Crossover options for Econowave type project

My vintage EV speaker project is starting to look similar to an Econowave, which is really a fabulous idea. I need help with crossover issues in order to take the next step.

This is a 1966 vintage speaker, 3.7cf, beautiful solid cabinet. A great Econowave type candidate. I am starting to really like the sound of the woofer, but want to ditch the horn and crossover, because it is horrible. The speaker has a 12" Alnico fullrange woofer, 100 db/1w. It is supposedly 16 ohm, but I've read that they are often more like 12-13. It crosses to the midrange horn at 800 hz. I assume that is also 16 ohm, but I don't know for sure. The crossover is potted in tar.

Before tearing the speaker apart, I want to ascertain if the crossover is bad, the horn, or both. I propose to buy either an inexpensive waveguide like the B52 closeout at Parts Express #299-2303, or use a pair of JBL 2344a and JBL 2425 drivers I have sitting on the shelf. I don't want to use the JBL long term, because they are worth a lot more in the resale market than many good, but cheap horns. This speaker is going to remain in my workshop in the basement.

I don't build crossovers, and am looking at just buying something like a PRV or Eminence from Parts Express to get this thing playing, and then take the next step. Almost all of those type crossovers are 4 or 8 ohm, and the effective crossover point would change with the existing drivers. How can I make this work in this situation? Would I be better off using an active crossover? I do have a TDM stereo 3 way, balanced. Does an active crossover compensate for differences in impedance?

I've also considered buying a 5" or 6" coned pro mid such as Faital, BMS, etc, and use it with a horn tweeter up around 5-6khz, but the same issues apply in that scenario too.

Somebody please offer some advice. Thanks!
 

AllenB

Moderator
Paid Member
2008-10-18 11:31 am
Your 16 ohm woofer may measure 12-13 ohms of resistance, but an 8 ohm woofer would measure half that as well so there is no surprise.

There is no problem crossing different nominal impedances. They are dealt with individually anyway. If you are looking to cut corners, active will increase the ability to tweak more in a shorter time, but such a technique reaches the same natural limits whether passive or active. So it depends on what you have around, and where you want to stake your learning curves.
 
Typically a 12" woofer is crossed to a 1" compression driver + horn around 1,100 - 1,200Hz, since at that frequency the 12" diameter cone has a polar pattern(JBL 2206 example) which closely matches the polar pattern of the horn for a smooth transition. The B52 Parts Express #299-2303 horn has a 90H x 40V directivity pattern, which matches the 12" JBL 2206 example 90 degree beaming around 1,150 Hz.

I would first listen to and also measure the SPL vs. Freq of JUST the 12" midbass. If it sounds good you will want to make a good horn + crossover investment. If it sounds icky.... then you have a nice cabinet to use on a PROVEN 2-way design.

If you like the midbass, I would want to first experiment with the "baby butt cheeks" pair of JBL 2344a and JBL 2425 drivers. Low cost. "Artistic" shape. Unique sound. You might keep them.

============
A good low cost 8-ohm compression driver: $61 Peerless by Tymphany DFM-2544R00-08 1" Compression DFM Driver 8 Ohm. I like this CD for both the sound quality and simple crossover circuit.

Modest Cost------16 ohm
B&C DE250-16 1" Polyimide Compression Driver 16 Ohm 2/3-Bolt $107

High Cost-------16 ohm
1st choice: The Faital HF10AK 1" exit compression driver can be used low for home use, and it is available in 16-ohms. Easy crossover ckt.

2nd choice: The BMS 4550 1" exit compression driver can be used low and is available in 16-ohms. Robust!
 

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Econowave candidate?

Your 16 ohm woofer may measure 12-13 ohms of resistance, but an 8 ohm woofer would measure half that as well so there is no surprise.

There is no problem crossing different nominal impedances. They are dealt with individually anyway. If you are looking to cut corners, active will increase the ability to tweak more in a shorter time, but such a technique reaches the same natural limits whether passive or active. So it depends on what you have around, and where you want to stake your learning curves.

AllenB: Thank you for your comment. Where I would like to take my learning curve is to be able to build proper crossovers for unique applications. For example, for my own living room application, garage system, a friends bar stereo, etc. At this time, what I have on hand are JBL 2344a and 2404H butt cheeks, TAD 1201 midbass, TDM crossover, a couple DIYSOUNDGROUP 15" Eminence buyout subs, and lots of amplifiers. All XLR connections. No testing software or knowledge on that subject. I do have lots of hardware like barrier strips, terminal blocks, shrink tubing, wire. etc. No passive crossover components, because I'm stymied in that area.

I really like these vintage speakers, because they are built really well cabinet-wise, I got them super cheap, and they look very appropriate in our vintage home, although they are in my workshop now. More info on my answer to LineSource. Thanks!
 
Econowave candidate?

Typically a 12" woofer is crossed to a 1" compression driver + horn around 1,100 - 1,200Hz, since at that frequency the 12" diameter cone has a polar pattern(JBL 2206 example) which closely matches the polar pattern of the horn for a smooth transition. The B52 Parts Express #299-2303 horn has a 90H x 40V directivity pattern, which matches the 12" JBL 2206 example 90 degree beaming around 1,150 Hz.

I would first listen to and also measure the SPL vs. Freq of JUST the 12" midbass. If it sounds good you will want to make a good horn + crossover investment. If it sounds icky.... then you have a nice cabinet to use on a PROVEN 2-way design.

If you like the midbass, I would want to first experiment with the "baby butt cheeks" pair of JBL 2344a and JBL 2425 drivers. Low cost. "Artistic" shape. Unique sound. You might keep them.

============
A good low cost 8-ohm compression driver: $61 Peerless by Tymphany DFM-2544R00-08 1" Compression DFM Driver 8 Ohm. I like this CD for both the sound quality and simple crossover circuit.

Modest Cost------16 ohm
B&C DE250-16 1" Polyimide Compression Driver 16 Ohm 2/3-Bolt $107

High Cost-------16 ohm
1st choice: The Faital HF10AK 1" exit compression driver can be used low for home use, and it is available in 16-ohms. Easy crossover ckt.

2nd choice: The BMS 4550 1" exit compression driver can be used low and is available in 16-ohms. Robust!


LineSource: Your comments are very much appreciated, and are right on the money for where I want to take this project. THANKS FOR YOUR SUGGESTIONS. I think that Zilch's work on Econowave was really a fabulous idea, and has benefited a lot of people. Also, guys like Wayne Parham making really great, affordable products. Both of the high efficiency variety.

So here it is: I've heard JBL 2206 with 2344a, 2404h. Sounds great. I like that horn. I've also heard it with a 15, and 18" JBL woofer, 2206, and 2404H. Better sound! Then I stumbled onto these EV Marquis in perfect shape for $200. And, a separate EV Regent cabinet with 15", $35. I've grown to like the sound of that SP12 woofer, but it does not play low...down to about 55hz. I can augment the bottom end. Was thinking of turning the Regent cabinet into a sub with 1-2 modern (15") in it.

I'll do as you say, and listen to just the SP12. It is supposedly pretty solid out to 8khz, according to the EV guys over on AudioKarma. Can easily add the 2344A. A third option would be to make a simple mock-up of plywood and use both the 2344a and 2404h. I have the active crossover to do that, and plenty of amp channels. If the SP12 is solid out to 7/8khz, then the 2404H crossed at about 5.5khz might be nice. Efficiency is the same as the woofer. I cannot understand why EV used them wide-range, but in my case crossed at 800hz to this horrible mid-horn. (Bad crossover?)

In the end, I'd want to end up with the Marquis as a single box, similar to the Econowave, with a passive crossover. By the way, the Marquis comes set up to accept either a 12" or 15" woofer, so I have lots of options. I want a high efficiency solution, but it does not have to be compression drivers.


Would you reply to these ideas? Thanks again.
 
Econowave candidate?

scale the frequency....

Turk:

Just discovered something interesting/confusing about these SP12. I thought the SP12 was a wide range woofer, and the SP12B was a coax. They are both listed as "twin cone", the EV name for coaxial. Also called Radax coaxial. They show a "mechanical crossover" at 4000 or 4400 hz. First off, I don't know what a mechanical crossover is. EV shows the SP12 running up to 13000 cps. Some people quote 17,000cps.

Why on Earth would a coax have a separate mid horn crossing at 825hz? And, the ability to add on a horn tweeter crossed at 3600?

I found this on another site: "Other than the aforementioned woofer gap problem... I don't know what else would be "out of spec" if the crossover and pad are passing signal and the tweeter's working.

I've gotta say that, based on the description in the previous post, it sounds to me as though the tweeter is not working -- it can be hard to tell on a coaxial driver... but the EV coaxes just don't sound 'right' when the tweeter's not working. I've got a couple of 'em here in just that state :p

Now, having said that - it is possible to drive the woofer (well, woofer and whizzer "midrange" cone) and the tweeter separately (i.e., bypass the crossover - or at least work partially around it). If you haven't done so, you might want to investigate the drivers separately."

So, like LineSource said, listen to the woofer by itself. I have not been able to remove the woofer yet, as it is back-mounted so you cannot see the front of the driver. I'll have to do that, and see what can be done about the "Twin Cone". EV states that this driver works really well in open baffle, in 15 cf or more. That could be a GREAT solution for my other listening area, where I wanted to mount something in the wall anyway.

This is shaping up to be fun......
 
Econowave candidate?

A twin cone is not a coax. It has two parts to the cone, they are glued together and only operate independently by bending. This is a compromise toward a full range driver.

If I were you I'd ignore this for now.

Allen: This is very confusing, partially because there seems to be a lot of misunderstanding in the vintage/high efficiency arena. People on an EV site refer to Twin Cone, but I'm not sure that they were not making a mistake either.

Based on LineSource's recommendation, as a first, quick test, I just fastened a piece of Styrofoam over-top the mid horn, to listen more closely to the woofer. (The next step will be open the speaker, and disconnect the mid) Even so, I noticed that the mid is quite a bit louder than the "coax" SP12. These speakers often had L pads, but mine don't, and the holes appear to have a factory plug in them.

I also shut off the lighting, and used a flashlight to peer through the grille cloth. There is indeed another cone mounted coaxially. The right speaker seems to have more high frequency content than the left one.

People on the AK site talk about repairing the "Whizzer" in the SP12, so that remains to be determined.

I'm going to rig up that JBL 2344a and give it a go. But, I'd like to ascertain exactly what is what with that "coax", and what a "mechanical crossover" is.
 
LISTEN and MEASURE
LISTEN and MEASURE

The ElectroVoice SP12 has a paper WIZZER CONE to mechanically extend the frequency response to around 6kHz with a ragged SPL. This is why you want to keep the woofer in the final (ported)cabinet with a full front baffle and critically listen to both test tones and music to decide on the best crossover point. Personally, I would use a BW3 circuit crossover at 1,200Hz to a 1" horn(compression driver)... ignore the wizzer extension. BUT, for garage use, you might enjoy the simplicity of running JUST the SP12 full range in your ported cabinet. A third option is to add a super tweeter at 6kHz, which is not my favorite because of the high efficiency of he SP12.

I CONFESS...I CONFESS... in the past I have carefully cut the wizzer cone off of a few drivers.
---------
To obtain the Frequency-Response-Data(FRD) and Impedance-Measurement (ZMA) you want to keep the woofer in the final (ported)cabinet with a full front baffle. You might be able to simplify your work by modifying the front baffle to brace and support the woofer, and also support two different upper baffle sections for the JBL 2344a and #299-2303. You want options.

If your cabinet is at least 14.2" wide, you should be able to design separate upper baffles for these two horns.

JBL 2344a "baby butt cheeks" horn
100x100 polar pattern from 1kHz to 16kHz
H=12.6"
W=12.6"
D=6.5"

B52 Parts Express #299-2303 constant directivity horn
90x40 polar pattern from 1kHz to 18kHz
H=10.1"
W=14.2"
D=5.5"
 

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Econowave candidate?

LISTEN and MEASURE
LISTEN and MEASURE

The ElectroVoice SP12 has a paper WIZZER CONE to mechanically extend the frequency response to around 6kHz with a ragged SPL. This is why you want to keep the woofer in the final (ported)cabinet with a full front baffle and critically listen to both test tones and music to decide on the best crossover point. Personally, I would use a BW3 circuit crossover at 1,200Hz to a 1" horn(compression driver)... ignore the wizzer extension. BUT, for garage use, you might enjoy the simplicity of running JUST the SP12 full range in your ported cabinet. A third option is to add a super tweeter at 6kHz, which is not my favorite because of the high efficiency of he SP12.

I CONFESS...I CONFESS... in the past I have carefully cut the wizzer cone off of a few drivers.
---------
To obtain the Frequency-Response-Data(FRD) and Impedance-Measurement (ZMA) you want to keep the woofer in the final (ported)cabinet with a full front baffle. You might be able to simplify your work by modifying the front baffle to brace and support the woofer, and also support two different upper baffle sections for the JBL 2344a and #299-2303. You want options.

If your cabinet is at least 14.2" wide, you should be able to design separate upper baffles for these two horns.

JBL 2344a "baby butt cheeks" horn
100x100 polar pattern from 1kHz to 16kHz
H=12.6"
W=12.6"
D=6.5"

B52 Parts Express #299-2303 constant directivity horn
90x40 polar pattern from 1kHz to 18kHz
H=10.1"
W=14.2"
D=5.5"

LineSource: Could you suggest a simple test set-up for me to acquire? I need to learn how to do that.

I read up on whizzers yesterday. Very interesting. I always thought they were a coax driver. I find it odd that in this Marquis speaker, they have a twin cone woofer on the very bottom of the 32" speaker, and a mid horn at the very top. For testing, I think I'll flip them upside down, and move the 3" riser to the opposite end. I can more easily set a test baffle on the top, rather than trying to build the JBL 2344a into the box. At 3.7 cf, they are already pretty small for that woofer. Hence the limited bass extension.

I'll build 2 plywood test baffles so I don't ruin the original grill cloth and metal work. One will be for a 12" woofer, one for a 15". I can play with the 2344a, the B52, and also my 2404H butt cheeks that match the 100 x 100 degrees of the bi-radial JBL's. RobH kindly provided me previously with the circuit to compensate for the falling response of the 2344a, but just for initial testing, I'll use the one in my active crossover.

My workshop is in a newly built room, 500 square feet, 9' clear span ceilings with no duct work. (radiant heat, mini-split a/c) I built it myself, obviously. Very quiet. I move around while in the room, and rarely sit.

Thanks!