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Old 9th January 2012, 01:22 AM   #1
TheGimp is offline TheGimp  United States
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Default Building a sub in a stereo cabinet

I have a Philco cabinet that had a blown amp (disconnected speaker with tube amp) that I’ve been re-purposing as a cabinet for my tube amps, turntable, preamp, etc. Ultimately I am working towards a surround system using a 25W/channel tube amp (PP 6L6s) driving a pair of Klipsch Heresy (H-700) speakers in front, and an 8W/channel SE amp driving a pair of FE103En speakers in the rear.

This leaves me with the subwoofer as a project. I have a Hafler DH-200 that I am considering for the sub amp. It is rated at 100W/Channel into 8 ohms. And it should be possible to bridge to channels to get 200W if necessary.

I got thinking today that it might be possible to seal off the bottom of the cabinet and convert it into a sub. The dimensions of the bottom section are 13” X 30” X 10” which yields a 2.67cu-ft volume.

In this configuration, the Sub could not be used when playing records, or feedback could be an issue.

The entertainment area is 12’ wide 8’ high and 14’ deep. One side is brick with a fireplace. One side is covered with drapes, the floor is wall-to-wall carpet the rear wall is paneling as is the front wall, except it has a large window as well. The stereo and TV currently are under the window. One couch and one recliner are all else in the room.

This is a moderately small room and should not require a lot of power as listening is normally at low to moderate levels (Measured level while watching “Jeremiah Johnson” is 62dB, fast response, C weighted). Musical taste varies from Jazz, rock, country, Hip-Hop, Blues, etc.

I don’t listen at concert levels, but do watch Action, Military, Sci-Fi, Western, movies etc.

Does this sound feasible to use the bottom to build a sub enclosure? I’ve not seen many 9” subwoofer drivers, other than ebay and 10” drivers won’t fit. I was thinking about possibly using a Super 8 from Apex Jr. but am concerned that the Re=2.65 ohms might be an issue.
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Old 9th January 2012, 02:52 AM   #2
NEO Dan is offline NEO Dan  United States
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I'd consider going with a 12" on the bottom, however I think that putting your sub in the same structure as your turntable is just silly.
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Old 9th January 2012, 04:07 PM   #3
tb46 is offline tb46  United States
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Hi TheGimp,

How about two of the ApexJr Super 8s in a djk PPSL arrangement? You might just have enough volume, and the PPSL is inherently vibration and distortion cancelling.

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Last edited by tb46; 9th January 2012 at 04:09 PM.
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Old 9th January 2012, 06:51 PM   #4
TheGimp is offline TheGimp  United States
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That, or a pair of W8Q-1071F in a PPSL as they have a Re of 3.2 which would be more friendly to the amp I have. Fs of 27, and Xmax of 12mm look good as well.

I'm reading the thread on the PPSL as this sounds promising.

Otherwise I guess I'll give up on putting the sub in the bottom of the cabinet and look at making the sub to fit under the left speaker, which would have the added advantage of raising it to the same level as the right speaker.
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Old 9th January 2012, 07:08 PM   #5
tb46 is offline tb46  United States
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Hi,

You can always connect the drivers in series to raise the impedance. The W8Q-1071 may need more net volume. There are also a lot of drivers on sale at PE.

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Last edited by tb46; 9th January 2012 at 07:17 PM.
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Old 9th January 2012, 07:53 PM   #6
TheGimp is offline TheGimp  United States
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Wiring the drivers in series is what I had in mind. However the TB won't fit if I'm limited to 13" depth and still have a reasonable plenum.

Dayton Audio DCS205-4 would fit, and might allow a 4" plenum depending on wood thickness, etc. With a depth of 4.25" it allows the speakers to be located closer together than the TB, thereby increasing available internal volume.

Am I correct that the lower Vas of the DCS205-4 (1.35cu-ft) compared to the W8Q-1071F (70.2L~=2.98cu-ft) would allow for a smaller enclosure for the same lower frequency cutoff?

Last edited by TheGimp; 9th January 2012 at 08:04 PM.
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Old 9th January 2012, 08:25 PM   #7
tb46 is offline tb46  United States
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Hi,

The DCS205-5 would have a similar response to the ApexJr Super 8, and twice the Xmax. App. same enclosure size. Nice find.

As to the construction, one way would be to integrate the front baffle and the plenum, and make both removable from the front. That might make mounting the drivers easier. You could also attach the ducts to the front baffle, that may make it easier to get to them for length tuning.

Just thoughts,

Regards,
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File Type: jpg PPSL_Super8_v_DCS205_SPL.jpg (36.7 KB, 205 views)
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Last edited by tb46; 9th January 2012 at 08:37 PM.
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Old 10th January 2012, 12:31 AM   #8
TheGimp is offline TheGimp  United States
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One thought I had was to mount the grill cover on a new front-board mounted from the rear as it originally was, and insert the speaker assembly from the rear independent of the cabinet so it would be removable for tuning. (no fancy finish required.)

I had planned on one shelf inside for the amps, and intended to place the turntable (SL-1200 MKII) on top to keep it as far from the sub as possible.

Actually, it would be possible to raise the shelf to leave more room for the sub, but I'd have to do a bit more work on a false front below the shelf.
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File Type: jpg Back_wo_Shelf.JPG (190.0 KB, 183 views)
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Old 13th January 2012, 07:44 PM   #9
TheGimp is offline TheGimp  United States
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For the last couple of days I've been playing with Hornresponse, but I'm missing something.

Specifications for DCS205-4 8: • Power handling: 150 watts RMS/300 watts max • VCdia: 1.5" • Le: 1.76 mH • Impedance: 4 ohms • Re: 3.53 ohms • Frequency range: 30-200 Hz • Fs: 30 Hz • SPL: 87 dB 2.83V/1m • Vas: 1.19 cu. ft. • Qms: 5.86 • Qes: 0.35 • Qts: 0.33 • Xmax: 8.8 mm • Dimensions: Overall diameter 8-1/4", Cutout diameter 7-1/4", Depth 4-1/4".
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File Type: jpg HornResp_PPSL.JPG (58.2 KB, 44 views)
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Old 13th January 2012, 08:01 PM   #10
tb46 is offline tb46  United States
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Hi,

When in the SPL window hit Tools>Combined Response.

Also L12 and L23 should be kept about as short as possible, S1 can be reduced (use fill in the back corners). djk says that the big peak past the passband does not happen; Hornresp cannot easily take the reduction in the plenum @ S2 because of the reversed driver into account.

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Last edited by tb46; 13th January 2012 at 08:19 PM.
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