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Could these drivers be the answer......

Discussion in 'Amps and Cabs [BG]' started by Rockin John, Feb 21, 2003.

  1. In my quest for something like a 2 x 10" cab for my 5 string, I discovered some drivers by the German company, Mac Audio:

    Mac Fire 250: 10": 320 Watt max: 160 Watt RMS: 4 Ohm: Sens, 92dB: Qts, 0.44: VAS, 39L: Fs, 33Hz: usable F range, 20Hz to 1Kz.

    They have a spun aluminium cone and rubber cone suspension. Don't know Xmax. Cost approx £60 each.

    They say the driver will live in a 3/4 Cu Ft sealed box or a 1 1/2 Cu Ft ported box where the port is 3" dia x 10" long. There's no info as to whether they're OK for bass guitar, or not. They are billed as subwoofers.

    They also do a 12" version.

    All the above came from a mail order catalogue (Maplin, for UK folk). There's a web site but it's all in German so I can't tell what other information is available. I've emailed them but no reply as yet.

    Any wisdom, guys?


  2. CS


    Dec 11, 1999
    I'm no techy but 92 db seems very low. THey might not be loud enough but I'm probably out of my depth here.
  3. ESP-LTD


    Sep 9, 2001
    They sure smell like car audio subs (nothing wrong with that, I happen to like car audio subs).

    I'd be concerned about Xmax as you said and perhaps magnet size and Xmech. The 1khz part might be a bit optimistic but with aluminum it's possible. The power handling is a bit low but they could measure that lots of different ways.

    I'd want more complete specs, but what you have is interesting though, assuming you have some power to put behind them. Given the sensitivity a pair of them biamped would match a quiet 1x10 box for top end. I used to use some aluminum cone 10's from MCM Electronics ($20 ea) that had Fs 40hz, but they were about 92db. I ran 4 of them in 2 sealed boxes and they were running flat out for a loud band practice. I liked the tone just fine however until they fried (70w rating).
  4. For a typical woofer, yes, but these seem more like sub-woofers, only going up to 1k (which is very low for a 10)

    *If* they can handle ,say, 200 watts sine tone at 30hz without gratuitous distortion, that would be about 115db of 30hz, which is a lot of bass.

    Its the ole excursion at 30hz which is the clincher, and not sure how to work that out yet.

    They do look promising though, but might still need a big cab (like a 410) to really get the lows without a big 'group delay' (I'm getting down on the technical jargon now :)
    definitely worth more research, a true sub woofing 210 cab would be nice, even though the general rule seems to be (judging by bgavins old posts) "if you want BASS, get a 15 or 18"

  5. I run true subwoofers (Rockford car audio) and can tell you first hand they have a very limited upper range. Mine are pretty much done by 150 ~ 200 Hz (-6dB). They are designed to pound in the bottom end, which they do very well. You will have to have something to handle the highs, or they will sound worse than playing through several layers of a heavy blanket.

    89 SPL is awful unless you have tons of power to drive them. I get 92 SPL from a pair of parallel subs (1w/1m) but I feed the pair a total of 900 watts each. This is all I can get from my PLX 3002 into 1 channel at 4 ohms.
  6. Over the weekend I've gleaned more about these drivers.

    ESP-LTD is correct. They are indeed in-car woofers. The tech people at Mac Audio sent me the datasheet, which includes loads of other drivers.

    The Xmax for the Mac Fire 250 and Mac Fire 300 is 16mm. Other missing parameters from my original post:-

    Qms for both, respectively, is 6.2 and 4.7.
    Qes for both, respectively, is 0.47 and 0.56.
    Re for both is the same, 3.2 Ohms.

    And the bits I didn't post about the 12", Mac Fire 300, Qts = 0.50; sens = 93dB; fs 32Hz; Vas = 65Ltr.

    I tried both drivers in WinISD using the above. It certainly seems possible to get the '250 flat to 30Hz in a small box. Two drivers in 80 Ltrs is about 3dB down @ 30Hz. The only thing is, is the port sizes. WinISD pumps out the red words Qes/... with every combination I tried so I've no idea what to do about that.

    The crux is, I guess, whether these drivers would get blown apart by a bass guitar, as they are apparently not designed for such use.

    I accept what Bruce says about the limited upper range and that something would need to be done about that should these drivers be OK in the first place.

    I also accept the business about needing plenty of watts. But just how many watts is all down to what's needed in the band situation. Like I've said elsewhere, about 100 top whack into that dreadfully inifficient Delta 15 cab is plenty loud enough, even for when we played outdoors.

    Any more thoughts gentlemen?

  7. ESP-LTD


    Sep 9, 2001

    Two of these guys means a 2 ohm load for your amp (like my subs). I suspect my QSC RMX-1450 will handle that if I'm gentle. This is where it starts to get expensive.

    It's whining because a high Qts driver (and Qes is most of Qts) should be in a sealed box. The popular rule-of-thumb is .5 Qts and above uses a sealed box. You can use a ported box but that speaker REALLY wants to resonate at Fs and you have to damp that. My solution is a driver that has Fs at 25Hz so I never get close enough to worry about it.
    To double your volume you only need 10x the power. That's a hard game to win, and thus the reason that most folks choose speakers that are sensitive instead of low.
  8. RJ: can you email me a scan of the complete T/S data? There are several pieces missing (Sd, BL, Mms).
  9. I'd love to, Bruce, but am not sure I really ought. I'm not convinved it would be right to give out this doc without permission.

    Please be assured that I'm not trying to be awkward, just respecting Mac Audio.

    In any case, those parameters you seek aren't on the document. It contains:-

    Fs, Re,Qms, Qes, Qts, Vas, Xmax, SPL.

    You could, I guess, try the guy for yourself then there'd be no problem:-


    Any early thoughts as to whether these units would be OK for BG?

  10. I got all the published info for the Fire 250 from their web site. They do not publish the rest of what I need. Based on the high Qts, I have no interest in this driver. It is a sealed box candidate for automotive use.
  11. Well, that's interesting. As the acknowledged layman, I wonder why it seems to come out quite well on WinISD in a ported box. Don't know about you, Bruce, but at the suggested 3/4 Cu ft sealed box you wouldn't get many of them in my car:eek:

    Forgive my ignorance, but does your disinterest mean the '250 wouldn't be siutable for BG, or does it mean you don't know?

    As the Qts causes the disinterest, would you be good enough to explain what Qts actually is and why it is a problem.

    I wonder, too, whether the issue might be it's cost. OK, the '250 is not so expensive, but it might do OK for those of us who really can't afford the top gear.......you know, the Rolls Royce vs the Ford.

  12. Petebass


    Dec 22, 2002
    QLD Australia
    I'n not the speaker guru but I have been reading up on this stuff. All of the "Q" factors relate to the suspension of the speaker that allows it to move back and forth. Qms deals with the mechanical suspension parts (the spider, the surround etc) and Qes deals with the electrical suspension (magnetic field, voice coil). The Qts is derived by multiplying the Qes and Qms, then deviding the result by the sum of same. So Qts is basically a calulation that gives experienced people(ie not me) an idea of how the speaker will perform, used in conjunction with the other perameters of course. Low Q's = good quality speaker.

    How did I do Bruce?
  13. ESP-LTD


    Sep 9, 2001
    These waters are way too clear thinks I, and so I shall muddy them somewhat on the Qts issue.

    "Q" stands for "Quality" in resonant circuits. For example a coil and capacitor in parallel resonate at a certain frequency and at that frequency the circuit has a low impedance (like resistance) to flow of current. A "high Q" circuit if graphed shows very rapid change as you leave the resonance frequency (a peaked graph); a "low Q" circuit is pretty much flat and indifferent to the issue.

    Applying it to speakers they consider both Qes (electrical- magnet and voice coil) and Qms (mechanical- surround and cone weight). A "high Q" speaker will really want to move the cone a lot at it's resonant frequency (like out of control) while a "low Q" speaker is pretty tolerant of such things and has a fairly flat response near it Fs (resonant frequency).

    You can put a low Q speaker in a sealed box and it will sound very nice (without much bass), which you can put a high Q speaker "carefully" in such a box and adjust the size to gain some control over the peaks in the response (without much bass).

    You can put a high Q speaker in a ported box and at tuning frequency, the response nicely drops away at a rapid clip. If you put a low Q speaker in a tuned box, near Fs it will have a BIG hump in the response (and perhaps at Fb as well?) where the speaker cone is out of control.

    --EDIT- note to self NEVER POST AT 5:00 AM ---
    This was originally backwards and has been corrected; my apologies to all.

    LOW Qts usually means big magnet and voice coil which leads to tight motor control over the cone.

    HIGH Qts usually means smaller magnets and voice coils and the cone can flop around a lot based on it's intertia; starting and stopping are not tightly controlled by your amp.

    LOW Qts costs money.

    HIGH Qts car audio subs usually comes in shiny colors with marketing hype like "Mega Bass" "Turbo" "Expensive Rare Metal" (substitute current rare metal).

    I have direct knowledge of the last bit, as my 12" JBL car audio subs have a Qts of .43 which is why they were only $55 each and have BRIGHT ORANGE writing with "1000 WATTS" on the cones.
  14. Yes, the waters are now like pea soup......Thanks!!

    I can only conclude that high Qts = smaller numbers, and vice versa?? Considering Eminence drivers, the Kappa 15Lf has a Qts of 0.38 and would cost me about £75: the Delta 15 has a Qts of 0.49 and cost about half that figure: the Gamma 15 has a Qts of 0.75 and is cheaper still.

    From that perspective, I presume, the Beta-8 with a Qts of 0.34 should be good in a ported box even though other parameters might make it unsuitable for BG. Conversely, the Alpha-8MR (@ 1.52) would be dreadful in a ported box but fine in a sealed box?

    Is that the idea?

  15. ESP-LTD


    Sep 9, 2001
    Negative. low numbers = low Qts ; as they appproach 1 they are getting higher. A driver with a Qts between .5 and higher is considered a sealed box candidate.

    "Fine" might be an overstatement. It would be lousy in ported box. It might just be a really cheapo speaker that isn't built for bass response.

    You have the concept indeed. It would be great if there was just a single parameter that made speakers sound good, instead of a dozen or more.
  16. No, ESP, I've not got the concept......I'm sure I haven't.

    Let me go over it again so you can correct me.

    The higher the Qts number, the higher is it's Qts: a driver with a Qts of (say) 1.0 has a higher Q than one of (say) 0.5? That means it has a higher total Q and that makes it more expensive? These speakers live best in a ported enclosure where the cab is tuned to Fs?

    Low Q drivers are best suited to sealed enclosures?

    But Bruce dismisses the Mac Fire 250 driver because of it's high Qts. Surely that's exactly the driver he should be looking at because of it's high Qts because they like ported enclosures. No, that just can't be right............... Perhaps it depends on what is meant by, 'high'? No, that can't be sensible, either.

    The Mac Fire 250 has a higher Qts than a fair number of the Eminence range. Does that make those drivers even more useless that the Mac Fire? No, that can't be right, either.

    I'm sorry, I just really don't understand this AT ALL


  17. And then, of course, there's, Group Delay.....

    With the cab sizes Ive got in mind, and with GD being the dreaded thing it apparently is, surely I'd be better off building a sealed cab for my Kappa 15LF? WinISD shows little difference in the SPL graph for my various combinations of cab.

  18. ThunderStik

    ThunderStik Guest

    Jun 25, 2001
    Claremore OK.
    Esp, John,

    I could be wrong but I believe some of the statements you made earlier are false.

    quote from ESP
    "High Qts usually means big magnet and voice coil which leads to tight motor control over the cone.

    Low Qts usually means smaller magnets and voice coils and the cone can flop around a lot based on it's intertia; starting and stopping are not tightly controlled by your amp.

    High Qts costs money."

    High qts usually means a smaller magnet and less control.
    Low qts is usually the sign of a higher quality driver and evidence of this can easily be seen by the BL factor which is the force of the magnet motor. Usually the "better" drivers will have a lower qts and a bigger magnet and a higher bl. This is what costs money , bigger magnet gives more control, sometimes a better suspension, things like lightweight cones but just as stiff as a heavier cone . These are what cost money.
    Qts = cone control (combination of electrical and mechanical), the lower the number the better control and it takes better components to get better control.

    Edit; brain got ahead of my fingers.
  19. ESP-LTD


    Sep 9, 2001
    I've had that problem recently .... I edited my original post to be accurate.

    I learned the "Q" stuff long ago with radiio circuits, and in that context High Q or "High Quality" was generally desireable and expensive to achieve. I was 180 degrees out-of-phase since LOW Qts is desireable and expensive in this context.
  20. ESP-LTD


    Sep 9, 2001


    NO. It has a higher Q and is therefore less expensive.

    High Qts drivers live best in sealed boxen. Low Qts drivers are happy in a poertd enclosure tuned to Fs.

    You are quoting me correctly and I said it backwards in my original 5:00 AM post. Low Qts drivers are best suited to ported enclosures.
    I made my original long post WAY before the coffee hit at 5:00 AM and my wires were crossed. I have since corrected the backwerdity. You have the concept correct from what I have read; I just explained it backwards.

    The only "confusing" part (besides my earlier post) is that a driver that we would consider to be of higher quality (no caps here) is a driver with a Low Qts.