Ampeg Isovent - Jack Plate Circuit Board.

[DJ Bebop]

NOT knocking Peavy but I'd take an Ampeg Isovent any day of the week.

This Peavy doesn't have half the power.View attachment 3680711 View attachment 3680712 View attachment 3680713 View attachment 3680714 View attachment 3680715 View attachment 3680716

At least my cabinet was working And I actually played gigs with it instead of it sitting in my garage or basement.
So, it's twice the power of a dead cab!

 

[Nicholas Orick]

As per my earlier post: this is a weirdly interesting speaker system. The over-all concept is one that should find real favor on this forum: a smallish 2-way, 210 box on top of a small, efficient sub system, in a single compact enclosure. And the 210 part of the box is angled upward toward the player; what an idea! The weirdness (for me) comes in with the concept of running two 15" drivers in tandem (front-to-front, clamshell-fashion) as a single driver with a greatly-reduced compliance. Although I very much doubt that's a completely new idea, it's a new concept to me. The sales lit and owner's manual are pretty uninformative, but it appears to me that it's a sorta conventional 2-way system consisting of a 210 box with a conventional passive crossover/HF driver combo (with incandescent lamp limiter, as evidenced in the pix) supplemented by a somewhat unconventional sub arrangement, which I gather is just running in parallel with the 210s. The HF driver is passively crossed over at 5KHz; the 'bi-amp' feature seems to allow the user to separate the 10s from the 'sub' and the HF driver is still passively crossed over from there. It's kind of hard to tell that for sure...the lit tells you how to hook up the bi-amp function, but offers no clue as to what a crossover frequency is likely to be. Seriously...there is no clue as to what crossover frequency to use. The only reference to crossover frequency was a nebulous spec of "Crossover Point: 5 KHz, Crossover Slope: 12dB/octave", which clearly is referring to the passive crossover for the HF unit. But the two "Bi-amp" inputs are each rated at 300 watts/8 ohms and the total cab rating is 600 watts/4 ohms, so it seems fairly clear that the bi-amping function is between the 15s and the 10s. This is a great idea in concept, but it would be helpful if the manufacturer actually informed you of that, and perhaps provided a recommended possible frequency range for the active crossover. I think many end-users, relatively uninformed about bi-amping, would employ a crossover frequency that would be much too high for the how this cab should be used. The GK bi-amp system employed in the RB series, for instance, would be useless hooked up to this box.

In passive mode, with the 210s and that weird clamshell sub running in parallel, the performance is likely to be a bit peculiar, IMO, but running it bi-amped might yield some real advantages. Employing a crossover point in the usual sort of 'sub' range, 80-120 Hz, would relegate the lowest octave or so to that weird dual-15 sub, which likely has pretty uneven performance above that anyway, while freeing the 10s of the burden of carrying that part of the spectrum, which should allow them to really soar. Seems like a pretty good idea to me.
OP: I'm still wondering about the answer to this question.

Your response here I really liked.

Shows an Appreciation and Understanding

for the Isovent Concept.

 

[Nicholas Orick]

Again, and this justifies repeating, the crossover can't possibly have ANYTHING to do with what you are experiencing because it operates octaves away from where the problem exists.

The crossover has NOTHING to do with where the two low frequency sections combine, they affect the tweeter response only.

The ONLY thing that's common to the problem is the low frequency drivers AND THE CABINET.

This is a known challenge with this type of cabinet design, which is why it's rarely used.

(Is this a clear enough explanation?)

Okay you suggest a different cabinet.

What is it about this Isovent design that could be said - doesn't work, and what kind of cabinet you say is likely to probably - work?

Moreover why did Ampeg choose this design then?

Just curious.

 

[thetragichero]

 

[agedhorse]

Okay you suggest a different cabinet.

What is it about this Isovent design that could be said - doesn't work, and what kind of cabinet you say is likely to probably - work?

Moreover why did Ampeg choose this design then?

Just curious.

As a generality, because I'm not going to get into a debate on specifics of this manufacturer or product...

Back when amps were not very powerful, there were many attempts to increase the efficiency of speaker cabinets in general. Bass guitar and PA cabinets were most common to be affected. One of the biggest tradeoffs is the exchange of higher efficiency for artifacts such as poor frequency response, increased distortion, resonant effects (also called the "one note bass" problem), large size and high weight. The isovent cabinet, just like a variety of different cabinets that went down this very path, all suffered from the same issues. BUT, these issues were better than not being heard at all.

When amps became more powerful, designers could focus on smoother, less erratic frequency response, smaller designs, lighter weight which is almost exclusively what we see the results of today (including from Ampeg). The market evolved to what was actually more important once the stumbling block of "not enough volume" was resolved.

Generally, the ported (or bass reflex) designs have become the most common due to their good efficiency, frequency response, low frequency extension and size/weight/power handling. These would be followed by sealed cabinets (acoustic suspension) which trade off some low frequency sensitivity and extension (at higher sensitivity) for a sometimes tighter sound, a different low and mid character, etc. BOTH types of cabinets are in fact viable.

This is why you don't see any major builders going down this road anymore.

 

[pfschim]

I suggested this way, way back!

ha!, I thought we would eventually find ourselves on the same side of an issue at some point.

 

[Nicholas Orick]

As a generality, because I'm not going to get into a debate on specifics of this manufacturer or product...

Back when amps were not very powerful, there were many attempts to increase the efficiency of speaker cabinets in general. Bass guitar and PA cabinets were most common to be affected. One of the biggest tradeoffs is the exchange of higher efficiency for artifacts such as poor frequency response, increased distortion, resonant effects (also called the "one note bass" problem), large size and high weight. The isovent cabinet, just like a variety of different cabinets that went down this very path, all suffered from the same issues. BUT, these issues were better than not being heard at all.

When amps became more powerful, designers could focus on smoother, less erratic frequency response, smaller designs, lighter weight which is almost exclusively what we see the results of today (including from Ampeg). The market evolved to what was actually more important once the stumbling block of "not enough volume" was resolved.

Generally, the ported (or bass reflex) designs have become the most common due to their good efficiency, frequency response, low frequency extension and size/weight/power handling. These would be followed by sealed cabinets (acoustic suspension) which trade off some low frequency sensitivity and extension (at higher sensitivity) for a sometimes tighter sound, a different low and mid character, etc. BOTH types of cabinets are in fact viable.

This is why you don't see any major builders going down this road anymore.

I see.

The basic box seems to be the best approach then.

I have a Bag End 18, which I like, and contrary to popular opinion, I am going to continue forging ahead with fixing up the Isovent, but later on after Other Obligations have been met, I have been toying around with the idea of using a B52 Folded Horn with my Ampeg SVP 1600. The power rating of both the SVP and B52 Folded Horn are just about identical.

I have always liked the sound of folded horns, I used to have a rig comprised of an Ampeg 4 Pro and B52 folded horn, and thought it was the coolest most awesome rig.

What do you think?

.

 

[DJ Bebop]

Okay you suggest a different cabinet.

What is it about this Isovent design that could be said - doesn't work, and what kind of cabinet you say is likely to probably - work?

Moreover why did Ampeg choose this design then?

Just curious.

The same reason this was built:

It was a design that was used, in the past the is not relevant anymore.

Let's look at the purpose your cab was built. It was to try and produce as much output as an 8x10 cabinet another old design, in maybe a smaller package. So it was designed using an old design and then marketed. Apparently it didn't work as hoped and they discontinued it. Funny thing is the other old designed 8x10 is still being manufactured down to today. This cabinet has never been brought back into production. For a reason.

 

[Nicholas Orick]

View attachment 3680756 View attachment 3680757 View attachment 3680758 View attachment 3680762 View attachment 3680763 View attachment 3680756 View attachment 3680757 View attachment 3680758 View attachment 3680762 View attachment 3680763

@Redbrangus
@agedhorse

I see.

The basic box seems to be the best approach then.

I have a Bag End 18, which I like, and contrary to popular opinion, I am going to continue forging ahead with fixing up the Isovent, but later on after Other Obligations have been met, I have been toying around with the idea of using a B52 Folded Horn with my Ampeg SVP 1600. The power rating of both the SVP and B52 Folded Horn are just about identical.

I have always liked the sound of folded horns, I used to have a rig comprised of an Ampeg 4 Pro and B52 folded horn, and thought it was the coolest most awesome rig.

What do you think?

.

 

[pfschim]

I see.

The basic box seems to be the best approach then.

I have a Bag End 18, which I like, and contrary to popular opinion, I am going to continue forging ahead with fixing up the Isovent, but later on after Other Obligations have been met, I have been toying around with the idea of using a B52 Folded Horn with my Ampeg SVP 1600. The power rating of both the SVP and B52 Folded Horn are just about identical.

I have always liked the sound of folded horns, I used to have a rig comprised of an Ampeg 4 Pro and B52 folded horn, and thought it was the coolest most awesome rig.

What do you think?

.

umm, OP, would you please consider NOT posting 10 pics on every reply ... makes it a PITA to scroll through the posts, and as far as I can tell it does not add anything to your posts.

 

[Nicholas Orick]

umm, OP, would you please consider NOT posting 10 pics on every reply ... makes it a PITA to scroll through the posts, and as far as I can tell it does not add anything to your posts.

I duplicated by mistake.

 

[Nicholas Orick]

At least my cabinet was working And I actually played gigs with it instead of it sitting in my garage or basement.
So, it's twice the power of a dead cab!

You guys have been jumping down my back.

You want to make fun of me, you do so at your own peril, because I can return it any time any day of the week.

You like your Peavy and I like my Ampeg.

How about we leave it at that.

And while you guys have been making fun, you have offered Nothing of Value towards my moving forward with the Isovent project.

Renbranger and Aged Hourse plus maybe one or two others seem to know something and they are the only ones talking seriously while the rest of you have been posting stupid videos.

So you get what you get.

If you can't take it then don't dish it out.

 

[DJ Bebop]

As a generality, because I'm not going to get into a debate on specifics of this manufacturer or product...

Back when amps were not very powerful, there were many attempts to increase the efficiency of speaker cabinets in general. Bass guitar and PA cabinets were most common to be affected. One of the biggest tradeoffs is the exchange of higher efficiency for artifacts such as poor frequency response, increased distortion, resonant effects (also called the "one note bass" problem), large size and high weight. The isovent cabinet, just like a variety of different cabinets that went down this very path, all suffered from the same issues. BUT, these issues were better than not being heard at all.

When amps became more powerful, designers could focus on smoother, less erratic frequency response, smaller designs, lighter weight which is almost exclusively what we see the results of today (including from Ampeg). The market evolved to what was actually more important once the stumbling block of "not enough volume" was resolved.

Generally, the ported (or bass reflex) designs have become the most common due to their good efficiency, frequency response, low frequency extension and size/weight/power handling. These would be followed by sealed cabinets (acoustic suspension) which trade off some low frequency sensitivity and extension (at higher sensitivity) for a sometimes tighter sound, a different low and mid character, etc. BOTH types of cabinets are in fact viable.

This is why you don't see any major builders going down this road anymore.

The same reason this was built:
View attachment 3680768
It was a design that was used, in the past the is not relevant anymore.

Let's look at the purpose your cab was built. It was to try and produce as much output as an 8x10 cabinet another old design, in maybe a smaller package. So it was designed using an old design and then marketed. Apparently it didn't work as hoped and they discontinued it. Funny thing is the other old designed 8x10 is still being manufactured down to today. This cabinet has never been brought back into production. For a reason.

I see while I was writing a response. Andy came through with a thorough response

 

[two fingers]

Working on it.

Ordered stuff.

.

I know we're giving you a bunch of crap. That's what we do. I hope it works our for you.

A word of advice. Do NOT blow one of those 10" speakers. I owned one of those Isovent cabs years ago (back when they were new). The up side? It sounded the same in the back of the room as it did 5 feet in front of it. The downside? It was a muddy mess of a tone. It sounded big, but no definition or clarity.

Also, I blew one of the 10" speakers. According to my tech, and he called Ampeg directly, those speakers were designed by David Eden, were only made for that cab, and can't be found anywhere. We did the math and came up with the closest spec 10" speaker we could find. The cab wound up even LESS defined than before.

Either way, I'm with the rest of the crowd who thinks the tweeter circuit has zero to do with your issues. But, for your sake, I hope I'm wrong.

 

[Nicholas Orick]

I know we're giving you a bunch of crap. That's what we do. I hope it works our for you.

A word of advice. Do NOT blow one of those 10" speakers. I owned one of those Isovent cabs years ago (back when they were new). The up side? It sounded the same in the back of the room as it did 5 feet in front of it. The downside? It was a muddy mess of a tone. It sounded big, but no definition or clarity.

Also, I blew one of the 10" speakers. According to my tech, and he called Ampeg directly, those speakers were designed by David Eden, were only made for that cab, and can't be found anywhere. We did the math and came up with the closest spec 10" speaker we could find. The cab wound up even LESS defined than before.

Either way, I'm with the rest of the crowd who thinks the tweeter circuit has zero to do with your issues. But, for your sake, I hope I'm wrong.

Thank You.

I appreciate the enthusiasm, concern, and straight forward experience and opinion.

Much Obliged.

 

[Wasnex]

As a generality, because I'm not going to get into a debate on specifics of this manufacturer or product...

Back when amps were not very powerful, there were many attempts to increase the efficiency of speaker cabinets in general. Bass guitar and PA cabinets were most common to be affected. One of the biggest tradeoffs is the exchange of higher efficiency for artifacts such as poor frequency response, increased distortion, resonant effects (also called the "one note bass" problem), large size and high weight. The isovent cabinet, just like a variety of different cabinets that went down this very path, all suffered from the same issues. BUT, these issues were better than not being heard at all.

When amps became more powerful, designers could focus on smoother, less erratic frequency response, smaller designs, lighter weight which is almost exclusively what we see the results of today (including from Ampeg). The market evolved to what was actually more important once the stumbling block of "not enough volume" was resolved.

Generally, the ported (or bass reflex) designs have become the most common due to their good efficiency, frequency response, low frequency extension and size/weight/power handling. These would be followed by sealed cabinets (acoustic suspension) which trade off some low frequency sensitivity and extension (at higher sensitivity) for a sometimes tighter sound, a different low and mid character, etc. BOTH types of cabinets are in fact viable.

This is why you don't see any major builders going down this road anymore.

I thought the advantage of Isobaric loading is it allowed designers to overcome the limitation of vintage drivers so they could produce deep bass with a relatively small cabinet. There was a trade off in efficiency and max SPL because only the radiating area of one driver couples with the room.

Modern drivers can be designed to give low response in small cab, so it is no longer considered an advantage to use isobarik loading. The isobarik cost more, weighs more, and has lower efficiency and max SPL.

Of course, I still think the Isovent is sort of a hybrid between an isobarik and a short tapped horn. But I believe it was made before the math to really understand and optimize tapped horns was widely known, and Ampeg may not have even treated it as a tapped horn.

 

[Redbrangus]

Your response here I really liked.
Too many photos here....
Shows an Appreciation and Understanding for the Isovent Concept.

Thanks for that, but you may have misunderstood my appreciation for it. I like that the 10s are angled upward toward the player. I do kinda, sorta like the format of the thing--a box with smaller drivers supplemented by a sub. But this box doesn't really do that unless you biamp it...re, my discussion about it way back there somewhere. It's just two 10s and two 15s, all paralleled together, with the 15's utilized in a fairly unconventional manner. And somewhere in the 'system', meaning the 2-15s and the 2-10s AND the enclosure in which they are operating, there is a problematic resonance--the F-bomb. At least that's my interpretation of what's happening. I'm reasonably certain that when you get your rewired, non-high-pass-filtered-and-limited jack plate back in place that you'll find you still have the phenomenon. If not...good on you. But if you do, then maybe you can try some things that might be more effective.

Big, BIG caveat: the 15s HAVE to be connected out-of-'phase' (polarity) from each other. Presumably you marked or otherwise noted the wiring scheme and got it connected back up right. Edit: This is crucial...those drivers won't last 5 seconds when played at level if they're connected up back-asswards.

 

[QRanc]

You guys have been jumping down my back.

You want to make fun of me, you do so at your own peril, because I can return it any time any day of the week.

You like your Peavy and I like my Ampeg.

How about we leave it at that.

And while you guys have been making fun, you have offered Nothing of Value towards my moving forward with the Isovent project.

Renbranger and Aged Hourse plus maybe one or two others seem to know something and they are the only ones talking seriously while the rest of you have been posting stupid videos.

So you get what you get.

If you can't take it then don't dish it out.

ok

 

[Redbrangus]

And there's this: I've asked you to confirm this twice and still haven't seen any response to the very basic query...did you block up the hole where the horn/driver (tweeter in your language) had been? Do you understand why I'm asking this?

 

[DJ Bebop]

You guys have been jumping down my back.

You want to make fun of me, you do so at your own peril, because I can return it any time any day of the week.

You like your Peavy and I like my Ampeg.

How about we leave it at that.

If you had read my post on the Peavy. I sold that cab.

The so-called jumping down your back comes from. You came here, we didn't accost you on the streets.
You asked us for help and every time someone has told you what to look for. You say nah, that's not it but, what is it? We again tell you to try some things and again you tell us you know what it is and it's not what we say, without trying anything we have suggested.

Like when I tried to get you to try all of your speakers out of the box itself. Rather than leave some in as you test some outside the cabinet. The cabinet is a common point. You stopped responding to me when we got to the point where it was evident that some speakers were still attached to the cab. Your F-bomb could be a resonance problem. No acknowledgment.

I really don't care if you listen to me but, to dismiss what agedhorse has said is foolish. I wonder what you would think if you called Ampeg and they told you the same things. Would you dismiss them as well?

It's more like you want someone to agree with you rather than find an answer to your problem.