Speaker Selection? - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 12th June 2002, 08:29 AM   #1
diyAudio Member
 
Join Date: Jun 2002
Location: Perth, Australia
Unhappy Speaker Selection?

I have recently purchased a 2 Channel Stereo Amp, which outputs 120W RMS per channel. I have decided to build myself a pair of 2 way speakers. I havent decided on any brands yet because there are a few things I am confused about.
As the Amp is 120W per channel, does this mean that the Woofer and Tweeter have to have a combined wattage of 120W(60 W ea) or does each one have to be 120W?. I will be using a 2 way crossover. And another thing, what do you reccomend the frequency response should be for the Woofer and also the Tweeter. They will most likely be in a .25 Cubic Metre Sealed Box, and will be about 6.5".
As you have proberbly realised I am new to this whole thing, I am therefore on a budget and I just want to build a pair of reasonable quality speakers. Any other suggestions are welcome.


Jeroth
  Reply With Quote
Old 12th June 2002, 09:54 AM   #2
Warp Engineer
On Holiday
 
AudioFreak's Avatar
 
Join Date: Oct 2001
Location: Queensland, Australia
In most musical situations when using a 2-way crossover even if the amp is near to clipping, assuming relatively standard power distribution and of course depending on crossover points and the type of music you listen to etc. about 40% of the output voltage from the amp will appear at the tweeter and the remainder of the voltage will appear at the woofer. This has the following effect.....

Of course, all figures below are generic and many assuptions have been mad but it should give you a general idea as to how the whole thing functions.

Now if your amp is 120W RMS into 8ohms and the speakers are also 8ohms, that is about 31Vrms output from the amp.

If 40% of that voltage (about 12.4Vrms) appears at the tweeter, the tweeter will receive about 19W and the woofer would receive about 43W. So, it can be seen that when using passive crossovers, not only does the music suffer because of the crossover but you also usually (more on this soon) lose about 50% of the output power. This allows commercial loadspeaker manufacturers to use drivers with a lower power rating. The exception to this is that if almost all of the input voltage is contained within a single passband. In this case, almost all of the amplifiers rated power can be delivered to a single driver frying it in the process.

Regards,
Daniel.
  Reply With Quote
Old 12th June 2002, 10:12 AM   #3
diyAudio Member
 
Join Date: Jun 2002
Location: Perth, Australia
Thumbs up Ok, Thanks

Thanks for your informative response!

So does what you have just said basically mean I sould get a 19W Tweeter and a 43W Woofer.I wouldnt get these exact amounts, proberbly about a 25W Tweeter and a 50W Woofer.Is this the right thing to do?

Jeroth
  Reply With Quote
Old 12th June 2002, 12:41 PM   #4
diyAudio Member
 
Join Date: Jun 2002
Location: Perth, Australia
Default Correction!!

I made a mistake in my first post by saying that the box will be .25 CU METRES but this should be .25 Cubic ft.
SORRY!!

Jeroth
  Reply With Quote
Old 12th June 2002, 12:43 PM   #5
Warp Engineer
On Holiday
 
AudioFreak's Avatar
 
Join Date: Oct 2001
Location: Queensland, Australia
Well it depends on what type of music you like to listen to... generally, i'd probably go for a about a 60W - 75W woofer just to err on the safe side because some music is very bassy and so more than 60% of the total musical power (voltage) may go on the woofer. A 25W tweeter should be adequate as not much music has more than 40% of the musical power (voltage) located in the treble but a slightly higher rating wouldnt hurt.
  Reply With Quote
Old 12th June 2002, 01:28 PM   #6
diyAudio Member
 
Join Date: Jun 2002
Location: Perth, Australia
Wink Thanks!!

That has helped me tramendously.
When you say a 60W Woofer, is that the RMS or the MAX.Would you recommend getting woofers that are 50W RMS/75W MAX or should they be 60W RMS. And also, what frequency range would u reccomend for the woofer and tweeter.
Sorry for the amount of questions but I dont want to get the wrong thing and blow them.

Jeroth
Thanks Again!
  Reply With Quote
Old 12th June 2002, 02:09 PM   #7
griff is offline griff  Australia
diyAudio Member
 
griff's Avatar
 
Join Date: Dec 2001
Location: Melbourne
The wattage isnt all that important, although it does play a part, another thing to look out for is the sensitivity. Most DIY speakers are rated between 87-92dB, though for a 120 watt amp, less sensitivity will be fine.

For a simply 2-way, we really do need to get some exact budget figures.

As for the frequency responses, it depends on the drivers, lets start with a budget and work from there.
__________________
griff
  Reply With Quote
Old 12th June 2002, 02:34 PM   #8
Warp Engineer
On Holiday
 
AudioFreak's Avatar
 
Join Date: Oct 2001
Location: Queensland, Australia
All values I quoted should ideally be RMS values. 50Wrms woofer and 25Wrms tweeter would be the minimum requirements in my opinion.

Yes as Griff says, efficiency is important and so is your budget for this project.

Please post your budget.
  Reply With Quote
Old 12th June 2002, 02:58 PM   #9
diyAudio Member
 
Join Date: Jun 2002
Location: Perth, Australia
Thumbs up Budget

My Budget would proberbly be about AUD$200 for the speakers, although i would prefer to have a bit of money left over,and then once I have those I will save for boxes, crossovers etc. Do you guys know any Online stores either within Oz or ones that offer shipment to Oz via money or cheque order, as i dont have a credit card.Thanks!

Jeroth
  Reply With Quote
Old 12th June 2002, 03:13 PM   #10
Warp Engineer
On Holiday
 
AudioFreak's Avatar
 
Join Date: Oct 2001
Location: Queensland, Australia
ok well that's about US$110 for the pair. There are a number of suppliers in australia for good drivers.... Scanspeak, Vifa, Peerless, Audax, Adire Audio and a few others are all available in the country.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
DIY: SI T Amp Boombox, FR Speaker Selection dellaseppes Full Range 35 20th February 2007 04:35 AM
seas speaker selection hero89cq Multi-Way 4 12th February 2007 07:51 AM
new on-wall speaker for selection denbo123 Multi-Way 0 3rd August 2006 02:30 PM
Speaker selection help lbreevesii Multi-Way 0 1st April 2006 03:14 PM


New To Site? Need Help?

All times are GMT. The time now is 09:51 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2