this may be a dumb question.. but..

NickfromSOS · #1 10-02-2011, 10:52 AM

I have been using a BBE Bmax preamp with a Crown xls 1000 power amp running bridged (1100 watts at 4ohms) into a Bag End S15-d and a Bag End Sx15-D. the cabs are 200/400 watts each at 8. I am not running the power amp at more than 75% volume. I'm getting a solid signal at the amp, not close to clipping it though.

I recently purchased an Ampeg PF500 (500 watts at 4 ohms) and i plugged it into the same 2 cabs. I didn't notice much of a drop off in volume between the 2 rigs. In fact, the ampeg sounded a little more solid at higher volumes.

I have 2 questions...
1.- am I in danger of blowing the bag end cabs with the crown set up? I could also use a QSC PLX 1804 (900 watts at 4 ohms stereo- I'd use only one side of the amp). Which is the better choice?

2.- why am I not getting a much more noticeable volume difference in the set ups? Am I setting up the preamp incorrectly? are the ampegs that loud?

BurningSkies · #2 10-02-2011, 10:57 AM

Quote:

Originally Posted by NickfromSOS

I have been using a BBE Bmax preamp with a Crown xls 1000 power amp running bridged (1100 watts at 4ohms) into a Bag End S15-d and a Bag End Sx15-D. the cabs are 200/400 watts each at 8. I am not running the power amp at more than 75% volume. I'm getting a solid signal at the amp, not close to clipping it though.

I recently purchased an Ampeg PF500 (500 watts at 4 ohms) and i plugged it into the same 2 cabs. I didn't notice much of a drop off in volume between the 2 rigs. In fact, the ampeg sounded a little more solid at higher volumes.

I have 2 questions...
1.- am I in danger of blowing the bag end cabs with the crown set up? I could also use a QSC PLX 1804 (900 watts at 4 ohms stereo- I'd use only one side of the amp). Which is the better choice?

2.- why am I not getting a much more noticeable volume difference in the set ups? Am I setting up the preamp incorrectly? are the ampegs that loud?

The difference in perceived volume between 500w and 1000w just isn't that much. Remember that wattage to volume isn't a direct relationship. So, I bet you have more headroom with the Crown than you do the Ampeg, and I'm guessing the Ampeg may introduce a bit of harmonic distortion that makes it sound louder than its actual wattage as well.

Rick Auricchio · #3 10-02-2011, 11:04 AM

+1

Perceived volume is also highly dependent on the voicing of the amp and cabs. The Ampeg could be voiced with a bump in just the right frequencies that it sounds louder.

As for the position of the Crown's level control, don't count on it helping you out. A power amp's level control merely sets the amount of input signal required to produce maximum output. With a strong enough input the amp can reach max power. (For example, you drop your bass or slam the strings really hard.) The level control is not a limiter.

NickfromSOS · #4 10-02-2011, 11:04 AM

Would using a 4x10 cab, or 2 2x10 cabs, make that much of a difference in volume?

Rick Auricchio · #5 10-02-2011, 11:07 AM

A 410 or pair of 210s will generally produce more volume than a 15.

Loudness requires cone displacement (movement) The 10s generally have greater cone movement than 15s.

I like the double-210 idea, because you can leave one home for small gigs. And, if you stack them vertically, you get two advantages: 1) You can hear yourself much better with the speakers that high; 2) You eliminate any phase issues caused by side-by-side speaker arrrangement. That's a compromise that all 410 cabs have.

BassmanPaul · #6 10-02-2011, 12:41 PM

Running in bridge you have 1100W. Your cabinets are rated 200W and 400W respectively. That's most likely the thermal limits of the drivers. Run in parallel for 4Ω you have a total power rating of 400W, the 200W cab defines the upper limit. With close to three times the power that the cabinets can take yes you are in danger of damaging them. Remember also that a driver will run out of excursion at about half it's thermal limit. After that the cab gets no louder and the drivers are being damaged.

Edit: The only kind of dumb question is the one that's not asked.

NickfromSOS · #7 10-02-2011, 01:26 PM

Ok then... I can run the crown power amp stereo at 210 watts a side at 8ohms and run both cabs that way. Is this a better choice for my cabs? What about "headroom". How important is having extra power vs matching the ratings of the cabs? Would the ampeg at 500 watts at 4 give better performamce than the stereo power amp (420 watts)?

NickfromSOS · #8 10-02-2011, 01:29 PM

Also- my cab ratings say "200 watts continuous sine wave, 400 watts peak musical perdormamce." im not planning on running a continuous sine wave, so what can my speakers safely handle for 3 45 minute sets a night?

billfitzmaurice · #9 10-02-2011, 01:34 PM

Quote:

Originally Posted by NickfromSOS

Also- my cab ratings say "200 watts continuous sine wave, 400 watts peak musical perdormamce." im not planning on running a continuous sine wave, so what can my speakers safely handle for 3 45 minute sets a night?

Cab ratings are as useless as the proverbial tits on a bull. If the cabs start to distort, turn it down. Simple as that. Now go spend some time reading this:
AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links

NickfromSOS · #10 10-02-2011, 01:41 PM

If can ratings are useless, why does every manufacturer use them for every single cabinet?

billfitzmaurice · #11 10-02-2011, 01:59 PM

Quote:

Originally Posted by NickfromSOS

If can ratings are useless, why does every manufacturer use them for every single cabinet?

So that there's an easy justification for charging more for one versus another.
Where the performance and output of speakers is concerned the most important factors are frequency response, sensitivity and driver displacement. The average user doesn't have a clue what any of that means, and with few exceptions the industry makes no attempt to educate them. A notable exception is Barefaced Bass; a visit to their website is well worth the time spent. If every manufacturer followed their lead questions like yours would seldom be necessary.

NickfromSOS · #12 10-02-2011, 06:14 PM

So power ratings are simply a marketing tool? Why wouldnt you just rate all your cabs at 1000 watt handling and charge more?

billfitzmaurice · #13 10-02-2011, 06:21 PM

Quote:

Originally Posted by NickfromSOS

So power ratings are simply a marketing tool? Why wouldnt you just rate all your cabs at 1000 watt handling and charge more?

Did you read either the FAQ or go to the Barefaced Bass site?
And yes, power ratings are primarily a marketing tool, as the useful information they give you is minimal.

thudfromafar · #14 10-02-2011, 06:27 PM

Nobody mentioned this yet I don't think -- but are you using a bridged speakon cable? If not, you are getting the stereo wattage, not bridged.

NickfromSOS · #15 10-03-2011, 05:51 AM

Banana clip

billfitzmaurice · #16 10-03-2011, 06:41 AM

Quote:

Originally Posted by thudfromafar

Nobody mentioned this yet I don't think -- but are you using a bridged speakon cable? If not, you are getting the stereo wattage, not bridged.

He should not bridge in any event. Bridging isn't about watts, it's about volts, and if you don't need to bridge to develop adequate voltage swing to drive a high impedance (8 ohms or higher, usually higher) load to full output you should not bridge, all it does is double the likelihood of blown drivers. 99% of the time if you have two cabs and a stereo amp you should run one cab per channel in dual mono.

esa372 · #17 10-03-2011, 10:14 AM

Quote:

Originally Posted by billfitzmaurice

Bridging isn't about watts, it's about volts, and if you don't need to bridge to develop adequate voltage swing to drive a high impedance (8 ohms or higher, usually higher) load to full output you should not bridge, all it does is double the likelihood of blown drivers. 99% of the time if you have two cabs and a stereo amp you should run one cab per channel in dual mono.

Great info, Bill. Thank you for constantly elucidating technical points for those of us without the same level of knowledge; it really is helpful.

...and, if anyone wants to read a bit more about this, I found these pages at Wikipedia:

Bridge-tied load

Bridged and paralleled amplifiers

anonymous101511 · #18 10-03-2011, 11:05 AM

Quote:

Originally Posted by NickfromSOS

I have been using a BBE Bmax preamp with a Crown xls 1000 power amp running bridged (1100 watts at 4ohms) into a Bag End S15-d and a Bag End Sx15-D. the cabs are 200/400 watts each at 8. I am not running the power amp at more than 75% volume. I'm getting a solid signal at the amp, not close to clipping it though.

I recently purchased an Ampeg PF500 (500 watts at 4 ohms) and i plugged it into the same 2 cabs. I didn't notice much of a drop off in volume between the 2 rigs. In fact, the ampeg sounded a little more solid at higher volumes.

I have 2 questions...
1.- am I in danger of blowing the bag end cabs with the crown set up? I could also use a QSC PLX 1804 (900 watts at 4 ohms stereo- I'd use only one side of the amp). Which is the better choice?

2.- why am I not getting a much more noticeable volume difference in the set ups? Am I setting up the preamp incorrectly? are the ampegs that loud?

Hi, I'm a little confused; you said that the Ampeg sounded about as loud but you also state that you didn't turn the Crown amp up much, "not close to clipping' were your words, I believe. I suggest cranking both rigs up until they start to distort, back off a bit to where you have the max. clean level and compare those two volume scenarios. I think that PLX amp would sound fantastic dual- mono; 1 cab per side so you can balance the levels, since they are different speakers.
You won't blow the speakers as long as they're not distorting for a long period of time, you'll just need to monitor that element for safe use.

anonymous101511 · #19 10-03-2011, 11:11 AM

Quote:

Originally Posted by billfitzmaurice

Did you read either the FAQ or go to the Barefaced Bass site?
And yes, power ratings are primarily a marketing tool, as the useful information they give you is minimal.

power ratings for amps are somewhat less useful than in years past, as well.
BTW, I have some old EV 15 woofers that are 'rated' for 200 watts that deliver more overall volume before distorting than my fancy new Mesa 600 watt 15's. They're both more efficient and deliver more overall volume.

billfitzmaurice · #20 10-03-2011, 11:26 AM

Quote:

Originally Posted by vail_bass

power ratings for amps are somewhat less useful than in years past, as well.
BTW, I have some old EV 15 woofers that are 'rated' for 200 watts

A case in point. EVMs started off at 200 watts, and over the years increased to 300 and then 400. Their actual output capability never changed, because that's determined by excursion, and their excursion never changed. And even the original 200 watt rating was not an accurate predictor of their output capacity, because said excursion limited all EVs to 100 watts actual working capacity in the low end.