It's true that tweeters have a lower power handling and that they distort when crossed low. Another point to take in mind however is that most designers strive for (somewhat) constant directivity: equal beamwidth for all frequenties. Midranges cannot play high without narrowing that beam due to their size. Tweeters are small so they have a wide beam, except at the topmost octave. So you are left with a wide beam at low frequencies (midrange speaker is small compared to the wavelength of sound), narrowing with increasing frequency up to the crossover point (midrange becomes somewhat large compared to wavelength), then at higher frequencies the tweeter takes over and the beam becomes wide again (tweeter is small compared to wavelength) and at the top octave it gets narrow again (tweeter becomes somewhat large compared to the wavelength).
If you cross over at a low frequency, the midrange only has to deal with low frequencies and therefore long wavelengths, so its beamwidth is always wide.
It's a compromise.
If you cross over at a low frequency, the midrange only has to deal with low frequencies and therefore long wavelengths, so its beamwidth is always wide.
It's a compromise.
Last edited:
Mayuri, a 20l cabinet looks like a good choice.
The attached LR4 LR4 for the Peerless 830869 and SB26ADC-04 alu dome tweeter was simulated on a W12" x H18" baffle plus a ported cabinet. Locating the tweeter 0.8" off-center simulates best for low diffraction. For Qt=0.7, a W12" x H18" x D16" 1.2cuft-net volume ported cabinet tuned for 38Hz (3" diameter, 8.7" long) is required. Deeper bass requires a much larger cabinet(3cuft net) with a -3db bass shelf tuning(28Hz, 3"diameter, 5.6" long).
IF deep bass is not the main goal for this 8" , a single cabinet with 0.7-0.75cuft(20-21 liters) can be constructed with a port which can easily be plugged. You will have an 8" to cover the vocal range; deliver impact/slam. From the 61 vs. 73Hz data, it seems that the only reason to include the ported option is for the deeper stand-alone -F10 + room effects.
...A sealed cabinet of 0.74cuft creates Qtc=0.7 tuning with -F3=. 73Hz
...A 20liter(0.7cuft) net volume tuned to 30Hz for a flat SPL yields -F3=61Hz (2" diameter, 11.8" long)
Attachments
I looked to the drivers you mention and the woofer is 8 ohms and the tweeter 4 ohms. Is it possible to have different driver impedance ?? I guess if that is possible the crossover will play a role determining the speaker impedance.
Thanks
online free speaker enclosure calculator ??
I have used an online software to calculate a SEALED enclosure for the drivers I am thinking to buy. The mid-woofer is Scan Speak 22W/8534G.
These are the results:
Width: 11.45 inches
Height: 18.53 inches
Depth: 7.08 inches
Q-0,857
Frequency at peak db: 116.67 hz
Peak level of resonance fb: 0.467 db
F3 : 56.34 hz -3db
What do you think about the results of online softwares ??, and the most important: Can I play with the measurements if I keep the internal volume intact ??
Many thank for all the help.!
I have used an online software to calculate a SEALED enclosure for the drivers I am thinking to buy. The mid-woofer is Scan Speak 22W/8534G.
These are the results:
Width: 11.45 inches
Height: 18.53 inches
Depth: 7.08 inches
Q-0,857
Frequency at peak db: 116.67 hz
Peak level of resonance fb: 0.467 db
F3 : 56.34 hz -3db
What do you think about the results of online softwares ??, and the most important: Can I play with the measurements if I keep the internal volume intact ??
Many thank for all the help.!
Looks fine.
Yes, you can vary the dimensions. Particularly for a sealed box, you can vary the volume too. I'd go for 35-50 litres, but as small as 20 litres should be OK.
Since you like the aesthetics of the Suzie "Q", the baffle sized you already stated seems about right. I'd probably keep those dimensions, but make it a little bit deeper.
Keep in mind that you have to use internal dimensions to calculate the air volume.
Yes, you can vary the dimensions. Particularly for a sealed box, you can vary the volume too. I'd go for 35-50 litres, but as small as 20 litres should be OK.
Since you like the aesthetics of the Suzie "Q", the baffle sized you already stated seems about right. I'd probably keep those dimensions, but make it a little bit deeper.
Keep in mind that you have to use internal dimensions to calculate the air volume.
In general, and broad terms, you are right, but modern drivers come in a variety of flavors. Crossing over at 2kHz is quite reasonable for a lot of tweeters, and crossing over at 3-5kHz is quite reasonable for a lot of 5" mid-woofers.
One tweeter worth using as an example is the Peerless / Vifa XT25 series. The BG version has a larger chamber, and dual magnets, allowing a significantly lower crossover point than the XT25TG even though this difference is impossible to tell from the front of the tweeter. Everything that helps it go down further is hidden behind the face plate.
Best,
E
One tweeter worth using as an example is the Peerless / Vifa XT25 series. The BG version has a larger chamber, and dual magnets, allowing a significantly lower crossover point than the XT25TG even though this difference is impossible to tell from the front of the tweeter. Everything that helps it go down further is hidden behind the face plate.
Best,
E
Post #12 Review the crossover schematic, the impedance graph in the lower right, and the datasheet for the SB29RDC-4. This design uses the 8-ohm Peerless P830869 and 4-ohm SB29RDC(*same voice coil as the SB26ADC-04 alu dome)
The DC resistance of the 1.1" SB29RDC-4 dome tweeter is 3.7ohms with Le=0.05mH inductance at 1kHz. Since this inductive voice coil oscillates in a magnetic field, the (resistance + phase)impedance will change with frequency(4.5ohms @20kHz) as shown in the manufacturer's spec sheet.
At high frequencies capacitors have a low impedance and inductors have a high impedance. At high frequencies the tweeter crossover C-L circuit works as a low resistance feed-through(in series with the input padding resistor). The impedance graph for the tweeter frequency range of 2kHz - 20kH shows a modest change in impedance from 4.7 to 5.2 ohms, and this is the load your amplifier must drive. The 20-20kHz impedance graph shows the full range of amplifier load. Most solid state amps have an output impedance <0.3ohms and function like an ideal voltage source into a wide range of impedance.
If you have a low output tube amp, the drivers and crossover circuits can be selected for a higher(8ohm+), more even impedance.
Thanks for your help. Yes, the only measure that doesn't convince me is the depth. It is just that what I want to make it deeper.
Not that hopeless. This is 22W8534g00 (30cm baffle, test cab) with Seas NoFerro650 in Visaton waveguide. Drivers raw data actual measured.
Attachments
Given the rapidly increasing HD < 2KHz on all of the XT25s that I've encountered, I'm not sure I'd be especially inclined to take any of them low, however big the motor. All the ones I've seen have the usual HD2 rise < 2KHz that you get from most ring-radiators or large surround domes, and the modest radiating area (roughly equivalent to a 3/4in dome in practice) tends to cause rising higher harmonics < 2KHz also. Not knocking them, I like them well enough for what they are, but I wouldn't call them ideally suited for low[er] filter frequencies compared to, say, a Seas 27TDFC (H1189) or 27TBFC/G (H1212) in more or less the same price bracket.
Last edited:
A crossover doesn't cut frequencies, it blends two (or more) drivers together. It is true what TBTL said, that a somewhat constant directivity in the transition range is a goal for a good crossover. Thus the dimension of a midwoofer dictates how high it can be crossed over to a tweeter: in general 3-3.5KHz for a 5", 2-2.5KHz for a 6", and sub 2KHz for a 8". The slope also does matter.
If you want to cross at 2KHz or below, you need a robust tweeter: no less than 1" VC, decent xmax, and decent distortion profile. A waveguide can also help a lot.
Ralf
The design someone suggested you on another thread is good in this respect.
If you want to cross at 2KHz or below, you need a robust tweeter: no less than 1" VC, decent xmax, and decent distortion profile. A waveguide can also help a lot.
Ralf
The design someone suggested you on another thread is good in this respect.
Speaking from experience with the 830869, you can use a simpler filter to achieve an LR4 slope. My speaker uses a single series 2.2mh inductor along with a parallel LCR of 15uF, 0.1mh, and 1.2R to achieve an LR4 at 1.5k. As a side benefit there is much less phase wrap with this crossover which may help to match the phase response to the tweeter. Try modeling this or something close to it and see if it suits your design also (if my memory serves, just increasing the cap to 20 or 25 will bring the response to 1400 LR4 if that’s still your goal). Also, in a 21L cabinet my speakers comfortably reach 35hz in my smallish living room before dropping off; hopefully you’ll get similar results. I posted measurements of my speaker at the tech talk forum.
pics of my 8"/1"+WG 2-way plus crossover - Techtalk Speaker Building, Audio, Video Discussion Forum
I’m still using the same speakers and love the 830869 to death. It sounds really fantastic. But incidentally I always did want to try the ScanSpeak 22W/4534G00 in its place to see what difference it made. At the time, modeling in PCD7 suggested that it would work with a very similar XO as the peerless, compensating for the lower impedance of course.
Last edited by a moderator:
The sw you used don't take into account the stuffing. You definitely want a good amount of stuffing for a closed box. In this case I wouldn't go higher than 25-30L. Your chosen measure (W & H) are on the large side, so the D will be shorter than what you want. Shorten W & H or be happy with a short D. Alternatively "waste" some of the internal volume for example with a 45 degree brace. Or build a cabinet with curved panels like the Wharfedale Diamond 9 series.
Ralf
Ralf
Hi Scott,
I did not mean to bring up the XT25 debate, but just to show that you can't judge a tweeter's bottom end response from the driver size alone.
Best,
E
I did not mean to bring up the XT25 debate, but just to show that you can't judge a tweeter's bottom end response from the driver size alone.
Best,
E
Dvjorge, have you listened to a 2khz sine wave before? A lot of people haven’t. If you can download a sine wave generator it will help give you an idea of what a 2khz wave sounds like, or any wave for that matter. After hearing it you will likely not be surprised that a 1” diaphragm can comfortably produce that pitch. Download a wave generator if you can and play around with it. (Since I brought it up I downloaded a free one for the iPad, so it’s at least that easy to get.)
I think a lot of people might be under misapprehensions about the actual pitch of various frequencies. I used to wonder why the full range folks thought that crossing full range drivers around 3-400hz (the typical FAST design) would be superior to the typical 2-way XO point of ~2khz. 3-400 is smack-dab in the middle of most instrument and voice ranges, whereas 2khz is already getting into overtone territory:
I think a lot of people might be under misapprehensions about the actual pitch of various frequencies. I used to wonder why the full range folks thought that crossing full range drivers around 3-400hz (the typical FAST design) would be superior to the typical 2-way XO point of ~2khz. 3-400 is smack-dab in the middle of most instrument and voice ranges, whereas 2khz is already getting into overtone territory:
I used to wonder why the full range folks thought that crossing full range drivers around 3-400hz (the typical FAST design) would be superior to the typical 2-way XO point of ~2khz. 3-400 is smack-dab in the middle of most instrument and voice ranges, whereas 2khz is already getting into overtone territory:
True. OTOH, ~2-3kHz is pretty much smack-dab in the middle of our auditory system's highest sensitivity range, so any discontinuities between drivers and/or aberrations induced by the crossover are likely to be more audible...
An externally hosted image should be here but it was not working when we last tested it.
This is the post that taught me everything I know about crossover point and shallow slopes versus steeper ones.
Marvellous stuff from Lynn Olson. 🙂
Marvellous stuff from Lynn Olson. 🙂
I would take "these" as guidelines. Distortion is not the only metric of a good speaker. There are more than one way to skin the cat and that does not include personal preferences.
