust is another annoying culprit.

I do have a variable speed polisher but it seems to be a little rough at times, its probably a case of me not using it correctly.

 

I wonder how the ATC mid dome compares to ATC's 5" and 6" mid-bass units (the latter as used in my Active 20s), which have dome units built into the woofer. For one thing, the dome on the 5" midbass is smaller than the 3" dome of the standalone mid driver.

Dunc

 

Unless the dome in the 5" driver is suspended from the rest of the woofer cone (like a ‘whizzer’), I doubt it will act anything like a separate mid-dome as the rest of the woofer will damp the high-frequency action. Still it would be interesting to see. I suspect the main thing would be a longer decay rate.

 

Well along with picking up my phono stage yesterday, I got the chanve once again to hear the ATC SCM50ASL - this time with the newest tweeter - in a rather neat system comprising TEAD gear and a Rock turntable. Whilst the results were better than they were when I owned a pair at home, I would still say there is something I cannot get on with. I thought, given the BS being thrown around on the internet at the moment it might be worthwhile reminding people of Shin's findings regarding the frequency irregularities of the midrange dome, and in addition the driver resonances and their proximity to the pass band in the ATC active monitors.

For comparison purposes, and because Keith get's a lot of stick for having the temerity to suggest the ATC can be bettered, I dug out the measurements TAD supply with the 2404 - with particular interest surrounding the performance of their midrange drive unit, the TD-4003.



Jon at BelCanto noted the following regards these measurements - comments I would concur with

And here is the FR plot for the 4003 and 703 taken in situ showing +/- 1db from 1khz to 18khz.



Hopefully this will help some ATC owners to understand why some of us have issues, however minor, with the performance of their monitors, and show a way forward, in which they can be objectively improved upon.

 

How does the new rock sound?

 

LOL! Mike, the "wind-up merchant" description is spot on. You've given me a genuine laugh, thanks.

 

P.S. The mid dome supplied OEM is not the same as the one used in ATC monitors.

More info here:

http://www.gearslutz.com/board/high-end/10776-opinions-atc-scm20-50-a.html

 

Bub, sorry but as I am very good friends with a long standing ATC OEM client, that internet gossip is misinformation.

There are only two versions of the ATC dome, the newer higher efficiency unit having been developed specifically for the SCM range of monitors. It is available OEM. Some choose not to use it however, preferring the lower sensitivity unit.

There is so much disinformation on internet forums regarding the ATC's I'm afraid. Which is a shame. I just get fed up with reading inaccuracies from a small number of ATC devotees. They are undoubtedly a good loudspeaker - especially when turned up loud.

I merely posted the above to correct some of the foolish things being said elsewhere at the moment. There are valid reasons for a number of people rejecting the SCM monitors - the most likely of which IMHO are the resonances just outside of the passband. The small bump at 1khz will also be contributing to their love of high volume levels and their comparative disappointment below 85db. The message is they are very good loudspeakers, but people hearing better ones are not deaf or addicted to colouration. If they were, then the vast majority of studio engineers and mastering engineers would be guilty of such failings - hardly likely when you think about it is it Bub?

 

Even if its true (which I doubt), its most likely they just test them all and select the best for themselves - which is unlikely to affect shins observations in the slightest.

 

I thought the new "SM" was a great improvement! You however bub havent moved forward at all.

 

Thanks BBV.

PFM? Yes it has improved hasn't it.

The main problem over here Bub is I've posted a set of objective measurements that you can't argue with - even if you wanted to - without making yourself look a teensy bit hypocritical. A bit like the CDX2 fiasco ;-)