Some good deals at partsexpress right now...

[OSCAR]

4" 8 ohm shielded speaker for $.87!  The pic looks exactly like the Bob Roberts 4" shielded speaker, and should be perfect for a cabinet project.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=269-568


Their vinyl laminate is on sale right now for $11/roll, too.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-018

[sofakng]

I'm almost finished constructing my cabinet according to the Project Arcade book, but I really haven't thought about speakers yet...

Here are some spare speakers I have-- both were taken out of my 1995 Eagle Talon TSi.  The second pair (generic ones) were the factory installed speakers.

2x Polk dx Series 6 1/2" "Premium Performance Loudspeaker"
Impedance:  4 ohms    model:  dx628238

2x Generic  5"  (looks like 5" anyways)
Misc information on back of speaker:   4 ohm, 16 W, model: (?) 480K10707, 4MN1C1

Now, I know that the Polk audios ones are far superior, but are 6 1/2" too big to use?  How can I tell if they are shielded?  Will I need anything else to hook these up to my computer's sound card?  What about grills?

...or should I skip my speakers and purchase the ones you listed?  (cheapest shipping was $8 for me... I'm in PA)

Sorry for so many questions....

[wakerlet]

4" 8 ohm shielded speaker for $.87!  The pic looks exactly like the Bob Roberts 4" shielded speaker, and should be perfect for a cabinet project.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=269-568


Their vinyl laminate is on sale right now for $11/roll, too.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-018

Question:  If I have an amp that states (4 ohm load per channel minimum) can I then use 8 ohm speakers?

[OSCAR]

wakerlet - You can use 8 ohm speakers on an amp rated for 4 ohms, you just don't want to do it the other way around; say use 4 ohm speakers on an amp only rated for an 8 ohm load.

I pulled a speaker out of a TV (because it was already sheilded) that was a 16ohm driver, and I used that just fine in an arcade cabinet.  The biggest difference is that an 8 ohm speaker will be a little quieter than a 4 ohm speaker at the same output wattage, but most arcade pcb's have sufficeint amps to make that a non-issue.


sofakng - Same here... you should check to make sure the amp you are using is capable of a 4 ohm load if you want to use car speakers.  Or  you could wire a pair in series per channel for a 8 ohm load.  You can pretty much bet that car speakers are not shielded.

[Tiger-Heli]

A little more on the speakers discussion -

Eight ohm speakers with a 4-ohm amp will reduce the power by half - For example - if your amps puts out 50 watts at 4 ohms, it will put out 25 watts at 8 ohms at the same power setting.  Not a problem, but your speakers will sound like they have half as powerful an amp.  (And it would put out 100 watts at a 2-ohm load, but many amps are not 2-ohm stable - i.e. at high power settings it might overheat and destroy the amp).

Also, if you have two 4-ohm speakers per channel, you can wire them in series to create an 8-ohm load, or parallel to create a 2-ohm load.  (Or two 8-ohm speakers in parallel to create a 4-ohm load).

[OSCAR]

A little more on the speakers discussion -

Eight ohm speakers with a 4-ohm amp will reduce the power by half - For example - if your amps puts out 50 watts at 4 ohms, it will put out 25 watts at 8 ohms at the same power setting.  Not a problem, but your speakers will sound like they have half as powerful an amp.  (And it would put out 100 watts at a 2-ohm load, but many amps are not 2-ohm stable - i.e. at high power settings it might overheat and destroy the amp).

Also, if you have two 4-ohm speakers per channel, you can wire them in series to create an 8-ohm load, or parallel to create a 2-ohm load.  (Or two 8-ohm speakers in parallel to create a 4-ohm load).

Not entirely accurate, but pretty close.  The wattage-to-dB ratio is not linear, so the speakers don't really "sound like they have half as powerful an amp", although it will be a bit quieter.  Like I said, I used a 16 ohm speaker on an amp that was supposed to have an 8 ohm driver, but I only had to tweak the volume slightly to get the same sound level as I did before with an 8 ohm driver.

The bigger issue is to make sure you don't present too little load to your amp by using speakers with a lower impedance value than the amp is rated for, unless of course you put a couple speakers in series.

[Tiger-Heli]

Not entirely accurate, but pretty close.  The wattage-to-dB ratio is not linear, so the speakers don't really "sound like they have half as powerful an amp", although it will be a bit quieter.

Actually, it was accurate, but your points are valid.  I didn't say the wattage-to-dB ratio was linear.

Your 50-watt @ 4 ohm amp hooked up to an 8-ohm speaker will sound EXACTLY like a 25-watt @ 8-ohm rated amp.  The point you are making is that a 50-watt @ 8-ohm amp will not be twice as loud as a 25-watt @ 8-ohm amp.  Which is a true statement and worth noting.

[OSCAR]

Not entirely accurate, but pretty close.  The wattage-to-dB ratio is not linear, so the speakers don't really "sound like they have half as powerful an amp", although it will be a bit quieter.

Actually, it was accurate, but your points are valid.  I didn't say the wattage-to-dB ratio was linear.

Your 50-watt @ 4 ohm amp hooked up to an 8-ohm speaker will sound EXACTLY like a 25-watt @ 8-ohm rated amp.  The point you are making is that a 50-watt @ 8-ohm amp will not be twice as loud as a 25-watt @ 8-ohm amp.  Which is a true statement and worth noting.

I understand what you were saying, I just took your use of the word "sound" to mean SPL which is measured in dB.

I think perhaps a more proper way to say it is:  Your 50-watt @ 4 ohm amp hooked up to an 8-ohm speaker will act EXACTLY like a 25-watt @ 8-ohm rated amp."  Although, it has been a few years since my noise control classes, and this is really beginning to seem like nitpicking on terminology...  

[Nannuu]

Anyone have any links to an amp that will work with these?  I know nothing about speakers but for 87 cents I'll learn.  I've been using cheap computer speakers lately and they sound a little weak.  Wouldn't mind trying a 4" for fun.

[Tiger-Heli]

Not entirely accurate, but pretty close.  The wattage-to-dB ratio is not linear, so the speakers don't really "sound like they have half as powerful an amp", although it will be a bit quieter.

Actually, it was accurate, but your points are valid.  I didn't say the wattage-to-dB ratio was linear.

Your 50-watt @ 4 ohm amp hooked up to an 8-ohm speaker will sound EXACTLY like a 25-watt @ 8-ohm rated amp.  The point you are making is that a 50-watt @ 8-ohm amp will not be twice as loud as a 25-watt @ 8-ohm amp.  Which is a true statement and worth noting.

I understand what you were saying, I just took your use of the word "sound" to mean SPL which is measured in dB.

I think perhaps a more proper way to say it is:  Your 50-watt @ 4 ohm amp hooked up to an 8-ohm speaker will act EXACTLY like a 25-watt @ 8-ohm rated amp."  Although, it has been a few years since my noise control classes, and this is really beginning to seem like nitpicking on terminology...  

We're nit-picking . . .  And we both agree.

The point is "The speakers will sound like they have half as powerful an amp".  Not - "The speakers will sound half as loud".

If I remember correctly, (but it's been a looooooong time), I think it's 10 times the power for double the sound output.

So a 10-watt amp is twice as loud as a 1-watt, and a 100-watt is twice as loud as a 10-watt (at the same ohm setting).

[Tiger-Heli]

Anyone have any links to an amp that will work with these?  I know nothing about speakers but for 87 cents I'll learn.  I've been using cheap computer speakers lately and they sound a little weak.  Wouldn't mind trying a 4" for fun.

Most car amps are 4-ohms so a small car amplifier would work.  Might be tough to find one with a low enough power rating that it won't potentially blow the speakers.  I don't know how you hook the amp to the PC.  (line out to RCA adapters for the sound card, maybe) but others have done this so it can be done . . .

[sofakng]

Hmmm.. what would I need to buy if my speakers aren't shielded?

I have a spare JVC 4-channel amp that I could probably use to power the speakers,  but I would then need a power source for the amp...

On top of that, I still need a grill as well, right?