4430 port tuning with different drivers

[GaryCh]

First time poster, long time JBL fan.

I'm planning to build a pair of DIY 4430's. They won't be clones, but they will be similar enough for me. I found plans for the cabinets on this forum from back in 2004, so building a version of the cabinets won't be a problem. I have all the components. Unfortunately my LF drivers are not 2235's. I have a pair old Alnico 2205A's that I'll be using.

My question is about proper tuning of the cabinet with the 2205's. Do I need to change the port diameter and length to keep the frequency response the same, or at least similar? I've done a bit of research into how this is done, but it's a bit beyond me, I'm not confident I would come up with the correct measurements. If they need to change would any of you with the necessary knowledge consider crunching the numbers for me? With any luck I'll blow the dusty old 2205's up and get them reconed to 2235's... or something similar!!

So, Alnico 2205A's, 5 cubic feet, 2 ports... need any more info?

Thanks for any help.

Gary

[Mr. Widget]

Here is a simple guide that can be used as a general template for your needs.

https://www.jblpro.com/pub/manuals/enclgde.pdf


Widget

[RMC]

Hi Gary,

If you look at the Enclosure Guide document referred to by Widget, the 2205 is more suitable for 4 cu.ft. tuned at 40 hz and the 2235 is more suitable for 5 cu.ft. tuned at 30 hz.

The 4430 has 5 cu.ft. net, tuned at 34 hz and uses the 2235H. My advice is don't waste your time with a 2205 (which I own) in a box this size and tuning as your likely to be unsatisfied by woofer performance. You will have more chances of being pleased sonically with your project if you go ahead with reconing them as 2235H in that particular context.

The 2205 performs better bass wise in a box of about 4 cu.ft. tuned around 45-50 hz, and it doesn't have the requirements to go deep in the low frequencies. You would get lower output in LF than a 2235.

The 2205 is a sound reinforcement engineered driver not a hi-fi driver and your project revolving around a 4430 type is more related to hi-fi and requires a more hi-fi type woofer with deeper bass capability and improved linearity. If need be I could model it for you in speaker design software as well as port tuning.

Regards,

Richard

[GaryCh]

Thanks RMC,

I've seen the guide widget linked to and thought it was odd that it suggested 4 cu.ft. for a 2205 or 2225. The enclosures JBL offers for those speakers that I've seen are 5 cu. ft, the 4507 and EN5. After doing a bit more research the idea of HiFi vs Basic sound reinforcement you were talking about makes more sense, might as well do it right so that's the direction I'll be going.

I'll be looking for a used pair of 2235's. For some reason I'm not excited about reconing the old alnico 2205's.

In the mean time, I think I'll build the cabinets to 4430 specs and if I don't have the 2235's by the time I'm done I'll drop the 2205's in temporarily. Would lengthening or shortening the ports improve frequency response?

Thanks

[GaryCh]

Uh Oh... gold top plate (actually yellow/green), real cork gasket, low serial number.......

50/50 odds... or less... dang it!!!

Anybody have a pair of 2225/2234/2235 frames for sale??

[turnitdown]

I have twp 2234s and, separately, two mass rings. $4 dollars in dust caps and you can convert them to 2235s, though I would run them without and find out whether you want to leave them that way, or convert them. They were re-foamed with Rick Cobb examples two years ago.

From experience, if space is an issue, you can get 4430 bass from an LE14 in 4 cu.ft.

[RMC]

Hi Gary,

I made some speaker software simulations for you as wells as calculations of the related vent lengths for these. Its quite possible you'll need to shorten vent lenght, depending on LF response you want with the 2205 in a 4430 cab. I have 5 pics of the LF responses and vent dimensions simulations for you.

I'll be back tomorrow evening with all this, gotta go sleep now its well past midnight eastern time and I'm falling asleep already... "All good things come to those who wait" Regards,

Richard

[macaroonie]

I believe that if you hunt about on the www that there exists such a thing as an adjustable port.

https://willys-hifi.com/collections/...ble-large-size

parts express got a couple also.

[sguttag]

I believe that if you hunt about on the www that there exists such a thing as an adjustable port.

https://willys-hifi.com/collections/...ble-large-size

parts express got a couple also.

I've tried the adjustable ports. Some things to keep in mind, make your opening in the cabinet a little larger because you will want to use tape as you adjust the length of the port(s). It is a repetitive process as you fine tune them. Once you determine the length, again, tape is your friend to define the final length before the ABS cement is use to seal and finalize the length (you need to make a "stop line" when you push them together.

[RMC]

To Speakerdave:

Thanks for the interesting post. RE 2205 "They are a unique driver ... they have somewhat more relaxed suspension, and some people like the way they make bass." The only enclosures I've ever seen where the 2205 is specified by JBL are mostly the older 45 series rear/front loaded horns and, to a lesser extent, in vented cabs # 4508 and EN5 (1980 Catalog). Maybe their limited number of specified boxes, compared to successor 2225, is what made them sort of a "unique driver" as you say. In any case, I certainly happen to be one of those 2205 sound fan (fast & dynamic), even if not designed for VLF. I'm not sure in between which drivers it falls but your summary classification seems to make sense.

RE: "2235's don't come up for sale often" "Have them reconed with genuine 2235 kits". But on the other hand, in another thread, I remember someone mentioned in the past original recone kits for 2235 were getting more difficult to find.. Has the situation suddenly improved? Seems like a catch 22 for Gary? Ken's reproduction cones then?

To kay:

My 4430 vent dimensions were from Drew Daniels own Notes on porting, he's a reliable JBL source I think, and confirmed by Chas. JBL has custom size vents made for them by a supplier and they're not for sale as indicated on all Tech Manual sheets I've yet seen...

RE: "is there a way to calculate the correct length for 4"/102mm tubes?"
Seems I previously posted for you, in another thread, the vent length formula given by Bullock and Dickason. If need be, let me know I'll ask Winspeakerz to calculate it for you...

To Macaroonie:

Interesting actual user note about the 2235, not only the flowers but also a weakness, I appreciate that. Though I know its not meant to be this way by you with the mention of 2234, but your 2235 experience could be an indirect argument in favor of giving a try to the 2205 in Gary's box, at least temporarily.

RE: "Anyway the OP has 2205's , they will play and loud at that. They will tolerate some LF Eq and probably sound dynamic and exciting. Maybe his best plan is to run as he is". Well, that's exactly what I had in mind too.

With all due respect, I think some of my collegues have lost sight of the original issue from poster: "In the mean time, I think I'll build the cabinets to 4430 specs and if I don't have the 2235's by the time I'm done I'll drop the 2205's in temporarily. Would lengthening or shortening the ports improve frequency response?"

This is what I responded to. Gary understands the 2235 issue (posts # 3 & 4), but in the meantime he has only 2205s, therefore I try to help him make something acceptable, including different options, with what he has instead of what he doesn't, though Dave's route with 2225 frames, and Macaroonie's user comments, may end-up giving something worthwhile.

To Gary:

Don't worry about the beers, as I write this I'm already having a cold Coors light... or two in fact!

I'm not familiar with the gold color issue in early 2205. The repair shop being authorized JBL, then they should know what they're talking about, so initially I would trust them. Then the question comes down to are you willing to scrap your 2205 cones just to know? And if the answer is negative for 2235s then you have no working drivers left... I wouldn't take that risk, specially if the 2205s are nice, but rather go with Dave's suggested way of getting frames, and keep/use the 2205 in the mean time...

As shown in my simulations, you can still make your box for the future woofer and pending you getting it then use the woofers on-hand with the info modeled, therefore not wasting precious time waiting for drivers... Regards to all,

Richard

[macaroonie]

https://www.ebay.co.uk/itm/Vintage-J...QAAOSwUBZcwjKa

Somewhere in the depths of this forum there was a discussion regarding the merits or otherwise of the mass ring vs. mass loading the cone itself. This then takes you down the rabbithole of what exactly is the formulation of the Aquaplas used by subsequent JBL low frequency drivers. You can see it on the back of cones , kinda lumpy looking.
One of the other aspects of the mass ring is that it can whack the pole piece if over driven.

[Kay Pirinha]

Wrt availability of genuine C8R2235 kits: We can still buy them here in Germany, albeit at € 320 per item !

Best regards!

[RMC]

Hi Gary,

The original 4430 cabinet has two vents, each with 4 1/8" inside diameter and a total length of 8 1/4" (including say 3/4" thickness for front panel).

Note the simulations are done with the standard box loss of QL 7 and half-space loading (e.g. boxes on the floor, one boundary).

The first pic (# 486) shows the expected low-frequency response of a 2205 in 5 cu.ft. tuned at 34 hz, so a 4430 box. Note the low end is pretty rolled off with -5 db at about 45 hz. This illustrates the lower LF output I mentioned previously. Two or three boundary box placement (floor and back wall, or corner placement) may increase the lows and make the response flatter (room gain is free).

Second pic (# 487) also shows the required vents length for the above case. Note the vent length indicated by the Winspeakerz software I used to simulate these is the exact same as the JBL number for 4430...

Third pic (# 488) shows this time LF response curves with 2205 in 5 cu.ft. box tuned at 45 hz (lower curve) and at 50 hz (upper curve) on same graph. The response drop around 100 hz on both curves is typical, showing the 2205 is overstretched in that box volume (i.e. the shoes are too large for it). Typical because such curves often happen when a driver is asked to perform in a cab which in reality is too large for best performance.

So my previous mention (post # 3) that the 2205 performs better LF wise in a box tuned in the 45-50 hz range is in the ballpark, and the curves would be flatter had the enclosure volume been about 4 cu.ft. instead of 5 cu.ft., the rated 97 db sensitivity line on the graph being the reference level.

Fourth pic (# 489) gives you the vent dimensions for the above 45 hz tuned box (showing part of the LF curve behind) if you decide to go this way, and the fifth pic (# 490) are the vent dimensions for the above 50 hz tuned box (also showing behind part of the LF curve) in case you prefer that one.

Personnaly, I would tend to go with the 50 hz tuning curve because at least part of the bass range, say 50-70 hz, is at about the same level (within 1 db) as the driver's reference level. Other reasons apply to that preference, but too long to explain now.

BTW though Macaroonie's extendable/retractable vent idea seems quite appealing, in practice I tend to agree with Sguttag. I don't really trust these vents re air leaks or possible rattle noise. Never used them.

There you have it, sort of "all dressed" I guess. Regards,

Richard

[Robh3606]

You are building a system basically from scratch. If you run a 2235 in a box program take a look at 5 cubic ft tuned to 30 hz. Go from there.

Rob

[speakerdave]

If you have some clean 2205's, that is, not wrung out and preferably having lived in a domestic environment, AND they have the original cones, I agree completely with your being reluctant to recone them with 2235 kits. They are a unique driver, not just an Alnico 2225; they have a somewhat more relaxed suspension, and some people like the way they make bass. Study the data sheets in the SPECS section of the JBL library and the numbers for three drivers on a theille parameter chart: 2205,2225, 2234. I believe you will find the 2205 fits in about midway (2234 is 2235 without the mass ring).

Besides, you want ferrite frames for 2235's anyway. 2235's don't come up for sale often. The quickest route to some 2235's is probably to track down some 2225 frames, which are exactly the same as the 2235 and are very numerous. Have them reconed with genuine 2235 kits, and Bob's your Uncle.