Tube Friendly 2 Way Designs

[JoMoCo]

Hi, I would like to build an efficient, high resolution, 2 way able to be driven by relatively low powered (8 to 24 watt 300B etc.) tube amps. Simple, passive crossover if possible. I love the sound of these amps and want to get speakers that work with their old school mojo.

I stumbled into a pair of 375 type drivers labeled "Jim Lansing by Ampex" attached to rather large metal horns labeled Ampex D-6870.
Locally, there is someone recommending a TL bass cab with alnico 2215H speaks he has for sale (are they efficent enough for this app?). I am open for input for designs that fit this general criteria and am willing to either use the 375's or something more appropiate if called for. I also have some 2235's waiting for either this, or another project in the future.

Thanks & Fire away!

[jeenie67]

Hi, I have Altec 14's and 15's...very close to what you might want...check em out online and copy? 12" woofr and HF horn. Need a few watts to tick off the neighbors! I have tubes too and Crowns, and Carver(stored away)

[louped garouv]

I would see what you can get out of the 375s and 2235s before buying more stuff...

you may (or may not) want to add a tweeter with a passive crossover to help with the 375's upper limit duties

have fun!

[BMWCCA]

I also have some 2235's waiting for either this, or another project in the future.They'll sound fine.




And then you'll want lots more power! ;)

[robertbartsch]

Be careful here.

If you must have tubes, then you absolutely need a high sensativity rating speaker. Most Altecs VOTT 2-way systems will fit the bill but most JBLs will NOT.

You need a sensativity rating of 98 or so db at 1 watt, from three feet.

[JoMoCo]

My target would be for the complete system including crossover & speakers to be able reach 93dB 1w/1m approx., give or take 4dB with a reasonable impedance curve. Interestingly, so called "tube watts" / or more correctly speaker driving ability, for the 300B output tube, output transformer & power supplies, is more negatively affected by large phase shifts & low (below 4 ohms) impedance dips than purely lower sensitivity output. Now what are sometimes called "flea powered tube amps", those under 4watts, need the super high sensitivity speakers to really sing...;)

Assuming a reasonably smooth impedance curve...From a 6moons article - "A good rule of thumb for watt/dB combinations is 4w/93dB where every 3dB decrease in speaker sensitivity requires double the power wattage from the amp. Hence, 8w/90dB, 16w/87B, 32w/84dB and so on.":blah:

Remember some speakers / crossovers are easier to drive than others and the whole circuit from output transformer/device to cabling to speaker network to drivers need to be synergistic....YMMV:blink:

[LE15-Thumper]

By TL do you mean transmission line ? Because they are generally not that efficient. Seems an 030 or 001 or S1 would be a good choice.
Just my 2 cents

[Tom Brennan]

I wouldn't believe those screwballs at 6Moons if they said night was dark and day was light. 4 watts with a 94db sensitivity system (as would be the base sensitivity of a system using the 2215) isn't gonna give very satisfying dynamics, in theory you'd run out of gas at only 100db. That's pretty loud but momentary dynamic peaks can call on more than that if.

On the other hand most audiophiles settle for poor dynamics anyway and fixate on other sonic attributes. But IF you want good dynamics with 94db speakers you'll need some power.

[iain42]

I wouldn't believe those screwballs at 6Moons if they said night was dark and day was light.

:barf: The recent Sarajan 300B article on 6moons gave me nightmares :barf:

[JoMoCo]

The bass cab mentioned in the first post, from the pic sent, looks like a scaled down variant of the "scoop" style cab. I know the LE15 / 2215 xmax is less than newer ferrite 15" and benefit more from rear horn loaded cabs to gain bandwidth and output from the cab design...

"Transmission line" is a type of specialized enclosure topology, in which when correctly designed, sound from the back of the bass speaker passes along a longer path within speaker enclosure and emerges from the open end of the path "in-phase" with the sound radiated from the front of the driver, enhancing the output level at low frequencies.

[kegger]

It's all relative,

Depends how much volume you really want/need for your apllication.

With 30 watts of push pull tube power I can power pretty much any speaker I own in my setting
to volumes louder then I "need".

On speakers of 90-93 db sens 8wpc does more then I need, 95-100 5wpc is enough for me here,
less then 5watts it's over 100db sens.

At the present I'm running 2225's to 2118, to 2404 at about 97db sens, the little SEP EL84 amp
isn't even sweating at all to give an incredible amount of volume.

Also ran the 2225 to a waveguide an comp setup 2-way with nice results, the other setup that
does better bass is an HPM-100 woofer to a waveguide and compression driver at about 93-94.

Impedance plays bigger part as mentioned, non complicated xovers, even lower sens speakers
can be driven with relitively small amps when they are bookshelves using smaller drivers.

[Beowulf57]

Or you could play around with this type of design: http://audioheritage.org/vbulletin/showthread.php?t=20973...sensitivity 102-103dB/watt @ 1 metre.

[JBLRaiser]

If I'm listening to Eva Cassidy, a few watts will do. For Pink Floyds' Comfortably Numb, a few hundred watts will do.

[Ian Mackenzie]

I think you need to be looking at 95 db sensitivity or you will find yourself sift clipping those types of amps.

The E145 and a suitable horn like the 2397 and 2441 driver might be interesting.

If you can afford it look at the new GPA drivers. There are some members who use that type of driver with tubes amps.

Ian

[JoMoCo]

Any recommendation for a vintage or modern 12" that would compare or surpass the Altec 414 in the midbass keeping in mind the 2way configuration?

"One advantage of the 12" Altec/GPA driver is a cabinet volume one-half of what a 416 or 515 15" driver require. Don't expect deep bass - that's the job for separate subwoofers, not a high-efficiency midbass driver."

[Allanvh5150]

Why don't you choose the quicker and much easier path and get a larger amp?

[JoMoCo]

I have both larger ss and tube amps in house but they both have completely different sound character /flavors. The simplier tube designs simply sound amazing and more direct in their own way...

[spkrman57]

JBL 2226 and large format compression driver/horn crossed over at 800hz or 1600hz.

97db/watt works really nice with my 300B SET amps!

Regards, Ron

[JBLRaiser]

I have both larger ss and tube amps in house but they both have completely different sound character /flavors. The simplier tube designs simply sound amazing and more direct in their own way...
WATTS!!! Bi-amp with tubes on top and experience NIRVANA.:homer:

[JoMoCo]

After some searching ... :blink: I am considering the JBL 123A-1 (possibly two in series to raise impedance and sensitivity slightly, maybe even try them in the proto Altec 817 cabs...the Honken Onken's, actually some well preserved Stanley Screamer's SS 1120-R) The 123A's appear to have been run by JBL full range in various configurations with simple high pass to the Mid or HF in simple 2way ie L88. Also the qts allows other options including dipole possibilities... and starting out with Zilch's econo wave for the HF first and moving up from there...:bouncy:

http://audiokarma.org/forums/showthread.php?p=1856214#post1856214

[TnTn]

Are these cabs to big for you? If you have the budget, I recommend going with the B&C for possibly more clarity on the upper end. That's what my friend with really good high frequency hearing told me. Otherwise, both of us are happy with this project. He might be starting his soon. If you have time, do a search on Russellc's posts.

http://audiokarma.org/forums/showthread.php?p=2348382#post2348382

[Russellc]

Are these cabs to big for you? If you have the budget, I recommend going with the B&C for possibly more clarity on the upper end. That's what my friend with really good high frequency hearing told me. Otherwise, both of us are happy with this project. He might be starting his soon. If you have time, do a search on Russellc's posts.

http://audiokarma.org/forums/showthread.php?p=2348382#post2348382
I combined JBL 4647 ( 4507 and 2225H ) and the Econowave using both the recommended selenium driver as well as JBL 2425H. Great results with all 4 ports open ( 40 hz ). Later switched to 2235H, one or two ports closed. Either one could be driven to ear splitting levels with a dyna ST 70.

Russellc

[JoMoCo]

Are these cabs to big for you? If you have the budget, I recommend going with the B&C for possibly more clarity on the upper end. That's what my friend with really good high frequency hearing told me. Otherwise, both of us are happy with this project. He might be starting his soon. If you have time, do a search on Russellc's posts.

http://audiokarma.org/forums/showthread.php?p=2348382#post2348382

Hey tn, the cab size is OK ;) If I could only find a set...that could be the hard part. Which B&C driver / horn combo are you refering to? :blink: can you post a link? Thanks.

[JoMoCo]

I combined JBL 4647 ( 4507 and 2225H ) and the Econowave using both the recommended selenium driver as well as JBL 2425H. Great results with all 4 ports open ( 40 hz ). Later switched to 2235H, one or two ports closed. Either one could be driven to ear splitting levels with a dyna ST 70.

Russellc

Russellc, Thanks for the info...have you tried the 2225 or 2235 in your Altec cabs? What drivers are you using in them, 515's or ....?

[TnTn]

I got lucky with the whole setup. One of old JBL experts I meet up with from time to time just happened onto a deal that day. He didn't want to take the cabs home due to having too much stuff already, so he sold them to me. We do see these cabs from time to time on eBay. Since I also have the Model 19, I would also recommend the 416-8B. It is not as accurate sounding as the JBL and does not go as low, but it sounds very nice and goes plenty low enough for me. They are very SET friendly as well.

The B&C compression driver is also used in Pi-Speaker's premium option. It is the DE250 but you could also use the BMS equivilent, if you could find it. Seems like BMS stuff is hard to find. Big disclosure, I have not have a chance to hear either the B&C or the BMS. Just going by what's written on the web. The horn I am using is the PT waveguide as detailed on the humongous AK thread. If you go to the first page and follow the links to the member's build page, you will see that people have tried

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=294-605

[doodlebug]

I combined JBL 4647 ( 4507 and 2225H ) and the Econowave using both the recommended selenium driver as well as JBL 2425H. Great results with all 4 ports open ( 40 hz ). Later switched to 2235H, one or two ports closed. Either one could be driven to ear splitting levels with a dyna ST 70.

Russellc

Confirming the 4507s/2226H's. A nice and reasonably efficient setup. Haven't gotten to the Econowave but have the parts. Currently, I use the 2445J and a 2380 CD horn.

The bigger question for our OP is what size room and how loud does he need it? This will determine wattage requirements, IMHO. Otherwise, all the other variables will make the project just that: Variable.

Cheers,

David

[Russellc]

Russellc, Thanks for the info...have you tried the 2225 or 2235 in your Altec cabs? What drivers are you using in them, 515's or ....?
I had 515 8G, but now use 416 8C in the Altecs. The Jbl drivers arent big enough to fill the altec holes! I believe the Altecs are actually 16 inches. I think it can be done with some of the older 825 cabs?

Russellc