2245 port sizes

[dennis j leisz]

I'm starting a new winter speaker project. It gets cold here in Minnesota. I am designing an 8 cu. ft. enclosure for a 2245 . I can't get any of the design programs to correlate on port size lenght etc. I need some suggestions. I plan to cross over at 300 hz to a 10in. I would like to tune the cabinet to 28hz and use (3 )., four inch I.D ports. What do your programs tell you the length of each port to be. I use this info as a starting point and use a test tone with a scope to fine tune the lenght. Any other suggestions would be great. I looked at the Solen site for help on the Ultimate experience. I have never used the 2245 before , looks like fun.

[4313B]

Well, the old JBL method of tuning comes up with 11.125" as the required duct length.

Bass Box 6 Pro comes up with 10.96" as the required duct length with "normal fill", 11.58" with minimal fill and 12.26" with "no fill".

And yes, the 2245H is fun

[boputnam]

Hey...

Here's a 4345 monitor plans - Link the first page of which shows, and gives the port dimensions for the 4345 cabinet as 4-1/8" diam by 8-1/4" duct (x 3).

Fun, fun, fun...

[4313B]

Well, if you are going with stock stuff then you might also want to know that the B460 used three 4.125" ID ports each having a 14.875" duct.

I think you're right on though going for a 28 Hz target tuning frequency. The 4345 might be a bit too high (plus you don't have a big 5.4 mH inductor in your signal path do you?) and the B460 might be a bit too low unassisted.

Use the port length I suggested and prepare to cut some length off as you measure the actual tuning frequency

BTW - What lengths are your programs giving you?

[Guido]

Originally posted by Giskard

BTW - What lengths are your programs giving you? [/B]

My Program state 10 qubic foot with three 4 inch ID Ports each 8,11 inch duct as ideal for the 2245H.

Tuning frequency is 28 HZ.
- 3 dB at 36 Hz

[4313B]

For ten cubic feet tuned to 28 Hz I get three 4" ID ports with 7.71" ducts from BB6P with "normal" fill, 8.21" ducts with "minimal" fill, and 8.75" with no fill. The JBL formula says three 4" ID with 7.875" ducts

Now do you see why I advocate just tuning by the proper methods

[dennis j leisz]

Thankyou for your input and suggestions. What I am basicaly doing is designing and building an updated 4345 system. This new speaker will sit in my new dedicated sound room. No wife acceptance factor in this space! I am using the 2245 , a 2123h crossed over at 300hz, a 2450h on the 2380a for the mids and a 2405 for the high frequencies. I am designing a 2nd order Linkwitz-Riley crossover. I have a pair of 077 s sitting in my shop that I may use instead of the 2405s. Any opinions? One other question. 9.2 cu.ft cabinet gross volume with 3- 4 1/8 " dia X 8 1/4 long ports= 28hz. Will 2 ports work and if so what dia. and lenght. As soon as I'm a bit further along I'll post some progress photos. I will drive these speakers with the McIntosh MC1201 monoblocks.

[4313B]

Originally posted by dennis j leisz
Will 2 ports work and if so what dia. and lenght.

I use dual 6" ID ports for 2242 and 2245 subs but you can use dual 5.25" ID ports with 10" ducts in your 9.2 cubic foot volume.

[Mr. Widget]

"I have a pair of 077 s sitting in my shop that I may use instead of the 2405s. Any opinions?"

They are identical, don't worry about the 8 ohm, 16 ohm thing. All 077s and 2405s use the same diaphragm. You can find several posts on this subject here on the forum. I use the 077 clear acrylic horn plugs in my 2405Hs because they look cooler.

[John Y.]

Originally posted by Giskard
I use dual 6" ID ports for 2242 and 2245 subs but you can use dual 5.25" ID ports with 10" ducts in your 9.2 cubic foot volume.

Giskard,

Why do you suppose JBL went to one (rather large) port on their latest pro subwoofs, the 4645C and 4641?

These enclosures are the 4518A, I believe. Do you suppose the enclosures are identical for the two systems mentioned above (same tuning)? Do you further suppose a 2245 sub would go in nicely, without mods, into this enclosure?

John Y.

[4313B]

Originally posted by John Y.
Giskard,

Why do you suppose JBL went to one (rather large) port on their latest pro subwoofs, the 4645C and 4641?

These enclosures are the 4518A, I believe. Do you suppose the enclosures are identical for the two systems mentioned above (same tuning)? Do you further suppose a 2245 sub would go in nicely, without mods, into this enclosure?

John Y.

I suppose because one single port is cheaper and easier and they have the baffle room to use it.

They are tuned the same. Fb is 25 Hz. The original 4518A was tuned to 30 Hz for the 2245H. If you put a 2245H into the 4645C enclosure it will perform roughly the same as a B460 without the BX63 boost. The original S1S used the 2245H and was tuned to 30 Hz as well. JBL has since moved to the 2242H and will be retuning the S1S to 25 Hz if they haven't already done so.

[Ian Mackenzie]

Inspifred by Dennis Leisz original question I thought it would be fun to revisit this old thread being a 2245H and 4345 fan.

Having built a clone of the JBL 4345 I calculated the internal Vb from the following data with the assistance of JBL (courtesy Greg Timbers)

Vol from cabinet internal dimensions = 10.1 cuft 3
Subtract
Vol of Dog Box = 0.71 cuft 3
Vol of Horn and driver = 0.1 cuft 3
Vol of Ports = 0.2 cuft 3

Gross internal volume = 8.99 cuft 3

Subtract

Vol of woofer =.0.3 cuft 3
Vol of cleats = 0.4 cuft3

Add effect of 3/4 inch fibreglass fill = Vol of woofer and cleats
(courtesy of Greg Timbers)

Net VB is 9.00 cuft3

Port dimensions 4 1/8 diameter x 8 1/4 inches long (3) ports

Tuning FB = 29.7 hertz (Bass Box simulation-normal fill QL 7)

The impedance curve suggests a Fb of 26 hertz but in practise the Fb in terms of real movement closer to 28.0 hertz from my observations.

In the original design the tuning was somewhat empirically done, based on the results of listening tests. One can change the tuning frequency of that system by +/- 2 Hz and still get a very presentable low frequency curve. It really came down to the preferred sound character.


Ian

[Ian Mackenzie]

The sound character of the bass is different in bi amp mode and I will do some experimenting with small variations in Fb and advise the results.

Ian

[Lancer]

The sound character of the bass is different in bi amp mode and I will do some experimenting with small variations in Fb and advise the results.

Once again, reference Keele's paper - Sensitivity of Thiele's Vented Loudspeaker Enclosure Alignments to Parameter Variations.

It's going to be tough for you to advise the results as they are somewhat subjective. Sure, you will affect power handling and can advise on that objectively but with a driver that robust it shouldn't really matter for home use. Some people think a 26 Hz tuning doesn't have enough "fill", other's think it's fine. Some prefer it tuned a bit higher. Any room/boundary reinforcement will have an effect.

You can play around with QL too, the stock 4345 should be somewhere around 10 as opposed to the "typical" 7.

In the original design the tuning was somewhat empirically done, based on the results of listening tests. One can change the tuning frequency of that system by +/- 2 Hz and still get a very presentable low frequency curve. It really came down to the preferred sound character.

[Ian Mackenzie]

Hey your up early!

I agree but I was planning only a +-1 hertz variation just to see what gives.

Once again, reference Keele's paper - Sensitivity of Thiele's Vented Loudspeaker Enclosure Alignments to Parameter Variations.

That is a great read, I recall measuring about 10-11 QL, the problem is the 2245 is like a big mic and a devil to measure.

I figure the system was either tuned for bi amp as best result or tweaked for good result in passive/active with that 0.5 ohm coil and 90 uf capacitor.

Odd they did not make it 10 cuft 3 and be done with it. The previous iteration I had was around 10.5 cuft tuned to 27.2 hz with Keele's equations

Vb= 15Vas ( Qts) 2.87

I suppose of I was serious I would buy a woofer tester and start with clean data.

Ian