Testing speakers in a Free Standing state is a Normal Process, in fact the Fs Value is obtained from testing speaker cones in the Free Standing state.
No sympathetic vibrations in the room.
This is all the Isovent.
I am sure of it.
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Ampeg Isovent - Jack Plate Circuit Board.
- Thread starter Nicholas Orick
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Testing speakers in a Free Standing state is a Normal Process, in fact the Fs Value is obtained from testing speaker cones in the Free Standing state.
No sympathetic vibrations in the room.
This is all the Isovent.
I am sure of it.
- Feb 12, 2006
- 61,003
- 5
- 220,815
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
I understood that, and that is, in fact, what I was trying to say...that they DO operate in parallel with no crossover, but the system would work a lot better if an active crossover and two power amps were used in a true bi-amp configuration. Ampeg made provisions to do just that, but didn't explain it in any way, either on the input panel itself, or in the owner's manual. They basically just tell you "here are your bi-amp inputs, hook 'em up and have at it".
It kind of seems to me as if the whole isobaric thing is like horn-loaded LF speaker systems...it was maybe worth trying to engineer around the idiomatic problems when drivers were limited to about 100-200 watts, but we've got more powerful components available now and can take a more hi-fi approach to high-performance sound.
So, the 15s and 10 are actually just connected together, all four drivers running full range, with no crossover between them?
Come, again?
See attached crossover from [Invalid or Expired Link Removed]
The schematic appears to be only a HPF for the horn with a pad and on/off switch.
So the woofers are connected together and the polarity of one of the 15s is electrically reversed, so it will be physically in phase in the cab. The connection from the input jacks to the woofer is straight through and does not go through any crossover components. Turning the tweeter control to off will isolate the crossover from the woofers, so there is no need to desolder or otherwise disconnect the crossover to prove that it is not the source of the problem.
It appears that the 210 section is sealed so this part of the cab will have a natural low frequency roll off. The 10's should not have much response down at low F.
F3 is listed as 38hz, F6 is listed as 32hz, and F10 is listed as 25hz. This extended low end should cab primarily from the clamshell 15s.
If the response of the cab is not smooth in the low end I would question whether it is using OEM drivers.
Isobaric basically means constant pressure. This refers to the space between the drivers. The Orange cabs combined Isobaric with vented technology.
I believe Ampeg would have considered the Isovent a combination of isobaric, vented, and folded horn technology.
Consider the Isovent similar to the old Electro Voice SB180, except add a second internal driver in clamshell orientation. See attached.
Combining folded horn and vented technology well, results in a tapped horn. I believe these are some of the best tapped horns you can buy. Tapped Horns | Danley Sound Labs | Danley Sound Labs, Inc.
In order to achieve good loading in the horn path there would not be room for an internal driver, so Isobaric is out.
- Feb 12, 2006
- 61,003
- 5
- 220,815
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
It's more of a push-pull type configuration, which increases motor strength relative to the air mass (not driver moving mass). IME, there is more to gain from increasing the air mass by doubling the cone area acting on the air mass, which is what a conventional 215 cabinet does and without (as much of) the resonance artifacts.
You do not like this cab, get rid of it and get something that preforms to your liking.
I don't think there's any kind of horn-loading of the 15" drivers in this box. But I agree with you that Danley has done a lot with the folded horn concept...they seem to have developed it into an origami-like art form.
1) Perhaps a stupid question along the lines of "is there gas in the tank?", but is there any chance this is connected to a resonance in the bass itself? Have you tried other instruments?
2) Perhaps of more interest, when SLM sold Ampeg to Loud, one of the engineers went to work for Gregg Hopkins at Vintage Amp Restoration in St. Louis. I don't know if it's the same engineer that designed the cab, or whether he's still working there, but id guess he'd know who was the designer, and a phone call might lead to being able to talk with someone that was involved with the design of the cab (whether it's one call or several, you might track down the specific engineer).
2) Perhaps of more interest, when SLM sold Ampeg to Loud, one of the engineers went to work for Gregg Hopkins at Vintage Amp Restoration in St. Louis. I don't know if it's the same engineer that designed the cab, or whether he's still working there, but id guess he'd know who was the designer, and a phone call might lead to being able to talk with someone that was involved with the design of the cab (whether it's one call or several, you might track down the specific engineer).
Just for the record, I believe this to be a misconception. As a seasoned audio professional, I would say that "removing the bad stuff--the stuff that isn't wanted" describes about 98% of the 'EQ-ing" that I do...I rarely find a reason to turn an EQ knob to the plus side. I think that's how most folks work.
I have the other rare ampeg cab from the same era, the 215R. It has a tweeter, a front facing 15 that covers the mid frequencies below the tweeter and above 100 Hz, and a rear facing 15 that pushes the low frequencies omnidirectionally out of the back, and a 3 way x-over. I don't know much about your cabinet's x-over, but where your 15s are facing each other mine have their backs to each other. I also have a 215E and a svt ll (non-pro), but I usually use my mesa walkabout head (which is the same as the one you have in your photos), you don't need to buy a parametric eq, your amp is a parametric eq! Cut the two knobs on top of each other to the right of the mids knob, the top one will reduce to the left and boost to the right by +/- 15 the dB of the chosen frequency and the one directly beneath it will choose the frequency band from 30 Hz - 300. Find your F, 44 Hz and see if you can dial it out. Cheers.
Don't those IsoVent Ampeg cabinets require an enormous room to operate properly?
They're kinda obsoleted by modern PAs and subs.
The two upper 10s were meant for near-monitoring. The bulk of the "blast" comes from the two 15s in push-pull.
I remember they sounded so strange in small venues. It was very easy to make it honk in a very unappealing way, while shaking the bottles on the shelves behind the bar.
They're kinda obsoleted by modern PAs and subs.
The two upper 10s were meant for near-monitoring. The bulk of the "blast" comes from the two 15s in push-pull.
I remember they sounded so strange in small venues. It was very easy to make it honk in a very unappealing way, while shaking the bottles on the shelves behind the bar.
I had the SVR215, the version of that cab with the four-space rackmount section on top. I had an SVT-III (non-Pro) mounted in it. I liked it, except that I couldn't put it up against the wall on a tight stage!
Perhaps you are right, but you can't deny the similarity here with these old EV subs.
The EV SB180 and T18 are very similar
Here is a what the inside of the T18 cab looks like
Some people even install drivers backwards (magnets in) in these cabs, so you could set them up exactly as the Isovent. I don't believe there is space in the SB180 to do this.
See attached datasheet and note EV claims, The T18 "...combines the attributes of both horn-loaded and vented box designs. See page 1, paragraph 1.
I have the same cab you are referring to, farace, with the 4U rack built in on top, even if I typed the wrong letters that's what I meant, thanks for correcting me. I was looking for a lll (non-pro) for years and couldn't find one, I am more than happy with the similar mosfet power section of the Walkabout.
Just a guess—
It’s the cabinet design, not the electronics.
A notch filter via a parametric eq can remove/ reduce the offending frequency.
It’s the cabinet design, not the electronics.
A notch filter via a parametric eq can remove/ reduce the offending frequency.
As was mentioned, eliminate the bass as a possibility. Try another bass. The pickup case can be a source of resonance. Dripping a layer of wax on the back of the pickup case can sometimes fix this.
this is a long shot, but the speakers should be the same make and model. If one is a replacement, an imbalance could cause a problem.
this is a long shot, but the speakers should be the same make and model. If one is a replacement, an imbalance could cause a problem.
In the late Seventies/Early Eighties there were a plethora of similar designs put out by small speaker cabinet manufacturers around here. One was Power Supply. Over the years that followed less and less of these sometimes bizarre topologies were to be seen. Many of them looked great on paper but not so good in real life.
I feel that the OP should put his cabinet back together properly and sell it. It might well go to someone who loves the box despite the designs flaws.
I feel that the OP should put his cabinet back together properly and sell it. It might well go to someone who loves the box despite the designs flaws.
I am NOT an Audio Professional, but just a guy learning to play bass at a later date in life, and through this experience I am learning a lot, while at the same time having a lot of fun meeting people like you, who are Audio Professionals, and I tend to agree with you on this point. One shouldn't have to Dial Out UnWanted Sound but instead Dial In What is Wanted.
I like the Isovent, I intend on getting it Dialed In the way I wanted it, and I am Keeping It.
No matter what system I get, I always have to learn how to use it, and this always means Dialing It In to the way I want it.
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