Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[raj]

Thanks Peter ,
A very good idea to do small jobs with only two subs ,
If the venue permits will it be better if two subs are placed horizontally in

the centre with their mouths next to each other and fly the Tops on stands

in both sides .

Rajeev

[Chris Parsons]

My tops are JBL 4732s.  One per side.  I figured that 1 LAB per 4732 would be fine, and actually overkill if anything...  It that accruate?

-Chris Parsons

[Steve Shafer]

I saw this horn and phase plug kit and thought it would be a good starting point for a top box.

http://www.proaudioparts.co.uk/index.php?id=pornhorn

This is a bit different approach then what has been suggested on the forum. What would be the upside and the downside of going with a mid driver assembly like the one above

my .02

Steve S

[Too Tall (Curtis H. List)]

Stevesb65 wrote on Mon, 18 October 2004 00:43

I saw this horn and phase plug kit and thought it would be a good starting point for a top box. http://www.proaudioparts.co.uk/index.php?id=pornhorn "Porn Horn"??? Pleeeeeeeeze!  LOL This is a bit different approach then what has been suggested on the forum. What would be the upside and the downside of going with a mid driver assembly like the one above my .02 Steve S

Hi Steve,

   Well lets take it case by case.

   IMHO a single 12" front-loaded is a nice box for the install market and small bars, but not the BEST match for the LAB subs. The 12" is hopelessly outmatched by the sub and the 2". It's not a bad box, just not a good match. It's only advantage is weight, which can be the most important consideration if you are by yourself setting up a PA.

Using a true horn loaded mid-bass means the horn is going to be BIG if it's going to reach down to 80Hz and mate with the LAB. If you can stand that it will be a good match, but I would not present it as the solution with the broadest appeal. It works best as part of a 4-way design.

Were I to design a top box for the LAB sub with the tools I have available I would go with a two 12" woofers and a 2" horn. Either MTM if the top box is just a 2-way or TMM if the top box can be filtered to make it a 2 1/2-way. The bottom 12" would only sees low mid frequencies. It is only there to help with the 80Hz to 250Hz range.

I might play with a wave guide on the 12" and some partial loading. IOW part of the 12" drivers are covered by the horn throat giving it a mild compression ratio and changing the dispersion.


This was done on a box a friend designed and I built 20 years ago and it still stands up as a solid box. With the tools available today we would actually be able to model and check the design to some degree instead of blindly trying different box designs.


My next fall back design would be a single 15" and 1" horn. This would have more reach in the low-mids, while not breaking the bank. The design fails or stands on the 1" driver and horn.

The horn needs to be bigger rather then smaller and the 1" driver needs to be "robust". Add some steep and well placed filtering and you have a powerful box. This is what Al uses for monitors and even though they use passive xovers and no time alignment they perform quite well as monitors and on a stick as mains with the LAB subs.


   Their drawback is they are fairly large even for a 15" box. The larger horn is responsible for this, but you CAN'T cheat the horn size and have it work well with a 15".

Too Tall

[Mark Seaton]

First, I got a good laugh at the name of those horns; especially the logo.  I am pretty confident the "well endowed" nature of the phase plug spawned the name.  

I have posted about this before, but the major problem I see here is that all of the people asking about a top box have no target in mind.  It is impossible to suggest what box might match well with your LABs when we don't know how you are using them, and we don't know what you need your main speakers to do.

I've posted this before, but once again, the concept of a 1:1 match of main to LAB sub is a flawed concept from the get go.  You should be adding more main speakers for coverage, not total output.  More boxes should be employed to deliver sound to a larger angle/audience.  The output within their coverage pattern won't/shouldn't change a lot.

If you want to define such a speaker system, first get an idea of what you want or need, and then keep in mind what is a want vs. a need.  I would first look at sensitivity at a nominal 1W.  In other words, this roughly defines what the ratio of power requirements will be relative to the LABs.  You then need to use some real numbers to determine what sort of SPL you want/need.  Now look at a range of minimum and maximum coverage angles you need.  Solutions start coming to the surface very quickly if you simply define the problem/objective accurately.

[Steve Shafer]

My concept of a top box for the Lab Sub was a three way box.  I would have used a 15" driver horn loaded with a DDS flare then the 10" with the "porn horn"  and then a BMS 1" compresion driver(a driver that I really like).  


The reason why i liked the porn horn is that it would allow me as a DIY person to have a horn loaded 10" cone driver with what looks to be a good phase plug arangment.

I had imagined to let the Lab Sub only handle up to 80 or 90 hz and then let the 15" take over.

Just tossing a few ideas about and learning along the way

Steve S

[Jeff Robinson]

Stevesb65 wrote on Mon, 18 October 2004 19:12

My concept of a top box for the Lab Sub was a three way box.  I would have used a 15" driver horn loaded with a DDS flare then the 10" with the "porn horn"  and then a BMS 1" compresion driver(a driver that I really like).   The reason why i liked the porn horn is that it would allow me as a DIY person to have a horn loaded 10" cone driver with what looks to be a good phase plug arangment. I had imagined to let the Lab Sub only handle up to 80 or 90 hz and then let the 15" take over. Just tossing a few ideas about and learning along the way Steve S

Hi Steve
Feel free to ignore me, I wish you the best of luck but there are a few problems I think you'll encounter.
On the 15"; for horn loading to work to 80 Hz the 1/4 wavelength minimum length of the horn is 3.5', while there are tricks to cheat a little any short horn starts to lose efficiency below that length. Look at DDS's DMB10pro with a length of 34.5" and has a gain spec'd at 12dB from 250 to 1.5k, which I do not doubt. The 15" horn choices have lengths of 15" or 5.75", they rate the short one at 3.5dB of gain with a response from 60 to 1.25K, I doubt that the horn adds any directivity below 500Hz. The 15" long horn is rated for 4.1dB of gain but I doubt it adds any control below 200Hz. By way of comparison the LABsub gives up to 18dB of gain (concentrated in less than 2 octaves of bandwidth).
On the 10"; the pornhorn is designed for a 12", while you can certainly make a mounting adapter you are giving up some compression ratio (and efficiency) by using a smaller cone. You'll notice it's length is 20" which is 1/4 wavelength of 170Hz and they say it'll do 130Hz (almost 1/2 octave lower).
Both Too Tall and Mark have given good info to consider in making your choices. In the past Mark has pointed out that not all applications need a top box to keep up to the LAB's maximum output capacity. If you don't really need that, lots of options open up, if you do then your options narrow to large efficient cabinets or pile up more small, lower efficiency cabinets.

Jeff Robinson

[Peter Sylvester]

Chris,

I have not used the JBL 4732 boxes, but it looks like they use 2x12 plus a mid and small horn, so they are probably comparable to 2 of my 12+2 cabs. In that case, I think you should be able to get by with just a pair of the LABs for a pair of 4732s just fine.

--Peter

[Steve Shafer]

Oops looks like I missed the driver size on that one.  At any rate, what about a 15" to the coaxial driver by BMS.  It will allow for a significanly lower x-over point that most 2" exit drivers.

Steve S

[David Trotter]

Have just finished building 4 LAB's (phew, thats 2 months of my life i want to forget quickly!)

Been following this thread, and some of you might be interested in the top combination i am using.

I have 4 HD15 speaker for 80-180hz. They are unbelievably loud and efficient. They area horn assisted bandpass speaker i belive. The horn is only about a meter long. but they are VERY loud and punchy and go well with the labs. They are also the same width (+9mm) as the labs, so go well.

I am currently using a double 12", 1.5" and super tweeters. Am considering packing the mids in for a single 12" on a porn horn.

Recon a single 12" will be able to keep up with everything else? Those horns look pretty big and efficient.

-dave