[mcgsxr]

I would PM this, but a number of folks might be interested in the answer, so I figured I would post instead.

Now, it is ENTIRELY possible that this info is already posted, and I just missed it in my scanning the threads here, and your site.

Could you share with us, a ballpark for the expected efficiency of the KIT41, and KIT61?

I am considering pairing the KIT41 with a lower powered amp, and would like some indication of how that may or may not work, before I go ahead and give it a listen to be sure.

[Kevin P]

Good question and one that I try to avoid.  

None of the new designs are efficient by traditional measurement standards.   The KIT41 & KIT61 come in around 85-86db/1W/1M averaged across their usable bandwidth.   The KIT261 & LCR are around 87-88db/1W/1M measured in the same way.  

I think that traditional efficiency ratings are a poor method of determining what type of amplifier you need for a given loudspeaker.   For one, companies really stretch these numbers.   They choose somewhere nice on the FR curve to pick their efficiency rating.   I'd rather see the entire bandwidth averaged.   The low frequency portion of a loudspeaker is what limits you.  The baffle step usually occurs around 500HZ and under that you end up with an in-room 2-3db loss.    You can either compensate for it electronically or in the acoustic design of the speaker/box system.   Either way you end up throwing away efficiency at 1Khz where most efficiency measurements are stated.    

None of this is useful in determining what kind of amp to use for a given speaker.   It doesn't tell you anything about the impedance curve and it doesn't say anything about how the loudspeaker will perform with more than 1W of power.   All of the XBL^2 drivers compress much less under power so they don't sound like an inefficient monitor.   Trust me... I've got a pair of 106db efficient horns and I've listened to a lot of inefficient monitors.    The differences are astounding.  

Due to the lack of compression under power the efficiency at higher power levels looks much better than a traditional loudspeaker.   That isn’t reflected in the 1W/1M measurement.  Look at efficiency ratings of most loudspeakers under 5-10W of power and you will see that efficiency-ratings plummet.   T/S parameters change up to 20% under power.   Most of this is due to driver non-linearities where the BL of the driver is changing due to the VC leaving the gap.   Some of it is due to heating of the VC increasing DCR of the voice coil.   Some of it is due to suspension non-linearities as the cone moves.    The typical 1W/1M measurement and T/S parameters tell you nothing about how the system reacts under load.

Rather than quoting numbers that don’t reflect anything meaningful, we have decided to publish detailed impedance curves and recommendations for minimum power.   The impedance curve is determined by the total system design, crossover + cabinet/driver so it tells you a lot about how easy/difficult a load the loudspeaker is to drive.   The second thing we do is recommend minimum power levels.   Any of the kits will run to their maximum SPL capabilities with 40-50W of power.   I use a LM4780 based chip amp that delivers about 40W to test all of them.   It provides more than enough headroom.

As a side note, I took a KIT41 over to Dan Schmalle's of Bottlehead.   None of the SET amplifiers had enough power to drive them to levels I'd consider acceptable.   They need more than 8W of Single ended triode to be happy.       Tube amps will work wonderfully as long as you use larger powered tube amps that typically have 30W & over.   I've tried a couple Push Pull EL-34 based amps and they work wonderfully.

Wow.... I'm full of wind!   Look at that answer!  

[kfr01]

Just to back Kevin's statement up... I'm a happy owner of the Kit61 and have noticed the exact behavior he describes.

Yes, their 1w/1m efficiency is on the low end.  I was worried this would be an issue when I initally hooked the kit up to my very small and very old sony amplifier for crossover testing before soldering.  My worry began for no other reason than it was noticable how much further I had to turn the volume knob.  

However, this worry completely melted away once I started playing the kit, and especially when I show it off.  They really do not suffer from compression at all after you get more than 1w pumping to them.  Throw more power to them?  They just keep getting louder.  I've never once heard them or the amplifier sound strained before my ears told me to turn them down in my moderately sized room.  My main integra amplifier has watt meters on it.  I've only once seen the needle stay near 30w.  This was when we were experimenting and were really trying to show off what the drivers could do.  It should be noted that this volume level was uncomfortable.  Normally the meters are bouncing around between 1 and 15w at room-filling and comfortable volume levels.  

Also, it should be noted that even at very low wattage "night volume" levels, the sound is very complete.  Exodus/Adire really did get the crossover right.  The speaker is still balanced from bass to midbass to midrange to highs even at low volume levels.  MANY speakers I've auditioned drop the bass and midbass at "night time" volume levels.  You don't need to turn these speakers up loud to gain their considerable benefit of complete sound.

Anyway, to sum up, if you have anything over 20wpc and a moderately sized room I wouldn't hesitate buying any xbl kit.  Kevin's statements regarding little compression are dead on.

[JoshK]

Nice honest answer Kevin!  I agree w/basically everything you said.  Efficiency is overrated unless you are using SETs but those are a different ballgame altogether.  

I read somewhere that midrange sensitivity of these drivers was low but when BSC comes into play they are more like 86db/w sensitivity speakers, iirc.  Even still, most 2-way speakers aren't going to be much above that.  Those who are honest about their monitors (Ellis Audio comes to mind too) state sensitivity near this mark.

[Kevin P]

Just to back Kevin's statement up... I'm a happy owner of the Kit61 and have noticed the exact behavior he describes.

Yes, their 1w/1m efficiency is on the low end.  I was worried this would be an issue when I initally hooked the kit up to my very small and very old sony amplifier for crossover testing before soldering.  My worry began for no other reason than it was noticable how much further I had to turn the volume knob.  

However, this worry completely melted away once I started playing the kit,  ...

Karl,

I appreciate your willingness to step up tell about your experiences with the speakers.   It really helps us at this stage to get the word out about the product.   Most people will discount my opinions for obvious reason.   It's the nature of the beast that most people buy what has gotten good reviews, either in the press or from other people they respect.   It's a chicken or the egg type of syndrome.  

I'm rarely stoked up about a product unless it offers something truly exceptional or innovative.   There are not many true innovations out there.   Just go to CES a couple years in a row and you will see the same designs, same hype and the same lack of real innovation.  

I've been stoked up about XBL^2 and it's potential in midrange drivers every since a demo we had at a speaker design conference a couple years ago.   It's an improvement in basic driver design without a doubt.   Nobody who has heard the Beta 10CX demonstration has walked away unimpressed.   That includes some of the largest OEMs in the world.  

I feel pretty lucky to have the chance to bring products to market ahead of the rest of the crowd.   We are an unknown player in the loudspeaker market and I’m not known as Mr. Loudspeaker.   That is an obstacle we have to overcome and input from people like you are exactly what we need.   Thank you…

[mcgsxr]

Kevin, thanks for taking the time to reply to my question - I wasn't trolling, I swear!

I own a set of the WR125's, and really like them - thanks to your PM, I reached Bob at CSS yesterday, and have ordered the balance of the KIT41.

I asked about efficiency mostly out of curiousity, since with my 30wpc Teac, I am able to achieve any volume I need, so I wanted to learn a little more about the specs - also, to your credit, this information is listed in the assembly plans for the kit.

I have managed to bottom out the WR125's, but only through seeking to do so, with some Crystal Method full blast...

They are a great mid, and I look forward to hearing the KIT41 in about a week.

Thanks again,

[Kevin P]

Kevin, thanks for taking the time to reply to my question - I wasn't trolling, I swear!

I own a set of the WR125's, and really like them - thanks to your PM, I reached Bob at CSS yesterday, and have ordered the balance of the KIT41.

I asked about efficiency mostly out of curiousity, since with my 30wpc Teac, I am able to achieve any volume I need, so I wanted to learn a little more about the specs - also, to your credit, this information is listed in the assembly plans for the kit.

I have managed t ...

Hey... I didn't think you were trolling.      

Yes.. you don't need much power to get them to full steam.   Even the cheapest HT amps on the market have more than enough power to drive them.

[revelator]

Does anyone know why this particular tweet was chosen for extending the WR125 highs?

I am in the process of building a pair and was wondering wether to use a top mount (such as the hivi tn48, for looks), 0r one of the small Dayton $5 tweeters crossed @ >10K.

Is the WR125 worthy of a higher priced tweeter? Anyone out there tried other tweeters with it? recommendations?

Thanx

[Kramer]

Well, they guys in the know (Dan, Kevin, and whomever else  ) have paired up the WR125 with 3 different tweeters (Usher, Audax, Hi-VI). I would say that those choices pretty much covers whatever application you need (the good, the bad, the ugly ).  

Right now, Im throwing together a WR125 kit using the Audax tweeter. I should be finished this weekend (I have some photos here: http://www.pbase.com/kramer/jbl_2500_upgrade ). I chose the Audax version based on the tweeter's flange size (the cabinet is limiting me, as you can see from my photos). I really hope to try (or convert my current WR125 to)  the Usher version. It uses a smaller sealed cabinet (and should match with my not-yet-released KIT641 front speakers).

[Kevin P]

We choose that tweeter because it's only used about 10K and above in the KIT41 design.    I wouldn't use it in an application where it's used down to a traditional crossover.    The WR-125 is good enough full range that the tweeter just adds a touch of top end so it's not all that critical.   Using the Usher in that design would have been an utter waste of money.

We have a smaller MT design where we are using the Usher.   In that design we crossover at a more traditional 3K and it's really worth the money to use the Usher as it's a 1000% better tweeter used down into that range.  

It really is best if you are going to try adding a tweeter that you have some way of measuring the system.   Doing it by ear can be an ugly experiment.

[Kevin P]

Well, they guys in the know (Dan, Kevin, and whomever else  ) have paired up the WR125 with 3 different tweeters (Usher, Audax, Hi-VI)...

Dan used the Audax because he had them.  The Hi-Vi was choosen based upon price/shielding.  

The Usher was choosen based upon performance.