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Replacement speaker question

Discussion in 'Amps and Cabs [BG]' started by basss, Dec 6, 2003.


  1. basss

    basss

    Aug 27, 2001
    NYC
    I've decied I want to lighten my load by putting a neodymium driver in a small 1x12 cabinet that I have. I'm trying to decide between these three drivers
    B&C hpl64
    B&C hpl76
    Eminence deltalite 2512
    My cabinet has an internal volume of 1.3 sq. ft. and 2 2.5" square ports that are 3.5" deep. Acording to WinISD this box is tuned to 37.4 Hz, correct?
    WinISD says that the eminence driver has a stronger bass response than the other two. What other factors should I be considering? I realize I'm not going to get a ton of bass from this cabinet but I would like a little leeway with the low end EQ on the amp before the cab farts out. Is this where power handling becomes important. Thanks and p.s. I have Vance Dickason's book on order so I won't be bothering you guys (bgavin, petebass) as much anymore.;)
     
  2. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I ran it on Winisd Pro and if the ports are 2.5in high, 2.5in wide, and 3.5in deep, that came to a cab tuning of 68Hz.

    Funnily enough that is pretty close to the correct tuning for flat optimal response for the 12hpl64. The cab would be -3db at 72Hz. So that speaker could go in as a direct transplant provided you're happy with the lack of bottoms.

    The 12hpl76 has a similar -3db point, but the cab is too large, so there is a mild dip in the low mids starting at about 250Hz and staying 1 to 2 dB down right through the the start of the low end roll off.

    Strangely enough, the Deltalite does the opposite. The cab is too small, so there is a pronounced hump in that same frequency range. It is +3dB at 125 Hz. This is the same design philosophy Eden but we have a problem. With this cab and tuning combination, the cone excursion graph for this speaker looks awful. It's moving 24mm at 120Hz, 20mm more that Xmax. Don't do it.

    My vote goes to the 12hpl64. Cone excursion checks out, as does group delay and frequency response. And you won't have to change the porting.

    The usual warning applies about cone excursion below Fb of 68Hz fo this cab.
     
  3. basss

    basss

    Aug 27, 2001
    NYC
    Thanks Petebass!
    I was using port radius and not diameter to calculate the tuning frequency (duh!) Thats why mine was off.
    Would the hpl 76 with its higher power handling give me more room to eq in some lows below the tuning frequency?
     
  4. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    You're welcome.

    I'm a bit confused now. Words like radius and diameter suggest the ports are round, but in your opening post you said they were square? We'd better clear this up before we go any further.

    EQing in bottom end may help while the speaker is only being driven gently. But under gig type loads, it will probably bottom out, maybe even go splattttt if you play loud enough.
     
  5. basss

    basss

    Aug 27, 2001
    NYC
    The online version of WinISD asks for port diameter. I figured out the area of my square ports and found the corresponding radius for a circle of the same area (math argh!) so we should have it right.
    Does extra power handling help when boosting the EQ at frequencies below the cabinet's tuning frequency? I'm wondering if I should go for the hpl76 which is rated at 350W rms in order to have more room to boost the low end EQ.
     
  6. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Oh man I just typed out a longish reply and the PC crashed as I hit send........

    I'm a little burnt out but I'll go again.........

    Would the extra power handling help? This has caused great debate in the past because every scientific text tells you that frequencies below Fb cause speaker cone excursion to go off the chart and damage the speaker. Vance Dockason's book talks about sub-sonic filtration and protecting you speakers from frequencies below Fb.

    The problem here is that lots of commercially available speakers are tuned high, and if this rule was so hard and fast, every one of those cabs would blow. Which they don't - why? Probably because they're not driving those speakers at full tilt. So I guess the answer to your questions is probably yes, the extra power handling will help, but only if you feed the speaker considerably less power than it's official rating, and only in don't boost the lows with your EQ.

    That last one is definitely not open to debate. Talk to people in speaker repair shops ask them what type of damage they see most. The answer is mechanical damage caused by people boosting low frequencies.

    If more bottom end is a definite requirement, you have 2 choices. Add a 15, or go for another speaker, maybe something non-neo. The Eminence Omega Pro 12 would work well in that cab. The flat frequency response is similar but with a Fb of 39Hz compared to 68Hz, it will be more forgiving on the excursion and less likely to blow. You'd have to change your cab's porting. I'm not sure about this but in theory you could even get away with boosting low frequencies to a certain extent, but certainly more than on the other speakers we were looking at.

    Unfortunately Neo technology is still new and so far it's been aimed more at the PA market.
     
  7. basss

    basss

    Aug 27, 2001
    NYC
    Thanks again Petebass
    Changing the port dimensions in this cab would be very difficult as the ports are built into the wooden structure of the cab.
    In your opinion would the extra power handling of the hpl76 outweigh the advantage of the slightly better low end response of the hpl64 in my cab? In other words, which speaker would you pick, if you had to choose one of these?
     
  8. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    If it were me........ well I play in loud bands. I have speaker cabs that are tuned higher than the frequencies I pump into them, so I always use 2 cabs so they don't get driven as hard. I'm also a wierdo who prefers the sound when the low frequencies (40Hz and lower) are cut so that helps.......

    Sorry about the rave but my point is that I have examined my situation closely and made decisions based on that. That's part of the beauty of making your own cabs.

    I don't know enough about your situation, your gear, your gigs, and tastes to make that call for you.

    12's are hard. I started toying with the idea of converting one of my existing cabs into a 12 with 2x10 stand alone. The hunt for the right 12 continues several months later..........In a lot of ways, replacement speakers are harder than building a cab from scratch because you working within the confines of the existing cab geometry.
     
  9. basss

    basss

    Aug 27, 2001
    NYC
    Thanks for your help. I am planning on picking up a new head soon so I guess I need to decide exactly what I will be powereing it with before I decide on a speaker.