Port number and frequency question

[wlb]

I'm rebuilding a small combo bass amp . It was originally made for a 15" speaker but only has about a two cu. ft. cabinet volume . Seems a little small for a 15" speaker . I put a new front mounting board in it for a 12" speaker and modeled it in Winisd .Everything looks good but i want to know what port frequency would be considered too high . and what would be the difference if you use two large ports or 3 or 4 smaller ports that equal the same tuning . The speaker can handle 450 watts of power but the amp is small and only puts out 65 watts so it probably won't get to the point of cuffing at the port .

[Chris Roemer]

Re: Port number and frequency question

Can you tell us what driver, or at least Qts, Fs, and Vas?

If a 4"id port needed to be 24" long to achieve your desired tuning (in a given box volume),
THEN if you used FOUR 2"id ports instead (same X-sectional area), they'd EACH have to be 24" long.

[wlb]

Re: Port number and frequency question

I'm using the PA310-8 . One 4" di. port would be 5.57" long with a port frequency of 1214 hz. or Two 3" di. 7.29" L and 928 hz. or four 2" di. 6.96" L and 971 hz . Just trying to see what will fit the best into the box .

[Chris Roemer]

Re: Port number and frequency question

I like the 4" @ 5" long.

[Brian Steele]

Re: Port number and frequency question

I'm rebuilding a small combo bass amp . It was originally made for a 15" speaker but only has about a two cu. ft. cabinet volume . Seems a little small for a 15" speaker . .

It actually looks like a pretty good match for the PA380 - http://www.parts-express.com/dayton-...oofer--295-034

[wlb]

Re: Port number and frequency question

It seems that most bass cabinets you buy have as many speakers crammed into them as possible .Most have an F3 of about 65 or 70 hz. If you are driving them with a 300 to 500 watt amp you can force a lot of low bass sound out of them . I'm only using a 65 watt amp so I'm trying to get as much bottom end as I can with a lower F3 ( a speaker/cab more efficient at a lower frequency ). A four string bass has a lowest frequency of about 40 hz. I'm not aiming to hit that 40 hz at an F3 , I know that is not really necessary but the closer I can come to it the less power I will need to use to boost the low bass when I need it , and with a small amp that will give me more power to use for a punchy sound ( 70 to 120 hz. ) That's my thinking anyway .

[Brian Steele]

Re: Port number and frequency question

The PA380 and the PA30 have the same rated efficiency, so there should be no issue wrt "punch".

I actually have experience with both drivers (I used the PA310 in my POC3 TH, and the PA380 in some repurposed PA boxes acting bass "fill").

In your situation, I'd have probably gone for the PA380, and plan a simple amp upgrade (a Behringer 3000DSP comes to mind - it's DSP would definitely come in handy) for later on.