• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

How to get rid of bloated bass

djnagle

djnagle

AK Subscriber
Subscriber
Hi All. I just picked up these speakers last night. They are custom made with inner dimentions of 26.5"H x 9.5"W x 9.5"D. the woofer is the Scan Speak 21w/8554 8" with Kevlar Cone and the tweet is the Vifa but I don't know the model. I can't find a pic of the tweet with the same hole pattern as mine. Anyway, they are sealed cabs and the bass and lower midrange is rather bloated sounding. What causes bloated sound and how can I fix it. I found the woofs for sale in a couple places for $230-$260 so they "should" sound good.

 
Register to hide this ad
They look nice. Very handsome. Have you played around with placement much?... off the floor, away from the wall, etc?
 
In a sealed system if the cabinet is the wrong size the woofer can be underdamped and have a big bump in the response just before roll off. I suggest you model the woofer in a bass response program.

Whoa! I just modeled it and I'm surprised you're getting any bass at all. This woofer belongs in a vented box; modeling shows that in a sealed box the size used F3 is around 100hz but in a vented box tuned to 45hz the F3 is about 50hz and with a nice flat response. I must conclude either I made a careless mistake in my ciphering or the cabinet has nothing to do with the problem.
 
Last edited:
Hi Tom, I got the same results late last night. While I'm watching the bowl games today, I'm going to strip the cabs to 1. try to figure out what the issue might be and 2. prep them for cutting vent tubes!
 

Attachments

  • scanspeak.jpg
    scanspeak.jpg
    120.8 KB · Views: 83
I am guessing -- as suggested above -- the Qtc is too high (i.e., underdamped; the "Radio Shack Mach One syndrome"!) -- you can try adding a ton of stuffing to 'fool' the woofer into feeling as though it were in a larger cabinet. That will (should) effectively lower Qtc and flatten out LF response (at least somewhat).

SealResp.gif

source: http://www.carstereo.com/help2/Articles.cfm
 
Last edited:
djnagle said:
Can I put the port right behind the woofer?
Click to expand...

I think so. On the JBL 250ti, you see the woofer magnet dead center of the port when you look in there.

And those are nice looking speakers, hope you get them performing to suit you!
 
Simple ! You GET RID of the speaker.. Sometimes trying to get a Volkswagen to be a Porsche!!!!! aint gonna happen no matter what parts you modify !

Two ways should be tight and very detailed.. Best two way I ran was a pair of Fritz Carbon 7 ..Ported of course !
 
C.A.P said:
Simple ! You GET RID of the speaker.. Sometimes trying to get a Volkswagen to be a Porsche!!!!! aint gonna happen no matter what parts you modify !
Click to expand...

One wonders if you understand the quality of the parts and how loudspeakers work.
 
As an experiment before you cut any holes, you could try rigging a port in the tweeter's spot. A quick trial might be listening to the bass with the tweeter removed. If it is better, then maybe a port would be a good move.

I like the stuffing idea too, I would do that first...
 
OK, here is the problem!!! Yes, the cabs should be ported and I will do that, but the bigger issue is that there is an 8db bump starting at 1khz up to 3.5khz AND the crossover is a Dayton prebuilt that crosses at 3.5khz!!!

I did a WT3 test on the tweet and the low end was at 750hz so I am thinking need to build a 3rd order crossover for 1khz for starters.

Check my thinking but I think I right. Ideas???
 

Attachments

  • Capture scanspeak.jpg
    Capture scanspeak.jpg
    102.2 KB · Views: 44
  • 3.5k xover.jpg
    3.5k xover.jpg
    16.4 KB · Views: 38
Dennis, you don't have an active crossover to use to experiment with first? I run mine all the time but they are also a great tool for nailing down specs for a passive crossover.
 
I figured it was either a crossover issue or those weren't the original woofers. Seems an AWFUL lot of time and thought put into those for them for the response to be so far out of wack like that.
 
I was wondering about the crossovers, those Kevlar drivers usually have nasty peaks in the upper range. It's probably time to investigate notch filters or some form of EQ to tame the peak, that's standard procedure with many stiff but poorly self damping cone materials such as Kevlar, carbon fiber, aluminum and such.

1000 hz seems a very low crossover for a dome tweeter, I think 2000 or so is a better spot. What model Vifa is it? What do they recommend?

As Rob said, an active crossover will help quickly determine a crossover point but unless it incorporates EQ it won't help with the peak. You're an old horny, do you have an active around?
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom