Ported box too small?

[ghukill]

I'm attempting to build twin 12" subs to compliment the MTM's I finished a few months ago. They will be used used for music 80% of the time and HT 20%. I'm trying hard to limit the box volume to 2ft^3 + change yet really like the looks of the new 8Ohm Dayton RS 12HF. WinIsd suggests an ideal ported box of 6.5 ft^3 tuned to 19Hz which is way too big and lower then I really need. When I push the box size to 2.1 ft^3 and tune to 25Hz, it creates a response with a slow +2dB hump centered at 45Hz and a -3dB at ~26Hz. I've only built a couple ported boxes before, always giving in to the suggested volume and being pleased with the result. Any insight or suggestion as to how the 2.1 ft^3 alignment will sound? I want to avoid a muddy, boomy, cheap sounding sub but would like the efficiency of a ported box. Would I be better off going back to a sealed design or swapping the RS12HF with an RS12HO at the expense of 5-10Hz at the bottom end?

Advice would be great

[fastbike1]

What drivers? I don't find an RS12HF or RS12HO in the catalog.

RSS315HFA maybe? It's 8 ohm. ALso, why an 8 ohm sub? NOt using a plate amp?

[johnnyrichards]

What drivers? I don't find an RS12HF or RS12HO in the catalog.

RSS315HFA maybe? It's 8 ohm. ALso, why an 8 ohm sub? NOt using a plate amp?

I suspect since he is building twins, he might be using one amp for both drivers.

[Chris Roemer]

I'm attempting to build twin 12" subs to compliment the MTM's I finished a few months ago. They will be used used for music 80% of the time and HT 20%. I'm trying hard to limit the box volume to 2ft^3 + change yet really like the looks of the new 8Ohm Dayton RS 12HF. WinIsd suggests an ideal ported box of 6.5 ft^3 tuned to 19Hz which is way too big and lower then I really need. When I push the box size to 2.1 ft^3 and tune to 25Hz, it creates a response with a slow +2dB hump centered at 45Hz and a -3dB at ~26Hz. I've only built a couple ported boxes before, always giving in to the suggested volume and being pleased with the result. Any insight or suggestion as to how the 2.1 ft^3 alignment will sound? I want to avoid a muddy, boomy, cheap sounding sub but would like the efficiency of a ported box. Would I be better off going back to a sealed design or swapping the RS12HF with an RS12HO at the expense of 5-10Hz at the bottom end?

Advice would be great

MOST rooms seem to have a "mode" (or node) right around 40 Hz or so. IMO, THAT coupled with a 45Hz hump would NOT be easy to listen to.

I DO like the looks of the HO12 in 2.1 cf tuned to 25 Hz. An F3 in the mid to low 20s should be good for ANY application.

Chris

[Jethro]

With a Qts of .53, the 8-ohm 12HF really is not a good candidate for a ported box, especially not one that's 2 ft^3 -- I don't think you would like the results. If a ported 8-ohm Reference sub is what you want, then the RSS315HO-44 is a much better choice: http://www.parts-express.com/pe/show...number=295-467 (and it's on sale)

[Brent_S]

MOST rooms seem to have a "mode" (or node) right around 40 Hz or so. IMO, THAT coupled with a 45Hz hump would NOT be easy to listen to.

I DO like the looks of the HO12 in 2.1 cf tuned to 25 Hz. An F3 in the mid to low 20s should be good for ANY application.

Chris

Use one of AESpeakers PR15-1050s to do the tuning, no extra weight required and avoid the hassle of trying to fit a suitable port in that small of a box.

Actually, this is one of my future projects...currently use a 315HO sealed in my living room system, but have a PR15-1050 in the parts closet waiting for its turn to come up. :-)

-Brent

[ghukill]

Thanks for the suggestions.

The drivers I considered were (to answer the initial reply)

http://www.parts-express.com/pe/show...number=295-466
and
http://www.parts-express.com/pe/show...number=295-445
plus a few others, titanic III etc...

I leaned away from the HO reference series just b/c of the higher FS. Its been in my head for years now that a rule of thumb was avoid tuning the box/port lower then the FS of the driver (for driver mechanical control).. If I'm wrong on that then the HO series looks like the solution.

One additional question then. I've been looking at using dual Bash 500W plate amps b/c they seem like a good $/watt, are on sale (I'm a sucker for sales) and get decent reviews. They are rated @ 4Ohm and if I tried this new HO speaker:
http://www.parts-express.com/pe/show...number=295-467
I'm probably safer wiring it as an 8Ohm load, but that cuts the output of the amp. Would a bash 500 push one of these drivers wired in Series or is that a no-no? I can always cough up the $$ for a single Dayton 1000 watt rack mount amp and wire both speakers together as a single 4Ohm load.

Thanks again for the help everyone

[Chris Roemer]

Thanks for the suggestions.

The drivers I considered were (to answer the initial reply)

http://www.parts-express.com/pe/show...number=295-466
and
http://www.parts-express.com/pe/show...number=295-445
plus a few others, titanic III etc...

I leaned away from the HO reference series just b/c of the higher FS. Its been in my head for years now that a rule of thumb was avoid tuning the box/port lower then the FS of the driver (for driver mechanical control).. If I'm wrong on that then the HO series looks like the solution.

One additional question then. I've been looking at using dual Bash 500W plate amps b/c they seem like a good $/watt, are on sale (I'm a sucker for sales) and get decent reviews. They are rated @ 4Ohm and if I tried this new HO speaker:
http://www.parts-express.com/pe/show...number=295-467
I'm probably safer wiring it as an 8Ohm load, but that cuts the output of the amp. Would a bash 500 push one of these drivers wired in Series or is that a no-no? I can always cough up the $$ for a single Dayton 1000 watt rack mount amp and wire both speakers together as a single 4Ohm load.

Thanks again for the help everyone

Vented boxes usually work better with unboosted amps (like the SA240). The thing about the B500, is that its boost is near 40 Hz (about +2dB?) which can emphasize the boom from a room mode. OTOH, the B300's boost is less (+1dB?) and is a bit lower in frequency.

If I was picking, my choices would be 1st - SA240 w/OUT boost, B300, and lastly the B500.

Also, you CAN alter 2 on-board resistors on the Bash amps to modify the boost curve (although I've never personally done this).

[Brent_S]

To add to what Chris said. The BASH500 also has it's rumble filter high pass at ~30Hz by default. For subwoofer use, you will *want* to adjust those two resistors to lower it to something like the more reasonable 18Hz found in the BASH300/SA240.

Unlike Chris, I would choose the BASH300 over the SA240, if for no other reason, due to the xover bypass. The SA240 turned to max is probably high enough to not cause a problem with the typical 80Hz xover point, but I prefer knowing it's out of the way. I have used both the SA240 and BASH300, FWIW.

The BASH300 has plenty of muscle for a 315HO, even in my sealed alignment, IMO. IIRC, the models I did for the 315HO/PR15-1050 with the BASH300 showed it capable of 105dB at 1m ground plane from 20Hz up. Figure another 6-10dB when you put it in a room.

Just messing around the other day with "Iron Man 2"...was seeing 100dB peaks (uncorrected Radio Shack analog spl meter) on the bass hits in the demo scenes (opening fireworks, fight at the house, and final battle)...taht was not the limit of the system, but my own threshold of comfort. Measurement distance was 14' (7' or more to nearest wall), sub is midwall, room is 22'x20'x9' with a two story foyer/open staircase/catwalk where one wall should be...sub is 1 ft^3 sealed 315HO with a stock BASH300. YMMV.

-Brent

[bvn]

That's what the Thiele-Small model is for.
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It will tell you if the enclosure size is inappropriate and whither ported or sealed is likely to give better results. As regards, ported designs, I've been most happy with 2nd order Chebychev pass-band designs.
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I've used it for decades (in the form of a spread sheet) and the actual results are fairly close. Tweaking is less labor intensive than rebuilding :-)
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PE is super good about providing the T/S parameters for it's drivers. I've found their info very helpful in driver selection and in enclosure design.