Port sealing

 

Gold Member
Username: Arande2

Rattle your ... Missouri

Post Number: 2922
Registered: Dec-06
I'm not asking for advice


Alright then.. I have a couple of Bose speakers I got at a garage sale for cheap a while back, and I've used them in different situations. Eventually, they got stuck in my room powered off the old HT receiver (Yam HTR-5740).

My most recent 'experiment' was to add a strong bass EQ curve. I basically just stuck my headphone amp into the signal path and turned on the bass boost. It's 3dB up at 130hz and maxes at 13dB around 20hz, where it goes back down to 0 at DC (1st-order). There's also a 10dB boost at 60hz (Q unknown).


There was a huge amount of port chuffing because of this, so I sealed off the ports, stuck the speaker drivers side-by-side (for more boost), then stuck the speakers against the wall. Suddenly the deep bass is there, but the volume can't pass around 70dB or THD levels go insane. Luckily these are for background listening.

I know there's a good amount of power going to these at low frequencies since I tried dual 10w resistor (in para') in series with the speakers (low value) and they got quite hot at seemingly low levels, so it's your typical inefficent sealed box at low freqs.


My question for everyone is -

If you had a pair of speakers that extended to 60hz, but wanted more extension AND HAD NO OTHER CHOICE, would you increase the port length (instead of sealing - I couldn't do that with these), then EQ to give up max output, or would you prefer your 60hz extension with higher output. Remember, no subs or anything like that.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 12919
Registered: May-04
.

Forcing the driver to do what it cannot naturally do is a short path to serious problems. Excursions become dramatic and uncontrolled once you pass the system resonance. If the driver were capable of better extension and only limted in its measured performance by a designer choice - smaller box to accomodate placement, then eq might pick up the last half octave or so. Otherwise, you're overdriving everything. Overdriving home audio components is not wise IMO. You're thinking like your going to enter a car stereo contest, Andre.

.
 

Gold Member
Username: Arande2

Rattle your ... Missouri

Post Number: 2924
Registered: Dec-06
To me it seems like I'm just operating it similar to an EBS sub, where you operate the system below fs (sealed now).

It's obviously not designed for it.. you're right.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 12923
Registered: May-04
.

I don't know what an EBS sub is. Whatever it is I can pretty much guarantee it uses a driver more well suited to your experiment than anything Bose has ever produced, including the heavily EQ'd 901's.
 

Gold Member
Username: Arande2

Rattle your ... Missouri

Post Number: 2925
Registered: Dec-06
It's basically where you run it below the fs of the driver.. these drivers have too much THD at low freqs for it.. so yeah.


And I found the amp was clipping since I read 25v (and the driver wasn't moving much).. I had a resistor in line with the speaker which I will remove here very soon.
 

Gold Member
Username: Arande2

Rattle your ... Missouri

Post Number: 2926
Registered: Dec-06
Yeah big difference. Even with the high THD, it still puts out a good bit in the 30hz upper 20hz range.
« Previous Thread Next Thread »



Main Forums

Today's Posts

Forum Help

Follow Us