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Old 4th October 2002, 11:23 PM   #1
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Exclamation HELP! - With REAR HORN LOADED SCOOP BASS-BIN from www.dancetech.com

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.
http://www.dancetech.com/aa_dt_new/pa/15-scoop.cfm

Well thanks,
Slice
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Old 4th October 2002, 11:37 PM   #2
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If you want to build something a little more professional, and a LOT better, build the LabHorn that Tom Danley designed.

http://www.prosoundweb.com/lsp

It'll be about $150 each for the drivers (LAB-12 from partsexpress.com), but it'll outperform that bass bin easily.
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Old 4th October 2002, 11:46 PM   #3
Pilkar is offline Pilkar  Argentina
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Default try here...

try here... he has excellent bass bins designs... ang he is very helpfull too...

http://www.speakerplans.com

good luck!

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Old 5th October 2002, 12:14 AM   #4
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Thinyness, Pikar,

Both of these have been suggested before. However.....

The Lab would give the best performance, but unless you're doing a larger rig, I'd go for Rog's 186 Horn with an Omega 18.
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Old 5th October 2002, 12:29 AM   #5
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Smile 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+).
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Old 5th October 2002, 01:34 AM   #6
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Default Re: i relise that the LAB Horn goes lower but...

Quote:
Originally posted by slicemaster101
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.
Quote:
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.
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Old 5th October 2002, 03:22 AM   #7
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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.
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Old 5th October 2002, 07:07 AM   #8
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Unhappy 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 buy 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…
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Old 5th October 2002, 10:09 AM   #9
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Default 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 endwith 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 http://sound.westhost.com/bi-amp.htm )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 Mc Bean'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 http://melhuish.org/audio/horn.htm , you'll also find a link to McBeans 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
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Old 5th October 2002, 11:55 AM   #10
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Mgoedeke,

You have to under stand 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
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