Boomy Bass vs. Cabinet Volume

I'm currently working on building and designing my first pair of tower speakers. It uses pretty cheap drivers because i'm in college and for all intensive purposes it will be a party system (the secondary purpose is to show my dad how easily outclassed Bose is because he has a tendency to buy into brand names).
The drivers I'm using:
  • GRS 8PF-8 8" Paper Cone Foam Surround Woofer (8; 4 in each cab to retain 8 ohms)
  • Dayton Audio DC28F-8 1-1/8" Silk Dome Tweeter (2; 1 per cab)
I'm using a third-order cross-over 2400 hz; hand-made not prefab. I'm also using a zobel network on the woofers. The cab is going to be sealed.
My Questions:
  • First Question: What causes boomy bass (monotone; non-responsive sound; airy; muddy) in relation to enclosure size; an enclosure larger or smaller than the vas? (i've recently seen conflicting information on this and i'm new to this; feel free to throw in any other factors)
  • Second Question: Does the zobel network (resistors) need to be rated for the amount of power that the woofers will receive? Or does the zobel network receive less power than the woofer?
  • Third Question: Since the tweeter is only receiving a small portion of the spectrum (upper 3 octaves pretty much), what could I expect for overall power handling for the whole speaker collectively before I would risk damaging the tweeter? I realize this changes with the spectral distribution of each song, but just generalize.
  • Fourth Question: With said drivers, would it even be useful to use goodish crossover components? Or might as well I go bottom of the line (non-polar electrolytic capacitors, etc)?
  • Fifth Question: Will the woofers be over powering compared to the tweeter? The woofers have a lower sensitivity than the tweeter, but there are 4 per cabinet and I'm just assuming that to a small extent that will increase the effective sensitivity.
Any advice, suggestions or criticism welcome. I know there are cleaner speakers I could make for the money, but this just seems to fit my needs (and I love the sound of paper woofers). Also, ignore the specs that say the woofer is only good down to 55 hz. After reading many reviews, this speaker is apparently prone to a long break-in period but will get down to about 35 hz after some time.
 
Hi, maybe try finding a woofer with a lower Qts. With it that high you will have boomy bass unless the cabinet is the size of a refrigerator. Try and find one around .3 to .4, so the cabinet will be of reasonable size. That woofer will work best as an OB system. About the smallest cab you could get away with is around 6 ft^3 for four woofers, sealed.
 
Q1: a box either too big, or too small... to get a feel for this, input the parameters of your woofer into Unibox, and play with the box size & tuning to see what will happen.
For sealed boxes, usually a too-small box will cause a problem
Q2: Zobels are usually a waste of time
Q3: Why Do Tweeters Blow When Amplifiers Distort?
Q4: standard components are OK, use polyprop caps if you can afford then, but np electros are perfectly OK for the larger values
Q5:This depends on how you implement baffle step correction, usually you will need to pad the tweeters anyway
 

kouiky

Member
2009-06-18 4:42 pm
I completely agree with PeteMcK about undersized sealed cabinets. I have heard several boomy sealed speakers, I could name three great examples of famous brands from memory. To be descriptive of the boomy sound, the speaker will subjectively seem to exhibit a prominence in one frequency range or a strong sonic characteristic regardless of what song or bass type that is reproduced on them. Some types of boominess or mud are relative to the driver and its own distortion or reflections within the cabinet. A poorly braced and parallel sided cabinet will also add its own note.

If finances later permits, you could try an active biamp system. They pay for themselves by saving the builder from buying expensive crossover parts and then having to change values and start over again. I have used 30 cent electrolytic capacitors in series crossovers and could not sonically indentify a difference in direct comparison between them and expensive Mundorfs that reviewers and shill blogs were going wild over. My hearing is perfectly fine, I had a hearing test in November and have no attenuation. There are some possibilities here, as in a second or higher order filter it may make an audible difference. I 'm just sharing that info now for future reference. I cannot recommend spending any sums on Duelunds, Audio Note or other glossy caps, when in reality a $500 active crossover will outperform them every time, and is continuously adjustable and transferable between speakers.

Just pay attention to cabinet bracing, internal displacement, stuffing. For the purpose and budget, I would maybe even consider 2x GRS 12PF-8 12" Paper Cone Foam Surround Woofers at just over $15 each or a 15" paired to a top mounted fullrange driver with a suspended disperser cone to make them largely omnidirectional. One of the causes of blown speakers at parties is being powered by an over driven amplifier, which comes down to it not being "loud enough" (by some party goer's self conviction) across the frequency domain in all directions.
 
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Speaker Design Works
And very unlikely to be able to make a better party speaker.
You know I like to agree with you when I can but this is where we have to part. This looks like a speaker you might actually enjoy listening to, no?

To me, a party speaker, and I own a few, doesn't resemble this. This could sit in your livingroom with nary a complaint from the Mrs. not to mention sound ok at lower volumes.
 
Yeah, back in the '60s till 1980 when I was helping/making HS, fraternity and off campus party systems, these would have been nice dorm room/efficiency apt. speakers, so when I read this, figured that since then increasing state/Federal noise abatement laws, political correctness had put a serious crimp on partying outside commercial venues.

GM
 
You're not supposed to enjoy listening to music at a party?

Of course you are but I was referring to more of a critical listening type speaker in that this seems to fit the bill more so than a traditional party speaker. It's like the difference between a luxury sports car and a 4X4. You enjoy the ride of the luxury car more and more often but you also enjoy the 4x4 when the time is right.
Party speakers have big air moving capability to give you the gut feeling. They don't worry about that silly octave at either end of the scale, they're about muscle. They start sounding good up around 100 dB and won't let you down if you take it further. If you spill a drink on them you worry about that in the morning. They're big enough and strong enough that if a girl wants to sit on them she can. Guys will use them for a table for...

...well that's for another time. I hope I clarified my thoughts on what a party speaker is to me.
 
I think I'd consider going 3-way, with dedicated amplifiers for the woofers.

When it really comes to it, the bass amp can clip. It doesn't matter much: the inductance of the big voice coils means the HF mush won't destroy anything - the delicate mids and tweeters must have their own amp that should not clip. The DC component of a clipping amplifier is short-term, and won't damage the woofers any more than more power from a bigger amplifier.

Give it a decent 10" or 12" per side, 6" mid, tweeter.

The mid will need its own enclosure, but it can be small. The tweeter can be either a 1" dome (smaller sacrifices power handling) or a compression driver with a small horn. Ensure it'll hit ~4kHz with plenty of power handling, either way.

Amplifier can be one of those 4x100w boards, or have a look on eBay for Studio Amplifiers - you can often get them cheap used.

It'll probably come to $3-400, but it'll do the job and then some. It shouldn't die when abused, either. That does depend on your woofer and amplifier choice - don't cheap out there.


I'm at university (similar to the thing Americans call college, IIRC), and trust me: no matter how big you build it, someone will *always* find out how loud it can actually go, and then push it a little past. People listen for the THD rise and set the volume accordingly. "Full blast" on a small portable iPod dock isn't anywhere near as loud as a proper stereo also driven to "full blast", but I'd bet the distortion components look similar.

Chris