Electro-Voice woofers in LaScala??

[Shock-Late]

Does someone know if I could use my Electro-Voice woofers (EVM15L) in my scalas?

For the moment they use Tesla woofers. But I have EV woofers in my DIY klipschorns; Bruce edgar recommended their use for a klipschorn enclosure, but I don't know if they would work in LaScala.

I don't want to try if i'm not sure it could give some good results, because I'm always afraid to break something, specially the holes for the screws. (even if plywood is more solid than MDF.)

Anyone ever tried EV woofers in LaScalas?

Thanks!

Frans

[djk]

djk

Fast Newbie

Posts: 66

From:cedar rapids, ia, usa

Registered: Sep 2000

posted 12-12-2000 03:47 AM

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The K43 will have quite a bit less bass below 70hz than the K33 in a stock Belle.This is due to the lower Qts.The lower Qts will also cause the Belle to have more output above 200hz.While I have converted many LaScala to the K43 and vented them to 31hz I have not done so with the Belle.It might be easier to do this to a Belle as there is more room for the woofer frame. http://www.audioasylum.com/forums/HUG/messages/4664.html you can go backwards to the root and read the whole thread.

To use an EV15L make new tops the same size as a home LaScala, 2' x 2' x 1'.Since yours have a bunch of holes from the piezo tweeters you were going to have to do something anyway.Port the new box out the back with two 4" dia 5.5" long ports.This back must be removable.Remove the bottom door from the bass cabinet and turn it up side down.Bolt the new top on.The new top must have an opening that matches up with the opening in the bass cabinet.Change the woofer inductor to 5mH.Use a 38hz two pole high pass filter with a Q of two in front of the power amp.This will be maximally flat with an F3=38hz and the woofer matched in level with the other drivers with an Rg=1R5 Rg is the sum of the DRC of the woofer inductor,speaker wire,and amplifier output impedance.If the woofer inductor is an air core type of 18~20 gauge you will be ok.If you buy an expensive large gauge inductor you will just have to put a resistor in series with it.One sheet of 4' x 8' will make two tops.The screw holes for the woofer have metal insert threads and are size 10-32 (SAE).

[Shock-Late]

Thanks for your answer, djk!

I'm afraid, however, that it is a bit too complicated for me. I'm sure it works perfectly but for now I don't wanna make enclosure changes, even less if there are changes to make in the crossover (I don't know anything about cross-overs. I wouldn't even be able to recognize the woofer inductor you told me i should replace!). Maybe later, when I'll be a bit more experimented, I'll try this mod cause it sounds interesting.

What do you mean by "a high-pass filter of 38Hz in front of the Power-amp"?

And if I used my EV without adding mods, would it work the same as K33 or less good?

I apologize to be as dumb, but all this is quite new for me ;-).

Many thanks!

frans

[djk]

Nobody is as helpless as you claim to be! Follow the input of the crossover to the woofer.It only goes through one part.That is the one you change.A 38hz filter is a 38hz filter.It is just another black box.You probably have black boxes called cd player,preamp,and power amp.The black box called 38hz filter can go anywhere in front of the power amp black box.That means it could go between the cd box and the preamp box or between the preamp box and the power amp box.It is not rocket science.There are no enclosure changes.You are making a simple six sided box the same size as the original home LaScala top.Take out the parts from your beat up tops that have extra holes from the piezos and install them in the new tops.The really,really hard part is remembering to install a pair of ports in the back of the new tops.Any lumberyard can cut the boards and the PVC pipe for the ports for you.A sheet of plywood is $30.The parts for the 38hz filter about the same.A pair of 5mH about $15.Or you could spend for a pair of K33E.The EV15L with the mods will sound better than the K33E.If you don't do the mods the K33E will sound better.I think you said the pair of K33E will cost $1000 locally?

[Shock-Late]

OK OK now it already looks quite simpler ;-). But what i was wondering about the 38Hz filter is WHY do I need it? Is that to prevent the woofer to "flap" because of the ported enclosure, and so reducing the risk for him to hit the mounting board? What about using a second gasket to keep it slightly furter from the board? Because I spent a lot of time to get the amp that would have the simplest path from input to output, and thus the more transparent sound, and I'm also using a (reasonably) "expensive" interconnect for the same reason. Maybe it would be a shame to use any active or passive filter in the path....(but correct me if I'm wrong).

What would happen without the 38Hz HP filter?

Also, don't yo loose the advantages of horn-loading (no distortion, no "slow bass",...) when you port the enclosure?

And last but not least, why do you change the woofer inductor? Is that because of the different specs of the EV15L, or because of the ported enclosure?

I think I'll keep my EV15L to try this mod, anyway. Sounds tempting to get deeper bass.

many thanks, djk, for helping me becoming less dumb ;-))

Frans

[Shock-Late]

I opened my scalas once again and this time I understood why I got a shy bass. I took one tesla woofer out to examine it closer. And it happens it has the same look as a JBL D130, you know with the extra-hard edge, exponential cone profil and aluminium dust caps. It's apparently a model desiged to be used as wide-bandwith loudspeaker, but with a very short bass just as the JBL D130. Don't know who had the stupid idea to use it in a bass horn....That said, these speakers are superb and I think I'll sell them for a good price, as they're in very good condition.

Then I thought "there's no reason my EV work worse" and after fitting one in my Scala it appea rs to give more bass, even without mods...it's not fabulous, but already a lot better. At least I hear some bass now. I'll be able to listen to some music while I build the modified tops .

[djk]

>>Shock-Late OK OK now it already looks quite simpler ;-). But what i was wondering about the 38Hz filter is WHY do I need it? Is that to prevent the woofer to "flap" because of the ported enclosure, and so reducing the risk for him to hit the mounting board? What about using a second gasket to keep it slightly furter from the board?<< djk: The Qts of the EV15L is so low it is not flat.The filter makes it flat and is carefully calculated to do so.B&W uses this same type of filter in their 800, 801,802,808 series loudspeakers as does Thiel in the 3.5 and EV in their Sentry III studio monitor and their Interface A,D,and others.The filter also protects the speaker from subsonic frequencies.And a second gasket should be fitted to the EV15L. >>Because I spent a lot of time to get the amp that would have the simplest path from input to output, and thus the more transparent sound, and I'm also using a (reasonably) "expensive" interconnect for the same reason. Maybe it would be a shame to use any active or passive filter in the path....(but correct me if I'm wrong).<< djk:The filter can be implemented in most power amps by changing the value of the input coupling cap and adding one other passive part.Or changing the output coupling cap in your cd player and adding one other passive part.Simple and transparent.>>What would happen without the 38Hz HP filter?<< djk: Less bass,more phase shift.When you correct the frequency response to flat you also reduce phase shift at the same time.>>

Also, don't yo loose the advantages of horn-loading (no distortion, no "slow bass",...) when you port the enclosure?<< djk: The LaScala is a 100hz horn.Actually they are direct radiators with help from horn loading.Its performance as a horn above 100hz is not impaired.>>And last but not least, why do you change the woofer inductor? Is that because of the different specs of the EV15L, or because of the ported enclosure?<< djk: Three reasons.The network is set up for a K33E which has a 4 ohm voice coil and the EV15L is 8 ohms.The EV15L is too loud.The resistor raises the Qes to work right in this design.>>I think I'll keep my EV15L to try this mod, anyway. Sounds tempting to get deeper bass. many thanks, djk, for helping me becoming less dumb ;-))Frans

Shock-Late: I opened my scalas once again and this time I understood why I got a shy bass. I took one tesla woofer out to examine it closer. And it happens it has the same look as a JBL D130, you know with the extra-hard edge, exponential cone profil and aluminium dust caps. It's apparently a model desiged to be used as wide-bandwith loudspeaker, but with a very short bass just as the JBL D130. Don't know who had the stupid idea to use it in a bass horn....<< djk: It sounds like they would work well in a real bass horn. http://home.att.net/~lkalin/ Michael is standing in front of a real 40hz bass horn.This is an RCA Olson bin.Sometimes called a Shearer horn.The 300hz 3x6 multicell high frequency horn on top has a larger mouth than a LaScala does.I used to own a pair of these.The bottoms are 80" tall and 80" wide. http://www.audioheritage.org/products/lansing/shearer_horn.htm >>That said, these speakers are superb and I think I'll sell them for a good price, as they're in very good condition.

Then I thought "there's no reason my EV work worse" and after fitting one in my Scala it appea rs to give more bass, even without mods...it's not fabulous, but already a lot better. At least I hear some bass now. I'll be able to listen to some music while I build the modified tops .<< djk: Good for you! Please fit a second gasket to the EV15L soon.

[John Warren]

Shocklate-Looking at the RCA unit, a 40Hz horn radiating in free space needs 62 sq. ft mouth, positioned at center of floor requires a 31 sq. ft., flat against a wall needs 15 sq. ft and in corner a 7.5 sq. ft. The horn pictured has a mouth area of 44 sq. ft. so maybe designed for floor placement(?).

I don't know LaScala dimensions but the mouth looks like 2x1.5'=4.5 sq. ft. so positioning it against the wall gives you a 70-75Hz horn cut-off. Needs bass augmentation. The original application was for PA so bass output was not considered a primary design goal.

[Shock-Late]

Thanks (once again) for your help djk!

I'm quite amazed the K33E has a 4Ohms coil (I always thought it was 8 Ohms, just has so many high efficiency speakers, or even 16...

My x-overs are of the vintage AA type, thus designed for the K33, not K33E. Was the K33 4 ohms too??

And considering my woofers are 8 ohms, what's the actual cut-off frequency with the AA network? If it's 800Hz it's quite OK for a short time, but if it's 200Hz I'll install new inductors for the woofers tomorrow morning!! I hate to know there might be a "hole" in the sound....gasp!!!!

[djk]

>>John Warren :Shocklate-Looking at the RCA unit, a 40Hz horn radiating in free space needs 62 sq. ft mouth, positioned at center of floor requires a 31 sq. ft., flat against a wall needs 15 sq. ft and in corner a 7.5 sq. ft. The horn pictured has a mouth area of 44 sq. ft. so maybe designed for floor placement(?).<< djk: In a theater behind the screen they usually had wings installed to the sides.Otherwise they sat on the floor.Bruce Edgar used to have a pair of these too.I have a picture of Bob Heil doing sound for the WHO with only two of these per side,a dozen 4560,two dozen HF horns that look like fiberglass 511B,and only two pair of EV T35.>>Shock-Late: I'm quite amazed the K33E has a 4Ohms coil (I always thought it was 8 Ohms, just has so many high efficiency speakers, or even 16...

My x-overs are of the vintage AA type, thus designed for the K33, not K33E. Was the K33 4 ohms too??

And considering my woofers are 8 ohms, what's the actual cut-off frequency with the AA network? If it's 800Hz it's quite OK for a short time, but if it's 200Hz I'll install new inductors for the woofers tomorrow morning!! I hate to know there might be a "hole" in the sound....gasp!!!!<< djk: All the K33 for the AA network were 4 ohms.The minimum impedance is actually about 5.5 ohms around 250hz.Many times you will find they work ok on the 8 ohm tap.When you change the woofer inductor to 5mH with the EV15L the midrange will sound smoother and you will get a little better bass.It is not a big deal but it is something you want to do.