Replies to This Discussion

Permalink Reply by Todd Allen on May 6, 2011 at 6:27am

My rear deck speakers are Peavey NEO 10s.  They are roughly 20 lbs each.   The NEO 15s are much bigger and heavier.  They will produce substantially more volume, but you'll want a stronger amp.   I expect the 15s will be an awkward choice for the trailer you selected.  They also come in a 12 inch size which might be more manageable.

 

I've been fairly happy with the NEO 10s, but my preference is for smaller speakers.  Going with bigger speakers can net a modest gain in efficiency, but smaller speakers give more flexibility.

 

I recently bought Bazooka 8" concentric horn marine speakers on a half price clearance sale.  List price is ridiculous but if you can find them cheap they offer good performance for their size and weight.  These speakers pair nicely with the Sure amp.  They also come in a 6" size which might be manageable for direct mounting on a bike.

Permalink Reply by Spencer "Thunderball" Thayer! on May 6, 2011 at 7:43am

The N15s are 35lbs which IMO are worth the extra weight in both sound dBs and power consumption. However if I cannot get a solution to the size vs. trailer problem I may downgrade to the 12s. Which would be fine but they are almost the same price and from every review I have read significantly not as loud.

 

I believe just two 15s would be sufficient and I wouldn't need to attach any additional speakers. Though I wouldn't be apposed to it.

 

Anyway regarding the trailer choice. It's the cheapest and largest trailer I can find available. I do believe building one to suite my needs would be better but I don't know anyone who I could commission to do this. You're in this same field, do you know of anyone that can do it? This isn't a fishing attempt to get you to do it. : ) I understand you're a busy person with little time to work on your own projects much less someone elses.

 

Permalink Reply by Matt on May 6, 2011 at 11:25am

This is impressive! And something I have only begun to re-delve into, so it is helpful to me! Thanks.

 

Questions for you, though, for my own edification: will the 100 watt amplifier board match up well with your 400 watt speakers? My reading has lead me to believe the amp wattage should meet or exceed the speaker wattage, perhaps I have misunderstood.

 

Also, while I understand the desire to add a microphone, why would you want/need to include two or more audio devices?

Permalink Reply by Matt on May 6, 2011 at 11:27am

Third question: is there a concern that mixing several audio devices might diminish the sound of one?

Permalink Reply by Spencer "Thunderball" Thayer! on May 7, 2011 at 6:42am

As far as I can tell no classD(T) energy efficient DC amp really has the power to hit 400 watts standard much less the 800 max. There are a lot of car amps that will do this but those things, to my understanding, waist power in an unacceptable way. Todd is using only one Sure 2x100w and seems to be pushing it beyond the 100 watt capacity. But I have also read around that it isn't exactly true that watts equal loudness or quality of sound. Todd or Howard can you shed some insight?

But this is a concern of mine. I don't fully get how I can have a power efficient system and yet crank the sound. If I have to keep it quite while on DC and then blast it on AC that'll be fine.

Reason for the mic is pretty clear like you said. However for the mulitple sources thing I intend to use this for out doors DJing as well as mobile sound. If you have at least two sound sources you can move from one audio device to another seemlessly. This is important. Also important is to have a back up mp3 device playing while the master device is playing this way if the primary sound source fails switching to another source sounds clumsy but not like a total failure. Most of the time in a dance or club enviroment the audience does not even notice. Only other snobby DJs.

Any good mixer will ensure there is no loss of sound, it's what they are designed to do.

Permalink Reply by Far'arned Retrogrumpalunkus #63 on May 9, 2011 at 5:24am

Neat concept.

 

On the power supply issue to add AC charging you will probably not be able to run the system very well off of an AC supply while charging the batteries all with a single commonly-available 15A receptacle outlet -especially running off any extension cord unless you are going to carry around a massive #12 AWG cord around with you.  

 

I'm just running your power requirements off the top of my head and shooting from the hip but it looks like the best you can do is run off of the batteries while putting a charge into them with AC or just running off of AC and not charging the batteries.  

 

It's important that your AC to DC power supply be clean or you are going to have noise issues that you are not going to like while the system is running and charging (or just running off AC.)  

 

The simplest way to deal with the issue would be to just have a charger that is sufficently clean that you can plug it in and charge while running the sound system and not have hash or noise picked up from the power supply.

 

Of course you wouldn't really be charging the batteries much -just supplementing the power drain while it is powering the audio equipment.  Depending on your total power requirements you might still be going downhill on total charge state but not nearly as fast as it would be without the AC helping. It would depend on how hard you were cranking.  If you were actually able to charge while in operation it wouldn't be very much or very fast.  Just holding your own would be the goal IMHO. 

 

This really isn't that hard of a circuit to build but it might have a few pricey compoments like a huge coke can capacitor or two to smooth out the ripple from the rectifier circuit and the current or voltage-limiting clipping circuit that regulates charging curents/voltages so you don't overcharge and cook your batteries.  That kind of stuff is available online or at audio shops and maybe even American Science Surplus.

 

I bet you are not going to find much in the way of ready-made power supplies and chargers for this type of application but building one shouldn't be that hard.  There are plenty of charger circuits designed for mobile ham radio purposes online that can be scaled to this type of "performance audio" purposes.  The other solution is to have two separate systems. One to charge and one to power on AC.  That not only gets expensive but adds more weight and complexity. 

Permalink Reply by Spencer "Thunderball" Thayer! on May 9, 2011 at 7:04am

Todd, how do you both charge your batteries and power your setup? Will a 12v battery ever produce enough power to push the Peavy speakers with 400 watts?

Permalink Reply by Matt on May 11, 2011 at 6:06am

I just noticed that your amp boards have an impedance rating of 4 Ohms, and the Peaveys have a rating of 8 Ohms. If you look in my parallel posting on Speakers, you will find Todd warning against an "impedance mismatch," which caused my speakers to sound much quieter than they should have. I have since verified this to be true. Is this a concern?

Permalink Reply by Far'arned Retrogrumpalunkus #63 on May 11, 2011 at 6:35am

If one over-drives the mismatched impedance it usually isn't a problem I think.

Permalink Reply by Matt on May 11, 2011 at 7:00am

But wouldn't a 4 Ohm amp underdrive 8 Ohm speakers?

Permalink Reply by Far'arned Retrogrumpalunkus #63 on May 11, 2011 at 7:17am

Depends on the amp. Looks like the 100W/channel amp listed above might be under-driving the 400W speakers a bit.  An 800W amp probably isn't going to have much of an issue though.    

 

For the most part speaker impedance ratings are almost meaningless.  An 8-ohm "rated" speaker may work just fine driven at 4-ohms and in reality might really be closer to 4-ohms measured.  Impedance ratings are nominal. 

Permalink Reply by Spencer "Thunderball" Thayer! on May 11, 2011 at 9:17am

Even though impedance mismatching isn't really something to be too concerned about reflections on the load will cause a loss of power efficiency. It's something to consider.

 

The thing is since the PA speakers are not meant to be powered by a DC battery source I don't really think I will get a perfect match. The best I have found is the Pioneer GM-D9500F. Which says it's 8 ohms but then when I look at the specs it doesn't say anywhere near 8 in the rated power. The rated power is worse than the Boss mono amps. I am quite confused by the product description.

 

Matthew, if you know of a true Class D 8ohm amp that can deliver 400 watts you've got me sold!

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