Easy (newbie) Watts & Speaker Question - diyAudio
Go Back   Home > Forums > General Interest > Car Audio

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 6th May 2008, 06:57 AM   #1
Lash is offline Lash  United States
diyAudio Member
 
Join Date: Apr 2008
Default Easy (newbie) Watts & Speaker Question

So I got a deal on 2 pairs of Alpine SPX177R component speakers, to be used in the front and rear of my VW Eos.
The specs say they'll take from 75 to 300 watts RMS.

The amp I'm considering is the Alpine PDX-5 which delivers 4 channels at 75 watts RMS, and a 5th at 300 watts RMS (for a subwoofer upgrade in the future).

So each of the component speaks would get 75 watts RMS.

My questions are; With 75 watts being the low end of the speakers needs, will I be disappointed with their output? Is it better to hit a speaker with something in the middle of the Min/Max level?

I await your expert opinions!
TIA!
Lash

(I'm considering the Alpine amp because of the subwoofer upgrade option and 'cuz space is limited in the Eos.
Also please don't turn this into a Soundstage/Rear Fill debate)
  Reply With Quote
Old 6th May 2008, 07:29 AM   #2
MadMutt is offline MadMutt  Australia
diyAudio Member
 
Join Date: Nov 2006
Power handling means very little.
Whats the sensitivity of the speakers ?

This will tell you how 'loud' they will sound with a given power input.

EG;
Speakers 87db/w/m driven with 1 watt of power will produce 87db.

Speakers with 90db/w/m driven with 1 watt of power will produce 90db.

See if I get this next bit right

90db is double the percieved 'loudness'.

To get the 87db speakers to produce 90db, you will need 4 times the power, so 4 watts.

EDIT, to make your 75 watt amp sound twice as loud, you would need to increase it too 300 watts.

In a nut shell, 75 should be more than enough.........
  Reply With Quote
Old 6th May 2008, 07:29 AM   #3
diyAudio Member
 
zigzagflux's Avatar
 
Join Date: Oct 2006
Location: Charlotte, NC
Default Re: Easy (newbie) Watts & Speaker Question

75W will be more than adequate for component speakers- should reach screaming levels if the rating of the amp is accurate. If the amp has built-in crossovers, which I suspect it does, high pass the components for around 80-100Hz, so they last longer than 2 years. 75W with bass pumping into them won't work, nor will it sound good. Let the subwoofer do what it does best, and don't expect it from the components.

Quote:
Originally posted by Lash
Also please don't turn this into a Soundstage/Rear Fill debate)
Okay, to each his own.
  Reply With Quote
Old 6th May 2008, 11:58 AM   #4
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Quote:
Originally posted by MadMutt
Power handling means very little.
Whats the sensitivity of the speakers ?

This will tell you how 'loud' they will sound with a given power input.

EG;
Speakers 87db/w/m driven with 1 watt of power will produce 87db.

Speakers with 90db/w/m driven with 1 watt of power will produce 90db.

See if I get this next bit right

90db is double the percieved 'loudness'.

To get the 87db speakers to produce 90db, you will need 4 times the power, so 4 watts.


EDIT, to make your 75 watt amp sound twice as loud, you would need to increase it too 300 watts.

In a nut shell, 75 should be more than enough.........

Hi,

97dB is double the percieved loudness relative to 87dB.
In other words 1 Bel = a doubling of percieved level.

+3dB in level requires double the power, not 4 times.

A 750W amplifier is twice as loud as a 75W amplifier.
A 75W amplifier is twice as loud as a 7.5W amplifier.

Quote:
The specs say they'll take from 75 to 300 watts RMS.
No they don't. 75W RMS, 300W peak.

http://www.abt.com/images/products/P...77r_manual.pdf

87dB/2.83V/1m comes out as 84dB/W/1m.
Xmax for the woofer is 3.5 mm and its power handling is 40W RMS.
So 75W to 100W is probably as high as you can go.
As allways speakers can take very high unclipped peaks so very high
power can be used with care, the downside being any carelessness
can cause damage / expiration of the drivers.


/sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
  Reply With Quote
Old 6th May 2008, 03:20 PM   #5
Lash is offline Lash  United States
diyAudio Member
 
Join Date: Apr 2008
Thanks guys, now to figure out where to squeeze in a subwoofer.
~Lash
  Reply With Quote
Old 6th May 2008, 11:23 PM   #6
jol50 is offline jol50  United States
diyAudio Member
 
Join Date: Nov 2007
75wrms is usually pretty loud. I know people have been running shallow subs in the side panels in back near the arm rest in other convertible cars. You may be able to run IB into the back seat like I do. I see they don't leave much room in the trunk with the top down.
  Reply With Quote
Old 7th May 2008, 03:57 AM   #7
Lash is offline Lash  United States
diyAudio Member
 
Join Date: Apr 2008
Quote:
You may be able to run IB into the back seat like I do. I see they don't leave much room in the trunk with the top down.
MadMutt I'm not hip to your lingo, is IB isobaric?
Got any photos?
Thanks for your reply.
  Reply With Quote
Old 7th May 2008, 04:27 AM   #8
jol50 is offline jol50  United States
diyAudio Member
 
Join Date: Nov 2007
Infinite Baffle or free air. You mount them in the rear deck, or you build a baffle sealed to the rear seat back opening and put them in that. Mine blows through the seat no problem, but all I left was the seat and took out the panel in the trunk. I sealed off my rear deck, works well and actually overpowers the 4 door speakers badly on a 5ch 700w amp. I have 4 12s in it. Just seal trunk off from car with some deadening or whatever as best you can, and if you make a baffle you have to mount it sturdy. I figure I need double the drivers for IB but went a little overboard on this one now I have to get my comps working better. Going to swap amps and want to try 2 15s instead, lighter ones, because the subs I have are rather heavy and put out plenty anyway. This way you have no box. For the room my 4 12s take I figure I could make a box for a single 10. With 15s I will have more amp room also, and still my trunk is near empty.
  Reply With Quote
Old 7th May 2008, 09:30 AM   #9
MadMutt is offline MadMutt  Australia
diyAudio Member
 
Join Date: Nov 2006
Quote:
Originally posted by Lash


MadMutt I'm not hip to your lingo, is IB isobaric?
Got any photos?
Thanks for your reply.
Wasn't me. But for me IB could mean infinite baffle, or isobaric.
  Reply With Quote
Old 7th May 2008, 02:57 PM   #10
jol50 is offline jol50  United States
diyAudio Member
 
Join Date: Nov 2007
Isobaric is much different and involves a box, though I suppose you could mount one IB but I can't see how it could ever work. The key to IB is more cone area and isobaric is half the cone area. Isobaric is mounting two drivers in tandem, cone to cone, that work together. So basically you have one cone and two voice coils (twice the motor on a sub in essence). IIRC you can use half the box for same tuning, but it takes twice the power to run. So it is mostly for when you must have a tiny box. I hate small boxes and low efficiency so I've never built one.

IB is all about moving air and no box at all (trunk room!), the world behind the driver is its infinitely large box. It must be at least say double what a sealed would be but should be more or open. You can use aperiodic, that is just limiting the air movement behind the sub. Say you put a sheet of batting on a frame and mount it behind the sub, it will tend to slow the air and limit higher excursion. That will kill off some low bass. Over excursion is always the limit in IB as you have no box air to support the cone. However IB tends to roll off on the bottom anyway, so aperiodic is often not that useful for SQ. You can do the same thing by venting a sealed box with a filter of some kind, it lets some air out and loosens the driver up allowing a little more low bass.
  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
Newbie question about an MP3 speaker amp Ute Chip Amps 1 5th September 2008 07:09 AM
Speaker Newbie Question TubeHead Johnny Multi-Way 28 22nd November 2007 07:21 AM
Newbie with a question about speaker sensitivity Dylan Multi-Way 5 10th September 2004 04:59 AM
newbie question about speaker wires moonshow Chip Amps 1 11th July 2004 04:32 PM
Newbie Question, upgrade PC speaker's amp. Mikka Solid State 1 4th January 2003 02:23 PM


New To Site? Need Help?

All times are GMT. The time now is 04:10 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