My Mass Rings Arrived!

[Loren42]

I don't see the point in adding a mass ring when using a digital crossover.
The 2235 is just 3dB less efficient is the midrange, the LF response remains the same. For me a mass ring is just a loss of energy (aquaplass is another story, because it can help damping the cone).

Thanks!

It is the midrange on my cabinets that I have too much of. Suppressing that slightly would flatten out the response and make the lower end sound more robust. Or am I missing something?

Is there any way of determining if the cones that were installed on my drivers are genuine JBL or some 3rd-party generic replacement?

I don't remember the date or the markings that were written on the cones, but it does appear that these were replaced.

It would be good to know what the pedigree of these cones are. Since I have to replace the damaged domes, I will be able to easily confirm if the mass rings are installed.

However, the measured Fs of the driver in free air was 23 Hz and I have a lot of music time on these drivers, so they should be as loose as they are going to get. The free air Fs of 23 Hz leads me to believe there are no mass rings installed.

Oh, I am using a passive crossover and a 60 WPC tube amp to drive these, by the way.

[Loren42]

No epoxy!

Thanks for the picture. I'll look for that.

[Loren42]

[QUOTE=herki the cat;281455]

After I did a Fs sweep of my 2235Hs and found the Fs was the same as the 2234H, I decided to order 4 dust caps and 4 mass rings.Now I need to cut off the old dust caps, install these, and put the new dust caps on and the drivers should operate like they were originally Anyone ever cut off an old dust cap? I would think that I could cut them off with an Exacto-knife, but I am concerned about the affect of the magnet pulling on the blade while I work. [quote/]

Loren42 I think you are a pretty nice fellow & I hate to see you compromise those drivers with mass rings and cutting the dust cap off. I agree with Member POS on this subject. It sounds like your diaphragms already have enough mass. Any more mass will hurt the transient response & the upper frequency spectrum . Using MEK solvent to remove the dust cap can melt the foam plug in the motor pole piece vent hole, which will then drift into the voice coil gap.

Hold up for a little while. later today I can send you the CP Moyen cement & solvents data sheet if you like.

cheers herki the cat

Thanks, Herki.

[pos]

Thanks!

It is the midrange on my cabinets that I have too much of. Suppressing that slightly would flatten out the response and make the lower end sound more robust. Or am I missing something?

Is there any way of determining if the cones that were installed on my drivers are genuine JBL or some 3rd-party generic replacement?

I don't remember the date or the markings that were written on the cones, but it does appear that these were replaced.

It would be good to know what the pedigree of these cones are. Since I have to replace the damaged domes, I will be able to easily confirm if the mass rings are installed.

However, the measured Fs of the driver in free air was 23 Hz and I have a lot of music time on these drivers, so they should be as loose as they are going to get. The free air Fs of 23 Hz leads me to believe there are no mass rings installed.

Oh, I am using a passive crossover and a 60 WPC tube amp to drive these, by the way.

could you post pictures of the cone? (including back of the cone)
aftemraket kits usually come with no mass ring.

If you have 2234 kits attenuation of the midrange can be done in your filter. Do you have a digital active crossover?
If you are crossing low enought (no more than 300 or 400Hz) you can even handle the bump in the midrange as if it was a rising response of the driver by including it in your LP fitler slope. This is typically done by using two slopes with different crossovers points: one starts earlyer to attenuate the rising response, and the second one is right on the intendend crossover point. The eletrical slope of the filter starts to attenuate it before the crossover point, but taking the natural rising response of the driver into account, the final acoustical slope is what it was meant to be.
I think this is done on many contemporary JBL filters now, like in the 4344mk2.

I will try to do some simulation with winISD pro and post the result later

[pos]

Will not the mass ring also help with reduce resonances?

I don't think so. That would be the aquaplass.
The aquaplass reduce the HF response more than a mass ring because it reduce resonance caused by cone breakups. So if a driver relies on breakups modes to enhance its HF response (like the musical intrument drivers do) it will be much more attenuated by aquaplass than by a mass ring of the same mass.
The mass ring does not affect the cone behavior. I think that is the reason why Greg Timbers used both mass ring and aquaplass in the 251J to achieve a given balance between cone breakups, HF response, and LF extension.

[pos]

first picture just to illustrate what we already know, using the ability to add mass to a driver in WinISD Pro:
here is a 2235H and a 2234H with Loren42's 33.39 mass ring, in the same box and tuning. Same cruves, as it supposed to be.

[pos]

now the same 2234H vs 2235H curve as in post #12, but in WinISD Pro (which takes Le into account, resulting in a HF rolloff)

2235H in green, 2234H in white

(note: the ~0.3dB difference around 40Hz is likely to be a simulation artifact)

[pos]

now the same curves with a 24dB/oct L-R LP filter at 300Hz

[pos]

...and now with the addition of a small parametric eq on the 2234H:

fc=250Hz
Q=0.5
gain=-2.5dB

The two curves are now quite similar (the group delay cruves are also very similar, especially around the 300Hz crossover point)

If targeting a higher crossover point than 300Hz, a shelf filter should probably be used instead of a parametric eq (cannot simulate these with Win ISD Pro tho...)

[pos]

and the same result can also be obtained by using two slopes as mentioned above:

2235:
L-R 24db/oct @ 300Hz

2234:
Butterworth 6dB/oct @ 200Hz
Butterworth 18dB/oct @ 300Hz

So depending on the filter used, both parametric EQ and slopes management can be used to obtain the same result.

[pos]

And now the real interest of using a "managed" 2234H instead of a 2235H :

For the above response curve, here are the VA loads to achieve the same SPL (100W input power in the 2235H).

less power means less heat to dispate in the VC, which in turn means less power compression, which results in more dynamic!
(and the same goes on the amplifier side)



Note: these are just simulations and WinISD Pro might not be totally accurate, so your mileage may vary on the EQ and slopes parameters, but the general trend remains the same.

some complementary info by 4313B:
http://audioheritage.org/vbulletin/s...50&postcount=6

[Loren42]

could you post pictures of the cone? (including back of the cone)
aftemraket kits usually come with no mass ring.

If you have 2234 kits attenuation of the midrange can be done in your filter. Do you have a digital active crossover?
If you are crossing low enought (no more than 300 or 400Hz) you can even handle the bump in the midrange as if it was a rising response of the driver by including it in your LP fitler slope. This is typically done by using two slopes with different crossovers points: one starts earlyer to attenuate the rising response, and the second one is right on the intendend crossover point. The eletrical slope of the filter starts to attenuate it before the crossover point, but taking the natural rising response of the driver into account, the final acoustical slope is what it was meant to be.
I think this is done on many contemporary JBL filters now, like in the 4344mk2.

I will try to do some simulation with winISD pro and post the result later

Thanks. I will pull a driver and take some pictures.

The crossover is passive. See my LEAP design.

Cabinet has about 6.7 cubic feet ( a little large, but I am still adding bracing) and tuned with two 4" flared ports to 28 Hz.

Mid is the Audax PR170M0, which requires a bit more of L-pad compensation (not shown in the LEAP schematic).

[4313B]

The last time I talked with Greg about the 2235H/mass ring thing we ended up aquaplasing a pair of 2234H/2235H cones instead of using the mass rings. It worked out very well. Greg is a fan of just using the 2234H and then filling in the bottom end with EQ.

[Loren42]

The last time I talked with Greg about the 2235H/mass ring thing we ended up aquaplasing a pair of 2234H/2235H cones instead of using the mass rings. It worked out very well. Greg is a fan of just using the 2234H and then filling in the bottom end with EQ.

Talk to me about aquaplasing.

[pos]

Loren42, the easiest and best thing to do for your project would be to match the levels of the 2235 and the audax at the 400Hz crossover point, and then use some EQ to adapt the bass response to your needs (ie taste, driver caracteristics, speaker placement, and room).
The room and placement will play a huge part at these frequencies anyway, so some global EQ would be your best bet. Don't be afraid to use it!