Willing to do some modeling for the Tang Band W6-789E 6.5" midbass (BF Specials)

[dcsoundz]

I have some of these: http://www.parts-express.com/pe/show...umber=264-1028

They're no longer a "buyout" item and the price is pretty good.

I should finish some speakers with them so I can listen to them and see how they sound. There isn't much competition (at any price) for a decent tweeter with a waveguide already built in (to get at least close to time alignment, which is a factor I see typically compromised in DIY AND commercial designs).

EVERY loudspeaker design, no matter what the price, is a set of compromises. Lack of time alignment seems to be one of the most universal ones chosen, to some people I've talked to though, they would not even want to bother to listen to a system that was not properly time aligned...

I'm also curious about this high-value tweeter, which seems to be endorsed by Zaph's measurements, yet hasn't really been adopted into designs that have been built and received feedback (that I'm aware of. I know Jay designed a speaker with this tweet, but I haven't seen any feedback on it).
Since it's Jay's design however, I'll ride with his ultimate choice. Here's hoping it's decided soon, especially if it's a tweeter that could be added to the TB order prior to midnight.

[tom_s]

I have a version of Jay's HDS 832873/BC25SC06-04 that I use in my video editing suite at work. Old, ugly boxes, but I needed monitors for the new edit system that just came online and we had nothing left in the budget. Jay's timing with crossover was perfect, so I threw them together. I didn't even have time to round over the baffle edges or paint them. They went from shop to daily duty. Voice-overs are very clear and I can easily judge when I need to clean up breath sounds between phrases. They also let you know when the music is encroaching on the voice track. I also like to listen to music when doing graphics. They are quite smooth, even when the source is an ipod.

With that in mind, I would not have any reservations using the BC25SC06-04 and the sensitivity requirement for an MTM really narrows the field.

[jkim]

Tweeter decided. I will create two versions of crossovers: one with the SB Acoustics SB29RDCN-C000-4 and the other with the Vifa DQ25SC16-04 (available only at Madisound or Meniscus).

If you want something available at PE, the soft dome version of the Vifa (with a truncated frame), BC25SC55-04:

http://www.parts-express.com/pe/show...umber=264-1024

can be substibuted. But the hornloaded version, BC25SC06-04, cannot be used. The ferrite, larger faceplate versions, BC25SG15-04 and BC25TG15-04:

http://www.parts-express.com/pe/show...umber=264-1026
http://www.parts-express.com/pe/show...umber=264-1040

can also be substitued for the DQ25SC16-04 with suggested crossover fine-tuning options.

jAy

[jkim]

I have a version of Jay's HDS 832873/BC25SC06-04 that I use in my video editing suite at work.

Tom, yours must be the truncated frame version, BC25SC55-04, not the hornloaded version, BC25SC06-04. Am I wrong?

[tom_s]

I have the horn loaded versions at work. You had helped out Caleb with his crossover. I had a few of these in the parts bin and needed monitors in just 2 days. I figured they would likely be as good (or in this case better) than my old Dynaco A25s for near-field use.

http://techtalk.parts-express.com/sh...fa+BC25SC06-04

My brother was the recipient of the truncated versions. Those still may be my favorites...

[jkim]

I have the horn loaded versions at work. You had helped out Caleb with his crossover. I had a few of these in the parts bin and needed monitors in just 2 days. I figured they would likely be as good (or in this case better) than my old Dynaco A25s for near-field use.

http://techtalk.parts-express.com/sh...fa+BC25SC06-04

My brother was the recipient of the truncated versions. Those still may be my favorites...

Oh, that one. I thought you were talking about the speakers you built for your brother. As you can see, shooting for LR4 with the horn-loaded Vifa takes more parts. That's one of the reasons why I did not choose it for a design in this thread.

[Erich H]

I ordered 6 of them but I'm going to wait to see which tweeter makes the most sense.

[ckmoore]

I ordered 6 of them but I'm going to wait to see which tweeter makes the most sense.

Same here, but I only got 2

[jkim]

MTM with SB29RDCN-C000-04

(EDIT: Vented cabinet port sizes given initially were incorrect. Corrected now)

Cabinet

It turns out that this midbass driver does not like anything smaller than 0.8 cu ft per driver for a vented alignment. For this MTM modeling, I used 1.6 cu ft net volume with 46 Hz tuning, but 2.0 cu ft with 44 Hz tuning is even better. This means that the cabinets have to be floorstanding unless you like to have really big standmounters.

With 1.6 cu ft volume, two 2.5" ID tubes cut to 5.75" length (including the flare), or a single 3.75" ID tube cut to 5.75" length (including the flare) will give 46 Hz tuning. With 2.0 cu ft volume, two 2.5" ID, 5" long tubes, or a single 3.75" ID, 5" long tube will give 44 Hz tuning. It can be front- or rear-ported. The cabinet's inner walls should be lined with acoustic foam, and the bottom 8" to 10" be filled with dense polyfill.

A sealed cabinet requires 0.5 to 0.6 cu ft per driver, which means 1.0 to 1.2 cu ft for MTM, and will provide a system -3 dB point at 80 Hz. This is perfect for the speakers to be used with a subwoofer or two, integrated by an AV receiver's active low and high pass filters. Standmounters should be possible. A sealed cabinet should be filled 80% with polyfill.

Baffle width should 8.5" to 9". Two midbass drivers' center-to-center distance is 9.75" (frames are 2.75" apart). The tweeter is in the middle of two midwoofers with a 1.375" (1-3/8") horizontal offset (L/R mirror image). Baffle height and distance from baffle top to the top midbass do not matter. Your ear should be level with the tweeter. All drivers should be flush mounted in properly recessed cutouts.

I do not provide cabinets' external dimensions. You should be able to come up with your own based on the requirements given above.

I recommend rounding over baffle sides using at least 1/2" round over bit (rounding over top and bottom is not required). In case the baffle is 1" thick or thicker, you should chamfer the midwoofer holes from inside to ensure good airflow behind the drivers.

Crossover

Below are the schematic---all component specs are included---, and its predicted responses:






Don't use expensive caps or foil inductors. Parts Express Dayton standard poly caps are perfect, and Jantzen or Erse coils will work great. On the crossover board, inductors need to be placed carefully to avoid their interference. If you post a picture of your initial layout in this thread, people will give you good feedback.

When soldering components, if you don't have much experience, it's always a good idea to use heat sinks like alligator clips between joints being soldered and component bodies not to damage them by overheating. 14 gauge (even 16 gauge) cable is thick enough for internal wiring.

Options

Tweeter fine-tuning: I strongly recommend fine-tuning the tweeter response by adjusting R9 and C9 values. Default values are 1.2 ohm and 11.5 uF. To tweak C9, buy 10 uF and two 1.5 uF caps per speaker. Then you'll be able to try 10, 11.5, and 13 uF by wiring them in parallel.

Primary inductor DCR: You can choose either Jantzen P-core (or steel laminate core) or air core 15 to 18 gauge, but you should be aware of the consequence of the choice. I assumed 0.33 ohm DCR in my modeling. Using a higher DCR inductor (for example, 18 gauge air core with 0.6 ohm DCR) versus a lower DCR one (e.g., Jantzen P-core with 0.14 ohm DCR) will cause up to a 1 dB difference in lower midrange and bass.

-jAy

[rogoll]

Tweeter decided. I will create two versions of crossovers: one with the SB Acoustics SB29RDCN-C000-4 and the other with the Vifa DQ25SC16-04 (available only at Madisound or Meniscus).

If you want something available at PE, the soft dome version of the Vifa (with a truncated frame), BC25SC55-04:

http://www.parts-express.com/pe/show...umber=264-1024

can be substibuted. But the hornloaded version, BC25SC06-04, cannot be used. The ferrite, larger faceplate versions, BC25SG15-04 and BC25TG15-04:

http://www.parts-express.com/pe/show...umber=264-1026
http://www.parts-express.com/pe/show...umber=264-1040

can also be substitued for the DQ25SC16-04 with suggested crossover fine-tuning options.

jAy

Sorry if this has already been discussed an I just missed it, but something that concerns me about the specs listed for the Vifa (and several other, including Jamo) tweeters is that they are giving the frequency range all the way down to the driver's resonant frequency. My understanding was that you needed to stay above double that frequency. Has this changed due to Neo magnets or some other technology advance?

Also, the spec sheet for the Vifa BC25SC55-04 says it has a "cooling fan"???? Are they referring to the heat sink (just mistranslated)?

[critofur]

Sorry if this has already been discussed an I just missed it, but something that concerns me about the specs listed for the Vifa (and several other, including Jamo) tweeters is that they are giving the frequency range all the way down to the driver's resonant frequency.

Marketing specifications can be, shall we say, a bit optimistic The "usable frequency range" is subjective, more so than some of the other specs like Re, Le, x-max, etc... I wouldn't blindly trust PE's stated usable frequency range (I tend to disagree with some of them), go with third party testing such as Zaph, etc, or, your own educated guess. Or, better yet, ask folks on the forum here

My understanding was that you needed to stay above double that frequency. Has this changed due to Neo magnets or some other technology advance?

That's a "rule of thumb" not a rule... The "some other technology advance" would be crossover simulation (speaker CAD) software being used more widely by DIY speaker folks...

The impedance spike at a tweeter's FS, depending on how severe it is could cause a "textbook" crossover to fail badly. So long as you use the tweeter within its physical limits, and, in order to sound very good, within limits dictated by its distortion performance, one need not follow any hard-and-fast rule regarding FS.

For anyone who doesn't know yet, the higher the impedance is, the less "effective" a given crossover component is. So, the spike in impedance would cause the tweeter's output around FS to be higher than intended, if not addressed in the crossover...

Also, the spec sheet for the Vifa BC25SC55-04 says it has a "cooling fan"???? Are they referring to the heat sink (just mistranslated)?

Obviously, it should have said FIN not FAN

[jkim]

MTM with Vifa DQ25SC16-04 (or other Vifa tweeters; see Options below)

Cabinet

See above (post #49).

Crossover

Below are the schematic---all component specs are included---, and its predicted responses:






Don't use expensive caps or foil inductors. Parts Express Dayton standard poly caps are perfect, and Jantzen or Erse coils will work great. On the crossover board, inductors need to be placed carefully to avoid their interference. If you post a picture of your initial layout in this thread, people will give you good feedback.

When soldering components, if you don't have much experience, it's always a good idea to use heat sinks like alligator clips between joints being soldered and component bodies not to damage them by overheating. 14 gauge (even 16 gauge) cable is thick enough for internal wiring.

Options

Using other Vifa tweeters: A soft dome version, (with a truncated frame), BC25SC55-04, can be substituted for the DQ25SC16-04. But the hornloaded version, BC25SC06-04, cannot be used. The ferrite, larger faceplate versions, BC25SG15-04 or BC25TG15-04, can also be substituted with suggested crossover fine-tuning options below. The midbass drivers' center-to-center spacing should be adjusted in this case.

Tweeter fine-tuning: I strongly recommend fine-tuning the tweeter response by adjusting R9 and C9 values. Default values are 1.35 ohm (two 2.7 ohm resistors wired in parallel) and 12 uF. To tweak C9, buy 10 uF and three 1.0 uF caps per speaker. Then you'll be able to try 11, 12, and 13 uF by wiring them in parallel.

Primary inductor DCR: You can choose either Jantzen P-core (or steel laminate core) or air core 15 to 18 gauge, but you should be aware of the consequence of the choice. I assumed 0.33 ohm DCR in my modeling. Using a higher DCR inductor (for example, 18 gauge air core with 0.6 ohm DCR) versus a lower DCR one (e.g., Jantzen P-core with 0.14 ohm DCR) will cause up to a 1 dB difference in lower midrange and bass.

-jAy

[Erich H]

I can't wait to get these started. Believe it or not, my 6.5" drivers were delivered this morning. Nice packaging.

I've never built a crossover before, so I've got some learning to do.

[jkim]

Horizontal MTM for Center Channel with SB29RDCN-C000-04

*There will be no center channel design with the Vifa tweeter due to the demand of a low crossover frequency for horizontal MTM.

Cabinet

Using a center channel speaker usually implies that it is included in a full home theater speaker system loaded with a subwoofer or two. So, a sealed cabinet is suitable. A vented MTM will be too large for a center channel speaker, anyway. A sealed box for MTM requires 1.0 to 1.2 cu ft net internal volume, which will give the system a -3 dB point of 80 Hz. The cabinet should be filled 80% with polyfill.

To minimize horizontal MTM's lobing errors, I suggest the following baffle size and driver layout. The baffle is 10.5" high and 18" wide---width can be adjusted (e.g., 16" to 22"). Depth is determined so that the net internal volume is 1.0 to 1.2 cu ft. The tweeter is right in the middle of the baffle horizontally, and its center is 2.5" away from the top edge. The two midwoofers's centers are located 6.125" (6-1/8") away from the baffle's top edge (4.375" away from the bottom edge), nearly touching each other's flange horizontally, which means their center-to-center distance should be 7" to 7.125".

This driver layout will make the speaker's horizontal listening angle as wide as +/-20 degrees, which should be sufficient for most HT setups.

Crossover

Below are the schematic---all component specs are included---, and its predicted responses:






Don't use expensive caps or foil inductors. Parts Express Dayton standard poly caps are perfect, and Jantzen or Erse coils will work great. On the crossover board, inductors need to be placed carefully to avoid their interference. If you post a picture of your initial layout in this thread, people will give you good feedback.

When soldering components, if you don't have much experience, it's always a good idea to use heat sinks like alligator clips between joints being soldered and component bodies not to damage them by overheating. 14 gauge (even 16 gauge) cable is thick enough for internal wiring.

Options

Tweeter fine-tuning: I strongly recommend fine-tuning the tweeter response by adjusting R9 and C9 values. Default values are 0.6 ohm (two 1.2 ohm resistors wired in parallel) and 12.5 uF. To tweak C9, buy 10 uF, 1.0 uF, and two 1.5 uF caps per speaker. Then you'll be able to try 11, 12.5, and 14 uF by wiring them in parallel.

Primary inductor DCR: You can choose either Jantzen P-core (or steel laminate core) or air core 15 to 18 gauge, but you should be aware of the consequence of your choice. I assumed 0.33 ohm DCR in my modeling. Using a higher DCR inductor (for example, 18 gauge air core with 0.5 ohm DCR) versus a lower DCR one (e.g., Jantzen P-core with 0.13 ohm DCR) will cause up to a 1 dB difference in lower midrange and bass.

-jAy

[jkim]

I can't wait to get these started. Believe it or not, my 6.5" drivers were delivered this morning. Nice packaging.

I've never built a crossover before, so I've got some learning to do.

Check out the following web articles. You will have no problem building crossovers.

http://www.parts-express.com/project...ver/xover.html
http://www.speakerbuilder.net/web_fi...xo/xoconst.htm
http://www.geocities.com/cc00541/nodal_analysis.html
http://www.troelsgravesen.dk/coils.htm

-jAy

[jkim]

TM with SB29RDCN-C000-04

Cabinet

It turns out that this midbass driver does not like anything smaller than 0.8 cu ft (22.5 liters) for a vented alignment. For this TM modeling, I used 0.8 cu ft net volume with 46 Hz tuning, but 1.0 cu ft with 44 Hz tuning looks even better. This means that the cabinets have to be either tall standmounters or floorstanders.

With 0.8 cu ft volume, a 2.5" ID tube cut to 5.75" length (including the flare) will provide 46 Hz tuning. With 1.0 cu ft volume, a 2.5" ID, 5" long tube will give 44 Hz tuning. It can be front- or rear-ported. The cabinet's inner walls should be lined with acoustic foam, and the bottom 4" to 6" be filled with dense polyfill.

A sealed cabinet requires 0.5 to 0.6 cu ft, and will provide a system -3 dB point at 80 Hz. This is perfect for the speakers to be used with a subwoofer, integrated by an AV receiver's active low and high pass filters. A sealed cabinet should be filled 80% with polyfill.

Baffle width should 8.5" to 9". The tweeter's center is placed 3" away from the baffle's top edge with no horizontal offset. The midwoofer's center is 5.125" (5-1/8") below the tweeter's center, that is, 8.125" away from the baffle's top edge. All drivers should be flush mounted in properly recessed cutouts.

I do not provide cabinets' external dimensions. You should be able to come up with your own based on the requirements given above.

I recommend rounding over the baffle's top and sides using at least 1/2" round over bit (rounding over the bottom edge is not needed). In case the baffle is 1" thick or thicker, you should chamfer the midwoofer holes from inside to ensure good airflow behind the drivers.

Crossover

Below are the schematic---all component specs are included---, and its predicted responses:






Don't use expensive caps or foil inductors. Parts Express Dayton standard poly caps are perfect, and Jantzen or Erse coils will work great. For L1 (2.5 mH), Parts Express steel laminate 18 gauge is a great choice. On the crossover board, inductors need to be placed carefully to avoid their interference. If you post a picture of your initial layout in this thread, people will give you good feedback.

When soldering components, if you don't have much experience, it's always a good idea to use heat sinks like alligator clips between joints being soldered and component bodies not to damage them by overheating. 14 gauge (even 16 gauge) cable is thick enough for internal wiring.

Options

Tweeter fine-tuning: I strongly recommend fine-tuning the tweeter response by adjusting R9 and C9 values. Default values are 4.7 ohm and 7.8 uF (6.8 uF and 1.0 uF caps wired in parallel). To tweak C9, buy 6.8 uF and two 1.0 uF caps per speaker. Then you'll be able to try 6.8, 7.8, and 8.8 uF by wiring them in parallel.

-jAy

[jkim]

TM with Vifa DQ25SC16-04 (or other Vifa tweeters; see Options below)

Cabinet

See above (post #56)

Crossover

Below are the schematic---all component specs are included---, and its predicted responses:






Don't use expensive caps or foil inductors. Parts Express Dayton standard poly caps are perfect, and Jantzen or Erse coils will work great. For L1 (2.5 mH), Parts Express steel laminate 18 gauge is a great choice. On the crossover board, inductors need to be placed carefully to avoid their interference. If you post a picture of your initial layout in this thread, people will give you good feedback.

When soldering components, if you don't have much experience, it's always a good idea to use heat sinks like alligator clips between joints being soldered and component bodies not to damage them by overheating. 14 gauge (even 16 gauge) cable is thick enough for internal wiring.

Options

Using other Vifa tweeters: A soft dome version, (with a truncated frame), BC25SC55-04, can be substituted for the DQ25SC16-04. But the hornloaded version, BC25SC06-04, cannot be used. The ferrite, larger faceplate versions, BC25SG15-04 or BC25TG15-04, can also be substituted with suggested crossover fine-tuning options below. The midbass driver's location should be adjusted in this case.

Tweeter fine-tuning: I strongly recommend fine-tuning the tweeter response by adjusting R9 and C9 values. Default values are 3.7 ohm and 10.2 uF (8.2 uF and two 1.0 uF caps wired in parallel). To tweak C9, buy 8.2 uF and three 1.0 uF caps per speaker. Then you'll be able to try 9.2, 10.2, and 11.2 uF by wiring them in parallel.

-jAy

[jkim]

Done!

[peko]

Thank you Jay,for the options and all the hard work.You've kept the driver costs down and parts count low. I would like to try the TM's with the DQ's since I have the Vifas at hand.If I can find a work shop I'll build some soon,as i took advantage of the TB sale.Once again thank you from the "great white north" i.e. Montreal.Peko.

[Mayhem13]

Phase tracking of the MT is exceptional at the crossover point......shoulbe very smooooth. Nice Job Jay.

For those tuning in, given the Facts and Jay's box modeling for tuning, i don't find the ported options to be very viable but the sealed version with it's acoustical 2nd order rolloff combined with the HP of most AVR's at 80hz should be as good as it gets for sub integration. Let the 6.5" driver play the midbass and the subs do the low stuff. These will get pretty loud with only a few watts of power......we're talkin 110db with only 50watts for the sealed MTM. Pretty not bad for those with entry level AVRs.