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Multi-Way Conventional loudspeakers with crossovers

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Old 29th December 2017, 10:52 AM   #121
gfiandy is offline gfiandy  United Kingdom
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I found another sweet spot with a slightly higher crossover frequency around 2KHz and the smother HF filter means excursion in the tweeter should be reduced in the crossover region. This looks to have retained the improved off axis response and has slightly improved phase response. You will need a better inductor for this response as the required inductor resistance is lower and 33uF is a large capacitor to use in a tweeter circuit as usually you want to use a polypropylene. (the 33uf pulls the response up in the crossover region and adjust phase without it, it still works but looks more like the original filter). I am not sure the extra couple of dB headroom in the crossover region is worth it.
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Old 29th December 2017, 11:07 AM   #122
gfiandy is offline gfiandy  United Kingdom
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I have extended the frequency to 40kHz in the attached plots you can see there is a very significant resonance in this tweeter at 27KHz, this is common in metal dome tweeters. A music signal should not have any significant energy in this region however this resonance is so high that harmonic distortion from lower down in the frequency range could set it off.


Some people don't find this a problem at all and just perceive this as metallic sounding or are completely unaware of its affect. However some people find this extremely fatiguing and unpleasant (I am one of those).


If you find this is a problem then a HF filter should help. I have simulated a second order HF filter so you can see the effect. The attached plots show the crossover with filter and a plot without and with the filter (you can see how it attenuates the 27KHz resonance.
Attached Images
File Type: jpg xover with HF filter.JPG (17.0 KB, 187 views)
File Type: png Scan_Speak_Peerless_DA25BG08-08_SPL 40KHz.png (33.1 KB, 184 views)
File Type: png Scan_Speak_Peerless_DA25BG08-08_SPL 40kHz filter.png (34.6 KB, 181 views)
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Old 29th December 2017, 12:40 PM   #123
dvjorge is offline dvjorge  United States
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Originally Posted by gfiandy View Post
This is a compromise, if you want to play really loud with these speakers then the max long term power would be improved by moving the crossover frequency up. However as you do this the off axis polar response will get worse and worse. Also woofers tend to distort in this region as the cone has stopped moving as one and breaks up with different sections of the cone moving at different time. As the cone goes more and more into cone break up they resonate and the cone starts to ring like a bell this causes energy storage and poor trasient response.

The tweeter you have chosen seems to have been designed with running at relatively low frequencies in mind, hence the 2k power bandwidth measurement. Moving it another 200Hz lower is unlikely to cause any power problems as the tweeter is quite sensitive and if you look at the filter electrical responses you can see the filter is already attenuating quite alot at the Xover frequency. Combining this with the extra order of filtering should give you the full power response. What is much more difficult to predict is how the distortion performance will behave. As you increase cone excursion on the tweeter it will distort more and the lower the frequencies you run into it will increase the excursion. I usually find for home use using as much of the range of the tweeter as possible gives a lower distortion, better transient response design which sounds better, typically better sound than running the woofer higher. The trade off is that it might not behave as well at very very high power levels, but as this design is quite sensitive anyway at about 92dB, you will get alot of sound for the input power.

Its my best guess, I can’t promise it will work well in all circumstances but I think it will give you a good compromise between sound quality, transient response, polar response, power response and distortion. If I were making this design I would go with the more complex crossover.

I will look to see if you can shift the crossover up to 2K with this design by only changing the caps (as this it is typically cheaper and easier to get hold of capacitors) which would give you the option of trying both however I think I found the phase was getting poor.
I don't have words to thank you for all your help. I am learning a lot with your explanations and also having the possibility of building the speakers with a solid help. As I said before, I had the idea that designing a two way speaker it was better to crossover it as high as possible to limit the amount of mid range going to the tweeter. I see your experience is different for home use. In any case, playing with the crossover, we can change the way the drivers are set up, but we need to have range with both drivers. I was looking to Part Express and found they have a line of speakers, Dayton Audio, where they have woofers going as high as 7000 Hz. They aren't very expensive but I don't have any idea about the quality of those drivers. I think that having a woofer that responds as high as 4K Hz or more and a tweeter that can be set as low as 2k Hz, we have enough range to change the crossover in case it be necessary. I mean more possibility of adjusting the design after listening to it. However, if the selected woofer has a top of 2K Hz, it forces you to crossover at that point or lower and there is not margin to play. Anyway, I am very excited and hoping to begin the project soon.

Last edited by dvjorge; 29th December 2017 at 12:47 PM.
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Old 29th December 2017, 01:06 PM   #124
dvjorge is offline dvjorge  United States
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People speak good about Dayton here :

Dayton drivers vs. ScanSpeak and Seas?

What do you think of this one ?? It responds to 4000 Hz

Dayton Audio DS215-8 8" Designer Series Woofer Speaker

Last edited by dvjorge; 29th December 2017 at 01:10 PM.
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Old 29th December 2017, 06:25 PM   #125
gfiandy is offline gfiandy  United Kingdom
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This speaker seems to have reviewed well but I have some concerns about it. The plots have been smoothed, it always a bit misleading to compair unsmoothed plots with smoothed ones. There could be short peaks in the response that we cant see and the peaks we can see might be worse for short frequecy spans

The cone break up at 1khz looks like it is resonating quite strongly, notice the disturbance in the impedance plot at the same frequency. This is indicative of resonance in the cone and thus energy storage causing poor transient response. You always get a bit of this but it seems quite high in this driver. It might sound quite musical depending on the behaviour of the resonance but it is not accurate and usually smears the image slightly. See the regions I have circled in the plots.

If it is especially cheap it might be worth putting up with these faults and designing to minimise the effects but they would be quite hard to mask in the crossover.
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Old 29th December 2017, 06:36 PM   #126
globalplayer is offline globalplayer  Germany
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Also Le is on the upper end of the spectrum for sq with this Dayton driver.
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Old 29th December 2017, 06:48 PM   #127
dvjorge is offline dvjorge  United States
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Originally Posted by gfiandy View Post
This speaker seems to have reviewed well but I have some concerns about it. The plots have been smoothed, it always a bit misleading to compair unsmoothed plots with smoothed ones. There could be short peaks in the response that we cant see and the peaks we can see might be worse for short frequecy spans

The cone break up at 1khz looks like it is resonating quite strongly, notice the disturbance in the impedance plot at the same frequency. This is indicative of resonance in the cone and thus energy storage causing poor transient response. You always get a bit of this but it seems quite high in this driver. It might sound quite musical depending on the behaviour of the resonance but it is not accurate and usually smears the image slightly. See the regions I have circled in the plots.

If it is especially cheap it might be worth putting up with these faults and designing to minimise the effects but they would be quite hard to mask in the crossover.
The good reviews and technical data called my attention but I don't have the resources neither knowledge to judge it right. The price is half of the Scanspeak. There are other Dayton drivers with good reviews. I would like to find a woofer with a frequency response higher than 2000 Hz, no matter if the crossover be designed to less than 2000 Hz. I would like to feel safe in case a live test doesn't sound the way I like. Having a woofer with more mid-range allow to increase the crossover point and to release the tweeter in any case. Maybe it isn't necessary but the possibility is there.
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Old 29th December 2017, 07:08 PM   #128
dvjorge is offline dvjorge  United States
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This is the other option I found with Dayton. But, again, I don't know how good it may be. The price is $30.00 less than the Scanspeak.

Dayton Audio RS225P-8A 8" Reference Paper Woofer 8 Ohm

The reviews are good and I like the paper cone. This belongs to its reference line.

Last edited by dvjorge; 29th December 2017 at 07:11 PM.
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Old 29th December 2017, 07:23 PM   #129
globalplayer is offline globalplayer  Germany
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The above driver has low Qms.
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Old 29th December 2017, 08:07 PM   #130
dvjorge is offline dvjorge  United States
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The above driver has low Qms.
I understand the low Qms doesn't have the last word. Qts is more important according to some articles I read. For instance one of them says it :


Qms will tend not to make much of a difference, since the forces arising from mechanical properties o the cone and suspension will be small compared to the loading caused by a nice enclosure and by the electrical properties.

Reading this old discussion, I am still confused :

The significance of high Qms..?

Last edited by dvjorge; 29th December 2017 at 08:21 PM.
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