>>> I measured the fs of my four Alpha 15A drivers to be an average of 41 Hz. When you put them in the H frame the air in the frame loads more mass onto the driver's cone.
Thanks Martin. Pretty cool actually.
>>> The big driver moves a lot of air by displacing just a little distance, I think this helps with the bass transients.
Based on my listening comparison with the sealed sub i have on hand (which was a well respected subwoofer driver, the ACI SV12 (cost $150), i'd have to agree with you. The SV12 sounds slow and muddled when working with my BIBs... with other more typical box speakers they offer great, detailed, low bass extension. I was worried the relatively inexpensive Alpha 15s would not have any sort of detail or quality of sound. In fact, i was concerned they would suck actually. Feels like i bought a lot of cardboard connected to a cheap metal frame. Certainly not a hi tech looking driver - but purposeful indeed!
>>> How much are the Alpha 15A's moving on heavy bass music?
Well, i can make them move if i turn up their amp but they overpower the rest of the system. When i first tried dialing them in i lightly touched them and turned up their amp until i heard them AND felt them vibrate. This was too much in my small listening room. They barely require any power at all! When i finally got them to sound just right with my BIBs they were not moving. I didn't think they were working. But I heard their contribution and my system sounded rich and full in the bass... to make sure, i disconnected the main speakers only to hear the low rumbly moans of the Alpha 15s... they were working perfectly. So the answer is no, when properly integrated with my main speakers they do not move much at all and seem not to be working at all. During bass rich material (like the Sade CD and a Jack Johnson CD) they slightly vibrate. Clearly, they are barely being taxed and have tremendous headroom to spare. They are probably overkill.
But when you consider the sound they produce and how they enhance the low end of my main speakers, their relatively low price, their small size (the H-Frames are probably as small as can possibly be considering these woofers are 15 inches) they are really an extremely efficient home subwoofer system.
The 18 inch Goldwoods must sound awesome! I just couldn't imagine them in my room... they would look too big. The smaller 15 inch Alpha's really do the trick for me. Probably could have built something using appropriate 12 inch drivers and gotten good sound too. But now that i have heard what two 15 inch drivers do by way of adding an effortless bass, huge sense of scale (you can practically hear the size of the hall the orchestra is playing in) and the effortless ease of detail making instruments sound more real, there's no turning back to sealed up, long throw subwoofer boxes. Uhg!
Whether it's Eminence, Goldwood or another driver with a Qts of around 1, amazing sound can be had in very efficiently packaged stereo subwoofers for not a lot of money... and their performance is incredible... it's all in the science.
Thanks for a GREAT PROJECT Martin! It's the one i nearly never built. I was thinking about building these for many months as i was recovering from my stomach surgery... it's been nine and a half months since the operation... i bought the drivers, amp and cut up the wood, saved them for when i felt better, built them last weekend and have been enjoying them since.
Godzilla
Thanks Martin. Pretty cool actually.
>>> The big driver moves a lot of air by displacing just a little distance, I think this helps with the bass transients.
Based on my listening comparison with the sealed sub i have on hand (which was a well respected subwoofer driver, the ACI SV12 (cost $150), i'd have to agree with you. The SV12 sounds slow and muddled when working with my BIBs... with other more typical box speakers they offer great, detailed, low bass extension. I was worried the relatively inexpensive Alpha 15s would not have any sort of detail or quality of sound. In fact, i was concerned they would suck actually. Feels like i bought a lot of cardboard connected to a cheap metal frame. Certainly not a hi tech looking driver - but purposeful indeed!
>>> How much are the Alpha 15A's moving on heavy bass music?
Well, i can make them move if i turn up their amp but they overpower the rest of the system. When i first tried dialing them in i lightly touched them and turned up their amp until i heard them AND felt them vibrate. This was too much in my small listening room. They barely require any power at all! When i finally got them to sound just right with my BIBs they were not moving. I didn't think they were working. But I heard their contribution and my system sounded rich and full in the bass... to make sure, i disconnected the main speakers only to hear the low rumbly moans of the Alpha 15s... they were working perfectly. So the answer is no, when properly integrated with my main speakers they do not move much at all and seem not to be working at all. During bass rich material (like the Sade CD and a Jack Johnson CD) they slightly vibrate. Clearly, they are barely being taxed and have tremendous headroom to spare. They are probably overkill.
But when you consider the sound they produce and how they enhance the low end of my main speakers, their relatively low price, their small size (the H-Frames are probably as small as can possibly be considering these woofers are 15 inches) they are really an extremely efficient home subwoofer system.
The 18 inch Goldwoods must sound awesome! I just couldn't imagine them in my room... they would look too big. The smaller 15 inch Alpha's really do the trick for me. Probably could have built something using appropriate 12 inch drivers and gotten good sound too. But now that i have heard what two 15 inch drivers do by way of adding an effortless bass, huge sense of scale (you can practically hear the size of the hall the orchestra is playing in) and the effortless ease of detail making instruments sound more real, there's no turning back to sealed up, long throw subwoofer boxes. Uhg!
Whether it's Eminence, Goldwood or another driver with a Qts of around 1, amazing sound can be had in very efficiently packaged stereo subwoofers for not a lot of money... and their performance is incredible... it's all in the science.
Thanks for a GREAT PROJECT Martin! It's the one i nearly never built. I was thinking about building these for many months as i was recovering from my stomach surgery... it's been nine and a half months since the operation... i bought the drivers, amp and cut up the wood, saved them for when i felt better, built them last weekend and have been enjoying them since.
Godzilla
Godzilla said:
I worked for a manager a long time ago and he had a canned saying he used all the time.
"Better is the enemy of good enough."
The Eminence drivers are very high quality in my opinion, consistent specs from unit to unit and they do the job below 200 Hz. For that frequency range they are good enough. Adding more expense, like a cast frame or fancy cone, to the driver probably does not buy you significantly more performance. People are way to concerned about status and looks with drivers and pay more when sometimes the performance impact is not that great.
That said, I prefer the Betas. The extra $10 dollars buys a bigger
magnet, and it's worth it.
😎
magnet, and it's worth it.
😎
Thanks for pointing that out.
Parts Express charges to ship the Alpha...shipping the Beta is at no charge. For a pair the Betas are $6 more.
Yes, it's worth it. 😉
Parts Express charges to ship the Alpha...shipping the Beta is at no charge. For a pair the Betas are $6 more.
Yes, it's worth it. 😉
I called into work today saying i did not feel well... listened to music for a few hours then went into work around 2:30... I recommend doing this every now and then to everyone. Spent a very relaxing morning with Eva Cassidy and Ella... bass sounded fuller, richer and better than ever!
Godzilla
Godzilla
Nelson Pass said:
I have the Betas, but I haven't been quite happy with them until I added Graham's T-bass circuit...
Never heard the Alphas, though...
Pyle PDW21250 are very nice woofers.
I got a pair recently. they are about 0.7qts
very smooth impedance curve and no humongous cone breakups,
easily can be crossed at 200hz. I am using them on 24in x 24in plywood baffles.
I got a pair recently. they are about 0.7qts
very smooth impedance curve and no humongous cone breakups,
easily can be crossed at 200hz. I am using them on 24in x 24in plywood baffles.
More pics of the H-Frame with 165k BIB. It's not easy to see but if you look carefully you will notice a BIB-Wing. I only hear a difference when the wing is fully extended and flush with the main baffle. They fold back but i usually leave them open. The midrange seems fuller when the wing is open. But the difference is subtle. It's possible the sound changes because the rear firing tweeter may be effected by the wing somehow. Sometimes i feel like removing them since the change is small and they clunk up their looks.
Will add low feet (probably the kind used for sliding furniture around on carpet) to the H-Frames. Have no clue how to finish them... I may have a little fun with color. Any suggestions welcome.
Godzilla
Will add low feet (probably the kind used for sliding furniture around on carpet) to the H-Frames. Have no clue how to finish them... I may have a little fun with color. Any suggestions welcome.
Godzilla
Attachments
The H-Frame on the other side. Note the 12" powered sub in the black box... very heavily braced inside... heavy to move around... It has a bulky uninteresting look. The H-Frames look interesting are light and easy to slide around. The Alpha 15's magnet is small compared to the SV12 subwoofer. I haven't really played with H-Frame positioning, just put them where the fit and played with the crossover and volume. A few hours of tweaking and you're set.
The coffee container contains an inexpensive Eminence compression tweeter and the smallest Dayton Audio waveguide. Crossover set to 11khz with an L-pad to adjust. The way i have them set you can barely hear them but when i turn them off i miss them. They add a detailed treble and air i like. I always liked super tweeters tho. I already have wood cut up to make small boxes for the tweeter. That's my next project. Probably sit them atop the H-Frames and be done with this system for a while... next i need to improve my office system.
Love the H-Frame sound! Full, rich and dynamic. I'm sure there are other well suited drivers for the chore and bet they all sound great. Best thing is they cost less to build than the powered sub they will be replacing.
Again, finishing ideas welcome for the H-Frames.
Godzilla
The coffee container contains an inexpensive Eminence compression tweeter and the smallest Dayton Audio waveguide. Crossover set to 11khz with an L-pad to adjust. The way i have them set you can barely hear them but when i turn them off i miss them. They add a detailed treble and air i like. I always liked super tweeters tho. I already have wood cut up to make small boxes for the tweeter. That's my next project. Probably sit them atop the H-Frames and be done with this system for a while... next i need to improve my office system.
Love the H-Frame sound! Full, rich and dynamic. I'm sure there are other well suited drivers for the chore and bet they all sound great. Best thing is they cost less to build than the powered sub they will be replacing.
Again, finishing ideas welcome for the H-Frames.
Godzilla
Attachments
hi Martin - is the 18" Goldwood as clean sounding as Eminence? - do you get good bowed bass and cello?
To Nelson Pass and Vix. How do you deal with the betas. I have four, intending to use two per side but they run out of xmax very quickly in the modelling software. The house is open plan and I hope to use them facing across the full width, about 10 meters, seated about 3 meters from the baffle which would be about 900mm from the wall behind them. This wall is mainly glass, 2 meters high with only vetrical louvre type blinds. I am looking at a 10" PHL for mids and maybe some sort of horn for the highs. All high sensitivity.jamikl
jamikl said:
Flat baffle, around 150 Hz first order low pass, T-bass circuit:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=130679
Just my
freddi said:
I don't know how to answer those questions since I have not listened to the two drivers in the same time period or in the same style of enclosure or baffle. I would think that bowed bass and cello would be primarily higher in frequency then the low bass I am trying to achieve so maybe the driver handling > 200 Hz might be a bigger player. Since I listen to mostly acoustic jazz, I am more familiar with plucked bass and both drivers seemed to do a good job of contributing to reproduce that sound and transient.
Math questions
Hey,
Its finally time to convert my desktop OB's (corkboard baffles with cardboard U sides) to a more solid implementation.
The woofer is the Goldwood 8028 8" and has been working out great in this application.
I'm going to build an H-Frame and am trying to determine the depth such that the resonant frequency will be above my 100Hz crossover.
There are two items in Martin's "Comparison of the Bass Performance of Passive Open Baffle, U Frame and H Frame Speakers" white paper that need clarification:
- What does the "depth of the cavity" (7.5") refer to in an H Frame? The depth on one side or the sum of both sides?
- How is r_effective determined (9")?
Thanks
Hey,
Its finally time to convert my desktop OB's (corkboard baffles with cardboard U sides) to a more solid implementation.
The woofer is the Goldwood 8028 8" and has been working out great in this application.
I'm going to build an H-Frame and am trying to determine the depth such that the resonant frequency will be above my 100Hz crossover.
There are two items in Martin's "Comparison of the Bass Performance of Passive Open Baffle, U Frame and H Frame Speakers" white paper that need clarification:
- What does the "depth of the cavity" (7.5") refer to in an H Frame? The depth on one side or the sum of both sides?
- How is r_effective determined (9")?
Thanks
Take a close look at the layouts on the bottom of page 4 in his white paper. The way I read those layouts for an H frame the speaker has 7.5 inches in front and back of it. For the U frame it would be 7.5 inches in back of the speaker.
Re: Math questions
The depth of the cavity is per side. The H frame is 7.5" deep in front of the center baffle and 7.5" deep hehind the center baffle. The driver is mounted to the 0.75" thick center baffle. Total external depth of the H frame is 7.5" + 0.75" + 7.5" = 15.75"
To calculate r_effective you want to think of a circle with the same area as the square opening. So if I do my math right, I think this becomes.
r_effective = [(width x height)/phi]^0.5
r_effective = [(16" x 16")/3.14159...]^0.5
r_effective = 9.027" ~ 9"
Hope that helps,
boudy said:
The depth of the cavity is per side. The H frame is 7.5" deep in front of the center baffle and 7.5" deep hehind the center baffle. The driver is mounted to the 0.75" thick center baffle. Total external depth of the H frame is 7.5" + 0.75" + 7.5" = 15.75"
To calculate r_effective you want to think of a circle with the same area as the square opening. So if I do my math right, I think this becomes.
r_effective = [(width x height)/phi]^0.5
r_effective = [(16" x 16")/3.14159...]^0.5
r_effective = 9.027" ~ 9"
Hope that helps,
That's extremely helpful, thanks
Working through some possible values has clarified how this all fits together.
Now I need to figure out the roll-off of the full-range driver's response due to its baffle and set the depth of the H-Frame appropriately. I'll probably need to adjust the X-over point.
I would expect that tapering the vertical sides of the H-Frame would reduce and broaden the peak and could provide finer control over the overall response. I'd like to see the formula for that!
Thanks for sharing.
Working through some possible values has clarified how this all fits together.
Now I need to figure out the roll-off of the full-range driver's response due to its baffle and set the depth of the H-Frame appropriately. I'll probably need to adjust the X-over point.
I would expect that tapering the vertical sides of the H-Frame would reduce and broaden the peak and could provide finer control over the overall response. I'd like to see the formula for that!
Thanks for sharing.
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