Impedans problem

[Heyman]

I've got a 18" Cerwin Vega element in my sub and it has been very great.
The issue is that I've bought a full tube head and just to be sure I did check the impedans of the speaker and it is a bit weird...Either it says 3 Ohms or maby it is just a bad punched 8...

Heres the label
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And a Closeup!
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Does anyone knows about the Cerwin Vega AC 188L???? Is it the odd 3 Ohms or 8 Ohms?

If it is 3 Ohms would a 18" Eminence Kilomax be a good substitution? The cabinett 23" x 27,5" x 17" and has some bass reflex opening in the front that is 4" x 23" and placed in the lower front of the cabinett.

 

[seamonkey]

Never heard of a rated 3 ohm speaker.
I think it's a upside down or backwards stamped "E" - maybe for "Eight"

You can measure it with an ohm meter, it will measure an ohm or two below the impedance. If it's 5 or more ohms it's probably 8 ohms impedance.

 

[BillyB_from_LZ]

It's impedance...and cabinet

The Cerwin-Vega (or perhaps it was just a Vega) that Acoustic used in the 301 folded horn cabinet is rated 3.2 ohms.

 

[Kennethfaria]

wow this is a weird one.

I;ve heard of horns adding impedance, but removing it.
Either this is one efficient sub x2000, or the labels wrong. try to get to the inside.

 

[Heyman]

It's impedance...and cabinet

The Cerwin-Vega (or perhaps it was just a Vega) that Acoustic used in the 301 folded horn cabinet is rated 3.2 ohms.

To bad!!!
I will messure it with my multimeter today but as I recall 3,2 sounds familiar. You mean that it could actually be a 3,2 Ohm speaker? Is there some good substitute for this???

Is any of
Eminence Kilomax???
Eminence Sigma
or Eminence Omega?
a good substitution or does anyone have another suggestion of a god speaker for replacement?

 

[Heyman]

I've got a 18" Cerwin Vega element in my sub and it has been very great.
The issue is that I've bought a full tube head and just to be sure I did check the impedans of the speaker and it is a bit weird...Either it says 3 Ohms or maby it is just a bad punched 8...

Does anyone knows about the Cerwin Vega AC 188L???? Is it the odd 3 Ohms or 8 Ohms?

If it is 3 Ohms would a 18" Eminence Kilomax be a good substitution? The cabinett 23" x 27,5" x 17" and has some bass reflex opening in the front that is 4" x 23" and placed in the lower front of the cabinett.

I did a messure with my multimeter today and got a value between 2,4 and 2,5 Ohms...
and also found
http://cgi.ebay.com/Cerwin-Vega-18-...6566541QQihZ016QQcategoryZ23794QQcmdZViewItem
which confuses me even more....

 

[BillyB_from_LZ]

I did a messure with my multimeter today and got a value between 2,4 and 2,5 Ohms...
and also found
http://cgi.ebay.com/Cerwin-Vega-18-...6566541QQihZ016QQcategoryZ23794QQcmdZViewItem
which confuses me even more....

Your multimeter measures DC resistance...which will be lower than the Impedance which takes into account both Resistance (the DC resistance of the voice coil wire) and the Reactance (see http://en.wikipedia.org/wiki/Reactance).

The speaker on eBay has been reconed which also replaces the voicecoil. The person that reconed it chose an 8 ohm voicecoil rather than a 3.2 or 4 ohm voicecoil.

An 18 in. loudspeaker with a 4 ohm voicecoil and appropriate Thiele-Small parameters for the enclosure would be a suitable substitute. Actually, an 8 ohm loudspeaker with appropriate Thiele-Small parameters would work too...you'll just have to decide whether the increased impedance's effect on your amplifier output is an issue or not.

 

[Heyman]

Your multimeter measures DC resistance...which will be lower than the Impedance which takes into account both Resistance (the DC resistance of the voice coil wire) and the Reactance (see http://en.wikipedia.org/wiki/Reactance).

The speaker on eBay has been reconed which also replaces the voicecoil. The person that reconed it chose an 8 ohm voicecoil rather than a 3.2 or 4 ohm voicecoil.

An 18 in. loudspeaker with a 4 ohm voicecoil and appropriate Thiele-Small parameters for the enclosure would be a suitable substitute. Actually, an 8 ohm loudspeaker with appropriate Thiele-Small parameters would work too...you'll just have to decide whether the increased impedance's effect on your amplifier output is an issue or not.

yes I've heard about the messurement issue, and tnx alot for explaining the thing with reconing.
I dont know anything about the Thiele-small parameters. I've just read alot of diagrams and specifikations of the Eminence speakers
EMINENCE SIGMA PRO-18
EMINENCE OMEGA PRO-18
EMINENCE KILOMAX PRO 18 A

All of them are 8 Ohms wich seems to be a good choice since my top cabinett has that impendance.
Which values should I be looking at and which are the right ones for me?
I dont have any spec on the Cerwin Vega speaker so its hard for me to compare.
The Cervin Vega is pretty old, maby it's better to buy a new one instead of reconing the Vega and just sell it as it is???

By the way I've got a Mesa Boogie Strategy 400 to run it with so I think 8 Ohms will work.

 

[BillyB_from_LZ]

...

... The cabinett 23" x 27,5" x 17" and has some bass reflex opening in the front that is 4" x 23" and placed in the lower front of the cabinett.

That seems like a pretty small enclosure for an 18. Can you post a photo?

Also, does the port have a shelf above it projecting back into the enclosure or is just as deep as the baffle is thick?

You can do online calculations at http://www.linearteam.dk or download WinISD from the same site.

You'll need to figure out the tuning frequency of your existing enclosure to model the response of any driver that you'd install in it.

 

[Heyman]

That seems like a pretty small enclosure for an 18. Can you post a photo?

Also, does the port have a shelf above it projecting back into the enclosure or is just as deep as the baffle is thick?

You can do online calculations at http://www.linearteam.dk or download WinISD from the same site.

You'll need to figure out the tuning frequency of your existing enclosure to model the response of any driver that you'd install in it.

Ok! You really give me alot of great information I'll try the calculationprogram and see what I can figure out.
Yes is't like a shelf above the port.

I realize that different brands gives me alot to shose from but which brands shall I give energy to look up? I've just heard that Eminence is good and they are alot sheaper than Cervin Vega ,ElectroVoise or RCF.

I dont have any descent pics that shows the construktion but it's the muppet show speaker in the bottom, I'm sorry to say that the fur was ripped away some time ago

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[Heyman]

You can do online calculations at http://www.linearteam.dk or download WinISD from the same site.

Dont really get the FB value. what does it actually mean? I just found a formula that said Fb=(0,42*Fs*Qts-0,9) and if that is correct the only thing I actually put in the program is the volume of the cabinet nothing that depends on how big och long the opening is.
Every speaker model has a recomended cabinet volume, but I think the the vent and baffle should have a great part in how the cabinett and speaker works together...

Can I calculate the Fb value in some way that does not depend on the speaker?
The graph doesnt tell me much of how it will sound with for example Eminence Omega Pro element which was the one I dod a simulation for.

 

[Heyman]

Dont really get the FB value. what does it actually mean? I just found a formula that said Fb=(0,42*Fs*Qts-0,9) and if that is correct the only thing I actually put in the program is the volume of the cabinet nothing that depends on how big och long the opening is.
Every speaker model has a recomended cabinet volume, but I think the the vent and baffle should have a great part in how the cabinett and speaker works together...

Can I calculate the Fb value in some way that does not depend on the speaker?
The graph doesnt tell me much of how it will sound with for example Eminence Omega Pro element which was the one I dod a simulation for.

Just has to BUMP this cause I still want some more answers... Need tip for good replacement elements instead of the Cerwin VEga AC 188L...

 

[BillyB_from_LZ]

No one can be much help until we know whether the port has a self extending back into the enclosure or not.

The area and volume of the port (hence our need to know the depth) along with the volume of the enclosure determine the frequency that it's tuned to.

Armed with the volume of the enclosure (Vb) and the tuning frequency of the enclosure (Fb), one can use a modeling program to see which driver or drivers are an appropriate match for the enclosure.

Are the dimensions that you originally posted outside dimensions and if so, how thick is the plywood that was used to build the box. In addition, how far back from the front edge of the enclosure is the baffle? I ask because we really need to know the actual depth of the inside of the box.

 

[Heyman]

No one can be much help until we know whether the port has a self extending back into the enclosure or not.

The area and volume of the port (hence our need to know the depth) along with the volume of the enclosure determine the frequency that it's tuned to.

Armed with the volume of the enclosure (Vb) and the tuning frequency of the enclosure (Fb), one can use a modeling program to see which driver or drivers are an appropriate match for the enclosure.

Are the dimensions that you originally posted outside dimensions and if so, how thick is the plywood that was used to build the box. In addition, how far back from the front edge of the enclosure is the baffle? I ask because we really need to know the actual depth of the inside of the box.

Ok! I'll try to go the the rehersalplace lateron today and do some messureing. The dimensions I gave earlier are the inside dimensions. I'll compliment with as much as I can...

 

[Heyman]

No one can be much help until we know whether the port has a self extending back into the enclosure or not.

OK I have done some messureing and I hope you get my illustrations.

First of all I have to say that all specifications are inside messures. The Plywood is 20 mm which are aprox 0.8"

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For another illustration I also stripped down the box and shot some pix.
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Hopefully you or someone else can tell me which element to shoose.

I use to shop at Thomann.de and they have very decent prices compared to the shops in Sweden...

http://www.thomann.de/gb/cat.html?gf=loudspeaker_18_inch&oa=pra

TNX in advance!!!

 

[Heyman]

One small error in the first pic is adjusted now!

 

[Brad T. Bass]

I realize this is on old thread. Don't know if your question was fully resolved. NOTHING wrong with your Speaker. What you have is an AC188L 18" Cerwin Vega. It was marketed in an Acoustic 301 Folded Horn Cabinet (70's vintage) and Yes it IS 3.2 Ohm. The Acoustic 370 Amp could Drive 2 of these Cabs @ 1.6 Ohms. I have the Original Manual on this Set-up. Should have lots of Kick if your amp can handle a load of that Impedance.