Speaker recommendations for stopping bass excursion?

[Fuzzstone]

This is pretty simple really, and hopefully this thread will be fruitful for me and serve as warning to others. 

I recently installed a depth mod to my JCA20H amp and experienced massive speaker excursion at volume 1.5 with it dimed up through my Jenson mod 12-35 speaker... I love this speaker, but it's pretty clear I'm gonna have to be very careful with it with the depth mod. It handled itself just fine before.

Does anyone have any ideas on how to either stop over-excursion with lots of bass? If not, are there any low sensitivity speakers which can handle this?

[DeepEnd]

Have you considered just turning down the bass? The JCA20H is a head, you haven't mentioned the cab. What cab are you using? A closed back cab would probably help as well. Is it possible to screw a sheet of plywood to the back of your cab?

[mrbrown49]

It maybe sounds like you should undo the depth mod.

[jtr654]

Is this for Bass Or Guitar? If guitar dose it happen with all your guitars ? I have a X2N that caused  over  excursion in my combo amps. Air sealed cab might do the trick. Or as Mr. Brown said  undo the depth mod.

[Grant Harding]

I'd reverse the mod or get a suitable new cab.

[Fuzzstone]

I should have mentioned that the cab is open backed, I'm currently considering rebuilding it as closed back or ported and tuning it fairly low, though I'm still working all that out.

As for uninstalling the mod.. that would kinda be silly, you can just turn the depth pot down (the preamp eq seems to have little effect on excursion however).

And yes, this is for guitar. Specically a Yamaha 112v with pretty low output singles, though I do tune down to drop B at lowest.

[mrbrown49]

So basically you are saying,

"There is too much bass when I turn the bass up too high.  Help me pick a speaker with less bass so I can turn the bass up higher."

Doesn't make a whole lot of sense dude.

[DeepEnd]

5 hours ago, Fuzzstone said:

I should have mentioned that the cab is open backed, I'm currently considering rebuilding it as closed back or ported and tuning it fairly low, though I'm still working all that out.

As for uninstalling the mod.. that would kinda be silly, you can just turn the depth pot down (the preamp eq seems to have little effect on excursion however).

And yes, this is for guitar. Specically a Yamaha 112v with pretty low output singles, though I do tune down to drop B at lowest.

If the preamp EQ has no effect there's something else wrong. Drop B produces a lot of low frequency energy and your Jensen Mod isn't a great speaker.

3 hours ago, mrbrown49 said:

So basically you are saying,

"There is too much bass when I turn the bass up too high.  Help me pick a speaker with less bass so I can turn the bass up higher."

Doesn't make a whole lot of sense dude.

FWIW, I thought the same thing.

[Fuzzstone]

No guys, if having a bassy tone (whether via speaker or amp) was the only way to avoid over-excursion then bass speakers would surely not be able to function. So there should be no reason that getting more bass should mean killing any speaker I play through.

My aim is to increase the amount of bass I'm able to dial in, that could either be by rebuilding my cab with the same speaker as closed or sealed, or finding one with a greater ability to handle low end. If I wanted the same bass response but to be able to crank the knob, I'd switch out to a lower resistance pot.

For instance, it may have a greater xlim, allowing it to have more excursion before killing itself and henceforth more potential bass response.

DeepEnd: The bass knob has "little" effect. I would imagine because it only effects frequencies so low.

My speaker has no problems with drop B without the mod, even maxed out. My guess would be that it can handle fairly low frequencies, just not much volume somewhere around 70hz or lower. 

Do you have any ideas of what that something else could be? 

[DeepEnd]

56 minutes ago, Fuzzstone said:

. . . DeepEnd: The bass knob has "little" effect. I would imagine because it only effects frequencies so low.

My speaker has no problems with drop B without the mod, even maxed out. My guess would be that it can handle fairly low frequencies, just not much volume somewhere around 70hz or lower. 

Do you have any ideas of what that something else could be? 

It sounds like something is producing infrasonics, causing the extreme excursions. No idea what. A subsonic filter might work. As for bass speakers, they're designed to handle the low frequencies and longer excursions involved. I'll reemphasize converting your cab to a closed back.

[Fuzzstone]

1 hour ago, DeepEnd said:

It sounds like something is producing infrasonics, causing the extreme excursions. No idea what. A subsonic filter might work. As for bass speakers, they're designed to handle the low frequencies and longer excursions involved. I'll reemphasize converting your cab to a closed back.

Thanks for the advice on there, particularly on filtering. Yeah the plan is to redesign my cab, though I'll miss the room filling sound for sure. 

Though I still believe there's a happy medium out there between a guitar and bass speaker, in fact if I remember correctly some of the mod series are even partially described for bass. Though there may not be too much reason for that.

[jtr654]

Some speakers work better in air tight cabs. Bose dose this so the speakers don't blow from over excursion

[leadfootdriver]

That speaker has a tiny 10 ounce magnet that just can''t control bass like a larger one can.. Celestion type magnets are typically 35 and 50 ounces.

Furthermore, the Depth Mod passes bass past the feedback loop, thereby allowing it to be less controlled. 

But you should be fine getting a speaker with a bigger magnet in a closed back cab.

 

[Fuzzstone]

57 minutes ago, leadfootdriver said:

That speaker has a tiny 10 ounce magnet that just can''t control bass like a larger one can.. Celestion type magnets are typically 35 and 50 ounces.

Furthermore, the Depth Mod passes bass past the feedback loop, thereby allowing it to be less controlled. 

But you should be fine getting a speaker with a bigger magnet in a closed back cab.

 

Celestions might need it a little more at ~97+ dB usually, mines sat below 94.

I don't really see why a bigger magnet would allow greater max bass response if the limit is the excursion, not power handling.

I'd have thought that resonance frequency and xlim are more important specs here.