[Ron Stewart]

At the risk of asking a silly question about port lengths, what really matters: the overall length of the port, or the length of the port inside the cabinet?

In other words, if I want to experiment with shortening my 1801F's ports, can I just leave them full length and pull them out of the cabinet (taking care to maintain a decent seal.)? Or do I really need to cut them?

Also, I know that Dave recently switched to a flared port, and has no more of the older, straight-sided ones. Does anyone still sell the old ports? My kit included one extra port, but if I end up cutting my ports too short, I'll need one more.

Thanks.

Ron

[David Ellis]

Good questions,

The volume of the port is theoretically a factor in cabinet volume calculations.  Given very big ports and very small cabinets, this theory has practical implications.  A very real place to consider the impact of port volume would be a subwoofer using one of the Peerless drivers.  These need an extensive port to obtain low bass due to their low Q.

With the 1801, the volume of the port is a non-factor.  You could easily leave the port protruding from the cabinet and obtain the same results.  This is because the volume of the 1801 port is extremely small compared to the volume of the 1801 cabinet.

At the risk of asking a silly question about port lengths, what really matters: the overall length of the port, or the length of the port inside the cabinet?

The length of the port is what matters.  Pulling the port out of the cabinet will accomplish... nothing.  You will have to cut the port for experimentation.  Yes, this is risky, but... I suppose you could super-glue the port back together to obtain the correct length.  I have never done this, but it should work just fine.

Does anyone still sell the old ports?

Unfortunately no.  I searched high & low then low & high.  The old vendor www.dynavox.com  doesn't have any more of the ports, isn't going to get any more of the ports, and won't tell me who to contact in China to obtain more of the old ports    .  This is a bit frustrating.  There are two solutions I might offer.

1.  Contact Jim Salk if you cut your port too short.  Jim said that he might have some old 1801 ports gathering dust in his basement http://www.salksound.com

2.  Purchase the new port from Madisound:



http://www.madisound.com/accessories.html

The mounting hole is bigger, so this might cause some problems.  Also the inner flare requires more space inside the cabinet.  If the inner flare doesn't fit, then don't use it.  This new port is really a slick unit.  I'd really like to do some a/b testing, but... I don't have any of the old ports, and can't get any of the old ports.  Hence, I can't accomplish any a/b testing, and... results would have no utility since the old port is no longer available.  I am certain the new port will perform equal/better than the old port, but I cannot verify the impact.

[Ron Stewart]

As always, Dave, thanks for the information.

Because the overall length of the port is the determining factor, and because I used a 1 1/2" thick rear panel, my 1801F's have an effective port length of 1 1/2" with the port tube removed completely. That's not too far off the 2-3' lengths stnvnharr and Salva have mentioned.

In my case, using the new port is not an option. My ports are very close to the bottoms of the cabinets, and the matching holes in the center braces are on the small side. I'll just make sure I keep the cutoffs in case I need go too short. I also have the extra port you included in the kit, so I should have plenty of port material on hand.

I noticed this port tube at Parts Express. It looks an awful lot like the old port you used, down to the mounting tines.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-322

Ron

[David Ellis]

You should be able to use the flared port, but possibly not the internal flange.

I noticed this port tube at Parts Express. It looks an awful lot like the old port you used, down to the mounting tines.

 

Yep, it does look the same.  Indeed I have 50 of them in my basement.  They are not the same.  The P.E. port diameter is bigger, and it's tapered.  

If you have the extra port, you should be able to experiment with no fear of "coming up short"  

[Ron Stewart]

I measured the bass response of my 1801Fs with three different port lengths: 5" (full length), 1.5" (no port), and 3". I used Stereophile Test CD1 and a Radio Shack SPL meter. It's pretty easy to see why I thought the speakers sounded forward with the 5" port.

Here is a chart showing my measurements.



My 1801Fs sound very nice with the 3" port. My 1801F web site contains the raw numbers, along with a long-winded description of my impressions of the sound with each port length.

http://home.hiwaay.net/~rgs/ellis1801f/listening.html

I'd also like to take this opportunity to extend a heartfelt thanks to Dave (and Dennis Murphy) for designing the 1801Fs, offering the kit at such a reasonable price, and providing such timely and useful customer support.

I'd also like to thank the contributors of this forum, particularly Salva and stvnharr, for posting about their experiences with these speakers. Those posts were a tremendous help.

Ron

[pecker]

I have a pair of the older style ports, if anyone needs them.
Just email me pecker@bellatlantic.net

[pem]

Did someone experimented the new version of the port?
They seem to be very long (11" I guess).

I am unable to find what is the recommended length.
I think I have read that 7" is nice (for the new version), but I do not know where I have read this.

  kind regards,
  Pem

[David Ellis]

Yes 7" is the starting length for the new port.  I'm pretty sure this is written in the cabinet plans.  Given the slightly larger diameter of the new port AND the flanged ends, this is the same theoretical length as the old port.  Well actually it's 1/4" "longer", but this isn't very audible.  

One gent responded that he really liked 6 1/2" tip to tail on the new port.  This is certainly a valid data point to consider.