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Author Topic: Taking out a sub port to increase depth  (Read 2535 times)

Richard_Stringer

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Taking out a sub port to increase depth
« on: February 19, 2018, 04:51:31 am »

Hi ya guys I have four Wharfedale Delta 218B dual 18" subs and i've been using them for years and like them but they struggle with very low bass so I was thinking about taking out two ports in each driver chamber and then sealing up the ports and changing the drivers with RCF L18P400 drivers instead. Would taking out two ports and then sealing up the front holes of the ports enable the bass to be deeper? Or could I just seal up two ports without taking the port out?

Here are my subs in the photo below and as you can see they have four ports per driver which are big and not very deep so regardless of what the specs say they're about -3db at 50hz.



The chambers for the drivers are actually quite small so I thought maybe if I either seal up two ports or take the wood partitions out for the ports that i'd get more low frequency depth.
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Ivan Beaver

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Re: Taking out a sub port to increase depth
« Reply #1 on: February 19, 2018, 07:30:08 am »

You MUST use your full real name on these forums before people can respond.

The short answer is "yes and no, you will get more depth".

For a better/more complete answer, change your name.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Richard_Stringer

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Re: Taking out a sub port to increase depth
« Reply #2 on: February 19, 2018, 10:33:27 am »

You MUST use your full real name on these forums before people can respond.

The short answer is "yes and no, you will get more depth".

For a better/more complete answer, change your name.

I've changed my username.
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Chris Grimshaw

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Re: Taking out a sub port to increase depth
« Reply #3 on: February 19, 2018, 11:17:38 am »

Some general rules on the subject:

- Longer port = lower tuning
- Narrower port = lower tuning
- Larger chamber volume (fixed port size) = lower tuning.

However, a narrower port will mean you're trying to shove lots of air through a small area, which means you can end up with reduced output at higher levels.

The port area there looks marginal as-is, IMO, and probably only suitable for older short-throw drivers (not much linear travel - aka Xmax). Putting some modern 18"s in there would overload those ports in short order.

If it was mine, and I had to use that cabinet and keep it a 2x18" but with updated drivers, here's what I'd do:

- Remove all existing ports
- Cut the baffles so that the largest possible triangular ports can be used
- Add triangular ports that go most of the way to the back of the cabinet, leaving a minimum of, say, 4" of space. Use a simulation program to check where the tuning will come out and plan accordingly.
- Drop in the best 18"s you can afford, and be prepared to throw some EQ around if the cabinet is, in fact, too small for a flat response out-of-the-box.

Note that the RCF driver you've mentioned have 8.8mm of Xmax, so there's going to be more output again by using even better drivers. A B&C 18SW115 has around 16mm of linear travel, so will go just under 6dB louder than the RCFs. That means you could use one box with the B&C units and have very nearly the same output as two boxes with the RCFs.

Chris
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John L Nobile

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Re: Taking out a sub port to increase depth
« Reply #4 on: February 19, 2018, 12:27:02 pm »

Would you not be in better shape by selling those cabinets and purchasing new ones that have the features that you need?

Putting speakers in a box that they're not designed for can be a crap shoot and putting better quality speakers in those boxes may put too much strain on their construction/material quality.
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Jerome Malsack

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Re: Taking out a sub port to increase depth
« Reply #5 on: February 19, 2018, 12:43:29 pm »

I do agree with John Nobile.   however if you want to continue on this try one of these books.

https://www.parts-express.com/cat/speaker-design-books/1524
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Richard_Stringer

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Re: Taking out a sub port to increase depth
« Reply #6 on: February 19, 2018, 01:03:05 pm »

Some general rules on the subject:

- Longer port = lower tuning
- Narrower port = lower tuning
- Larger chamber volume (fixed port size) = lower tuning.

However, a narrower port will mean you're trying to shove lots of air through a small area, which means you can end up with reduced output at higher levels.

The port area there looks marginal as-is, IMO, and probably only suitable for older short-throw drivers (not much linear travel - aka Xmax). Putting some modern 18"s in there would overload those ports in short order.

If it was mine, and I had to use that cabinet and keep it a 2x18" but with updated drivers, here's what I'd do:

- Remove all existing ports
- Cut the baffles so that the largest possible triangular ports can be used
- Add triangular ports that go most of the way to the back of the cabinet, leaving a minimum of, say, 4" of space. Use a simulation program to check where the tuning will come out and plan accordingly.
- Drop in the best 18"s you can afford, and be prepared to throw some EQ around if the cabinet is, in fact, too small for a flat response out-of-the-box.

Note that the RCF driver you've mentioned have 8.8mm of Xmax, so there's going to be more output again by using even better drivers. A B&C 18SW115 has around 16mm of linear travel, so will go just under 6dB louder than the RCFs. That means you could use one box with the B&C units and have very nearly the same output as two boxes with the RCFs.

Chris

There's 8 ports on each sub with 4 ports being on each driver chamber (each driver is in a seperate chamber) and the inner dimension of each the ports is 180mm x 140mm x 395mm deep. I worked out that the internal capacity of each driver chamber is aproximately 116 litres which is tiny. Would the RCF L18P300 be better instead of the P400? The L18P300 has 7.8mm xmax.


John...To be honest selling the subs and buying four more powerful subs isn't something I could afford to do because subs which are massively more powerful are way more than the money I could get together so that's why I wanted to modify these, the old saying "you do the best you can with what you have" comes to mind.
« Last Edit: February 19, 2018, 01:14:34 pm by Richard_Stringer »
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Jerome Malsack

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Re: Taking out a sub port to increase depth
« Reply #7 on: February 19, 2018, 01:24:01 pm »

Then it would be better to visit parts-express and buy the tools to help estimate you results.  You will need the specs from the two drivers.  One coming out.  and the new one going in.  along with the changes you plan to make on the cabinet.
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Richard_Stringer

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Re: Taking out a sub port to increase depth
« Reply #8 on: February 19, 2018, 01:47:25 pm »

Then it would be better to visit parts-express and buy the tools to help estimate you results.  You will need the specs from the two drivers.  One coming out.  and the new one going in.  along with the changes you plan to make on the cabinet.

That's gonna be impossible because i've emailed and phoned Wharfedale a few times in the past two years about the TS parameters of their drivers and they themselves don't even know they told me, they have no idea, there's no paperwork on any specs or anything on their drivers and i'm not qualified to measure the TS specs of the drivers myself.
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Jeff Bankston

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Re: Taking out a sub port to increase depth
« Reply #9 on: February 19, 2018, 02:00:48 pm »

Get this cabinet design CD and model the speakers to that cabinet and it will show you what you can get from them. Designing a cabinet is not as easy as it seems and takes a little time using different port types and sizes.

http://www.usspeaker.com/cabinetsoftware-1.htm
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