feedback on cabinet design for 2235

[frank23]

hi,

I am trying to design some new cabinets for my 2235 drivers. I know the JBL enclosure guide gives measurements, but I would like non-parallel walls and I like my horn at ear height. The standard JBL recommended size does not allow that.

Measurements here are in cm., this gives a volume of about 150 liters [which is about qubic 5ft for those who do not know wat a "cheese royale" is]

Does anyone have any thoughts on this design? Positive or negative?

edit>> WOW, I now see this was POST NR 100! finally I am getting somewhere!

Regards, Frank

[Zilch]

As shown, your sides are parallel, and your top and bottom, too, no?

[frank23]

yes, but the back is not parallel with the front

I have thought about making the back normal and tapering the sides towards the back, that would be better

frank

[Ian Mackenzie]

What's wrong with the original 4430 enclosure?

[mvaldes]

What's wrong with the original 4430 enclosure?


:applaud:

[John W]

What's wrong with the original 4430 enclosure?
The 4430 has a great enclosure, basically a box of golden rectangle proportions. The function is there but I don’t think that means there couldn’t be alternate designs that might fit better for a home system. The 4425 is a great speaker, but still JBL designed the L200T3.

One goal Frank has is to get the horn up to listening height. Also, I was looking at the sales brochure for the 250Ti and it has the line “Low frequency driver is precise height from floor to give best balanced bass response”. I have not heard much about this, but what is that best height?

[Earl K]

Frank

- If you want/need a non-standard box profile, I'd suggest a trapezoidal shape.

- I feel the "trap" shape is easier to build than what you've displayed. It'll also give better overall performance in the reduction of box modes .

- FWIW ; if you drastically alter the 4430s' baffle dimensions, by going "tall and thin" / be prepared to alter some of the values for the passive components ( if you're using a passive crossover ). You'll need to "play on your own" a bit to figure ought the best compromises for the low-pass values.

:)

[Zilch]

Best I can read it, 4430 horn centerline is at 29.25", but it's somewhat academic since the constant directivity really works with flat power response on the 2344(A). Note also that the plane of time alignment is tilted 8° or 10° up from there (depending upon where you read); the standard layout was designed for listening from above the horn centerline.

I have a preference for trapezoidal enclosures: this one designed for a 15" three-way. No two sides are parallel. I also like an exposed horn on top, but keeping the 4430 horn-to-woofer center distance is going to be difficult in all but a low horn height configuration. Integrating the horn into the cabinet per the original may be a better approach....

[Earl K]

John W


Also, I was looking at the sales brochure for the 250Ti and it has the line “Low frequency driver is precise height from floor to give best balanced bass response”. I have not heard much about this, but what is that best height?

- LF & MF cancellation ( caused by a wave reflecting off of a very hard surface ) is a real and significant factor effecting the smooth playback of certain frequency areas. A "bounced wave" can quite easily propagate a new wave that is 180° out of phase to the original . Add the out of phase wave to the original and you get cancellation of various degrees .
- These cancellations aren't as narrowband as I may have implied. I've measured them to sometimes be almost a 2/3 of octave wide ( the width of the null will be effected by the diameter of the woofer under study ). The shape of the attenuation can be remarkably uniform resembling a "V" / cut into an otherwise straightline response .

- Maybe the designer found a reason to use the floor to moderate or attenuate a response bump found in the 300 hz area. Why the bump ? Maybe the answer is single driver related ( le14h-1 ) or maybe it's a function of two drivers plus the chosen crossover slopes , I really don't know the particulars.

- An example ; 1130 ( the speed of sound used by many ) divided by 300 hz = 3.767 ft ( or 45.2" ). This is the wavelength in inches . Divide that by 2 to arrive at 22.6" ( for 1/2 wave bounce-cancellation to occur centered around 300 hz )

- Look at a scaled 250ti picture / note the apparent distance from the bottom up to the center of the 14" speaker. Roughly, to my eyes, the distance appears to be about a woofer & a half / or 21" ( roughly corresponding to 325 hz ) .

- Conjecture on my part that can't go much further without building a 250ti in an anechoic environment ( & that's not going to happen ) .

:)

[Ian Mackenzie]

The stock 4430 had a lot of fibre glass in it was I recall..that may be a clue.

If you were going all out think about taking out the mass ring of the 2235 recone...and add a but of boost at the low end. One of the engineers at JBL favoured this modification..ask no further questions...

The improvements maybe a lot more worthwhile than a weird (have a not that term down pat..you Yankies?) enclsoure shape and the construction headaches.

Ian

[Zilch]

If you were going all out think about taking out the mass ring of the 2235 recone...and add a but of boost at the low end. One of the engineers at JBL favoured this modification..ask no further questions...Like 2234H? That'd be the 4435, with two of 'em.... ;)


The improvements maybe a lot more worthwhile than a weird (have a not that term down pat..you Yankies?) enclsoure shape and the construction headaches.Weird like Performance Series, Project Array, L250, K2, Project May, Everest, Pangea, and Widget Works? :p

["Yankees," actually....]

[4313B]

Like 2234H?Yep. Single 2234H and 2425H/2344A. Fill in the bottom end with EQ as desired or run a pair of 4645C's or SUB1500's. Modified 3135 network with the 18 mH and four 62 ohm resistors for the second 2234H left out. The 2234H also sounds really nice in a smaller box tuned higher if one wanted to build smaller boxes than the 4430.

[Zilch]

Yep. Single 2234H and 2425H/2344A. Fill in the bottom end with EQ as desired or run a pair of 4645C's or SUB1500's. Modified 3135 network with the 18 mH and four 62 ohm resistors for the second 2234H left out. The 2234H also sounds really nice in a smaller box tuned higher if one wanted to build smaller boxes than the 4430.COOL!

More good stuff to try here! :thmbsup:

[John W]

Along the same lines, here is a sketch I've been contemplating building.

[frank23]

What's wrong with the original 4430 enclosure?

I am not sure if anything is wrong with it. It is just that I assume JBL designed them the way they did for a reason and my environment might call for other design criteria.

One reason I can think of why JBL designed them the way they did is that them being mounted in a studio where space might be at a premium was to minimize the front area, but keeping a certain internal volume and preferable measurements, and that could be in-wall-mounted. So they would not like to have ended up with a speaker that was "high and slim" as it does not work in most studio workplaces.

But to me that does not mean to me that "high and slim" are wrong. It is just that 4430 were never designed to be floorstanders and with home speakers, that's a very handy feature and saves you [costly and possibly sound degrading] stands.

And with a non-square-baffle, JBL buyers would also have problems in-wall-mounting their 4430's. Probably the crossover would have to be retuned between a freestanding non-square-baffle speaker and an in-wall-mounted [squared out] non-square-baffle speaker.

Looking at the 4430, I'd say JBL has considered:
- unequal distances from drivers to edges
- preferable measurements
- time alignment
- easy studio mounting / positioning cabinets [could the 4430's be mounted horizontally and vertically?]

JBL obviously only cared for non parallel walls in their home speakers.

In my home, I'd like:
- floorstanding cabinets
- that come out to have the high frequency driver at ear height to catch all those high-frequencies

But... If the original 4430 cabinet cannot be beaten for sound quality, then I might have to just design a nice pair of stands and build a pair of original 4430 cabinets...

I like the trapezoidal shape though. And I have found myself a cabinet maker that has the experience to build these for me.

As always, I am open for suggestions!

>> edit >> I drew 3 cabinet options together to compare front sizes. 2 are the inside measurements, the 4430 cabinet is outside because those are the only values I could find in the brochure.

Regards, Frank

[Zilch]

In my home, I'd like:
- floorstanding cabinets
- that come out to have the high frequency driver at ear height to catch all those high-frequencies.Please look again at the 4430 spec sheet:

http://www.jblpro.com/pub/obsolete/443035.pdf

There's virually no highs lost at 10° up (Fig. 5) and that's where the time-alignment is optimum, as well, with the stock crossover and the horn mounted 1" forward of the woofer.

I'm not arguing against raising the horn, as you like, rather, merely suggesting that it's not so necessary as might be assumed from experience with other horns. Constant directivity works here; 4430 translates well as a home floor-stander....