Hi All
I've obtained a set of PM6As quite a number of years ago, with the idea of going for one of the popular horn designs. Time and lack of woodwork skills put a stop to that idea and resulted in the Lowthers going into storage 🙁
However, thanks to this and other forums I've pretty much been convinced OB is the way to go and on the plus side it should be do-able with my almost non existent woodwork skills 😀
But, Lowthers on their own would be a bit bass shy. I believe the trend is to either go with Hawthorne Augies (one each baffle) or else Eminence Alpha 15As (2 each baffle). Coming from a car audio environment, I know how fast and detailed high Q (freeair subs) could be, so with my noob knowledge 🙂 , I totally agree with MJK in his view on OB + high Q drivers.
So, finally, my question: taken my current kit which is a LEAK Stereo 60, Decware SE34I.2 and the Lowthers, what will be the simplest (read cheapest 😀 ) way to integrate some good fast and detailed low end into the OBs? I only have a passive pre-amp in half working condition so I would rather stay with the build in pre-amp in the Decware for now.
I would like to keep the signal path as simple as possible. I was leaning towards pairing the PM6As with two 15As each. Maybe running with the 15As and PM6s from the Decware only although I am not sure how to wire that up to get the most from the woofers: 15As in serial with PM6A in parallel or if the Decware will have the legs to power the lot.
Any case, anybody with similar systems running? Suggestions?
Cheers
Andre
I've obtained a set of PM6As quite a number of years ago, with the idea of going for one of the popular horn designs. Time and lack of woodwork skills put a stop to that idea and resulted in the Lowthers going into storage 🙁
However, thanks to this and other forums I've pretty much been convinced OB is the way to go and on the plus side it should be do-able with my almost non existent woodwork skills 😀
But, Lowthers on their own would be a bit bass shy. I believe the trend is to either go with Hawthorne Augies (one each baffle) or else Eminence Alpha 15As (2 each baffle). Coming from a car audio environment, I know how fast and detailed high Q (freeair subs) could be, so with my noob knowledge 🙂 , I totally agree with MJK in his view on OB + high Q drivers.
So, finally, my question: taken my current kit which is a LEAK Stereo 60, Decware SE34I.2 and the Lowthers, what will be the simplest (read cheapest 😀 ) way to integrate some good fast and detailed low end into the OBs? I only have a passive pre-amp in half working condition so I would rather stay with the build in pre-amp in the Decware for now.
I would like to keep the signal path as simple as possible. I was leaning towards pairing the PM6As with two 15As each. Maybe running with the 15As and PM6s from the Decware only although I am not sure how to wire that up to get the most from the woofers: 15As in serial with PM6A in parallel or if the Decware will have the legs to power the lot.
Any case, anybody with similar systems running? Suggestions?
Cheers
Andre
I heard a system with one beta-15A per side (on OB) yesterday.
Believe me when I say that one 15" driver per side can be more than enough. Makes it cheaper for you, too.
If you use a passive crossover at the speaker end, it's easy enough to cross around 300Hz. Probably somewhere near ideal.
You shouldn't need any/much eq with a set-up like that, either.
Chris
Believe me when I say that one 15" driver per side can be more than enough. Makes it cheaper for you, too.
If you use a passive crossover at the speaker end, it's easy enough to cross around 300Hz. Probably somewhere near ideal.
You shouldn't need any/much eq with a set-up like that, either.
Chris
You may find this thread interesting where Nelson Pass experiments with OB using the PM6As and the Feastrex D9nf's
http://www.diyaudio.com/forums/full-range/122748-feastrex-fun.html
http://www.diyaudio.com/forums/full-range/122748-feastrex-fun.html
According to MJK, he was fighting the efficiency of his Lowthers, and so not only did he have to use two Alpha 15A's per side, he also had to make the baffle extremely wide (60"?) and then on top of that, I believe he had to add bass boost through his active EQ (which I think is a dbx Driverack). But that's because he didn't want to pad down the Lowthers, and that's why next time he deliberately specified a ~90db fullranger.
Next step, I think, would be to decide active or passive on the crossover.
Next step, I think, would be to decide active or passive on the crossover.
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I use one 15" Alpha per side and it's plenty when paired with the 93db Tangband 1808. But mine setup powers the woofers with a separate amp.
Boomer Open Baffle Speaker Kit
I can only imagine how powerful and rich two Alpha's per side sound!
Godzilla
Boomer Open Baffle Speaker Kit
I can only imagine how powerful and rich two Alpha's per side sound!
Godzilla
Thanks Chris. Was that driving the LF and HF drivers from the same amp? Wonder if the beta-15A would keep up with the PM6A or if it would need/eq or else a bi-amp.
As a starting option I am also trying to get my head around driving two pairs of alpha-15As plus Lowthers from the same amp. Mm, how to present 8ohm by 8ohm by 8 ohm to the amp and still get good SPL from all drivers... 😕
A
Thanks for the link bluemartini, (nice link that), and I like the ferarri/lotus elise etc. cars discussion in the thread 😀
Andre,
The Augie is not very sensitive at 89 db 1w/1m, so I can't imagine you'd have any luck running them with a passive crossover and a single amp. Nelson Pass appears to have success using higher efficiency woofers with the Lowther, so maybe Alpha 15's would work. I don't know the details of all of their units, but Decware amps often like low impedance loads, so two Alpha 15's could work well.
Don't just look at the efficiency spec for a given woofer, plug the numbers into a box or OB simulator. PA woofers often show significant peaking near the top of their passband, and that skews the numbers up. There are plenty of woofers that have a high number, but will make less noise in an OB than the Alpha.
It sounds as if you are set on the high Qts route. I personally followed Pass's lead, and used a lower Q woofer. I had anticipated needing a bunch of EQ/shelving, but a simple second order slope at 80hz (like NP) seems to be working well (using the miniDSP as an active crossover). My woofers are Foster OEM's (the "Jensen") from Jack Hidley. They are great OB woofers (high sensitivity, high compliance, high excursion compared to most budget PA woofers) and only $60 each. There are certainly nicer woofers out there for bigger budgets, though.
The Augie looks like a nice woofer, but I don't know that it'll do what you want it to.
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
The Augie is not very sensitive at 89 db 1w/1m, so I can't imagine you'd have any luck running them with a passive crossover and a single amp. Nelson Pass appears to have success using higher efficiency woofers with the Lowther, so maybe Alpha 15's would work. I don't know the details of all of their units, but Decware amps often like low impedance loads, so two Alpha 15's could work well.
Don't just look at the efficiency spec for a given woofer, plug the numbers into a box or OB simulator. PA woofers often show significant peaking near the top of their passband, and that skews the numbers up. There are plenty of woofers that have a high number, but will make less noise in an OB than the Alpha.
It sounds as if you are set on the high Qts route. I personally followed Pass's lead, and used a lower Q woofer. I had anticipated needing a bunch of EQ/shelving, but a simple second order slope at 80hz (like NP) seems to be working well (using the miniDSP as an active crossover). My woofers are Foster OEM's (the "Jensen") from Jack Hidley. They are great OB woofers (high sensitivity, high compliance, high excursion compared to most budget PA woofers) and only $60 each. There are certainly nicer woofers out there for bigger budgets, though.
The Augie looks like a nice woofer, but I don't know that it'll do what you want it to.
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
Many open baffle gurus think that the woofers mentioned here do "muddy" the mids of drivers Lowther kind. Lowther America settled on Tone Tubbies and Altec designs. Lampizator likes Altecs as well. If two 15" ers seem like overkill for your room, two 12" could be ideal solution for you and integrate better with the Lowther as well.
>>> PA woofers often show significant peaking near the top of their passband, and that skews the numbers up.
They sure do!
Having lived with the Alpha's for a while i can't say they have muddy bass at all rather detailed fast bass. But i have yet to compare them to another woofer on OB so perhaps i am hearing the benefits of open baffle. I do want to build and compare a 15" driver in a cabinet to OB to hear the differences the box or lack of box makes. I will say that 15" woofers are addictive and offer a level of realism smaller woofers just don't provide. When listening to Pink Floyd's The Wall, bass always seems rich and full... but thru 15" woofers it's downright scary when the room rumbles, the drama builds and the sound envelopes you completely. I believe big bass brings you closer to what the artist is trying to convey. And my 12" powered sub that i lived with for years... that specs out deeper bass... just doesn't provide the same effect.
Godzilla
They sure do!
Having lived with the Alpha's for a while i can't say they have muddy bass at all rather detailed fast bass. But i have yet to compare them to another woofer on OB so perhaps i am hearing the benefits of open baffle. I do want to build and compare a 15" driver in a cabinet to OB to hear the differences the box or lack of box makes. I will say that 15" woofers are addictive and offer a level of realism smaller woofers just don't provide. When listening to Pink Floyd's The Wall, bass always seems rich and full... but thru 15" woofers it's downright scary when the room rumbles, the drama builds and the sound envelopes you completely. I believe big bass brings you closer to what the artist is trying to convey. And my 12" powered sub that i lived with for years... that specs out deeper bass... just doesn't provide the same effect.
Godzilla
It's easy if you have an active crossover. On the subject, I
got better results from the Eminence 15 beta - less boom,
goes a little deeper.
😎
Thanks for the input so far everybody.
nigelwright7557 - 18" yeah, I would like that, but it will really be pushing the WAF in my living room. I would hate moving my system to the garage 🙂.
Paul - 1. you are correct those Augies are not very sensitive but they can go very low which is a serious plus over the Alphas. But if I go that route I will drive the PM6As from the Decware and the Augies from a dedicated plate amp.
Paul - 2. The logical choice may be to start with two Alphas per side passive XO on all drivers. BUT, I am not sure if a 6W pch Decware will have the muscle to drive all speakers?? 😕 I was thinking 8 ohm by 8 ohm Alphas in parallel = 4 ohm + 8 ohm Lowther in parallel = 6 ohm load to the amp. makes sense??
Godzilla - I hear you. My intention is not so much earth shaking bass but more accuracy in an attempt to get as close to realistic as possible. My music preference is classical and blues/jazz. I am concerned that a single Alpha will not bring the bass to the same level other frequencies will be portrayed by the Lowthers.
Nelson - I was looking at the Betas yesterday, and was thinking the same thing. Re active XO, I was really hoping to stick to using the pre-amp on the Decware and either driving the HF and LF speakers from the Decware or else (somehow) get LF out from the Decware to power a plate amp with less efficient LF drivers such as the Augies.
So many options so little money, he he 😀
Again - thanks a gazillion everybody. Keep the feedback coming. I am very keen to get to a solution and get the OBs up and running.
Cheers
Andre
nigelwright7557 - 18" yeah, I would like that, but it will really be pushing the WAF in my living room. I would hate moving my system to the garage 🙂.
Paul - 1. you are correct those Augies are not very sensitive but they can go very low which is a serious plus over the Alphas. But if I go that route I will drive the PM6As from the Decware and the Augies from a dedicated plate amp.
Paul - 2. The logical choice may be to start with two Alphas per side passive XO on all drivers. BUT, I am not sure if a 6W pch Decware will have the muscle to drive all speakers?? 😕 I was thinking 8 ohm by 8 ohm Alphas in parallel = 4 ohm + 8 ohm Lowther in parallel = 6 ohm load to the amp. makes sense??
Godzilla - I hear you. My intention is not so much earth shaking bass but more accuracy in an attempt to get as close to realistic as possible. My music preference is classical and blues/jazz. I am concerned that a single Alpha will not bring the bass to the same level other frequencies will be portrayed by the Lowthers.
Nelson - I was looking at the Betas yesterday, and was thinking the same thing. Re active XO, I was really hoping to stick to using the pre-amp on the Decware and either driving the HF and LF speakers from the Decware or else (somehow) get LF out from the Decware to power a plate amp with less efficient LF drivers such as the Augies.
So many options so little money, he he 😀
Again - thanks a gazillion everybody. Keep the feedback coming. I am very keen to get to a solution and get the OBs up and running.
Cheers
Andre
I've had much success using 2 Alpha 15As per side with some Hawthorne Silver Iris drivers I have. I use the cheaper Behringer CX3400 active (analogue) crossover and cross them at 350 Hz. I now wish I'd gone with the DCX2496 to provide much more flexibilty.
After modelling the setup with MJK's worksheets (and adding the reflections from a side wall, rear wall and floor) and then listening to my built speakers, I beginning to think that Nelson is right. The approach using lower Qts woofers and adding bass boost may be better (by that I mean provide a flatter freq response). The Alphas in my OB end up with a response peak centered around 100 Hz and drop off rapidly below 45 Hz. Using a lower Qts woofer should provide much flatter response around 100 Hz and the bass boast will bring the response up for lower freqs. (But this will only work if you use an active crossover).
I think that some complaints about "slow bass" or "tubby bass" for higher Qts woofers like the Alpha can be entirely explained away by this peak around 100 Hz in an OB. Note that despite my critisism of the Alpha 15A they still sound very good and I have no plans to replace them (the price/performance ratio is great). If price was no object I'd look to getting the AE Dipole15 instead.
After modelling the setup with MJK's worksheets (and adding the reflections from a side wall, rear wall and floor) and then listening to my built speakers, I beginning to think that Nelson is right. The approach using lower Qts woofers and adding bass boost may be better (by that I mean provide a flatter freq response). The Alphas in my OB end up with a response peak centered around 100 Hz and drop off rapidly below 45 Hz. Using a lower Qts woofer should provide much flatter response around 100 Hz and the bass boast will bring the response up for lower freqs. (But this will only work if you use an active crossover).
I think that some complaints about "slow bass" or "tubby bass" for higher Qts woofers like the Alpha can be entirely explained away by this peak around 100 Hz in an OB. Note that despite my critisism of the Alpha 15A they still sound very good and I have no plans to replace them (the price/performance ratio is great). If price was no object I'd look to getting the AE Dipole15 instead.
Now that is confirmation that the powered Augies could be a better solution. A plate amp with "bass boost" or some form of gain control may just be a simpler option that going active XO. And I suppose the upside is lower bass extension.
I kind of wonder if replacing my idea of double Alphas with double Betas (Nelson's recommendation) will remove the 100Hz bump and at the same time offer simpler amplification?
Hi Andre, in my limited experience, the first "dipole hump" is a characteristic of the baffle itself. But also, a couple thoughts from a newbie:
1. Nelson's OB's look about 4 feet wide to me. Part of Martin's rationale for high Qts is to get the baffle width down.
2. Are you assuming that the driver's response is flat? Check out page 7 of Martin's "Designing a Passive Two Way Open Baffle Speaker System", specifically Fig. 6. The final response is the sum of driver's response, baffle hump, whatever low-pass is in place etc.
http://www.quarter-wave.com/OBs/OB_Design.pdf
Also: Project 7 : Lowther Open Baffle System Design Project
Andre, where are you based? If you are in the UK or somewhere else in Europe, have you considered buying an old pair of folded-horn lowther cabinets and installing the PM6As into them? A lot of people don't like the sound of this set-up and you will certainly not get pounding bass out of it, but you may like it.
Signal path is obviously as simple as it can get as you don't even need to add a cross-over network. Main advantage is that Lowther cabinets (particularly acoustas) are cheap as chips in the UK, as loads were made and sold here over the last 50-60 years and the majority of sellers cannot be bothered with the hassle of posting them. All you have to do is arrange for a courier to pick them up or drive and pick them up yourself - all of which should cost less than a pair of woofers, materials for OB, x-overs/EQs and second amp (if you end up having to bi-amp).
Similarly, because very few people are prepared to post them, if you decide you don't like them, you are very likely to recuperate what you spent in purchase and transportation, by offering a shipping option (and therefore opening yourself to a larger market).
If you are interested in this, let me know and I'll give you some tips on choosing between cabinets - as they were being made for a long time, there are a few variations.
My baffle width is 3 feet. I recall that Martin's original project
had wings that gave it a comparable surface area. In any case
I tried both and liked the beta. Here's a comparative curve.
😎
Attachments
Hi Nelson, my apologies. Thank you for the graph - that is very informative.
So you're using the Beta on 36", and he's using the Alpha on a 20" baffle (his second-gen design).
It looks like they both get to 40hz around 4-5db down (comparing your graph with his Fig. 13 in "Designing a Passive Two-Way OB").
So you're using the Beta on 36", and he's using the Alpha on a 20" baffle (his second-gen design).
It looks like they both get to 40hz around 4-5db down (comparing your graph with his Fig. 13 in "Designing a Passive Two-Way OB").
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