Help! With a rear horn loaded scoop bass bin

I have decided to build 2x REAR HORN LOADED SCOOP BASS-Bins for a friend’s PA system. He is a local DJ and he wants to upgrade his system so that it has more bass. I would like some help with this project, as the instructions on the web site aren’t that clear, and they have no diagrams other then the plans them self. Anyways I have a few questions. On the page is says nothing about what driver to use, so I assume it is compatible with any 15” woofer (correct me if I am wrong!). Assuming that the enclosure is compatible with any 15” driver, how can I calculate how low and high it will go, that depends on the driver right? My last question is if anyone knows of a web site with clearer instructions on how to build the thing? If you know how to build it from personal experience that would be even better. Well, the answers to these questions will lead into some more having to do with amps and x-o.

Here’s an exact link to the page with the “instructions” and plans.
PA Systems, sound systems, speaker boxes, live Sound - Dancetech

Well thanks,
Slice:)
 
i relise that the LAB Horn goes lower but...

Well ThingyNess,
I ruled out the lab horn for a number of reasons.
1. Cost
2. Rumors of heat problem and killing drivers
3. Complexity

And just to let you know I have looked through many charts on the lab horn and it’s usable frequency SPL levels vary from ~97Db at ~22Hz to a peak of ~112Db at 85Hz. The problem is that my friends requirements are that the bass got to 300Hz witch the lab horn is incapable of doing. But this little bass-bin will reproduce 40-50Hz to 5000Hz easily at SPL levels from 97Db up to 104Db! I realize that the lab horn goes lower (20Hz) but its bandwidth is limited in the fact that it can only got up to about 200Hz. This narrow bandwidth is a limiting factor in the way this “speaker” can be used. On the other hand the bass box witch I am seeking help on can easily excide the lab horns potential as a bass/low-mid “speaker.

I'll take a loot at the 186 horn, but would like to stick with 12" of 15" drivers

Thanks,
Slice

NOTE: I relies that you guys are trying to help and I am still open to changing my mind to a different horn design but it must be able to reproduce bass to at least 300Hz. The reason I chose this design for now is because it meats that requirement of 300Hz or more. The fact that it goes to 40-50Hz isn’t bad ether for a DJ PA system. If you find a horn that can go lower then 40Hz and at least 300Hz at decent SPL (~100Db and UP) levels then please share it. Note: PLEASE DO NOT WASTE MY TIME WITH SITES WITH HORN PLANS THAT DO NOT REACH MY REQUIRMENTS (namely: 40Hz or less-300Hz+).
 

Brett

Member
2002-01-07 6:02 pm
Re: i relise that the LAB Horn goes lower but...

slicemaster101 said:
I'll take a loot at the 186 horn, but would like to stick with 12" of 15" drivers
Email Rog and ask for his opinion on what you want to do. He has years of experience in doing PA's for clubs and bands. He's also a talented designer, and whilst I've never had any contact with him directly, he was very helpful when he used to post on another board I frequent.

As for the scoop producing 40Hz, I'm sceptical, based on past personal experience with similar designs. Position in the room, and the transmissibility of the nearby surfaces will have a huge affect on the resultant sound. So too will the driver selected.

The other claim of 5k out of a 15"driver is ludicrous. It will become so directional above 1k and suffer tons of breakup modes it will sound like crap. Yes, yes, I know you only want 300Hz, but it does go to the credibilty of people making such claims.

If you decide to build this design, just email the designer and ask what he optimised it for.

Horns, even crappy scoops have a limited number of drivers that will work in any given design, possibly only one. As you have been told in previous threads, designing horns is about an order of magnitude more complex than a box, so unless someone reverse engineers it, who knows what's best.
The reason I chose this design for now is because it meats that requirement of 300Hz or more. The fact that it goes to 40-50Hz isn’t bad ether for a DJ PA system. If you find a horn that can go lower then 40Hz and at least 300Hz at decent SPL (~100Db and UP) levels then please share it. Note: PLEASE DO NOT WASTE MY TIME WITH SITES WITH HORN PLANS THAT DO NOT REACH MY REQUIRMENTS (namely: 40Hz or less-300Hz+).
Before you start shouting at people who have far more knowledge and experience than you, it would help if you specified bandwidth requirements. Horns by their very nature are bandpass designs and this MUST be specified so that the appropriate driver can be chosen and the horn dimensions optimised.

I'm so glad to see you've decided to be polite again, and I wonder why you bother asking questions of this board at all. You obviously know more than us.
 
Amen to that, Brett.

I know a fair bit of the theory, some of the physics, and much of the math behind horn design, but I know that I'm way underqualified and nowhere near experienced enough to do better than Tom has with the LAB horn.

Your comment about the Lab horn's limited top end is fair enough, Slice, but Brett is right about a horn being intrinsically bandpass in nature - you really should have posted bandwidth requirements first then.

Analysis of horns is quite difficult - I'm willing to bet most "scoop bins" and other PA horns out there right now haven't been designed particularly well at all - at least not to the mathematical rigor that Tom's done with his Unity summation aperture, and lab horn designs.

A 40hz -> 300hz bandwidth is quite doable, but unless you have a horn designed for one specific driver, and you follow those plans to the letter (with the same driver), you're likely to have an unsatisfactory result. Unless you know all the implications of changing a driver in a horn design and know how to use mathcad or something similar to make a model of the horn, it's not likely to end up terribly good.

If you have a driver you're planning to use, you'd be better off designing a horn around it than taking a current horn design and trying to "shoehorn" a replacement into it.

At any rate, I wish you the best of luck.
 
Sorry, Sorry I came across as angry of argent.

Sorry I came across as angry of argent.

Well, I am just getting frustrated with this project because he wants me to build him some horns but I know nothing about them. I looked around and found many appealing designs, but none of them fit the bill. If it were up to me I would do the lab horn for the experience. I am a very good wood worker and have made many complex designed speaker enclosures. I feel it is time that I try a horn but I don’t have the funding to do it. Then my friend came along and asked me if I could build a bass horn for his PA, and I told him I knew nothing about designing horns but I would look around for a proven design meeting his requirements (40Hz or lower and up to 300Hz or higher). I have not done much PA work because my main focus is home audio HiFi. Anyway for all who were turned off by some of my posts or got the idea that I thought I knew more then any of you, I know nothing about horns.

Please forgive me.

Well I was wondering if this thread could now become a design help thread.
I know you guys have better things to do then to help me design a bass horn but I thought I’d ask anyway. Here I go, will you guys please help me design a bass horn?

The requirements of this project would be as follows:

1. My DJ friend needs 2 15” drivers driving bass (whether it be 2 drivers in one enclosure or 1 driver in two enclosures). ***Lets figure out a good Eminence bass driver***
2. A horn capable of reproducing 40Hz or less (preferably less say 20-30Hz) and up to
At least 300Hz (note: a passive XO will supply high and low pass filters) with SPL levels of ~100Db or more (the higher the better).
3. Try to keep the design as small as possible with out compromising the above requirements. Lets say 5’x5’ or less per enclosure as a starter (note: if this is not possible bust make it as small as possible with out compromising above requirements)
4. This will be used outside and in decent sized venues, horns preferably will perform well in both conditions.


Well that’s it so now that I am in my place (simple novice) maybe we could get some constructive conversation going on to solve my little predicament…

Lets all agree on the Best Eminence Bass driver for the job:
Selection possibilities:
*EMINENCE DELTA P-15A 15" CAST FRAME DRIVER
*EMINENCE KAPPA-15LFA 15" LOW FREQUENCY DRIVER 8 OHM PRESSED FRAME
*EMINENCE MAGNUM 15HO
* EMINENCE GAMMA-15A 15" DRIVER 8 OHM
*EMINENCE LAB12 GEN II 12" WOOFER

Thanks So Much Everyone,
Slice

NOTE: I APPRESHATE ALL THE TIPS AND HELP YOU HAVE OFFERED THUS FAR…
 
Perhaps this is a case of go big or go home

Mr Slice.

About horn bandwidth: the bottom end is dictated by two things: the surface area of the mouth and the geometry of the horn (length, flare rate, etc.). A horn system's bandwidth will usually show a sharp cutoff towards the bottom end and a shallow rolloff towards the top end with the knee point given my driver parameters and again horn geometry. The LAB Gen II driver has different T/S parameters enabling the true bandwidth to extend to 150 Hz (as opposed to the old 80 Hz). Thereafter it starts showing a gentle rolloff and the directivity increased with frequency as well. However the amount of parallel surfaces will cause you grief at about 300 Hz because of the 1/4 wavelength causing a resonance (but so would any scoop or horn with parrallel walls)

In PA it is a lot more practical to go active than to use passive crossovers. For one they will cause a loss in sensitivity and a proper inductor for a 200-300 Hz crossover is bound to be large,expensive and non air cored. My suggestion would be to go active, the benefits are really big. An active crossover would buy you 3dB more maximum output (which is the same as doubling the amplifier power, read up Rod Elliots article on Bi-Amping 404 Not Found )and allow you to implement a higher order crossover, meaning you could bring down the crossover frequency and reduce distortion

The LAB horn is not exactly easy to build, but the only part more difficult than building a 186 or a scoop apart from the incerased material required would be the horizontal flare (not sure about the exact description, but the one with the multiple mitred angles). The effort would be really worth the effort, but then again not many people would actually ever push the LAB to its limits. The LAB's plans are also easily the best I have come across and every part to build is documented.

If you don't need much below 40Hz, then Rog Mogale's 186 might be an easier option. Horns that actually get to 30Hz (and slightly below in the case of the LAB) are few and far between.

The thermal issue was brought up because of the aluminium plate. It was actually just a measure to fit the driver's big magnet into the small space allocated for it and people got off on the thermal considerations. Thermal issues would not be an issue if you power the LAB and each cab should easily take in excess of 1000W contiunuous if driven within their bandwidth. Tom Danley has said before that one or two LABs in a corner should perform admirably, with two in a certain configuration (time for you to do some research on the LAB forum) should show an efficiency in the region of 30% and more (then add corner/room gain). I could hardly imagine a club that would ever utilize more than a dual LAB setup (configured as a mono sub in a corner). Even two on a floor should be more than enough for even demanding situations and is the minimum recommended use of a LAB horn.

The scoops have a horrible response and show a lot of peaks and dips in the mid-bass area. They may seem loud and offer an extended bandwidth, but that is about where their advantages end. Their geometry would dictate them not to be much good below about 50HZ and below that you'd have over-excusion going wild with attendant distortion. That, and you need drivers suitable for such a design, as with all horns. I can tell you that I have used McBean's horn design program and spent literally hours fiddling around with different drivers and what not and ended up with nothing even in the same ballpark as TD. The LAB is definitely about as good as it gets for a horn sub but one has to take care to use it correctly if one wants to use less than the recommended 6.

If you want to jack up on horn theory, point your browser to 403 Forbidden , you'll also find a link to McBean’s hornresp.exe program which is a gem. Whilst this is not a definitive guide, it is a good start. Horns are all about matching a driver to a horn and one cannot just put any odd driver into a random horn and expect it to work well. If you aren't really experienced with designing horns, something like a LAB or a 186 (with the correct and very expensive drivers) is likely to surpass your wildest expectations. Get the choice wrong though (as is likely with some of the plans one sees), and you might get reasonably loud, but it will lack the slamm and all the other characteristics well done horns are known for. In other words, go big or go home if you want horns.

If the LAB doesn't give you what you want ITO frequency extension, you can always add some EQ. If you decide to do an active XO, you might just as well. Perhaps you could give some more info on the top your DJ friend is using. Is it really a sin to use it from 200Hz and up instead on using it from 300Hz and up? I'd think that a higher order crossover and 200Hz is a much better choice than 300Hz and a low order crossover and a loss in sensitivity of a passive XO. You can always build one or two and add more later and even Bass Reflex enclosures wouldn't be out of the question. Two proper dual 15s or 18s can really kick and would be less effort, but then again this system is for outdoors use as well.

Enough of this. I have better things to do than ramble at people who show their appreciation for forum members' time (especially in the light of past transgressions) by shouting and demanding information just to apologize every time, but in my mind you are forgiven.

Martin
 
Mgoedeke,

You have to understand that the capital letters of the second “note” in my second post was not intended as “shouting” or as anger. It was simply meant to grab the reader’s attention. If you notice there is no “!” after it. Now since I have been misinterpreted so many times for the same offence, what do you suggest to make those “notes” stick out rather then all capital letters?

Well I gtg,

I will talk more on the subject later if you like, and thank you very much for the info.

slice
 
If you want to try some free front loaded horn design software you can find a MathCad model on my website. I have checked the model against HornResp and AJ Horn and it correlates very well. The advantage to using my MathCad worksheet is that I believe it gives a little more general flexibility in the horn geometry.

Martin
www.quarter-wave.com
 
I don't really have any qualms about the capitalisation. However there is a certain attitude expressed sentences such as
PLEASE DO NOT WASTE MY TIME WITH SITES WITH HORN PLANS THAT DO NOT REACH MY REQUIRMENTS
which do not come across as kind. I realize that you may have some obligation towards this DJ and that you want to get this person the best you can, but by showing brash behaviour like that you are only detracting potentially useful posters from investing time (= money/ time spent with family/ studies/etc) in thinking out useful responses and putting them into words effectively.

People will visit threads which they think warrant their attention. I think there is little need to market one's post and I know many people who as a rule wouldn't show an interest in people who don't at least show basic understanding of principles of mutual respect.

Another hint : Search. The seach capabilities of this forum are by no means the most powerful, but a little time and effort will in many cases come up with useful information, even if one has to browse through the result set a little.

English is by no means my strength and as such I have a world of understanding when it comes to people with difficulty to express their thoughts.

In this thread (http://www.diyaudio.com/forums/showthread.php?s=&threadid=6522 ), Ken L posted a link to what trolling was all about. Having a look at that page I found an excellent guide to posting on the web and can be found under : http://members.aol.com/intwg/ .

Before you post, give your post a little thought and structure it into logical, bite-sized chunks which follow logically on one another. Cut out what is not nessecary. Put the most important information towards the beginning or end of the end of your (short)paragraphs. That way people who are quickly browsing through a longish post will get the essence of what you're trying to say.

Only my 2c

Martin
 
slicemaster101, do your friend have any specs about max sound level?

15" speaker can take rather lot of power and amps are rather cheap. What about a closed box or a bass reflex?

If you are looking for a horn with high efficiency, I have a hunch of that you need a straight one (not folded).

Some calculation.

15" = 96 dB SPL at 1 m and 1 W (closed box)
Amp = 500 W

== 96 + (30 - 3) = 123 dB
 
I don’t know much about horns I can’t say for sure what is required in this instance. In other words I don’t know what type of horn would be used for a given situation. As some of you might know I have been tinkering with HiFi for some time now and I know that a sealed sub would probably get the job done indoors for my friend but from personal experience sealed and bass reflex do not react well to wide open spaces, such as ones in a park festival or a large outdoor party. I do not believe that amps are cheap, but I agree that it does take quite a bit of juice to drive some 15’s. High efficiency in PA as I understand it is a given. I know most horns such, as the Lab Horn that has been referenced many time through out this thread is very efficient. As for what type of horn he needs to reach his requirements, I don’t have the slightest idea what kind he needs. That is why I am here and asking questions and presenting his situation to you as a community who I know can help me with my problem because I have had great success in the past.

Sincerely,
Slice

Mgoedeke thank you for those sites:)
Peranders thanks for the idea but I don’t believe that a sealed or bass reflex design will be suitable for his various situations, but thank you for the presenting the possibility:)
 
Slice,

These horns are known as J-bins and are very well suited to the job your friend needs them for. I have used them extensively in sound reinforcement applications ranging from live bands to recorded music and particularly dance music.

I agree that they may not go much below 40Hz, but I think it is the "right" kind of Bass that you are looking for. Me and some guys I used to work with would set these J-bins up (the more the better!) and play bass-heavy music through them and stand back and grin wildly. It is the kind of bass that slams you in the solar plexus - quite fast and punchy. And loud. I think these cabinets are ideal for this application.

There are other designs out there that may be better, but check the price!

If you want higher SPLs or deeper bass - build more cabinets and put them side by side!

BTW, we used EV 15" drivers in them, rated at about 600 - 1000W, sorry forgot the model numbers. They sounded best with Crown Amcron Macrotech 2400 power amplifiers. about 1200W per channel I think.

:)
 
???

Well,
This is a little unnerving.
One person says the “scoops” would be perfect for my friend’s application and every one else says they blow. I am not sure what to believe. I have no clue as to what makes a good horn and what doesn’t but I am getting confliction feedback. At first I was sold on the scoop and then I was sold on not using the scoop and now I have no idea on what or who to believe. I am not saying that any of you guys are wrong I am just saying I don’t have the slightest idea on what I need now. More feed back would be greatly appreciated. And to those who suggested to design one from the driver up could I get some help with that? As most of you know I know jack about any type of horn and what would be the best choice for a given situation.

Thanks,
Slice

PS. For those who suggested that I design a horn from the driver up, I got the idea that you were going to help me design a horn, but I have had no such help. Was I wrong in assuming that you guys were going to help me design a horn?
 
Designing a horn is a time-consuming and difficult process. I could "design" you a horn, and it may even be better than the scoop you were going to construct, but it will be far, far sub-optimal.

There are very few people on this board who are qualified to really do a horn the justice it requires. I can count on one hand the number of people I'd deem able to do it well (and it wouldn't include myself), and none of those have enough free time to sit around here and play with us kiddies in our sandbox (so to speak.)

The proper resources have been pointed out to you already. Getting full custom designs handed to you on a platter is expensive, and will require large consulting costs.

Take the time to learn + absorb the material given. Play with some of the horn models + calculators and see how your favorite scoops, bass bins, or otherwise, will be have with different drivers.

Read up on the theory, and if you don't understand something, ask questions and we'll all do our best to help. This place isn't meant to be a free design service, however. You'll be a lot better served by learning what goes into making a good horn than just by getting one designed for you.

Seriously, designing a quality horn takes weeks of modeling, design, construction, measurement, deconstruction, epithets, and then more construction and measuring, until you have a good finished product. The urls given to you in this thread are already a good start, and if you can manage to digest them and spend a few hours playing around with the free tools provided, you'll be on your way.
 
Slice,

So as not to confuse you, I should state that I have absolutely no experience designing or building horn loaded loudspeakers, apart from re-coning a few drivers and doing repairs, etc.
I have USED a wide range of horn loaded P.A. speakers, and IMHO I think this design would be good for the application you have suggested. My experience is as an end-user only.

-Sure, the frequency response may not be particularly flat.
-sure, there may be other, more complicated designs offering better specs/performance. For the job you have suggested however, I think this design is a good choice. They are a tried and tested design.

I believe that "Hi-Fi" horn loudspeakers and Professional sound reinforcement horn-loaded speakers are a world apart; it is important to remember this to find the right design for the job at hand.
 
another rookie seeking advice

Hi everybody!

I just came across this thread by accident, and as I intend to build a pair of scoops, I decided to register and post some questions on that topic.

Like slicemaster, I found the plans for a scoop bin on the dancetech page some time ago.

I also had previously found some general information and formulae on horn design on the net (http://melhuish.org/audio/horn.htm, just to mention one).

As I have already bought a pair of Eminence Kappa 15 (which by the way should be quite suitable for horn loading according to the Fs/Qts quotient), I started to calculate the modifications I would have to do on the design from the dancetech site to fit it to my woofers, using the formulae from above mentioned site.
But unfortunately something went wrong:

1. I got some nasty results like a throat area of 0.5 m²
2. I'm not sure which formula to use e.g. for the compression chamber, since the formulae were intended to be used on a different design.

I would be glad if anybody could tell me, whether the formulae I'm counting with are crap, or if it's just that I'm too dumb to use my calculator ;-))))))

I hope I'm not annoying anybody