Forums Music Sound Engineering A Technical Foundation To Building A Sound System: FAQ

This topic contains 5 replies, has 5 voices, and was last updated by Avatar grindcore_hooligan June 21, 2006 at 8:24 am.

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  • #1035762
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    Techno Viking
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    Question:

    How do you feel about the Cerwin T-250 to go with T-36s as a mid-high cabinet? Is there a better choice for (underground) dance music?

    Answer:

    The problem with the T-250 is that it has a cutoff of 90Hz, and because it has only a 10″ driver, does not have much ability to move large volumes of air, so you simply can’t get percussive *impact* from it. The V-253 is definitely a better choice. That has a cutoff of 35 Hz, and would definitely give a fuller, richer sound than the T-250. The other thing is that the V-253 is a full-range cabinet, whereas the T-250 is not. An advantage of full-range cabinets (aside from the fact that you get a lot more bass and percussive impact), is that for smaller gigs (a house party for example) you can bring just the full-range cabinets, and that’s all you need. The T-250 is only a mid-high cabinet and thus it is completely useless by itself.

    Question:

    I’ve been reading and learning a lot about the technical side of building a system that is loud, crisp and hard to blow up. We have very limited resources, so we might build the speakers ourselves. We will probably use the old Fane book for speaker designs.

    Comment:

    Keep in mind that it’s a lot more difficult than it looks if you want them to sound really good and be very solid electrically… But, it’s a good learning experience, so if you have a lot of time to spare, it might be worth it. Many speakers on the market have literally decades of engineering behind them though, so you will have to do a lot of research and testing and fine tuning if you want yours to sound as good. Also, it does end up being pretty expensive building your own anyway, once you add up all the dozens of parts costs (which you pay retail for but manufacturers buy in bulk and pay wholesale for). What you spend will be probably 80% or more of the cost of just buying some good speakers outright.

    Question (continued):

    For starters we are planning on building a 3-way system, with 2 18″ W-bins, 2 double 15″ courtbins, 2 double 12″ mid-low speakers, and 2 speakers with a horn and a bullet tweeter in them, using a passive crossover to split between the horn and the bullet. So I need a 3-way crossover, right?

    Answer:

    First off, we advise against using separate cabinets for everything. Also, stay away from non-sealed bass bins. They are much easier to blow than sealed designs (such as the Cerwin-Vega SL36). L36 style cabinets are more efficient and put out twice the bass, due to their exponential folded horn design. We strongly recommend going with SL36B or T-36 bass bins. Also, for what you get, I think they are priced very reasonably. So, put the mid bass, mid, and high drivers in one cabinet, and then yes, you’ll need a 3-way passive crossover inside that cabinet. Use a 500Hz – 750Hz crossover frequency on the bass drivers, and be sure to use a 6dB/octave passive crossover design. (http://www.the12volt.com is a good website by the way which has lots of info on building crossovers.)

    Question:

    You say that you never use crossover modules in the signal chain for full-range cabinets. I understand the reasons completely, yet in the manual for EV Eliminator cabinets, they say that we have to filter any signal below 40Hz because the Eliminators cannot handle subbass frequencies. Have you worked with Eliminators and do you really run straight signal into them?

    Answer:

    Definitely. The driver may not be able to handle as much power at 30Hz then at 50Hz, but that’s fine – just run it at a little less power. It’s much better that it put out as much low frequency bass as it can, than it put out a bunch of mid-bass. Look at it this way: Those 15″‘s should be putting out the exact same waveform as a kick drum would.

    So is EV wrong to suggest filtering out the subbass? No, they are just trying to prevent incompetent sound people from blowing out their speakers. But if you know what you are doing, know the limits of your speakers, and you configure your system properly, then you don’t have to worry about that, and they will sound better as a result.

    Question:

    How much RMS do you recommend supplying full-range cabinets from the amps? How do you ensure that the drivers won’t blow?

    Answer:

    It is easy to tell because the speakers will sound like they are distorting. If you have a good ear for things, then after a while you just get a feel for when a speaker is at its max. Then just back it off a few percent to be sure. Also, the amps should never be run such that the clip/limit lights flicker more than occasionally. If your amps are rated for the program power of the speakers, and you set them so the clip/limit lights very rarely come on, and the speakers sound good, you’re all set.

    Question:

    I am trying to build some folded horn subs like the Cerwin-Vega SL36 but I can’t find any plans. Can you help?

    Answer:

    I would not recommend building your own unless you have A LOT of time on your hands. It would take you probably 50 – 100 hours of labor for each one, and cost you 80% or more of what new ones would. You might be surprised how the parts costs add up. Cerwin-Vega does very high quality work, which can’t be matched unless you have about $20K in shop equipment. Also, the drivers they use are very good, and expensive. If you don’t use the same or very similar, they won’t sound good. We have seen (and heard) some homebuilt L36s and they are junk compared to the real thing! If you still insist on building your own though, here’s a drawing: http://www.unrec.com/sunsonic/l36.gif

    Question:

    We bought an old JBL rig consisting of 4 W-bins, 4 mid cabs with one 12″ driver each, 2 horns with a 2″ compression driver each and 2 high cabs with two bullet tweeters and a 1″ compression driver each. We want to run the rig 4-way. The bullet tweeters have filters to split the frequency, but the rest doesn’t have any filters. We were thinking of buying 2 Behringer crossovers, which are 4-way mono, and have adjustable cutoff frequencies. What crossover frequencies do you recommend?

    Answer:

    Don’t buy an active crossover, unless you use it only as a low pass filter for the bass. The Behringer should be fine, although make sure you can return it if you don’t end up liking it. For your bass signal all you need is a cheap active crossover or low pass filter which you could build. For the mids, buy or build some simple 6dB/octave passive crossovers. Run the 12″s up to around 2 or 2.5 KHz, and the horns above that. For exact frequencies to set your crossovers at you should look at the frequency response graphs of the different drivers and see where they start to fall off. Pick the crossover frequency such that your combined response from both drivers is maximized. On the high cabinets just use a 6 or 12 dB/oct passive crossover with a cutoff of 10KHz or so. On the mid cabinets, don’t filter out the bass or highs. One 6db/oct crossover for each cabinet is all you need. 6dB/oct. passive crossovers are very inexpensive, because it’s only 1 part – an inductor for low pass or a capacitor for high pass.

    The passive crossover approach will save you money, make things easier to connect, and you won’t need as many amplifiers. Though the frequency response may not be perfect, the transient response will be outstanding. Remember, only your bass needs to be super loud. Everything else can be a simple design because you don’t need the mids or highs to be too loud.

    Question:

    Is 80Hz the best cutoff frequency for bass bins? I heard some people talking about 125 Hz. The JBL 18″ driver can handle between 30 and 800 Hz.

    Answer:

    80 Hz is good for L36 type cabinets. For W bins, a higher frequency is better. 100 or 125 Hz is probably good. So, it depends on the type of cabinet. Also, if you have no 15″s or 18″s in your full range cabinets, you will (unfortunately) need the bass bins to supply more mid-bass. The best way to find the exact frequency to use is just run the system and find the frequency that sounds the best overall. Note that this may also depend on the venue. For example, If you have to do a small side room that has bad acoustics, there may be some midbass resonant peaks in the room’s frequency response. In this case, a 125 Hz cutoff on the bins might be too high.

    Question:

    How does the dB/octave thing work? I understand that at a certain frequency the signal is cut, but why is 24dB/octave too much. What exactly does that mean, that the cutoff is at 24dB/octave or 6dB/octave?

    Answer:

    A capacitor or inductor by itself has a frequency cutoff rate of 6dB/octave. That means 6dB less signal will get through one octave away. It’s a long story, but the important thing is that you don’t need anything higher than that for dance music, because percussion is what is important in dance music, not sharp cutoffs or high power handling.

    Question:

    I am a one-man mobile dj who is obviously concerned about portability when choosing a sound system. Are you familiar with the Bose professional series of loudspeakers and if so, how is the Bose Platinum system (consisting of Four 802-II loudspeakers and Two 502BP loudspeakers) for a mobile DJ catering to mostly younger crowds with a mix of hip-hop and electronic/techno style music. Also, I have a question about levelers. Would you recommend the Behringer Ultracurve Pro over a basic leveler–cost not being an issue? What are some good basic levelers?

    Answer:

    I have not used the Bose system before, but I can make a few observations from their specifications. I would estimate the sound quality is very good, but, the maximum output level is pretty low, and the bass cutoff is 55Hz. So it does not put out much bass, or much of any frequency range for that matter. If the total system cost on this is under $1000 it might be worth looking into, otherwise I would suggest going with 2 full-range cabinets. A system consisting of 2 EAW LA325’s for example would provide 10dB greater max. SPL and give you more bass. 2 LA325’s would be less in total system weight, would be easier to transport, would require fewer amplifiers, and I’ll bet would provide the same or better overall sound quality. The LA325’s go for about $1500 a piece. The Cerwin-Vega V253 or PS-152 are also very good cabinets and are under $1000 each.

    Question (continued):

    This system goes for around $5000 (not including amplifiers). The 802s are about $700 each (times 4), the 502s are about $1000 each (times 2) and the system controller is around $400.

    Answer:

    I’m surprised Bose is asking that much for that system, considering it only puts out 123dB max SPL. If you do have that much to spend, you might want to look into some Funktion-One Res 2 full-range boxes. They are very clean, and very loud for their size (about 13dB (20x) louder than the Bose system, according to the specs), and probably better sounding. Check out the Res2 data sheet at http://www.funktion-one.com/res2.htm (The Res2’s run about $3K a piece.) For the money the LA325’s or Cerwin-Vega V253s or PS-152s are half or a third the cost but are also very clean and probably a better value for most applications. Carvin, Yorkville, and PAS are also brands that are worth checking out.

    For levelers, I would suggest a dbx DriveRack or other similar controller, as these have some limiting functions built in, and act as a crossover and EQ as well. Otherwise, a digital mixer or a Behringer Ultracurve might work, though with those you would still need a separate crossover. Also check out some multifunction processors such as the Rane RPM 26v. [We tested the Symetrix 422 AGC leveler recently. Its limiter is very non-musical sounding and has a very short release time, making it useless for leveling.]

    Question (continued):

    You mentioned the Funktion-One Res2 cabinets. Do these have to be ordered directly from the factory or do you know of some good dealers – or even some place where I could pick up some used ones in good shape? A few more questions concerning the Res2’s, how’s the bass response, can I get away without a sub for a while? Can they be stand mounted? How much power do you recommend for the Res2? Right now I have a QSC PLX-3002 and a QSC RMX-2450.

    Answer:

    Funktion-One has several US dealers, check their website at http://www.funktion-one.com for contact info. They should be able to arrange for you to demo the Res2’s somewhere near you.

    Another option that may work very well for you is the NEXO PS15 system. They are less expensive and have an optional subwoofer that extends the frequency response to 30Hz, and there is also a matching controller for the whole system. (Martin Audio also has a similar system to this which is very comparable in quality and is probably similarly priced.) With 2 PS15s and 1 LS1200 sub, you’d still be about $500 less than the cost of 2 Res2’s. Check out http://www.nexo-sa.com for more info. If you call the US NEXO office, chances are they will know of an install near you where you can hear a PS15 system.

    Once you’ve had a chance to hear the above 2 systems, make sure you also hear what a Cerwin-Vega system with 2 T-36s and 2 V253s or PS-152s sounds like. Cerwin-Vega is really a leader for performance to price ratio. A $4K Cerwin-Vega system may not sound as clean as the other systems I mentioned, but will still be very good sounding. A 4 cabinet Cerwin-Vega system with a controller but no amps would run about $4K, whereas with NEXO, 4 PS series cabinets and a controller would be around $8K, but would sound a little more accurate (though if you EQ the Cerwin-Vega cabinets right they might actually sound better), and would be more compact and easier to transport. With Funktion-One, 2 Res2’s and a controller would be around $7K, and that’s with no subs.

    So you have a lot of options… I do recommend Cerwin-Vega overall for the money, but it’s worth your time to have a listen to the other systems I mentioned and draw your own conclusions.

    Regarding used stuff, I have not seen any NEXO or Funktion-One cabinets for sale on any of the used equipment sites. Those cabinets are just so good sounding that I don’t think anyone could part with them.

    Question (a comment actually):

    I’m currently trying to fix up my car sound system, well it’s not exactly a PA, but the idea is the same, so I’ll try setting it up according to your guidelines and see how things go.

    Answer:

    Cars are a nice thing to do sound for: Because the enclosed volume is small, it’s easy to get good bass response. One thing you may want to try in your car is play a swept frequency square wave. Then record it with a measurement mic (the ones which have flat response down to 20Hz) and look at the waveform in a wave editor, and make adjustments to your crossover settings until the resultant waves look as even and correct as possible at all frequencies.

    With car audio EQ is important by the way, since any small enclosed volume will have resonances which need to be compensated for. For that, play some white noise, record for about 1 Minute while moving the mic around to different areas in the car where you want the frequency response to be the best, and then look at the FFT spectrum in a wave editor or high accuracy audio analyzer. For the EQ, a good parametric EQ is the way to go.

    Question:

    I am currently in the process of putting together a small system for private venues. Based on the knowledge I have gathered so far, I have purchased four Cerwin-Vega T-36 bass bins and two Cerwin V-253’s. I am now looking into purchasing some Crest Professional amps to power them. What model(s) do you suggest?

    The next step will be to get the rest of the pieces. I know I need a leveler and some crossovers, but that’s all I know. I understand I should use an active crossover on the bass bins and minimal phase delay crossovers for the full-range speakers. But what kind? Also what kind of cables should I be using to hook all this up? […] I have a mixer but I’m looking into buying a new one.

    Answer:

    Start out with a good professional grade mixer, cartridges (higher-end Ortofon or Shure), and turntables (Technics 1200MK3 or high-end Vestax), and a limiter or leveler.

    The only other thing you will then need is a low pass filter or crossover for the bass bins. It should be set at 80 Hz frequency. Only use it for the bass bins, do not run the signal for the full-range cabinets through it. Any inexpensive stereo crossover will do, just make sure it has XLR ins and outs (stay away from anything with RCA jacks). And by the way 2 V-253s and 4 T-36s is an excellent choice of cabinets for dance music.

    For amps, a Crest CA12 or 8001 would be good for the 2 V-253s. A Crest 9001 would be good for the 4 T-36s Stay away from any lower cost amps than the Crest Pro or CA series. Lower grade amps can cut out if overheated and the audio quality may not be as good.

    For cables, use 10 gauge cable if possible. 12 gauge cable is OK for short runs (less than 25 feet), but avoid it if possible. It does not matter what brand as long as it’s thick, fine stranded, oxygen free cable. For signal cables, make sure the plugs are gold plated, and hold tightly, and that the cables look like they can take some abuse. And always have some spare cables on hand in case one breaks.

    Question:

    I have two questions: What do you think of active speakers in general and the Mackie SRM-450 in particular? And do you have any advise for anyone wanting to learn about sound engineering and sound systems?

    Answer:

    Regarding active speakers, their overall quality and cost-effectiveness are lower than what is available with passive speakers and the large number of high quality amplifiers available. Active speakers are easier to transport and set up however, making them ideal for portable and rental applications. In the next few years, better active products will become available and their cost effectiveness in smaller sound systems will begin to approach that of passive speakers, making them a better alternative in almost all applications. Advances will also occur which will allow simple system management of all active components via a single cable (carrying power and multitrack digital audio and control signals) chained between any number of system components. Most pro systems will adopt this design over the next 10 years or so.

    The Mackie SRM-450 is a good speaker for rental applications since it is so easy to transport and set up. It sounds decent and has a good output level, but in terms of sound quality it is definitely far behind some passive alternatives at the same price. It is an ideal choice for a monitor if you are buying only one however, because the passive alternative is more cost effective only if you are getting two or more speakers (since most pro amplifiers are stereo).

    About learning the science of sound, the best place to start is with the web. There are 100’s of websites relating to pro sound, and they have all the info you need. There are also messageboards such as http://www.live-audio.com which are an excellent resource. If you want to go further than that, I would suggest that you study engineering.

    Sunsonic provides sound system design, evaluation, and reinforcement services for clubs and events and may be contacted at: sunsonic@unrec.com

    This document © David X (United Records, Sunsonic Sound System) – http://www.unrec.com/ & http://www.unrec.com/sunsonic/sound2.htm

    #1061373
    Avatar
    Anonymous

    I need the drawing for the Cerwin Vega T-250 Mid/High enclosure

    #1061375
    Avatar
    elretardo87
    Participant
    Salu wrote:
    I need the drawing for the Cerwin Vega T-250 Mid/High enclosure

    I doubt you’ll find a set. They don;t tend to release plans for commercially produced speakers.

    #1061374
    Avatar
    BioTech
    Participant

    I must say that I find some of the statements by sunsonic throughout their technical guide to be wrong and a little missleading. Not that i’d want to attempt such a guide though.

    But I must also say that after being involved with pro audio for a while now, i’ve found that a lot of the theory is a matter of personal opinion and open to debate.

    It’s like a bloody artform.

    #1061377
    Avatar
    grindcore_hooligan
    Participant

    check out martin audio, they’ve got some serious equipment for not alot of cash. you can pick up MA wi some crown amps to run about a 12k rig for next to nothing, check ebay.

    #1061376
    Avatar
    Raj
    Participant
    BioTech wrote:
    But I must also say that after being involved with pro audio for a while now, i’ve found that a lot of the theory is a matter of personal opinion and open to debate.

    huge amounts of so called fact is in actuality somebodies pet theory; i did sciences at uni and one of the first things the lecturers said is that mostly the ‘laws’ are accepted theories which model the facts fairly accurately – not in any way fact

    :crazy_fre:crazy_fre:crazy_fre

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