B20's, sealed, wide vs narrow baffle?

[2litre]

Last weekend I tinkered with my B20's in some old school heavy weight Pioneer cabinets with a net volume of @1.25cuft. They were 16.5"w (outside dim.) and 8.5"d (internal dim.). I had the port tightly stuffed so it was more like a sealed than a ported cab.

I ended up running my receivers bass at -4 to have it sound right to me.
I liked the sound anyway though

So now I've got some ply and am getting ready to cut but am still wondering which would be easier in the bass. A wide front baffle with a shallow depth or a narrower front baffle with a deeper depth.
I'm thinking I should go with a narrow by deep enclosure but I'm not exactly sure why.

Right now I'm keeping height constant at @29"h. I'm using PE's response graph measurements (not those quoted in the catalog) for Fs, Qes and Qts which closely correspond to those I got with WT3. I haven't measured Vas on my drivers yet but am using PE's of 48.92l.
Using the calculators found at mh-audio.nl, 1.703cuft net will give me the .707Qtc I'm shooting for. I'm shooting for 1.9 so I'll have room for holey braces. I'll then add blocks to tkae up any necessary volume.

So why am I thinking I should go narrow baffle instead of wide baffle? BTW the intended listeneing room is 10'w x 13'l, music - anything but rap/hip-hop.

R/
Jim

[Godzilla]

http://www.zillaaudio.com/pioneerb20-3cubox.htm

Maybe somehow the link above could help?

Did you use a tweeter? Maybe it sounded bass heavy because there was no tweeter and that's why you turned the bass down?

Godzilla

[2litre]

Godzilla,

No I didn't have the Neo's hooked in at that time. And I didn't have them in room either.
See I was going to do a Half Chang build but decided to do a simple sealed instead so I have Neo's as well.
Getting my feet wet on the cheap.
I'll save a Chang Family build for when I get some Fostexes, and I'm going to get some

I've been to your sight probably 30 times in the last 6mo looking at all four B20 buttons(?). Then I finally listened to them in those freebe boxes (Pioneer CS-911A's, since reassembled and passed on to a buddy) and generally liked the sound, which is what prompted me to scrounge up enough 13-ply to make a 29" high cabinet.

Right after I posted I started looking into a golden ratio box.
I used a link found in another post, along with an FR125 page at P-10's site.
http://www.carstereo.com/help/Articles.cfm?id=5
It gives me 15.12w x 9.07d x 24.49h for 1.94cuft.
I could modify that a bit to 13.5w x 8.5d x 29h for 1.925cuft and just get busy.
Similar to your 'Exotic B20" build, but larger so I can brace and block to get down to a .707 Qts. I want to hear that alignment first.

R/

[HareBrained]

The answer really depends on placement within the room and whether you're planning to have a baffle step compensation circuit.

The wider the baffle, the further down in the spectrum the baffle step is push until you no longer need any compensation (~12" outside the driver on each side). It's only relevant if the speakers are free standing and a couple of feet from anything else. The more stuff in close proximity, the less severe the step will have (in dbs). If next to a flatscreen TV, no BSC maybe needed and the width is more of an aesthetics question. If they are free standing, and you don't want the large coil in series with your driver, you're going to want to go wide.

[norman bates]

I had my b20 in a box 2' wide, 3' tall and 1' deep. No baffle step, no fill, sounded great !!!!!!!!!!! But big, heavy box.

But if you have the space and making a box is free to you, go for it.

Norman

[2litre]

Thanks for the input Zilla, Norman and HareBrained.

I burned the better parts of last weekend building a pair of sealed boxes for them. Because I'm a wood hacker instead of a wood worker (Man, don't ask!) I ended up with probably the worst shape for them, 10"w x 11.5"d x 29.25"h internal for 1.94cuft. And in good wood hacker fashion, internal bracing is sub par (but at least there is some) but, in good wood worker fashion, they're heavily biscuited. Driver is set 21" up measured internally. @ 1/2" fibrous carpet underlay (not the chopped foam stuff) covers all but two areas of the interior.
Currently the front baffles are clamped on while I listen to them for a couple of days. Once my buddy gives me his take I'll look at buttoning them up.

Initial impressions are:
- They're too big for my room. But, since this is my first build beyond OB, I'm going to deal with them for awhile.
- Just as so many others have said, the drivers aren't spectacular at anything, but do a whole lot very well. Money well spent IMO.
- Baffle step hasn't been an issue at all in the intended listening room. In fact I currently run WMP at 0db for 31Hz, -5db for 62Hz, -3db for 125Hz and -1db for 250Hz to cut down on the boom.
- The driver is surface mounted. While tinkering I found there is a definate enhancement to SQ when a baffle is added around the driver to flush it up. Is that what a supra baffle does?
- It's best to listen to them on axis. Sounds obvious, and maybe it's a FR trait, but they actually sound engaging on axis.

No tweeter so far. I'll install them when I flush up the drivers.

R/

Jim

[norman bates]

I had luck trimming 1/4 of the whizzer off, then adding more hf boost with an eq.

Don't forget a little cotton batten loosly between whizzer and cone.

Norman

[gychang]

Originally posted by norman bates
I had my b20 in a box 2' wide, 3' tall and 1' deep. No baffle step, no fill, sounded great !!!!!!!!!!! But big, heavy box.

But if you have the space and making a box is free to you, go for it.

Norman

chance for a picture?

gychang

[norman bates]

lol, nope, that was over 3 years and a move ago.

Box is now at someone elses house with an 8" sub in it.


Norman

[2litre]

I listened to them for awhile after I posted before I found I had made a serious mistake; I had those SRS WOW effects turned on on my computer.
I had this set while using the monitors integrated speakers.
Big change! Now they are run flat with no manipulation of the EQ required in the bass and midbass regions, and that's a good thing.

I made the second change after listening to them over at Taperwoods house yesterday. He has experience voicing speakers. We listened for awhile and did some rudamentary testing with a Rat Shack SPL meter and his audiophile test CD. Track 17 is a decending sweep from 250Hz on down to 20Hz. Starting at 70db I had a +3db at 80Hz but what was surprising was that they were -3db at the 40Hz tone and -5db on the 31.5Hz tone.
Other items of note was the +12db hump at 800Hz, the drivers completely run out of steam beyond the 12KHz mark and that setting them just off the wall rather than 4ft into the room rounds out the bottom end nicely. We did the tone sweeps with them about 18" off the wall.
About the time I was looking at leaving he recommended stuffing the area above the division brace, the drivers chamber. So we stuffed one box and used his A/B-mono switch to compare boxes and evaluate changes. The stuffed one was definately cleaner.

Right after that test I loaded them up and brought them home along with the A/B switch. After a break I set them up with the switch to see if I could hear the difference or if I convinced myself I did back at his house. I immediately heard the difference between the cabinets. I picked the 'bad' one and openned it up and it was the unstuffed one. Good reality check. So I stuffed it similar to the other one and listened for the rest of the night. They now image better and take more power before audible distortion. Instrument placement was also enhanced.

So I still haen't installed the tweeters and I still haven't made the panel to flush up the driver, but I'm liking the heck out of them anyway.

R/