Pioneer BOFU, 8" fullranger problem

[gychang]

I have it matched with a tweeter that sounds great at low volume. Now we are in a large home and I enjoy my speakers particularly with amp32 playing guitar jazz (my favorite is Earl Klugh)

Here is the problem, at higher volume the cone seems to break up transiently, I am not sure how to put it... I don't think the amp is clipping. I notice either right or the left BOFU has the same problem.

Is this something that can be fixed with phase plug?, do I need to replace my beloved BOFU and move up from the budget king?

thanks,

gychang

[BHTX]

Originally posted by gychang
do I need to replace my beloved BOFU and move up from the budget king?

Unfortunately, yes.

[Pano]

i DO think the amp is clipping- and maybe the tweeter, too.

Check each driver in isloation on a passage that sounds rough. See if you can find where it's sounding bad.
Is it just the BOFUs? Just the Tweeter? Or Both?

[Kensai]

I have a hard time believing that the B20s are bottoming out here. I use mine on OB with copious amounts of EQ on the bottom end, and I get painful levels in room that create decent ambient levels throughout the rest of the house. In your Chang cabinets, you should have alot more cone control than on OB. You may want to look at the phase plug mod, if for no other reason than you'll be removing the pocket of air under the dust cap that will compress at higher level, resisting cone movement. Just a simple dustcapectomy would remove that problem, but they sound really weird without something filling that space over the pole piece, so why not phase plugs?

And, yeah, the Amp32 is probably underpowered for filling a large space. The B20s are not that efficient. PE states 90dB on their listing, but every set of DIYer measurements I've ever seen has been at least a bit lower. My rough, in my head, estimate is that the Amp32 pushing the B20s peaks around 96-98dB, so at only 4m away, that's down to 90-92dB and if you want your peaks much beyond that, you're going to distort and clip.

Have you tried your JVC with them in your new place. I'm sure they've got a good bit more juice than the Amp32. Maybe doesn't sound as good, but if its not exhibiting the same behavior, then you've got a definitive answer.

Kensai

[GM]

Greets!

I agree, at a rated 10% THD/14 W, I've 'cured' more speaker 'problems' with plenty of 'clean' power, so having a B20 collecting dust, I propped it up and connected it to a loaner 300 W/chnl Altec studio amp, rolled off the bass/treble controls and broke it in with some Eric Bromberg at ~85 dB avg/100+ dB transients/12 ft (diaphragm moving up to a finger gapped ~5/16 - 3/8" p-p) and to my ears didn't garble it any worse than at lower SPLs once doing the $0.98 tweak.

As always though YMMV, but if you like the speakers you owe it to yourself to try them with a low/no nfb amp with at least 25 squeaky clean watts and preferably at least the driver's 85 W in case you go crazy with some wide dynamic range symphony CDs. Remember, the tweeter distorts/burns out first when a SS amp clips, so there's no such thing as too much power, just a point of diminishing returns.

GM

[BHTX]

What amp is he using?
Ah, nevermind. Could very well be the amp then.

[GM]

Originally posted by GM
.......Eric Bromberg.......

Make that Brian Bromberg.........

[gychang]

Originally posted by panomaniac
i DO think the amp is clipping- and maybe the tweeter, too.

Is it just the BOFUs? Just the Tweeter? Or Both?

my initial impression was the BOFU... but will check again.

Originally posted by Kensai
I have a hard time believing that the B20s are bottoming out here.

And, yeah, the Amp32 is probably underpowered for filling a large space.

Have you tried your JVC with them in your new place. I'm sure they've got a good bit more juice than the Amp32. Maybe doesn't sound as good, but if its not exhibiting the same behavior, then you've got a definitive answer.

Kensai

Great idea, should've thought of it. Will try it tonight.

gychang

[Fast1one]

Headroom is NEVER a bad thing, just upgrade your amp and I bet you will be surprised Also you may want to upgrade your tweeter while your at it, even though it is crossed over high...

[pjanda1]

Why not hit craigslist and grab whatever big 'ol solid state suits your fancy? It likely won't be the ultimate word in transparency or timbre, but it'll help you sort your problem out. I doubt that your problem is the BOFUs.

pj