Speaker Newbie Question

[TubeHead Johnny]

Hello Folks!

A few years back, I built a pair of mid-sized, ported speakers with the Dayton DC300-8 12" Classic Woofer. I've been very happy with the end result, with the exception of the bass response below 50Hz. I was thinking about replacing the woofer with the Dayton ST305-8 12" Series II Woofer. Here are the specs, starting with the original:


Dayton DC300-8 12" Classic Woofer:

Power handling: 80 watts RMS/115 watts max * Voice coil diameter: 2" * Voice coil inductance: 1.80 mH * Impedance: 8 ohms * Re: 6.6 ohms * Frequency response: 28-2,500 Hz * Magnet weight: 30 oz. * Fs: 28 Hz * SPL: 92 dB 1W/1m * Vas: 5.11 cu. ft. * Qms: 2.94 * Qes: .42 * Qts: .37 * Xmax: 4.3mm * Net weight: 6 lbs. * Dimensions: Overall Diameter: 12", Cutout Diameter: 11", Mounting Depth: 5-1/4", Magnet Diameter: 4-3/4", Magnet Height: 1-3/8".


Dayton ST305-8 12" Series II Woofer:

Power handling: 275 watts RMS/380 watts max * Voice coil diameter: 2-1/2" * Voice coil inductance: 2.30 mH * Nominal impedance: 8 ohms * DC resistance: 5.7 ohms * Frequency response: 27-2,000 Hz * Magnet weight: 56 oz. * Fs: 27 Hz * SPL: 92 dB 1W/1m * Vas: 5.70 cu. ft. * Qms: 11.72 * Qes: .35 * Qts: .34 * Xmax: 8.0mm * Net weight: 15 lbs. * Dimensions: Overall Diameter: 12", Cutout Diameter: 11", Mounting Depth: 6", Magnet Diameter: 6-1/8", Magnet Height: 1-7/8".

Now will this new woofer dramatically improve the bass, or is it just not worth it? I've got a tube amplifier that puts out 60 watts per side.

Thanks, Johnny

[MadMutt]

So you have the specs of the two drivers.
Why not model them in >insert favorite software here< and see for yourself.

[sdclc126]

What does the rest of your speaker system consist of? I'm guessing they are 3-ways? If you're using a decent sized cone midrange, consider using true subwoofers such as the Dayton SD315-88, or just keep your Classics and build a single separate sub.

[PeteMcK]

There probably won't be much difference between them.
What size box do you have your current woofers in?
These need a fairly large box to get down low.

Madmutt's right - download WINISD PRO and start modelling....

[BHTX]

If you're really satisfied with rest of the speaker, besides low frequency extension, I'd suggest redesigning the cabinet and using a Series II 15, tuned properly, powered with a high current solid state amplifier. Several good SS amps of sufficient power and quality can be had for $300 or less, (adcom 555 for example...i have one laying around with no use for it at the moment, but it works very well for powering woofers like this). With an amp like that, along with the nearly unbeatable bargain of the Series II 15, plus the fact that a decent active xo can be had for VERY cheap (especially if you can do 4th order), it won't cost all that much. Not sure if you're using an active or passive xo though. If active and you can get by with using the same xover points, great. Regardless, I'd seriously consider active for the woofer, and use a separate amp for it, using your tube amp for the mids up. As for the 12" Series II, it's more sensitive, but definitely doesn't posess a massive amount of low frequency extension to brag about either. Won't find an 8 ohm twelve with that kind of sensitivity that extends much lower tho. MAD1259 could even be a possible option too if you wanted to go that route, but it's difficult to say without knowing anything else about the rest of the loudspeaker you built. If you don't want such a wide cabinet for the 15 or can't deal with the possible effects that the wider baffle could have on the rest of the system, redesign the enclosure as necessary to accommodate that diameter without allowing its appearance to seem so intrusive. Design for a larger baffle for the 15 on bottom, with the mid + tweet in a smaller separate enclosure on top if you have to. Several ways to go about this type of thing. It'd be best to know the rest of the design though, before taking any recommendations very seriously.

[TubeHead Johnny]

I have limited space, so a sub would not be practical. The boxes are 28" X 17" X 10". They're old EPI's.....very nicely built, with 3/4" MDF and lots of bracing. Very heavy. I really don't have the room or proper tools to make my own cabinets. For the most part I build amps but not much else. They are "2 1/2" way....the 12" woofer in parallel with a Dayton 5 1/2" aluminum cone woofer. The tweeter is a 1 1/8" dome. The crossover is a 2 way prefab unit, also made by Dayton. Like I said before they sound very good, I just need a tad more extension and punch.

~~~John~~~

[pulexirritans]

Swapping out the woofer will not produce any noticeable difference since the specs (fs, qts and vas) on those drivers are essentially same. The st-305 would actually give you slightly less bass than your current woofers.

If you want thx movie style bass you need to get different woofers OR make your boxes larger. With an giant 6cf box you could get 30hz @116db for the pair, which is very respectable although not very practical.

If you just want to listen to music these woofers should be able to produce great bass. You may think you want deeper bass extension but what you may actually be looking for (without knowing it) is some bass boost. Shortening your bass port will give you more bass in the 45-150 hz range without sacrificing extension.

A 3 inch diameter by 2.75 inch long port should give you +3db ripple. If your port is 4 inches then try a 6 inch length. (btw some speaker dorks would say this is blasphemy, but I say it will give you nice warm bass)

If I were you I'd also ditch the parallel woofer setup and get a proper 3 way crossover and replace the midrange with this part:

http://www.partsexpress.com/pe/showd...number=295-301

Your current midrange starts breaking up at 1.5k and the efficiency is too low to match the woofer. Make a 2nd order 3 way crossover with frequencies of 300hz and 2000hz (these frequencies are a little close for a 3 way but it should be OK) For the lowpass portion of the 2000 hz crossover make it 4th order to compensate for the rise of the woofer between 2k and 4k. You can calculate those values here:

http://www.mhsoft.nl/spk_calc.asp#crossover

Also, add a 7 ohm resistor in series to the tweeter (but before the crossover) to match the efficiency of the midrange and woofer. Also,
reverse the polarity of your midrange. You can save money on your crossover by using electrolytic caps in the bass section (omg, the horror)

[TubeHead Johnny]

Now correct me if I'm wrong. The ideal box size for this particular speaker is 5.11 cu ft.? Also, wouldn't shortening the port make it boomy? It's 4.5" now.

~~~John~~~

[TubeHead Johnny]

It's a 3" diameter port. I cut it down to 3" long and there's a slight difference. Now will widening it to 4" have the same effect? I don't want "one note bass" that's heard in so many car subs these days. That drives me nuts!

[Norcad]

Hello
I do understand that you're unhappy with the bass in this speakers. But of course there is some tricks that will help.

1. If 28x17x10" is the external dimensions of the box, its to small. If this is the internal dimensions, then its perfect

2. You are using a 2way crossover, with the mid and bass in paralell, thats not good.
a) If your "lucky" the mid and bass are in phase, and you get a boost in the midbass, and this will sound likes theres no low bass. If your "unlucky" the mid and bass is out of phase, and this sucks out the midbass almost completely. The easiest thing to do, is to try and turn the phase of the bassdriver, just put on the cables on the driver the opposite way (+ to -, and - to +)
b) When the mid and bass are in paralell, there is no Baffle Step Compensation, and I'm sure this is the biggest problem. Baffle step is when the soundwave is longer than the width of your enclosure, then the soundpressure decreases with 4-6dB, and thats a lot!
When the enclosure width are 17", you will get a -3dB point from Baffle Step at aprox 280Hz.

So the best thing to do, is to build a new 3-way crossover, but that is rather difficult. Or you could use an surround receiver's sub out, with an external amp to your bassdriver. And set the xo frequency at 250-350Hz. Thats the easiest way.