Meet report - Saturday Jan 7

[Doc B.]

The meet was a nice one today. Just 7 of us, which made for easy conversation and lots of listening. I spent a little time going over how I had established the current positioning of the new kit speakers and sweet spot in our listening room. I had spent yesterday afternoon roughly modeling the room in RoomEQ Wizard. The result surprised me - it looked like putting the speakers right at the front wall about 13 feet apart, and moving the listening position back about a foot from where it has been the past few years might be the magic setup. Gotta say so far it's working very nicely. Shooting the room shows there are a couple of bumps at 70Hz and 300Hz to work out still, but the response is very smooth above 300 Hz and extends right down to about 30Hz. Tweaking the toe in a little got the imaging to be very believable. Today I started with yesterday's setup -  tweeters driven from a single stereo Kaiju and a pair of strapped Kaijus as monoblocks, one on each speaker's woofers. Plenty of power and a nice mellow yet resolved 300B sound.

PB had completed a second Big Betty quad PSE 6550 amp, so I switched back to a single amp configuration on the speaker crossovers and we put those monsters in the system. PARTAY! I subjected to poor meeting attendees with some near club levels for a few songs, followed by some super duper dynamic symphonic stuff. The amps and speakers showed perfect composure, which I can't say for the audience. Shit was loud.

The bottom line is the speakers are definitely something I'm feeling good about offering. In fact I think they are our new permanent speakers in the listening room. And the Big Betty project has the go ahead for a second prototype with iron of our own design rather than off the shelf stuff.

I'll take some pics when I get back Monday morning so you can see what I'm talking about. Thanks to all who stopped by today and thanks to Peebs for finishing the second monster and lugging the pair over. It was really fun!

[johnsonad]

Hopefully Josh will post a couple of pictures of the new room set up once it has settled in.   If you have visited BH before or have seen the pictures of Doc's system, it's big and sounds outstanding but not for the timid or a small listening room.  When I walked in yesterday it looked like something most people could easily fit in their home listening room. 

I learned a lot from Dan's talk on using REW and still have a lot to learn about using all of the features.  It's one of two programs I've used to help set up listening rooms and works very well.  Once you start using a program like REW you find that even small movements of your system can make larger improvements in sound vs. changing out equipment.  The best part is REW's free and a mic is cheap.  All that's left is a mic stand and a laptop and you are ready to start.  Thank you Dan for putting the talk together!

The new speakers are sounding nice and best of all, they sound nice right up against the back wall which for some people, may be the only place you can put them in a room.  Dan put a pair of the limited run custom finished BeePre and Kaiju in the main system and man do they look good!  That walnut finish is beautiful! 

The time flew by as it seems to do and the only thing we didn't get to listen to when I was there was PB's custom amp build.  Hopefully he will bring it again to another meet in the future. 

Eileen, thank you for the treats and coffee and as always for being a warm and wonderful host! 

[Doc B.]

One thing I wanted to point out during the talk was how much the absorption coefficient of the room surfaces influence the modeled response. If you are using REW to model your room try increasing the front wall absorption coefficient from .1 up to something like .75. Watch what that does to smooth out the peaks of the front to rear axial modes. We have pretty heavily treated front wall in our room and it works. I was exhibiting at a show with Bob Hodas where he turned a shitty sounding hotel room into the best sounding room at the show by putting up a temporary frame filled with Bonded Logic cotton batts across the entire front wall. People waste so much money swapping gear when they could get so much more improvement from tuning the room.

[aragorn723]

Looks like you can buy that insulation as squares too.  6 of them for $30 at home depot.

Dave

[BNAL]

Wish I could have been at the meet, especially with the discussion about listening rooms. I have been reading the book Get Better Sound and it talks a lot about room setup. From my reading I know that I need a lot of work, especially with the front wall. So it was interesting to read what Dan was saying about treatment on the front wall. I'm going to look at using the Bonded Logic batts for my front wall.

I will need to figure how to get up to the PAC Norwest for one of these meets.

[Doc B.]

Look for The Master Handbook of Acoustics. There are a lot of copies on ebay for $4-5.

[BNAL]

Doc,

Thanks, I purchased a copy.

Brad

[Doc B.]

Here are a couple of pics of the meet setup. First is the speaker setup, with the speakers near the well treated front wall. Response is smooth down to the mid-low 30s in the this position and imaging is great.

Second picture is of one Big Betty quad SE 6550 prototype amp. 50 watts.

[Mikey]

"Second picture is of one Big Betty quad SE 6550 prototype amp. 50 watts."

Very interesting...
Any more details that you'd care to share?

[Paul Joppa]

We have talked among ourselves for many years about making an SE amp powerful enough to drive speakers of ordinary efficiency, while retaining as much of the Bottlehead sound signature as possible. This amp is my best shot at how to do it.

It's what I call a "transimpedance" amp, similar to the Seductor topology. Both stages are pentodes operated as pentodes, and the signal is direct-coupled between stages. That coupling acts in the current domain, though both driver input and power output operate in voltage mode.

[aragorn723]

That's a cool looking amp!  Are they 50w monos?  Thanks,

Dave

[johnsonad]

Yes they are and they double as room heaters if needed 😊

[Mikey]

We have talked among ourselves for many years about making an SE amp powerful enough to drive speakers of ordinary efficiency, while retaining as much of the Bottlehead sound signature as possible. This amp is my best shot at how to do it.

It's what I call a "transimpedance" amp, similar to the Seductor topology. Both stages are pentodes operated as pentodes, and the signal is direct-coupled between stages. That coupling acts in the current domain, though both driver input and power output operate in voltage mode.

Very cool.   

Is there a snowballs chance in hell that this will become a kit someday?
If not, maybe a DIY project similar to the SR-45?

Mike

[aragorn723]

Yes they are and they double as room heaters if needed 😊

They probably won't here in Georgia LOL.  What's the driver tube?

Dave

[BNAL]

From the picture it looks like an EL 84.

Looks like it would be a great kit.