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Acceptable transition freq between dipole panel and boxed sub ?
Acceptable transition freq between dipole panel and boxed sub ?
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Old 19th February 2019, 11:36 AM   #21
SoundRight is offline SoundRight  United Kingdom
diyAudio Member
Join Date: Jul 2010
Just to add my input. The cone excursion required for dipole bass is substantial, even with multiple 15" drivers driven into their X limit, which is not a preferred method as they are no longer linear and distortion rises. I checked a range of different 15's in WinISD and power handling was severely compromised. For some they could only manage 20 or so watts even when used with a 40Hz HP. Running them from 80-100Hz on a 4th order, the power handling increased to well beyond their power rating, many in excess of 1000watts to meet their Xmax. For those interested, and although not perfect, you can simulate open back by assuming a very large cabinet of say, 1000 litres!! But you also need to add a shelf filter that replicates the 6dB roll off cancellation as a result of baffle dimensions.

This natural roll off is of course critical and to preserve the actual crossover point, you need to EQ the dipole with a +6dB shelf. As a rule of thumb, if the dipole is sitting on the ground, the frequency equivalent to twice the diagonal of the baffle is a rough starting point.

With a baffle holding 2 x15's (3ft x 1.5ft ish), it starts rolling between 180-225Hz and this is where you need to start your shelf EQ. Clearly then you will be around +12dB at 50Hz. No wonder you have no power handling!!

To maintain an accurate 100Hz X/over without EQ correction you are looking at 6 x 15's in a baffle around 5ft x 3ft approximately. Yes, that is 12 x 15'S in total for stereo!

Another aspect which may have some relevance, and comment welcomed, the dipole bass increases it's GD as the frequency drops. A Transform box, or small cabinet monopole, even with the required EQ can remain in very low GD figures down to the lowest required frequency.

And as for combining monopoles and dipoles, I had a classic system in the 70's, stacked Quads, 2 x 15 monopole bass bin and Kelly ribbon tweeters stuck between the Quads. A TEAC 12dB/oct active x/over divided them, a sensible room some 30ft x 14ft and the sound was just wonderful with no "join" between the Quads and the bass bins which were some 12 ft behind them against a wall....

Last edited by SoundRight; 19th February 2019 at 11:38 AM.
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Old 19th February 2019, 10:07 PM   #22
esl 63 is offline esl 63
diyAudio Member
Join Date: Aug 2010
I couldnt state it better myself: "going boxed below the lowest room node" Post nr #7

I have a big room 10meter long. 15-27Hz is handeled with 4 custom made 15" JBL elements moving air between the listening room and outside "nature". I so to say have an Infinite baffel.
27-200 (will be changed to 27-150 Hz) is managed by 4 dayton IB15" woofers in 2*15" configuration subs, that is acting as stands for QUAD Esl63 speakers and obviusly they go from 200Hz to infinity... :-) well not really, but without metal grille and no dustcovers, bypassed electrolytic cap, + some other mods, they sound good.

Point is. Below the lowest room mode there is no point going dipole.
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