Ampeg Isovent - Jack Plate Circuit Board.

[frankie5string]

Details, details, details...

All of these solutions are more expensive than the cabinet it worth by a long shot. Reminds me of home studio guys who wouldn't worry about the quality of the tracking because they were going to fix it in the mix. I'll bet very few ever became successful that way.

DSP isn't going to fix the problem any more than parametric eq is going to fix the problem... mask the problem maybe, but it's not a true fix.

No, I agree. But the ROLLS unit is probably the easiest way to tune out whatever frequencies are offending him. That's all I was getting at. Then again, companies like Apogee and Bose relied very heavily on analog signal processing between the input and the power amp. So if there's any hope in hell of slightly correcting that cabinet for him, a Para-EQ will at least get him close, and he can use his ears to decide on what he likes.

Otherwise this whole thread just wreaks of toxoplasmosis...

 

[DJ Bebop]

Details, details, details...
Reminds me of home studio guys who wouldn't worry about the quality of the tracking because they were going to fix it in the mix. I'll bet very few ever became successful that way.

I try to teach my home recording buddies. If you get your tracking together beforehand, mic placement, gain structure, sound quality, etc. You hardly have to mix, let alone fix

 

[frankie5string]

I try to teach my home recording buddies. If you get your tracking together, mic placement, gain structure, sound quality, etc. You hardly have to mix

Lol... don't tell that to anyone who uses API or Tab preamps... Some of us love our processing.

 

[DJ Bebop]

Lol... don't tell that to anyone who uses API or Tab preamps... Some of us love our processing.

That's cool!
Don't you use that in tracking anyway? That's the part to pay more attention to, the tracking.

 

[Nicholas Orick]

Details, details, details...

All of these solutions are more expensive than the cabinet it worth by a long shot. Reminds me of home studio guys who wouldn't worry about the quality of the tracking because they were going to fix it in the mix. I'll bet very few ever became successful that way.

DSP isn't going to fix the problem any more than parametric eq is going to fix the problem... mask the problem maybe, but it's not a true fix.

Well besides throwing the Isovent away, which I am NOT going to do, what is going to fix the F Bomb problem?

 

[PraiseBassing]

Details, details, details...

All of these solutions are more expensive than the cabinet it worth by a long shot. Reminds me of home studio guys who wouldn't worry about the quality of the tracking because they were going to fix it in the mix. I'll bet very few ever became successful that way.

DSP isn't going to fix the problem any more than parametric eq is going to fix the problem... mask the problem maybe, but it's not a true fix.

Just hoping to keep him from buying two amps.

 

[DJ Bebop]

Well besides throwing the Isovent away, which I am NOT going to do, what is going to fix the F Bomb problem?

Maybe glue and clamps.

 

[frankie5string]

That's cool!
Don't you use that in tracking anyway? That's the part to pay more attention to, the tracking.

Yes, but sometimes I'll run something already tracked back out and through the preamps to beef them up a little bit. It's not always a straight though-into the ADC.

 

[DJ Bebop]

Yes, but sometimes I'll run something already tracked back out and through the preamps to beef them up a little bit. It's not always a straight though-into the ADC.

That's cool too!
At least you're not trying to fix something

 

[agedhorse]

No, I agree. But the ROLLS unit is probably the easiest way to tune out whatever frequencies are offending him. That's all I was getting at. Then again, companies like Apogee and Bose relied very heavily on analog signal processing between the input and the power amp. So if there's any hope in hell of slightly correcting that cabinet for him, a Para-EQ will at least get him close, and he can use his ears to decide on what he likes.

Otherwise this whole thread just wreaks of toxoplasmosis...

Both the Bose and the Apogee (which I did some design work for many years ago) products are based on solid science and the cause of the non-linearities were easily defined and quantified. That made (at least most of) the corrections more practical. The Apogee processing was both eq and dynamics based, most of those products were trying to get the most SPL out of the box. I think that's the project where I learned about IASYS, specifically to quantify speaker non-linearities.

Well besides throwing the Isovent away, which I am NOT going to do, what is going to fix the F Bomb problem?

You are not going to like the answer, but the resonances are part of the basic concept of that approach, it's built into the design and can not be separated out... not without changing the 15" section to become a 15" bass reflex section. Then, it becomes a viable option, but requires some wood working experience. It also gives you the option of using a 15" driver with well defined and known parameters.

There's a reason no other designers of bass guitar speakers has done this, it simply does not and can not work well. It doesn't matter what you wish, you believe, or demand, the limitations are within the basic concept. Ironically, Ampeg went on to discontinue this product and release some very good ported cabinets without these artifacts, and they were well accepted because they worked and worked well.

 

[Jim C]

There's a reason no other designers of bass guitar speakers has done this, it simply does not and can not work well. It doesn't matter what you wish, you believe, or demand, the limitations are within the basic concept. Ironically, Ampeg went on to discontinue this product and release some very good ported cabinets without these artifacts, and they were well accepted because they worked and worked well.

610 posts and the facts haven't mattered yet! I admire your patience and persistence though.
Anybody else lost complete interest the original scope and just want to see how crazy the ending is?

 

[thetragichero]

I've already invested so much time I'm along for the ride

 

[agedhorse]

610 posts and the facts haven't mattered yet! I admire your patience and persistence though.
Anybody else lost complete interest the original scope and just want to see how crazy the ending is?

Well Jim, there are some members who PM'd me interested in some of the reasons why things work or don't work, they are trying to learn and are open to the facts as I am presenting them. It's mostly for those folks...

 

[DJ Bebop]

610 posts and the facts haven't mattered yet! I admire your patience and persistence though.
Anybody else lost complete interest the original scope and just want to see how crazy the ending is?

 

[DJ Bebop]

I've already invested so much time I'm along for the ride

 

[mexicanyella]

...Also you haven't asnwered my question.

What would you recommend that could be considered "More Modern"?

Something Self Powered.

And I don't want your guys making excuses for why you can't answer.

View attachment 3683750

I think this has been covered more than once in this thread, but even if I’m mistaken, pretty much all the amps and cabs-related posts on TB address this question if you read them with an eye towards current trends. The modern way involves the fact that big wattage is cheap and readily available now. Mega-high-performance, lightweight drivers—neodymium magnets, take a bow!—are available now. So the modern way uses big watts from light, compact amps to drive power-hungry drivers in tuned, ported boxes. It takes a lot of power, but the acoustic performance is more even and accurate over a wider range.

Whereas in the not-so-distant past, watts were expensive, heavy and bulky and driver technology was not what it is today, so various box technologies like folded horns and isobaric cabs were tried as means to extract maximum SPL from limited watts and driver technology. The tradeoff for the performance boost was bulk, weight, woodworking complexity and the fact that the performance boost only worked over a narrow range of frequencies.

I see this as being analogous to engine technology and performance, in a way. I drive a ho-hum 2014 Grand Caravan. It has a 3.6-liter V6 with nearly 300 hp, which produces something like 90% of its peak torque over most of its operating range, on regular gas, and idles smoothly and quietly while getting mpg in the mid 20s in a vehicle that weighs more than two tons.

It does this because it’s got a bunch of computer control over variable valve timing, fuel delivery, ignition timing, throttle position and a six-speed automatic tranny. It’s pretty good at pulling reasonable performance out of this little engine in this heavy vehicle by juggling a bunch of parameters.

When I was a high-school gearhead, this would have been science fiction. 300 hp back then from an engine that size would have involved a really high compression ratio, a wild cam, giant ports and heavy breathing through multiple carburetors, idling rough and a narrow useful powerband that started somewhere north of 2,000 rpm. And getting about 7 mpg on your way to buy 100+ octane gas at the local airport.

You could have done it with 1980s tech, but it would have involved heavy compromises with significantly worse drivability. And emissions that wouldn’t pass inspection in anything made after 1966 or so.

In my comparison, buying $3.00-per-gallon avgas to get 7 noisy, revvy mpg is your F-Bomb.

And adding additional EQ control to tame that F-Bomb is analogous to swapping in a later-model fuel-injected computer-controlled engine, because you like the car despite its limitations compared to newer cars that handle better and are more advanced in various ways. Some guys like to do stuff like that, even though it’s more work (and involves more work-arounds) than just buying a better-performing new car.

 

[mexicanyella]

Having just typed all that, it occurs to me that maybe you could re-string and re-tune so your lowest note is higher than F. Say, F# standard or G standard. Get up above that problematic resonance. With the right bunch of experimental bandmembers, that could be fun to explore. Find a drummer who uses a small kick, and somebody that plays tenor guitar, or some brass...In the right context, it could sound interesting...let that cab’s limitations or idiosyncrasies be an inspiration in a new direction. Hey, Mark Sandman and his two-string slide bass (tuned D and A, I think) did some cool stuff with baritone sax and drums in the band Morphine.

EDIT: I am pretty far off the “how do I fix this cab’s issue” here but I’m not making fun. Trying to think outside the box, so to speak. See what I did there...Anyway, you’ve mentioned having other rigs, so if the F-Bomb turns out to be an unavoidable acoustic “feature” of this cab no matter what, this is one way you might be able to keep it and have fun with it without the resonance F-ing up your playing fun.

 

[Nicholas Orick]

View attachment 3684679

LOL.

That was funny.

Good one.

.

 

[Nicholas Orick]

I think this has been covered more than once in this thread, but even if I’m mistaken, pretty much all the amps and cabs-related posts on TB address this question if you read them with an eye towards current trends. The modern way involves the fact that big wattage is cheap and readily available now. Mega-high-performance, lightweight drivers—neodymium magnets, take a bow!—are available now. So the modern way uses big watts from light, compact amps to drive power-hungry drivers in tuned, ported boxes. It takes a lot of power, but the acoustic performance is more even and accurate over a wider range.

Whereas in the not-so-distant past, watts were expensive, heavy and bulky and driver technology was not what it is today, so various box technologies like folded horns and isobaric cabs were tried as means to extract maximum SPL from limited watts and driver technology. The tradeoff for the performance boost was bulk, weight, woodworking complexity and the fact that the performance boost only worked over a narrow range of frequencies.

I see this as being analogous to engine technology and performance, in a way. I drive a ho-hum 2014 Grand Caravan. It has a 3.6-liter V6 with nearly 300 hp, which produces something like 90% of its peak torque over most of its operating range, on regular gas, and idles smoothly and quietly while getting mpg in the mid 20s in a vehicle that weighs more than two tons.

It does this because it’s got a bunch of computer control over variable valve timing, fuel delivery, ignition timing, throttle position and a six-speed automatic tranny. It’s pretty good at pulling reasonable performance out of this little engine in this heavy vehicle by juggling a bunch of parameters.

When I was a high-school gearhead, this would have been science fiction. 300 hp back then from an engine that size would have involved a really high compression ratio, a wild cam, giant ports and heavy breathing through multiple carburetors, idling rough and a narrow useful powerband that started somewhere north of 2,000 rpm. And getting about 7 mpg on your way to buy 100+ octane gas at the local airport.

You could have done it with 1980s tech, but it would have involved heavy compromises with significantly worse drivability. And emissions that wouldn’t pass inspection in anything made after 1966 or so.

In my comparison, buying $3.00-per-gallon avgas to get 7 noisy, revvy mpg is your F-Bomb.

And adding additional EQ control to tame that F-Bomb is analogous to swapping in a later-model fuel-injected computer-controlled engine, because you like the car despite its limitations compared to newer cars that handle better and are more advanced in various ways. Some guys like to do stuff like that, even though it’s more work (and involves more work-arounds) than just buying a better-performing new car.

I hear you loud and clear.

I knew all along the Isovent was a dated concept compared to what we have going today, but just for fun I decided to get it anyway, and based upon what you guys are saying today, once whatever is to be done with the Isovent is done, down the road a little bit, I am going to go far more modern with my next acquisition.

Isovent today/something like the Bose tomorrow.

 

[Nicholas Orick]

Having just typed all that, it occurs to me that maybe you could re-string and re-tune so your lowest note is higher than F. Say, F# standard or G standard. Get up above that problematic resonance. With the right bunch of experimental bandmembers, that could be fun to explore. Find a drummer who uses a small kick, and somebody that plays tenor guitar, or some brass...In the right context, it could sound interesting...let that cab’s limitations or idiosyncrasies be an inspiration in a new direction. Hey, Mark Sandman and his two-string slide bass (tuned D and A, I think) did some cool stuff with baritone sax and drums in the band Morphine.

EDIT: I am pretty far off the “how do I fix this cab’s issue” here but I’m not making fun. Trying to think outside the box, so to speak. See what I did there...Anyway, you’ve mentioned having other rigs, so if the F-Bomb turns out to be an unavoidable acoustic “feature” of this cab no matter what, this is one way you might be able to keep it and have fun with it without the resonance F-ing up your playing fun.

NOT likely to DeTune the fretless six, especially when it uses a 2TEK brdige which prohibits DeTuning, but what you are suggesting reminds me if the Picollo Bass.