Questions about Horn Lenses

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ogp

Member
2001-09-17 9:27 pm
Ohio
I am planning to build some speakers for dj/sound reinforcement use. They will all use eminence drivers. The setup will consist of two <a href="http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=290-460&DID=7"> 15" Kappas</a> in a ported 5 cu. ft. box and four satellites on stands (two for monitor use), more than likely containing one <a href="http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=290-403&DID=7"> 10"</a> or one <a href="http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=290-401&DID=7"> 8"</a> woofer and a <a href="http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Product_ID=7607&CATID=49"> horn tweeter</a>. I am still deciding on the size of these satellites and whether they will be closed or vented. This will be an active setup. My quesion is, how do I decide what type of <a href="http://www.eminence.com/Pages/EminHF/HornsF.html"> horn lense</a> to pair with my tweeter? I guess one deciding factor is where I am going to cross them over but I don't know the difference between the types. Could someone please explain the difference between constant directivity, bi-radial and radial horn lenses? What would be more suitable for my application? Thanks.
 
I don't know enough about horns to give you a break-down but I can give you a few ideas. The different types are all different attempts at getting a wide passband and dispersion.
Constant-Directivity horns are essentially hybridized designs, attempting to get the best of many designs.
Exponential and Bi-Radial are probably the most common.

As for the crossover frequency: horns have a resonance frequency which governs thier low frequency response. A lower cutoff means a larger horn. The woofers you have should play high enough for a crossover of 2500Hz.

I would not vent the satellites. The 15" you have selected plays high enough that you might as well go for small sealed satellites and a crossover somewhere in the midbass. There is no need for low bass of any kind to come from the satellites. Go for high efficiency and small size. Be careful of the max power handling. Depending on how loud you want it, 100W on the 10"/8" woofers might not be enough.

I might even consider scrapping having the 10"/8" woofers altogether. You could probably find a compression horn tweeter suitable for a midrange crossover. According to parts express the 15"s play to 3kHz, you could cross at 1.5kHz without difficulty. But I have little experience with pro sound, so don't take my word on that.
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
OGP:

If you don't get an answer on this forum-and really, I will be very surprised if you do not get an answer here from somebody who is experienced in PA sound-then you should know that Parts Express itself has a help line.

I would ask them if you do buy an Eminence horn driver and lens and cross over at 500 Hz-the lowest recommended crossover-do you need a tweeter and where should you cross it over.

Then ask the same question for those horn driver/lens combos that the lowest recommended crossovers are 1,000 Hz.

The last time I called Parts Express tech help was a few years ago, but they were very good. I assume they still have the tech help line.
 
PA system

Did you check out the 15" coax Beta. They make a few models where their Super Tweeter compression driver screws into the woofer and you use an adapter to mount the horn. They also make the crossovers to go with the different horns. Still very efficiant at 97 db but won't take as much power as the Kappa. Then again you will only have to worry about one box and I would guess taking the horn off for transport. Another thing, even though the Beta is I believe 150 watts instead of 400 they can and will permanently damage peoples ears if you even attempt to turn them up much. You are going to have 97 db of sound with 1 watt with the ability to take it up way past what humans can take even with what could be considered a low wattage amp.
 
I can't speak to the DJ applications, but with pro sound I've had experience both designing and building a number of cabs and using my system for 10 years or so.

First and in general, unless one is using rear/horn-loaded cabs, a 12" is generally considered a minimum/typical/ideal midrange or midbass.

Some companies (EAW, Mackie, JBL, etc) make cabs that are horn-loaded with 6", 8", or 10" drivers in the midranges down to the upper mid-bass regions, but this results in relatively large/heavy cabs and is done in order to get better projection, pattern control, and efficiency in the drivers' passband.

The overwhelmingly most popular mid-high pack is one or two beefey twelves with a good horn. The Eminence 12"'s would be a good choice, as would JBL's etc etc. But certainly the Emi's are a good value, particularly if one shops at some place like Image Communications. I've used a number of 12" & 15" Emi's and, like JBLs and some others, they seem to have pretty good voicing.

I've never really cracked the subject of (high/mid freq) horn design, it is a subject where there is even still a lot of compromises and differing opinions.

In general, there are a number of competing factors that must be played one against another in designing a compression-driven horn lense. Some of those factors include dispersion pattern and dispersion pattern as a function of frequency, trying to avoid having the horn display nasty resonances and other phase/freq-dependent problems, etc.

We've all experienced horns that DON'T do a good job of balancing those factors, typical characteristics include horn "squawk" and/or "nasaliness", and/or blistering SPL's (resonances) at particular frequencies or places in the dispersion pattern, and narrow or poorly covered patterns.

The market seems to have moved strongly to the constant-directivity designs. These are designs that try to make the dispersion more-or-less the same over the bulk of the passband. In my experience, constant-directivity horns tend to be some of the better sounding horns.

On the other hand, it might also be the case that the reason the constant directivity horns sound better is because a lot of the established companies are now using the design and they also coincidentally and in general do a better job of designing their horns.

As far as horn drivers go, I've had good luck with Emi's, and while not quite as good as JBL/R-H/McC/etc, they also don't carry the price tag. At least the Emi's avoid some of the bad/nasty characteristics that plague other lower-priced drivers, such as (again) squawkiness (resonances), poor voicing, that nasty metal "bite", etc etc.

A couple other words in passing. As Vance Dickason points out in his writings, even cone speakers (mid-basses and basses) have dispersion patterns in the upper reaches of their passbands. I don't recall the exact numbers and it varies with the size of the speaker, but 15"'s and to lesser extent 12"'s are already starting to become directional ("lobing") by around 1.5 kHz or so.

That is one reason that in general pro sound boxes tend to crossover at very low frequencies relative to, say, home hi-fi speakers. Most the better passively x-overed mid-highs/two-ways will be x-overed in the 1.2-1.6 kHz range.

The other reason for this is because the range of around 1kHz and on up to around 2.5kHz - 4kHz is *very* important to intelligibility and overall subjective sound quality. Using horns to cover that freq range allows one to better control the dispersion (audience/venue coverage) and the voicing (assuming one invests in good horns and drivers.)

I would not suggest the Emi coaxes for mid-highs, they are really intended for near-field monitoring. For example, I've had good luck using them in decent lower-cost stage monitors, particularly if one is talking about small-to-midsizish stages with lower stage volumes (such as small to mid-size churches, grange halls, etc.)

But the Emi coaxes are not appropriate for mid-high pack usage, at least in my estimation.

Good luck.
 
I'm new to DIYAudio and missed the thing in the newbies' FAQ about being sure to post relevant safety information.

In the spirit of that thought, allow me to state the following:

To anyone just starting out in the DJ/pro sound arena:

*Please* be aware that decent or better pro sound speakers will be both loud and efficient.

Driven by typical pro sound amps (250-1000+ true RMS watts continuous duty per channel), such speakers can do serious damage to hearing with even short exposure.

When working with "racks and stacks", ringing out monitors, etc, make sure that proper ear protection is worn (*always* have a pair of foam ear protectors in your pocket.)

Make sure that others, including staff/wannabes, security, the crowd, etc are kept far enough from stacks that they are not being subjected to such sound levels.

Flying speakers can help avoid such issues, but then there's the whole issue of spec'ing and arranging for rigging that meets or exceeds all the various standards *and* is engineered on-site to meet the challenges of the particular environment.

Similar caveats go for power (AC) distro, etc.

Sorry to sound like a fuddy-duddy, but quite honestly it never ceases to amaze me the chances people are willing to take in order to blast away with their new toys.
 
To answer your questions directly:

Should the boxes be ported? Yes. I won't claim to understand exactly why, but having built both acoustic suspension (as experiments) and vented (more typical design) pro sound boxes, I can say that both my experience and the overwhelming bulk of the rest of the market agree that vented is better.

At what point should you crossover to your tweeters? Well, the term tweeter is generally not used in pro sound, except for "super tweeters", which are different than what I believe you are refering to.

Assuming that you are in fact referring to your mid-high horns in a typical two-way (fullrange or mid-hi pack) design, then you want to cross over as low as possible (within reason and keeping the xover point above 1.0kHz and certainly at or below 2.0kHz.)

I think I covered the reasons for this pretty well in the earlier post.

A number of firms, such as Eminence, Image Communications (their off-shore house brand), Dayton etc produce and sell canned pro sound xovers with decent components (plastic foil caps, decent coils, etc.)

These xovers include 18 dB/octave high-pass sections, high-pass section overload protection, and variable gain (power shunt) controls on the high-pass section, all of which help to protect your expensive horn drivers.

If I were you, I'd select a pair of Emi 12"'s or a single 15" that meet your power requirements.

If you want to be able to use the mid-highs standalone for smaller gigs, you might consider the single 15".

If they will be used most often with subs and you want better mid-bass to mid range voicing, go with the dual 12"'s.

Spend the money to get good horn drivers, good horns, and the good xovers.

Also make sure that the impedance of the drivers matches the impedance required for the xover. If you go with two 12"'s, they need to be wired in parallel. This means you will end up with a combined impedance of 4 ohms (assuming 8 ohm drivers) or 8 ohms (assuming 16 ohm drivers.) Some of the Emi 12"'s are available in 16 ohms, getting 16 ohms 12"'s opens up your choices for canned xovers, since the bulk of the OTC xovers are 8ohm/8ohm.

Finally, as to the horn types. This is tricky. If you will be playing mostly in "bright" or "hard" or "cold" acoustic environments, you need to keep the sound directly-radiated by the horns off of the walls. Otherwise, you make nasty, harsh reflections, resonances, and reverberations more likely. On the other hand, if you play more frequently in "soft" or "warm" or "dead" environments, you want to cover the bulk of the space more completely with the horns.

It would be hard to go wrong with 60x40 horns (slightly narrower pattern, good pattern control, but still very widely used) or 90x40 horns (wider pattern, very common).

Having owned and used both, I'd tend towards the 60x40, but just because my jaded ears are tired of the blistering, metallic resonances that uncontrolled spill can produce at high volumes, and the lack of intelligibility that spillage can produce in reflective environments and even at most levels.

Hope this helps a little more.

- L

PS I hope you have access to and are good with a tablesaw. Use medite or marine plywood for the boxes. Lesser grades of composite (i.e. particle board) are generally too soft and weak, and non-marine plywoods tend to have voids and internal delaminations that can cause nasty buzzes.
 

Brett

Member
2002-01-07 6:02 pm
I more or less agree with everything Lance said in his last post, but don't buy components simply because they're in the PE catalogue. For instance the Beyma 380 is an awesome 1" driver and quite cheap (I'm not in the US so I dunno where to buy) that you'll have to spend serious money to better.
 
Lance and the others pretty much hit it on the head. Design the speakers for where you are going to be using them in. If outdoors, you want as wide as a dispersion as possible. However the wider the horn, the shorter the "throw". I would also take a look at many of the commercially made speakers now and try to copy their designs. (Peavey, JBL, EV, Yorkville, Community, Yamaha, etc) Most are horn on top, woofer on bottom config with the ports at the face.

Yes you should port the boxes, you can tune it around 55 or 60 Hz or so. I use a pair of EV Eliminator tops (pretty low end, but better then alot of the horn + 15s speakers out there). Typical crossover is usually 1.5k or so.

I wanted to do 2 12s and a horn but I couldnt find anything commercially available short of the JBL SRX (read $$$$$).

I too wanted to build my own PA speakers, however I just said scruit and bought commercially available ones. Maybe one day I will still.
 
Brett is right on with what he said.

I was trying to avoid being biased toward one outlet or brand versus another (and possibly being chided by a moderator, starting a flame war, or offending a company I deal with such as either Parts-Express or Image Communications.)

Anyway, yes, the P-E catalog is a great source of information and for getting an idea of what's available on the market.

But their prices tend to be a little high and at least in pro sound they seem to stock a lot of, umm, not-center-of-the-market stuff that looks the part on the glossy pages but just as obviously are not the real item.

For instance, they tend to stock and sell a very broad assortment of horns and drivers, but many of them have aluminum, plastic, or phenolic diaphrams and/or have laughably small magnets/bodies and/or otherwise just don't look like they're solidly and decently designed and built.

Since horn drivers with titanium diaphrams have penetrated the market at all but the rock-bottom price points, there's no reason to even consider anything else (not for standard mid-hi packs, anyway...)

On the other hand, P-E DOES tend to carry just about anything anyone else does, and because of that they represent one-stop, hassle-free shopping. And I can only give them glowing praise for their promptness, care in getting orders right, and their customer service.

Anyway, I hinted at this and I'll say it plain, one can hardly go wrong with Eminence, and Image Communications has about the best prices going.

Note that a lot of manufacturers use Eminence drivers OEM'ed into their own boxes, that list would include (at least past offerings) from the likes of Carvin, Yamaha, Fender, EAW, and doubtless countless others.

I've heard good things about Selenium and Beyma. However, while Selenium has offerings that can compete with Eminence at Image prices, most the rest of the market is not even close. If one were to buy Beyma, then one is approaching the cost of JBL/Renkus-Heines/McCauley and some of the others, and one might as choose their favorite out of that stable full of goods.

I'd disagree slightly with Mr Wong in one sense: It can very advantageous to build ones' own speakers. For instance, a 2x12" + horn mid-hi pack with Emi drivers and the usual assortment of cab hardware, horns, etc could be built for on the order of $300/each, assuming Image Communications pricings.

For that amount, one would be lucky to find entry-level Fender/Yamaha/Behringer/etc 1x15" + horn boxes that would be distant cousins to the DIY cab.

That being said, I have to confess that in general unless I'm making 4+ of any one box, it's questionable whether the savings justify the time and expense.

Cheers and good luck!
 

Brett

Member
2002-01-07 6:02 pm
Lance Delo said:
Brett is right on with what he said.

For instance, they tend to stock and sell a very broad assortment of horns and drivers, but many of them have aluminum, plastic, or phenolic diaphrams and/or have laughably small magnets/bodies and/or otherwise just don't look like they're solidly and decently designed and built.

Since horn drivers with titanium diaphrams have penetrated the market at all but the rock-bottom price points, there's no reason to even consider anything else (not for standard mid-hi packs, anyway...)

Now, I have a disagreement with you. Generally I find Ti diaphrams stink sonically. My BMS and Beyma phenolic diaphrammed drivers sound considerably better than any JBL, Selenium, PAudio and Eminence Ti drivers I've used, and the BMS have a hell of a lot higher power ratings, with no oil-can sounds. I'd rather have aluminium or phenolic any day.
 
I think I may try out PA speakers in the future for sure. Unlike home audio speakers, they dont have to sound super great, they dont have to look that pretty either. I'd like to do a horn + 2 12s and design my own crossover, thats still light enough to be stand mountable. Maybe I'll try it on a d'appolito design.

I'd like to get some more tools, like somethin that can do dado cuts and make better circles. O well some day when I get more $.
 
reply

For professional audio. All pro drivers only

6 inch-10 inch for midrange/low mid only 300hz-2khz

12 inch for bass/low mid 80hz-800hz [with the exception of Eminence Lab 12 which goes down to 30hz and can be used as pa sub.]

15 inch to lower bass/bass 50hz-300hz

18 inch-24 inch sub bass/bass 15hz-300hz

Ring Radiator bullet tweeters for super treble 4khz-20khz

1 inch compression driver 1.8khz-12khz
2 inch compression driver 800hz-4khz [plays midrange as well]

For pa, avoid piezo tweeters as they are harsh ear bleeding nasty sounding crap.

So for mid/high packs a 10 inch or 12 inch with a 1 inch compression tweeter and ring radiator titanium bullet supertweeter and 3 way x over

And 15 inch or 18 inch bass bin with either passive low pass filter or use an active crossover.

For various pa speaker designs look at www.dancetech.com under pa gear section for plans and www.speakerplans.com
 
I stand corrected by Brett's comments.

There are several common and acceptable horn diaphram materials.

I have heard (from a friend who is an engineer with a very large sound company) that phenolic in particular is a good material, it's pretty well damped (less resonance and "ringing" problems) and in general is thought of as "warmer" (less sterile or harsh or metallic) and more natural sounding.

On the other hand, he also stated that phenolics are more prone to failure -which makes sense given that both for a given thickness and as measured per unit of mass, phenolic is many-fold times weaker than titanium and more prone to fatigue failure modes.

And it's my observation from perusing specs and manufacturers glossy sheets that phenolics generally don't reach as high (their freq response tends to roll off at lower freqs.)

All that being said and again, Brett makes a valid point in that one should not discount phenolics outright and they do have their advantages.

In the end I personally find it hard to believe one can beat the bang-for-buck value proposition of the long established Emis on the one hand, or the long-established market-leading sound of the higher-end JBLs (titanium) on the other.

However, the phenolics Brett refers to are both more expensive than the Emis on the one hand, and virtually all other drivers (save for the most exotic and expensive) are cheaper than the JBLs on the other, so we're basically comparing apples to oranges...
 
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