Hi All.
The cold weather has arrived, and its time to revisit one of the many projects that have spent the warmer months on hiatus in my basement. I would like to use the parts listed in the title to put together a two way speaker set. As per the title, these comprise a pair of Peavey FH1 bass bins with a soon to arrive pair of Eminence Kappa 15C, and a pair of Altec 511B with Renkus Heinz SSD1800 drivers. Some time ago, I tried to use a Behringer Super-X Pro CX3400 as an active crossover for these components, utilizing a DIY pair of stereo tube amps, but found that the noise floor of this setup was unacceptable as there was audible hiss from my listening position. Also, ignoring the hiss, my reference La Scalas sounded obviously superior. That said, I would like to pursue an all horn two way design utilizing a passive crossover. I have researched a number of passive crossover options, and would like your opinions on the two that I have narrowed it down to, as well as any advice you may have on the topic. I am currently looking at the ALK Engineering AP12-500 or AP12-600, or the Jean Hiraga inspired crossover (530 HZ) for Altec VOTT A7-500-8 contained in this link, http://www.vtaf.com/id107.html (modified to take into account the Kappa 15C's 4 Ohm instead of the contained schematic's 8 Ohm woofers). The attraction of the latter Hiraga inspired crossover is that it includes a filter that will flatten the dropping frequency response of the 811B/RH SSD1800 combo, while the ALK AP12xxx is a proven product that is in more in line with a normal Klipsch Heritage crossover. It is my intention to DIY the crossover for these speakers.
Any input/advice you may have on these two choices, and any opinions as to the suitability of each crossover for my application, would be much appreciated.
The cold weather has arrived, and its time to revisit one of the many projects that have spent the warmer months on hiatus in my basement. I would like to use the parts listed in the title to put together a two way speaker set. As per the title, these comprise a pair of Peavey FH1 bass bins with a soon to arrive pair of Eminence Kappa 15C, and a pair of Altec 511B with Renkus Heinz SSD1800 drivers. Some time ago, I tried to use a Behringer Super-X Pro CX3400 as an active crossover for these components, utilizing a DIY pair of stereo tube amps, but found that the noise floor of this setup was unacceptable as there was audible hiss from my listening position. Also, ignoring the hiss, my reference La Scalas sounded obviously superior. That said, I would like to pursue an all horn two way design utilizing a passive crossover. I have researched a number of passive crossover options, and would like your opinions on the two that I have narrowed it down to, as well as any advice you may have on the topic. I am currently looking at the ALK Engineering AP12-500 or AP12-600, or the Jean Hiraga inspired crossover (530 HZ) for Altec VOTT A7-500-8 contained in this link, http://www.vtaf.com/id107.html (modified to take into account the Kappa 15C's 4 Ohm instead of the contained schematic's 8 Ohm woofers). The attraction of the latter Hiraga inspired crossover is that it includes a filter that will flatten the dropping frequency response of the 811B/RH SSD1800 combo, while the ALK AP12xxx is a proven product that is in more in line with a normal Klipsch Heritage crossover. It is my intention to DIY the crossover for these speakers.
Any input/advice you may have on these two choices, and any opinions as to the suitability of each crossover for my application, would be much appreciated.
You'll save yourself a lot of money & grief if you first buy a USB based measurement mic ( before buying any passive networks ).
The umik-1 test mic is one of the most popular test mics.
Using a test mic along with some free ( acoustic test ) software ( such as REW ) will allow you to test out the notion that your driver/horn combo will actually make it down to 500hz and therefore support such a low crossover point ( I don't think it will ).
Here's the RH-SD1800 cut-sheet
The plane wave graph displayed within that info sheet shows that the driver is pretty flat down to around 800hz.
- That's the lowest crossover point I would choose ( based on the available info ).
🙂
The umik-1 test mic is one of the most popular test mics.
Using a test mic along with some free ( acoustic test ) software ( such as REW ) will allow you to test out the notion that your driver/horn combo will actually make it down to 500hz and therefore support such a low crossover point ( I don't think it will ).
Here's the RH-SD1800 cut-sheet
The plane wave graph displayed within that info sheet shows that the driver is pretty flat down to around 800hz.
- That's the lowest crossover point I would choose ( based on the available info ).
🙂
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EarlK: Thanks for the info and the suggestion to get a USB microphone. Based upon the attached Hornresp sim (thanks Karlson3!), it seems that I could use a higher crossover than my intended 500-600HZ. This sim, combined with the frequency response contained in the RH SD1800 cut-sheet, would indicate that the combo would work at a 750-800HZ crossover point. My concern about the FH1/15C combination was that it wouldn't go high enough to crossover at a higher frequency, but the sim seems to indicate that it will. The RH SD1800 drivers will work better at that frequency as well. Do you think that, given the acoustic roll-off of the FH1/15C combo, I could use a first order crossover on the woofer portion, and a second order crossover on the 511B/RH SD1800 portion, both at 750-800HZ?
I have a few other general questions as well that relate to my specific application:
1. When using a 4 Ohm woofer and a 16 Ohm tweeter together, is the output of the tweeter reduced relative to the woofer's? If I understand this correctly, and I may not, the output of the 16 Ohm tweeter will be 6 DB lower than it would normally be if both components were 4 Ohms.
2. With respect to the crossover design, does the loading of the 15C woofer by the FH1 horn come into play when calculating component values for the crossover with respect to how many Ohms the combination presents? From my reading, the FH1/15C combo has a combined impedance of 6.5-8 Ohms, depending on the source of the information. The 15C on its own is nominally 4 Ohms.
3. Can a shaping/notch filter, as contained in the Jean Hiraga inspired crossover referred to in my first post, be added to the tweeter portion of any crossover without causing issues?
I have a few other general questions as well that relate to my specific application:
1. When using a 4 Ohm woofer and a 16 Ohm tweeter together, is the output of the tweeter reduced relative to the woofer's? If I understand this correctly, and I may not, the output of the 16 Ohm tweeter will be 6 DB lower than it would normally be if both components were 4 Ohms.
2. With respect to the crossover design, does the loading of the 15C woofer by the FH1 horn come into play when calculating component values for the crossover with respect to how many Ohms the combination presents? From my reading, the FH1/15C combo has a combined impedance of 6.5-8 Ohms, depending on the source of the information. The 15C on its own is nominally 4 Ohms.
3. Can a shaping/notch filter, as contained in the Jean Hiraga inspired crossover referred to in my first post, be added to the tweeter portion of any crossover without causing issues?
Attachments
This simulation shows that your 16ohm HF driver ( 108db ) won't quite keep up with the woofer ( when passively crossed over + EQed for some linearity > though it's most likely to be close enough in the real world ) .
You can't design crossovers without having the actual ac impedances of the drivers in the horns.
REW ( or ARTA ) with a simple test jig can measure these impedances ( & then export the values as a .zma file to be used within network simulation software.
🙂
EarlK: Thanks for the help with this. It appears that the impedance of the 15C in a folded horn such as a La Scala, Belle ot FH1 is between 5.6-6, based on a couple of different sources. While I am interested in crossover design, I’m in the midst of a huge learning curve with my primary audio hobby, which is building tube amps, so getting into crossovers is probably going to put me over the edge. I will base my design on this figure for now.
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