Hello, my name is gearfreak and I am an AUB refugee...
...I have an interest, I'll bite! So how big were they?
I am working my way towards 30cuft.
BIB right?
...or do we get into areas of difficulty beyond driver Vas?
Sealed or MLTL / convertible is the initial trajectory, but that is just me prior to soliciting suggestions.
Real (driver) measurements to come, but only after I figure out whereabouts to start a thread on all these 515's sitting here.
...I have an interest, I'll bite! So how big were they?
I am working my way towards 30cuft.
BIB right?
...or do we get into areas of difficulty beyond driver Vas?
Sealed or MLTL / convertible is the initial trajectory, but that is just me prior to soliciting suggestions.
Real (driver) measurements to come, but only after I figure out whereabouts to start a thread on all these 515's sitting here.
Greets!
Start your own 604D build thread and load it with all the AUB/whatever info as I haven't been able to get on since my last post re 'attached is the File type/size list'.
Re cab size considerations, see my response here: Best MLTL Cabs (or other if better) for the latest Altec 604's
GM
Start your own 604D build thread and load it with all the AUB/whatever info as I haven't been able to get on since my last post re 'attached is the File type/size list'.
Re cab size considerations, see my response here: Best MLTL Cabs (or other if better) for the latest Altec 604's
GM
They are very coloured .That does not mean they are not good.It just means you have to be able to live with that sort of sound.Most high efficiency speakers are coloured though so if you want realistic dynamics this is often the price you pay.
It is arguable however that given the vast improvement in high efficiency cone drivers [they now measure flat]-just look at the Faital Pro drivers, then the two way using a compression loaded horn for the mid and treble region is probably obsolete.And I say that as a big fan of classic Tannoys.
Take a look at the Troels Gravesen -The Loudspeaker for example.
It is arguable however that given the vast improvement in high efficiency cone drivers [they now measure flat]-just look at the Faital Pro drivers, then the two way using a compression loaded horn for the mid and treble region is probably obsolete.And I say that as a big fan of classic Tannoys.
Take a look at the Troels Gravesen -The Loudspeaker for example.
Actually, 604 can be much more "transparent" than modern speakers today.
Altec 604 (or Urei) used to be ubiquitous in the music studios worldwide in 60's through 80's. So what you hear from 604 today is close to what the musicians and producers were hearing in the studio at that time. Beatles, Glenn Gould, Earth Wind and Fire..., all of them were listening to 604 type in the studios. If you consider "transparency" is hearing musician's intention accurately, and if you want to to hear music in that way, 604 would be probably the best choice to listen to the music from that era. Today's flat response speakers were not flat at all at that time in this sense, because 604 were the reference speakers.
Altec 604 (or Urei) used to be ubiquitous in the music studios worldwide in 60's through 80's. So what you hear from 604 today is close to what the musicians and producers were hearing in the studio at that time. Beatles, Glenn Gould, Earth Wind and Fire..., all of them were listening to 604 type in the studios. If you consider "transparency" is hearing musician's intention accurately, and if you want to to hear music in that way, 604 would be probably the best choice to listen to the music from that era. Today's flat response speakers were not flat at all at that time in this sense, because 604 were the reference speakers.
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The 604s were an integral part of the "Alberts sound" in Australia.That shredding the air and percussive guitar sound epitomised by AC/DC but also by many other great Australian bands including the Easybeats,Stevie Wright ,Rose Tattoo and The Angels.All mastered on 604s in the Alberts Studio 1 in Sydney.
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Not sure that I remember - but would guess in the 25 cubic foot range. I have photos somewhere, but didn't save dimensions.
The 604:s are bass shy and do need huge boxes if one wants low bass. With the help of a neighbour I just hauled up 3 pcs 604-8K from the hometheater in the basement. Used them as LCR, crossed over to 4 x 18” subs from Acoustic Elegance. Now the 604:s will be ”retired” to the living room as TV-speakers, some occasional Netflix but probably not much of music.
As I had the subs already, I didn’t have to build large boxes so I built the 604:s as sealed ones, fully stuffed, net volume 101 L / 3,58 ft³ each prior to stuffing. I cannot use any subs in the living room, so now I’m scratching my head what would be lowest tuning frequency with still good sound when I rebuild them to ported ones, to get some more bass out of them.
There will be 3 ports, each will have internal id 72 mm / 2,84”, length can be up to about 25 cm / 10” or so due to practical reasons inside the box. Stuffing will be pulled out and only about 5 cm / 2” on each wall left. With that stuffing left I guess the virtual volume will be about 107 L and after reduction of the ports of about 1 L each, net virtual volume should be around 104 L / 3,64 ft³.Ports will be on the backside with about 15-20 cm / 6-8” breathing distance to the wall behind to get some more room gain.
Anyone who has experience from such small ported enclosures with the 604:s and have a suggestion what to aim for as tuning frequncy? Lowest possible is not really the aim but lowest possible that still sounds nice.
(I apologize for this slight kidnap of the thread.)
As I had the subs already, I didn’t have to build large boxes so I built the 604:s as sealed ones, fully stuffed, net volume 101 L / 3,58 ft³ each prior to stuffing. I cannot use any subs in the living room, so now I’m scratching my head what would be lowest tuning frequency with still good sound when I rebuild them to ported ones, to get some more bass out of them.
There will be 3 ports, each will have internal id 72 mm / 2,84”, length can be up to about 25 cm / 10” or so due to practical reasons inside the box. Stuffing will be pulled out and only about 5 cm / 2” on each wall left. With that stuffing left I guess the virtual volume will be about 107 L and after reduction of the ports of about 1 L each, net virtual volume should be around 104 L / 3,64 ft³.Ports will be on the backside with about 15-20 cm / 6-8” breathing distance to the wall behind to get some more room gain.
Anyone who has experience from such small ported enclosures with the 604:s and have a suggestion what to aim for as tuning frequncy? Lowest possible is not really the aim but lowest possible that still sounds nice.
(I apologize for this slight kidnap of the thread.)
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With such a small cab and assuming SS/highly damped source, tuning to < Fs + room gain is all you can do, though Freddy/someone with experience with it will probably suggest including 'assisted' 6th order to further 'bump' it a bit.
Regardless, vent wise, only two of these are required to keep vent mach < ~5%, making them as long practical is your best overall tuning option.
GM
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Thanks for answers. The existing cabinets are well built and quite OK looking in oak. So I wish to keep them as they are, except for some ports on the back. The width I can play with in the living room is only about 270 cm / 106” with a sidewall to the left and a piano to the right which cannot be moved due to a window. With centre speaker under the TV I have 34 cm / 13” on each side of the centre speaker towards L and R. That may be sufficient for a 8” sub, - not much of a sub …
GM, English is not my native language so to avoid possible misunderstandings, when you wrote ”to keep vent mach < ~5%”, can you expand a bit? 5% of speed of sound, distorsion or what? With max length about 25 cm / 10” and 3 ports, I believe tuning would land at around 35 Hz. (I don’t have access to simulation in Unibox on this computer.) And there is my question actually. Sound quality wise for the bass, is it better to aim for about 35 Hz or might it be better with a bit higher tuning of say 40 Hz? I prefer well sounding bass instead of lowest possible but ”muddy and slow”.
(I chose id 72 mm for a couple of reason:
1) Several smaller diameter ports instead of 1 large of, say 100 mm / 4”, allow for higher velocities through the port before Reynolds number goes up too much and audible turbulence / distorsion is reached.
2) id 72 mm can be fitted with a flange + roundover of Ø 120 mm / ~ 4,7” inside the cabinet which should lessen turbulence at port ends. With a larger port, flanges inside wouldn’t be possible due to practical reasons.
3) The id 72 mm ports can be easily closed off if wanted, with easy to buy covers.
The picture shows the cabinets in the hometheater with newly installed subs before the room was rebuilt to accomodate the new speakers. L and R are close to 2 feet wide, the centre 3 feet and has been moved into the room out of it usual place. The 2nd: Picture round ports as a black curve and slottet port of equivalent area as a red curve with ratio length versus height of 12,6. Y-axis is air velocity in port when Reynolds number 50 000 is reached. X-axis the diameter of the port in mm. (50 000 is subjectively before turbulence starts to get bad audibly. Actual figure for Reynolds number when turbulence starts to form is around 3 200.))
The existing cabinets are well built and quite OK looking in oak. So I wish to keep them as they are, except for some ports on the back. The width I can play with in the living room is only about 270 cm / 106” with a sidewall to the left and a piano to the right which cannot be moved due to a window. With centre speaker under the TV I have 34 cm / 13” on each side of the centre speaker towards L and R. That may be sufficient for a 8” sub, - not much of a sub … GM, English is not my native language so to avoid possible misunderstandings, when you wrote ”to keep vent mach < ~5%”, can you expand a bit? 5% of speed of sound, distorsion or what? With max length about 25 cm / 10” and 3 ports, I believe tuning would land at around 35 Hz. (I don’t have access to simulation in Unibox on this computer.) And there is my question actually. Sound quality wise for the bass, is it better to aim for about 35 Hz or might it be better with a bit higher tuning of say 40 Hz? I prefer well sounding bass instead of lowest possible but ”muddy and slow”.
(I chose id 72 mm for a couple of reason:
1) Several smaller diameter ports instead of 1 large of, say 100 mm / 4”, allow for higher velocities through the port before Reynolds number goes up too much and audible turbulence / distorsion is reached.
2) id 72 mm can be fitted with a flange + roundover of Ø 120 mm / ~ 4,7” inside the cabinet which should lessen turbulence at port ends. With a larger port, flanges inside wouldn’t be possible due to practical reasons.
3) The id 72 mm ports can be easily closed off if wanted, with easy to buy covers.
The picture shows the cabinets in the hometheater with newly installed subs before the room was rebuilt to accomodate the new speakers. L and R are close to 2 feet wide, the centre 3 feet and has been moved into the room out of it usual place. The 2nd: Picture round ports as a black curve and slottet port of equivalent area as a red curve with ratio length versus height of 12,6. Y-axis is air velocity in port when Reynolds number 50 000 is reached. X-axis the diameter of the port in mm. (50 000 is subjectively before turbulence starts to get bad audibly. Actual figure for Reynolds number when turbulence starts to form is around 3 200.))
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Nice room/system!
OK, understood, just the math 'says' you only need two vents and due to the acoustically small size allotted for the 604, it ideally needs to be tuned as low as practical [longest vent length], though of course you can try shorter ones in case your room has more gain than typical, i.e. you don't have to rigidly flush mount the vents to test, just slide them in part way and use Blu-Tack or similar to temporarily seal the joint.
Don't know why your Reynolds chart is so far off from what works in practice unless it's a pipe terminating into free space.
Regardless, when the vent is driven too hard by the cab's air mass 'spring' it loads up, making increasingly audible noise [distortion] with ~5% mach [speed of sound] = 344 m/s*0.05 = ~17 m/sec the goal for some folks, though Richard Small mentioned his point was ~4% IIRC and most apparently are OK with up to 10% judging by reverse engineering some popular consumer designs over the decades.
Note though that if it has grill cloth, etc, a certain amount of vent damping comes into play, so can be 'critically' damped if desired by packing the vent with straws or tightly stretching material over it to personal 'taste', though folks often remove them or unplug a damped vent for serious listening, reinforcing the sometimes quoted 10% rule.
FWIW, Hornresp, a well vetted software, predicts ~26 Hz for 104 L with one large vent/25 cm long, so will be a little higher for two 72 mm i.d. ones of the same total cross sectional area [CSA] due to increased stiction.
Room gain below a vented cab's tuning is like adding a 'sub' system, but with little/no driver protection, so in general, best to tune down into where the room can add some gain + some driver protection above its Fs. Note too that the lower the tuning, the 'tighter'/'faster' the perceived bass response similar to a low Qt sealed alignment and one reason why extended bass shelf [EBS] alignments have been popular for woofer apps since the digital age of electronics became the norm.
Higher tuning gets you more mid bass 'punch', etc., [AKA Altec's, JBL's toe tapping 'west coast sound']. Great if there's no significant lower bass 'demands' below 35-40 Hz, but if there is you'll need to protect the speakers below ~0.7x tuning.
'Fullness'/'mud'/'slow' is actually in the ~250-500 Hz portion of the critical telephone BW where vintage driver designs excel, so the 604's cab alignment, XO point/slope are the 'key' issues to 'fast'/tight' [mid] bass transients.
1] Single vents are more efficient, hence has the shortest length for a given tuning, so not following your logic other than a single 100 mm diameter is a little smaller than dual 72 mm, but at 25 cm long it still tunes the cab the same ~26 Hz and still below the 17 m/s [5%] vent mach, so doesn't need any other flanges than the one it makes mounted to the cab, so recommend the single 100 mm vent.
As Forest Gump noted "Simple is as simple does". ;)
GM
Nice room/system!
OK, understood, just the math 'says' you only need two vents and due to the acoustically small size allotted for the 604, it ideally needs to be tuned as low as practical [longest vent length], though of course you can try shorter ones in case your room has more gain than typical, i.e. you don't have to rigidly flush mount the vents to test, just slide them in part way and use Blu-Tack or similar to temporarily seal the joint.
Don't know why your Reynolds chart is so far off from what works in practice unless it's a pipe terminating into free space.
Regardless, when the vent is driven too hard by the cab's air mass 'spring' it loads up, making increasingly audible noise [distortion] with ~5% mach [speed of sound] = 344 m/s*0.05 = ~17 m/sec the goal for some folks, though Richard Small mentioned his point was ~4% IIRC and most apparently are OK with up to 10% judging by reverse engineering some popular consumer designs over the decades.
Note though that if it has grill cloth, etc, a certain amount of vent damping comes into play, so can be 'critically' damped if desired by packing the vent with straws or tightly stretching material over it to personal 'taste', though folks often remove them or unplug a damped vent for serious listening, reinforcing the sometimes quoted 10% rule.
FWIW, Hornresp, a well vetted software, predicts ~26 Hz for 104 L with one large vent/25 cm long, so will be a little higher for two 72 mm i.d. ones of the same total cross sectional area [CSA] due to increased stiction.
Room gain below a vented cab's tuning is like adding a 'sub' system, but with little/no driver protection, so in general, best to tune down into where the room can add some gain + some driver protection above its Fs. Note too that the lower the tuning, the 'tighter'/'faster' the perceived bass response similar to a low Qt sealed alignment and one reason why extended bass shelf [EBS] alignments have been popular for woofer apps since the digital age of electronics became the norm.
Higher tuning gets you more mid bass 'punch', etc., [AKA Altec's, JBL's toe tapping 'west coast sound']. Great if there's no significant lower bass 'demands' below 35-40 Hz, but if there is you'll need to protect the speakers below ~0.7x tuning.
'Fullness'/'mud'/'slow' is actually in the ~250-500 Hz portion of the critical telephone BW where vintage driver designs excel, so the 604's cab alignment, XO point/slope are the 'key' issues to 'fast'/tight' [mid] bass transients.
1] Single vents are more efficient, hence has the shortest length for a given tuning, so not following your logic other than a single 100 mm diameter is a little smaller than dual 72 mm, but at 25 cm long it still tunes the cab the same ~26 Hz and still below the 17 m/s [5%] vent mach, so doesn't need any other flanges than the one it makes mounted to the cab, so recommend the single 100 mm vent.
As Forest Gump noted "Simple is as simple does". ;)
GM
Thanks for your insights GM. Especially for that section about frequency range for subjective ”muddy bass range”. I like the ”tight bass” one gets from sealed boxes and have also noticed that the lower the tuning for the ports, frequency curves for ported and sealed get more and more alike while at the same time you lose some dBs in the upper bass for a ported cabinet. (As it is with crossover, I still use Altec’s original crossover which came with the drivers.)
I don’t agree though with one single large port being more efficient compared to several smaller ones having together the same cross section area as the large one. I see it as the other way around. Intuition says a large port is better than a small one. I have no problems with that but a looong time ago I had some classes for planning of chemical plants where air, steam and fluid flow through pipes was on the schedule.. A faint memory said that smaller diameter pipes can carry a higher velocity in them than larger ones before turbulence starts. So, in that case several smaller ports should for pumping out air into the room perform better before turbulence and compression starts with audible noise from the ports. I googled some and found the chart below. Anywhere one looks, all lecture books says that turbulence starts at around 2400-3200 and the ”unit” for it is Reynolds number. Subjectively for turbulence and start of compression in speaker ports some say 30 000 others say 50 000.
Subjectivity set aside, from the chart: With a 4” pipe one can have a velocity of 600 ft/min before turbulence starts to form. For the 8” pipe the velocity is ”only” 300 ft/min. 4 pcs 4” pipes have the same cross section area as 1 pcs 8” pipe. For me that means double the amount of pumped air and higher SPL from the system before compression starts to form. Those dBs / SPL are ”for free” except that 4 smaller ports may cost a bit more than 1 large one.
(This is academic though, I will not play at very loud volumes watching TV …)
I don’t agree though with one single large port being more efficient compared to several smaller ones having together the same cross section area as the large one. I see it as the other way around. Intuition says a large port is better than a small one. I have no problems with that but a looong time ago I had some classes for planning of chemical plants where air, steam and fluid flow through pipes was on the schedule.. A faint memory said that smaller diameter pipes can carry a higher velocity in them than larger ones before turbulence starts. So, in that case several smaller ports should for pumping out air into the room perform better before turbulence and compression starts with audible noise from the ports. I googled some and found the chart below. Anywhere one looks, all lecture books says that turbulence starts at around 2400-3200 and the ”unit” for it is Reynolds number. Subjectively for turbulence and start of compression in speaker ports some say 30 000 others say 50 000.
Subjectivity set aside, from the chart: With a 4” pipe one can have a velocity of 600 ft/min before turbulence starts to form. For the 8” pipe the velocity is ”only” 300 ft/min. 4 pcs 4” pipes have the same cross section area as 1 pcs 8” pipe. For me that means double the amount of pumped air and higher SPL from the system before compression starts to form. Those dBs / SPL are ”for free” except that 4 smaller ports may cost a bit more than 1 large one.
(This is academic though, I will not play at very loud volumes watching TV …)
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You're welcome!
True, but for a given audio tuning they must be longer to slow it down, so to speak, which is considered less efficient acoustically. Now in a steam pipe/whatever app where it's a fixed length, then yes, more smaller ones may be required to get the desired net volume, flow rate, efficiency, etc..
Well, not necessarily as longer pipes have lower harmonic structures that while having a low vent mach can also have these out of phase resonances audibly comb filtering with the mains' output. The Onken alignment is an excellent example and for those folks that prefer them it's due to their liking the [euphonic] distortion of all the 'ripple' the vents create in the [lower] mids.
Regardless, it's your speakers, so by all means use whichever you prefer that gets the job done, but since I'm posting to a multitude I feel I should provide the most technically correct response as I understand it.
GM
FYI, a MI chart based on the Klark Teknik Altec gave me way back when: https://www.audio-issues.com/wp-content/uploads/2011/07/main_chart.jpg
GM
GM
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