Budget mid-woofers to go with a line-array ribbon

[DeonC]

Hi guys

I am now the proud owner of these line-array ribbons. They were handmade by a local speaker builder. They are 35" long and are rated at 90dB/W at 6-ohm.

An externally hosted image should be here but it was not working when we last tested it.

The designer reckons they can work down to 350Hz with a 3rd order XO. I would prefer not to take them that low. To start off with they will be used with an active 4th order at 400Hz (XO to a 15" woofer on an OB), but my aim is to get a set of good midwoofers that can handle the range between 700Hz and 80Hz (also OB). I will then be using the 15" woofer from 80Hz to 40Hz, before crossing to a good sub for the lowest octaves.

Here is where I need help. I need suggestions for good mid-woofers that wont break the bank, but I do not want to sacrifice the transparency of the ribbon. I have a set of four Philips AD5060/W8 and was thinking of sourcing four more. Four of these per side in a line-array next to the ribbon is one idea. My other idea is eight (four per side) of the Markaudio CHN-70 Paper Cone 4" Full Range. They are reasonably priced and could be the answer. An array of Markaudio CHP-70-P Gen2 Natural Paper or Markaudio CHR-70-Gold Champagne Cone 4" Full Range could also possibly work, but then it will be at the upmost end (even over) my available budget, especially after transport, C&E, etc. to South-Africa is included.

So my question is: will the Philips work, or must I look toward more modern drivers? And if so, which should I consider?

Thanks in advance for the help.

Enjoy,
Deon

 

[DeonC]

After surfing the PartsExpress website I found these too:

Dayton Audio CF120-4 4-1/2" Woven Carbon Fiber Midwoofer 4 Ohms

They look very good. There are also some 3.5" buyout woofers that are a possibilty, but so far these CF midwoofs and the MarkAudio midwoofs are the best options I have found. Any other suggestions?

Thanks,
Deon

 

[DAMIC]

Hi,

Maybe this could help:

http://www.diyaudio.com/forums/plan...titute-woofer-panel-ideas-suggestions-18.html

 

[DeonC]

Hi Damic

I have read through that thread. It was interesting, thanks. The difference however is that they are aiming at fullrange, XO down to bass, and I just want to do lower mids. I am going to use a single 15" P.Audio woofer per side for bass. OTOH, I am open to be convinced. But I think I will get better midrange purity with dedicated mids. Ajy thoughts?

Thanos,
Deon

 

[fporegon]

4" woofers

Why restrict yourself to such small woofers when you only need to go up to 700 Hz? Is your tweeter a dipole as well? How will you handle corossover and EQ?

 

[Bob Richards]

I'd build vertical line array woofers, maybe about equal height, with four 8 inch Peerless Nomex cone woofers (about $80 each - $60 each for the 6.5 inch versions) on each side, closed box, with active EQ making them acoustically flat down to 30HZ. I'd cross them with an active 4 pole xover anywhere between 500HZ - 800HZ. I'd also put the ribbons up off the floor by maybe 2 feet.

I have the 6.5 inch Peerless Nomex woofers with a 10dB 32HZ FR peak active EQ (quick rolloff below 30HZ and does nothing above 100HZ), and really like them. Woofer size depends how loud you want them to go. A vertical line array of woofers will work better with typical room acoustics issues (floor and ceiling bounce and associated comb filter effects).

 

[DeonC]

Why restrict yourself to such small woofers when you only need to go up to 700 Hz?

I need something that will keep up with the speed of the ribbon. I may be wrong in this. OTOH, the thing that makes the Dayton CF120 my frontrunner is its low Q.

Is your tweeter a dipole as well? How will you handle corossover and EQ?

The ribbon is dipole as well, and all XOs and EQ will be done with a full active XO.

 

[DeonC]

I'd build vertical line array woofers, maybe about equal height, with four 8 inch Peerless Nomex cone woofers (about $80 each - $60 each for the 6.5 inch versions) on each side, closed box, with active EQ making them acoustically flat down to 30HZ. I'd cross them with an active 4 pole xover anywhere between 500HZ - 800HZ. I'd also put the ribbons up off the floor by maybe 2 feet.

I have the 6.5 inch Peerless Nomex woofers with a 10dB 32HZ FR peak active EQ (quick rolloff below 30HZ and does nothing above 100HZ), and really like them. Woofer size depends how loud you want them to go. A vertical line array of woofers will work better with typical room acoustics issues (floor and ceiling bounce and associated comb filter effects).

Hi Bob

Thanks for the suggestion. I wil look into those woofers. The ribbon won't stand on the floor. Those are just the pics that were taken after they were finished. They will stand on the woofer cabinet. In the pics they are already mounted on a finished baffle, but I can remove them from that baffle and put them on a new baffle (one containing the midwoofers too). As for bass- I am already getting a pair of P.Audio C15 500LF woofers. These are very low Q, but have been used, very successfully, by a local builder on an open baffle. So the midwoofers do not need to do anything below 120 - 150Hz.

 

[fporegon]

I need something that will keep up with the speed of the ribbon. I may be wrong in this. OTOH, the thing that makes the Dayton CF120 my frontrunner is its low Q.

I think "driver speed" has likely been discussed a great deal on other threads. Not wishing to start a new discussion here but I've never understood that concept. It don't see how overdamped systems are thought of as "fast".... but since you have to EQ anyway....

The ribbon is dipole as well, and all XOs and EQ will be done with a full active XO.

You might want to consider an arrangement that has the mids and ribbon side by side. Since both are dipole, this will take some thinking. I started with a Newform Research R645v3 and replaced the bottom cabinet (2 scan speaker 6.5 inch drivers) with a short array - 6 x 6.5 inch drivers - of about equal height placed right next to the ribbon driver. This was definitely an improvement. You seem concerned about integrating the mids with ribbon...doing an over / under arrangement might work against you here.

 

[Bob Richards]

A vertical array of 6 inch drivers would be more directional on the vertical axis. In that way, it would merge better with the vertical ribbon, than if it were a single driver. If the 6 inchers are baffled open-back, be careful not to build a baffle that will have significant "cavity effect" on the back side. It can be a little tricky. Many OB's out there screwed this part up. Side panels shouldn't be more than 3-4 inches deep.

I'll attach a photo of how I did my OB's, which have four 5 inch drivers on each side doing 100HZ - 1.4kHZ. My front panel is 1.5 inches thick of MDF, with successive routering on the backside so the driver air can get out easier. Solid oak is recommended for side panels, even though I used MDF. I also angled the baffle by 10 degrees to further reduce floor bounce, and align the driver diaphrams relative to the listeners ears (somewhat), so phase is less of an issue. Notice the corner braces on the back side, in the corners. They are there to help the rear energy get dispersed with minimal cavity effect on the back side. I added that rear "fin" or what I call a waveguide, to diffuse the rear emission better, so angle of placement isn't so critical.

 

[DeonC]

I think "driver speed" has likely been discussed a great deal on other threads. Not wishing to start a new discussion here but I've never understood that concept. It don't see how overdamped systems are thought of as "fast".... but since you have to EQ anyway....

True. I have been thinking about that a bit. At the moment it is between the Dayton CF120 and the Dayton reference midwoofers (4" or 5"), but I am not sure my budget will stretch to the Dayton Refs (I still have to pay postage to South-Africa, C&E, etc., etc.) I also happen to like the Dayton CF because they are carbon. I somehow think their sonic signature might match the ribbon well. OTOH, the aluminum Dayton Refs could also be an excellent match. Hard to choose. Would you pay the extra and go for the Dayton Reference midwoofers?

You might want to consider an arrangement that has the mids and ribbon side by side.

Absolutely! That has been my idea from the start. In the pics the ribbons are pre-mounted on a baffle, but the baffle is not integral to them. As soon as I get the midwoofers I will build a new baffle for the ribbons and the midwoofers. At the moment I am thinking of using 6 midwoofers, in a line-array next to the ribbon. And I will place them as close to the ribbon as I can, within constraints.

 

[DeonC]

If the 6 inchers are baffled open-back, be careful not to build a baffle that will have significant "cavity effect" on the back side. It can be a little tricky. Many OB's out there screwed this part up. Side panels shouldn't be more than 3-4 inches deep.

My side baffles will be 1" - 2" max deep. I am thinking of adding a seperation baffle between the ribbon and the midwoofers. This could be around 3" - 4" deep, but will have carpetfelt on it to reduce reflections.

I'll attach a photo of how I did my OB's, which have four 5 inch drivers on each side doing 100HZ - 1.4kHZ. My front panel is 1.5 inches thick of MDF, with successive routering on the backside so the driver air can get out easier. Solid oak is recommended for side panels, even though I used MDF. I also angled the baffle by 10 degrees to further reduce floor bounce, and align the driver diaphrams relative to the listeners ears (somewhat), so phase is less of an issue. Notice the corner braces on the back side, in the corners. They are there to help the rear energy get dispersed with minimal cavity effect on the back side. I added that rear "fin" or what I call a waveguide, to diffuse the rear emission better, so angle of placement isn't so critical.

I like your speakers. They look really cool. As far as the corner braces go, I have been thinking of putting something like 1/4-rounds in there, or maybe something similar. Maybe just triangular fill in pieces, but something to break up the corners. I also want to damp a lot of the rear panel with carpetfelt to reduce reflections as much as possible. And I really like your fin idea.

 

[fporegon]

True. I have been thinking about that a bit. At the moment it is between the Dayton CF120 and the Dayton reference midwoofers (4" or 5"), but I am not sure my budget will stretch to the Dayton Refs (I still have to pay postage to South-Africa, C&E, etc., etc.) I also happen to like the Dayton CF because they are carbon. I somehow think their sonic signature might match the ribbon well. OTOH, the aluminum Dayton Refs could also be an excellent match. Hard to choose. Would you pay the extra and go for the Dayton Reference midwoofers?

I can't give specific advice on the two drivers you've selected as I have never used either of them. If I remember correctly the band assigned to the mid-woofer is 120 Hz to 700 Hz(?) or slightly more than 2 octaves. Just about any driver I think would do fine as long as it had the excursion you need for the open baffle. Further I don't see cone material making any difference either as they will operate well below breakup. If I was forced to give guidance I would say that being spare with the cash on your midwoofer choice is fine.

Absolutely! That has been my idea from the start. In the pics the ribbons are pre-mounted on a baffle, but the baffle is not integral to them. As soon as I get the midwoofers I will build a new baffle for the ribbons and the midwoofers. At the moment I am thinking of using 6 midwoofers, in a line-array next to the ribbon. And I will place them as close to the ribbon as I can, within constraints.

I couldn't argue against this approach too much as I operated a similar system (closed baffle) for about 9 years. Only now am I making some changes.

I'd be a little concerned about the low XOVER frequency on the ribbon, but if you have electronic XO and EQ and you are using 4-5 inch drivers you can adapt....I think you will get great results.

Please keep posting with your progress.

 

[DeonC]

I'd be a little concerned about the low XOVER frequency on the ribbon, but if you have electronic XO and EQ and you are using 4-5 inch drivers you can adapt....I think you will get great results.

Which frequency would you suggest for the XO? Just keep in mind that the designer has speced these ribbons to work as low as 350Hz with a passive 3rd order XO. They are very robust. But even so, suggestions will be welcomed. The only reason I am careful of higher XO points is due to spacing between drivers. I am worried about comb-filtering in the midwoofers'range, as well as that integration between the ribbon and the midwoofers might suffer with a higher XO. Please share your thoughts and experience. It will be most appreciated.

 

[fporegon]

Ribbon XO

I don't have a particular frequency in mind, 350 Hz just seems low for a dipole ribbon transducer. I recall the larger BG ribbons claimed operation down to 150 Hz, so you may be just fine at 350. I prefer to leave the range 300 to 3k w/o a crossover breaking it up, so if you are satisfied that 350 Hz is "ok" for your ribbon then I'd say go for it.

You don't need to worry about comb filtering for this short of an array at crossover frequencies you are considering.

 

[Bob Richards]

Off axis dispersion might be the bigger issue when matching dynamic drivers with the ribbon. So smaller diameter drivers, and perhaps more of them in a vertical array, might make better sense. If you can cross the ribbons over at 500 - 800HZ, and if you will be using 4 pole xover filters (so hard cone upper-mid resonance will be very attenuated), then hard cone drivers (metal, kevlar, etc.) will give you the better resolution, and cause less of a change in off axis response at the crossover frequency. Imaging is usually better with smaller drivers too.

Don't make the mistake I made on a different project where I thought I could take a 3 inch Peerless TG9FD1008 down to 150HZ, just because the FR was flat to 100HZ. It just didn't have enough cone surface area to project the lower frequencies at real world distances in a normal living room, even with an active 4 pole xover. I wouldn't take the ribbon below 500HZ, 800 might work better.