Lab 12 Based Offset Driver - Mass Loaded - Transmission Line (OD-ML-TL) Design by Bj - Page 12 - diyAudio
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Old 2nd May 2013, 03:43 PM   #111
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Would be interesting the compare a traditional ported design tuned to the same value. Is there a measurable or audible difference? Traditional ported would be a much simpler build.
I think the long box will sound different. It reminds me of a truck box verses a trunk box. Truck boxes don't sound deep to me due to the lack of depth behind the speaker. HR shows depth affects group delay, phase response, and diaphragm displacement regarding a Kicker 08S15L74 in 2.5ft3 sealed enclosures with 8" (truck box) and 16" (trunk box) depths.
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Old 2nd May 2013, 03:53 PM   #112
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Did the same for a 2.5ft3 BR enclosure. It also affected the frequency response above 100hz.
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Old 2nd May 2013, 05:52 PM   #113
DrDyna is offline DrDyna  United States
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Did the same for a 2.5ft3 BR enclosure. It also affected the frequency response above 100hz.
Well, I can tell you, even with one of these playing, wired 4 ohms on one channel of an ep2000, its anything but shallow, its got a pretty nice thunderous growl to it.

I need to work up the ambition to go out in the garage and get my stupid measurement mic.
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Old 2nd May 2013, 09:30 PM   #114
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Drill drill the 4" holes and see how it measure and sound.
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Old 2nd May 2013, 09:41 PM   #115
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Drill drill the 4" holes and see how it measure and sound.
I'll probably do it tomorrow, I need to measure it like it is first and MiniDSP any issues out of it first before I change it.

I'm still pretty convinced that I'm going to build a proper pair of these though.
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Old 5th May 2013, 02:00 AM   #116
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Have you drilled the holes? How many of the inner partions can you reach from the driver mounting hole?

I hope we see a measurable difference, would emprically show mass loading is a real phenomenon and not just theoretical mamby pamby (precise engineering language could be substituted here).

I think two of these wil be great for the two channel rig, not sure how well they will work for HT as the don't dig below 20 Hz. The Labs 12s sound great in the temp sealed boxes I am using now, but they start rolling off to early (around 40 Hz). To counter, I have bumped up a bit with an LT via the miniDSP - but have to be careful with low end boost and cone excursion.

I don't get LT in practice. When modeling LT in winISP you have to reduce power significantly due to cone extension at the boosted frequencies, looking at before and after plots it seems it would be easier to use a shelf filter to bring down the higher frequencies instead of boosting lower. Overall the effect is almost identical if looking at max SPL at a given frequency below the LT boost due to reduced power handeling. Perhaps I am using the modeling incorrectly.

Last edited by NWCgrad; 5th May 2013 at 02:04 AM.
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Old 5th May 2013, 02:14 AM   #117
NWCgrad is offline NWCgrad  United States
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Default Report to Moderator - Thread Name Change Request

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You should be able to get a moderator to change the topic, I remember reading that the design was really an OD ML TL, but if a few days goes by before I see the thread again, the topic always puts QWP back in my head when I'm discussing it.
Suggested new thread title: Lab 12 Based Offset Driver - Mass Loaded - Transmission Line (OD-ML-TL) Design by Bjorno and tb46.

Last edited by NWCgrad; 5th May 2013 at 02:16 AM. Reason: spelling
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Old 5th May 2013, 04:00 AM   #118
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thread tittle changed per request...
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Old 5th May 2013, 04:03 AM   #119
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Thanks Tony, should help with confusion.
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Old 5th May 2013, 04:06 AM   #120
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Sorry Bjorno and tb46; title was too long and you were cut off! Thanks again for the assistance, I am getting ever closer to moving back to the US and my tools.
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