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Discussion Starter #1
Another newbie in need of some advise. I am building a 1.2 ft sealed box with a Dayton RSS 315HF-4 driver. F3 seems to be around 35Db. It looks to be about -6 at 30Db.

These numbers may not be too acurate, cuz I don't have a clue about using the program. I am assuming they are close.

I noticed that the Dayton 240B adds 6Db at 30Hz. Would it be better to use this amp rather than the un-boosted 240?

This project does not allow for equalizers or more expensive amps.
 

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Discussion Starter #3
Thanks for responding. Wouldn't ya know that when I consulted my notes the size is 2.5 ft. This is close to the limit for space available.

In any case, the frequency drop off is correct and the question about which amp still applies.
 

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Discussion Starter #5
Thank you. I am not yet able to use/understand the better design programs so I don't have access to the information you have provided.

I don't see anything in the literature about a high pass filter in the 240B and exceeding 55W seems easy to do. I think I'll pass on the boosted amp.

The un-boosted F3 is disappointing, so I will try for a ported box with this driver and the plain 240 amp. My simple calculations indicate a 3.33 ft box with a 3" flared port 7" long. F3 of 23.

The port is too small for full power, but I'm hoping it will be ok with "normal" listening levels. Could you comment on this?
 

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A 3" flared port 7" long would tune the box to just under 25 hz, causing a hump in the response. Also with a 3 inch diameter port, air speed is exceeded with 80 watts. Lowering the tuning to 22.5 hz smoothens the response and the use of a 4 inch flared port 17 inches long allows the full 240 watts to be used and port air speed is under 26 m/s.

Here is the SPL graph comparing the sealed to the ported. The ported model is with a 4 inch port and both models have 240 watts input power.

dayton.JPG
 

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Discussion Starter #8
Wow!. So far, you have saved me 2 major errors. I need to put the port and driver on the front face cuz it is going to be a tight fit in a built in book case.

I'm not sure I can fit the larger port without increasing height beyond the WAF. I fear months of KP duty should I make the box any taller.

I got a much smaller box recommendation using a Dayton Titanic TIT320C-4. It was 2.1 ft. tuned to 25 with F3 of 25. The 3" port was 12.3" long.

Could I impose further on you to evaluate this with a 4" port? Thank you.
 

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Discussion Starter #10
Great. Can you tell me the displacement in the box for the titanic? I've looked all over for it, but can't find it.

I am also thinking a 2.0 foot box would be a perfect fit if it will work ok. I am hoping for something around 25Hz.
 

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Discussion Starter #12
Yes, primarily for home theater. Main amp is Pioneer 1015 THX - 120W per channel. Mains & surrounds are Polk Monitor 40, center is Polk CS2.

Yes, size matters. The room is central and has a stairway, hall, large opening to the living room, opening to the kitchen and door to the patio. Lots of walkways and no space (or WAF) to put a woofer. on the floor.

That leaves the built-in cabinet/bookcase. It's 10' wide. The TV sits on the counter top (above the cabinets). Speakers are in the book shelf on either side and above the TV.

The current woofer, a Polk PWS10. is in the bookcase in the lower left position and is sitting on the top pf the cabinet. The new woofer is going in the same place. May not be perfect, but it will be a real upgrade from the current one.

The slot it will occupy is 18"W 18.5"H and 20" deep. The depth figure allows room for the amp & wires and maximum extension onto the counter top. Using 3/4 MDF and allowing some clearance will work out to internal dimensions pf 15"x16"x17.5", or, 4,200 inches and a Vb of 3,500.

Just guessing at Vb as I am still uncertain of the speaker volume or the length of ports required. I'm currently looking at two 3" ports about 12" long. A single 4" port won't fit on the front and I don't know if it would be a good idea to mount it very close to one of the walls of the bookcase.
 

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15"x16"x17.5" is 4200 cubic inches or 2.4 cu.ft. Two 3" ports about 12" long will tune the box to 34 hz which won't work for a HT application. Small box, low tune, means a long port. The net volume of the box would be about 2 cu.ft. Here is the SPL graph of the 12" Titanic. 240 watts input power, tuning is 23 hz with a 4 inch port 29 inches long.

Titanic.JPG
 

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Discussion Starter #14
Chalk up another save. I started using UniBox this weekend. I made some mistakes with the ports that I was able to understand based on the info you provided. I can now check port velocity and other stuff I don't understand, yet. I think my results are close to yours, now.

The bookshelf has adjustable shelving. Length and depth are fixed, but height may be negotiable with the marital unit. Could you recommend a Vb that I should be looking at if I could increase from 2.0 to 2.7? I wouldn't want to make large size increases for marginal sound improvement.
 

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Increasing the box size to 2.7 cu.ft and lowering the tuning to 21 hz would give you a 2 db increase in output from 18 to 25 hz. Remember that you'll get more output in room when the effects of room gain are added. All modeling above is with a high pass filter at 18 hz which I'm sure the Dayton amp has. You should contact PE support and verify that fact.
 

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Discussion Starter #16
I am unable to determine if that is worth doing. It's because I have no experience listening to various speakers of known specifications.

You obviously have a lot of experience relating specifications to listener satisfaction. Would you give me your personal opinion concerning the increase in listener satisfaction from 2.0 to 2.7?

I'll call and check on that high-pass filter. Thanks for reminding me.
 

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Discussion Starter #18
Ok, I called PA and the nice tech told me that the SA240 did not have a "real" crossover to cut-off low frequency signals. It does have what he calls a rumble filter set at 18Kz. He said this would prevent the driver from bottoming. I guess we are all set.

I have been studying the difference between a 2,0 and a 2.7 box. Assuming that port speed and length are acceptable, seems like the main advantage of the bigger box is that it will be louder. What am I missing?
 

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Discussion Starter #20
Thanks to both Josh & Mike. I can see where this is headed. I will wind up with something the size of a washing machine and be sent to live with the dog.

Just kidding. I'll do some figuring and see how big I can make it while still retaining house privileges. My expectations for sound level are modest compared to some of the folks around here.

I'm not looking to move picture frames around when a cannon is fired. Just short of that will be fine. After all, this woofer only needs to blend with some Monitor 40s. I am hoping the 2.0 box will, at least, be adequate if I have to stick with that size.
 
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