# Mark Audio Drivers!!!



## mdrake (Jan 31, 2008)

I posted this in my Fostex thread but figured the little drivers deserved their own thread. 
I built a TL for the CHR 70's and they are INCREDIBLE!!! I was able to get a -3db point of 38hz using a transmission line enclosure!! It was amazing to listen to a 4 inch driver do 35hz!!!!!!!!!!!!! Of course I was using two per enclosure to get any kind of volume and will end up using 4 drivers per enclosure. I am going to order the alpair 6's next and give them a test run. THIS IS FUN.

Matt


----------



## dgilme (Apr 1, 2009)

*Re: Mark Audio Drivers!!!!!!!!!!!!!!!!!*

Got any pics? That sounds pretty interesting. I wonder if you could do a combination line array/TL..


----------



## Mike P. (Apr 6, 2007)

*Re: Mark Audio Drivers!!!!!!!!!!!!!!!!!*

Hey Matt, what are the high frequencies like on these full range drivers?


----------



## Anthony (Oct 5, 2006)

*Re: Mark Audio Drivers!!!!!!!!!!!!!!!!!*

I have a buddy who did a little 3" TL build a while back and they ended up sounding great. Volume wasn't very good, but sound quality was excellent from a single driver.

Please post pics, if you get a chance.


----------



## mdrake (Jan 31, 2008)

*Re: Mark Audio Drivers!!!!!!!!!!!!!!!!!*

Thanks guys for the positive feedback!! I was really excited to get the roll of so low!!!!!!!! 
I will get a couple of pics of both the inside of the box and the freq response curve. 

I am planning on doing 4 drivers per box so I guess that would qualify it as a line array of sorts. It is really everything I know slammed into one enclosure. It is kinda a TL/Line Array/Dipole/WMTMW lol. 

The top end sounded pretty good to my ears but did not look so hot in REW. It tends to break up in the higher freq. I will post a screen shot. I am planning on crossing them over somewhere between 500hz and 1000hz so I am not to concerned about their top end.  

If I make the baffle large enough I can avoid the baffle step compensation which will be a huge plus. If I cross everything over just right and build the baffles just right I might be able to avoid any notch filters as well but we will see. Each pair of alpairs will be in series which should bump up the efficiency by 3db and then all 4 will be compound loaded which should give me another 3db in theory, so they should be very efficient if all goes well. 

I need to get some good software to measure these things with.  Any recommendations? Thinking ether SoundEasy or LspCad. 

Matt


----------



## planet10 (May 27, 2007)

*Re: Mark Audio Drivers!!!!!!!!!!!!!!!!!*



mdrake said:


> I posted this in my Fostex thread but figured the little drivers deserved their own thread.
> I built a TL for the CHR 70's and they are INCREDIBLE!!! I was able to get a -3db point of 38hz using a transmission line enclosure!! It was amazing to listen to a 4 inch driver do 35hz!!!!!!!!!!!!! Of course I was using two per enclosure to get any kind of volume and will end up using 4 drivers per enclosure. I am going to order the alpair 6's next and give them a test run. THIS IS FUN.
> 
> Matt


Tell us more... pics, plans?

I've just been listening to the 1st set of EnABLed CHR -- a reallygood driver, utterly transformed.

dave


----------



## mdrake (Jan 31, 2008)

*Re: Mark Audio Drivers!!!!!!!!!!!!!!!!!*

What is an EnABLed CHR? The pics I have are of a really ugly box as it is just a test box.  I am using a basic TL straight tunnel enclosure. Nothing special yet, except for the nice low-end. 

Here is a screen shot of REW. Not sure why the top end is bad. Almost looks like REW was clipping. Any thoughts?


----------



## planet10 (May 27, 2007)

*Re: Mark Audio Drivers!!!!!!!!!!!!!!!!!*



mdrake said:


> What is an EnABLed CHR?


So far one pair exist and they are in my living room. EnABL is a very specific cone treatment.

More here: 
http://www.diyaudio.com/forums/showthread.php?s=&threadid=119676
http://www.diyaudio.com/forums/showthread.php?s=&threadid=100399
http://www.diyaudio.com/forums/showthread.php?s=&postid=1460032#post1460032


Is that an in-room response? It is far too flat to not have something wrong with it. 

How long is the TL? Cross-section? Driver offset?

dave


----------



## mdrake (Jan 31, 2008)

*Re: Mark Audio Drivers!!!!!!!!!!!!!!!!!*

Ya, the response looked funny to me as well. It is an in room response. I am going to wait for all for drivers to fill the enclosure and then take it out side and measure it as I don't have a chamber. I do have a very nice flat room though.  

That EnABLed looks like a TON of work is really worth it? 

Driver is offset from the beginning of the TL line by 3 inches and diameter of the line is twice the sd of one driver. Did not want to make the box to big.  

THANKS for the links!!!!!!!!

Matt


----------



## planet10 (May 27, 2007)

*Re: Mark Audio Drivers!!!!!!!!!!!!!!!!!*



mdrake said:


> That EnABLed looks like a TON of work is really worth it?


VERY much so.



> Driver is offset from the beginning of the TL line by 3 inches and diameter of the line is twice the sd of one driver. Did not want to make the box to big.


Then i'm pretty sure the measure is screwy. Without taking advantage of offset (which for a straight line is somewhere near a 3rd of the way down the line) either you should have a fair bit of ripple from the 1st harmonic, or you have stuffed it until it is close to aperiodic and the rolloff should be similar to a sealed box of the same size (or maybe you have a small, solid room)

Such a small cross-section is also suspect. Did you use any of the available tools to design it, or is it a classic line (ie not likely optimal)

dave


----------



## mdrake (Jan 31, 2008)

I have built many a TL but this is my first journey back into the world of TL in 15 years and there are now tons of resources on TL's. Back when I used to build them we did it with lots of math and trial and error but these new resources are making it easier to get right the first shoot out. Which saved me a ton of time, well maybe not a ton as I had to do a lot of reading. 

I am not sure what you mean by offset? You can't use fancy words like that to a guy who comes from the old school TL world. :bigsmile: If you mean are the drivers mounted in the middle of the Line then the answer is a yes and no.  Two are in the middle of the line and two are at the beginning of the line to try alleviate the ripple in both the 1st and 2nd harmonic, which looks like it worked up to 500hz. Which should be just below the fourth harmonic if my math is correct.  

I do use a lot of stuffing both wool and standard pillow stuffing. I have also had good success with sound deadening foam.  

Not sure why twice the sd of the line diameter would be suspect except for the fact that I am using a total of 4 eventually but during the measurements I used two which should be spot on. From my experience I learned and the reading I have done recently seemed to agree that line diameter should be sd for a straight line TL. Do you do something different? Is there a different way to do it now. 15 years has passed by.  

Matt


----------



## mdrake (Jan 31, 2008)

Going to have to do some reading on the EnABLed stuff. Did you measure the Theil parameters after you did the modification did it mess with the Mms? This sounds interesting to say the least.... 

Matt


----------



## planet10 (May 27, 2007)

mdrake said:


> I am not sure what you mean by offset? You can't use fancy words like that to a guy who comes from the old school TL world. :bigsmile: If you mean are the drivers mounted in the middle of the Line then the answer is a yes and no.  Two are in the middle of the line and two are at the beginning of the line to try alleviate the ripple in both the 1st and 2nd harmonic, which looks like it worked up to 500hz. Which should be just below the fourth harmonic if my math is correct.
> 
> .... Not sure why twice the sd of the line diameter would be suspect except for the fact that I am using a total of 4 eventually but during the measurements I used two which should be spot on.


Offset is the distance of the driver from the closed end of the line. from memory 0.3411 gets you cancellation of the 1st undesirable harmonic.

Sd actually has no direct relationship to the required cross-section. This is determined by Vas & Qt. I've not time to run the numbers thru King's tables, butthat is always a good starting point.

How long is your line?

dave


----------



## mdrake (Jan 31, 2008)

> Sd actually has no direct relationship to the required cross-section. This is determined by Vas & Qt. I've not time to run the numbers thru King's tables, butthat is always a good starting point.


 THANK YOU VERY MUCH for that info!! That is new to me. Do you have a copy of kings tables??? 

So using 4 drivers then two of the drivers are very close to the .34111. 

Wow, I had no idea TL's had come this far! This is very, very cool. 

Line length is 48 inches based of a the 1/4 wave of 70hz. But the way the box is designed the second line length is would be 96 inches. Here is a drawing since the box is so UGLY.


----------



## planet10 (May 27, 2007)

mdrake said:


> THANK YOU VERY MUCH for that info!! That is new to me. Do you have a copy of kings tables???
> 
> 
> > My TL site: http://www.t-linespeakers.org/
> ...


----------



## mgboy (Jan 17, 2007)

All that measurement shows is that is was clipping the entire measurement. Try turning the volume down, or the meter level up.


----------



## mdrake (Jan 31, 2008)

Martin's tables are the 30 pages I read. I just looked at the author. 




> So the actual line length is twice as long as it should be. You actually get less bass if you make the line too long.


Looking at my design do think the woofers are seeing the full 96 inches or are they just seeing the 48 inches of line length? 

I was planning on crossing them over and letting a mid range and tweet take over the highs. 

I have had issues with using more than one full range driver per baffle. So, I was not planning on going that route. 

I will check out your site and THANKS for the info!!!


----------



## mdrake (Jan 31, 2008)

It is funny with all the fancy math and table the basic fundamentals don't change much.  

Any idea how to locate the pc parameter? I figured out everything after reading the document tons of times but can not find the pc parameter that is needed to finish the calcs.  
His explanation of pc is "*wave specific acoustic impedance*" .. any idea how to find it? :gah:

Matt


----------



## planet10 (May 27, 2007)

mdrake said:


> Looking at my design do think the woofers are seeing the full 96 inches or are they just seeing the 48 inches of line length?


Yes



> I was planning on crossing them over and letting a mid range and tweet take over the highs.


Why would you get a CHR70 and then ruin it by adding a mid & a tweeter. I could see using it as a midtweeter with a bass driver.



> I have had issues with using more than one full range driver per baffle. So, I was not planning on going that route.


I do as well, you have to get creative if you want to use more than 1. Here is a good way to use a pair...










dave


----------



## mdrake (Jan 31, 2008)

> Why would you get a CHR70 and then ruin it by adding a mid & a tweeter. I could see using it as a midtweeter with a bass driver.


 Because I am nuts. :coocoo::dumbcrazy: No I am looking to build my own version of the ML's that hand on the wall. A thin speaker that still can go low without a sub but is designed to be used from 60hz up. That and I have always been partial to full range speakers especially were voices are concerned. Besides what other speaker is going to give this kind of sound quality for the money. :bigsmile:

I LIKE you creative design on overcoming the baffle issue with dual full rangers but what about of axis phase response.  

Do you have any idea were I find the parameter pc that Martin King is referring to in his formulas? If I could get that one parameter I would know how far off my design is. 

Just got the active crossover/loudspeaker management unit to go all active, no more coils or caps. :yay2: 

If they are seeing all 96 inches thin it back to the drawing board. I will test and see. 

THIS IS A FUN HOBBY!!!!!!

Matt


----------



## mdrake (Jan 31, 2008)

I compared 4 alpair 6's up against 2 CSS SDX7's in WinISD & the results were surprising. At 55 watts I can get 3 db more out of the 4 alpairs than I can out of the CSS and they hit Xmax at almost the same time. So, with the alpairs on sale I can get more bang for my buck and get more efficiency by using 4 alpairs vs. 2 midbass drivers and I can use a shorter line length. 

Back to reading Martin Kings research.... Now were did he hide that pc parameter..... 

Matt


----------



## planet10 (May 27, 2007)

mdrake said:


> I compared 4 alpair 6's up against 2 CSS SDX7's in WinISD & the results were surprising. At 55 watts I can get 3 db more out of the 4 alpairs than I can out of the CSS and they hit Xmax at almost the same time.


The SDX7 (needs at least minimal treatment) is one of my very favorite woofers. No way can the Alpair 6 keep up. Plus these 2 speakers aren't directly comparable... the highest i use the SDX7 is 333 Hz, and the A6 is best suited as a midtweeter. Matter of fact i have a FAST half-built that will use an Alpair 6 with an SDX7 under it. Something like Tysen (http://www.diyaudio.com/forums/showthread.php?s=&threadid=144099).

BTW: i'll only use the SDX7 in a sealed box.

dave


----------



## mdrake (Jan 31, 2008)

> BTW: i'll only use the SDX7 in a sealed box.


Have you tried it a in a TL? From what I can tell it would work "using old school method's as I can't fully calculate Mr. Kings formula's yet. I can program CSS and Flash but can't a calculate a stupid TL formula. I am going to go hang out in the dunce corner for a while. 

Glad to know you have had good success with the CSS woofer. Can't wait to get my hands on a pair. The group delay looks really low on the CSS wonder what she would do with a Link Transform circuit. This could get real FUN real FAST. 


Matt


----------



## planet10 (May 27, 2007)

mdrake said:


> Have you tried it a in a TL?


Yes. I have push-push SDX7 TL woofers in my living room as we speak (with sealed CHR70eN sitting on top for that matter). Woofers are disconnected at the moment as we complete evaluation of the treated driver). I had to stuff them till aperiodic to keep them from unloading real low. They are going to come out and go into a sealed box.

dave


----------



## mdrake (Jan 31, 2008)

You treated your beautiful woofer. :foottap: Kidding :R You will have to let me know how that turned out. 

That is the problem I found with trying to TL woofers was line length and the unloading. That is why I was using Focal and now Mark Audio full rangers in my TL's. 

I am pleased with the results of the mark audio drivers in TL but I think I may use them in my family room and build some serious speakers using the CSS drivers for the HT. Thanks for the conversation it has really got me thinking. TL's have come a long way in 15 years. 

Matt


----------



## planet10 (May 27, 2007)

mdrake said:


> You treated your beautiful woofer


IMHO they aren't usable without at least minimal treatment to bond the carbon fibres together. Bob has talked with the factory about getting it done there for the next run. I of course EnABL all my drivers to take them a stage further.

dave


----------



## mdrake (Jan 31, 2008)

Won't the Enable process increase the cone weight and hurt the transient response? 
Why do you say they are not usable unless modified. Do you mean because carbon fiber is a little rough around the edges. "Pun intended" :bigsmile: Guess I will order a pair and see what they can do. What measurement software do you suggest?

Matt


----------



## planet10 (May 27, 2007)

mdrake said:


> Won't the Enable process increase the cone weight and hurt the transient response?


Mass added is very small... and it wouldn't affect transient response as that is largely tied to motor inductance. Google Dan Wiggins, John Janowitz or Nick McKinney on the subject. 



> Why do you say they are not usable unless modified. Do you mean because carbon fiber is a little rough around the edges.


Take an SDX7, hold it close, and run the back of your fingers (fingernail tips) across the cone. Then the same with your findertips.

More than a little rough. Bonding the fibers will greatly lower the noise floor and it measures flatter and smoother at the top end of the band (800-1.15k)

dave


----------



## mdrake (Jan 31, 2008)

Wow, just when you think you know something you find out you don't.  Just goes to show the old saying that half of what you know is wrong. I will have to some googleing on transient response and cone design. Seems to me that a speaker manufacture would take great pains to make sure there cones are properly setup, so I don't understand the need to mess with their work but.......

I would love to measure the before and after and that is exactly why I need to get some measurement software!! This sounds more like the old "Magic Cable" magic trick than real world application as I cannot see how the human ear is going to pick up the difference in a carbon fiber woofer treated or not treated. :bigsmile: But I could be totally wrong. Only one way to find out.

Over the years the trial and error method of speaker building has worked but I would love to get more into the exact science of this hobby. 

Matt


----------



## planet10 (May 27, 2007)

mdrake said:


> I cannot see how the human ear is going to pick up the difference in a carbon fiber woofer treated or not treated.


You don't give your ears enuff credit.

Differences in FR are clear, but that is the least of the benefit. (Red is treated)










dave


----------



## Mike P. (Apr 6, 2007)

Dave, is that's an in room measurement?


----------



## planet10 (May 27, 2007)

yes


----------



## mdrake (Jan 31, 2008)

What enclosure were those in when that measurement was taken? 
Does look like that coating made a difference especially in the high-end for the freq.

Matt


----------



## planet10 (May 27, 2007)

I believe they were in a 1 ft^3 curvy PE box (Al Wooley of RAW made these measures). You are only interested in stuff over 200-300 Hz.

dave


----------

