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Old 14th February 2018, 10:33 AM   #71
Scottmoose is offline Scottmoose  United Kingdom
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Nobody is 'unprepared' but you may wish to reflect on the fact that we do not all have unlimited time. I started typing something yesterday, but frankly, I have work to do, and after half an hour I had to give up. However, I have ten minutes spare, so I'll do my best to cover some aspects.

Firstly, here is the FE206En (factory data) in your Sony TL, with the dimensions you provided a few posts back. 1/2 space FR, impedance & RMS driver deflection; left hand column shows undamped response for clarity of line behaviour, right hand shows same with light damping equivalent to what is typically used in such boxes in the first two manifolds.

There are a lot of erroneous assumptions & pronouncements above, so here are some engineering facts.

-The FE206En (& variations of the 206) were specifically intended for use in back-horns with a high output impedance amplifier, or similar compensation applied via series R &c. They have a rising on-axis response above ~ 1KHz to enhance off-axis dispersion and are not intended to be listened to directly on-axis unless you happen to like an elevated HF.

-Much of the 'slam' or 'punch' referred to in classical & particularly rock music is found in the octave 60Hz - 120Hz.

-For a given tuning & volume, a TL has a higher, not lower, F3 than an equivalent vented box.

-A TL cannot 'correct' for driver characteristics that exist well above the enclosure's operating BW. No back load can, with certain exceptions for compression horns that significantly load & alter the resonant profile of the diphragm & suspension, and in their case it's more 'alter' than 'correct for'.

-Sd has no direct connection to line CSA in a TL / QW enclosure. Like any other kind of vented box, Qt, Fs and Vas dominate. So you should not be 'scared' of putting a totally different driver into some other random box just because of a difference in size. You should be 'scared' for other reasons, but that one comes some way down the list of problems.

-The line you have drawn is tuned to roughly the low-mid 30Hz regions, and combined with its highly damped characteristics (using the factory data) has a highly damped LF response at some -6dB. This tuning is lower than the driver is suited to, especially for the available volume, unless it is picking up significant assistance from amplifier, room modes or similar. Rooms are the greatest variable in the entire sound reproduction chain, and different enclosures interact with them in different way, so beyond a certain point, this cannot be predicted with particular accuracy.
Attached Images
File Type: png Sony QW with 206En.png (55.8 KB, 104 views)
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Last edited by Scottmoose; 14th February 2018 at 10:36 AM.
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Old 14th February 2018, 06:15 PM   #72
GM is offline GM  United States
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FWIW, up until fairly recently [and probably still the norm in most venues], prosound systems, which we know has plenty of 'slam' [true 'chest thump' is down in the ~20-35 Hz BW], were set up to be ~ -24 dB/40 Hz and ~flat from 80-300 Hz, so a ~56 Hz tuned 'scoop bin' [BLH] with a~ 300 Hz mass corner and at least a +6-10 dB gain [depending on room acoustics] seems the goal here.

The FE206en theoretically has plenty of motor, so little/no series resistance should be required and if true 'chest thump' is required, then that's what a separate sub system is for, though one's home needs to be well built to handle the extremely high SPL and sound deadening required [THX LFE reference at minimum].

GM
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Old 14th February 2018, 06:36 PM   #73
Scottmoose is offline Scottmoose  United Kingdom
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Sounds favourite to me. The existing amp is supposed to be a 6550 PP, so output impedance will probably be in the ~0.75ohm - 1.5ohm region, & with an Andy Grove designed 300b SET apparently in the offing, that's probably going to rise to somewhere around 2.5ohm - 4ohm. Some Ni80 resistance wire might be cheaper to get what little series R should be needed -doesn't look as good on the rack though.
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Last edited by Scottmoose; 14th February 2018 at 06:50 PM.
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Old 15th February 2018, 04:54 AM   #74
GM is offline GM  United States
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Missed the 300B part, but if the mid bass should become a little 'flabby' from excessive series R, then a little throat damping or even a nice, tightly stretched mouth grill cloth screen should 'snap'/'tighten' it right up.

GM
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Old 15th February 2018, 10:20 AM   #75
Scottmoose is offline Scottmoose  United Kingdom
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Last edited by Scottmoose; 15th February 2018 at 10:23 AM.
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