folded in speaker alignment

[Tom Loizeaux]

I have been wondering about the possible negative affects of mounting drivers on a folded-in baffle.
Someone one told me not to do it because the waves would collide and that would be a bad thing. I've seen photos (some included here) of a number of pro-quality boxes that use a folded-in baffle.
I built a pair of dual 10 cabinets (last photo) where I used a slight folded in baffle. These are mid cabinets that handle 500 to 2.5K, and as I walk around them at 25 feet or so away from them (they're for a PA stack) I don't hear any abnormal patterns.
What is the acoustic theory behind crossing driver beams? Any thoughts?

Thanks,

Tom

[ralphs99]

Hi Tom,

The folded baffle will have no negative effects. In fact, it has a few positive ones.

It brings the acoustic centres of the two drivers closer together which helps to reduce the interaction of the drivers. At the very long wavelengths typical of low frequencies the effect will not be noticeable.
However in a two way system with a crossover point of 500Hz or more, where the wavelength is of a similar length to the distance between drivers, the angled baffle will reduce lobing. Also the directivity patterns of the drivers can be made complimentary to give a more even power response.

An angled baffle will also be more rigid.

If you don't mind the extra woodwork, it sounds like a good idea.

Nice woodwork BTW!

Cheers, Ralph

[duaneage]

At certain frequencies there wil be different lobes to the response pattern. If these lobes fall out of the range the system operates in it does not matter.

Advantages include getting larger drivers into a smaller area for space savings, increased output (slightly) due to megaphone effect, looks way cooler and rad.

At higher frequencies the domes begin to beam their signal so this would produce undesireable effects. Cross them over early rather than late.

[Tom Loizeaux]

...At higher frequencies the domes begin to beam their signal so this would produce undesireable effects...

This is for a P A application and a wider horizontal spread is what I was looking for. The 2-15s spread pretty wide and the horn on top (2.5K and up) are called 90 degree horns, so I thought that folding these 10" (2123Hs) in slightly would help spread the mids (500 to 2.5K) to be a closer match to my other frequency spreads.
I guess the question is: would splaying them out, as opposed to in, be any better? ... not that I want to re-build these cabinets, but I want to know what my system is doing.

Thanks,

Tom

[Tom Loizeaux]

BTW, here's a photo of one of the P A stacks.

Tom

[grumpy]

Hi Tom,

You probably know all of this...
The beaming angle is frequency dependent so the overlap and interference patters will be also.
Splaying them inward will tend to prevent a "hole" that splaying them outward might cause
at the upper end of your spectra. Interferometric problems may be noticeable as you
move side to side... if not, no problem :) Nice stack.

-grumpy

[glen]

Hi Tom,

George Augspurger must've thought it was a good idea. He put hundreds of main monitors with that "folded-in baffle" design into professional recording studios over the last decade or two. They are usually a two-way system with a TAD components including a 4001 driver handling the highs.

[duaneage]

It's all about the crossover frequency

(What's the frequency, Kenneth?) ( A little REM / Dan Rather Humor )

If you move to the midrange ( or Horn) before the drivers get directive it does not matter. For 10 inch drivers you can probably go 2000Hz. 12s and 15s are going to be lower.

[Tom Loizeaux]

It's all about the crossover frequency...
If you move to the midrange ( or Horn) before the drivers get directive it does not matter. For 10 inch drivers you can probably go 2000Hz. 12s and 15s are going to be lower.

Thanks for the responses.
Here's an image of the Renkus-Heinz ST7 that uses a pair of 10 inch mids, towed in, but at a steeper angle then mine.

Tom

[ibobby]

Great info folks. I have searched hi and low on the internet for plans or detailed photos to build a set folded-baffle-design enclosures like the GA mains found in commerical studios. But I havent found any as of yet

Here is a link to build the horns.

http://members.aol.com/araiyuichi/Process/process01.htm
http://members.aol.com/araiyuichi/

If any one can help with a link to build the enclosures, it would be great.

Thanks

[glen]

Great info folks. I have searched hi and low on the internet for plans or detailed photos to build a set folded-baffle-design enclosures like the GA mains found in commerical studios. But I havent found any as of yet

Never saw any plans, but I've got the parts. A pair of the big Augspurger mains, but using a different horn (originally used in a screening room). As far as I can tell the box, baffle and ports are the same as the recording studio monitors.
I also have ONE of the Augspurger horns. For a 2 inch throat horn it is very short. And unlike the Smith or Yuichi horns the vanes in the throat are not tapered, but are made from thin flat plywood bent to follow the contours of the inner throat. I think that Beyma made a plastic horn of similar design.

When I have the time to dig those out of their place of entombment in the garage I'll post some drawings.

[glen]

. . . detailed photos . . .
of my one lonely Augspurger horn

[louped garouv]

pretty horn.....

not as "finished" as I would have thought it would be, but still very pretty...

industrial art.....

[ibobby]

:applaud: Great! Love the info and I will be waiting on those other pics if u can find them. Those horn pics looks super nice too. Thanks a million.


and louped garouv

"the city where imagination takes precedence over fact"

....I miss crawfish too....:D

[louped garouv]

I miss walking around everywhere all the time with a drink/NO original daquari in my hand ;)

[ibobby]

just got back from Jazz Fest 2007. :applaud: but it was hot:blink:


Glen...any luck on finding the Augs? thanks

[glen]

just got back from Jazz Fest 2007. :applaud: but it was hot:blink:


Glen...any luck on finding the Augs? thanks

Here are some measurements, didn't open them up for interior bracing. HI end horn on mine is Emilar, not the small wood horn or larger Northwest.
Seems like all panels are one inch thick particle board.
Drawing is NOT to scale.

[lfh]

Hi Glen,

thanks for posting this most interesting info!

I have a question related to the Augspurger horn: What does the inside of the throat plate look like, and what are the properties of the hole? E.g. does the hole constitute a smooth continuation of the built-in horn throat of the 244x drivers or is it a plain cylindrical bore? Are the edges towards the horn camfered?

The arrangement with four countersunk bolts and large studs is clever BTW.

Fredrik

[glen]

Hi Glen,

thanks for posting this most interesting info!

I have a question related to the Augspurger horn: What does the inside of the throat plate look like, and what are the properties of the hole? E.g. does the hole constitute a smooth continuation of the built-in horn throat of the 244x drivers or is it a plain cylindrical bore? Are the edges towards the horn camfered?

The arrangement with four countersunk bolts and large studs is clever BTW.

Fredrik

I am not really familiar with the throat geometry of the drivers, but here's a couple of things I think I know . . .

Every Augspurger monitor with the "folded in" arrangement I've heard of was equipped with TAD horn drivers usually 4001s, not JBL. My examples, previously used in a screening room, have 4002 drivers.

The example of the smaller wooden horn with the rounded over lips that I have came with the simpest throat you could imagine: a 1 inch thick piece of particle board with a 2 inch diameter hole on the driver side and a 2 inch square hole on the horn side. It's a very short transition with what would seem like a fairly rapid expansion that deep in the throat(?) Maybe throat geometry is not as critical since this relatively short horn is acting more like a wave guide?

[lfh]

Every Augspurger monitor with the "folded in" arrangement I've heard of was equipped with TAD horn drivers usually 4001s, not JBL. My examples, previously used in a screening room, have 4002 drivers.

Ah, of course -- I forgot. (I figure the TAD:s are very similar to the 244x in this respect.)



The example of the smaller wooden horn with the rounded over lips that I have came with the simpest throat you could imagine: a 1 inch thick piece of particle board with a 2 inch diameter hole on the driver side and a 2 inch square hole on the horn side. It's a very short transition with what would seem like a fairly rapid expansion that deep in the throat(?)

OK. I'll make some plates for my Q&D Modular Mains and this info is already very helpful. (Of course, I'd love to see a pic if you have the time and the horn is easily available.)

Fredrik

[Zilch]

http://www.reyaudio.com/warp-e.html

[Pretend that was easy to find.... :p ]

[ibobby]

Glen my friend. U made me smile like a pretty woman does :applaud:

but i promise not to ask for your phone number. :D

[glen]

http://www.reyaudio.com/warp-e.html

[Pretend that was easy to find.... :p ]
So they're crossing over the TAD4001s at 400 hz?
Sounds too low.
I also recall once hearing that the Kinoshita crossovers swallow up an enormous amount of power, but that might have been a generation or two earlier.

[glen]

Glen my friend. U made me smile like a pretty woman does :applaud:

but i promise not to ask for your phone number. :D
If speaker drawings make you smile like that then you've definitely found the right crowd to hang with here
:cheers:

[Zilch]

I think I understand the Rey directivity, but I can't say I much get the point yet. Something's getting lost in the translation.

Thought I had it figured out at one point, but E2 instructions kicked my ass. They want me to put the helper woofer on the wrong side. :blink:

Fold-in, fold-out, :blah:

I'll have to make some empirical determinations here.... :p

[merlin]

I also recall once hearing that the Kinoshita crossovers swallow up an enormous amount of power, but that might have been a generation or two earlier.

http://i6.photobucket.com/albums/y225/airwise/1024Dscn2317.jpg

The reason looks like it might remain a mystery.

[ibobby]

:applaud:
just wanted to say thanks again for starting this topic and for all the replies.

I've been reading so much info on this website is crazy. I wish I could upgrade my brain like I upgrade harddrives.:D I need more room for more info.

I'm off in search of info on components similars to TAD 4001s and 1603s.

[DJ Vincenzo]

design is in JBLs baddest speaker ($12 grand)....the vertec 4889....look at the 4 mids at 90 degree angles (the 4 slits)

Then again it could beam the wave to produce a longer throw which is what we dont want.


http://www.jblpro.com/vertec1/new_vertec/assets/vt4889_small.jpg

http://www.jblproservice.com/pdf/VerTec%20Series/VT4889.pdf