[tabrink]

  I am just really impressed with what a nice guy AJ is and his personal attention to details and prompt replies to inquiries!
Looking forward to hearing the genius!

[andy19191]

AJ, I am curious about the design decision to use a bass-mid/tweeter crossing at 200 Hz rather than a mid/tweeter crossing around 500 Hz?

[doug s.]

AJ, I am curious about the design decision to use a bass-mid/tweeter crossing at 200 Hz rather than a mid/tweeter crossing around 500 Hz?

you do realize that this is a coax driver, and its low end goes quite low?  this way, the design can use a powered woofer almost like a subwoofer...

doug s.

[andy19191]

you do realize that this is a coax driver, and its low end goes quite low?  this way, the design can use a powered woofer almost like a subwoofer...

For a while now I have had an on and off project (mainly off) to DIY a small 3 way for the shelf above my desk. The original intention was a sealed 8", small mid and tweeter in a waveguide but I was having problems getting things to fit. A few days ago a chap that installs speakers showed me the KEF mid/tweeter from the R series and this would fit quite nicely. Like Genelec, KEF seem to follow conventional thinking for a 3 way and crossover around 500 Hz but AJ has opted to use the bassmid/tweeter from the Q series and crossover much lower. I am interested in his objectives and the pros and cons as he sees them.

[AJinFLA]

AJ, I am curious about the design decision to use a bass-mid/tweeter crossing at 200 Hz rather than a mid/tweeter crossing around 500 Hz?

Hi Andy,
Many reasons, one of which is the diffraction losses of that sized baffle and the way it can be used to shape the total acoustic response (driver/filter/baffle). No need to cross the KEF driver higher due to it's inherent performance characteristics/strengths, ditto for the subwoofer.

cheers,

AJ

[ricardojoa]

Hi Aj, what do you think about raal tweeter? Would it be possible to integrate the raal in to this design working as a 4 way so the coaxial still remain but the raal will handle the higher notes.

[jimdgoulding]

Were I in the market and for my size room, I would DEFINITELY give these a whirl.

[andy19191]

Many reasons, one of which is the diffraction losses of that sized baffle and the way it can be used to shape the total acoustic response (driver/filter/baffle). No need to cross the KEF driver higher due to it's inherent performance characteristics/strengths, ditto for the subwoofer.

Thanks for the reply which looks a bit like a manufacturers answer. Are you still alive on any of the DIY forums?

[doug s.]

Thanks for the reply which looks a bit like a manufacturers answer. Are you still alive on any of the DIY forums?

andy, you obviously have not met aj, or read posts he's made to the forums - even tho he's technically a "manufacturer", he does this speaker thing as a hobby.  he's an enthusiast first and foremost, and he will give you only straight answers.  no gobbledygook here.  he's about the straightest shooter you will find, here or anywhere, imo.

doug s.

[AJinFLA]

Thanks for the reply which looks a bit like a manufacturers answer. Are you still alive on any of the DIY forums?

Well, I am a manufacturer, though the answer is accurate and to the point. What do you think might be missing? Did you understand it?

[AJinFLA]

Hi Aj, what do you think about raal tweeter?

Hi Richard,
Very nice sound, expensive, drops right into the cookie cutter.

Would it be possible to integrate the raal in to this design working as a 4 way so the coaxial still remain but the raal will handle the higher notes.

Sure. You pay, I build. 
Seems like a waste to be used as such. Have you heard either an M1 or RAAL based design to determine whether this would be a desired inclusion? A big part of why the M1 sounds the way it does...is due to the design as is. Controlled directivity in ever direction. To be placed in real rooms with real reflections...in every direction.

cheers,

AJ

[andy19191]

andy, you obviously have not met aj, or read posts he's made to the forums - even tho he's technically a "manufacturer", he does this speaker thing as a hobby.  he's an enthusiast first and foremost, and he will give you only straight answers.  no gobbledygook here.  he's about the straightest shooter you will find, here or anywhere, imo.

I have never met AJ but we have occasionally corresponded on other forums in the past. I suspect he will readily admit to being more restrained/responsible in his posting now he is a manufacturer and good luck to him. Whether that makes him a straighter or more bent shooter on an audiophile forum is perhaps debatable.

[satfrat]

I have never met AJ but we have occasionally corresponded on other forums in the past. I suspect he will readily admit to being more restrained/responsible in his posting now he is a manufacturer and good luck to him. Whether that makes him a straighter or more bent shooter on an audiophile forum is perhaps debatable.

Well from your beginning 4 posts here on AC, restraint doesn't seem to be an issue with you. 


BTW, welcome to AC! 


Cheers,
Robin

[doug s.]

I have never met AJ but we have occasionally corresponded on other forums in the past. I suspect he will readily admit to being more restrained/responsible in his posting now he is a manufacturer and good luck to him. Whether that makes him a straighter or more bent shooter on an audiophile forum is perhaps debatable.

it's debatable, only if you like to argue.   

i have been following aj for a long time here on a/c, and and, w/o a doubt, you won't meet a straighter shooter, mfr or otherwise.  if he shows restraint/responsibility, it is not because he's not a straight shooter, but because he may be more cognizant of not wanting to insult others when he knows they're full of it.  i have found it pretty easy to read between the lines, most of the time, tho... 

ymmv,

doug s.

[AJinFLA]

Whether that makes him a straighter or more bent shooter on an audiophile forum is perhaps debatable.

Again Andy, if you didn't understand, or did but need further info, feel free to ask. No secret sauces or magic in any of my designs. Just knowledge of the fundamentals and application.
Or feel free to use 500hz.

[andy19191]

What do you think might be missing?

More on why you made the unconventional choice of a midbass rather than a mid in a 3 way. The radiation pattern is one parameter but it is only one of a set which will of course be weighted by your objectives, constraints and other design choices.

Did you understand it?

I believe I understood what you said but I have yet to weight the significance which requires the comparison of a few simulations.

[andy19191]

Again Andy, if you didn't understand, or did but need further info, feel free to ask. No secret sauces or magic in any of my designs. Just knowledge of the fundamentals and application.

That is good.

Or feel free to use 500hz.

If I opt for the R series mid/tweeter coaxial I suspect I will be forced to use something around 500 Hz because it is not a midwoofer/tweeter.

[AJinFLA]

More on why you made the unconventional choice of a midbass rather than a mid in a 3 way.

That one was easy. KEF made it for me, by supplying a midbass driver. As such its parameters are optimized for midbass reproduction, sacrifices made to sensitivity and traded for LF capability. A large (2") VC and decent displacement capability also contributes to the filter choice. Hopefully you are advanced enough in DIY knowledge to know the full scope of crossovers, the electrical filter portion and the actual acoustic response as determined by the driver/baffle combination.

The radiation pattern is one parameter but it is only one of a set which will of course be weighted by your objectives, constraints and other design choices.

That would have been a minor consideration at those frequencies. Not unconsidered, but minor.

I believe I understood what you said but I have yet to weight the significance which requires the comparison of a few simulations.

The baffle diffraction losses (aka "Baffle step") is fairly straight forward. How you choose to address isn't always. I chose to address it in the system design, without throwing what I deemed as unnecessary components and performance limiting. I chose to use the combination of total acoustic response of each driver in that enclosure to account for the filter choice. Hence, around 200hz. Keep in mind these are not intended for console use, but free standing. In a room. Where the Schroeder frequency rarely exceeds 300hz. That too plays a role.

cheers,

AJ

[Saturn94]

it's debatable, only if you like to argue.   

i have been following aj for a long time here on a/c, and and, w/o a doubt, you won't meet a straighter shooter, mfr or otherwise.  if he shows restraint/responsibility, it is not because he's not a straight shooter, but because he may be more cognizant of not wanting to insult others when he knows they're full of it.  i have found it pretty easy to read between the lines, most of the time, tho... 

ymmv,

doug s.

+1!

BTW, I've read candid posts by AJ that have ticked off a few people; some don't like to hear the truth or want an education. 

PS - My pair of SAM1s arrived today.

[Letitroll98]

Thanks for the reply which looks a bit like a manufacturers answer. Are you still alive on any of the DIY forums?

Well, I am a manufacturer...

Welcome to AC Andy.  Just as a note of explanation, AJ, being a manufacturer, is under certain restrictions to not promote or advertise his products in the public circles on AC.  In threads mentioning his products he can only answer direct questions about them.  He does a great job of this and I've been required to do zero moderation of his posts.  Being new here you may not realize right off the bat that a great deal of this site is commercially based with sponsor manufacturers paying a fee to host their own circles in which they freely promote their products.  On the public circles the restrictions to manufacturers posting about their products are much tighter than on many other audio forums, such as the DIY ones.  I'm sure AJ would be happy to be his old self and go toe to toe with you about speaker theory on a more general thread than this one.