Volume of a JBL 4550

[Lee in Montreal]

I am wondering if anyone knows the volume of the JBL 4550, minus the horn obviously. ;-)

[1audiohack]

Roughly 21 cubic feet.

[Lee in Montreal]

Thanks very much. So, at 10cf per driver, that cabinet has the potential to go low with the proper port tuning and right drivers (2235 - 2234). There will be more midrange than lower bass because of the horn loading, but that's nothing that can't be equalized for hifi duty I guess.

I am asking as I have been offered a pair. Not original but nicely crafted from high quaity Russian ply and all the proper bracing.

[Lee in Montreal]

So, Barry, what driver do you think would work best for home duty? 2234 or 2235? I know you are fitting 2227 in yours, but I wish to go a bit lower than the 2227's Fs of 40Hz

[Ruediger]

Hi Lee,

I checked 2225, 2226, E130, E140, none of them matches.

Have a look at formula 70 in the Thiele paper. 1/Qt = 1/Qa + 1/Qe [Re / (Rg + Re) ]

I calculated for the 2225H what happens when You connect two of them in series.

Re is the DC resistance of the voice coil, and Rg is the amplifier's output impedance plus losses in cable and in xover. Assume Rg was zero (thick amp, thick cables, no passive xover).

If You connect two drivers in series, then each of them will see the other driver's Re as its effective Rg.

1/Qt = 1/2.5 + 1/0.31 [ 6.3 / (6.3 + 6.3)]

This gives You a new (higher) Qt, thus an entry in Thiele's table (requires some interpolation) and a new f3.

Do the calculations Yourself.

Ruediger

[Lee in Montreal]

Hi Ruedigger. I mentionned the 2234 and 2235 for better low end at the expense of all out "loudness". ;-) 10cft is indeed too much volume for a 2225, and even worst for a 2226.

[Ruediger]

... 10cft is indeed too much volume for a 2225, and even worst for a 2226...

For a stock 2225 yes, but if two are connected in series, it fits. Do the calculations and check the table.

Calculating the new Qt gives a value of 0.5 This is quite the middle between entries 7 and 8 in the table.

f3 = fs * 0.7, which is 28 Hz. Low enough?

Vb = Vas / 0.645 = 273 ltr, which is ca. 10 cu ft.

2226 has very similar params as 2225.

Ruediger

[1audiohack]

Hello Lee;

I have not spent any real time with these yet. I have four of them loaded with 2227's and two with E130's. I am listening to the ones loaded with 2227's as the shop stereo and am not delighted with the low end. Now out of fairness, they are replacing six 2242's for he bottom. Since they're not horn loaded below about 120-140Hz I too think drivers possessing either a lower corner and or less rising response will sound fuller. I have 2226's for two of them and 2220's for the other two but have yet to load them.

Hi Rudiger;

I haven't done anything but an ETC and quick EQ on these so I, as always, appreciate your input as well.


Thank you and all the best,
Barry.

[Eaulive]

So Lee, the 4520's were not big enough?

[Lee in Montreal]

The 4550 are indeed 25% bigger than 4520, I agree, but I am now only looking for another type of sound and bass articulation. It is part of a life long quest in sound...

[Lee in Montreal]

So, I have this party coming in February. The place is quite big and can host 250 people but ùI don'T expect more than 80 people on the dancefloor all at once. The occasion of that party is to celebrate a bar that was in operation in 1980-84. A friend will loan his set of empty 4550s, while I will bring my 4520 for extra bass. On top of the 4550s, I will use my 2350s with 2441 drivver and some 2405 on top. I will keep the 4520s loaded with my 2225. I was thinking using four 2226 in the 4550 for basically two reasons. The 4550 is bass reflex cabinet which suits a bass reflex driver (the 2226). That driver doesn't go as low as the 2225 and it's fine as the 4550 doesn't go as low either. The 4550 will be used mostly for midbass and lower medium. That'S where I think the 2226 shines. Crossed over around 600Hs and no higher than 800Hz.

With 10cft per driver, if the bass reflex is tuned to 40Hz, then I get a 5db bump at 40Hz that compemsates for the horns' midrange bump of around 5db from 100Hz up. I can have a relatively flat curve.

HAs anyone tried that combo? 4550 + 2226? Barry?

[1audiohack]

Hi Lee;

I've put a few of drivers through mine, E130's, 2220's, 2226's, and 2227's. The best bottom is the 2226's, no surprise I know. They are a good fit so I just got six more 2226's to double stack each side.

My best results were with a full 2kW across each pair of drivers with a 30Hz 12dB high-pass. They sound good to 800Hz, no issue.

How many4550's will you have? Two or four?

[Lee in Montreal]

I will only have two 4550. One per side. Bass reflex cabinet + 2226 should indeed be a good match. I wonder to which frequency the cabinet's bass reflex is tuned. Did you have to use spacers between the woofer and the mounting flange? Also, I was planning a 24db HP filter at 30Hz.

BTW Can you measure the size of the 4 ports on the front? That shall tell me to which frequency the ports are tuned. If they are 7 x 8, then with all 4 ports opened, that should give around 66Hz. Block two and you get 46Hz. Calculated for a volume of 20cft

[ivica]

So, I have this party coming in February. ......
.......... On top of the 4550s, I will use my 2350s with 2441 drivver and some 2405 on top...................?

Hi Lee,

Pay Your attention at 2441 (if Aluminum diaphragms in them) not to destroy AL

[1audiohack]

Hi Lee;

I am going to load four more of mine with 2226's this weekend and re-stack. I will take the VI box and take some impedance measurements.