Speaker kit experiments - an archive of the Jäger Speaker development

[Paul Joppa]

Dear Paul Joppa;

Could you explain what your "bridged T" network does for the new speaker?

I am sure there are many on our Forum who would be interested in how you developed it. PB says it works a treat!

I hope to hear it myself in late June.

Cheers, Hank in Eugene

Sure. It's a long-ish story though ...

First, the woofers are Zobeled to give them a constant impedance with frequency. (That's a simplification; the lower woofer is cut out so only the upper one is active in the crossover region - but the end result is close to 8 ohms in the audio band.)

The woofer itself has a resonance at a bit over 5kHz, with about a 4dB peak. Above the resonance it falls at 12dB per octave. By using a suitable notch filter, that is made to be a 6dB/octave roll off from 2800Hz to around 10kHz. The bridged-T is a form of notch filter that maintains constant input impedance at all frequencies, which is needed for the crossover itself to work into. It has 4 resistors, 2 caps, and 2 inductors - more complicated than the usual RLC notch.

The woofer crossover combines with the 6dB/octave to give something very close to a 4th order Linkwitz-Riley function at the 2800Hz crossover.

 

[Doc B]

Kelvin got the production impedance compensation networks installed in the cabinets Wednesday. The improvement was one of those "whoa, didn't expect that!" kind of things. Yesterday I got the external passive crossover boards laser cut, and today I built them out and installed them. I cannot explain why since the part values are pretty much the same as the crossover and network prototypes, but the speakers have taken a very big jump forward with these production prototypes. It's getting pretty wonderful. If you think you have heard them at their best, you haven't yet. I suggest you come by tomorrow and listen 12-3.

 

[Paul Birkeland]

It has 4 resistors, 2 caps, and 2 inductors - more complicated than the usual RLC notch.

I've studied lots of speaker designs, and I've never seen a speaker level bridged T filter used before.  (This is where PJ steps in and provides a link to an obscure JBL design that used one!)

 

[Paul Joppa]

I've studied lots of speaker designs, and I've never seen a speaker level bridged T filter used before.  (This is where PJ steps in and provides a link to an obscure JBL design that used one!)

The bridged-T is (was) commonly used in line-level studio gear before WWII, which used matched impedance connections. That came about from telephone technology, probably because phone lines were used to connect the studio and/or concert hall to a radio transmitter. Once gain became cheap and negative feedback became common, studios transitioned to low source impedance/high input impedance. I've never seen it in a speaker crossover either. I suppose the cost of twice as many components was off-putting. Today, commercial designers are more likely to us computer optimizations to achieve a good approximation to the desired target function, using as few component$ as possible.

For this design, I wanted to separate the eq from the crossover, and give the eq a constant input resistance to make it more flexible with different amps - looking ahead to the possible use of active crossovers. (I did a similar thing with the tweeter eq, but it's simpler.) This also makes the crossover design straight out of the book, so it's easier to understand, and also regular commercial active crossovers could be used. (We'll have one ourselves of course, but our customers are often independent minded and/or experimental.)

 

[Hank Murrow]

Dear Paul Joppa;

I am heartened by your decision to separate impedance matching circuits from the Xover circuit. This means I might be able at some point to make use of my XM-9 Marchand fourth order three-way Xover somehow. Previously, i used it to cross between a Linaeum tweeter, a 5 inch Vifa T-line, and a Focal 10" Kevlar T-line. wonderful speaks, but not sensitive enough for my Custom BH 2A3 amp. My electric piano in front.

Cheers, Hank in  Eugene

 

[Doc B]

I have just sent in the order for the production prototype cabinets that we will use to shoot the assembly manual for this kit. Getting closer and closer.

 

[Hank Murrow]

When do you expect to release the kit?

Cheers, Hank in Eugene

 

[Doc B]

Once we have the assembly manual shot we will start taking pre orders. The new cabinets should be here pretty soon.

 

[Quattrofish]

I had the good fortune to spend a few hours with Doc at Bottleheadquarters a couple of months ago, just after he installed the impedance compensation networks.  We listened to a wide range of music, from just about every source known to Man.  We tried good recordings (the Tape Project!  OMG!), crappy digital recordings, and everything in between.  His new speakers are fantastic.

By that, I don't mean that they made crappy recordings sound good.  They are too revealing for that.  What they did do, however, was let the music shine through without emphasizing or masking anything.  Poor recordings were revealed for what they were, but they were still enjoyable.  Good recordings, on the other hand, were unlike anything I've yet heard.  One of my favorites is "Saxophone Colossus" from Sonny Rollins.  It is one of my reference albums, I know every note and brush stroke, and I listen to it on every system I can.  I've never heard it sound this good.  The same can be said for every album we tried.  Driven by the Stereomour II in Doc's listening room, these speakers kick ass.

For contrast, my personal speakers are my own design/fabrication and are something of a homage to the Omega outlaws.  They consist of a Fostex 120a in a sealed volume, rolled off with a single capacitor at around 300hz, driven by my Stereomour.  In a separate sealed volume I've got a Dayton sub driven by a Crown XLS1500, digitally crossed over to integrate with the Fostex.  At low to medium volumes they sound pretty damned good.  Incredibly fast and detailed in the mids, as full range drivers so often are, with gobs of very punchy bass.  I've blown the minds of many a visitor with these speakers, and it pains me more than a little to admit that the new Bottleheads are significantly better in every way.  All of the detail and articulation, with none of the shout or high-volume breakup I get with mine.  The bass is all there and perfectly integrated.  Rich and full with no boom.

Am I gushing?  Perhaps, but not because I have anything to gain.  On the contrary, this is my attempt to give back a bit.
I've learned a tremendous amount from this forum and rarely have much to share that any one of you don't already know.  In this particular case I'm one of only a few civilians to get my ears on these things so figured I'd give my best attempt at a useful review.  If you are in the market for new speakers, I highly recommend giving these a shot.

 

[Doc B]

Wow, thank you so much, Mike! We're hoping to see the final prototype cabinet panels this week and get started on the assembly manual. As usual the process is going slower than I had planned. But one way or another we will have things far enough along to take pre-orders this month.

For anyone who wants to hear the speakers, we have them set up in our listening room. A great day to hear them will be this Saturday from 12-3. We will be having our monthly meetup, spinning vinyl with an experimental all tube moving coil cartridge step up preamp. Or give us a call and we will be happy to arrange a time for you to hear them during the week.

 

[Doc B]

I'm thinking I have not shown the back of the cabinet yet. This is a pic of the prototype built just prior to the production one we will be building for the assembly manual. It is 98% the same, the 2% difference being that the binding posts will sit a little higher on the back panel to simplify the internal wiring. You can see the cubby hole in the bottom for the passive crossover. That will allow easy removal of the crossover when we come out with an active tube crossover for biamping, some time in the future. We're working out packaging right now and then we will be moving on to shooting the manual.

 

[Deluk]

Why do the binding posts have to be up that high? There is plenty of room between the port and the cubby hole. Would also make things tidier behind the speaker when set up. Dare I say that there are many choices of speaker post inserts which would neaten things up too.

 

[Doc B]

The binding posts will sit a little higher on the back panel to simplify the internal wiring. There is an impedance network board for the woofers and the tweeter, that is mounted on a solid center divider between the two woofers. The binding posts are high enough to make a short connection to that board. This way there is only one easy to seal hole through the center divider for running the wiring to the lower woofer, rather than four or five holes back and forth from posts to board or board to upper woofer and tweeter.

 

[butchbass]

If you have a little age on you and are arthritic the higher positioned binding posts will be a plus!

 

[Hank Murrow]

Well after Paul Birkeland(with his wife and new baby boy) visited our home in Eugene last week giving a very positive account of the new speakers, I am curious once again about the possible delivery date. Paul said that the high sensitivity of these speakers will allow the Custom Bottlehead/JJ 2A3-40 equipped stereo amp that Paul built for me to really sing freely, as compared with the Orca/Buf Subs currently in use, which bottom out when stressed with big symphonic music, Like Mahler, etc.

So, I am eager to hear how the final design is going together, and when it may be available to those that live south of the border in Oregon. I would welcome a trip north to hear them and pack a pair home, as I have deferred an art/business trip to Seattle, hoping soon to bring back a pair to build. Any new word on a delivery timeline Doc?

Cheers, Hank in Eugene

PS: Meanwhile, here is the setup waiting for them(do they have a name?).

 

[Doc B]

I'm hoping to be ready to take orders in September. We're getting down to the last few details.

 

[Paul Joppa]

.... We're getting down to the last few details.

Such as a name! I've been calling them the "Nameless Speaker" for a while now...  :^)

 

[Doc B]

You are assuming I don't have a name that I'm keeping to myself . Josh and I are leaning towards Jaeger, as in,

If you have a Kaiju, you need a Jaeger.

We got some good news today about pricing and packaging, so we have moved another small step forward.

 

[Deluk]

"If you have a Kaiju, you need a Jaeger."

I had to Google that phrase and all then became clear although all of that was completely new to me. Nice connection. At least I now have a possible answer to the question I asked a few weeks ago.

 

[Karl5150]

So Doc, with all the effort that went into these does that make you guys the Jaeger masters?