woofer me

[Dave Jones]

I'm thinking about slapping a Peerless 830500 into a pre-fab box and calling it my subwoofer. It will be used with a fairly low crossover point. Plus, I'm sort of fixated on the idea of a Qtc of 0.5. Don't ask me why. I'll be using it in conjunction with a pair of Lynn Olson Ariels in a moderate size living room. I won't be playing it at volumes that will make the neighbors call the police. Is the Peerless the best choice?

The published T/S parameter Qts=0.2 along with Qtc=0.5 yields a closed box size of .94 cubic feet (26.5L).

Given that (unlike you all) I am only a borderline genius, and I don't know what I'm doing, a whole bunch of questions come to mind.

Are there pre-fab boxes available in sizes other that 1, 2, and 3 cubic feet?

About how much volume does a 12" woofer displace? (For that matter, how about other sizes?)

I've read that stuffing can increase apparent box volume "by 25%." Does that mean to figure the unstuffed box at 4/5 the size you want? If so, what kind of stuffing and what density?

Is there room in a 1 cu ft box for a plate amp? For example, look at this one:

http://www.partsexpress.com/pe/show...44&St3=61577777&DS_ID=3&Product_ID=9388&DID=7

If I figgered right, it displaces .157 cu ft (4.43L). Using the Peerless, my target volume is .94*(4/5) = .752 cu ft (21.2L), which would leave .09 cu ft (2.55L) for the woofer. It looks as though the plate amp and woofer might both fit in the 1 cu ft box. Yes? No?

Finally, what kind of amp to use? I have a Richter Scale Series III [ http://www.audiocontrol.com/homeaudio.htm ], so I could use that with an external mono amp. Or I could use a plate amp, perhaps with some built-in EQ. Or I could use the Richter Scale for EQ only in conjunction wity a plate amp. If I get a plate amp, should I get one with a 6 dB boost at 30hz, or a flat one? Or should I spring for the expensive "500 Watt" amp (273 Watt -> 8 ohm) at Parts Express with its cool features?

http://www.partsexpress.com/pe/show...&St3=61577777&DS_ID=3&Product_ID=124777&DID=7

Would it displace too much volume?

Other plate amps? How about an external mono amp? -- Any suggestions for a brand/model?

Finally, finally, if you were wanted a super clean and tight subwoofer to go with a pair of Lynn Olson Ariel speakers, what would you do?

Whew!

 

[Timn8ter]

How about this one. It impressed a lot of people at T.H.E. Show. You can almost see it in this picture behind the left speakers.

 

[Dave Jones]

I can now answer one of my questions. I found a spec for the Shiva 12" saying it displaces 3L (.106 cu ft). Supposedly, other typical 12-inchers would measure similarly.

 

[Dave Jones]

ttt

 

[mikee12345]

To move air is one thing
To move air LINEARLY is another!
=for 20hz ish = multiples of shiva/dpl12 etc..It simply wouldnt satisfy my mind knowing they are moving at 14mm excursion(oneway) regularly.

Id then measure the Sinewave quality and cosine shaped sine bursts...and transient response 'blips'

Plus, I'm sort of fixated on the idea of a Qtc of 0.5. Don't ask me why

i wont ask why,because i know Qtc=0.5 is good. The problem is\how different does it sound from Qtc=0.707,and what box volume does it require.

Finally, finally, if you were wanted a super clean and tight subwoofer to go with a pair of Lynn Olson Ariel speakers, what would you do?

basshorn. Or other expensive quality transducer....or multiples of cheaper ones
🙂

 

[SY]

Given the realities of room gain, a 0.5 Qtc isn't a bad idea, especially if the driver is coupled closely to the floor. I haven't personally tried the Shiva, but heard good things. I'm VERY pleased with the closed box I built for a buddy of mine, using an NHT 1259, mounted near the floor, with a Qtc about what you're aiming at. We used separate subs for each channel. You won't get insane SPLs from it, but it plays plenty loud (as loud as the near-SOTA-NHT3.3s).

For an amp, forget the frills and features (you can build them into the crossover- you ARE using an electronic crossover, right?). You just want POWER.

 

[chrish]

I am also looking at building some sub-woofers to go with my newly constructed ariels. Have you seen this page, http://www.nutshellhifi.com/ME2txt.html#me2

This is what Lynn Olson recommends to accompany his ariels and is what I am probably going to build.

Good luck.

Chris

 

[Dave Jones]

I am also looking at building some sub-woofers to go with my newly constructed ariels. Have you seen this page, http://www.nutshellhifi.com/ME2txt.html#me2

This is what Lynn Olson recommends to accompany his ariels and is what I am probably going to build.

Good luck.

Chris

Yes, I've seen that. I hope not to use that many drivers. I don't need enormous amounts of SPL.

 

[Dave Jones]

Given the realities of room gain, a 0.5 Qtc isn't a bad idea, especially if the driver is coupled closely to the floor. I haven't personally tried the Shiva, but heard good things. I'm VERY pleased with the closed box I built for a buddy of mine, using an NHT 1259, mounted near the floor, with a Qtc about what you're aiming at. We used separate subs for each channel. You won't get insane SPLs from it, but it plays plenty loud (as loud as the near-SOTA-NHT3.3s).

For an amp, forget the frills and features (you can build them into the crossover- you ARE using an electronic crossover, right?). You just want POWER.

The NHT 1259 has a published Qts of 0.445. How big is the box you built?

In answer to your questions, yes, I will use an electronic crossover. I might use a Richter Scale III that I have, or I might use a plate amp.

 

[SY]

I'll check the volume when I get home. It was pretty big, hitting a Q = 0.577 target once it was stuffed. More like an infinite baffle than acoustic suspension, that's for sure.

 

[Dave Jones]

Here's another idea.

How about a Shiva Mark III in a 3 cu ft box? That would be real close to Qts=0.5 with minimal stuffing. The makers say 3 cu foot with 32 oz of polyfill has an in-room F3 of 27Hz. They also list a ported 3 cu ft alignment with an in-room F3 of 23Hz. I could build it with a port fitted with a removeable cover. The only question would be how much stuffing to put in the thing.

I've got space in the living room for a 3 cu ft box, so I think this is a better idea than trying to jam the Peerless into a 1 cu ft box.

 

[Dave Jones]

Yes, I've seen that. I hope not to use that many drivers. I don't need enormous amounts of SPL.

Following up on my answer (too late to edit)...

The only thing that gives me pause is this quote from Lynn Olson:

The second reason? Most well-reviewed "audiophile" drivers have magnetic circuits that are no better than consumer-grade; it just isn't a priority, since hi-fi magazines don't care much about IM distortion in speakers. In the real world, though, IM distortion is a very important consideration. Few bass drivers have magnet systems optimized for low IM distortion; the only ones I know of are expensive professional studio monitor drivers from JBL, Altec, and TAD, and the Scan-Speak drivers for consumer use.

That was written a few years ago. Perhaps the situation has improved. I wonder if the drivers I am considering have low IM distortion figures. Anyone know?

 

[Dave Jones]

Here's another idea.

How about a Shiva Mark III in a 3 cu ft box? That would be real close to Qts=0.5 with minimal stuffing. The makers say 3 cu foot with 32 oz of polyfill has an in-room F3 of 27Hz. They also list a ported 3 cu ft alignment with an in-room F3 of 23Hz. I could build it with a port fitted with a removeable cover. The only question would be how much stuffing to put in the thing.

I've got space in the living room for a 3 cu ft box, so I think this is a better idea than trying to jam the Peerless into a 1 cu ft box.

Dang it! I made a math error. I forgot to subtract a 1. A Shiva in a 3 cu ft box will not be right at Q=0.5. ... and it's too late to edit or delete the post. Sorry.

 

[454Casull]

Why not use an AA Tempest? It's only $25 more and goes lower louder.

Also, you can put the plate amp on the outside of the enclosure.

 

[Dave Jones]

Why not use an AA Tempest?

... because I want a Q of around 0.5. In a 3 cu ft box, the Tempest would have a Q of 0.84.

There just don't seem to be any low Q woofers other than the Peerless and some 8 and 10 inchers from Scan Speak. If someone knows of others, please speak up.

 

[454Casull]

Really that averse to building your own box?

 

[SY]

Dave: The 1259 sub I mentioned ran about 8 cu ft.

I'd like to try that driver in a TL.

 

[kelticwizard]

Dave:

Well, if you want to get creative, two TangBand 8" subs put into a 26 liter enclosure, (26 liters for the both together), will yield a Qtc of 0.5 and and an Fc of 46 Hz, assuming the published Thiele-Small numbers hold up.

That is less than 1 cu ft.

http://www.tb-speaker.com/detail/woofer/w8-740c.asp

You can use the money you save by buying these to purchase another plate amp to drive the second woofer, since these both are 4 ohms and plate amps work best into 4 ohms. The second plate amp will boost the sensitivity up to 90 dB as well.

Take a 1.5 cu ft enclosure which i believe is available, hook the two amps up and put bricks into it to make up the extra space.

I don't know if an Fc of 47 Hz is what you want, though.

 

[catapult]

I'd go for the Peerless in a sealed 2 cu.ft. box. That's only a little bigger than the 50 liters Siegfried Linkwitz used in his Thor sub and a plate amp would take up most of that. Sealed subs are pretty insensitive to minor changes in box volume and room effects have a much greater impact on the frequency response.

http://web.archive.org/web/20030606010005/linkwitzlab.com/thor-intro.htm

Edit: or, if one is available, a stuffed 1.5 cu.ft. box should be fine. Maybe even better. SL doesn't like stuffing but I do. It will eliminate the 300Hz null he gets due to box dimensions. I'd even stuff a 2 cu.ft. box and use EQ to adjust the frequency response.