TL for silver flute 6.5"?

[Dave R]

I built a compact 3-way in a ported box a couple of years ago, using the Silver Flute 6.5" W17RC38-08 woofer. (Vb = 17.5 liters, fb = 38 Hz)
The Madisound Speaker Store

Thought it might be interesting to try it in a TL instead of a ported box. A few threads that I found here have suggested it, but nothing seems to have materialized with the idea.

Are there any designs out there? Particulars?

 

[Inductor]

Hi Dave,
This driver SILVER FLUTE W17RC38-08 is not suggested for a TL in my simulator. Maybe someone can explain you why...

 

[GM]

Nice little BLH horn driver if the specs are reasonably accurate, so a simple BIB pipe horn might be worth the effort.

With a Fs/Qts = ~140 Hz, best limited to the lower mids in a TL.

A MLTL though will theoretically be even better damped than the recommended reflex.

GM

 

[Dave R]

Nice little BLH horn driver if the specs are reasonably accurate, so a simple BIB pipe horn might be worth the effort.

With a Fs/Qts = ~140 Hz, best limited to the lower mids in a TL.

A MLTL though will theoretically be even better damped than the recommended reflex.

GM

Thanks GM,

The mass-loaded TL sounds good. The bass reflex box was originally chosen because of its compact size (17.5 liters). Small footprint would be the primary objective.

The parameters that I measured on my pair of W17RC38-08 SF's were a little different than those published (see prior link). Some of the measurments may have been affected by my choice of piston diameter (ref SD) Also, the suspension seemed to take a bit more time to loosen up (probably 20+ hours) after these initial "break-in" measurements.

Fs = 46.6 Hz
Qes = 0.46
Qms = 3.1
Qts = 0.40
Vas = 18.8 liters
Le = 0.94 mH @ 1 kHz
DCR = 7.3 ohms
Xmax = 5 mm (manufacturer)
SD = .0132 m^2
Mms = 13.57 g
BL = 8.26

Again, I used vented box with Vb = 17.5 liters, fb = 38 Hz

Would you have an estimate of MLTL particulars?

I have downloaded the worksheets from MJK, but there are conflicts between Mathcad 8 and 7 (I have 7 on my working computer). The worksheets will go on my other PC -- when it can be retrieved from storage. Lots of chaos in my life this past year -- married, moved, fun stuff in storage, re-modeling garage. When the re-model is done, I'll have dedicated workshop space - AND - audio Lair. Right now, I'm a short putt away from being driven nuts by the anticipation.

 

[GM]

You're welcome!

Congrats!

I resemble that remark! Chaos is my name……….

You can make this out of [2] 1x8 and [2] 1x10 boards if desired [~1.95 ft^3 net]:

L = 60”
CSA = 56.1875”^2
Zdriver = 20.1875”
Zport = 48”
Dport = 2”
Lport = 0.75”

All dims i.d. and approximate. Sim is minimally damped, so plenty of tuning flexibility and depending on location in room, you may want to try up to a 2” long vent to get it down to ~32 Hz.

GM

 

[planet10]

Drawing, as per GM's description.

dave

 

[Dave R]

You're welcome!

Congrats!

I resemble that remark! Chaos is my name……….

You can make this out of [2] 1x8 and [2] 1x10 boards if desired [~1.95 ft^3 net]:

L = 60”
CSA = 56.1875”^2
Zdriver = 20.1875”
Zport = 48”
Dport = 2”
Lport = 0.75”

All dims i.d. and approximate. Sim is minimally damped, so plenty of tuning flexibility and depending on location in room, you may want to try up to a 2” long vent to get it down to ~32 Hz.

GM

Wow! Thanks for the quick reply.
I'm hoping for the shop to be saw-dust ready in March. As soon as I assemble my Anarchy TH's, this will be next on the list. Can't wait to check it out.

 

[Dave R]

Drawing, as per GM's description.

dave

Thanks to you too, Dave!

btw, this is for the series 3-way that I had to VI diyfest 2011. I'll toy around with folding it to put the tweeter closer to ear height.

It will be interesting to see what kind of bass extension can be obtained by varying the stuffing.

 

[Dave R]

You're welcome!

Congrats!

I resemble that remark! Chaos is my name……….

You can make this out of [2] 1x8 and [2] 1x10 boards if desired [~1.95 ft^3 net]:

L = 60”
CSA = 56.1875”^2
Zdriver = 20.1875”
Zport = 48”
Dport = 2”
Lport = 0.75”

All dims i.d. and approximate. Sim is minimally damped, so plenty of tuning flexibility and depending on location in room, you may want to try up to a 2” long vent to get it down to ~32 Hz.

GM

What would the impedance look like? If it's not too unruly, I'd like to present it to my tube amp.

btw, the sensitivity of the drivers that I measured was close to 88 dB (compared to 89 dB published by manufacturer).

 

[Dave R]

The impedance (and electrical phase) of the 3-way in the vented box looked like this. My tube amp struggled with the low end a bit. The region above was very nice, however.

Hoping a different enclosure/mounting might alleviate the impedance swings of the vented configuration.

 

[Inductor]

the sensitivity of the drivers that I measured was close to 88 dB (compared to 89 dB published by manufacturer).

Probably close to 85 dB/2.83V/m after mounted in the speaker.
Pay close attention to BS also. SPL in OB
2 pi hemispherical = 89.5 dB/2.83V/m
4 pi steradians (spherical) = 85.5 dB/2.83V/m
Baffle Diffraction Step

 

[GM]

I'll toy around with folding it to put the tweeter closer to ear height.

It will be interesting to see what kind of bass extension can be obtained by varying the stuffing.

Hmm, the plan was to put the tweeter below the woofer, so still too high?

If you want to trade flatness for extension, use a 2" long vent. The stuffing would be to 'soften' any sharpness due to group delay.

GM

 

[GM]

Probably close to 85 dB/2.83V/m after mounted in the speaker.

The sim is 2pi, so around 88 dB before any BSC [if required].

GM

 

[GM]

The impedance (and electrical phase) of the 3-way in the vented box looked like this. My tube amp struggled with the low end a bit. The region above was very nice, however.

Hoping a different enclosure/mounting might alleviate the impedance swings of the vented configuration.

Then the speaker either needs to be tuned to Fs for best power transfer or a ~max flat impedance TL is required to minimize 'swings' if the amp has too little power handling.

The MLTL will only damp down the lower peak to a greater or lesser extent depending on how low it's tuned unless it's stuffed to a fare-thee-well with a low Q sealed alignment's bass output as the trade-off.

Your plot shows equal amplitude impedance peaks, so the existing cabs appear to be tuned to Fs, so what's up with the 46.6 Hz Fs measurement?

GM

 

[Dave R]

Your plot shows equal amplitude impedance peaks, so the existing cabs appear to be tuned to Fs, so what's up with the 46.6 Hz Fs measurement?
GM

The crossover has a good sized cap on the woofer branch, which tends to shift the woofer peak down somewhat. I've seen that on the sims, and measured it also.

 

[Dave R]

Hmm, the plan was to put the tweeter below the woofer, so still too high?

GM

That could be experimented with. Just had it in my mind to put tweeter at top, mid in middle, then woof at bottom, as in previous vented box. Hmm.....

 

[GM]

The crossover has a good sized cap on the woofer branch.

OK, a 'ringing' 6th order alignment in effect, so the lower inherent tuning of the MLTL plays to this, though apparently your amp doesn't like the 'feel' of it.

GM

 

[GM]

That could be experimented with. Just had it in my mind to put tweeter at top, mid in middle, then woof at bottom, as in previous vented box. Hmm.....

FWIW, my layout factors in the vertical room modes of a ~ 8ft ceiling whereas virtually all speaker designs ignore them, so if you have a high ceiling, it may be best overall to change the line length/driver location.

GM

 

[Dave R]

Lots of work to do. The tweaking never ends. Thanks for all of the comments -- things to consider -- very educational.

 

[mem]

I think you'll like the results - I had the shielded version of the Silver Flute 6.5" and after seeing an article on some Gemme Tanto speakers I decided to through it into a cobbled-together rear-loaded horn. While it's nowhere near complete, it sounds better than anything else I've owned - bass is plentiful and breathy. Right now it's paired with a HiVi TN25... could use a bit more top end but they sound good together, especially for strings/acoustic instruments and voices.