Where do I start?

[simon5]

Hi owdi

It's nice to have opposite opinions

I'm against bass boost to fill low end, you lose amplifier headroom.

Also you run much more power than needed to achieve the same SPL at the same frequency with a ported and/or passive box so I'm not sure that you will achieve lower distortion when playing loud, especially when you run into the bass boosted frequencies.

I agree with you about the group delay, sealed is better. But then, if you tune under 20 Hz, group delay isn't that problematic.

I agree with you also on the push-pull configuration, lower distortion on small level signals, but when you push all the power needed to achieve high SPL, I'm not sure that you will achieve lower distortion since push-pull is power hungry if we talk about the same thing.

Lower price, I agree with you also. But again, he has alot of money to spend, it seems. I tend to suggest a project to use all the money or to exaggerate.

I agree that you get high power handling also, but do you get higher SPL ? Do you get lower distortion at high SPLs ?

Your suggestion is very good, to me it would be an excellent sounding subwoofer for moderate volume listening, with very low distortion.

I think my idea is better for high volume listening, with low distortion.

What do you think ?

[ScottG]

Originally posted by twowheeled

Box size is a non-issue I don't mind having a large cabinet.

THAT really should have gotten the attention of others.

Consider an "IB" design (aka infinite baffle).

The cheapest driver is the Dayton IB at parts express.

Then there is the new IB driver from aespeakers.

Finally, Rythmik audio should have an IB servo driver solution soon.

[owdi]

Originally posted by simon5
Hi owdi

It's nice to have opposite opinions

I'm against bass boost to fill low end, you lose amplifier headroom.

Also you run much more power than needed to achieve the same SPL at the same frequency with a ported and/or passive box so I'm not sure that you will achieve lower distortion when playing loud, especially when you run into the bass boosted frequencies.

I agree with you about the group delay, sealed is better. But then, if you tune under 20 Hz, group delay isn't that problematic.

I agree with you also on the push-pull configuration, lower distortion on small level signals, but when you push all the power needed to achieve high SPL, I'm not sure that you will achieve lower distortion since push-pull is power hungry if we talk about the same thing.

Lower price, I agree with you also. But again, he has alot of money to spend, it seems. I tend to suggest a project to use all the money or to exaggerate.

I agree that you get high power handling also, but do you get higher SPL ? Do you get lower distortion at high SPLs ?

Your suggestion is very good, to me it would be an excellent sounding subwoofer for moderate volume listening, with very low distortion.

I think my idea is better for high volume listening, with low distortion.

What do you think ?

Even with bass boost, I don't think the dual sealed subwoofer would require a larger amp than the PR subwoofer.

This is a chart comparing a vented*** vs. dual sealed alignment. 4 cu ft. using the Dayton 12" HF, @ 1 watt.



The vented alignment is more efficient between 14hz and 40hz, while the sealed alignment is more efficient above 40hz.

An interesting thing to ask is what happens when you EQ these two subwoofers so they have equivalent FR (using that bass boost). Below 40hz the vented sub will have the advantage, with less power required for a given SPL, and lower excursion. Above 40hz the dual sealed setup will have the advantage.

Things get murky when you feed the sub music instead of test tones. Music, even synthetic, is filled with harmonics. These can be just as loud as the fundamental. At 30hz the vented alignment has the advantage, but when you factor in the 60hz and 90hz harmonic the sealed could be more efficient. I haven't taken the measurements or done the math, but my guess is power requirements between these two subwoofers would be pretty even when it comes to playing music.

If the power requirements are equivalent, then you should base your decision on other factors, such as distortion and price. The dual sealed push-pull wins in both categories, which is why I recommend it over a PR. It should also be easier to construct, and easier to tune.

***I used vented because I'm lazy. It's easier than modeling a PR and results are very close, with PR being slightly less efficient :-)

Dan

[simon5]

Nice discussion, you have a point with harmonics. I guess it depends on the kind of music we listen to, then.

I did your same experiment with WinISD Pro alpha.

I entered 2nd order peaking highpass 6 dB bass boost filter centered at 20 Hz. Now your design is equal with vented from 30 Hz and under. Over 30 Hz your design is louder from a 1 W imput.

Problem is excursion. Your design will go in overexcursion at 20 Hz when the amplifier is outputting 125 watts because of the bass boost, the real power usage at 20 Hz will be near 310 W according to apparent amplifier power load in VA in WinISD.

Vented enclosure OTOH will take 330 W before going in overexcursion at 30 Hz and under 18 Hz.

We now have very similar power handling and significantly higher output for the vented enclosure, except if the signal doesn't contain low frequency, then sealed wins.

Maybe we should use a better filter like Linkwitz transform or param EQ. Since we get lower SPL from sealed, maybe we would get lower distortion from vented at same SPL.

I agree with you on price like always, my idea is expensive. I also agree about ease of construction and ease of tuning.

Here's the results with similar "apparent" power imput 310 W for sealed and 330 W for vented before overexcursion.

[owdi]

I think we pretty much agree on everything, but have different tastes :-)

I don't think an LT is required for the sealed enclosure. With room gain, about 4db boost at 20hz should flatten things out and satisfy the OPs requirements.

While you're already modeling things in WinISD, try a dual vented Dayton RS 12" HF in 4 cu ft, with two round 4" x 36" ports. If you could fit the ports, and align the drivers push-pull, could be an awesome sub.

Dan

[judtoff]

I would recomend passive radiators as well. A tapped horn would be great too. Oh and would nt only 1 18" radiator be needed

[simon5]

owdi yeah your idea ain't bad, but to better match room gain, I would prefer 8 cu.ft with those 2 ports but 28 inches long.

Would be easier to fit also! We also get a low end bonus...

That's because IMHO room gain is more like 3 dB/octave in a "typical" (if we could say that...) drywall room. I tend to design subwoofers around that room gain curve.

You seem to be well versed into push pull subwoofers, can you show one of your creations ? I would like to see one, thanks !

[Andersonix]

Originally posted by ScottG
Consider an "IB" design (aka infinite baffle).

The cheapest driver is the Dayton IB at parts express.

Then there is the new IB driver from aespeakers.

Finally, Rythmik audio should have an IB servo driver solution soon.

It's strange how many boxes people try building before they come around to just cutting a hole in a wall or ceiling and sticking in an IB woofer (or 4). IB should always be the first thought before resorting to boxes...

What do people think of Parts Express Dayton HPSA1000-R 1000W Rackmount Subwoofer Amplifier (pn 300-810) for $400? It has a proper adjustable phase control knob, parametric EQ, and plenty of power.

[planet10]

I don't know why a push-pull woofer of any sort would take more power.

With a lot of the more linear woofers today push-pull doesn't give you all that much.

Some more seni-random thots....

When i am looking at doing a woofer i prefer to make a push-posh woofer as it takes a lot of the box out of the coloration equation.

I'm not a big fan of BRs, boxes with PRs are like BRs with an extra resonance to deal with.

If you are going to go sealed, the box should be big enuff to be low Q (0.5-0.58)... tie it in with room gain and it will go low. A little judicial boost if needed isn't a bad thing. A really big box turns into an IB ... if you have a large space adjacent to your listening room, i'd consider that the way to go.

My real preference is for quarter-wave or aperiodic boxes. A QW that goes low will almost rival an IB in terms of size... i have designs for a CSS SD12 BIB (see attached) & a TL, and some data for a monster or 2 with a pair of SDX15s

To my mind the best way to move alot of air is to use a big woofer, but you have to trade that off against the smaller woofers better top end, which help with integration to the mains.

At the moment i am working with the SDX7 -- only good to 25 Hz or so thou.

dave