Cab Output help

[yorkshireviking]

Hi There.
I have just built a bass cab, including two 15" eminence delta 400 watt 8 ohm drivers, and had it wired up in parralell.
could someone please let me know what they think the output would be on this cab. i know it will be 4ohm's but im not too sure how the wattage multiplies. would this be 800watts? might be quite a ******** question to the experienced builder but could do with knowing before i gig with the beast!

cheers
Joe

 

[playerunk]

yes..it's 800 watts.

i'm just curious as to what size box and tuning did you use.

 

[yorkshireviking]

i used the shell of an old custom sound cabinet, just replaced the drivers and wire;
its rougly 32" tall x 22" wide and 20" deep.

tuning as in what i tune to? ... A

 

[rust_preacher]

Being the skeptic that I am, I must remind you that the output is UP TO 800 W, whatever your amplifier is rated at. (It cannot be more or you would have free energy...)

Many people seem comfortable with higher wattage amps driving lower wattage cabs, assuming that the peak power output is only momentary and there is enough tolerance in the power rating of the speaker. But, you cannot get 800 W of output from a 50 W amp.

 

[yorkshireviking]

yeah, im gonna be running an ashdown mag 600 through it.
600watt RMS, 1000watt max.
should be sound.

 

[T-Bird]

Hi.

i used the shell of an old custom sound cabinet, just replaced the drivers and wire;
its rougly 32" tall x 22" wide and 20" deep.

tuning as in what i tune to? ... A

Unfortunately it seldom is that simple, just throw any old speakers into any old box.

If the enclosure is sealed, You're safe, and there isn't too much to do to tune the enclosure to the speakers for better performance. OTOH if the cab is vented/ported, there's a good chance that the cab is tuned too high, and the speakers are destroyed when the mechanical damping that the cab provides dissapears as the frequency falls below the tuning frequency.

Download WinISD, it's free, and model the speakers and the enclosure. Experimenting with different port dimensions will get You probably better results than you have now.

Regards
Sam

 

[yorkshireviking]

thanks for that Sam,
it is sealed. ill have a look at that. are you saying it might be as well keeping it sealed?
i was gonna look int porting it, but not just jump to a desision.

 

[T-Bird]

Hi.

You're welcome.

And welcome to TalkBass as well.

First I like to thank You for filling out the personal info, helps a lot when people are trying to help.
The country You're livin' in would also be of help .

I modeled the cab and the speakers in WinISD beta and in The Eminence Designer (ED from now on) and unfortunately the results weren't too promising.



A lot of assumptions in the following, so the results may not be too accurate. But they're in the ballpark.


I assumed that the driver You used is the standard 15" Delta and not one of the improved designs.

I also deducted 40mm from the dimensions to get the approximated internal volume of 180l.

With that volume, WinISD gives -3dB point of ~65Hz for closed-, and ~62Hz for vented design.
By themselves, the figures aren't all bad, but ED reveals that in a closed box, You run out of excursion with ~90W from 100Hz downwards. With a vented design, the cab will take ~200w before running out of excursion.

With ED, 4 ports of 100mm inside diameter and the lenght of 68mm gives the "best" results, at least with a quick modeling.

As You can see from the results, the cab handless considerably less power as a sealed design. Therefore I'd make the cab vented if I was faced with a similar project.
OTOH, on a vented design You won't necessarily notice reaching excursion limits as clearly as in a closed design, hence my claim that a closed design is safer when random speakers are tossed into a random box.
Views on this differ. A lot .

There's a lot of good, solid information in the stickies/FAQ as well, I suggest reading those to get more in-depth view of the wonderful world of DIY cab-making.

Regards
Sam

 

[Jaco who?]

Hi There.
I have just built a bass cab, including two 15" eminence delta 400 watt 8 ohm drivers, and had it wired up in parralell.
could someone please let me know what they think the output would be on this cab. i know it will be 4ohm's but im not too sure how the wattage multiplies. would this be 800watts? might be quite a ******** question to the experienced builder but could do with knowing before i gig with the beast!

cheers
Joe

The output power will be amp input power divided equally by the two drivers. The 400x2 watt rating means pretty much nothing.

 

[billfitzmaurice]

could someone please let me know what they think the output would be on this cab...would this be 800watts?

Cab output isn't measured in watts. It's measured in decibels, it varies with frequency, and the only way to know it is to either model the cab using software (which is part of the cab design process done prior to choosing the drivers and arriving at the cab design) or measure it.

 

[yorkshireviking]

Hi.

You're welcome.

And welcome to TalkBass as well.

First I like to thank You for filling out the personal info, helps a lot when people are trying to help.
The country You're livin' in would also be of help .

I modeled the cab and the speakers in WinISD beta and in The Eminence Designer (ED from now on) and unfortunately the results weren't too promising.



A lot of assumptions in the following, so the results may not be too accurate. But they're in the ballpark.


I assumed that the driver You used is the standard 15" Delta and not one of the improved designs.

I also deducted 40mm from the dimensions to get the approximated internal volume of 180l.

With that volume, WinISD gives -3dB point of ~65Hz for closed-, and ~62Hz for vented design.
By themselves, the figures aren't all bad, but ED reveals that in a closed box, You run out of excursion with ~90W from 100Hz downwards. With a vented design, the cab will take ~200w before running out of excursion.

With ED, 4 ports of 100mm inside diameter and the lenght of 68mm gives the "best" results, at least with a quick modeling.

As You can see from the results, the cab handless considerably less power as a sealed design. Therefore I'd make the cab vented if I was faced with a similar project.
OTOH, on a vented design You won't necessarily notice reaching excursion limits as clearly as in a closed design, hence my claim that a closed design is safer when random speakers are tossed into a random box.
Views on this differ. A lot .

There's a lot of good, solid information in the stickies/FAQ as well, I suggest reading those to get more in-depth view of the wonderful world of DIY cab-making.

Regards
Sam

I had a word with the fella who wired it all up for me, he said it would be fine either way. i think what ill do is crank it up at the next practice and see how it goes. i mean it is pretty dam loud, so therefore wont really be pushing it too hard.
ill keep you posted on how this goes. if the results arent to great ill consider venting it, and look into it in a bit further detail.
i would like to that ou again for your help, and ive ammended my Location detail!

Joe