[dweekie]

Looks very nice! 

[jkelly]

Here are some photos of the project. The physical build and cosmetic stuff is about 99% complete. Now the real hard part starts with RTA and EQ tweaking on the Behringer. 

http://members.cox.net/brassear/emerald-physics-clones/

Wow - they really look great!

I have a couple of questions. 

Is the back of the waveguide covered with any material?

The foam plug - how do you determine the width of it.  I thought that maybe it fills
the whole horn but it looks like a lightbulb screwed into the mouth.

Does it go into the mouth of the waveguide?

Thanks and great work.

[Ric Schultz]

Looks great......however, any grill cloth will veil the sound and including on the woofs.  You absolutely must contrain layer damp the frames of the woofs....huge....humungus difference.  You really want to wire your amps directly to the drivers, so the cloth on the back should be gone too.  A single set of binding posts and the extra wire will veil the sound.   All these things I have tried.  You will probably need to delay the treble a slight bit.  The woofs take at least 200 hours of very hard playing to come into their own.  The surrounds and spider are very stiff.......so takes a while.  Have fun!

[BrassEar]

Is the back of the waveguide covered with any material?

Nope, stock DDS waveguide. These are strange in that the fronts are beautifully finished and the rears look like a child finished them.

The foam plug - how do you determine the width of it.  I thought that maybe it fills
the whole horn but it looks like a lightbulb screwed into the mouth.
Does it go into the mouth of the waveguide?

I just used spray adhesive to glue multiple layers together and then cut that 3-inch thick chunk in a circle. I then had to manually shave or cut it down to represent a funnel that fit inside the WG. It comes about a half inch in front of the throat. If you were not using a grille you could extend the foam out beyond the mouth of the waveguide. I believe Geddes does this on his speakers.  I don't think the foam plug dimensions are that critical as any foam in the WG would help as far as what I read on Earl's patent.

[BrassEar]

You absolutely must contrain layer damp the frames of the woofs....huge....humungus difference. 

Sorry Ric but I must be dense, can you elaborate on this? How do I constrain layer damp the frames of the woofers? Do you mean apply some damping compound to those cheapo stamped steel frames to stop them from ringing like telephones? 

You really want to wire your amps directly to the drivers, so the cloth on the back should be gone too. 

I wired some 14GA directly to the drivers and that cable will connect directly to the amps.

You will probably need to delay the treble a slight bit. 

The auto time align on the Behringer indicated 30 mm tweeter delay (.09 ms). Does that sound close?

Thanks for the suggestions! The next major step after getting these RTA'd and EQ'd will be to upgrade the Behr. I think I know who can do that for me!

[Ric Schultz]

Yes, apply a constranined layer damping material to the woofer frames.  Michael Percy sells EAR SD40AL.  This damping material has an aluminum layer on top.  You cut it to size with scissors and peel off the clear layer underneath and stick it on....self sticking.  Works incredibly.  Damp all the struts on each woofer.....way better sound.

Yes, that amount of delay sounds about right.  You can easily change it and listen.

I am glad you are hardwiring.....mucho good.

[fine]

 aa

[BrassEar]

Just a minor update here....

Please see Richard's "New Insights: Going beyond HiFi... "good" design and the "known" ~" thread (page 3) for my latest trials with these clones.  I just might go passive first order on these but I need a few weeks of pure listening to make that call.  The Behringer is an amazing device for the $$ but I now have more respect than ever for what Clayton has accomplished with this unit and his speakers. 

I don't like the sound of the DDS waveguide/B&C DE250 with high order slopes and just going for flat in-room response does not sound as natural as a simple coil and cap arrangement here. What is truly shocking is how flat the first order setup actually measures in room with TrueRTA.

[ecir38]

Here's the link

http://www.audiocircle.com/index.php?topic=56536.msg559905#msg559905

Look forward to hearing more about this when the time comes.

BR

[gainphile2]

Holy cow the universe have aligned  . While awaiting for AUD to strengthen so I can get reasonable price for seleniums I have... run the Eminence Alpha FULL RANGE for about a month. I since had no desire to pursue cloning the CS2 it sounds so real, so good. The high is simple dome tweeter. I reserved the lower part for additional Alpha but don't need them and also not keen to lower the acoustic center.




I still pass it through active XO for the bass compensation and notice no sound degradation. This is measurement from *listening position*, in-room. Ignore the SPL level I did not calibrate them.

[scorpion]

Gainphile2,

Your measurements conform quite a bit to what I has measured for th Alphas fullrange, the build up at 2 kHz may or may not exsist and I think it is much milder than official FR measurements show. I  also listened to the Alpha fullrange but placed much near the floor and I liked what I heard but didn't go further. Are these speakers better than your Plutos ? Then this is really interesting. What are your panel and mounting measures ? I do would like to run a simulation of your setup ! Where is the tweeter coming in ?

/Erling

[BrassEar]

I still pass it through active XO for the bass compensation and notice no sound degradation. This is measurement from *listening position*, in-room. Ignore the SPL level I did not calibrate them.

Gainphile2 - what active XO are you using? I am surprised that they sound that good being so close to the rear wall. I have mine about 3 feet from the rear wall and they sound spacious and very clean.

Maybe we should start a new "Full Range Alpha" Circle. This is one amazing driver. Thanks for sharing.  BTW, I still think two are better than one.

[scorpion]

Gainphile2,

In fact, you won't be sacrifacing anything by taking in a lower Alpha. Just let this go bass only and you will not be needing any bass lift.
I can say this for my ongoing project is 2 Alphas on a 40 cm wide baffle, flat down to 40 Hz + some other drivers, no EQ. More detail later.

/Erling

[gainphile2]

Gainphile2,

Your measurements conform quite a bit to what I has measured for th Alphas fullrange, the build up at 2 kHz may or may not exsist and I think it is much milder than official FR measurements show. I  also listened to the Alpha fullrange but placed much near the floor and I liked what I heard but didn't go further. Are these speakers better than your Plutos ? Then this is really interesting. What are your panel and mounting measures ? I do would like to run a simulation of your setup ! Where is the tweeter coming in ?

/Erling

The 2k peak does appear if I measure *nearfield* so I had played around with notch filter to smooth it out. But then they don't sound "right". Only after I read this maniac at Lampizator.eu I got the "awakening".  Basically he said never to measure nearfield or 1m etc. as then they will sound like your typical showroom speakers. Measure only at listening position as then the room is accounted for! What a genius.

My guess is at listening position the 2k peak is already well-diffused by the room it became irrelevant.

[gainphile2]

I still pass it through active XO for the bass compensation and notice no sound degradation. This is measurement from *listening position*, in-room. Ignore the SPL level I did not calibrate them.

Gainphile2 - what active XO are you using? I am surprised that they sound that good being so close to the rear wall. I have mine about 3 feet from the rear wall and they sound spacious and very clean.

Maybe we should start a new "Full Range Alpha" Circle. This is one amazing driver. Thanks for sharing.  BTW, I still think two are better than one.

The XO is simple lowpass-shelving as per SL's site. One op-amp. I forgot what the frequencies were I think it was 250Hz - 11Hz. but will try to re-document and post here. It was one of those experiement which bound to "fail" so I did no documentation. If you look at my site gainphile.blogspot.com I usually document things very thoroughly. What a turn of event though   .

That picture was quite old and yes - too close to the wall. The final distance from the wall is now 85cm (inside) and 90cm (outside) so they're bit toed-in. The soundstage is best if they are simply parallel to the wall but then I would be listening to the tweeters off-axis.

[gainphile2]

Are these speakers better than your Plutos ? Then this is really interesting. What are your panel and mounting measures ? I do would like to run a simulation of your setup ! Where is the tweeter coming in ?
/Erling

In short: Yes. But the Pluto have their own quality. With such large panel sometimes I have the impression that the "Stage" is blocked by these panel. Something like looking at a concert but then you have 2 people standing in front of you. It's a weird sensation how these OBs fool your brain. With the Pluto this sensation do not exist thus I felt "the concert" is all for myself.

Where the Pluto fails: Bass quality and sensitivity.

The baffle is 45cm x 112cm. Woofer at 63cm and Tweeter 91cm. I forgot what Tweeter freq. is but it's 3.3uF parralel with 2.2uF + L .56mH  (2nd order).

[scorpion]

gainphile2,

Here are two simulations of your Alpha15 baffle. 1st as is is now:



2nd with a second Alpha lower crossed LP at 300 Hz , 12dB/octave:



No EQ in any case.

/Erling

[richidoo]

Looks like those FR simulation graphs were created with Quarter-Wave software, created by AC'er Martin King. 

[gainphile2]

Wow that's a good program (MJK I suppose)?  It seems that my eq can do the same as the additional Alpha with no eq but they both roll off rather quickly below 40Hz which is Fs. I wonder now if they can be pushed towards high 20s when a pair is used  aa

I ran a test of harmonics distortion and 30Hz is still reasonable but 20Hz is not. At 20Hz I can hear tones whare there should be silence. I'm wondering how CS2 can obtain -3dB at 20Hz.

At 40Hz:



At 30Hz:



At 20Hz:

[scorpion]

Of course it's MJK's MathCad models, the best software we have for these simulations. MJK himself has published a lot of Alpha simus so I don't think he will mind.
Two woofers will certainly help bass but this 20 Hz figure is a bit in the blue, it will never be put to test in reality. Two woofers will help lowbass powerhandling and contribute to extension.

What SPL level is your Spectrum measurement ? 40 Hz looks quite reasonable, 2nd harmonic a bit below 10% and 3rd well below 3% distortion perhaps as low as 1%. 30 Hz is alright too I think although 3rd harmonic is equal to the 2nd. Now think what 2 units and no EQ will do ! 

/Erling