Very nice looking build.
Looks like you are using the drivers from the bibs? If so how would you compare the sound of the two speakers, bass, mids, highs, and presentation?
Thanks
Ed
Yes I saw and stated no drivers in the bib.
Rather vague answer, are you a political speech writer?
Ed
Thanks, I can accept that. I hope you like them. We all seek different things in audio.
I like building and experiencing, and learning. I also seek more refinement and better musical enjoyment. I also like simple things, and often find that it is way too easy to over engineer something.
When I made my first open baffle I was pleasantly surprised, but never was happy with the bass. This thread and Martin's other work had rekindled that interest.
Cheers
Ed
Has anyone tried changing the So/SL geometry of the H-Frame?
Using Martin's Model it looks like reducing the size of the rear opening can reduce the rising response.
Adding “wedges” to the driver side to reduce the final opening to 8x16 may be an easy option. Or does the expansion from So to SL need to be linear?
Using Martin's Model it looks like reducing the size of the rear opening can reduce the rising response.
Adding “wedges” to the driver side to reduce the final opening to 8x16 may be an easy option. Or does the expansion from So to SL need to be linear?
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netbug:
I'm having trouble replicating your results. I assume because you used a So and SL of 16x16 and 8x16 you're looking at the Alpha 15A in an H-frame and not the Goldwood GW-1858. If so did you change the Terminus Geometry Input so that Wmth = 8 in instead of 16? I'm using the H_Frame_Corner_7_03_09 worksheet.
I'm having trouble replicating your results. I assume because you used a So and SL of 16x16 and 8x16 you're looking at the Alpha 15A in an H-frame and not the Goldwood GW-1858. If so did you change the Terminus Geometry Input so that Wmth = 8 in instead of 16? I'm using the H_Frame_Corner_7_03_09 worksheet.
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I'm using the same sheet.
Martin indicated that the So-Sl transition is linear so my earlier models are junk. I *think* i've figured out how to model the wedges in the rear cavity. If I figure this out it may be possible to install either solid wedges or maybe even hinged flaps for tuning.
So n_open can be 1, but that still means two section lines....
I'm also using the goldwood 215/8/40.
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Great news. I think you could make them removable in a test mule situation, have fun, and learn.
Keep us informed!
cheers
Ed
Hi Guys.
I really want to add something to this difficult issue.
I know at least two guys who switched from an single Alpha 15A to single mid-qts driver (Selenium 15PW3 or Eminence Delta) or even double low-qts drivers (qts- 0.35).
When I asked why both of them could not put it in words. They claimed that there where a lot less low bass but these new speakers just sounded right. More interesting and precise. Faster.
I've made some simulations and added some experience from building car subwoofers.
The results showed me that one of the things that really matter is Group Delay in milliseconds.
We can call a vented subwoofer quick enough if it's getting below 10ms.
On the other hand a quick small closed sub is about 5ms.
If you want a really quick bass, that is used on SQL contest (sound quality) - you should get a low qts driver (below 0,4), put it in closed box and get group delay about 2ms at 50hz.
In the last case though you won’t go down flat even to 60hz.
Do you get the analogy?
Alphas are around 7ms at fs (41hz)
We have 3 ways to choose. Each of them has trade offs.
1. Good extension and speed, but low SPL
2. Good speed, high SPL but poor extension.
3. High SPL, good extension but poor speed (high QTS drivers)
There's one more thing.
Why oh why so many people like Alphas so much ?
I think I know why.
This high Group Delay occurs around FS of the driver. If we put Alpha in H/U Frame we lower FS to about 30hz, so we're getting slower bass between 20hz-70hz. Everything above is as quick as low qts drivers.
Now - how often do we go down that low ?
It depends on what kind of music we prefer.
The other thing is that most of us is trying to match Alpha's with ultra fast and ultra light fullrangers. So it becomes even more difficult
It also depends on our expectations and the tradeoffs that we are able to give away and which ones we are not.
That's it. Sorry for my lousy English. I hope I made it all clear to you guys.
Thanks for tackling the issue Fakamada. Recently I've been using the Jensen C15K 15" bass guitar driver instead of the Pyles. It is 1mm throw, qts .86, mms 43g, magnet 50oz, fs 73hz, 101 db from 100-200hz etc.
In room response is surprising - at least 12 hz below fs if I take advantage of the walls in the room. Now it's not a low bass driver and I'm not trying to use it as such. But let me tell you, in terms of quickness and bass detail in OB, it WALKS ALL OVER the Alpha 15 (and the Pyles for that matter) from 60-200hz. It produces the best bass and midbass I've ever heard. And it barely moves. Look at the moving mass 43g! And think of how good the bl curve must be with an average of 1mm pk to pk excursion! How many 15" woofers are this low on mms and yet so beefy on the motor? (double that of the Alpha.)
Many people are quite pleased with the Alphas. I think that's great. Fakamada claims the delay/ rise time/ settle time whatever of the Alphas is not that bad. Well, they sound like garbage to me.
In room response is surprising - at least 12 hz below fs if I take advantage of the walls in the room. Now it's not a low bass driver and I'm not trying to use it as such. But let me tell you, in terms of quickness and bass detail in OB, it WALKS ALL OVER the Alpha 15 (and the Pyles for that matter) from 60-200hz. It produces the best bass and midbass I've ever heard. And it barely moves. Look at the moving mass 43g! And think of how good the bl curve must be with an average of 1mm pk to pk excursion! How many 15" woofers are this low on mms and yet so beefy on the motor? (double that of the Alpha.)
Many people are quite pleased with the Alphas. I think that's great. Fakamada claims the delay/ rise time/ settle time whatever of the Alphas is not that bad. Well, they sound like garbage to me.
The only way to have lightning speed is to use drivers like this Jensen or vintage woofers from Isophon, RFT or others + Sub with Plate amp (can be open baffle).
The best bass I've ever heard was from TAD active, closed subwoofers. They're about 200 liters each, low QTS, but driven only 20hz-60hz, so you're not hearing any fall of effinciency caused by low QTS.
I'm currently running Selenium 15PW3 wich is a compromise. It's not lightning fast and is not going down to 30's but it's pretty good (qts 0,7)
The best bass I've ever heard was from TAD active, closed subwoofers. They're about 200 liters each, low QTS, but driven only 20hz-60hz, so you're not hearing any fall of effinciency caused by low QTS.
I'm currently running Selenium 15PW3 wich is a compromise. It's not lightning fast and is not going down to 30's but it's pretty good (qts 0,7)
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