Hello! Calling all dual 2235 sub owners

[slider908]

greetings everyone,

As a neophyte to audio, i have been a long time observer of this forum. i am new to you, but most of you do not seem foreign to me. i am very inexperienced in cabinet building as well, having almost the experience. i love jbl and have a friend with a pair of heavily modded hartsfields. i am 16 years old and still a senior in high school still, but still try to pursue my passion of audio. since age 12 i have taken notice of various audio companies (from electrostatic to horns) and have found jbl to be my favorite amongst the rest. i live in hawaii so shipping costs make the job of getting components and parts difficult
i acquired a pair of 2235s a few months ago but haven't built cabinets for them yet because i don't really know what to do with them. at the time i thought you could just slam a pair of woofers in a enclosure and expect all to go reasonbly well, with the enclosure on affecting a small part of the sound. i have learned that you are listening to mainly the enclosure and what a large role it plays in the system. this was hard for me to accept, but i am beginning to understand it a bit more. i have noticed some of you in an old thread mentioned to have had a dual 2235 setup. could you give me the dimensions and port dimensions as well. at first i was seeking 20 hz extension with the 2235s, but as time went by i realized that this contains its own set of compromises due to the large VAS and low qts. i have decided anything below 28 hz will do nicely as the room response will help compensate. this will double as a music/movie sub but mostly 2 channel stereo. i am seeking accuracy over output, but still expect good output from these reputable 2235s. i need help learning how to calculate port dimesions, box volume, and everything else involved in building speakers.
I am very anxious to get going on the 2235s this summer.
I the past, i have posted small questions in various forums but, never had the time to follow up on them. I hope to become a larger part of this forum from now on.

thank you all,

-john

[Robh3606]

Hello John

Get a copy of WiniSD. It's a free box program. You can use it to model box sizes to see what the best size and tuning is for your 2235's. 4 to 6 cu ft looks to be a good range for them. I will attach a link so you can down load the program. It is very easy to use and comes with the T/S parameters already loaded for your woofer. It will also give you port sizes and lengths. Give it a try.

http://www.linearteam.dk/default.aspx?pageid=winisd

Rob:)

[slider908]

thanks for the quick response Rob. i will download the program and give it a try. the question still remaining is should i go ported or sealed. enclosure size doesn't matter. i have the real estate to house them. i realize there must be many options on this issue and would like to hear from everone on it.
John

[GordonW]

John, given my experience with the 2235 and its parameter set, I've always had better luck with them in ported enclosures.

In fact, running the numbers... in about a 6 cubic foot ported box, tuned to 25 Hz, you get an f3 of about 32 Hz, with a relatively "shallow" rolloff down to 25 Hz. This could do quite well. If anything you might want the port frequency to be slightly lower (like say, 24 Hz), since when you cross over the subwoofer, the "shelving effect" of adding the crossover (ie, you "cut off" the midbass and midrange) makes the effective f3 lower...

Regards,
Gordon.

[tomp787]

Hello,

JBL sugests a 5 cubic foot enclosure tuned to 30 Hz in their enclosure document, though it is also tuned at 26 or 28 Hz in one of the 43xx models (4350 ?). Another virtue of the 5 cubic foot enclosure is that it has a Q of 0.5 in a sealed enclosure. A Q of .5 is a Bessel alignment and it has the best transient response with no overshoot or ringing.

So if you build the ported 5 cubic foot you can block off the ports and see if you like it better.

Tom

[Zilch]

2235 Sub = B380 (http://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm)

A tried and true design, you can't go wrong with this one. The dimensions and tuning for B380 are on the last page of this seminal 1983 sub-building article. Pairs of them are particularly delicious.

For added pleasure, find or build the BX63(A) EQ. They go between $100 and $300 on eBay, depending upon who's snoozing at the time.... :)

[Mr. Widget]

I would suggest you start by building the JBL recommended cabinets for your 2235Hs as outlined in the following document. (see #8)

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

I built four cabinets based on this info to house four 2235Hs and after much screwing around decided it was the best design for these woofers.

That said I have a few questions for you. What do you listen to and how loud do you hope to play your music?

I too was 16 once and at that point in my life I played Led Zeppelin, Black Sabbath, and The Who all at Maximum volume. These speakers can do that very well. They however will certainly crap out if you play any of the contemporary music (even something as benign as Madonna) with sub harmonic synthesizers pumping out VLF information if you want high SPL.

The 2235H is an excellent general purpose woofer. It works fairly well as a subwoofer too, but it will not do what the 2242 or Sub1500 can do. As blasphemous as it sounds they will not do what high quality true subs from some other brands either. Don't get me wrong, I regard the 2235H very highly, but it does have it's limitations in reproducing VLF at high SPLs. Without external EQ they will be fairly down in output by 30Hz. If you do use a boosting EQ curve you will need to also use a VLF cut filter to prevent running out of Xmax. This will alert you with a loud smacking of the mass ring against the top plate. As mentioned above by Zilch, you may want to look up the EQ circuit for the B380.

Widget

[PSS AUDIO]

Hello,

Why not building a 4350/55 enclosure.

It works fine and easy to build as we can provide, if it was not already done in previous posts, all measurements.

[slider908]

wow! i would like to thank all of you for all your responses. it will take me several days to chug down all this information and get back to you guys

to mr. widget, i listen to mainly classic rock, jazz, and a bit of classical so not to much of my music has high spl VLF material in it. i don' t listen to my music at very high levels either because i want to save my ears for a better system years down the road. i rarely hear a peak over 105db (c weighted on the RS meter).
i'm looking mainly for good accuracy/transience and decent extension

[Mr. Widget]

Originally posted by slider908

to mr. widget, i listen to mainly classic rock, jazz, and a bit of classical so not to much of my music has high spl VLF material in it.

You should be happy with a pair of 2235Hs then. I would definitely recommend the 5 cu ft enclosures from the JBL enclosure chart. There is some good basic construction info there as well.

I would recommend you use at least 3/4" MDF and brace the hell out of it. I like kiln dried 2X4s.

"i don' t listen to my music at very high levels either because i want to save my ears for a better system years down the road."

That shows unusual forward thinking. Good for you.:thmbsup:

Widget

[4313B]

Yep, the "5.0 cubic foot vented volume tuned to 30 Hz" is probably the best compromise for the 2235H.

"They however will certainly crap out if you play any of the contemporary music (even something as benign as Madonna) with sub harmonic synthesizers pumping out VLF information if you want high SPL."

To be fair, JBL always recommended a 30 Hz high pass filter with the large format Studio Monitors. In other words, used as intended, the 2235H's and 2245H's were quite reliable. JBL was thoroughly aware of the unloading tendencies of vented systems below resonance and made recommendations accordingly. The BX63(A) protected the 2235H/2245H from unloading in the B380/B460.

[slider908]

running the numbers on winisd, i have found 3 designs i like. they are: 5 cf @ 29 hz, 8cf @ 29hz, and 10cf @ 24hz. these are for 1 woofer only. the 8 and 10 cf have more of the extension that i'm looking for. will tuning at 24 hz create a type of EBS where i lose 3db on sensitivity? the 8 cf seems to be a compromise between the other 2. the 5 cf jbl recommends seems to have excellent group delay and phase response but it begins rolling off too early. because enclosure size doesn't matter i think i will begin considering the 8 cf. in ported systems does the Q of the system matter as it does in sealed?
When calculating box dimensions, are there any rules of thumb to follow for example eliminating standing waves? Lastly, i once heard you can add virtual volume with fiberglass, how effective is this? by what percentage could i increase an enclosures volume. would i affect response.
john

[4313B]

If you're going with an 8 cubic foot or larger volume then the 2242H or 2245H would be the preferred driver.

If you want greater extension from the 2235H in a 5 cubic foot volume then you might wish to use an assisted tuning similar to the B380 solution. You might want to look at Ian's new thread on active filters and see how that can help you. You'll need a bandpass filter with variable "bump" in the high pass section. The high pass can provide variable EQ if desired as well as protect the driver below resonance. His design offers variable slope, frequency and Q which can ultimately yield a very powerful and flexible sub solution.

[Robh3606]

Hmm Great questions! I personally would stay away from the larger volumes. You gain some extension but you give up transient response and your group delay goes out the window. Don't forget you will get some room gain. I have Le-14's that are tuned -3db @ 32Hz and I get rock solid response as low as 25Hz with the room gain.

Rob:)

[slider908]

ok, i'm going with the jbl enclosure guide 5 cf. this will be plenty for me to do for now. the assisted tuning solution has my interest and sounds like a great idea. it could be incorporated into the system after the cabinets are built. are there any kits for that circuit or could someone design the circuit for me. a circuit of that complexity seems to be way out of my league? i would need lots of help with that one.
are there any websites with guides and tips on basic cabinet building? what do you guys usually make your ports out of or is it preferred to buy them from partsexpress?

i must thank you two and this forum again for all the help i have received. this project has made more progress in the last 3 days then it has in the last 6 months.

john

[speakerdave]

In the Lansing Heritage Library you will find posted some enclosure guides from back in the days when JBL actively supported DIY speaker building.

Here's a good place to start.

http://www.lansingheritage.org/html/jbl/plans/jbl-plans.htm

Good luck!

David

[Mr. Widget]

Hi Slider,

I use 4" PVC pipe for my ports.

As for how to build a cabinet that depends a lot on what you want the final cabinet to look like and what tools you have at your disposal.

Here is a pic of one of the JBL recommended cabinets. It now houses a JBL Sub1500 but it used to house a 2235H. It is butt jointed out of plywood because aesthetics was not a concern and portability was. If they will not be moved I would highly recommend MDF as is denser and less resonant. I can not stress enough the importance of internal bracing. Put twice what you think it needs. If you read the notes on the JBL enclosure guide and try to find one of the recommended books you should be fine. Using the older JBL guides like the one posted by Speakerdave is good too, but they didn't use enough bracing back then. For tight bass you want these things to be brick sh_ _ houses.

Good luck and have fun!

Widget

[Zilch]

Ports = 4" Foam Core ABS pipe.

It's beefier, and I can pretend it's less resonant.... ;)

[4313B]

The nice thing about using dual ports and tuning the volume to 28 Hz is that if you block one of the ports you end up with a tuning frequency of 20 Hz and can then apply the 20 Hz high pass bump filter. I mention this because back then we had 5234's laying about and they had dip switches for assisted alignments which made trying them out quite easy. With the 2235H and 2245H you will still end up with a maximum electrical input power sag in the 25 Hz region but it shouldn't be so bad as to not be able to reach your 105 dB SPL.

If you need to read about assisted tunings I would recommend starting with D.B. Keele's "A New Set of Sixth-Order Vented-Box Loudspeaker System Alignments." AES (http://www.aes.org/) Journal, June 1975, Volume 23, Number 5.

Anyway... they can be fun to play around with.

[Robh3606]

I was using 3" PVC but switched to 3" mailing tubes. You can use the outside as a sleeve to change the port length and then glue in place. You can also beef up the inner sleeve with the outer for a double thickness port. I am running in a pair of 2235 right now in 5 cu. Ft. 30Hz . They are nice! Have not measured them yet will wait a while but they go low just fine considering they have zero hours on them. They do Also Sprach Zarathustra just fine.

Rob:)

[4313B]

"I am running in a pair of 2235 right now in 5 cu. Ft. 30Hz . They are nice!"

Yeah, that's what I always ended up doing as well. Fb = 28 to 30 Hz. The 34 Hz tuning of the stock 4430 is a bit too aggressive for home use. I wouldn't tune the 2235H or 2245H below 28 Hz without assist.

Incidentally, Keele's "best compromise solution" for the 2235H was 4.55 cubic feet tuned to 29 Hz. I've built that specific configuration a couple of times with "perfect" results, sounded fantastic, never smacked a mass ring or blew a driver. The only 2235H's I ever blew were those placed in volumes larger than 5.5 cubic feet (bigger than a 4343 volume) and tuned lower than 28 Hz without using assist.

I believe Keele also did the original BX63. Note that the B380 was also 4.5 cubic feet but tuned a bit lower and assisted. It's pretty much indestructible up to full rated input.