Impedance Load Question
I’m hoping their are some audio experts here that can help me. I’m considering buying a Peavey xr 684 from a friend. It’s rated at 200 watts rms @ 4 ohms stereo and 420 watts rms @ 8 ohms bridged. I want to run it in 8 ohms stereo. This should be safe correct? Is there a way I can calculate the wattage loss?
For now I don’t want to wire it parallel and bring it down to 4 ohms because the amp doesn’t have binding post outputs. I want to use my trs-trs 1/4" cables.
I ended up finding the answer myself. I thought I should post the answer for anyone searching the forums for the same reason in the future.
If an amp is stable down to 4 ohms, then it is also stable at 8 and 16. Running a 4 ohm stable amp at 8 ohms necessitates a wattage loss up to 50%. For example, an amp that delivers 200 watts at 4 ohms may only push out 130 at 8 ohms.
Impedance Load Question
Hey DJ NiteFlite,
Where did you find the info on Ohms and watts calculation?
I have an older Audiopipe 1500 amp that is trying to push 2 1000w floor speakers with 18s (using 1/4 inch mono cables). I’m only able to turn amp up to around 50% before clipping starts and sound deteriorates. I’m only a hobbyist and still learning but pretty sure something isn’t right.
My configuration is:
Computer → Mixer → EQ → Amp → Speakers
Thanks!
Scott
Can you post a picture of the amp? I can’t seem to find any info on it
Impedance Load Question
Thanks Chef!
Here’s what I could find about the Audiopipe APA-1500. I assumed by the model number that it was 1500 watts but perhaps that’s not correct. I also assumed that my speakers could handle 1000w since I put 1000w 18s in the cabinet …turns out that the cabinet has a label that states peak is 400w. I bought the speaker cabinets and amp from a reggae band. I had to replace one 18" because it was sounding blown (my first sign that maybe these items don’t really go together as they were using them). Anyways… here’s my mix-match of components, any help and suggestions would be greatly greatly appreciated:
Audiopipe APA-1500
input impedance: 10k ohms, unbalanced & balanced
input sensitivity: 1.15v
output power: 8ohms/ stereo 150 watt/channel
4 ohms/stereo 200 watt/channel
4 ohms/bridged 430 watt
frequency response: 25hz-25khz +0/-1db
total harmonic distortion <0.3%
signal to noise ration: 100db
weight: 33.7 (lbs)
These are the settings I currently have on back of Amp:
MODE Options: Parallel, Stereo, Bridged (Stereo selected - although Parallel might be better?)
SENSITIVITY Options: 1.44v, 1.0v, 0.7v (1.0v selected)
NORMAL or COMPRESSED: (Normal selected)
GROUND Options: Lift, GND (Lift selected)
Speakers:
They are large floor-speakers like you might see at a swap meet. In the cabinets are 1-18, 2-Horns, 4-Tweeters. They are heavy loads of crap but they sound better than the 12" name-brand portables that I occasionally rent. Here’s the specs:
Zebra (brand) Pro XL Series Z-1832
Woofer: 18" with kapton voice coil
Tweeter: 4 Super Bullet 4x5 Tweeters
Horn: 2 4x10 Super Magnetic Horns
Frequency Response: 32Hz - 20.000Hz
Power: 400 Watts Peak
Impedance: 8 Ohm
Sensitivity: 101dB
Size: 35"(H) x 24"(W) x 17"(D)
Weight: approx. 78 lbs
Designed in UK
Link to amp:
Link to speaker:
[quote]I have an older Audiopipe 1500 amp that is trying to push 2 1000w floor speakers with 18s (using 1/4 inch mono cables). I’m only able to turn amp up to around 50% before clipping starts and sound deteriorates. I’m only a hobbyist and still learning but pretty sure something isn’t right.
[/quote]
Dude you are only getting 150 watts into those boxes .. you need a bigger amp.
Since you have changed the rating on the box, so the stickers mean jack shit 
You might need to change the crossovers to handle the different drivers.
Depending on the speakers you replaced them with your resistance may have changed to something odd (e.g. 6ohm).
Impedance Load Question
Thank you deevey,
If you read my last post (below) it might make more sense …but your volume settings comment brings up another question. What is the optimum (volume) to set each component in the string? My configuration and output levels typically look like this:
iMac Computer (volume max)
-to-
Small 2ch Mixer -not amplified- used as master volume (usually around 25% - higher makes amp clip)
-to-
Equalizer (set at 0 gain)
-to-
Amp (maxes out at 60% before clipping)
-to-
Speakers
Is my configuration correct? Please read below for specs on Amp and Speakers. Forgive my ignorance and THANK YOU !!!
Amp:
Audiopipe APA-1500
input impedance: 10k ohms, unbalanced & balanced
input sensitivity: 1.15v
output power: 8ohms/ stereo 150 watt/channel
4 ohms/stereo 200 watt/channel
4 ohms/bridged 430 watt
frequency response: 25hz-25khz +0/-1db
total harmonic distortion <0.3%
signal to noise ration: 100db
weight: 33.7 (lbs)
Settings on back of Amp:
MODE Options: Parallel, Stereo, Bridged (Stereo selected - although Parallel might be better?)
SENSITIVITY Options: 1.44v, 1.0v, 0.7v (1.0v selected)
NORMAL or COMPRESSED: (Normal selected)
GROUND Options: Lift, GND (Lift selected)
Speakers:
They are large floor-speakers like you might see at a swap meet. In the cabinets are 1-18, 2-Horns, 4-Tweeters. They are heavy loads of crap but they sound better than the 12" name-brand portables that I occasionally rent. Here’s the specs:
Zebra (brand) Pro XL Series Z-1832
Woofer: 18" with kapton voice coil
Tweeter: 4 Super Bullet 4x5 Tweeters
Horn: 2 4x10 Super Magnetic Horns
Frequency Response: 32Hz - 20.000Hz
Power: 400 Watts Peak
Impedance: 8 Ohm
Sensitivity: 101dB
Size: 35"(H) x 24"(W) x 17"(D)
Weight: approx. 78 lbs
Designed in UK
Link to amp:
Link to speaker:
Pardon Our Interruption...…-/370492091282
Impedance is actually variable and changes with frequency. The curve is not linear but it typically dips in the low frequencies. An impedance rating on a speAker is a nominal rating not an absolute rating so a 8 ohm speaker can dip to 4 ohms or lower at 40 hz which is why you need an amp can that get as close to doubling down as possible. Ideally if an amp can do 100 watts in to 8 ohms you’ll want it to do 200 watts in to 4 ohms. This wil enshure your amp won’t clip with intense bass.
Look for high current amps. Current is way more important than wattage. High current and lower wattage is much better than high wattage and low current.
Your underpowering the heck out of those speakers. I would suggest getting a bigger amp. In the meantime be careful
Absolutely you are under powering those speakers. If a speaker can handle 400w, use a 600 watt amp. You’ll typically be driving the speakers with only 200-300 watts but the bass transients will require more juice. Remember low frequency = low impedance. Low impedance = more power needed.
Speakers can handle much more CLEAN power, that they denote on the speaker typically. They can also handle big transients for small instances of time. If you can be careful and not do anything reckless you should always over power your speakers and adjust the gain structure so you don’t blow anything.
I’ve fixed a lot of speakers in my day and you blow speakers with distortion (under powering) way more than too much power.
^^^^^THIS^^^^^
Fantastic post and should be “stickied” I’ve told people this sooo many times over the years.
Edit: Doesn’t it just suck when you point to a post immediately above yours and then come to find your post becomes the first one on the next page?. 
THANK YOU all for the detailed information. I really appreciate your time and knowledge. It makes sense now why I used to get more sound by gaining up the EQ …although the high-end was piercing and hard to control. Odd to think my clipping and distortion was from underpowering the speakers. Since amp can only go up to 50% before clipping, I always thought I was overpowering.
Anyone want to recommend a new, amp & speaker combination? Needs to be priced in the mid-range, very portable, very EQ’able, deep bass and enough sound for a medium sized banquet hall or large backyard. If anyone wants to know about the photography business, I can repay the favors as that’s my real profession.
Thanks again!
Scott
As the others said you are underpowering your speakers. You usually want more power than your speakers are rated so that you have the headroom the speakers need to breathe, open up and give you their best. I would suggest calling around to some sound stores tell them what you have and ask for an amp that will pair with them. Check to see who would give you the best deal on the amp that would match what you have. You will most likely never run the amp at full volume but you will have what you need for your speakers to work right. As far as the rest of the info you listed
CPU volume all the way up
Amp most likely at least 1/2 to 3/4 of the way up and the master mix volume up until meter reads just at or below 0 (zero) depending on whether or not your mixer is digital or analog. The mixer channel volume is then raised until you get the level you need without clipping. I was reading up on mixers last year and there is a difference between how analog and digital sounds are received and sent you may want to read up on it so you can set it right. Hope this helps.
This is an awesome amp for that set-up. I’m not sure if they make another model w/out the option of an active crossover thats a little cheaper, but in any case you can’t go wrong w/ the quality and the well known durability of these amps
those speakers provide 400W Peak. peak power is basically irrelevant. the number is provided for marketing purposes only. the only meaningful figure (for output at a given impedance) is RMS.
it is true what DJ Aaron said above. distortion is the number one killer of speakers, which is why it is generally recommended to get amps that are somewhat higher rated than the speakers. but when dimensioning the amp, look at RMS power, not peak power.