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-   -   DIY 112-1 Budget Stage Monitors (requesting assistance!) (http://www.diyaudio.com/forums/pa-systems/220144-diy-112-1-budget-stage-monitors-requesting-assistance.html)

NoDestiny 21st September 2012 10:55 PM

DIY 112-1 Budget Stage Monitors (requesting assistance!)
 
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I tried searching both this site and Google for a while and didn't turn anything up for, what I would say is "Low Budget" stage floor monitors. I have designed/built speakers in the past, but it's been a while and I'm pretty rusty (not to say I was ever good at it to begin with.. :D).

I want to make ~4x 1x12" and 1x1" cabs. I first selected my drivers, based on price, user review, and application... here is what I came up with...

Woofer: Eminence Alpha 12a (8 ohm)
Eminence Alpha-12A 12" Guitar/PA Driver 290-405

Tweet: Eminence ASD1001 (8 ohm)
Eminence ASD1001 1" HF Titanium Horn Driver 1-3/8"-18 TPI 290-525

Wave Guide: ? (still researching)

The Eminence Alpha 12a seems to give about the power handling I think I need, a decent frequency response (never enough low end, but in this price range, it looks that it can get down to 100Hz pretty easily), and a name I'm familiar with.

The ASD1001 seems to be pretty unbeatable for it's price. Seems a lot of reviews have rated this as comparable to more expensive horn drivers, given the proper install of course.

After choosing my drivers, I started working on the crossover... this is where I'm pretty rough on the edges!

After looking at the woofer's response graph, I figured that it would be wise to start the crossover a bit earlier than the horn's 2.5Khz point, due to it's peak that starts out around 1.6Khz and tops at 2.3Khz, so I figure that a point of 2Khz should help tame that. The woofer is planned at only 12db/oct xover, where the horn is aiming at 18db/oct. I looked at 24db/oct, but parts seemed to jump the price by a little over $10 a cab, which started hurting the budget a bit more than I wanted.

Two other things that I figured would be a good idea: A zobel for the woofer, since it's impedance raises pretty hard, and an Lpad for the tweet (since it's like 10dB louder than the woofer). A few other things I considered throwing is: Fuses/bulbs for the horn driver as well as a ~16k 6db/oct lowpass filter for extended protection. The lowpass filter is to remove any inaudible feedback (if any) and the fuse/bulb in case of overload (especially from feedback... bulbs are cheaper than drivers!)

Attached is my rough design (never claimed to be an MSPaint master... lol). Everything looks like it should work. I plan to order the parts to make one first before dedicating to the others, along with some misc other parts to do some testing. Was hoping somebody could check my logic prior... ;)

As for the enclosure to put it all together, I have a friend who can get me some 5x5 sheets of Russian 12mm 9-ply void free plywood for a great price. With proper bracing, this stuff should be stronger than most 3/4" or 18mm stuff (who's back is going to complain in 20 years about having to left lighter-weight equipment?). The usual shape in design, probably aiming for 1.5-2 cubic foot of air (42-56L). Port the driver, of course, to get the most low end possible from them. The amp will take care of the high-passing, to keep the 80-100hz range out of the mix.

Outside of that, I plan dual speakon connectors, give them some sort of tough coating (Black, of course), full steel grill, 1-3/8" stand ability, etc.

As of writing this, I have a rough price of US-$157.63 w/ everything needed per, minus the bulb, coating, wood (and assembly pieces), and grill (so, drivers, majority of crossover, and misc hardware for cabs).

I'm sure there is plenty of error in my design... I'm hoping that somebody can comb through this and point those out. I have yet to design a crossover that somebody couldn't improve!

Thanx, gang.

Enzo 21st September 2012 11:56 PM

Parts Express, which you know since it is your link source, sells crossovers - both ready-made, and in parts. That includes bare boards onto whwich you mount your own parts. They also provide charts of component values for freq versus impedance.

Your list doesn't include the horn flare. You will ned one - using horn or horn flare in the Parts Express search shows a bunch of choices at ALL manner of pricing. There are two types of horn driver/horn flare - bolt on and screw on. Screw on also referred to as threaded. You 1" throat is a standard size of screw on.

NoDestiny 22nd September 2012 01:20 AM

Hi Enzo,

I have viewed their crossovers, but I don't think it is quite as optimal as designing and building your own. After all, the pre-built ones are pretty generic and are not designed for either driver, let alone both together. On top of that, it's a bit of savings by building your own. Finally, I need some new blisters.

The waveguide (horn flare) is still up in the air. I'm still researching which one would be best for my application, but at the moment my eyes are set on this one...
Selenium HM11-25 1" Exponential Horn 60x60 1-3/8"-18 TPI 264-306

It seems to be about the right depth for mounting, great on the budget, but unsure if something with a larger angle would be a better choice or not.

I definitely appreciate the input, though!

Enzo 22nd September 2012 02:01 AM

SO go half way and build your own on one of their bare boards. Crossover circuits are not complex, they tend to be laid out pretty much the same. And remember, you are building stage moniutors, not some hifi super listening room items. For example worrying about the impedance peaks. ALL speakers have impedance peaks, I;'d personally let the amp worry about that, and I assume in my work I am going to have good EQ on the monitor feed.

How much coverage area do you want from these? If you intend to plop it down right in front of your mic stand, then who cares about horn dispersal? Why have it spilling into the drum mics? Etc. Most speakers are rectangles, a lot of wedges are oriented "sideways" with horn at one end, narrow sides vertical, long sides horizontakl. But some wedges are made long axis vertical so they are narrower on stage, take up less room. Now if you want two moniutors to cover the entire front of the stage so you can run around, then you need more spread. So that is the sort of thing to consider when looking at angle of dispersion.

Since budget seems to be your motivating factor, have you shopped for used monitor wedges? You can get a lot of gear for less money in the used market. A couple nice used Yorkville cabs maybe or some Peavey product. Check with your nearby used gear stores.

And don;t write off new gear. A quick look at Musicians Friend and I find several inexpensive monitors - new WITH WARRANTY.

For example, at $109:

http://static.musiciansfriend.com/de...e_582081_V.jpg

NoDestiny 22nd September 2012 02:42 AM

Hi Enzo,

I'm always after a good DIY project, hence why I don't just simply "buy the cheap stuff". Plus, the cheap stuff just never sounds good, IMO. I'm pretty confident that the component selection I have would easily beat out most in its class for price. It's always a drag having to find the time to assemble everything, but again, I like the project work. It may cost a little more (almost double that of the item you listed), but in the end, I get what may be a much better unit that fits my needs more directly.

As for crossovers, let me go a little more in-depth on how I came to the conclusion on the ones in my OP. First, I analyzed the graphs provided by the manufacturer for frequency response and Independence. Then, I determined the crossover frequency to match the impedance. Finally, I used calculators found in Google (plenty of different ones, all giving the same results) to determine the component values.

For the woofer, I assume 8ohm because of the zobel, which just makes it easier to work with anyways. I realize one could work without a zobel, but it is something I used in the past that seemed to work really well, as well as gives a bit of "peace of mind".

The tweeter is ~10db higher than the woofer, so I used the lpad calculator (again, google) and figured out the value of components from that.

Thanks for the input on the horn. The ones I listed have been in my eyes as it seems to offer about the spread I think I want.

chrispenycate 23rd September 2012 06:22 PM

As somebody who has done lots of monitor mixes over the years, on many different wedges…
100 Hz is fine. You'll get the low stuff leaking in from the FOH system anyway, and frequently vibrating up from the stage itself. As regards crossovers, have you considered biamping? Power amps nowadays don't cost that much more than a decent passive crossover, and Speakons give you the essential connections. More, you can use only the twelve and have a guitar extension speaker.

Directionality depends on a number of factors, and while tight focus works for relatively static musicians, when you have a speaker for each artist it tends to give dead spots and feedback peaks when a vocalist is dancing across stage, or you've got a horn section (or multiple backing vocals) on one feed. Then, a wider spread is useful; I've been particularly fond of the 'pepper-pot' acoustic lenses, and if you look at their specifications you'll notice I don't recommend a frequency response up to 20kHz; ten will do me fine, and even seven and a half is no hardship. To reduce the beaming on the cone speaker, as you are taking it up pretty high, you can leave a slab of wood across the middle when doing the cutout. This not only cuts the high frequencies from the dome some, and adds lobing (not very HiFi, am I?) but adds valuable protection when musicians kick, trample or trip over it.

I admit to having a weakness for sidefills in these situations (FOH engineers hate me, but not the artists). And, if I can't manage an active drum stool (a twelve inch speaker feeding directly into the most sensitive region of a drummer, slightly cushioned and on a swivel support) I go for an over designed drum system; sitting among the cymbals and skins many drummers require excessive levels to function.

From experience I don't suggest amplified speakers; more difficult to hump, the electronics undergoing more mechanical misuse and less easy to cool (yes, I know you weren't suggesting them, but thought the information should be on the thread). Make sure they have handles that work from several different directions, and I'd consider a hole for stand mounting. You can reduce weight by using thinnish ply (is 19mm about three quarter inch) and damping panels with softboard and bracing, as long as the corners are good and solid. I wouldn't use chipboard; not just because it's heavy, but because it tends fragment under the treatment wedges get.

Since wedges get used in vast numbers of positions, it's really nice to have two connector panels. Very few commercial products have noticed this.

pinkmouse 23rd September 2012 06:41 PM

Absolutely nothing there I'd disagree with Chris, though I would add that a peak of around 3dB at about 1k/1K2 helps clarity no end.

NoDestiny 23rd September 2012 07:26 PM

chrispenycate: Thanks for your reply. I did consider doing a biamp setup. After looking at the cost of passive crossovers versus the price of a second amp, I concluded that at 4x of these monitors, it was better on the budget to go with the passive crossovers. Should I build 6+, the 2nd amp would be cheaper (looking @ brand new pricing, of course). For now, I think I would want to go with the passive crossover setup, if nothing else than for simplicity. Should I ever upgrade these (as I'm sure I will some day..), a biamp setup would be a no-brainer. If I wasn't trying to build an entire PA system on a tight budget, I'd definitely do it now.

Additionally, if I end up building more in the future, I can always convert them to bi-amp then. Hopefully, I'd just end up selling them and use the money to invest in higher end ones... but the future is untold and the budget is low at this time. ;)

Do you have any example pics of said 'pepper-pot' horns? I'm a very visual learner. :)

I have Pen-Elcom M1551 tripod mounts on my full list of things to get per cab. At $7.80 each, it seems pretty worth it. I don't have any stands yet, but I plan on getting a pair.

Having a drummer of my own, I hear ya on getting them satisfied with sound. Worth blasting their ears off, though!

I actually did look into making active monitors, but the price seemed to go up. I like the idea of having adjustable volume per, but it's not necessary and the complexity in design also swayed me away.

I'll have to budget in some basic handles for these... not sure how I want to go about those yet. Probably some of those spring-loaded ones on the sides?

I have access to 12mm void free 9-ply plywood (from Russia) that comes in 5'x5' sheets that I plan to use. Heavily braced, of course.

pinkmouse: One nice thing about this setup is the eventual addition of an EQ. I'll definitely be picking up a 30-band in the long run dedicated to the monitor system.

pinkmouse 23rd September 2012 08:01 PM

A separate EQ is a good thing, but if you can choose your drivers and crossover to give you that boost without, that's even better.

As for handles, don't go for spring loaded, they eventually start to rattle and are really annoying. The recessed ones with a bar across, (as in that pic above), are much better, and if you're a cheapskate like me, just router in a slot big enough to get your hand in and make up a shallow box behind to seal it off from the rest of the cabinet.

tinitus 15th December 2013 12:05 AM

anyone heard the new active stage/floor/wedge monitors ?

(some are cheap, and some are very expencive)


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