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ndcraig 3rd September 2013 04:31 PM

Need help with a midbass horn
 
I am trying to get the most 90 to 300Hz out of a single easy-to-build cabinet. Size isn't an issue and I'm trying to figure out the Hornresp software but not having much luck. I figure a straight horn would be the easiest, but not opposed to folding if it doesn't mess with the upper range response too much.

The system is for a donated PA type installation so I don't have much money to spend but do have plenty of materials and a large collection of drivers. (and not opposed to buying a single more optimum driver if necessary)

I'm assuming a horn is really the only way to accomplish this as a pile of reflex boxes wouldn't have the efficiency. I've only done bass-reflex type boxes and this would be my first horn and I figure a really good way to learn the process better.

Any help would be appreciated.

quinnling 3rd September 2013 05:30 PM

Goto
inlowsound.com

Look at the 80hz horn.. The owner of the site goes by Carpenter at this forum

weltersys 3rd September 2013 05:31 PM

Quote:

Originally Posted by ndcraig (Post 3618678)
I'm assuming a horn is really the only way to accomplish this as a pile of reflex boxes wouldn't have the efficiency. I've only done bass-reflex type boxes and this would be my first horn and I figure a really good way to learn the process better.

Horns are one way to accomplish a goal. Your goal is not clearly defined in terms of output required, coverage area, or drivers that you would like to use, cabinet size or budget.
Adding a second front loaded cone gives a 3 dB increase in efficiency, 6 dB more output when driven equally. Going to four cones gives a 6 dB increase in efficiency, 12 dB more output when driven equally.

Horns give from around 3 dB to 10 dB increase in efficiency and or sensitivity, depending on size and dispersion.

Unless you are planning to copy a mid-bass design (few in the subwoofer forum), time to start learning how to use Hornresp.

ndcraig 3rd September 2013 10:16 PM

Quote:

Originally Posted by weltersys (Post 3618738)
Horns are one way to accomplish a goal. Your goal is not clearly defined in terms of output required, coverage area, or drivers that you would like to use, cabinet size or budget.

Don't laugh, but I'm trying to add a couple octaves of lower response to a cluster of cobraflex paging horns on the roof of a press box across a football field from the home-side bleachers. I can achieve the sound I'm looking for with 4 Ramsa 12" boxes that I have (with blown tweeters and the 12's wired directly to the terminals bypassing the internal crossovers.). I'm using an old BSS Minidrive 2x4 dsp as an EQ crossover and limiter.
Would just like to have a single large box that would be more weatherproof than the Ramsa boxes -a horn would keep the driver back out of the elements more. (besides, I like the Ramsa's and want to use them for my portable sound outfit after repairing them properly)

I currently have a large stack of EV 12's (DL, EVM and similar) JBL E-140's as well as a pile of stamped and cast-frame eminence 18's 15's and 12's

Quote:

Adding a second front loaded cone gives a 3 dB increase in efficiency, 6 dB more output when driven equally. Going to four cones gives a 6 dB increase in efficiency, 12 dB more output when driven equally.

Horns give from around 3 dB to 10 dB increase in efficiency and or sensitivity, depending on size and dispersion.
If you think that a direct-radiating design would do it then I definitely know they are quicker and easier to build. However I thought this would be a good way to start learning horns better.

Quote:

Unless you are planning to copy a mid-bass design (few in the subwoofer forum), time to start learning how to use Hornresp.
Trust me, I'm trying -its just very difficult when it feels I'm flying blind. I can grasp bass reflex concepts but horns are eluding me. (or maybe it's just me not grasping what I feel is very non-intuitive software) That and when I get thinking I have the program working, I'm still at a loss on interpreting the results into something with dimensions I can actually build.
I also didn't think I would find any designs for this in a "subwoofer" forum as it seems they are all obsessing about 3-octaves lower than I need -but I'll look. (I am trying to go beyond just "copying" too)

Thanks for all your suggestions.

weltersys 4th September 2013 01:28 AM

Quote:

Originally Posted by ndcraig (Post 3619069)
Don't laugh, but I'm trying to add a couple octaves of lower response to a cluster of cobraflex paging horns on the roof of a press box across a football field from the home-side bleachers.

I currently have a large stack of EV 12's (DL, EVM and similar) JBL E-140's as well as a pile of stamped and cast-frame eminence 18's 15's and 12's

Cobra Flex for top end means a crossover around 400 Hz is OK. There are dozens of folded horn designs that would work fine.
The EV 12s would work well in "W" horn designs like the EV Sentry III and IV, simple folded horns that would be quite weatherproof.
Actually, all the speakers mentioned probably would probably be fine, but the JBL E-140's bring quite decent $$ from nostalgia types.
You can simply make the FH cabinet taller (the middle of the "W" should be vertical) to enclose more 12s. Good idea to make the compression chambers individual so one failed driver does not lead to more.

A ratio of one 12" in a FLH like a Sentry to one Cobraflex is about right.

Use grill cloth to keep the bugs and birds from nesting :p.

Art

ndcraig 4th September 2013 08:45 PM

Quote:

Originally Posted by weltersys (Post 3619231)
Cobra Flex for top end means a crossover around 400 Hz is OK. There are dozens of folded horn designs that would work fine.

I'm using the bigger fiberglass ones and not the smaller metal ones, I seem to be getting a good strong 300 out of them. (They've actually been running fullrange most of their life on an old 100W or so University amp) Not sure of the driver, but it does have a reasonably large phenolic diaphragm.

Quote:

The EV 12s would work well in "W" horn designs like the EV Sentry III and IV, simple folded horns that would be quite weatherproof.
I've dug around a bit and can't seem to find any dimensions or plans. Did find a TL-4025 as well as several Keele W-bins if I chose to go with a 15.
From what I see, those Sentry's are relatively shallow cabs, I could build a straight horn with that mouth size if I had dimensions to work with. The space I have is the entire roof of the press box (30x15') so a big wide flat horn isn't out of the question and it would make a great mounting platform for all the paging horns (4 of them)

Quote:

Actually, all the speakers mentioned probably would probably be fine, but the JBL E-140's bring quite decent $$ from nostalgia types.
I'm not going to put those outside for a small town football team with only 6 home-games. They definitely do seem to be popular with the vintage guitar/bass amp crowd, I have 6 of them in old wedge cabinets with emilar HF that haven't been used in years, was trying to figure out a more worthy project for them because they are in quite pristine condition.

Hesitant about the using the EV 12's too but I do have some rather large Eminence 12's as well as the Audiopile.net ones.

Quote:

You can simply make the FH cabinet taller (the middle of the "W" should be vertical) to enclose more 12s. Good idea to make the compression chambers individual so one failed driver does not lead to more.
A ratio of one 12" in a FLH like a Sentry to one Cobraflex is about right.[/quote]

I'm almost feeling like 2 to 1 would be all they need. They just want a bit better sounding rig for music playback -it's very close to useable as it is but the kids are excited about having football back in this small town for the first time in 25 years so just trying to make things a bit better. (Of course nobody has any budget for this :-)

Quote:

Use grill cloth to keep the bugs and birds from nesting :p.
seriously there were so many birds nests in the old field lights that one caught on fire! I plan on using a good downangle for drainage and fine stainless steal mesh.

Thanks Art. I will try to post pics of the project as it proceeds.

weltersys 4th September 2013 09:20 PM

Quote:

Originally Posted by ndcraig (Post 3620150)
I'm using the bigger fiberglass ones and not the smaller metal ones, I seem to be getting a good strong 300 out of them. (They've actually been running fullrange most of their life on an old 100W or so University amp) Not sure of the driver, but it does have a reasonably large phenolic diaphragm.

I've dug around a bit and can't seem to find any dimensions or plans. Did find a TL-4025 as well as several Keele W-bins if I chose to go with a 15.
From what I see, those Sentry's are relatively shallow cabs, I could build a straight horn with that mouth size if I had dimensions to work with. The space I have is the entire roof of the press box (30x15') so a big wide flat horn isn't out of the question and it would make a great mounting platform for all the paging horns (4 of them)

You can scale the TL-4025 or Keele W-bins down since 12" will be adequate for your needs and you are not looking for super low extension. Shrink the compression chamber a bit more than the 12/15 ratio.
The old EV Eliminator or Klipsch La Scala or old Peavey SP1 folded horns all would work OK too.
You can "unfold" those plans for a straight horn if you would like, but the FH use less wood, and tend to be well braced to start with

The HF will "clean up" a bit if you cross them at 400 Hz.
A 12" in a FLH of the type we are discussing will just about keep up with the Cobraflex, but if you want to go two 12" to one HF, that is fine.
Double the cones and they will only need half the power.

The Cobraflex would be best arranged in a vertical line, if you need more horizontal dispersion, arrange them like a "barber pole". If the vertical dispersion becomes more narrow than you care for, then arc the vertical in a "C" or "J".

bitSmasher 6th September 2013 07:19 AM

I wondered what a Cobraflex was, and found this... appropriate:

http://www.hifilit.com/hifilit/University/plans-1.jpg

djk 6th September 2013 09:18 AM

Cobreflex on top of a Klipsch LaScala bottom.

Easy build, 1 sheet.

ndcraig 15th September 2013 03:11 AM

Quote:

Originally Posted by djk (Post 3621878)
Cobreflex on top of a Klipsch LaScala bottom.

Easy build, 1 sheet.

been google-ing quite a bit and haven't found any build plans with dimensions for a "La Scala"
Found plenty of info on the huge MWM Klipsh bin. (remember using those years ago in a PA rig and had no clue who made them as they had been painted over so many times.)


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