Ampeg Isovent - Jack Plate Circuit Board.

[DJ Bebop]

 

[jthisdell]

Nice but today we do not need enclosures that are 15 feet tall to produce good lows.

 

[farace]

I found my old Ampeg catalogs. The IsoVent first appeared in the 1993 catalog (though I saw it in the shop in '92), a single model SVT50DL. In 1994 there were two versions, the SVT50HE (with Celestion 10") and SVT50 Pro (with special design 10"). The previous year's SVT50DL appears to be the same as the Pro, if we can go by the listed weight of the magnets. Both versions have a 600-watt limit (1200 peak). There is a small cutaway diagram that I can scan if desired (and if I can uncover my scanner).

 

[DJ Bebop]

Nice but today we do not need enclosures that are 15 feet tall to produce good lows.

Or to throw it 2 miles away!

 

[Nicholas Orick]

Okay I went back to your first post and pulled a photo.

View attachment 3682114

Weird that some have the ports on the back, and some have them on the slanted baffle that holds the 15s.

Exactly.

.

 

[Nicholas Orick]

I found my old Ampeg catalogs. The IsoVent first appeared in the 1993 catalog (though I saw it in the shop in '92), a single model SVT50DL. In 1994 there were two versions, the SVT50HE (with Celestion 10") and SVT50 Pro (with special design 10"). The previous year's SVT50DL appears to be the same as the Pro, if we can go by the listed weight of the magnets. Both versions have a 600-watt limit (1200 peak). There is a small cutaway diagram that I can scan if desired (and if I can uncover my scanner).

 

[Nicholas Orick]

I found my old Ampeg catalogs. The IsoVent first appeared in the 1993 catalog (though I saw it in the shop in '92), a single model SVT50DL. In 1994 there were two versions, the SVT50HE (with Celestion 10") and SVT50 Pro (with special design 10"). The previous year's SVT50DL appears to be the same as the Pro, if we can go by the listed weight of the magnets. Both versions have a 600-watt limit (1200 peak). There is a small cutaway diagram that I can scan if desired (and if I can uncover my scanner).

I have the HE.

.

 

[Nicholas Orick]

No, on the SVR cabs both the front- and rear-facing drivers are powered. There is a crossover so that only the lowest lows go to the rear, and above that to the front (don't remember the spec but if I find the catalog I can check). There is also a front-facing horn with on/attenuation/off switch. No passive radiators on these cabs. (I did have a pair of Panasonic Thrusters stereo speakers in college that used passive radiators, though.)

In the Isovent all Radiators are Active.

I thought you were refering to something else that had one Active and one Passive.

 

[thetragichero]

 

[Jeff Scott]

Do you need for me to post some giant, irrelevant pics for you?

Nah, we've gotten plenty of those, so far.

Those cabs were bipole rather than isobaric.

The drivers are wired the same, electrically? (- to -;+ to +)

 

[Wasnex]

The drivers are wired the same, electrically? (- to -;+ to +)

Agreed. If the drivers were wired out of phase, the cab would be a dipole instead of a bipole.

 

[pfschim]

View attachment 3682167 View attachment 3682118 View attachment 3682121 View attachment 3682122 View attachment 3682123 View attachment 3682144 View attachment 3682145 View attachment 3682118 View attachment 3682121 View attachment 3682122 View attachment 3682123

I think the T18 will be a good cab for just doing gigs and trashing it.

I know there are far better and more expensive speaker systems, but for a far lesser expensive, and for bass players just gigging on a much lower budget, the T18 makes an excellent choice.

Obviously the T18 is No Match for the newer far more and much more expensive systems of today.

For example the T18 is No Match when compared to the JBL VRX, but for a modest club or venue, the T18 is NOT a bad speaker to consider.

However the T18 is NOT High End Gear.

I know this already.

That said, what would you recommend?

For a basic system I think my Bag End does okay.

Good basic and NOT too expensive.

Now if I had a whole lot of Extra Money, Bag End has come out withthe Quartz bass speaker, and I would probably consider one of these.

What would you recommend for lower budget and for higher budget?

Just curious.

.View attachment 3682118 View attachment 3682121 View attachment 3682122 View attachment 3682123

DUDE! ... what the heck are you doing that keeps loading all these pointless pics into your responses ? ... on one hand it kind of adds to the strange comedy of this thread, OTOH it is very annoying and surely must be avoidable.

 

[TonH]

See attachment for the schematics of the SVR:
www.riverband.demon.nl/SVR212 Schematics.PDF

The drivers a wired the same - to - , + to +, so bipole?

Anyway when I look at the values of the components of the crossover on that schematics, the crossover frequencies would be 300Hz (LPF rear speaker) and 6000Hz (HPF tweeter) while the manual states 150Hz and 4000Hz. Both speakers and the tweeter are 8 Ohm. Or am I wrong?

 

[Nicholas Orick]

DUDE! ... what the heck are you doing that keeps loading all these pointless pics into your responses ? ... on one hand it kind of adds to the strange comedy of this thread, OTOH it is very annoying and surely must be avoidable.

I am NOT the one doing it. For some reason I load four pics into a post, and all of the sudden the whole thing went buck wild, and loaded the pics in several locations.

I think it is a malfunction on the Talkbass site.

I had Nothing to do with it. In fact some of the pics I intended for one posting wound up in others.

 

[staccatogrowl]

Must be Talkbass auto-interpret response using folded horn, isobaric, and isovent code pathways. .

 

[Redbrangus]

Maybe you could stop posting pics altogether until you figure out what's happening, or least try to curb your enthusiasm and limit the number of pics. I'm pretty sure no one here needed any pics or explanations of how a folded horn works, for instance.

I can't remember exactly how it works, but clicking on the 'picture' icon (next to the emoji icon) allows you to post a pic without loading it as a media file, which is what happens when you click on the 'camera' icon. I think. Maybe that makes a diff.

 

[jthisdell]

Maybe you could stop posting pics altogether until you figure out what's happening, or least try to curb your enthusiasm and limit the number of pics..

Personally I'd like to see MORE pics of this fantastic cab and of course more examples of folded horn cabs, of which this one is not. What's it look like again?

 

[Nicholas Orick]

Okay I went back to your first post and pulled a photo.

View attachment 3682114

Weird that some have the ports on the back, and some have them on the slanted baffle that holds the 15s.

True.

Some sort of angled cabs show a slit or slot or bandpass gap between the speaker cone and the internal volume.

There were several variants of the Isovent over a brief period of time, and with only about 357 or so made, it can be seen there was a struggle with the design it's short run, and it is clear the Isovent didn't become a marketing hit for Ampeg, or they would have continued running it for a whole lot longer.

For a cab that saw less than 400 manufactured, there seems to be a huge controversay, and a sort of strange sub culture developed concerning the Isovent design.

In one sense I actually wonder why I am going to so much trouble with this Isovent, but there is something about it that has an appeal for me, and I think it has to do with the Isobraically loaded 15s, and it is almost a once done I cant go back - type of things, so we will see what the guys and I can do with it. If we can somehow get sonething useful accomplished with this Isocent then it will become sort of an odd oddity to be used.

 

[seamonkey]

See attachment for the schematics of the SVR:
www.riverband.demon.nl/SVR212 Schematics.PDF

The drivers a wired the same - to - , + to +, so bipole?

Anyway when I look at the values of the components of the crossover on that schematics, the crossover frequencies would be 300Hz (LPF rear speaker) and 6000Hz (HPF tweeter) while the manual states 150Hz and 4000Hz. Both speakers and the tweeter are 8 Ohm. Or am I wrong?

With the use of a stereo amp with a DSP to manipulate the phase/delay to the drivers, this type of arrangement could be wired as a cardioid sub.

This kind of arrangement is very valuable steering the lows to go the direction towards the audience and just everywhere. Can sound louder out front with lower "mud".

Even high end studio monitors like Kii Audio use this approach to help take the control room/space out of the equation.

 

[Wild Rice Chris]

.

That said, what would you recommend?

I'm sure the commercial user policy of talkbass prevents Andy (agedhorse) from answering, as well as his professional courtesy to competitors.

But you should really try playing some of the cabinets he's designed recently. And by that, I mean literally the entire current bass cab lineup from Mesa/Boogie.
MESA/Boogie®

Most of what you're referring to as "modern" cabs throughout this thread are 25+ year old designs. Work the advancements in amps and cabs, I wouldn't consider anything older than ten years to be even close to modern.