Well tb46 hasn't contacted me yet.
If anyone is on a thread of with please inform him. OR if anyone wants to draw that up (see above post) I will build one.
I should be finishing up
my test box for my new dual 12 TH tonight. Only thing left is the speaker baffles. It is BIG. 171.5 cm x 40" x 15". just at 400 Lt internally. As long as this one comes close to the HR data I will be happy.
Screamer -
you going to put up a PDF of your design?
If anyone is on a thread of with please inform him. OR if anyone wants to draw that up (see above post) I will build one.
I should be finishing up
my test box for my new dual 12 TH tonight. Only thing left is the speaker baffles. It is BIG. 171.5 cm x 40" x 15". just at 400 Lt internally. As long as this one comes close to the HR data I will be happy.
Screamer -
you going to put up a PDF of your design?
Hey FlipC
I have tried to send you an E-mail as well...
...But it didn't appear successful.
I'm antoneb@pacbell.net.
I have tried to send you an E-mail as well...
...But it didn't appear successful.
I'm antoneb@pacbell.net.
Sorry
The other day I realized I had set my Message Filter incorrectly for that email address. I had created a "Name Spoof" filter but instead of it checking to see if BOTH TO and FROM were the same I had it set to "IF ANY MATCH". Which means it was deleting EVERY email sent to me at that address since July 4th!
My apologies!
tb46-
I was going to say if you can draw your dual 12 up or make it Sketchup. I will build one! I like the outcome.
I am currently working on my own
Utilizing a Lab 12 Gen 2 driver. I want something that is less than 400 Lt. >$300 to build and goes down to 30 Hz. At above 135 DB. Preferably 140 plus at 38 Hz -150 Hz. Which is about where I stand right now. Though layout issues still abound.
The other day I realized I had set my Message Filter incorrectly for that email address. I had created a "Name Spoof" filter but instead of it checking to see if BOTH TO and FROM were the same I had it set to "IF ANY MATCH". Which means it was deleting EVERY email sent to me at that address since July 4th!
My apologies!
tb46-
I was going to say if you can draw your dual 12 up or make it Sketchup. I will build one! I like the outcome.
I am currently working on my own
Utilizing a Lab 12 Gen 2 driver. I want something that is less than 400 Lt. >$300 to build and goes down to 30 Hz. At above 135 DB. Preferably 140 plus at 38 Hz -150 Hz. Which is about where I stand right now. Though layout issues still abound.
Hey FlipC
My email got bounced back this time.
This is what it said...
Ohh Here is my original Email relating to a question I asked in the Tapped
horn Forum.
Hey man,
I've been wondering if my tapped horn layout I posted on the Pro Audio
Tapped horn Forum .
I'm not sure if you weren't comfortable answering in a public forum??
http://www.diyaudio.com/forums/showthread.php?postid=1810592#post1810592
Would love to know if I'm close to what you came up with for internal
layout.
I have been tempted to buy some MDF and build one up.
Thanks.
Anyhow,
I just read your post about trying a TH design using the LAB12 Gen 2.
From most of the modeling I've seen with the LAB12 it has lead me to believe
that the LAB12 is not the best candidate for a TH unless it is designed to
go to 16Hz or bellow. It seemed to have serious XMAX issues in a horn of
smaller size. Though I wouldn't rule it out. It would seem better suited
in a TH that is larger and goes lower than the DTS-20.
I could be wrong though I haven't messed modeling a LAB12 in the newer
versions of Hornresp. But I did mess with AKABAK before the TH-feature was
created.
Anyhow would like to know what you come up with.
I didn't look to close the HornRESP numbers for the Dual 12PS100 TH.
Is that supposed to be like a dual TH-Mini? Or is it something else?
I've been thinking about doing some TH-designs with Micro Drivers.
Haven't found quite the right driver yet, but Tang band looks
promising.
Cheers-
Antone-
My email got bounced back this time.
This is what it said...
Ohh Here is my original Email relating to a question I asked in the Tapped
horn Forum.
Hey man,
I've been wondering if my tapped horn layout I posted on the Pro Audio
Tapped horn Forum .
I'm not sure if you weren't comfortable answering in a public forum??
http://www.diyaudio.com/forums/showthread.php?postid=1810592#post1810592
Would love to know if I'm close to what you came up with for internal
layout.
I have been tempted to buy some MDF and build one up.
Thanks.
Anyhow,
I just read your post about trying a TH design using the LAB12 Gen 2.
From most of the modeling I've seen with the LAB12 it has lead me to believe
that the LAB12 is not the best candidate for a TH unless it is designed to
go to 16Hz or bellow. It seemed to have serious XMAX issues in a horn of
smaller size. Though I wouldn't rule it out. It would seem better suited
in a TH that is larger and goes lower than the DTS-20.
I could be wrong though I haven't messed modeling a LAB12 in the newer
versions of Hornresp. But I did mess with AKABAK before the TH-feature was
created.
Anyhow would like to know what you come up with.
I didn't look to close the HornRESP numbers for the Dual 12PS100 TH.
Is that supposed to be like a dual TH-Mini? Or is it something else?
I've been thinking about doing some TH-designs with Micro Drivers.
Haven't found quite the right driver yet, but Tang band looks
promising.
Cheers-
Antone-
sumsound I am unsure why it bounced.
the address exist. Did you receive the one I sent to you?
Samuel
I thought I posted the HR data for the dual 12 on here.
But not a layout pic. If you or anyone wants to give it a go just take the driver and see how much SPL you can get out of up to 400 Lt box. Down to 35 hz.
All I have done so far is a simple "M" shape.
See pic below. The length is correct but at the cost of an overall external size of 669 Lt. because I wanted to make the test box easy to build. The drivers simply sit on the left and right side with
the cone facing into the path. I built this box to be able to do another test of HR response chart and also the phenomena that the low end valleys get filled in a TH. Both my Mini Clones and Screamers Furybox has attested to this fact. Danley mentioned in on the original TH thread or such also. And yes - when i get a final design done I will post it.
As far as the Lab 12 goes.
It is a relatively cheap driver. I can get 2 for the a few more $ than the B&C or like drivers. Also since this isn't Hi-Fi I am not worried nor do I want a flat curve. I expect the dips to get filled. I just wanted massive SPL down. Doesnt have to be the Lab 12 IF you can find another driver to do the job of 140+ Db 38-150 Hz at 400 lt or less. keep the box under $300 US to boot! This can be done with the Lab 12. (4 dual 12 boxes)
Sumsound,
No your layout is different than mine. Mine has a longer path. I just went and got my drawings. I will start work on a Sketchup model of it as other have asked for it as well. I will let you know when i get that done but it shouldn't take me to long.
tb46's dual 12 is just a dual 12 in regards to my post about wanting MORE. I am a bass addict. His response chart is rather nice.
There are ALLOT of designs for micro drivers.
Look at the TH for cars thread and the original TH thread. I myself do plan to build a TH Spud some day soon. I just have to get the rest of the system first. (IE I do not have a Home Theater setup)
the address exist. Did you receive the one I sent to you?
Samuel
I thought I posted the HR data for the dual 12 on here.
But not a layout pic. If you or anyone wants to give it a go just take the driver and see how much SPL you can get out of up to 400 Lt box. Down to 35 hz.
All I have done so far is a simple "M" shape.
See pic below. The length is correct but at the cost of an overall external size of 669 Lt. because I wanted to make the test box easy to build. The drivers simply sit on the left and right side with
the cone facing into the path. I built this box to be able to do another test of HR response chart and also the phenomena that the low end valleys get filled in a TH. Both my Mini Clones and Screamers Furybox has attested to this fact. Danley mentioned in on the original TH thread or such also. And yes - when i get a final design done I will post it.
As far as the Lab 12 goes.
It is a relatively cheap driver. I can get 2 for the a few more $ than the B&C or like drivers. Also since this isn't Hi-Fi I am not worried nor do I want a flat curve. I expect the dips to get filled. I just wanted massive SPL down. Doesnt have to be the Lab 12 IF you can find another driver to do the job of 140+ Db 38-150 Hz at 400 lt or less. keep the box under $300 US to boot! This can be done with the Lab 12. (4 dual 12 boxes)
Sumsound,
No your layout is different than mine. Mine has a longer path. I just went and got my drawings. I will start work on a Sketchup model of it as other have asked for it as well. I will let you know when i get that done but it shouldn't take me to long.
tb46's dual 12 is just a dual 12 in regards to my post about wanting MORE. I am a bass addict. His response chart is rather nice.
There are ALLOT of designs for micro drivers.
Look at the TH for cars thread and the original TH thread. I myself do plan to build a TH Spud some day soon. I just have to get the rest of the system first. (IE I do not have a Home Theater setup)
An externally hosted image should be here but it was not working when we last tested it.
Hey Flip,
Yes I got your email, the first time I sent to you it didn't get bounced back, this time it did.
Yes I agree that the LAB12 is quite a bargain. I just found it was a little difficult to make a TH that was happy with it (at least for something like the DTS-20) It was not staying withing XMAX in its intended range power bandwidth, which is something that I normally obsess about.
I am interested in seeing what you did with the B&C TH, I used the original foot print to come up with my dimensions but I'm not sure if I can count the horn mouth area as part of the path length anymore. I ended up using increased inductance to flatten response in hornResp.
The one rule of thumb that I have found when choosing TH drivers, is you actually want A higher FS than the low cut of the horn maybe even as much as .5-1 octave higher.
140dB with 2 12s?? Has Danley done that yet?? Don't forget to set HornResp to 2pi.
Sounds good.
Antone-
Yes I got your email, the first time I sent to you it didn't get bounced back, this time it did.
Yes I agree that the LAB12 is quite a bargain. I just found it was a little difficult to make a TH that was happy with it (at least for something like the DTS-20) It was not staying withing XMAX in its intended range power bandwidth, which is something that I normally obsess about.
I am interested in seeing what you did with the B&C TH, I used the original foot print to come up with my dimensions but I'm not sure if I can count the horn mouth area as part of the path length anymore. I ended up using increased inductance to flatten response in hornResp.
The one rule of thumb that I have found when choosing TH drivers, is you actually want A higher FS than the low cut of the horn maybe even as much as .5-1 octave higher.
140dB with 2 12s?? Has Danley done that yet?? Don't forget to set HornResp to 2pi.
Sounds good.
Antone-
BTW
Here is my original attempt at modeling what the TH-mini is.
http://www.diyaudio.com/forums/showthread.php?postid=1781640#post1781640
Still don't know how close the internals are, I started with a best guess trying to start with a 3:1 compression ratio expanding to a little less than 1:2 at the mouth the expansion on the model is fairly linear conical.
Antone-
Here is my original attempt at modeling what the TH-mini is.
http://www.diyaudio.com/forums/showthread.php?postid=1781640#post1781640
Still don't know how close the internals are, I started with a best guess trying to start with a 3:1 compression ratio expanding to a little less than 1:2 at the mouth the expansion on the model is fairly linear conical.
Antone-
tb46 -
looking forward to it.
Here are 2 pics of the crazy big test box I did this week.
Apologies for the blurriness, set to auto but didn't change the focus to auto and didn't even look until I got them onto the computer already.
It will become scrap tomorrow.
Funny that I had to put a Cerwin B36 on top of it lying down to keep the thing in order. No braces! Again this was just testing the path length. The internal path volume was cut down by creating a channel but the 2nd portion wasn't. Definitely wasn't straining to reproduce low notes though the natural cutoff was steep.
Sumsound - I am not trying to go
for anything like the DTS-20 or the SPUD. Those are meant for home use. I want purely for abusive SPL level. And Yes Danley has achieved what I am trying to do. His 212 in a single cabinet does 138 DB max. So in a quad setup it will be 145 ish. I get spikes with the Lab 12 but I think those will be filled in. Plus the LAB 12 can take some punishment! (can anyone figure out the 212 layout?)
In regards to the mini's
When I first started I tried to get a flat response.
Then after reading more of Danleys white papers and patent apps I came to the understanding that you want to work with 2 spikes on your low end. That the dip in between will get filled up on the actual output. I built my Mini's (realized other day pics are no longer up- not sure what happened to em when I migrated web servers but will re post asap) and then Screamer built his. This phenomenon was shown true. Which is why he cant get a HR response like his TRUE response. HR is good but not perfect it seems. And unfortunately I am not good enough with Akabak myself to use it. (been trying with the dual 12 project but end up with headaches)
As I mentioned my layout was different.
I started a Sketchup model. Not exactly 100% but you will get a good idea from it.
I to started with back engineering. I knew the outer dimensions and also the driver used. Figured the path distance and started playing.
Note that Danley also said you do not need reflectors.
Nor does the path have to be angular. Just make sure the expansion increases at each change.
Now the ones I actually built I changed
somewhat. I had originally built a test box for a 15" I had. I had it so I could change the amount of compression on the driver. I found I liked the driver firing 100% into the throat. Unlike the pic above that show's a constrictive throat/baffle. On the build I also angled my interior path walls. I basically followed the angle of the first piece. To the 2nd piece. To the third piece etc. Only the last, which is the top portion of the mouth did I have to cut and angle on. When I laid it out on the board it worked so I did it. Simple as that.
Yours seems fine.
Just get rid of the inductor. I cant see you using such a sub for HT duty?
I am going to build 2 more but use the
real plans instead of my improvising. Try to get them to work and look better.
If you draw yours up I will build one to test it.
Yes I am a junkie.
So in my basement sits:
2 self powered, Dual 12 Horns with separate 2" compression horns.
2 Cerwin B36 (very FIRST ones - not the B36a)
2 Mini Clones
4 15" 2 ways
2 12" 2 Ways
2 Dual 10 2 ways
2 8 inch 3 ways
2 15" 3 ways
2 Yorkville/RCF horns
And in the garage sits a "House Wrecka" (dual 15" sub) Drivers in the basement boxed up. Been working on a SPUD type box for these with the drivers sitting horizontal to the floor firing down.
Amps -
Yamahaa (for monitors)
Crown XLS 602 x2
Crest FA2401 x2
Behringer EP4K (just got that)
Plus processing gear.
I can not help it.
looking forward to it.
Here are 2 pics of the crazy big test box I did this week.
Apologies for the blurriness, set to auto but didn't change the focus to auto and didn't even look until I got them onto the computer already.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
It will become scrap tomorrow.
Funny that I had to put a Cerwin B36 on top of it lying down to keep the thing in order. No braces! Again this was just testing the path length. The internal path volume was cut down by creating a channel but the 2nd portion wasn't. Definitely wasn't straining to reproduce low notes though the natural cutoff was steep.
Sumsound - I am not trying to go
for anything like the DTS-20 or the SPUD. Those are meant for home use. I want purely for abusive SPL level. And Yes Danley has achieved what I am trying to do. His 212 in a single cabinet does 138 DB max. So in a quad setup it will be 145 ish. I get spikes with the Lab 12 but I think those will be filled in. Plus the LAB 12 can take some punishment! (can anyone figure out the 212 layout?)
In regards to the mini's
When I first started I tried to get a flat response.
Then after reading more of Danleys white papers and patent apps I came to the understanding that you want to work with 2 spikes on your low end. That the dip in between will get filled up on the actual output. I built my Mini's (realized other day pics are no longer up- not sure what happened to em when I migrated web servers but will re post asap) and then Screamer built his. This phenomenon was shown true. Which is why he cant get a HR response like his TRUE response. HR is good but not perfect it seems. And unfortunately I am not good enough with Akabak myself to use it. (been trying with the dual 12 project but end up with headaches)
As I mentioned my layout was different.
I started a Sketchup model. Not exactly 100% but you will get a good idea from it.
An externally hosted image should be here but it was not working when we last tested it.
I to started with back engineering. I knew the outer dimensions and also the driver used. Figured the path distance and started playing.
Note that Danley also said you do not need reflectors.
Nor does the path have to be angular. Just make sure the expansion increases at each change.
Now the ones I actually built I changed
somewhat. I had originally built a test box for a 15" I had. I had it so I could change the amount of compression on the driver. I found I liked the driver firing 100% into the throat. Unlike the pic above that show's a constrictive throat/baffle. On the build I also angled my interior path walls. I basically followed the angle of the first piece. To the 2nd piece. To the third piece etc. Only the last, which is the top portion of the mouth did I have to cut and angle on. When I laid it out on the board it worked so I did it. Simple as that.
Yours seems fine.
Just get rid of the inductor. I cant see you using such a sub for HT duty?
I am going to build 2 more but use the
real plans instead of my improvising. Try to get them to work and look better.
If you draw yours up I will build one to test it.
Yes I am a junkie.
So in my basement sits:
2 self powered, Dual 12 Horns with separate 2" compression horns.
2 Cerwin B36 (very FIRST ones - not the B36a)
2 Mini Clones
4 15" 2 ways
2 12" 2 Ways
2 Dual 10 2 ways
2 8 inch 3 ways
2 15" 3 ways
2 Yorkville/RCF horns
And in the garage sits a "House Wrecka" (dual 15" sub) Drivers in the basement boxed up. Been working on a SPUD type box for these with the drivers sitting horizontal to the floor firing down.
Amps -
Yamahaa (for monitors)
Crown XLS 602 x2
Crest FA2401 x2
Behringer EP4K (just got that)
Plus processing gear.
I can not help it.
tb46 -
looking forward to it.
Here are 2 pics of the crazy big test box I did this week.
Apologies for the blurriness, set to auto but didn't change the focus to auto and didn't even look until I got them onto the computer already.
It will become scrap tomorrow.
Funny that I had to put a Cerwin B36 on top of it lying down to keep the thing in order. No braces! Again this was just testing the path length. The internal path volume was cut down by creating a channel but the 2nd portion wasn't. Definitely wasn't straining to reproduce low notes though the natural cutoff was steep.
Sumsound - I am not trying to go
for anything like the DTS-20 or the SPUD. Those are meant for home use. I want purely for abusive SPL level. And Yes Danley has achieved what I am trying to do. His 212 in a single cabinet does 138 DB max. So in a quad setup it will be 145 ish. I get spikes with the Lab 12 but I think those will be filled in. Plus the LAB 12 can take some punishment! (can anyone figure out the 212 layout?)
In regards to the mini's
When I first started I tried to get a flat response.
Then after reading more of Danleys white papers and patent apps I came to the understanding that you want to work with 2 spikes on your low end. That the dip in between will get filled up on the actual output. I built my Mini's (realized other day pics are no longer up- not sure what happened to em when I migrated web servers but will re post asap) and then Screamer built his. This phenomenon was shown true. Which is why he cant get a HR response like his TRUE response. HR is good but not perfect it seems. And unfortunately I am not good enough with Akabak myself to use it. (been trying with the dual 12 project but end up with headaches)
As I mentioned my layout was different.
I started a Sketchup model. Not exactly 100% but you will get a good idea from it.
I to started with back engineering. I knew the outer dimensions and also the driver used. Figured the path distance and started playing.
Note that Danley also said you do not need reflectors.
Nor does the path have to be angular. Just make sure the expansion increases at each change.
Now the ones I actually built I changed
somewhat. I had originally built a test box for a 15" I had. I had it so I could change the amount of compression on the driver. I found I liked the driver firing 100% into the throat. Unlike the pic above that show's a constrictive throat/baffle. On the build I also angled my interior path walls. I basically followed the angle of the first piece. To the 2nd piece. To the third piece etc. Only the last, which is the top portion of the mouth did I have to cut and angle on. When I laid it out on the board it worked so I did it. Simple as that.
Yours seems fine.
Just get rid of the inductor. I cant see you using such a sub for HT duty?
I am going to build 2 more but use the
real plans instead of my improvising. Try to get them to work and look better.
If you draw yours up I will build one to test it.
Yes I am a junkie.
So in my basement sits:
2 self powered, Dual 12 Horns with separate 2" compression horns.
2 Cerwin B36 (very FIRST ones - not the B36a)
2 Mini Clones
4 15" 2 ways
2 12" 2 Ways
2 Dual 10 2 ways
2 8 inch 3 ways
2 15" 3 ways
2 Yorkville/RCF horns
And in the garage sits a "House Wrecka" (dual 15" sub) Drivers in the basement boxed up. Been working on a SPUD type box for these with the drivers sitting horizontal to the floor firing down.
Amps -
Yamahaa (for monitors)
Crown XLS 602 x2
Crest FA2401 x2
Behringer EP4K (just got that)
Plus processing gear.
I can not help it.
looking forward to it.
Here are 2 pics of the crazy big test box I did this week.
Apologies for the blurriness, set to auto but didn't change the focus to auto and didn't even look until I got them onto the computer already.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
It will become scrap tomorrow.
Funny that I had to put a Cerwin B36 on top of it lying down to keep the thing in order. No braces! Again this was just testing the path length. The internal path volume was cut down by creating a channel but the 2nd portion wasn't. Definitely wasn't straining to reproduce low notes though the natural cutoff was steep.
Sumsound - I am not trying to go
for anything like the DTS-20 or the SPUD. Those are meant for home use. I want purely for abusive SPL level. And Yes Danley has achieved what I am trying to do. His 212 in a single cabinet does 138 DB max. So in a quad setup it will be 145 ish. I get spikes with the Lab 12 but I think those will be filled in. Plus the LAB 12 can take some punishment! (can anyone figure out the 212 layout?)
In regards to the mini's
When I first started I tried to get a flat response.
Then after reading more of Danleys white papers and patent apps I came to the understanding that you want to work with 2 spikes on your low end. That the dip in between will get filled up on the actual output. I built my Mini's (realized other day pics are no longer up- not sure what happened to em when I migrated web servers but will re post asap) and then Screamer built his. This phenomenon was shown true. Which is why he cant get a HR response like his TRUE response. HR is good but not perfect it seems. And unfortunately I am not good enough with Akabak myself to use it. (been trying with the dual 12 project but end up with headaches)
As I mentioned my layout was different.
I started a Sketchup model. Not exactly 100% but you will get a good idea from it.
An externally hosted image should be here but it was not working when we last tested it.
I to started with back engineering. I knew the outer dimensions and also the driver used. Figured the path distance and started playing.
Note that Danley also said you do not need reflectors.
Nor does the path have to be angular. Just make sure the expansion increases at each change.
Now the ones I actually built I changed
somewhat. I had originally built a test box for a 15" I had. I had it so I could change the amount of compression on the driver. I found I liked the driver firing 100% into the throat. Unlike the pic above that show's a constrictive throat/baffle. On the build I also angled my interior path walls. I basically followed the angle of the first piece. To the 2nd piece. To the third piece etc. Only the last, which is the top portion of the mouth did I have to cut and angle on. When I laid it out on the board it worked so I did it. Simple as that.
Yours seems fine.
Just get rid of the inductor. I cant see you using such a sub for HT duty?
I am going to build 2 more but use the
real plans instead of my improvising. Try to get them to work and look better.
If you draw yours up I will build one to test it.
Yes I am a junkie.
So in my basement sits:
2 self powered, Dual 12 Horns with separate 2" compression horns.
2 Cerwin B36 (very FIRST ones - not the B36a)
2 Mini Clones
4 15" 2 ways
2 12" 2 Ways
2 Dual 10 2 ways
2 8 inch 3 ways
2 15" 3 ways
2 Yorkville/RCF horns
And in the garage sits a "House Wrecka" (dual 15" sub) Drivers in the basement boxed up. Been working on a SPUD type box for these with the drivers sitting horizontal to the floor firing down.
Amps -
Yamahaa (for monitors)
Crown XLS 602 x2
Crest FA2401 x2
Behringer EP4K (just got that)
Plus processing gear.
I can not help it.
sumsound said:
Danley posted at some point (might have been here or at avsforums - I can't find it now) that his SPL ratings are not necessarily within driver xmax (or xmech), but are extrapolated from the driver power handling.
FlipC said:
How large a dip do you think will get filled in?
Cheers
fb -
just about 3 DB or there about.
I have been trying to remember just
where I read Danley talking about it. I cant recall if it's within the original TH thread or in the DTS-20 thread. But both my Mini Clone and ScreamerUSA's Furybox both fill this troph on the actual output.
In my current Dual Lab12 idea.
I have a 6 Db dip. I wont go over that. IF only part of that gets filled I will use EQ on that channel to compensate.
Funny those pics make that test box look small.
FYI that is 171.5 cm front to back external. Watching the watchmen with it at my back was fun. Now it is gone to the scrap yard.
just about 3 DB or there about.
I have been trying to remember just
where I read Danley talking about it. I cant recall if it's within the original TH thread or in the DTS-20 thread. But both my Mini Clone and ScreamerUSA's Furybox both fill this troph on the actual output.
In my current Dual Lab12 idea.
I have a 6 Db dip. I wont go over that. IF only part of that gets filled I will use EQ on that channel to compensate.
Funny those pics make that test box look small.
FYI that is 171.5 cm front to back external. Watching the watchmen with it at my back was fun. Now it is gone to the scrap yard.