Re: Re: My 2 cents
Yes, they are not the "C" version. They must not be that different. The floor stander plan on the Hemp Acoustics web site is not that different from what I did. They went taller and narrower than my design. Mine ended up 40 inches tall, 16 inches wide and 12 inches deep. The front panel is doubled. I used the Boxy CAD spread sheet to come up with the design.
planet10 said:
Yes, they are not the "C" version. They must not be that different. The floor stander plan on the Hemp Acoustics web site is not that different from what I did. They went taller and narrower than my design. Mine ended up 40 inches tall, 16 inches wide and 12 inches deep. The front panel is doubled. I used the Boxy CAD spread sheet to come up with the design.
'Must not...' don't bet on it. 
Odd things happen.
All of this seems to confirm GM's suspicion that these new units in particular need their response from about 1.5KHz or so shelving with some form of Eq, be it active or a RLC circuit, plus a zobel, if they're going to sound balanced in a back-loaded cabinet.
Odd things happen.All of this seems to confirm GM's suspicion that these new units in particular need their response from about 1.5KHz or so shelving with some form of Eq, be it active or a RLC circuit, plus a zobel, if they're going to sound balanced in a back-loaded cabinet.
Re: Re: FR8C parametres measured by me.
Greets!
You need to calc the zobel based on the inductance at the XO point, which for a FR is ~20 kHz, so measure its impedance (Zxo) at 20 kHz (Fxo), then calc its inductance:
Le (mH) = ((Zxo^2 - Re^2)^0.5/(2*pi*Fxo))*1000
Hopefully this will allow you to use a simple R/C shelving network.
GM
panomaniac said:
Greets!
You need to calc the zobel based on the inductance at the XO point, which for a FR is ~20 kHz, so measure its impedance (Zxo) at 20 kHz (Fxo), then calc its inductance:
Le (mH) = ((Zxo^2 - Re^2)^0.5/(2*pi*Fxo))*1000
Hopefully this will allow you to use a simple R/C shelving network.
GM
OK guys,
I've been looking at a ML-TQWT for the Hemp FR8c.
There is one over in the Aperto thread. that's a straight box.
So I have a few questions:
Using Martin's ML-TQWT model, the FR8c models pretty well with a line length of ~60 to 70". Can this be folded?
MJK's model is for mass loaded straight pipe, but does it matter if it's folded?
The ML-TQWT design around the 'net seem to all be straight pipes. Why?
So it's really 2 questions.
If so, it looks (on paper) like the FR8c could work well in a box no taller than 35", which would be great. Any ideas?
I've been looking at a ML-TQWT for the Hemp FR8c.
There is one over in the Aperto thread. that's a straight box.
So I have a few questions:
Using Martin's ML-TQWT model, the FR8c models pretty well with a line length of ~60 to 70". Can this be folded?
MJK's model is for mass loaded straight pipe, but does it matter if it's folded?
The ML-TQWT design around the 'net seem to all be straight pipes. Why?
So it's really 2 questions.
- Can the ML-TQWT be folded?
- Can the mass loading and round port be used with the folded line?
If so, it looks (on paper) like the FR8c could work well in a box no taller than 35", which would be great. Any ideas?
An MLTL is a straight, untapered pipe with mass-loading. An ML TQWT is a pipe that tapers toward the throat, with mass-loading. The latter is sometimes useful as it gives some extra gain, but it needs to be longer than a stright pipe for the same Fp (pipe tuning). In most cases, a stright pipe gives as good, or better, results, but the TQWT is still a useful card to play for those units that don't suit a straight line as well, or if you have a particular goal in mind.
A tapered pipe can indeed be folded if an unfolded line isn't possible in your room, and yes, you can still apply the mass-loading.
A tapered pipe can indeed be folded if an unfolded line isn't possible in your room, and yes, you can still apply the mass-loading.
Thank you, Mr. Moose!
I should be careful in my use of "straight pipe." I meant "not folded" as opposed to "straight walls. " Will use "folded" or "not folded" from now on. Even a straight TL could be folded, I've seen it done.
So... Using Martin's ML-TQWT calculations, no worries about folding it. And use the same stuffing and port, right?
The folded pipe would have much less leeway in port placement, unless the port was at the back or side.
I have, and it's a little bigger than I'd like. What got me thinking is that a smaller box models just as well, so where's the catch?
I should be careful in my use of "straight pipe." I meant "not folded" as opposed to "straight walls. " Will use "folded" or "not folded" from now on. Even a straight TL could be folded, I've seen it done.
So... Using Martin's ML-TQWT calculations, no worries about folding it. And use the same stuffing and port, right?
The folded pipe would have much less leeway in port placement, unless the port was at the back or side.
I have, and it's a little bigger than I'd like. What got me thinking is that a smaller box models just as well, so where's the catch?
Right -damping and vent remain the same.
Why use a larger cabinet? Better sonics. Even if the FR looks similar, bigger is better; it will sound less strained, and have better dynamics than the smaller volume enclosure -something GM taught me, and he's not kidding. The more air you've got working for you, the bigger, the more effortless and dynamic the sound will be.
Look at it this way: I could get 350bhp out of a 2 litre tubocharged Cosworth engine, no sweat. Would it be as effortless as a 389 V8 with the 3x2 carb option in a MK1 Pontiac GTO (one day, I shall own one), rated at ~the same power? Nope. As a Brit, I'm not supposed to voice such a classic U.S. phrase, but it's fundamentally true: there's no substitute for cubic capacity.
Why use a larger cabinet? Better sonics. Even if the FR looks similar, bigger is better; it will sound less strained, and have better dynamics than the smaller volume enclosure -something GM taught me, and he's not kidding. The more air you've got working for you, the bigger, the more effortless and dynamic the sound will be.
Look at it this way: I could get 350bhp out of a 2 litre tubocharged Cosworth engine, no sweat. Would it be as effortless as a 389 V8 with the 3x2 carb option in a MK1 Pontiac GTO (one day, I shall own one), rated at ~the same power? Nope. As a Brit, I'm not supposed to voice such a classic U.S. phrase, but it's fundamentally true: there's no substitute for cubic capacity.
Scottmoose said:
Yes, don't I know it. That's why I love the big Altec boxes and the Onken W. It's always a matter of compromise. Given the room, I'd go big. But my little cottage just doesn't have the room for big boxes. So cheat, I will. Or at least try.
My neighbors had a giant plywood crate delivered, it's still in their yard. Biggest damn plywood box I've ever seen. 8ftx4ftx15ft. HxWxL. That's a 480 cubic foot box. Maybe I can make speakers out of it, and set it right outside my living room windows.
Re: Jimmy D ...
I would not have believed it, but I tried it tonight. It works!
OK, the details:
Whipped up a pair of the Warfdale/JELabs style baffles out of double thickness cardboard. Did it at work where there is plenty of room - maybe too much room.
The amount of low mid the baffle adds is surprising. And they will play loud! Imaging was decent, but not extraordinary. No real low bass, of course, but good solid mid bass. A lot of the shout was gone.
Tonal balance was still mid heavy, but better than I had hear it before on small baffles. What really helped was the loudness button on my Sansui receiver. Pulling down the mids was a big help.
Some caveats:
Huge room. The baffles where at least 15' from the nearest wall. Room is huge. 40x50x22 LxWxH. I've been in smaller barns. That can't help room gain.
Cardboard baffle. Sounds like... yeah, cardboard. I think that was the main annoyance. And the cardboard must pass LF like a sieve. Can't help the tonal balance.
So I can see how this driver on a real baffle in a modest size room could sound very good. Better yet would be a 15" or 2x12" drivers for bass with the FR8c for highs and mids. Should be worth a try.
Can anyone who has gone from a cardboard baffle to a wooden baffle tell me what differences you found?
Nanook said:
I would not have believed it, but I tried it tonight. It works!
OK, the details:
Whipped up a pair of the Warfdale/JELabs style baffles out of double thickness cardboard. Did it at work where there is plenty of room - maybe too much room.
The amount of low mid the baffle adds is surprising. And they will play loud! Imaging was decent, but not extraordinary. No real low bass, of course, but good solid mid bass. A lot of the shout was gone.
Tonal balance was still mid heavy, but better than I had hear it before on small baffles. What really helped was the loudness button on my Sansui receiver. Pulling down the mids was a big help.
Some caveats:
Huge room. The baffles where at least 15' from the nearest wall. Room is huge. 40x50x22 LxWxH. I've been in smaller barns.
That can't help room gain.Cardboard baffle. Sounds like... yeah, cardboard. I think that was the main annoyance. And the cardboard must pass LF like a sieve. Can't help the tonal balance.
So I can see how this driver on a real baffle in a modest size room could sound very good. Better yet would be a 15" or 2x12" drivers for bass with the FR8c for highs and mids. Should be worth a try.
Can anyone who has gone from a cardboard baffle to a wooden baffle tell me what differences you found?
Part Deux.
Tried them at home before taking them apart. Much too big for my small and crowded living room, but they work much better in the small room.
Bass is better, even though I don't have tons of room gain (open windows and doors). Imaging is also much better with closer walls. In fact imaging is quite good. A little low, but the drivers are almost on the floor. Images seems about 5 feet high. Rear firing tweeter now has some use with wall reflections
They get darn loud with little power! Still a bit shouty, but that's probably the cardboard baffles. If a passive contour filter were needed, there seems to be plenty of sensitivity to trade off.
If you have the room, this baffle with big bass drivers and the FR8 as a mid/high should be killer! Just the FR8 by itself really rocks.
Tried them at home before taking them apart. Much too big for my small and crowded living room, but they work much better in the small room.
Bass is better, even though I don't have tons of room gain (open windows and doors). Imaging is also much better with closer walls. In fact imaging is quite good. A little low, but the drivers are almost on the floor. Images seems about 5 feet high. Rear firing tweeter now has some use with wall reflections
They get darn loud with little power! Still a bit shouty, but that's probably the cardboard baffles. If a passive contour filter were needed, there seems to be plenty of sensitivity to trade off.
If you have the room, this baffle with big bass drivers and the FR8 as a mid/high should be killer! Just the FR8 by itself really rocks.
Here's Vadim's BLH "Horn Project" using the FR8C. A kit is available from E-Speakers and a complete write-up is given at this URL:
http://www.e-speakers.com/Pdf/vadim-infopack.pdf
If someone is going to plug in the values (they can be approximated from the drawings -- they aren't specifically given) it would be interesting to see how it performs on Martin's BLH Mathcad worksheets.
http://www.e-speakers.com/Pdf/vadim-infopack.pdf
If someone is going to plug in the values (they can be approximated from the drawings -- they aren't specifically given) it would be interesting to see how it performs on Martin's BLH Mathcad worksheets.
jackinnj said:
This design was originally offered for the FR810DIY, the predecessor of the current FR8C. The driver parameters in the write-up are for the earlier driver. The newer driver has a larger Vas and lower mms - I don't know how much that will affect the performance of the system.
Bill
The world according to Martin (MJK):
"While in general higher Qtd drivers are not looked upon as being particularly high fidelity, the use of a higher Qtd driver in a severely compromised back loaded horn may have some real benefits".
You can see the entire article on MJK's website:
http://www.quarter-wave.com/Horns/Back_Horn.pdf
"While in general higher Qtd drivers are not looked upon as being particularly high fidelity, the use of a higher Qtd driver in a severely compromised back loaded horn may have some real benefits".
You can see the entire article on MJK's website:
http://www.quarter-wave.com/Horns/Back_Horn.pdf
Re: Re: Jimmy D ...
I got more info and decided to try these drivers. Will get them in a few days and plan to try them over the weekend.
I plan exactly to add 2x 12" woofers on each speaker, and to cut at approx 200hz (hopefully less but i dont think so).
My baffles will be very narrow (room requirements) but tall, using the floor above the driver to reinforce midbass like a wider baffle would do.
Approx measures are 30x120cm.
I will experiment with pressed cardboard (which I can find here in office shop), easy to cut with a cutter. After 2 weeks of burn-in, I'll change the baffle size and see the effect.
The definitive baffles will be 36mm birch plywood (2x18mm sandwitched), with some finishing (shellac, maybe c37).
I'll make a thread in the next few days, but wanted to reply to Panno that i'll confront pressed cardboard with thick plywood.
panomaniac said:
I got more info and decided to try these drivers. Will get them in a few days and plan to try them over the weekend.
I plan exactly to add 2x 12" woofers on each speaker, and to cut at approx 200hz (hopefully less but i dont think so).
My baffles will be very narrow (room requirements) but tall, using the floor above the driver to reinforce midbass like a wider baffle would do.
Approx measures are 30x120cm.
I will experiment with pressed cardboard (which I can find here in office shop), easy to cut with a cutter. After 2 weeks of burn-in, I'll change the baffle size and see the effect.
The definitive baffles will be 36mm birch plywood (2x18mm sandwitched), with some finishing (shellac, maybe c37).
I'll make a thread in the next few days, but wanted to reply to Panno that i'll confront pressed cardboard with thick plywood.
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