Jump to content


Speaker rating bi-amped


  • Please log in to reply
8 replies to this topic

#1 debzdoodle

debzdoodle

    Power User

  • Members
  • PipPipPipPipPip
  • 46 posts

Posted 11 September 2012 - 08:05 PM

This is more of a speaker question I suppose but I am intrigued by this. I have 2 SRX715's powered by 1 XLS2000 bridged per side. The speakers are rated at 800w each. However, if I bi-amp them  using a small amp for the horns, the rating on the mid is still 800w and the horn is 75w. Does this mean that the speaker when bi-amped is rated at a total of 875w??????

Thank you in advance.........

#2 dakos

dakos

    Admin

  • Members
  • PipPipPipPipPip
  • 742 posts

Posted 12 September 2012 - 12:10 AM

No, of course not... It took me a while to understand this as well and I'm still not sure I got to the bottom of it. This is not a simple parallel connection... Because the speaker has an internal crossover, it routes the amplified music signal to the correct driver, the amp doesn't "see" the actual drivers, the amp only "sees" the crossovers representation of the drivers. The crossover sums the total of frequencies to a complete full range of the box. The speaker companies relay on the typical frequency composition music is made of and that's the signal they use to rate the power of speakers. This might make more sense to you if only theoretically you filter out the LF content, say 1000hz and below, and then push it up to 800W that the speaker is rated to, now connect it to the full range speaker, I guarantee you will fry that HF driver in a second. The same goes if the crossover is external (active), the only power boost you get is overcoming the -3dB the crossover robs from us. You also get other benefits such as better system control but that's out of our scope

You need think of any system you build as how much SPL you need for the whole frequency range, since the HF driver is much more sensitive, you don't need as much power to get the same SPL as the LF section of the speaker.

#3 debzdoodle

debzdoodle

    Power User

  • Members
  • PipPipPipPipPip
  • 46 posts

Posted 12 September 2012 - 01:30 PM

Thanks Dakos...... As always....you teach...I learn. Ok so my use of the term 'wattage rating' shouldn't really be used here as the 800w does not change  - whether passive or b i-amped. The important thing is SPL which is increased by 3db. That is quite a lot right?? So if I switched to passive and ran the same amp I am using for mids into the full range cabs at the same volume (gain), I would notice a slight increase in volume...correct? This makes them more efficient in bi-amp mode...Bottom line.....always better to bi-amp. As you say extra 3db, and that extra control over the system . Dakos, one more question....again something I am interested to know...... what is the difference between adjusting the main EQ through the PA  -  and adjusting the gains on the horns, mids and subs??? Does it in fact do the same thing?

#4 debzdoodle

debzdoodle

    Power User

  • Members
  • PipPipPipPipPip
  • 46 posts

Posted 12 September 2012 - 02:45 PM

One more thing...sorry......

Regarding your comments about more power needed for LF than HF, in simple terms, what is the ratio or percentage difference generally between LF and HF power needed to get a balanced system - just an approximation of course ....?????

#5 dakos

dakos

    Admin

  • Members
  • PipPipPipPipPip
  • 742 posts

Posted 13 September 2012 - 06:14 AM

View Postdebzdoodle, on 12 September 2012 - 01:30 PM, said:

Thanks Dakos...... As always....you teach...I learn. Ok so my use of the term 'wattage rating' shouldn't really be used here as the 800w does not change  - whether passive or b i-amped. The important thing is SPL which is increased by 3db. That is quite a lot right??
That is allot but that's true only if you don't have enough power. Say you have an 800W driver and a crossover that robs 3dB, so if you feed the crossover 1600W then the driver will already get the maximum power it can handle, so if you get a gazzilion watts amp, it will not change a single bit.

View Postdebzdoodle, on 12 September 2012 - 01:30 PM, said:

So if I switched to passive and ran the same amp I am using for mids into the full range cabs at the same volume (gain), I would notice a slight increase in volume...correct? This makes them more efficient in bi-amp mode...Bottom line.....always better to bi-amp.
There is never such a thing as always... You would still need to know how to configure the bi amp system to get better sound quality then the passive crossover would give you, that's not always a simplest of tasks!!!

View Postdebzdoodle, on 12 September 2012 - 01:30 PM, said:

As you say extra 3db, and that extra control over the system . Dakos, one more question....again something I am interested to know...... what is the difference between adjusting the main EQ through the PA  -  and adjusting the gains on the horns, mids and subs??? Does it in fact do the same thing?
No, it doesn't do the same thing, first of all, EQ's can ruin the sound quality just as easely as the can upgrade it, an EQ sould be used to cut specific, trouble causing frequencies, for example due to a screaming lead vocal, a boost in a curtain frequency that needs to be taken care of, an occasional feedback. More exactly it's used to cut and not to boost anything. Second, an EQ has a very nerrow responce curve so if you take all the knobs down, even on a 1/3 octabe EQ, you will still get a saw tooth responce curve rather then an equal flat, only taken down a few dB's down responce curve/

View Postdebzdoodle, on 12 September 2012 - 01:30 PM, said:

Regarding your comments about more power needed for LF than HF, in simple terms, what is the ratio or percentage difference generally between LF and HF power needed to get a balanced system - just an approximation of course ....?????
Answering this one is compleatly theoretic and is only basic rule of thumb, it can vary allot so take that into consideration. The subs get 50-80%, the mids 20-40% and the HF drivers about 10%. That's very unsubstatiated and changes from gig to gig.

#6 debzdoodle

debzdoodle

    Power User

  • Members
  • PipPipPipPipPip
  • 46 posts

Posted 13 September 2012 - 08:15 AM

Thank you, thank you , thank you and thank you.

I use the DRPA.  At first , I was a bit intimidated by it but now I love it. My SRX speaker tunings are built in and the amps I had set up manually. SRX715 bi-amped tops with bridged Crown XTI 4002 mids and Carvin HT760 horns AND SRX718 subs with a XLS2000 bridged per side. I used gain structure to get all my meters where I want them. When you to take the time to answer my questions Dakos, I learn a little more that I knew before. I love the science behind sound.......it fascinates me. There are very differing opinions expressed by some knowledgeable (and not so knowledeable) people on different forums so I am always aware that personal opinion can muddy the facts and I need to discern what I take from what I read, I find your explanations well written, clear, easy to understand and I appreciate that.

I just thought of one more thing regarding the subs. I originally purchased MRX518's early this year which sounded great with the srx715's. However, I got tempted by the low price on the discontinued SRX718 and bought 2. I played them side by side and I like the SRX's more.. IMy plan was to sell the MRX's. I never even used them live - they never left the house. It took me a while to build the system and the band broke up just as I started to piece things together. However, I have had many inquiries for the MRX's but all have been no shows. Now I am wondering if I can use them rather than have them sit around. Of course I would need another amp but would a mrx518 and srx718 per side make things better or worse??? I have heard that coupling different speakers isn't always a good thing. I thought I could use one set of subs through aux for extra sub boost when necessary - so in effect outside of the 3 way system. Good or bad??

#7 dakos

dakos

    Admin

  • Members
  • PipPipPipPipPip
  • 742 posts

Posted 13 September 2012 - 09:33 AM

Bad, but like I said, not always... You need very expensive gear to do that properly otherwise it's 99% you will get a terrible comb filter effect due to the difference in the frequency response of the subs. But... Since you already have the gear so why not give it a try? You just might be that lucky one percent :)

Thank you for the kind words :)

#8 debzdoodle

debzdoodle

    Power User

  • Members
  • PipPipPipPipPip
  • 46 posts

Posted 13 September 2012 - 10:53 AM

You are welcome!

Thank you again....... I'll give the MRX's a try along with the SRX's  !!

#9 debzdoodle

debzdoodle

    Power User

  • Members
  • PipPipPipPipPip
  • 46 posts

Posted 13 September 2012 - 12:56 PM

OK...... I have what I need I think to use both sets of subs next gig. Do I have this right???

Set up PA as usual, three way except I'll steal one of the Crown XLS2000's from the set-up. SRX718's + SRX715's bi-amped.
I'll use one of my XLS2000's to power the SRX718's  in bridge mode and the other to power the MRX's in stereo (well, 2 channels)
As I do not want to purchase another amp yet in case the subs clash, I'll just use what I have for now, I can get an amp later. It is a small place so I can keepthe levels low.
Then, I take an output from the aux at the desk into the XLS2000 and l'll activate low pass on the amp to around 80hz ish and also 'Y' feature.......Am I right??? I'm keeping the subs separately fed so the MRX's don't get the same frequencies from the DRPA as the SRX's do.