4355 evnts plans

[frablake]

JBL has long been tight-lipped about the details of the port ducts in its cabinets. For one thing, they were not particularly interested in having the cabinets replicated while the speakers were in production. A more important reason now is that in a DIY cabinet many if the details of construction will vary from the factory version, and these variations may affect the length of duct needed to achieve the desired tuning. In other words, it is very likely your cabinets will need to be individually tuned. Still, it is desirable to know as many of the details as possible, so what is needed here is for someone owning a pair of factory cabinets to make some careful measurements and post them here just as has been done with the 4345, 4333, 4430 and others. Perhaps a forum member who has a pair can take the time.

Hi Sir
lot of thanks for your comment. It is very interesting.

[frablake]

Hi Sir
lot of thanks for your comment. It is very interesting.

Hello Sir, i find a 36.69 cms lengh for 25Hz. Do you agreee?

[speakerdave]

Hello Sir, i find a 36.69 cms lengh for 25Hz. Do you agreee?

If someone says "sir" in my presence I always get whiplash looking around to see who they're talking to.

I don't have any data on the tuning of the 4355, but that length seems way long, certainly much longer than what we know from sketches. Where did you get the 25 Hz target figure?

[speakerdave]

Here's another thread on the box:

http://www.audioheritage.org/vbullet...nclosure-Plans

[frablake]

If someone says "sir" in my presence I always get whiplash looking around to see who they're talking to.

I don't have any data on the tuning of the 4355, but that length seems way long, certainly much longer than what we know from sketches. Where did you get the 25 Hz target figure?

25 Hz is the best for two 2235H.

[speakerdave]

25 Hz is the best for two 2235H.

I don't know? I'm really not the one to be your cabinet tuning consultant, but . . . . where did this "best" tuning come from?

Is that JBL's tuning?

Isn't JBL's tuning 32 Hz? I thought you wanted to replicate the original.

How many ports does your duct length assume?

[frablake]

I don't know? I'm really not the one to be your cabinet tuning consultant, but . . . . where did this "best" tuning come from?

Is that JBL's tuning?

Isn't JBL's tuning 32 Hz? I thought you wanted to replicate the original.

How many ports does your duct length assume?

Here is the source:

Courbe de réponse, F_B et Fréquence de coupure à -3 dB :

Définition	Paramètre	Valeur	Formules de calcul
Volume bass-reflex	VB	256.0 L	Volume de calcul
Coeficient de volume	N	4.02	VB/(VAS*Qtsb2)
Optimisation de la courbe de réponse	Opt	FB est forcé à 24.9 Hz
FB pour 256.0 L	FB	24.9 Hz	Précision du calcul à 0.1 dB
Niveau à 24.9 Hz	EFB	-8.8 dB	Niveau à FB
F à -3 dB pour 256.0 L ( En champs libre, donc dehors )	F-3 dB	37 Hz	Chapitre enceinte bass-reflex Arrondi au dB le plus proche
F à -6 dB pour 256.0 L ( Niveau à -3 dB dans votre salon )	F-6 dB	29 Hz
F à -12 dB pour 256.0 L	F-12 dB	21 Hz
F à -24 dB pour 256.0 L	F-24 dB	13 Hz

Courbe de réponse en champs libre du JBL 2235H, V_B = 256.0 L, F_B = 24.9 Hz, le 0 dB correspond à 100.0 dB/2.83V/m.
Rouge : Réponse en champs libre. Bleu : Réponse avec car gain.
Vert : Correction Hi-FI embarquée ou Room gain. Pente : 0.00 dB/octave en dessous de 0 Hz.

Of course i want to replicate the original, but i have to resolve the event problem..so i use mathematic to do that..

[speakerdave]

I'm no good with French. If you want to use this approach, then try it and see if you like the result. If you do, all is well.

[Lee in Montreal]

@ frablake. I suggest using a simulation software to get your "best" tuning. "Best" is only a compromise. What good does it make to tune to 27Hz if you loose many db at, say, 35Hz, or hit max excursion at even low levels...

Lee

[4313B]

25 to 30 Hz is fine. I usually tune to around 28 Hz. The dimensions of the stock JBL ducted ports are arguably meaningless unless you use the same fiberglass fill JBL used.

[ivica]

Here's another thread on the box:

http://www.audioheritage.org/vbullet...nclosure-Plans

Unfortunately, there is NO DATA about the ducts.....:-()
Regards
Ivica

[ivica]

Here is the source: Courbe de réponse, F_B et Fréquence de coupure à -3 dB :

Définition	Paramètre	Valeur	Formules de calcul
Volume bass-reflex	VB	256.0 L	Volume de calcul
Coeficient de volume	N	4.02	VB/(VAS*Qtsb2)
Optimisation de la courbe de réponse	Opt	FB est forcé à 24.9 Hz
FB pour 256.0 L	FB	24.9 Hz	Précision du calcul à 0.1 dB
Niveau à 24.9 Hz	EFB	-8.8 dB	Niveau à FB
F à -3 dB pour 256.0 L ( En champs libre, donc dehors )	F-3 dB	37 Hz	Chapitre enceinte bass-reflex Arrondi au dB le plus proche
F à -6 dB pour 256.0 L ( Niveau à -3 dB dans votre salon )	F-6 dB	29 Hz
F à -12 dB pour 256.0 L	F-12 dB	21 Hz
F à -24 dB pour 256.0 L	F-24 dB	13 Hz

Courbe de réponse en champs libre du JBL 2235H, V_B = 256.0 L, F_B = 24.9 Hz, le 0 dB correspond à 100.0 dB/2.83V/m. Rouge : Réponse en champs libre. Bleu : Réponse avec car gain. Vert : Correction Hi-FI embarquée ou Room gain. Pente : 0.00 dB/octave en dessous de 0 Hz.

Of course i want to replicate the original, but i have to resolve the event problem..so i use mathematic to do that..

It has to be aware that in 4355 there were TWO DRIVERS, so their mutual coupling has to be considered too. That is the reason why some has used 2234 pair instead of 2235 drivers.... Unfortunately most of the programs do not "pay attention" to the drivers mutual coupling, because in such situation drivers mutual distance is important parameter over frequency ( distance = lambda/2) say 150Hz ~ 250Hz...
Nice presentation at;

http://www.zainea.com/mutualcoupling.htm

I2/I1 = 2*[1 + sin(k*d)/(k*d) ],

where k= 2*pi/Lambda,
d= drivers center distance

This is for on-axis response, but for off-axis response, the problem would be more complicated in some On JBL DD66000 such is visible too. ElectroVoice product literature: "When two speaker systems are placed side by side, the woofer cones “mutually couple,” causing the two systems to act as one system with twice the effective cone area at very-low frequencies, giving an additional 3-dB increase in maximum acoustic output. Mutual coupling will occur when the frequency is such that the center-to-center distance between the two woofer manifolds is less than about one-half wavelength." Fo = c/(d*sqrt(n)) Where "c" is the speed of sound in the air in metres per second (normally 343 is used, but can vary slightly according to air temperature and humidity). "d" is the distance in metres between the two speakers "n" is the number of sources. Fo = 344 / ( 0.5m * 1.4142 ) = 487 Hz

http://www.diyaudio.com/forums/subwo...tml#post585439

From the JBL Sound System Design Reference Manual:
".......The phenomenon of mutual coupling always comes to our aid in increasing the power output of combined subwoofer units. Figure 7-6A shows the transmission coefficient for a direct radiator as a function of cone diameter. The solid curve is for a single unit, and the dotted curve is for two units positioned very close to each other. In addition to the double power handling capability afforded by the two units, the dotted curve shows a 3 dB increase in transmission coefficient at low frequencies. This is due basically to the tendency for the two drivers to behave as a single unit with a larger cone diameter, and hence higher efficiency. Thus, at B, we see the relative response of a single woofer (solid curve) compared to two such radiators (dashed curve). Note that the upper frequency transition point for the pair is 0.7 that of the single unit. The more such units we combine, the lower the effective cut-off frequency below which mutual coupling is operant. As an example, let us pick a large cinema with the following physical parameters: V = 14,000 m3 S = 3700 m2 T60 = 1.2 seconds R = 2500 m2 We will use the JBL 2242H LF transducer. Taking into account its power rating and its dynamic compression at full power, we note that its power output in acoustic watts will be: WA = (WE x reference efficiency)10-dB/10 where WE is the transducer’s continuous power rating (watts) and -dB is the transducer’s power compression at full power. Substituting the values of WE of 800 watts, reference efficiency of .004, and power compression of 3.3 dB, we get the value of 15 acoustical watts. The reverberant level in a space with a room constant of 2500 is then: LREV = 126 + 10 log 15 - 10 log 2500 = 104 dB SPL We can now construct the following table: Number of Units Maximum Level Power Input 1 104 dB 800 W 2 110 dB 1600 W 4 116 dB 3200 W We cannot continue this process much beyond that shown here. What happens is that the frequency below which mutual coupling takes place falls below the nominal cutoff frequency of the system, and eventually all we see is a simple 3 dB increase per doubling of elements. For multiple subwoofers outdoors, it is best to assume that levels fall off according to inverse square law. I would welcome a simpler explanation. ......"

Regards Ivica

[stephane RAME]

http://www.jblproservice.com/pdf/Stu...eries/4355.pdf

Stéphane

[yvonf]

Hello

Some forumers ask for the 4355 CAD Solidworks...
You can download it at :
http://www.mediafire.com/file/6thltu...works.rar/file

Please keep in mind than all the dimensions are correct exept the event !

Sincerely

Yvon

[discus96]

Hello

Some forumers ask for the 4355 CAD Solidworks...
You can download it at :
http://www.mediafire.com/file/6thltu...works.rar/file

Please keep in mind than all the dimensions are correct exept the event !

Sincerely

Yvon

Thank you yvonf,


Great Job with Solid Works!