Product Info and Selection

What do I need for a home theater system?

In the following order:

  1. A display device - TV or projector.
  2. A receiver.
  3. Speakers - connected to the receiver via speaker wires
  4. Subwoofer(s) - connected to the receiver via an RCA cable.

Watch Dr. Hsu explain it here.

What is a subwoofer?

A subwoofer is a specialized speaker that handles the most challenging task in home theater and music reproduction - producing deep, room-shaking notes that provide a better sense of the acoustic space in which a recording was made and making sound effects more realistic.

What size subwoofer do I need?

Check out our guide diagrams here.

You can never have too much subwoofer! A larger subwoofer (from the same manufacturer) will always play lower, have lower distortion, more headroom, and better long-term reliability if played at the same listening level. Therefore, if budget is not an issue and there are no WAF or physical limitations, going for the larger sub will always be beneficial.

We provide suggested room sizes for each subwoofer, but this is only a rough guide as individual tastes can vary greatly. We have customers who find that four VTF-15H MK2 subwoofers are not enough for a 1,000 cu.ft. room, while others are happy with a STF-1 (our discontinued 8-inch sub) in a 5,000 cu.ft. room. Therefore, we suggest going with the largest subwoofer that your budget, spouse, and space allow.

We frequently receive questions such as 'is this subwoofer too powerful or too loud for my room?' The answer is no. The subwoofer only needs to play as loudly as you set it. You can even turn it down until it has no contribution to the sound. You can set it anywhere between that and 'too loud'. The larger subwoofer would sound more effortless and 'airy' due to lower distortion and higher headroom. All else being equal, the larger sub will also be more reliable as it has to work less hard for the same listening level.

How do your products compare with others?

What distinguishes HSU from the rest is that we are an engineering-driven company, as reflected in the quality of our products. Other companies commonly focus on cosmetics and marketing gimmicks, following the marketing adage to "sell the sizzle, not the steak". HSU is different. We focus on pure audio engineering and on building a better mousetrap. We obsessively concentrate on product performance and reliability. Dr. Hsu carefully engineers each HSU product to provide high-end sound in its specified room type, meaning the best of the best. We hope you will agree.

Attention to customers is another differentiator. Dr. Hsu, founder of HSU, consults privately with customers on a daily basis, demonstrating his commitment to product quality and home integration. Few companies can make that claim.

What is the technology behind VTF subwoofers?

Variable tuning allows you to choose how deep your subwoofer plays, on-demand. Choose between a music mode (lower bass extension) or a home theater mode (higher headroom and more impact) in just a few seconds. Subwoofer designs involve tradeoffs – one cannot optimally design a subwoofer to play low deep notes, and at the same time play loud. Usually the designer chooses a tradeoff for you. With the VTF series, we build in flexibility so that the listener has uncompromising control.

The bass characteristics can be varied between lower extension (one port open), higher headroom (2 ports open), or sealed mode. We also give you a Q control to adjust the bass tightness. This series gives you more flexibility than any other subwoofer we know. This is equivalent of buying multiple subwoofers for the price of one. Irrespective of your preference or room, you can get the VTF subwoofer to sound right.

Watch Dr. Hsu explain it here.

What recommendations do you have for receivers?

Most receivers these days should work well. Because we like to think about budget, Onkyo and Pioneer receivers are budget-friendly, yet work very well.

Do I need to use a subwoofer interconnect?

No. A regular mono RCA cable is all you need.

What type of speaker wall mount would you recommend to use with the HB-1 MK2 and HC-1 MK2?

Our customers have used B-Tech BT15 or PPT_AM15B (, Center Channel Speaker Bracket Mount and B-Tech BT77 UltraGrip Pro Speaker Wall Mounts.

This AM40 side clamping wall mount frombracketsandstandsworks without requiring any threaded inserts on the HB-1 MK2s
(Note: These products are not endorsed or affiliated with Hsu Research)

What happened to the mid-bass module?

We have incorporated the MBM concept in the ULS-15 MK2. Expanding on the variable tuning concept, we made the ULS-15 MK2 operate in two modes - a sealed ultra deep bass subwoofer and as a MBM (mid bass module). Two products in one! In the MBM mode, the ULS-15 MK2 has even higher mid bass headroom than the MBM-12 MK2 and can be transformed into a sub 20 Hz subwoofer at the flip of a switch!a

Test Tones for Subwoofer Measurements

You can download the test tones on the CDR we provide (if you lost your CD, or if you are outside of the US) here.

Setup and Usage

Where is the best place to put a subwoofer?

A good place to start is a front corner furthest from openings. This is generally great for deep bass. If you like a lot of 'hit in the chest' mid-bass punch, placing the subwoofer close to you is best (preferably directly behind).

If you have a means of measuring and are willing to experiment, the subwoofer crawl is the best way to find the optimal location for the subwoofer. You place the subwoofer in your listening chair and measure the frequency response at the various locations where you can place the subwoofer. The position that gives the best response is where you should put the subwoofer.

Note that where you sit is equally important. If possible, avoid sitting in the middle of the room as this is where bass is usually weakest.

What is the best way to set up the HB-1 MK2s?

The HB-1 MK2s are best toed in so that the tweeter axis crosses a foot or two in front of you. This positioning provides the deepest soundstage and the widest sweet spot. If you use the recommended stands (26-28" high stands), the speakers should be positioned 19" away from the side walls (measured to the center of the woofer dust cap). If this is not practical, don't worry - they will still sound great.

How close can I put the subwoofer to my television?

Unless you are still using a CRT television, you don't have to worry about placing the subwoofer close to your TV. None of the newer technology TVs are sensitive to magnetic fields.

What should I use to clean the cabinet?

You should use a damp soft cloth (micro fiber is great), followed by a dry one. Never use any chemicals.

How do you change voltage settings?

With the current VTF and ULS series subwoofers, there is a voltage selector switch on the back of the amplifier. Remember to change the fuse when you change the voltage. Use half the current rating when switching to 230/240V. 

What crossover frequency should I use? I have large main speakers

We generally recommend using 80 Hz crossover even if you have large main speakers. Due to the limited amplifier power of most receivers, using the main speakers to handle some of the bass will reduce the amplifier power available for the mids and highs. Crossing over at 80 Hz gives you the highest possible headroom for your system.

We do not recommend crossing over higher because the subwoofer will be localizable with a higher crossover.

If I have two or more subwoofers, how should I set them up?

To achieve the highest headroom, it's important to level match all the subwoofers in your system. Follow these steps:

  1. Mark a spot on the floor and position each subwoofer precisely in that spot. Make sure all controls are set similarly - crossover out, EQ1 (if available), Q=0.7 (if there's a Q control), etc.
  2. Place an SPL meter 1 m in front of the subwoofers and set it to the 80 dB range with C weighting.
  3. With just one subwoofer and the receiver's sub out at 0 dB, adjust the level on the subwoofer to get a nice balance. Set all subwoofers to about this level.
  4. Place the first subwoofer in the marked spot, set its volume to where it sounded good in your system, and play a 50 Hz tone. Adjust the volume on your receiver to get an 80 dB reading.
  5. If you have two subwoofers to match, lower the volume on the second subwoofer to get 75 dB. For four subwoofers, adjust the volume on the subwoofer to get 70 dB.
  6. Move the first sub out and place the second sub in the same location. Play the same test tone and adjust the sub's volume control to get the same dB reading. Repeat this for the rest of the subwoofers.
  7. Now all the subwoofers are level matched. Don't touch their volume controls again or they won't be level matched anymore.

Should I use the Auto EQ in my receiver?

The auto EQ feature in receivers is generally improving and it's recommended to use it. As a general guideline for using auto EQ with a subwoofer, set the subwoofer to the lowest extension and flattest response mode so that the EQ compensates for the room acoustics only. For example, with our VTF series subwoofer, set it to one port open, EQ1, and Q=0.7 for the flattest response mode. The EQ will then adjust for the room effects. After EQ, you can choose other operating modes for the subwoofer such as two ports open, EQ2, Q=0.3, and so on.

Can I connect your subwoofers to my computer or computer speakers?

It's relatively easy to connect a HSU subwoofer to computer sound cards with a dedicated subwoofer output. Without a subwoofer output on the card, it is still possible to hook up a VTF or ULS subwoofer, since these subwoofers have stereo inputs.

Use a splitter/adapter (one 1/8-inch stereo male to two 1/8-inch stereo female). Take the stereo 1/8-inch output from the computer sound card. Then feed one set to the computer speakers and another to the subwoofer using an adapter (1/8-inch stereo male to two RCA male). Please be aware that connecting a HSU Research subwoofer o computer speakers (as opposed to computer sound cards) may be impossible.

How do you hook up the subwoofer to a pre-amp?

If your computer has a dedicated subwoofer output, simply connect that to the subwoofer. If it does not have a subwoofer output on the card, simply split the L/R outputs to feed both the subwoofer and the powered speakers you have your computer connected to.

About Us

How do you pronounce "Hsu"?

We're originally from Singapore, so we pronounce it: "SOO".

Listen to this video.

Do you do demonstrations or auditions?

Yes! We are located in Orange County, California. Please call or message ahead for an appointment during our normal business hours.

What happened to your old site/forum?

We sunsetted them in 2023. Here's a snapshot if you're feeling nostalgic.

Thanks to all of our loyal supporters who advocated for our products despite the basic website!

Customer Service - Ordering, Shipping, and Returns

Where do you ship to?

We ship to every state in the continuous US (not including Alaska and Hawaii).

Interested buyers from elsewhere should contact us directly. We may be able to accommodate a purchase, but the buyer will likely be responsible for the freight.

Do you have a local pickup option?

Yes, you can pick up from our office at: N. Shepard Street, Anaheim, CA 92806. Just contact us in advance to order and schedule.

Note: we do not accept PayPal for pick-up orders.

Terms & Conditions - Orders

Orders may usually be placed using the Hsu Research website or over the phone with an official Hsu Research representative. We accept credit cards issued by Visa, MasterCard, American Express, and Discover. Gift cards are generally not accepted unless the customer is able to add in their billing address to the card and the card can be properly authenticated. All cards must be issued by a US bank. It is preferred that the order billing address and shipping address be the same, especially for first time customers. However, if the shipping address is different from the billing address, the customer may be subject to further authentication. Hsu Research does accept PayPal for payment. However, when PayPal is used, the order must ship to a PayPal confirmed address. PayPal is not accepted for local pickup. Money orders and checks, issued within the US, are accepted. However, money orders, and checks, will be subjected to longer processing times. Please contact Hsu Research to place your order if using a money order or check.

Orders placed outside of the contiguous United States must be placed over the phone or via email. Due to our inability to authenticate, we cannot accept credit cards for orders placed outside of US and Canada. We may be able to accept PayPal, provided the shipping address is confirmed by PayPal. For orders placed outside the US and Canada, direct wire transfer is typically used for payment. All orders shipped outside the contiguous US will need a quote for shipping. Please contact us at so that we may provide you with an official shipping quote. When shipping outside the United States, the customer will be responsible for any customs fees such as taxes and duties.

If in stock, orders normally ship within one business day after the order is placed. It is usual, that the order may ship the same business day if placed before 12:00 PM (PST/PDT). It’s still possible that the order may ship if placed after 12 PM, so if any changes need to be made to your order, Hsu Research will need to be notified by 01:30 PM (PST/PDT) the same day the order ships. If you need to make a change to your order, you will need to contact us via email at and/or via phone (714-666-9260).

We do accept local pickups at our Anaheim, CA location and that may be specified under the shipping method when placing the order online. We ask that the customer provide us with the date and time, within normal business hours, for pickup in the comment section. We will send an email to the customer to confirm the pickup time. Generally, we do not allow for anyone other than the billing cardholder to pick up the order.

All prices listed on the Hsu Research website are in United States Dollar. Prices posted on the Hsu website are subject to change without notice.

Sales tax is currently only collected when receiving within California. Note that the product pages do not reflect the sales tax. Any applicable sales tax is displayed during the ordering process after you enter in your shipping and billing information.

Terms & Conditions - Shipping

Products are normally shipped with low cost, insured, FedEx Ground with signature required to any destination in the lower 48 states. Due to the cost of the item, we do prefer to send with signature required. However, if the customer would rather send the item with no signature required, the customer can request that in the comment section.  

Note that for no signature required:
1) Once the package is delivered, Hsu Research no longer assumes responsibility for the package.
2)  Due to the value of the package, it is ultimately up to the FedEx driver's discretion whether to require a signature or not.

We cannot modify the signature requirement after shipping. If you want to have the signature requirement removed, you would need to inform us, in the comment section, when you place the order.

Depending on the location, many items shipped can be held at a nearby FedEx Print & Ship Center. Please contact or check the FedEx website to find the nearest location to you.

Shipping times within the 48 states are typically 1-5 business days depending on the location. Note that shipping and delivery times are estimates only and are not guaranteed. Hsu Research is not responsible if the shipment is delayed. The day your order is shipped, your FedEx tracking number will be emailed. For online orders, we also update your tracking page with the tracking information. If you do not receive it, be sure to check your spam folder, as some emails tend to end up there. If you are unable to locate the tracking number, give us a call or send us an email at and we will be happy to provide you with the tracking info.

For orders shipped outside of the contiguous United States, there will be an additional shipping and handling charge. Email for a shipping quote.

It is strongly recommended that you inspect the item as soon as it is delivered. If the item has arrived damaged, Hsu Research must be notified within 21 days of receiving the item.

Terms & Conditions - Warranty

The standard warranty on all subwoofers is 7 years on the driver(s) and 2 years on the electronics. Speakers come with a warranty of 7 years on the drivers. For RMA repairs, whether or not under warranty, the customer is responsible for organizing shipment of the part to Hsu Research. If under warranty, Hsu Research will be responsible for the repair and return shipping cost back to the customer within the 48 states. For international orders, the customer will be responsible for shipping costs both ways as well as any additional customs fees. For more details on warranty coverage, please reference the individual product manual, located on the individual product page.

We only offer an extended electronics warranty for our powered subwoofers.  To add the extended electronics warranty, add the product to the cart. When you view the cart, an option will display on the bottom allowing you to add the electronics warranty to your order. The extended electronics warranty extends the warranty from two years to five years.

30-day Satisfaction Guarantee

If you are not completely satisfied with your purchase, you have 30 days from receiving the item to begin the return process. The customer is responsible for organizing return shipping and ensuring the safe transit of the product(s). We will refund the complete purchase price, minus any shipping charges, after our technicians review the return. The refund happens under four conditions: (1) all items must be in "like new" condition, (2) there must not be any missing items, (3) the product needs to be in transit back to Hsu Research within 30 of delivery (4) you must call us to receive an RMA number. Failure to comply with these conditions may result in the item being refused, or you may be charged a 15% restocking fee. In the event that the item(s) returned arrives damaged, the customer is responsible for filing any claims with their courier. Package Orders: In the event that you receive the unit(s) damaged, a replacement unit(s) will be shipped out at no cost to you. However, if you decide to return the entire package, you will be responsible for all shipping and handling charges both ways for all returned items and the same terms as stated above will apply.

If the shipment is rejected, or if the item is sent back to Hsu Research due to failed delivery, by no fault of Hsu Research, the customer will be responsible for shipping both ways.

Hsu Research reserves the right to modify the 30-day tryout policy without notice.

Contacting us


Why is there is a humming or buzzing noise coming from my subwoofer?

This is a common question and can usually be solved at home. There are several possible causes:

1) You have a ground loop problem. Try using a cheater plug that removes the third prong, also called the 'ground'. Do NOT ground the grounding tab on the cheater plug! That would defeat the purpose of the cheater plug for this application.

2) You have an amplifier problem. If the ground cheater plug does not help, disconnect all interconnects from the subwoofer amplifier. If still hums, call or email technical support.

3) You have a problem with other equipment. If the hum goes away when interconnects are disconnected, the hum is coming from the rest of your equipment. Add them back one piece at a time to determine the source of the hum.