Replacing the two 12' in my combo

Discussion in 'Amps and Cabs [BG]' started by Quzumm, Aug 5, 2001.

  1. Quzumm


    Sep 25, 2000
    Trondheim, Norway
    I have a Laney DB 300C combo, with two 12' speakers. I am not very happy with the sound, the speakers start to distort too early and it doesn't handle low notes very well. Because of that, I'm thinking about getting new speakers.

    I have been looking at some Eminence speakers, and the Thiele-Small parameters says "Compliance Equivalent Volume (Vas) = 67,88 liters" (Delta 12LF). Does it mean that each speaker needs 67,88 liters of cabinet volume? The cabinet part of my amp is about 100 liters, is that 45 liters too small for the two Eminence speakers?

    Are there perhaps other 12's that will suit my combo better?

    Also; I've read about tuning a cabinet after the speakers. Do I have to do that if I change the speakers in my combo?
  2. You can download my Musician's Reference spread sheet from my web site at and sort it by diameter and DBK cu. ft.

    This will show you all the speakers I have catalogged, and the amount of cabinet volume they require for optimal performance. Two speakers in the same cabinet... you must double the cabinet volume.

    Look at all 12" drivers by both the DBK cu.ft column (cabinet volume) and DBK F3 column (lowest frequency). This will give you an idea of what is required for you needs. Be sure to calculate your existing cabinet internal volume as a reference point.

    The pair of Delta 12LF are optimally enclosed in 6 cubic feet or 170 litres, tuned at 41 Hz, with a -3 dB cutoff at 39 Hz. If you put these drivers into the much smaller cabinet of a combo, the bass response will suffer.
  3. Quzumm


    Sep 25, 2000
    Trondheim, Norway
    Thanks for the sheet! Nice thing for a number-freak like me... :)

    But there aren't many 12' speakers that are "small" enough for my combo, and those who are small enough seem too have poor bass response. The only one that was both "small" and had a good bass (and mid) responce was the Rockford RFP-2412 XLC (row 233), but it seemed to be quiet? SPL = 90 isn't loud enough, is it?

    You said that the bass response would suffer if the cabinet was too small for the drivers, but how much will it suffer? Would it be better to use a pair of drivers that require 150 liters and go down to 40 Hz (-3db), than using a pair of drivers that my combo is "big" enough for, but only goes down to 50 Hz (-3db) for instance?

    Again, thanks.
  4. Yes, you are experiencing what has been discussed here at great length: too big drivers in too small cabinets.

    You can sort the spread sheet by 1) Diameter, (2) DBK cu.ft and (3) DBK F3. You can see which will fit optimally, and where their F3 cutoff point is.

    If you want something that performs very low in a small cabinet, it will be a subwoofer that is NOT very loud. If you want to give up low frequency extension, in favor of being loud, any of the 12" will do.
  5. Quzumm


    Sep 25, 2000
    Trondheim, Norway
    I've been doing some reading, learning and thinking, which has given me more questions... :)

    1) Is cabinet part of the combo vented or sealed? It has a hole in the front, with a 10 cm diameter, but there is no pipe inside the hole. If it's not vented, what's the idea with the hole?

    2) Do drivers with bad bass response distort easier at low frequencies than drivers with good bass response? I tried a 5-string on my combo. If I boosted the bass frequencies a little, the speakers distorted when I played the B-string, even if I had the volume at 2...

    3) Will boosting the 40 Hz on the EQ with 6 db make up for a driver that is down 6 db at 40 Hz? I belive so, but if so, there shouldn't be need for a cabinet that is flat down to 40 Hz? Besides, boosting the 40 Hz (and use the combo alone) doesn't give me the good, bassy sound I get by using a 15' ext. cabinet.

    Any help is appriceated.